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Bendle JM, Palmer AP, Thorndycraft VR, Matthews IP. Phased Patagonian Ice Sheet response to Southern Hemisphere atmospheric and oceanic warming between 18 and 17 ka. Sci Rep 2019; 9:4133. [PMID: 30858415 PMCID: PMC6411896 DOI: 10.1038/s41598-019-39750-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 01/28/2019] [Indexed: 11/16/2022] Open
Abstract
The onset of deglaciation in the Southern Hemisphere mid-latitudes has been attributed to the southward transmission of climate anomalies in response to slow-down of Atlantic meridional overturning circulation (AMOC) during Heinrich Stadial 1 (HS-1; 18–14.6 ka). However, inferences on the response of former ice sheets to sub-millennial palaeoclimate shifts are limited by a shortage of high-resolution terrestrial archives. Here we use a ~1000-year duration, annually-resolved lake sediment record to investigate the deglacial retreat dynamics of the Lago General Carrera–Buenos Aires ice lobe (46.5°S) of the former Patagonian Ice Sheet. We attribute the onset of glacier retreat at 18.0 ± 0.14 cal ka BP to abrupt southward migration of the Southern Westerly Winds that enhanced solar radiation receipt (and ablation) at the ice sheet surface. We infer that accelerated retreat from 17.77 ± 0.13 cal ka BP represents a lagged Southern Hemisphere response to gradual ocean-atmosphere warming associated with the centennial-scale transmission of Northern Hemisphere climate anomalies through the oceanic bipolar seesaw. By 17.38 ± 0.12 cal ka BP, the glacier margin had receded into a deepening proglacial lake, instigating sustained calving losses and more rapid ice recession.
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Affiliation(s)
- Jacob M Bendle
- Centre for Quaternary Research, Geography Department, Royal Holloway, University of London, Egham, TW20 0EX, Surrey, UK.
| | - Adrian P Palmer
- Centre for Quaternary Research, Geography Department, Royal Holloway, University of London, Egham, TW20 0EX, Surrey, UK
| | - Varyl R Thorndycraft
- Centre for Quaternary Research, Geography Department, Royal Holloway, University of London, Egham, TW20 0EX, Surrey, UK
| | - Ian P Matthews
- Centre for Quaternary Research, Geography Department, Royal Holloway, University of London, Egham, TW20 0EX, Surrey, UK
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102
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Sadatzki H, Dokken TM, Berben SMP, Muschitiello F, Stein R, Fahl K, Menviel L, Timmermann A, Jansen E. Sea ice variability in the southern Norwegian Sea during glacial Dansgaard-Oeschger climate cycles. SCIENCE ADVANCES 2019; 5:eaau6174. [PMID: 30854427 PMCID: PMC6402855 DOI: 10.1126/sciadv.aau6174] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 01/23/2019] [Indexed: 06/09/2023]
Abstract
The last glacial period was marked by pronounced millennial-scale variability in ocean circulation and global climate. Shifts in sea ice cover within the Nordic Seas are believed to have amplified the glacial climate variability in northern high latitudes and contributed to abrupt, high-amplitude temperature changes over Greenland. We present unprecedented empirical evidence that resolves the nature, timing, and role of sea ice fluctuations for abrupt ocean and climate change 32 to 40 thousand years ago, using biomarker sea ice reconstructions from the southern Norwegian Sea. Our results document that initial sea ice reductions at the core site preceded the major reinvigoration of convective deep-water formation in the Nordic Seas and abrupt Greenland warming; sea ice expansions preceded the buildup of a deep oceanic heat reservoir. Our findings suggest that the sea ice variability shaped regime shifts between surface stratification and deep convection in the Nordic Seas during abrupt climate changes.
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Affiliation(s)
- Henrik Sadatzki
- Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, 5007 Bergen, Norway
| | - Trond M. Dokken
- NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, 5007 Bergen, Norway
| | - Sarah M. P. Berben
- Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, 5007 Bergen, Norway
| | - Francesco Muschitiello
- Department of Geography, University of Cambridge, Cambridge CB2 3EQ, UK
- Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, P.O. Box 1000, Palisades, NY 10964, USA
| | - Ruediger Stein
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27568 Bremerhaven, Germany
- MARUM and Faculty of Geosciences (FB 5), University of Bremen, P.O. Box 330440, 28334 Bremen, Germany
| | - Kirsten Fahl
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27568 Bremerhaven, Germany
| | - Laurie Menviel
- Climate Change Research Centre and PANGEA Research Centre, University of New South Wales, Sydney, New South Wales 2052, Australia
- Department of Earth and Planetary Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Axel Timmermann
- Center for Climate Physics, Institute for Basic Science (IBS), Busan, South Korea
- Pusan National University, Busan, South Korea
| | - Eystein Jansen
- Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, 5007 Bergen, Norway
- NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, 5007 Bergen, Norway
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103
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Shchipanov NA, Pavlova SV. Role of Population Structuring in the Formation of Karyotypic Diversity of the Common Shrew Sorex araneus (Lipotyphla, Mammalia). RUSS J ECOL+ 2019. [DOI: 10.1134/s1067413619020097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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104
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Impact of abrupt sea ice loss on Greenland water isotopes during the last glacial period. Proc Natl Acad Sci U S A 2019; 116:4099-4104. [PMID: 30760586 PMCID: PMC6410777 DOI: 10.1073/pnas.1807261116] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Dansgaard–Oeschger events contained in Greenland ice cores constitute the archetypal record of abrupt climate change. An accurate understanding of these events hinges on interpretation of Greenland records of oxygen and nitrogen isotopes. We present here the important results from a suite of modeled Dansgaard–Oeschger events. These simulations show that the change in oxygen isotope per degree of warming becomes smaller during larger events. Abrupt reductions in sea ice also emerge as a strong control on ice core oxygen isotopes because of the influence on both the moisture source and the regional temperature increase. This work confirms the significance of sea ice for past abrupt warming events. Greenland ice cores provide excellent evidence of past abrupt climate changes. However, there is no universally accepted theory of how and why these Dansgaard–Oeschger (DO) events occur. Several mechanisms have been proposed to explain DO events, including sea ice, ice shelf buildup, ice sheets, atmospheric circulation, and meltwater changes. DO event temperature reconstructions depend on the stable water isotope (δ18O) and nitrogen isotope measurements from Greenland ice cores: interpretation of these measurements holds the key to understanding the nature of DO events. Here, we demonstrate the primary importance of sea ice as a control on Greenland ice core δ18O: 95% of the variability in δ18O in southern Greenland is explained by DO event sea ice changes. Our suite of DO events, simulated using a general circulation model, accurately captures the amplitude of δ18O enrichment during the abrupt DO event onsets. Simulated geographical variability is broadly consistent with available ice core evidence. We find an hitherto unknown sensitivity of the δ18O paleothermometer to the magnitude of DO event temperature increase: the change in δ18O per Kelvin temperature increase reduces with DO event amplitude. We show that this effect is controlled by precipitation seasonality.
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105
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Late Quaternary Variations in the South American Monsoon System as Inferred by Speleothems—New Perspectives using the SISAL Database. QUATERNARY 2019. [DOI: 10.3390/quat2010006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Here we present an overview of speleothem δ18O records from South America, most of which are available in the Speleothem Isotopes Synthesis and Analysis (SISAL_v1) database. South American tropical and subtropical speleothem δ18O time series are primarily interpreted to reflect changes in precipitation amount, the amount effect, and consequently history of convection intensity variability of convergence zones such as the Intertropical Convergence Zone (ITCZ) and the South America Monsoon System (SAMS). We investigate past hydroclimate scenarios in South America related to the South American Monsoon System in three different time periods: Late Pleistocene, Holocene, and the last two millennia. Precession driven summertime insolation is the main driver of convective variability over the continent during the last 120 kyrs (from present day to 120 kyrs BP), including the Holocene. However, there is a dipole between speleothem δ18O records from western and eastern South America. Records located in the central region of Brazil are weakly affected by insolation-driven variability, and instead are more susceptible to the variability associated with the South Atlantic Convergence Zone (SACZ). Cold episodic events in the Northern Hemisphere, such as Heinrich and Bond Events, and the Little Ice Age, increase the convective activity of the SAMS, resulting in increased precipitation amount in South America.
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106
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Pendleton SL, Miller GH, Lifton N, Lehman SJ, Southon J, Crump SE, Anderson RS. Rapidly receding Arctic Canada glaciers revealing landscapes continuously ice-covered for more than 40,000 years. Nat Commun 2019; 10:445. [PMID: 30683866 PMCID: PMC6347664 DOI: 10.1038/s41467-019-08307-w] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 12/21/2018] [Indexed: 12/03/2022] Open
Abstract
Arctic temperatures are increasing faster than the Northern Hemisphere average due to strong positive feedbacks unique to polar regions. However, the degree to which recent Arctic warming is unprecedented remains debated. Ages of entombed plants in growth position preserved by now receding ice caps in Arctic Canada help to address this issue by placing recent conditions in a multi-millennial context. Here we show that pre-Holocene radiocarbon dates on plants collected at the margins of 30 ice caps in Arctic Canada suggest those locations were continuously ice covered for > 40 kyr, but are now ice-free. We use in situ 14C inventories in rocks from nine locations to explore the possibility of brief exposure during the warm early Holocene. Modeling the evolution of in situ 14C confirms that Holocene exposure is unlikely at all but one of the sites. Viewed in the context of temperature records from Greenland ice cores, our results suggest that summer warmth of the past century exceeds now any century in ~115,000 years. Shrinking Arctic Canada ice caps are revealing preserved landscapes containing a record of past glacier activity. Here the authors show that 14C ages of plants and cosmogenic 14C concentrations from these landscapes indicate that recently exposed landscapes have been continuously ice covered for > 40,000 years.
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Affiliation(s)
- Simon L Pendleton
- INSTAAR and Department of Geological Sciences, University of Colorado, Boulder, CO, 80309-0450, USA.
| | - Gifford H Miller
- INSTAAR and Department of Geological Sciences, University of Colorado, Boulder, CO, 80309-0450, USA
| | - Nathaniel Lifton
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, 47907, USA.,Department of Physics and Astronomy, PRIME Lab, Purdue University, West Lafayette, IN, 47907, USA
| | - Scott J Lehman
- INSTAAR and Department of Geological Sciences, University of Colorado, Boulder, CO, 80309-0450, USA
| | - John Southon
- Department of Earth System Science, University of California, Irvine, Croul Hall, Irvine, CA, 92697-3100, USA
| | - Sarah E Crump
- INSTAAR and Department of Geological Sciences, University of Colorado, Boulder, CO, 80309-0450, USA
| | - Robert S Anderson
- INSTAAR and Department of Geological Sciences, University of Colorado, Boulder, CO, 80309-0450, USA
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107
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A Window into Africa’s Past Hydroclimates: The SISAL_v1 Database Contribution. QUATERNARY 2019. [DOI: 10.3390/quat2010004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Africa spans the hemispheres from temperate region to temperate region and has a long history of hominin evolution. Although the number of Quaternary palaeoclimatic records from the continent is increasing, much of the history of spatial and temporal climatic variability is still debated. Speleothems, as archives of terrestrial hydroclimate variability, can help reveal this history. Here we review the progress made to date, with a focus on the first version of the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database. The geology of Africa has limited development of large karst regions to four areas: along the northern coast bordering the Mediterranean, eastern Africa and the Horn of Africa, southwestern Africa and southern Africa. Exploitation of the speleothem palaeoclimate archives in these regions is uneven, with long histories of research, e.g., in South Africa, but large areas with no investigations such as West Africa. Consequently, the evidence of past climate change reviewed here is irregularly sampled in both time and space. Nevertheless, we show evidence of migration of the monsoon belt, with enhanced rainfall during interglacials observed in northeast Africa, southern Arabia and the northern part of southern Africa. Evidence from eastern Africa indicates significant decadal and centennial scale rainfall variability. In northwestern and southern Africa, precession and eccentricity influence speleothem growth, largely through changing synoptic storm activity.
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108
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Diverse manifestations of the mid-Pleistocene climate transition. Nat Commun 2019; 10:352. [PMID: 30664647 PMCID: PMC6341081 DOI: 10.1038/s41467-018-08257-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 12/20/2018] [Indexed: 12/03/2022] Open
Abstract
The mid-Pleistocene transition (MPT) is widely recognized as a shift in paleoclimatic periodicity from 41- to 100-kyr cycles, which largely reflects integrated changes in global ice volume, sea level, and ocean temperature from the marine realm. However, much less is known about monsoon-induced terrestrial vegetation change across the MPT. Here, on the basis of a 1.7-million-year δ13C record of loess carbonates from the Chinese Loess Plateau, we document a unique MPT reflecting terrestrial vegetation changes from a dominant 23-kyr periodicity before 1.2 Ma to combined 100, 41, and 23-kyr cycles after 0.7 Ma, very different from the conventional MPT characteristics. Model simulations further reveal that the MPT transition likely reflects decreased sensitivity of monsoonal hydroclimate to insolation forcing as the Northern Hemisphere became increasingly glaciated through the MPT. Our proxy-model comparison suggests varied responses of temperature and precipitation to astronomical forcing under different ice/CO2 boundary conditions, which greatly improves our understanding of monsoon variability and dynamics from the natural past to the anthropogenic future. The mid-Pleistocene transition is recognized as a shift in paleoclimatic periodicity from 41- to 100-kyr cycles. Here the authors present a unique mid-Pleistocene transition of coupled monsoon-vegetation changes from 23- to 100-kyr cycles, which indicates varied sensitivity of past climate to astronomical and ice/CO2 forcing.
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109
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Martens J, Wild B, Pearce C, Tesi T, Andersson A, Bröder L, O'Regan M, Jakobsson M, Sköld M, Gemery L, Cronin TM, Semiletov I, Dudarev OV, Gustafsson Ö. Remobilization of Old Permafrost Carbon to Chukchi Sea Sediments During the End of the Last Deglaciation. GLOBAL BIOGEOCHEMICAL CYCLES 2019; 33:2-14. [PMID: 31007381 PMCID: PMC6472570 DOI: 10.1029/2018gb005969] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 11/27/2018] [Accepted: 12/11/2018] [Indexed: 05/26/2023]
Abstract
Climate warming is expected to destabilize permafrost carbon (PF-C) by thaw-erosion and deepening of the seasonally thawed active layer and thereby promote PF-C mineralization to CO2 and CH4. A similar PF-C remobilization might have contributed to the increase in atmospheric CO2 during deglacial warming after the last glacial maximum. Using carbon isotopes and terrestrial biomarkers (Δ14C, δ13C, and lignin phenols), this study quantifies deposition of terrestrial carbon originating from permafrost in sediments from the Chukchi Sea (core SWERUS-L2-4-PC1). The sediment core reconstructs remobilization of permafrost carbon during the late Allerød warm period starting at 13,000 cal years before present (BP), the Younger Dryas, and the early Holocene warming until 11,000 cal years BP and compares this period with the late Holocene, from 3,650 years BP until present. Dual-carbon-isotope-based source apportionment demonstrates that Ice Complex Deposit-ice- and carbon-rich permafrost from the late Pleistocene (also referred to as Yedoma)-was the dominant source of organic carbon (66 ± 8%; mean ± standard deviation) to sediments during the end of the deglaciation, with fluxes more than twice as high (8.0 ± 4.6 g·m-2·year-1) as in the late Holocene (3.1 ± 1.0 g·m-2·year-1). These results are consistent with late deglacial PF-C remobilization observed in a Laptev Sea record, yet in contrast with PF-C sources, which at that location were dominated by active layer material from the Lena River watershed. Release of dormant PF-C from erosion of coastal permafrost during the end of the last deglaciation indicates vulnerability of Ice Complex Deposit in response to future warming and sea level changes.
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Affiliation(s)
- Jannik Martens
- Department of Environmental Science and Analytical Chemistry (ACES)Stockholm UniversityStockholmSweden
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
| | - Birgit Wild
- Department of Environmental Science and Analytical Chemistry (ACES)Stockholm UniversityStockholmSweden
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
| | - Christof Pearce
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
- Department of Geological Sciences (IGV)Stockholm UniversityStockholmSweden
- Department of Geoscience, Arctic Research Centre and ClimateAarhus UniversityAarhusDenmark
| | - Tommaso Tesi
- Department of Environmental Science and Analytical Chemistry (ACES)Stockholm UniversityStockholmSweden
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
- Institute of Marine SciencesNational Research CouncilBolognaItaly
| | - August Andersson
- Department of Environmental Science and Analytical Chemistry (ACES)Stockholm UniversityStockholmSweden
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
| | - Lisa Bröder
- Department of Environmental Science and Analytical Chemistry (ACES)Stockholm UniversityStockholmSweden
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
- Department of Earth SciencesVrije Universiteit AmsterdamAmsterdamNetherlands
| | - Matt O'Regan
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
- Department of Geological Sciences (IGV)Stockholm UniversityStockholmSweden
| | - Martin Jakobsson
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
- Department of Geological Sciences (IGV)Stockholm UniversityStockholmSweden
| | - Martin Sköld
- Department of MathematicsStockholm UniversityStockholmSweden
| | | | | | - Igor Semiletov
- Pacific Oceanological Institute FEB RASVladivostokRussia
- Institute of Natural ResourcesTomsk Polytechnic UniversityTomskRussia
- International Arctic Research CenterUniversity of Alaska FairbanksFairbanksAKUSA
| | - Oleg V. Dudarev
- Pacific Oceanological Institute FEB RASVladivostokRussia
- Institute of Natural ResourcesTomsk Polytechnic UniversityTomskRussia
| | - Örjan Gustafsson
- Department of Environmental Science and Analytical Chemistry (ACES)Stockholm UniversityStockholmSweden
- Bolin Centre for Climate ResearchStockholm UniversityStockholmSweden
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110
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111
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Population reconstructions for humans and megafauna suggest mixed causes for North American Pleistocene extinctions. Nat Commun 2018; 9:5441. [PMID: 30575758 PMCID: PMC6303330 DOI: 10.1038/s41467-018-07897-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 12/05/2018] [Indexed: 11/30/2022] Open
Abstract
Dozens of large mammals such as mammoth and mastodon disappeared in North America at the end of the Pleistocene with climate change and “overkill” by human hunters the most widely-argued causes. However, the population dynamics of humans and megafauna preceding extinctions have received little attention even though such information may be telling as we expect increasing human populations to be correlated with megafaunal declines if hunting caused extinctions. No such trends are expected if climate change was the primary cause. We present tests of these hypotheses here by using summed calibrated radiocarbon date distributions to reconstruct population levels of megafauna and humans. The results suggest that the causes for extinctions varied across taxa and by region. In three cases, extinctions appear linked to hunting, while in five others they are consistent with the ecological effects of climate change and in a final case, both hunting and climate change appear responsible. Much of the North American megafauna went extinct in the late Pleistocene, but the causes are debated. Here the authors analyze human and megafaunal population dynamics in Pleistocene North America and find variation among taxa and region in whether hunting, climate or both best predict extinction.
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112
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Abstract
As the world warms due to rising greenhouse gas concentrations, the Earth system moves toward climate states without societal precedent, challenging adaptation. Past Earth system states offer possible model systems for the warming world of the coming decades. These include the climate states of the Early Eocene (ca. 50 Ma), the Mid-Pliocene (3.3-3.0 Ma), the Last Interglacial (129-116 ka), the Mid-Holocene (6 ka), preindustrial (ca. 1850 CE), and the 20th century. Here, we quantitatively assess the similarity of future projected climate states to these six geohistorical benchmarks using simulations from the Hadley Centre Coupled Model Version 3 (HadCM3), the Goddard Institute for Space Studies Model E2-R (GISS), and the Community Climate System Model, Versions 3 and 4 (CCSM) Earth system models. Under the Representative Concentration Pathway 8.5 (RCP8.5) emission scenario, by 2030 CE, future climates most closely resemble Mid-Pliocene climates, and by 2150 CE, they most closely resemble Eocene climates. Under RCP4.5, climate stabilizes at Pliocene-like conditions by 2040 CE. Pliocene-like and Eocene-like climates emerge first in continental interiors and then expand outward. Geologically novel climates are uncommon in RCP4.5 (<1%) but reach 8.7% of the globe under RCP8.5, characterized by high temperatures and precipitation. Hence, RCP4.5 is roughly equivalent to stabilizing at Pliocene-like climates, while unmitigated emission trajectories, such as RCP8.5, are similar to reversing millions of years of long-term cooling on the scale of a few human generations. Both the emergence of geologically novel climates and the rapid reversion to Eocene-like climates may be outside the range of evolutionary adaptive capacity.
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113
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Ocean circulation, ice shelf, and sea ice interactions explain Dansgaard-Oeschger cycles. Proc Natl Acad Sci U S A 2018; 115:E11005-E11014. [PMID: 30385629 DOI: 10.1073/pnas.1802573115] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The last glacial interval experienced abrupt climatic changes called Dansgaard-Oeschger (DO) events. These events manifest themselves as rapid increases followed by slow decreases of oxygen isotope ratios in Greenland ice core records. Despite promising advances, a comprehensive theory of the DO cycles, with their repeated ups and downs of isotope ratios, is still lacking. Here, based on earlier hypotheses, we introduce a dynamical model that explains the DO variability by rapid retreat and slow regrowth of thick ice shelves and thin sea ice in conjunction with changing subsurface water temperatures due to insulation by the ice cover. Our model successfully reproduces observed features of the records, such as the sawtooth shape of the DO cycles, waiting times between DO events across the last glacial, and the shifted antiphase relationship between Greenland and Antarctic ice cores. Our results show that these features can be obtained via internal feedbacks alone. Warming subsurface waters could have also contributed to the triggering of Heinrich events. Our model thus offers a unified framework for explaining major features of multimillennial climate variability during glacial intervals.
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114
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Batz P, Ruttor A, Opper M. Approximate Bayes learning of stochastic differential equations. Phys Rev E 2018; 98:022109. [PMID: 30253603 DOI: 10.1103/physreve.98.022109] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Indexed: 11/07/2022]
Abstract
We introduce a nonparametric approach for estimating drift and diffusion functions in systems of stochastic differential equations from observations of the state vector. Gaussian processes are used as flexible models for these functions, and estimates are calculated directly from dense data sets using Gaussian process regression. We develop an approximate expectation maximization algorithm to deal with the unobserved, latent dynamics between sparse observations. The posterior over states is approximated by a piecewise linearized process of the Ornstein-Uhlenbeck type and the maximum a posteriori estimation of the drift is facilitated by a sparse Gaussian process approximation.
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Affiliation(s)
- Philipp Batz
- TU Berlin, Fakultät IV-MAR 4-2, Marchstrasse 23, 10587 Berlin, Germany
| | - Andreas Ruttor
- TU Berlin, Fakultät IV-MAR 4-2, Marchstrasse 23, 10587 Berlin, Germany
| | - Manfred Opper
- TU Berlin, Fakultät IV-MAR 4-2, Marchstrasse 23, 10587 Berlin, Germany
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115
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Hawkings JR, Hatton JE, Hendry KR, de Souza GF, Wadham JL, Ivanovic R, Kohler TJ, Stibal M, Beaton A, Lamarche-Gagnon G, Tedstone A, Hain MP, Bagshaw E, Pike J, Tranter M. The silicon cycle impacted by past ice sheets. Nat Commun 2018; 9:3210. [PMID: 30097566 PMCID: PMC6086862 DOI: 10.1038/s41467-018-05689-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 06/11/2018] [Indexed: 11/17/2022] Open
Abstract
Globally averaged riverine silicon (Si) concentrations and isotope composition (δ30Si) may be affected by the expansion and retreat of large ice sheets during glacial−interglacial cycles. Here we provide evidence of this based on the δ30Si composition of meltwater runoff from a Greenland Ice Sheet catchment. Glacier runoff has the lightest δ30Si measured in running waters (−0.25 ± 0.12‰), significantly lower than nonglacial rivers (1.25 ± 0.68‰), such that the overall decline in glacial runoff since the Last Glacial Maximum (LGM) may explain 0.06–0.17‰ of the observed ocean δ30Si rise (0.5–1.0‰). A marine sediment core proximal to Iceland provides further evidence for transient, low-δ30Si meltwater pulses during glacial termination. Diatom Si uptake during the LGM was likely similar to present day due to an expanded Si inventory, which raises the possibility of a feedback between ice sheet expansion, enhanced Si export to the ocean and reduced CO2 concentration in the atmosphere, because of the importance of diatoms in the biological carbon pump. The role ice sheets play in the silica cycle over glacial−interglacial timescales remains unclear. Here, based on the measurement of silica isotopes in Greenland meltwater and a nearby marine sediment core, the authors suggest expanding ice sheets considerably increased isotopically light silica in the oceans.
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Affiliation(s)
- Jon R Hawkings
- Bristol Glaciology Centre, School of Geographical Sciences, University Road, Bristol, BS8 1SS, UK.
| | - Jade E Hatton
- Bristol Glaciology Centre, School of Geographical Sciences, University Road, Bristol, BS8 1SS, UK
| | | | - Gregory F de Souza
- Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, 8092, Zürich, Switzerland
| | - Jemma L Wadham
- Bristol Glaciology Centre, School of Geographical Sciences, University Road, Bristol, BS8 1SS, UK
| | - Ruza Ivanovic
- School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
| | - Tyler J Kohler
- Department of Ecology, Charles University, Viničná 7, 12844, Prague 2, Czech Republic
| | - Marek Stibal
- Department of Ecology, Charles University, Viničná 7, 12844, Prague 2, Czech Republic
| | - Alexander Beaton
- National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
| | | | - Andrew Tedstone
- Bristol Glaciology Centre, School of Geographical Sciences, University Road, Bristol, BS8 1SS, UK
| | - Mathis P Hain
- Earth and Planetary Sciences, University of California, Santa Cruz, CA, 95064, USA.,Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
| | - Elizabeth Bagshaw
- School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Jennifer Pike
- School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK
| | - Martyn Tranter
- Bristol Glaciology Centre, School of Geographical Sciences, University Road, Bristol, BS8 1SS, UK
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116
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Ng HC, Robinson LF, McManus JF, Mohamed KJ, Jacobel AW, Ivanovic RF, Gregoire LJ, Chen T. Coherent deglacial changes in western Atlantic Ocean circulation. Nat Commun 2018; 9:2947. [PMID: 30054472 PMCID: PMC6063924 DOI: 10.1038/s41467-018-05312-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 06/28/2018] [Indexed: 11/26/2022] Open
Abstract
Abrupt climate changes in the past have been attributed to variations in Atlantic Meridional Overturning Circulation (AMOC) strength. However, the exact timing and magnitude of past AMOC shifts remain elusive, which continues to limit our understanding of the driving mechanisms of such climate variability. Here we show a consistent signal of the 231Pa/230Th proxy that reveals a spatially coherent picture of western Atlantic circulation changes over the last deglaciation, during abrupt millennial-scale climate transitions. At the onset of deglaciation, we observe an early slowdown of circulation in the western Atlantic from around 19 to 16.5 thousand years ago (ka), consistent with the timing of accelerated Eurasian ice melting. The subsequent weakened AMOC state persists for over a millennium (~16.5–15 ka), during which time there is substantial ice rafting from the Laurentide ice sheet. This timing indicates a role for melting ice in driving a two-step AMOC slowdown, with a positive feedback sustaining continued iceberg calving and climate change during Heinrich Stadial 1. The exact timing and magnitude of past changes in Atlantic Ocean circulation, and its relation to abrupt climate changes remains elusive. Here, the authors show a spatially coherent picture of western Atlantic circulation changes, which reveals a two-step AMOC slowdown at the beginning of the deglacial period.
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Affiliation(s)
- Hong Chin Ng
- School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK.
| | - Laura F Robinson
- School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK
| | - Jerry F McManus
- Department of Earth and Environmental Sciences, Columbia University and the Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA
| | - Kais J Mohamed
- Department of Marine Geosciences, University of Vigo, 36310, Vigo, Spain
| | - Allison W Jacobel
- Department of Earth and Environmental Sciences, Columbia University and the Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA
| | - Ruza F Ivanovic
- School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
| | - Lauren J Gregoire
- School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
| | - Tianyu Chen
- School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK.,School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210046, China
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117
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Salonen JS, Helmens KF, Brendryen J, Kuosmanen N, Väliranta M, Goring S, Korpela M, Kylander M, Philip A, Plikk A, Renssen H, Luoto M. Abrupt high-latitude climate events and decoupled seasonal trends during the Eemian. Nat Commun 2018; 9:2851. [PMID: 30030443 PMCID: PMC6054633 DOI: 10.1038/s41467-018-05314-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2018] [Accepted: 06/28/2018] [Indexed: 12/03/2022] Open
Abstract
The Eemian (the Last Interglacial; ca. 129–116 thousand years ago) presents a testbed for assessing environmental responses and climate feedbacks under warmer-than-present boundary conditions. However, climate syntheses for the Eemian remain hampered by lack of data from the high-latitude land areas, masking the climate response and feedbacks in the Arctic. Here we present a high-resolution (sub-centennial) record of Eemian palaeoclimate from northern Finland, with multi-model reconstructions for July and January air temperature. In contrast with the mid-latitudes of Europe, our data show decoupled seasonal trends with falling July and rising January temperatures over the Eemian, due to orbital and oceanic forcings. This leads to an oceanic Late-Eemian climate, consistent with an earlier hypothesis of glacial inception in Europe. The interglacial is further intersected by two strong cooling and drying events. These abrupt events parallel shifts in marine proxy data, linked to disturbances in the North Atlantic oceanic circulation regime. The Eemian period (120 ka) is considered a past analogue for future climatic warming, yet data from the high latitudes remains sparse. Here, the authors show that in Northern Europe, the Eemian saw dramatic climatic shifts, linked to changes in Earth’s orbit and North Atlantic oceanic circulation.
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Affiliation(s)
- J Sakari Salonen
- Department of Geosciences and Geography, University of Helsinki, PO Box 64, FI-00014, Helsinki, Finland.
| | - Karin F Helmens
- Department of Physical Geography and the Bolin Centre for Climate Research, Stockholm University, 106 91, Stockholm, Sweden
| | - Jo Brendryen
- Department of Earth Science, The Bjerknes Centre for Climate Research, and the Jebsen Centre for Deep Sea Research, University of Bergen, PO Box 7803, N-5020, Bergen, Norway
| | - Niina Kuosmanen
- Department of Forest Ecology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21, Praha 6, Czech Republic
| | - Minna Väliranta
- Environmental Change Research Unit (ECRU), Ecosystems and Environment Research Programme, University of Helsinki, PO Box 65, FI-00014, Helsinki, Finland
| | - Simon Goring
- Department of Geography, University of Wisconsin, Madison 550 M Park St, Madison, WI, 53706, USA
| | - Mikko Korpela
- Department of Geosciences and Geography, University of Helsinki, PO Box 64, FI-00014, Helsinki, Finland
| | - Malin Kylander
- Department of Geological Sciences and the Bolin Centre for Climate Research, Stockholm University, 10691, Stockholm, Sweden
| | - Annemarie Philip
- Ecosystem and Landscape Dynamics, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94216, 1090 GE, Amsterdam, The Netherlands
| | - Anna Plikk
- Department of Physical Geography and the Bolin Centre for Climate Research, Stockholm University, 106 91, Stockholm, Sweden
| | - Hans Renssen
- Department of Natural Science and Environmental Health, University College of Southeast Norway, N3800, Bø i Telemark, Norway.,Department of Earth Sciences, VU University Amsterdam, NL-1081HV, Amsterdam, The Netherlands
| | - Miska Luoto
- Department of Geosciences and Geography, University of Helsinki, PO Box 64, FI-00014, Helsinki, Finland
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118
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Maier E, Zhang X, Abelmann A, Gersonde R, Mulitza S, Werner M, Méheust M, Ren J, Chapligin B, Meyer H, Stein R, Tiedemann R, Lohmann G. North Pacific freshwater events linked to changes in glacial ocean circulation. Nature 2018; 559:241-245. [PMID: 29995862 DOI: 10.1038/s41586-018-0276-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 05/14/2018] [Indexed: 11/09/2022]
Abstract
There is compelling evidence that episodic deposition of large volumes of freshwater into the oceans strongly influenced global ocean circulation and climate variability during glacial periods1,2. In the North Atlantic region, episodes of massive freshwater discharge to the North Atlantic Ocean were related to distinct cold periods known as Heinrich Stadials1-3. By contrast, the freshwater history of the North Pacific region remains unclear, giving rise to persistent debates about the existence and possible magnitude of climate links between the North Pacific and North Atlantic oceans during Heinrich Stadials4,5. Here we find that there was a strong connection between changes in North Atlantic circulation during Heinrich Stadials and injections of freshwater from the North American Cordilleran Ice Sheet to the northeastern North Pacific. Our record of diatom δ18O (a measure of the ratio of the stable oxygen isotopes 18O and 16O) over the past 50,000 years shows a decrease in surface seawater δ18O of two to three per thousand, corresponding to a decline in salinity of roughly two to four practical salinity units. This coincided with enhanced deposition of ice-rafted debris and a slight cooling of the sea surface in the northeastern North Pacific during Heinrich Stadials 1 and 4, but not during Heinrich Stadial 3. Furthermore, results from our isotope-enabled model6 suggest that warming of the eastern Equatorial Pacific during Heinrich Stadials was crucial for transmitting the North Atlantic signal to the northeastern North Pacific, where the associated subsurface warming resulted in a discernible freshwater discharge from the Cordilleran Ice Sheet during Heinrich Stadials 1 and 4. However, enhanced background cooling across the northern high latitudes during Heinrich Stadial 3-the coldest period in the past 50,000 years7-prevented subsurface warming of the northeastern North Pacific and thus increased freshwater discharge from the Cordilleran Ice Sheet. In combination, our results show that nonlinear ocean-atmosphere background interactions played a complex role in the dynamics linking the freshwater discharge responses of the North Atlantic and North Pacific during glacial periods.
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Affiliation(s)
- E Maier
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
| | - X Zhang
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
| | - A Abelmann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - R Gersonde
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - S Mulitza
- MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - M Werner
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - M Méheust
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - J Ren
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - B Chapligin
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
| | - H Meyer
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
| | - R Stein
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - R Tiedemann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - G Lohmann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
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119
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Early-warning signals for Dansgaard-Oeschger events in a high-resolution ice core record. Nat Commun 2018; 9:2556. [PMID: 29967370 PMCID: PMC6028441 DOI: 10.1038/s41467-018-04881-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 06/01/2018] [Indexed: 11/09/2022] Open
Abstract
The Dansgaard–Oeschger (DO) events, as observed in oxygen isotope ratios from the North Greenland Ice Core Project (NGRIP) record, are an outstanding example of past abrupt climate transitions. Their physical cause remains debated, and previous research indicated that they are not preceded by classical early-warning signals (EWS). Subsequent research hypothesized that the DO events are caused by bifurcations of physical mechanisms operating at decadal timescales, and proposed to search for EWS in the high-frequency fluctuation levels. Here, a time series with 5-year resolution is obtained from the raw NGRIP record, and significant numbers of EWS in terms of variance and autocorrelation increases are revealed in the decadal-scale variability. Wavelet analysis indicates that the EWS are most pronounced in the 10–50-year periodicity band, confirming the above hypothesis. The DO events are hence neither directly noise-induced nor purely externally forced, which provides valuable constraints regarding potential physical causes. The Dansgaard-Oeschger events are remarkable examples of abrupt climate changes during the last ice age, yet a physical explanation remains debated. Here, Boers shows that these events are preceded by early-warning signals in the high-frequency variability, providing valuable constraints regarding physical causes.
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120
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Pronounced summer warming in northwest Greenland during the Holocene and Last Interglacial. Proc Natl Acad Sci U S A 2018; 115:6357-6362. [PMID: 29866819 DOI: 10.1073/pnas.1720420115] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Projections of future rates of mass loss from the Greenland Ice Sheet are highly uncertain because its sensitivity to warming is unclear. Geologic reconstructions of Quaternary interglacials can illustrate how the ice sheet responded during past warm periods, providing insights into ice sheet behavior and important tests for data-model comparisons. However, paleoclimate records from Greenland are limited: Early Holocene peak warmth has been quantified at only a few sites, and terrestrial sedimentary records of prior interglacials are exceptionally rare due to glacial erosion during the last glacial period. Here, we discuss findings from a lacustrine archive that records both the Holocene and the Last Interglacial (LIG) from Greenland, allowing for direct comparison between two interglacials. Sedimentary chironomid assemblages indicate peak July temperatures 4.0 to 7.0 °C warmer than modern during the Early Holocene maximum in summer insolation. Chaoborus and chironomids in LIG sediments indicate July temperatures at least 5.5 to 8.5 °C warmer than modern. These estimates indicate pronounced warming in northwest Greenland during both interglacials. This helps explain dramatic ice sheet thinning at Camp Century in northwest Greenland during the Early Holocene and, for the LIG, aligns with controversial estimates of Eemian warming from ice core data retrieved in northern Greenland. Converging geologic evidence for strong LIG warming is challenging to reconcile with inferred Greenland Ice Sheet extent during the LIG, and the two appear incompatible in many models of ice sheet evolution. An increase in LIG snowfall could help resolve this problem, pointing to the need for hydroclimate reconstructions from the region.
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121
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Antarctic and global climate history viewed from ice cores. Nature 2018; 558:200-208. [DOI: 10.1038/s41586-018-0172-5] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 03/19/2018] [Indexed: 11/08/2022]
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122
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Instability of the Northeast Greenland Ice Stream over the last 45,000 years. Nat Commun 2018; 9:1872. [PMID: 29760384 PMCID: PMC5951810 DOI: 10.1038/s41467-018-04312-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 04/20/2018] [Indexed: 11/16/2022] Open
Abstract
The sensitivity of the Northeast Greenland Ice Stream (NEGIS) to prolonged warm periods is largely unknown and geological records documenting such long-term changes are needed to place current observations in perspective. Here we use cosmogenic surface exposure and radiocarbon ages to determine the magnitude of NEGIS margin fluctuations over the last 45 kyr (thousand years). We find that the NEGIS experienced slow early Holocene ice-margin retreat of 30–40 m a−1, likely as a result of the buttressing effect of sea-ice or shelf-ice. The NEGIS was ~20–70 km behind its present ice-extent ~41–26 ka and ~7.8–1.2 ka; both periods of high orbital precession index and/or summer temperatures within the projected warming for the end of this century. We show that the NEGIS was smaller than present for approximately half of the last ~45 kyr and is susceptible to subtle changes in climate, which has implications for future stability of this ice stream. The outlet glaciers that comprise the Northeast Greenland Ice Stream (NEGIS) have experienced accelerated retreat in recent years, yet their longterm stability remains unclear. Here, via cosmogenic surface exposure and radiocarbon ages, the authors investigate the stability of the NEGIS for the past 45 kyr.
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123
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Interplay of grounding-line dynamics and sub-shelf melting during retreat of the Bjørnøyrenna Ice Stream. Sci Rep 2018; 8:7196. [PMID: 29740089 PMCID: PMC5940849 DOI: 10.1038/s41598-018-25664-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 04/16/2018] [Indexed: 11/09/2022] Open
Abstract
The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor during the Last Glacial Maximum (21 ky BP). The Bjørnøyrenna Ice Stream was the largest ice stream draining the Barents Sea Ice Sheet and is regarded as an analogue for contemporary ice streams in West Antarctica. Here, the retreat of the Bjørnøyrenna Ice Stream is simulated by means of two numerical ice sheet models and results assessed against geological data. We investigate the sensitivity of the ice stream to changes in ocean temperature and the impact of grounding-line physics on ice stream retreat. Our results suggest that the role played by sub-shelf melting depends on how the grounding-line physics is represented in the models. When an analytic constraint on the ice flux across the grounding line is applied, the retreat of Bjørnøyrenna Ice Stream is primarily driven by internal ice dynamics rather than by oceanic forcing. This suggests that implementations of grounding-line physics need to be carefully assessed when evaluating and predicting the response of contemporary marine-based ice sheets and individual ice streams to ongoing and future ocean warming.
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124
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Schüpbach S, Fischer H, Bigler M, Erhardt T, Gfeller G, Leuenberger D, Mini O, Mulvaney R, Abram NJ, Fleet L, Frey MM, Thomas E, Svensson A, Dahl-Jensen D, Kettner E, Kjaer H, Seierstad I, Steffensen JP, Rasmussen SO, Vallelonga P, Winstrup M, Wegner A, Twarloh B, Wolff K, Schmidt K, Goto-Azuma K, Kuramoto T, Hirabayashi M, Uetake J, Zheng J, Bourgeois J, Fisher D, Zhiheng D, Xiao C, Legrand M, Spolaor A, Gabrieli J, Barbante C, Kang JH, Hur SD, Hong SB, Hwang HJ, Hong S, Hansson M, Iizuka Y, Oyabu I, Muscheler R, Adolphi F, Maselli O, McConnell J, Wolff EW. Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene. Nat Commun 2018; 9:1476. [PMID: 29662058 PMCID: PMC5902614 DOI: 10.1038/s41467-018-03924-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 03/21/2018] [Indexed: 11/16/2022] Open
Abstract
The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little. Past climate changes in Greenland ice were accompanied by large aerosol concentration changes. Here, the authors show that by correcting for transport effects, reliable source changes for biogenic aerosol from North America, sea salt aerosol from the North Atlantic, and dust from East Asian deserts can be derived.
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Affiliation(s)
- S Schüpbach
- Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - H Fischer
- Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland.
| | - M Bigler
- Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - T Erhardt
- Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - G Gfeller
- Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - D Leuenberger
- Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - O Mini
- Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - R Mulvaney
- British Antarctic Survey, National Environment Research Council, High Cross Madingley Road, Cambridge, CB3 0ET, UK
| | - N J Abram
- British Antarctic Survey, National Environment Research Council, High Cross Madingley Road, Cambridge, CB3 0ET, UK.,Research School of Earth Sciences, The Australian National University, Canberra, ACT 2602, Australia
| | - L Fleet
- British Antarctic Survey, National Environment Research Council, High Cross Madingley Road, Cambridge, CB3 0ET, UK
| | - M M Frey
- British Antarctic Survey, National Environment Research Council, High Cross Madingley Road, Cambridge, CB3 0ET, UK
| | - E Thomas
- British Antarctic Survey, National Environment Research Council, High Cross Madingley Road, Cambridge, CB3 0ET, UK
| | - A Svensson
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - D Dahl-Jensen
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - E Kettner
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - H Kjaer
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - I Seierstad
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - J P Steffensen
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - S O Rasmussen
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - P Vallelonga
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - M Winstrup
- Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100, Copenhagen K, Denmark
| | - A Wegner
- Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar-und Meeresforschung, Am Alten Hafen 26, 27568, Bremerhaven, Germany
| | - B Twarloh
- Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar-und Meeresforschung, Am Alten Hafen 26, 27568, Bremerhaven, Germany
| | - K Wolff
- Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar-und Meeresforschung, Am Alten Hafen 26, 27568, Bremerhaven, Germany
| | - K Schmidt
- Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar-und Meeresforschung, Am Alten Hafen 26, 27568, Bremerhaven, Germany
| | - K Goto-Azuma
- National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo, 190-8518, Japan
| | - T Kuramoto
- National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo, 190-8518, Japan.,Fukushima Prefectural Centre for Environmental Creation, 10-2 Fukasaku, Miharu Town, Fukushima, 963-7700, Japan
| | - M Hirabayashi
- National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo, 190-8518, Japan
| | - J Uetake
- National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo, 190-8518, Japan.,Department of Atmospheric Science, Colorado State University, 200 West Lake Street, 1371 Campus Delivery, Fort Collins, CO, 80523-1371, USA
| | - J Zheng
- Natural Resources Canada, Geological Survey of Canada, 601 Booth Street, Ottawa, K1A 0E8, Canada
| | - J Bourgeois
- Natural Resources Canada, Geological Survey of Canada, 601 Booth Street, Ottawa, K1A 0E8, Canada
| | - D Fisher
- Department of Earth Sciences, Environment and Geomatics, University of Ottawa, Ottawa, ON, Canada
| | - D Zhiheng
- State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - C Xiao
- State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - M Legrand
- Institut des Géosciences de l'Environnement, Université Grenoble Alpes, CS 40 700, 38058, Grenoble Cedex 9, France
| | - A Spolaor
- Institute for the Dynamics of Environmental Processes-CNR, University of Venice, via Torino, 155, 30172, Venice-Mestre, Italy
| | - J Gabrieli
- Institute for the Dynamics of Environmental Processes-CNR, University of Venice, via Torino, 155, 30172, Venice-Mestre, Italy
| | - C Barbante
- Institute for the Dynamics of Environmental Processes-CNR, University of Venice, via Torino, 155, 30172, Venice-Mestre, Italy
| | - J-H Kang
- Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon, 21990, Republic of Korea
| | - S D Hur
- Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon, 21990, Republic of Korea
| | - S B Hong
- Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon, 21990, Republic of Korea
| | - H J Hwang
- Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon, 21990, Republic of Korea
| | - S Hong
- Department of Ocean Sciences, Inha University, 100 Inha-ro, Nam-gu, Incheon, 22212, Republic of Korea
| | - M Hansson
- Department of Physical Geography, Stockholm University, S-106 91, Stockholm, Sweden
| | - Y Iizuka
- Department of Physical Geography, Stockholm University, S-106 91, Stockholm, Sweden
| | - I Oyabu
- Department of Physical Geography, Stockholm University, S-106 91, Stockholm, Sweden
| | - R Muscheler
- Department of Geology, Lund University, Solvegatan 12, SE-22362, Lund, Sweden
| | - F Adolphi
- Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland.,Department of Geology, Lund University, Solvegatan 12, SE-22362, Lund, Sweden
| | - O Maselli
- Desert Research Institute, Nevada System of Higher Education, Reno, NV, 89512, USA
| | - J McConnell
- Desert Research Institute, Nevada System of Higher Education, Reno, NV, 89512, USA
| | - E W Wolff
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK
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125
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Abstract
The notion that small changes can have large consequences in the climate or ecosystems has become popular as the concept of tipping points. Typically, tipping points are thought to arise from a loss of stability of an equilibrium when external conditions are slowly varied. However, this appealingly simple view puts us on the wrong foot for understanding a range of abrupt transitions in the climate or ecosystems because complex environmental systems are never in equilibrium. In particular, they are forced by diurnal variations, the seasons, Milankovitch cycles and internal climate oscillations. Here we show how abrupt and sometimes even irreversible change may be evoked by even small shifts in the amplitude or time scale of such environmental oscillations. By using model simulations and reconciling evidence from previous studies we illustrate how these phenomena can be relevant for ecosystems and elements of the climate system including terrestrial ecosystems, Arctic sea ice and monsoons. Although the systems we address are very different and span a broad range of time scales, the phenomena can be understood in a common framework that can help clarify and unify the interpretation of abrupt shifts in the Earth system.
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126
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Abstract
Understanding how the Atlantic Meridional Overturning Circulation (AMOC) evolved during crucial past geological periods is important in order to decipher the interplay between ocean dynamics and global climate change. Previous research, based on geological proxies, has provided invaluable insights into past AMOC changes. However, the causes of the changes in water mass distributions in the Atlantic during different periods remain mostly elusive. Using a state-of-the-art Earth system model, we show that the bulk of NCW in the deep South Atlantic Ocean below 4000 m migrated from the western basins at 125 ka to the eastern basins at 115 ka, though the AMOC strength is only slightly reduced. These changes are consistent with proxy records, and it is mainly due to more penetration of the AABW at depth at 115 ka, as a result of a larger density of AABW formed at 115 ka. Our results show that depth changes in regional deep water pathways can result in large local changes, while the overall AMOC structure hardly changes. Future research should thus be careful when interpreting single proxy records in terms of large-scale AMOC changes, and considering variability of water-mass distributions on sub-basin scale would give more comprehensive interpretations of sediment records.
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Affiliation(s)
- Yiming Luo
- Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Allegaten 70, 5007, Bergen, Norway.
| | - Jerry Tjiputra
- Uni Research Climate, and Bjerknes Centre for Climate Research, Jahnebakken 5, 5007, Bergen, Norway
| | - Chuncheng Guo
- Uni Research Climate, and Bjerknes Centre for Climate Research, Jahnebakken 5, 5007, Bergen, Norway
| | - Zhongshi Zhang
- Uni Research Climate, and Bjerknes Centre for Climate Research, Jahnebakken 5, 5007, Bergen, Norway
| | - Jörg Lippold
- Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234, 69120, Heidelberg, Germany
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127
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Global patterns of declining temperature variability from the Last Glacial Maximum to the Holocene. Nature 2018; 554:356-359. [PMID: 29400701 DOI: 10.1038/nature25454] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 12/12/2017] [Indexed: 11/08/2022]
Abstract
Changes in climate variability are as important for society to address as are changes in mean climate. Contrasting temperature variability during the Last Glacial Maximum and the Holocene can provide insights into the relationship between the mean state of the climate and its variability. However, although glacial-interglacial changes in variability have been quantified for Greenland, a global view remains elusive. Here we use a network of marine and terrestrial temperature proxies to show that temperature variability decreased globally by a factor of four as the climate warmed by 3-8 degrees Celsius from the Last Glacial Maximum (around 21,000 years ago) to the Holocene epoch (the past 11,500 years). This decrease had a clear zonal pattern, with little change in the tropics (by a factor of only 1.6-2.8) and greater change in the mid-latitudes of both hemispheres (by a factor of 3.3-14). By contrast, Greenland ice-core records show a reduction in temperature variability by a factor of 73, suggesting influences beyond local temperature or a decoupling of atmospheric and global surface temperature variability for Greenland. The overall pattern of reduced variability can be explained by changes in the meridional temperature gradient, a mechanism that points to further decreases in temperature variability in a warmer future.
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128
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Cook E, Davies SM, Guðmundsdóttir ER, Abbott PM, Pearce NJG. First identification and characterization of Borrobol-type tephra in the Greenland ice cores: new deposits and improved age estimates. JOURNAL OF QUATERNARY SCIENCE 2018; 33:212-224. [PMID: 29576671 PMCID: PMC5856069 DOI: 10.1002/jqs.3016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 12/02/2017] [Accepted: 12/18/2017] [Indexed: 06/08/2023]
Abstract
Contiguous sampling of ice spanning key intervals of the deglaciation from the Greenland ice cores of NGRIP, GRIP and NEEM has revealed three new silicic cryptotephra deposits that are geochemically similar to the well-known Borrobol Tephra (BT). The BT is complex and confounded by the younger closely timed and compositionally similar Penifiler Tephra (PT). Two of the deposits found in the ice are in Greenland Interstadial 1e (GI-1e) and an older deposit is found in Greenland Stadial 2.1 (GS-2.1). Until now, the BT was confined to GI-1-equivalent lacustrine sequences in the British Isles, Sweden and Germany, and our discovery in Greenland ice extends its distribution and geochemical composition. However, the two cryptotephras that fall within GI-1e ice cannot be separated on the basis of geochemistry and are dated to 14358 ± 177 a b2k and 14252 ± 173 a b2k, just 106 ± 3 years apart. The older deposit is consistent with BT age estimates derived from Scottish sites, while the younger deposit overlaps with both BT and PT age estimates. We suggest that either the BT in Northern European terrestrial sequences represents an amalgamation of tephra from both of the GI-1e events identified in the ice-cores or that it relates to just one of the ice-core events. A firm correlation cannot be established at present due to their strong geochemical similarities. The older tephra horizon, found within all three ice-cores and dated to 17326 ± 319 a b2k, can be correlated to a known layer within marine sediment cores from the North Iceland Shelf (ca. 17179-16754 cal a BP). Despite showing similarities to the BT, this deposit can be distinguished on the basis of lower CaO and TiO2 and is a valuable new tie-point that could eventually be used in high-resolution marine records to compare the climate signals from the ocean and atmosphere.
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Affiliation(s)
- Eliza Cook
- Department of GeographySwansea UniversitySwanseaUK
- Centre for Ice and ClimateNiels Bohr InstituteUniversity of CopenhagenDenmark
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129
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Wan X, Zhang Z. Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia. Proc Biol Sci 2018; 284:rspb.2016.2438. [PMID: 28330916 DOI: 10.1098/rspb.2016.2438] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 02/21/2017] [Indexed: 11/12/2022] Open
Abstract
Climate change and humans are proposed as the two key drivers of total extinction of many large mammals in the Late Pleistocene and Early Holocene, but disentangling their relative roles remains challenging owing to a lack of quantitative evaluation of human impact and climate-driven distribution changes on the extinctions of these large mammals in a continuous temporal-spatial dimension. Here, our analyses showed that temperature change had significant effects on mammoth (genus Mammuthus), rhinoceros (Rhinocerotidae), horse (Equidae) and deer (Cervidae). Rapid global warming was the predominant factor driving the total extinction of mammoths and rhinos in frigid zones from the Late Pleistocene and Early Holocene. Humans showed significant, negative effects on extirpations of the four mammalian taxa, and were the predominant factor causing the extinction or major extirpations of rhinos and horses. Deer survived both rapid climate warming and extensive human impacts. Our study indicates that both the current rates of warming and range shifts of species are much faster than those from the Late Pleistocene to Holocene. Our results provide new insight into the extinction of Late Quaternary megafauna by demonstrating taxon-, period- and region-specific differences in extinction drivers of climate change and human disturbances, and some implications about the extinction risk of animals by recent and ongoing climate warming.
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Affiliation(s)
- Xinru Wan
- State Key Laboratory of Integrated Management of Pest Insects and Rodents in Agriculture, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China.,University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Zhibin Zhang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents in Agriculture, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
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130
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Sánchez Goñi MF, Desprat S, Fletcher WJ, Morales-Molino C, Naughton F, Oliveira D, Urrego DH, Zorzi C. Pollen from the Deep-Sea: A Breakthrough in the Mystery of the Ice Ages. FRONTIERS IN PLANT SCIENCE 2018; 9:38. [PMID: 29434616 PMCID: PMC5790801 DOI: 10.3389/fpls.2018.00038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 01/09/2018] [Indexed: 05/25/2023]
Abstract
Pollen from deep-sea sedimentary sequences provides an integrated regional reconstruction of vegetation and climate (temperature, precipitation, and seasonality) on the adjacent continent. More importantly, the direct correlation of pollen, marine and ice indicators allows comparison of the atmospheric climatic changes that have affected the continent with the response of the Earth's other reservoirs, i.e., the oceans and cryosphere, without any chronological uncertainty. The study of long continuous pollen records from the European margin has revealed a changing and complex interplay between European climate, North Atlantic sea surface temperatures (SSTs), ice growth and decay, and high- and low-latitude forcing at orbital and millennial timescales. These records have shown that the amplitude of the last five terrestrial interglacials was similar above 40°N, while below 40°N their magnitude differed due to precession-modulated changes in seasonality and, particularly, winter precipitation. These records also showed that vegetation response was in dynamic equilibrium with rapid climate changes such as the Dangaard-Oeschger (D-O) cycles and Heinrich events, similar in magnitude and velocity to the ongoing global warming. However, the magnitude of the millennial-scale warming events of the last glacial period was regionally-specific. Precession seems to have imprinted regions below 40°N while obliquity, which controls average annual temperature, probably mediated the impact of D-O warming events above 40°N. A decoupling between high- and low-latitude climate was also observed within last glacial warm (Greenland interstadials) and cold phases (Greenland stadials). The synchronous response of western European vegetation/climate and eastern North Atlantic SSTs to D-O cycles was not a pervasive feature throughout the Quaternary. During periods of ice growth such as MIS 5a/4, MIS 11c/b and MIS 19c/b, repeated millennial-scale cold-air/warm-sea decoupling events occurred on the European margin superimposed to a long-term air-sea decoupling trend. Strong air-sea thermal contrasts promoted the production of water vapor that was then transported northward by the westerlies and fed ice sheets. This interaction between long-term and shorter time-scale climatic variability may have amplified insolation decreases and thus explain the Ice Ages. This hypothesis should be tested by the integration of stochastic processes in Earth models of intermediate complexity.
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Affiliation(s)
- María F Sánchez Goñi
- École Pratique des Hautes Études, EPHE PSL University, Paris, France
- Environnements et Paléoenvironnements Océaniques et Continentaux, UMR 5805, Université de Bordeaux, Pessac, France
| | - Stéphanie Desprat
- École Pratique des Hautes Études, EPHE PSL University, Paris, France
- Environnements et Paléoenvironnements Océaniques et Continentaux, UMR 5805, Université de Bordeaux, Pessac, France
| | - William J Fletcher
- Quaternary Environments and Geoarchaeology, Department of Geography, School of Environment, Education and Development, The University of Manchester, Manchester, United Kingdom
| | - César Morales-Molino
- École Pratique des Hautes Études, EPHE PSL University, Paris, France
- Environnements et Paléoenvironnements Océaniques et Continentaux, UMR 5805, Université de Bordeaux, Pessac, France
| | - Filipa Naughton
- Instituto Português do Mar e da Atmosfera, Portuguese Institute of Sea and Atmosphere, Lisbon, Portugal
- Center of Marine Sciences, Algarve University, Faro, Portugal
| | - Dulce Oliveira
- École Pratique des Hautes Études, EPHE PSL University, Paris, France
- Environnements et Paléoenvironnements Océaniques et Continentaux, UMR 5805, Université de Bordeaux, Pessac, France
- Instituto Português do Mar e da Atmosfera, Portuguese Institute of Sea and Atmosphere, Lisbon, Portugal
| | - Dunia H Urrego
- College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Coralie Zorzi
- GEOTOP, Université du Québec à Montréal, Montreal, QC, Canada
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131
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Carcaillet C, Blarquez O. Fire ecology of a tree glacial refugium on a nunatak with a view on Alpine glaciers. THE NEW PHYTOLOGIST 2017; 216:1281-1290. [PMID: 28805959 DOI: 10.1111/nph.14721] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 06/26/2017] [Indexed: 06/07/2023]
Abstract
In paleoecology, the function of biomass as a fire driver has become a focus of attention in cold ecosystems, and concerns have been raised about climate in this context. Little is known about the fire frequency and fire-plant relationships during glaciation when woodlands were limited and the climate was cold. Fire history and tree biomass were reconstructed from sedimentary charcoal and macroremains, respectively, archived in lake sediments from the western Alps. Two nunataks were investigated, both with lacustrine sediments covering the last 21 000 yr at least. During the Last Glacial Maximum (LGM) and the Lateglacial, fires occurred only on the nunatak sheltering woody plants. Cembra pine (Pinus cembra) and larch (Larix decidua) survived above glaciers during the LGM, thus evidencing a biological refugium and supporting the nunatak theory. We highlighted a long-term relationship between fires and dominant trees over the last 21 000 yr, where fire frequencies track the global climate and the local changes in tree biomass. Glacial climate (dry, cold) does not rule out fires. Fuel load and composition were significant fire drivers, with cembra pine dominating during colder periods with rare fires, and larch during the warmer Holocene with frequent fires. These findings increase knowledge of fire ecology in cold environments, and open perspectives in tree population genetics by considering new areas of tree glacial refugia in Europe.
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Affiliation(s)
- Christopher Carcaillet
- PSL Research University Paris, Ecole Pratique des Hautes Etudes, 4-14 rue Ferrus, Paris, F-75014, France
- Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (UMR5023 CNRS), Université Lyon 1, Villeurbanne Cedex, F-69622, France
- LTER Zone Atelier Alpes, Grenoble, F-38000, France
- International Associated Laboratory (LIA France-Canada MONTABOR), Montpellier, F-34000, France
| | - Olivier Blarquez
- International Associated Laboratory (LIA France-Canada MONTABOR), Montpellier, F-34000, France
- Département de Géographie, Université de Montréal, C.P. 6128 Succ. Centre Ville, Montréal, QC, H3C 3J7, Canada
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132
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Deglacial Tropical Atlantic subsurface warming links ocean circulation variability to the West African Monsoon. Sci Rep 2017; 7:15390. [PMID: 29133905 PMCID: PMC5684145 DOI: 10.1038/s41598-017-15637-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 10/31/2017] [Indexed: 11/27/2022] Open
Abstract
Multiple lines of evidence show that cold stadials in the North Atlantic were accompanied by both reductions in Atlantic Meridional Overturning Circulation (AMOC) and collapses of the West African Monsoon (WAM). Although records of terrestrial change identify abrupt WAM variability across the deglaciation, few studies show how ocean temperatures evolved across the deglaciation. To identify the mechanism linking AMOC to the WAM, we generated a new record of subsurface temperature variability over the last 21 kyr based on Mg/Ca ratios in a sub-thermocline dwelling planktonic foraminifera in an Eastern Equatorial Atlantic (EEA) sediment core from the Niger Delta. Our subsurface temperature record shows abrupt subsurface warming during both the Younger Dryas (YD) and Heinrich Event 1. We also conducted a new transient coupled ocean-atmosphere model simulation across the YD that better resolves the western boundary current dynamics and find a strong negative correlation between AMOC strength and EEA subsurface temperatures caused by changes in ocean circulation and rainfall responses that are consistent with the observed WAM change. Our combined proxy and modeling results provide the first evidence that an oceanic teleconnection between AMOC strength and subsurface temperature in the EEA impacted the intensity of the WAM on millennial time scales.
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133
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Menounos B, Goehring BM, Osborn G, Margold M, Ward B, Bond J, Clarke GKC, Clague JJ, Lakeman T, Koch J, Caffee MW, Gosse J, Stroeven AP, Seguinot J, Heyman J. Cordilleran Ice Sheet mass loss preceded climate reversals near the Pleistocene Termination. Science 2017; 358:781-784. [PMID: 29123066 DOI: 10.1126/science.aan3001] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 10/10/2017] [Indexed: 01/28/2023]
Abstract
The Cordilleran Ice Sheet (CIS) once covered an area comparable to that of Greenland. Previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost Canada as late as 12.5 thousand years ago (ka). New data indicate that substantial areas throughout westernmost Canada were ice free prior to 12.5 ka and some as early as 14.0 ka, with implications for climate dynamics and the timing of meltwater discharge to the Pacific and Arctic oceans. Early Bølling-Allerød warmth halved the mass of the CIS in as little as 500 years, causing 2.5 to 3.0 meters of sea-level rise. Dozens of cirque and valley glaciers, along with the southern margin of the CIS, advanced into recently deglaciated regions during the Bølling-Allerød and Younger Dryas.
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Affiliation(s)
- B Menounos
- Natural Resources and Environmental Studies Institute and Geography, University of Northern British Columbia, Prince George, British Columbia V2N 4Z9, Canada.
| | - B M Goehring
- Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118, USA
| | - G Osborn
- Department of Geoscience, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - M Margold
- Geomorphology and Glaciology, Department of Physical Geography, Stockholm University, S-10691 Stockholm, Sweden
| | - B Ward
- Department of Earth Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - J Bond
- Yukon Geological Survey, Whitehorse, Yukon Y1A 2B5, Canada
| | - G K C Clarke
- Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - J J Clague
- Department of Earth Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - T Lakeman
- Geological Survey of Norway, Trondheim 7040, Norway
| | - J Koch
- Department of Geography, Kwantlen Polytechnic University, Surrey, British Columbia V3W 2M8, Canada
| | - M W Caffee
- Department of Physics and Astronomy and Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - J Gosse
- Department of Earth Sciences, Dalhousie University, Halifax Nova Scotia B3H 4R2, Canada
| | - A P Stroeven
- Geomorphology and Glaciology, Department of Physical Geography, Stockholm University, S-10691 Stockholm, Sweden.,Bolin Centre for Climate Research, Stockholm University, S-10691 Stockholm, Sweden
| | - J Seguinot
- Geomorphology and Glaciology, Department of Physical Geography, Stockholm University, S-10691 Stockholm, Sweden.,Laboratory of Hydraulics, Hydrology and Glaciology, ETH Zürich, Zürich, Switzerland
| | - J Heyman
- Geomorphology and Glaciology, Department of Physical Geography, Stockholm University, S-10691 Stockholm, Sweden.,Department of Earth Sciences, University of Gothenburg, Sweden
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134
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Jo KN, Yi S, Lee JY, Woo KS, Cheng H, Edwards LR, Kim ST. 1000-Year Quasi-Periodicity of Weak Monsoon Events in Temperate Northeast Asia since the Mid-Holocene. Sci Rep 2017; 7:15196. [PMID: 29123205 PMCID: PMC5680219 DOI: 10.1038/s41598-017-15566-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 10/27/2017] [Indexed: 11/29/2022] Open
Abstract
The Holocene variability in the East Asian summer monsoon (EASM) based on speleothem δ18O records has inconsistencies in timing, duration, and expression of millennial-scale events among nearby regions, and even within the same cave. Here, we present another stalagmite δ18O record with multi-decadal time resolution from the temperate Korean Peninsula (KP) for the last 5500 years in order to compare with Holocene millennial-scale EASM events from Southeast Asia. Based on our new stalagmite δ18O record, millennial-scale events since the mid-Holocene were successfully identified in the KP, representing a noticeable cyclic pattern with a periodicity of around 1000 years. We propose that the Holocene millennial-scale events are common hydroclimatic phenomena at least in the East Asian monsoon system. Meanwhile, the shorter periodicity of millennial-scale events than that of the North Atlantic region is likely to decouple the EASM system from the North Atlantic climate system. This observation suggests that weak EASM and North Atlantic Bond events may have been induced independently by direct solar activity (and then possible feedback) and ocean–ice sheet dynamics, respectively, rather than simple propagation from the North Atlantic to the EASM regions.
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Affiliation(s)
- Kyoung-Nam Jo
- Division of Geology and Geophysics, College of Natural Sciences, Kangwon National University, Chuncheon, Korea. .,Critical zone Frontier Research Laboratory (CFRL), Kangwon National University, Chuncheon, Korea.
| | - Sangheon Yi
- Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Korea
| | - Jin-Yong Lee
- Division of Geology and Geophysics, College of Natural Sciences, Kangwon National University, Chuncheon, Korea.,Critical zone Frontier Research Laboratory (CFRL), Kangwon National University, Chuncheon, Korea
| | - Kyung Sik Woo
- Division of Geology and Geophysics, College of Natural Sciences, Kangwon National University, Chuncheon, Korea
| | - Hai Cheng
- Department of Geology and Geophysics, University of Minnesota, Minneapolis, USA.,Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an, China
| | - Lawrence R Edwards
- Department of Geology and Geophysics, University of Minnesota, Minneapolis, USA
| | - Sang-Tae Kim
- School of Geography and Earth Sciences, McMaster University, Hamilton, Canada
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135
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Zimmermann HH, Raschke E, Epp LS, Stoof-Leichsenring KR, Schirrmeister L, Schwamborn G, Herzschuh U. The History of Tree and Shrub Taxa on Bol'shoy Lyakhovsky Island (New Siberian Archipelago) since the Last Interglacial Uncovered by Sedimentary Ancient DNA and Pollen Data. Genes (Basel) 2017; 8:E273. [PMID: 29027988 PMCID: PMC5664123 DOI: 10.3390/genes8100273] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 09/27/2017] [Accepted: 10/04/2017] [Indexed: 11/21/2022] Open
Abstract
Ecosystem boundaries, such as the Arctic-Boreal treeline, are strongly coupled with climate and were spatially highly dynamic during past glacial-interglacial cycles. Only a few studies cover vegetation changes since the last interglacial, as most of the former landscapes are inundated and difficult to access. Using pollen analysis and sedimentary ancient DNA (sedaDNA) metabarcoding, we reveal vegetation changes on Bol'shoy Lyakhovsky Island since the last interglacial from permafrost sediments. Last interglacial samples depict high levels of floral diversity with the presence of trees (Larix, Picea, Populus) and shrubs (Alnus, Betula, Ribes, Cornus, Saliceae) on the currently treeless island. After the Last Glacial Maximum, Larix re-colonised the island but disappeared along with most shrub taxa. This was probably caused by Holocene sea-level rise, which led to increased oceanic conditions on the island. Additionally, we applied two newly developed larch-specific chloroplast markers to evaluate their potential for tracking past population dynamics from environmental samples. The novel markers were successfully re-sequenced and exhibited two variants of each marker in last interglacial samples. SedaDNA can track vegetation changes as well as genetic changes across geographic space through time and can improve our understanding of past processes that shape modern patterns.
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Affiliation(s)
- Heike H Zimmermann
- Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Telegrafenberg A43, 14473 Potsdam, Germany.
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany.
| | - Elena Raschke
- Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Telegrafenberg A43, 14473 Potsdam, Germany.
| | - Laura S Epp
- Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Telegrafenberg A43, 14473 Potsdam, Germany.
| | - Kathleen R Stoof-Leichsenring
- Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Telegrafenberg A43, 14473 Potsdam, Germany.
| | - Lutz Schirrmeister
- Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Telegrafenberg A43, 14473 Potsdam, Germany.
| | - Georg Schwamborn
- Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Telegrafenberg A43, 14473 Potsdam, Germany.
| | - Ulrike Herzschuh
- Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Telegrafenberg A43, 14473 Potsdam, Germany.
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany.
- Institute of Earth and Environmental Sciences, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany.
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136
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Herbert C, Bouchet F. Predictability of escape for a stochastic saddle-node bifurcation: When rare events are typical. Phys Rev E 2017; 96:030201. [PMID: 29346886 DOI: 10.1103/physreve.96.030201] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Indexed: 11/07/2022]
Abstract
Transitions between multiple stable states of nonlinear systems are ubiquitous in physics, chemistry, and beyond. Two types of behaviors are usually seen as mutually exclusive: unpredictable noise-induced transitions and predictable bifurcations of the underlying vector field. Here, we report a different situation, corresponding to a fluctuating system approaching a bifurcation, where both effects collaborate. We show that the problem can be reduced to a single control parameter governing the competition between deterministic and stochastic effects. Two asymptotic regimes are identified: When the control parameter is small (e.g., small noise), deviations from the deterministic case are well described by the Freidlin-Wentzell theory. In particular, escapes over the potential barrier are very rare events. When the parameter is large (e.g., large noise), such events become typical. Unlike pure noise-induced transitions, the distribution of the escape time is peaked around a value which is asymptotically predicted by an adiabatic approximation. We show that the two regimes are characterized by qualitatively different reacting trajectories with algebraic and exponential divergences, respectively.
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Affiliation(s)
- Corentin Herbert
- Univ Lyon, Ens de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France
| | - Freddy Bouchet
- Univ Lyon, Ens de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France
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137
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Asmerom Y, Polyak VJ, Lachniet MS. Extrapolar climate reversal during the last deglaciation. Sci Rep 2017; 7:7157. [PMID: 28769108 PMCID: PMC5541005 DOI: 10.1038/s41598-017-07721-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 07/10/2017] [Indexed: 11/17/2022] Open
Abstract
Large ocean-atmosphere and hydroclimate changes occurred during the last deglaciation, although the interplay between these changes remains ambiguous. Here, we present a speleothem-based high resolution record of Northern Hemisphere atmospheric temperature driven polar jet variability, which matches the Greenland ice core records for the most of the last glacial period, except during the last deglaciation. Our data, combined with data from across the globe, show a dramatic climate reversal during the last deglaciation, which we refer to as the Extrapolar Climate Reversal (ECR). This is the most prominent feature in most tropical and subtropical hydroclimate proxies. The initiation of the ECR coincides with the rapid rise in CO2, in part attributed to upwelling in the Southern Ocean and the near collapse of the Atlantic Meridional Overturning Circulation. We attribute the ECR to upwelling of cold deep waters from the Southern Ocean. This is supported by a variety of proxies showing the incursion of deep Southern Ocean waters into the tropics and subtropics. Regional climate variability across the extropolar regions during the interval previously referred to as the “Mystery Interval” can now be explained in the context of the ECR event.
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Affiliation(s)
- Yemane Asmerom
- Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, 87131, USA.
| | - Victor J Polyak
- Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, 87131, USA
| | - Matthew S Lachniet
- Department of Geoscience, University of Nevada, Las Vegas, Las Vegas, NV, 89154, USA
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138
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García CA, Otero A, Félix P, Presedo J, Márquez DG. Nonparametric estimation of stochastic differential equations with sparse Gaussian processes. Phys Rev E 2017; 96:022104. [PMID: 28950538 DOI: 10.1103/physreve.96.022104] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Indexed: 06/07/2023]
Abstract
The application of stochastic differential equations (SDEs) to the analysis of temporal data has attracted increasing attention, due to their ability to describe complex dynamics with physically interpretable equations. In this paper, we introduce a nonparametric method for estimating the drift and diffusion terms of SDEs from a densely observed discrete time series. The use of Gaussian processes as priors permits working directly in a function-space view and thus the inference takes place directly in this space. To cope with the computational complexity that requires the use of Gaussian processes, a sparse Gaussian process approximation is provided. This approximation permits the efficient computation of predictions for the drift and diffusion terms by using a distribution over a small subset of pseudosamples. The proposed method has been validated using both simulated data and real data from economy and paleoclimatology. The application of the method to real data demonstrates its ability to capture the behavior of complex systems.
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Affiliation(s)
- Constantino A García
- Centro Singular de Investigación en Tecnoloxías da Información (CiTIUS), Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - Abraham Otero
- Department of Information and Communications Systems Engineering, Universidad San Pablo CEU, 28668, Madrid, Spain
| | - Paulo Félix
- Centro Singular de Investigación en Tecnoloxías da Información (CiTIUS), Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - Jesús Presedo
- Centro Singular de Investigación en Tecnoloxías da Información (CiTIUS), Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - David G Márquez
- Centro Singular de Investigación en Tecnoloxías da Información (CiTIUS), Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
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139
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Abstract
The complexity of the climate of the past 122;000 years and recent 2000 years was investigated by analyzing the δ18O records of ice cores based on the sample entropy (SampEn) method and Lempel-Ziv (LZ) complexity. In using SampEn method, the climate complexity is measured by the sample entropy, which is a modified approximate entropy defined in terms of the occurring probability of new modes in a record. A larger sample entropy reflects a higher probability to spot a new mode in the data, and in this sense signals a larger complexity of the sample. The δ18O record of the past 122,000-year is found to have smaller SampEn than the recent 2000-year. This result suggests that the climate of the past 122;000-year has less complexity than that of the recent 2000 years, even though the record for the former exhibits stronger fluctuations and multifractality than the latter. This diagnosis is additionally supported by calculations of LZ complexity, which has smaller value for the record of the past 122;000 years than the recent 2000 years. Our theoretical findings may further contribute to ongoing explorations into the nonlinear statistical character of the climate change.
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140
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Postglacial response of Arctic Ocean gas hydrates to climatic amelioration. Proc Natl Acad Sci U S A 2017; 114:6215-6220. [PMID: 28584081 DOI: 10.1073/pnas.1619288114] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Seafloor methane release due to the thermal dissociation of gas hydrates is pervasive across the continental margins of the Arctic Ocean. Furthermore, there is increasing awareness that shallow hydrate-related methane seeps have appeared due to enhanced warming of Arctic Ocean bottom water during the last century. Although it has been argued that a gas hydrate gun could trigger abrupt climate change, the processes and rates of subsurface/atmospheric natural gas exchange remain uncertain. Here we investigate the dynamics between gas hydrate stability and environmental changes from the height of the last glaciation through to the present day. Using geophysical observations from offshore Svalbard to constrain a coupled ice sheet/gas hydrate model, we identify distinct phases of subglacial methane sequestration and subsequent release on ice sheet retreat that led to the formation of a suite of seafloor domes. Reconstructing the evolution of this dome field, we find that incursions of warm Atlantic bottom water forced rapid gas hydrate dissociation and enhanced methane emissions during the penultimate Heinrich event, the Bølling and Allerød interstadials, and the Holocene optimum. Our results highlight the complex interplay between the cryosphere, geosphere, and atmosphere over the last 30,000 y that led to extensive changes in subseafloor carbon storage that forced distinct episodes of methane release due to natural climate variability well before recent anthropogenic warming.
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141
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Density-dependent processes determine the distribution of chromosomal races of the common shrew Sorex araneus (Lipotyphla, Mammalia). MAMMAL RES 2017. [DOI: 10.1007/s13364-017-0314-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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142
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Portilho-Ramos RC, Chiessi CM, Zhang Y, Mulitza S, Kucera M, Siccha M, Prange M, Paul A. Coupling of equatorial Atlantic surface stratification to glacial shifts in the tropical rainbelt. Sci Rep 2017; 7:1561. [PMID: 28484227 PMCID: PMC5431516 DOI: 10.1038/s41598-017-01629-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 03/29/2017] [Indexed: 11/09/2022] Open
Abstract
The modern state of the Atlantic meridional overturning circulation promotes a northerly maximum of tropical rainfall associated with the Intertropical Convergence Zone (ITCZ). For continental regions, abrupt millennial–scale meridional shifts of this rainbelt are well documented, but the behavior of its oceanic counterpart is unclear due the lack of a robust proxy and high temporal resolution records. Here we show that the Atlantic ITCZ leaves a distinct signature in planktonic foraminifera assemblages. We applied this proxy to investigate the history of the Atlantic ITCZ for the last 30,000 years based on two high temporal resolution records from the western Atlantic Ocean. Our reconstruction indicates that the shallowest mixed layer associated with the Atlantic ITCZ unambiguously shifted meridionally in response to changes in the strength of the Atlantic meridional overturning with a southward displacement during Heinrich Stadials 2–1 and the Younger Dryas. We conclude that the Atlantic ITCZ was located at ca. 1°S (ca. 5° to the south of its modern annual mean position) during Heinrich Stadial 1. This supports a previous hypothesis, which postulates a southern hemisphere position of the oceanic ITCZ during climatic states with substantially reduced or absent cross-equatorial oceanic meridional heat transport.
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Affiliation(s)
- R C Portilho-Ramos
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany. .,Institute of Geosciences, University of São Paulo, São Paulo, Brazil.
| | - C M Chiessi
- School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, Brazil
| | - Y Zhang
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - S Mulitza
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - M Kucera
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - M Siccha
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - M Prange
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - A Paul
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
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143
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Bennett EA, Champlot S, Peters J, Arbuckle BS, Guimaraes S, Pruvost M, Bar-David S, Davis SJM, Gautier M, Kaczensky P, Kuehn R, Mashkour M, Morales-Muñiz A, Pucher E, Tournepiche JF, Uerpmann HP, Bălăşescu A, Germonpré M, Gündem CY, Hemami MR, Moullé PE, Ötzan A, Uerpmann M, Walzer C, Grange T, Geigl EM. Taming the late Quaternary phylogeography of the Eurasiatic wild ass through ancient and modern DNA. PLoS One 2017; 12:e0174216. [PMID: 28422966 PMCID: PMC5396879 DOI: 10.1371/journal.pone.0174216] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 03/06/2017] [Indexed: 11/24/2022] Open
Abstract
Taxonomic over-splitting of extinct or endangered taxa, due to an incomplete knowledge of both skeletal morphological variability and the geographical ranges of past populations, continues to confuse the link between isolated extant populations and their ancestors. This is particularly problematic with the genus Equus. To more reliably determine the evolution and phylogeographic history of the endangered Asiatic wild ass, we studied the genetic diversity and inter-relationships of both extinct and extant populations over the last 100,000 years, including samples throughout its previous range from Western Europe to Southwest and East Asia. Using 229 bp of the mitochondrial hypervariable region, an approach which allowed the inclusion of information from extremely poorly preserved ancient samples, we classify all non-African wild asses into eleven clades that show a clear phylogeographic structure revealing their phylogenetic history. This study places the extinct European wild ass, E. hydruntinus, the phylogeny of which has been debated since the end of the 19th century, into its phylogenetic context within the Asiatic wild asses and reveals recent mitochondrial introgression between populations currently regarded as separate species. The phylogeographic organization of clades resulting from these efforts can be used not only to improve future taxonomic determination of a poorly characterized group of equids, but also to identify historic ranges, interbreeding events between various populations, and the impact of ancient climatic changes. In addition, appropriately placing extant relict populations into a broader phylogeographic and genetic context can better inform ongoing conservation strategies for this highly-endangered species.
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Affiliation(s)
- E. Andrew Bennett
- Institut Jacques Monod, UMR7592, CNRS-Université Paris Diderot, Paris, France
| | - Sophie Champlot
- Institut Jacques Monod, UMR7592, CNRS-Université Paris Diderot, Paris, France
| | - Joris Peters
- Institute of Palaeoanatomy, Domestication Research and the History of Veterinary Medicine, Ludwig-Maximilian University, Munich, Germany
- SNSB, Bavarian State Collection of Anthropology and Palaeoanatomy, München, Germany
| | - Benjamin S. Arbuckle
- Department of Anthropology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Silvia Guimaraes
- Institut Jacques Monod, UMR7592, CNRS-Université Paris Diderot, Paris, France
| | - Mélanie Pruvost
- Institute of Palaeoanatomy, Domestication Research and the History of Veterinary Medicine, Ludwig-Maximilian University, Munich, Germany
| | - Shirli Bar-David
- Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
| | | | - Mathieu Gautier
- Centre de Biologie pour la Gestion des Populations CBGP, Montferrier-sur-Lez, France
| | - Petra Kaczensky
- Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Ralph Kuehn
- Technische Universität München, AG Molekulare Zoologie/Lehrstuhl für Zoologie, Freising, Germany
| | - Marjan Mashkour
- CNRS and Muséum national d'Histoire naturelle, UMR 7209, Archéozoologie, archéobotanique: sociétés, pratiques et environnements, Département Ecologie et Gestion de la Biodiversité, Paris, France
| | - Arturo Morales-Muñiz
- Laboratory of Archaeozoology, Dept. Biologia, Universidad Autonoma de Madrid, Madrid, Spain
| | | | | | - Hans-Peter Uerpmann
- Eberhard-Karls-Universität Tübingen, Institut für Ur- und Frühgeschichte und Archäologie des Mittelalters, Abteilung Ältere Urgeschichte und Quartärökologie, Zentrum für Naturwissenschaftliche Archäologie, Tübingen, Germany
| | - Adrian Bălăşescu
- National History Museum of Romania, National Centre of Pluridisciplinary Research, Bucureşti, Romania
| | - Mietje Germonpré
- Royal Belgian Institute of Natural Sciences, Earth and History of Life, Brussels, Belgium
| | - Can Y. Gündem
- Eberhard-Karls-Universität Tübingen, Institut für Ur- und Frühgeschichte und Archäologie des Mittelalters, Abteilung Ältere Urgeschichte und Quartärökologie, Zentrum für Naturwissenschaftliche Archäologie, Tübingen, Germany
| | - Mahmoud-Reza Hemami
- Department of Natural Resources, Isfahan University of Technology, Isfahan, Iran
| | | | - Aliye Ötzan
- Ankara Üniversitesi Dil ve Tarih-Coğrafya Fakültesi, Ankara, Turkey
| | - Margarete Uerpmann
- Eberhard-Karls-Universität Tübingen, Institut für Ur- und Frühgeschichte und Archäologie des Mittelalters, Abteilung Ältere Urgeschichte und Quartärökologie, Zentrum für Naturwissenschaftliche Archäologie, Tübingen, Germany
| | - Chris Walzer
- Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria
| | - Thierry Grange
- Institut Jacques Monod, UMR7592, CNRS-Université Paris Diderot, Paris, France
- * E-mail: (EMG); (TG)
| | - Eva-Maria Geigl
- Institut Jacques Monod, UMR7592, CNRS-Université Paris Diderot, Paris, France
- * E-mail: (EMG); (TG)
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144
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Wang X, Edwards RL, Auler AS, Cheng H, Kong X, Wang Y, Cruz FW, Dorale JA, Chiang HW. Hydroclimate changes across the Amazon lowlands over the past 45,000 years. Nature 2017; 541:204-207. [PMID: 28079075 DOI: 10.1038/nature20787] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 11/08/2016] [Indexed: 11/09/2022]
Abstract
Reconstructing the history of tropical hydroclimates has been difficult, particularly for the Amazon basin-one of Earth's major centres of deep atmospheric convection. For example, whether the Amazon basin was substantially drier or remained wet during glacial times has been controversial, largely because most study sites have been located on the periphery of the basin, and because interpretations can be complicated by sediment preservation, uncertainties in chronology, and topographical setting. Here we show that rainfall in the basin responds closely to changes in glacial boundary conditions in terms of temperature and atmospheric concentrations of carbon dioxide. Our results are based on a decadally resolved, uranium/thorium-dated, oxygen isotopic record for much of the past 45,000 years, obtained using speleothems from Paraíso Cave in eastern Amazonia; we interpret the record as being broadly related to precipitation. Relative to modern levels, precipitation in the region was about 58% during the Last Glacial Maximum (around 21,000 years ago) and 142% during the mid-Holocene epoch (about 6,000 years ago). We find that, as compared with cave records from the western edge of the lowlands, the Amazon was widely drier during the last glacial period, with much less recycling of water and probably reduced plant transpiration, although the rainforest persisted throughout this time.
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Affiliation(s)
- Xianfeng Wang
- Earth Observatory of Singapore, Nanyang Technological University, 639798 Singapore.,Asian School of the Environment, Nanyang Technological University, 639798 Singapore
| | - R Lawrence Edwards
- Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Augusto S Auler
- Instituto do Carste, Belo Horizonte, Minas Gerais 30150-160, Brazil
| | - Hai Cheng
- Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA.,Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, China
| | - Xinggong Kong
- School of Geography Science, Nanjing Normal University, Nanjing 210023, China
| | - Yongjin Wang
- School of Geography Science, Nanjing Normal University, Nanjing 210023, China
| | - Francisco W Cruz
- Instituto de Geociências, Universidade de São Paulo, São Paulo 05508-080, Brazil
| | - Jeffrey A Dorale
- Department of Earth &Environmental Sciences, University of Iowa, Iowa City, Iowa 52242, USA
| | - Hong-Wei Chiang
- Earth Observatory of Singapore, Nanyang Technological University, 639798 Singapore
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145
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Novello VF, Cruz FW, Vuille M, Stríkis NM, Edwards RL, Cheng H, Emerick S, de Paula MS, Li X, Barreto EDS, Karmann I, Santos RV. A high-resolution history of the South American Monsoon from Last Glacial Maximum to the Holocene. Sci Rep 2017; 7:44267. [PMID: 28281650 PMCID: PMC5345026 DOI: 10.1038/srep44267] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 02/07/2017] [Indexed: 11/22/2022] Open
Abstract
The exact extent, by which the hydrologic cycle in the Neotropics was affected by external forcing during the last deglaciation, remains poorly understood. Here we present a new paleo-rainfall reconstruction based on high-resolution speleothem δ18O records from the core region of the South American Monsoon System (SAMS), documenting the changing hydrological conditions over tropical South America (SA), in particular during abrupt millennial-scale events. This new record provides the best-resolved and most accurately constrained geochronology of any proxy from South America for this time period, spanning from the Last Glacial Maximum (LGM) to the mid-Holocene.
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Affiliation(s)
- Valdir F Novello
- Instituto de Geociências, Universidade de São Paulo, São Paulo 05508-090, Brazil
| | - Francisco W Cruz
- Instituto de Geociências, Universidade de São Paulo, São Paulo 05508-090, Brazil
| | - Mathias Vuille
- Department of Atmospheric and Environmental Sciences, University at Albany, Albany, New York 12222, USA
| | - Nicolás M Stríkis
- Departamento de Geoquímica,Universidade Federal Fluminense, Niterói, Rio de Janeiro 24220-900, Brazil
| | - R Lawrence Edwards
- Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Hai Cheng
- Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA.,Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, China
| | - Suellyn Emerick
- Instituto de Geociências, Universidade de São Paulo, São Paulo 05508-090, Brazil
| | - Marcos S de Paula
- Instituto de Geociências, Universidade de São Paulo, São Paulo 05508-090, Brazil
| | - Xianglei Li
- Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, China
| | - Eline de S Barreto
- Instituto de Geociências, Universidade de São Paulo, São Paulo 05508-090, Brazil
| | - Ivo Karmann
- Instituto de Geociências, Universidade de São Paulo, São Paulo 05508-090, Brazil
| | - Roberto V Santos
- Instituto de Geociências, Universidade de Brasília, Brasília, Brazil
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146
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Li G, Gerhart LM, Harrison SP, Ward JK, Harris JM, Prentice IC. Changes in biomass allocation buffer low CO 2 effects on tree growth during the last glaciation. Sci Rep 2017; 7:43087. [PMID: 28233772 PMCID: PMC5324044 DOI: 10.1038/srep43087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 01/19/2017] [Indexed: 11/09/2022] Open
Abstract
Isotopic measurements on junipers growing in southern California during the last glacial, when the ambient atmospheric [CO2] (ca) was ~180 ppm, show the leaf-internal [CO2] (ci) was approaching the modern CO2 compensation point for C3 plants. Despite this, stem growth rates were similar to today. Using a coupled light-use efficiency and tree growth model, we show that it is possible to maintain a stable ci/ca ratio because both vapour pressure deficit and temperature were decreased under glacial conditions at La Brea, and these have compensating effects on the ci/ca ratio. Reduced photorespiration at lower temperatures would partly mitigate the effect of low ci on gross primary production, but maintenance of present-day radial growth also requires a ~27% reduction in the ratio of fine root mass to leaf area. Such a shift was possible due to reduced drought stress under glacial conditions at La Brea. The necessity for changes in allocation in response to changes in [CO2] is consistent with increased below-ground allocation, and the apparent homoeostasis of radial growth, as ca increases today.
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Affiliation(s)
- Guangqi Li
- Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
- School of Archaeology, Geography and Environmental Sciences (SAGES), Reading University, Reading, UK
| | - Laci M. Gerhart
- Geography Department, Kansas State University, Manhattan, KS 66505, USA
| | - Sandy P. Harrison
- Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
- School of Archaeology, Geography and Environmental Sciences (SAGES), Reading University, Reading, UK
| | - Joy K. Ward
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - John M. Harris
- The La Brea Tar Pits Museum (George C. Page Museum), 5801 Wilshire Boulevard, Los Angeles, CA 90036, USA
| | - I. Colin Prentice
- Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
- AXA Chair of Biosphere and Climate Impacts, Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK
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147
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Half-metre sea-level fluctuations on centennial timescales from mid-Holocene corals of Southeast Asia. Nat Commun 2017; 8:14387. [PMID: 28186122 PMCID: PMC5309900 DOI: 10.1038/ncomms14387] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 12/21/2016] [Indexed: 11/17/2022] Open
Abstract
Sea-level rise is a global problem, yet to forecast future changes, we must understand how and why relative sea level (RSL) varied in the past, on local to global scales. In East and Southeast Asia, details of Holocene RSL are poorly understood. Here we present two independent high-resolution RSL proxy records from Belitung Island on the Sunda Shelf. These records capture spatial variations in glacial isostatic adjustment and paleotidal range, yet both reveal a RSL history between 6850 and 6500 cal years BP that includes two 0.6 m fluctuations, with rates of RSL change reaching 13±4 mm per year (2σ). Observations along the south coast of China, although of a lower resolution, reveal fluctuations similar in amplitude and timing to those on the Sunda Shelf. The consistency of the Southeast Asian records, from sites 2,600 km apart, suggests that the records reflect regional changes in RSL that are unprecedented in modern times. Despite concern over anticipated eustatic sea-level rise, our understanding of past relative sea level, including regional deviations from the global average, is limited. Here, the authors show evidence for synchronous 0.6-m sea-level fluctuations between 6850 and 6500 yr BP at three sites across Southeast Asia.
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148
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Finsinger W, Giesecke T, Brewer S, Leydet M. Emergence patterns of novelty in European vegetation assemblages over the past 15 000 years. Ecol Lett 2017; 20:336-346. [PMID: 28090754 DOI: 10.1111/ele.12731] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 08/25/2016] [Accepted: 12/08/2016] [Indexed: 11/28/2022]
Abstract
Plant communities are not stable over time and biological novelty is predicted to emerge due to climate change, the introduction of exotic species and land-use change. However, the rate at which this novelty may arise over longer time periods has so far received little attention. We reconstruct the emergence of novelty in Europe for a set of baseline conditions over the past 15 000 years to assess past rates of emergence and investigate underlying causes. The emergence of novelty is baseline specific and, during the early-Holocene, was mitigated by the rapid spread of plant taxa. Although novelty generally increases as a function of time, climate and human-induced landscape changes contributed to a non-linear post-glacial trajectory of novelty with jumps corresponding to periods of rapid changes. Emergence of novelty accelerated during the past 1000 years. Historical cultural landscapes experienced a faster novelty development due to the contribution from anthropogenic land-cover changes.
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Affiliation(s)
- Walter Finsinger
- Palaeoecology, ISE-M (UMR 5554 CNRS/UM/EPHE), Place E. Bataillon, 34095, Montpellier, France
| | - Thomas Giesecke
- Department of Palynology and Climate Dynamics, Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen, Untere Karspüle 2, 37073, Göttingen, Germany
| | - Simon Brewer
- Geography Department, University of Utah, 260 S. Central Campus Drive, Salt Lake City, UT, 84119, USA
| | - Michelle Leydet
- IMBE-CNRS, Aix-Marseille Université, IRD, Avignon Université, Technopôle Arbois-Méditerranée, Bât. Villemin - BP 80, F-13545, Aix-en-Provence Cedex 04, France
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149
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Lynch-Stieglitz J. The Atlantic Meridional Overturning Circulation and Abrupt Climate Change. ANNUAL REVIEW OF MARINE SCIENCE 2017; 9:83-104. [PMID: 27814029 DOI: 10.1146/annurev-marine-010816-060415] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.
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Affiliation(s)
- Jean Lynch-Stieglitz
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332;
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Massive remobilization of permafrost carbon during post-glacial warming. Nat Commun 2016; 7:13653. [PMID: 27897191 PMCID: PMC5141343 DOI: 10.1038/ncomms13653] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Accepted: 10/19/2016] [Indexed: 11/25/2022] Open
Abstract
Recent hypotheses, based on atmospheric records and models, suggest that permafrost carbon (PF-C) accumulated during the last glaciation may have been an important source for the atmospheric CO2 rise during post-glacial warming. However, direct physical indications for such PF-C release have so far been absent. Here we use the Laptev Sea (Arctic Ocean) as an archive to investigate PF-C destabilization during the last glacial–interglacial period. Our results show evidence for massive supply of PF-C from Siberian soils as a result of severe active layer deepening in response to the warming. Thawing of PF-C must also have brought about an enhanced organic matter respiration and, thus, these findings suggest that PF-C may indeed have been an important source of CO2 across the extensive permafrost domain. The results challenge current paradigms on the post-glacial CO2 rise and, at the same time, serve as a harbinger for possible consequences of the present-day warming of PF-C soils. Atmospheric CO2 increases during the last deglaciation have been linked to the destabilisation of permafrost carbon reservoirs. Here, using a sediment core from the Laptev Sea, Tesi et al. indicate a massive supply of permafrost carbon was released from Siberia following active layer deepening.
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