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Thermal coupling of the Indo-Pacific warm pool and Southern Ocean over the past 30,000 years. Nat Commun 2022; 13:5457. [PMID: 36115856 PMCID: PMC9482618 DOI: 10.1038/s41467-022-33206-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 09/06/2022] [Indexed: 11/08/2022] Open
Abstract
The role of the tropical Pacific Ocean and its linkages to the southern hemisphere during the last deglacial warming remain highly controversial. Here we explore the evolution of Pacific horizontal and vertical thermal gradients over the past 30 kyr by compiling 340 sea surface and 7 subsurface temperature records, as well as one new ocean heat content record. Our records reveal that La Niña-like conditions dominated during the deglaciation as a result of the more intense warming in the western Pacific warm pool. Both the subsurface temperature and ocean heat content in the warm pool rose earlier than the sea surface temperature, and in phase with South Pacific subsurface temperature and orbital precession, implying that heat exchange between the tropical upper water column and the extratropical Southern Ocean facilitated faster warming in the western Pacific. Our study underscores the key role of the thermal coupling between the warm pool and the Southern Ocean and its relevance for future global warming. The mechanism of the last deglacial global warming is key for future climate. Here, the authors shed light on the pivotal role of the thermal coupling between the western Pacific warm pool and the Southern Ocean.
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Remisiewicz M, Underhill LG. Large-Scale Climatic Patterns Have Stronger Carry-Over Effects than Local Temperatures on Spring Phenology of Long-Distance Passerine Migrants between Europe and Africa. Animals (Basel) 2022; 12:ani12131732. [PMID: 35804633 PMCID: PMC9265019 DOI: 10.3390/ani12131732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 06/30/2022] [Accepted: 07/02/2022] [Indexed: 12/03/2022] Open
Abstract
Simple Summary Spring in Europe has been trending earlier for almost half a century. Long-distance migrant birds, such as the Willow Warbler and Pied Flycatcher, which breed in Europe, have arrived earlier too. It is broadly accepted that warming springs in temperate regions explain the earlier arrival of migrants. However, migration started weeks earlier and thousands of kilometres away. There must be additional cues elsewhere triggering migration. Meteorologists have developed measures of atmospheric circulation which are related to climate variability in wide regions. One of them is the Southern Oscillation Index, which reflects El Niño/La Niña that cause droughts and floods in the southern hemisphere. Other atmospheric circulation patterns, measured by the North Atlantic Oscillation Index and Indian Ocean Dipole, help predict total rainfall for a whole season in various parts of Africa and Europe. Good rains are associated with plant growth and with insect abundance. Insects provide food for most of these migrants. Therefore, this paper asks the question: “Is the timing of arrival of long-distance migrants in spring related to the climates they experience in the places where they are over the year prior to arrival in Europe?” This paper says the answer is “Yes”. Abstract Earlier springs in temperate regions since the 1980s, attributed to climate change, are thought to influence the earlier arrival of long-distance migrant passerines. However, this migration was initiated weeks earlier in Africa, where the Southern Oscillation, Indian Ocean Dipole, North Atlantic Oscillation drive climatic variability, and may additionally influence the migrants. Multiple regressions investigated whether 15 indices of climate in Africa and Europe explained the variability in timing of arrival for seven trans-Saharan migrants. Our response variable was Annual Anomaly (AA), derived from standardized mistnetting from 1982–2021 at Bukowo, Polish Baltic Sea. For each species, the best models explained a considerable part of the annual variation in the timing of spring’s arrival by two to seven climate variables. For five species, the models included variables related to temperature or precipitation in the Sahel. Similarly, the models included variables related to the North Atlantic Oscillation (for four species), Indian Ocean Dipole (three), and Southern Oscillation (three). All included the Scandinavian Pattern in the previous summer. Our conclusion is that climate variables operating on long-distance migrants in the areas where they are present in the preceding year drive the phenological variation of spring migration. These results have implications for our understanding of carry-over effects.
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Affiliation(s)
- Magdalena Remisiewicz
- Bird Migration Research Station, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland
- Department of Biological Sciences, University of Cape Town, Rondebosch, Cape Town 7701, South Africa;
- Correspondence:
| | - Les G. Underhill
- Department of Biological Sciences, University of Cape Town, Rondebosch, Cape Town 7701, South Africa;
- Biodiversity and Development Institute, 25 Old Farm Road, Rondebosch, Cape Town 7700, South Africa
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3
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Reynolds AR, Seymour KL, Evans DC. Smilodon fatalis siblings reveal life history in a saber-toothed cat. iScience 2021; 24:101916. [PMID: 33532710 PMCID: PMC7835254 DOI: 10.1016/j.isci.2020.101916] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/18/2020] [Accepted: 12/07/2020] [Indexed: 11/23/2022] Open
Abstract
The saber-toothed cat Smilodon fatalis is known predominantly from “predator trap” deposits, which has made many aspects of its life history difficult to infer. Here, we describe an association of at least two subadult and one adult S. fatalis from Pleistocene coastal deposits in Ecuador. The assemblage likely derived from a catastrophic mass mortality event, and thereby provides insights into the behavior of the species. The presence of a P3 in the subadult dentaries suggests inheritance, a rare instance of familial relatedness in the fossil record. The siblings were at least two years old and were associated with an adult that was likely their mother, indicating prolonged parental care in S. fatalis. Comparison with the growth of pantherine cats suggests that S. fatalis had a unique growth strategy among big cats that combines a growth rate that is similar to a tiger and the extended growth period of a lion. Association of two subadult and one adult Smilodon fatalis from Ecuador Rare, likely genetic condition suggests subadults are siblings S. fatalis appears to have exhibited fast growth over a prolonged period Comparison with growth in lions and tigers suggests a unique growth strategy
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Affiliation(s)
- Ashley R. Reynolds
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, ON M5S 1C6, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada
- Corresponding author
| | - Kevin L. Seymour
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, ON M5S 1C6, Canada
| | - David C. Evans
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, ON M5S 1C6, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada
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4
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Abstract
The Younger Dryas (YD), arguably the most widely studied millennial-scale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon-Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard-Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ∼11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ∼11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic-Asian Monsoon-Westerlies directionality of climatic recovery.
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End of Green Sahara amplified mid- to late Holocene megadroughts in mainland Southeast Asia. Nat Commun 2020; 11:4204. [PMID: 32826905 PMCID: PMC7442841 DOI: 10.1038/s41467-020-17927-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 07/20/2020] [Indexed: 12/02/2022] Open
Abstract
Between 5 and 4 thousand years ago, crippling megadroughts led to the disruption of ancient civilizations across parts of Africa and Asia, yet the extent of these climate extremes in mainland Southeast Asia (MSEA) has never been defined. This is despite archeological evidence showing a shift in human settlement patterns across the region during this period. We report evidence from stalagmite climate records indicating a major decrease of monsoon rainfall in MSEA during the mid- to late Holocene, coincident with African monsoon failure during the end of the Green Sahara. Through a set of modeling experiments, we show that reduced vegetation and increased dust loads during the Green Sahara termination shifted the Walker circulation eastward and cooled the Indian Ocean, causing a reduction in monsoon rainfall in MSEA. Our results indicate that vegetation-dust climate feedbacks from Sahara drying may have been the catalyst for societal shifts in MSEA via ocean-atmospheric teleconnections. The mid-Holocene has seen a number of climate shifts, which have been associated with societal changes. Here, the authors investigate in a centuries long megadrought in Southeast Asia during the mid-Holocene, possibly caused by the end of the Green Sahara period.
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6
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Praetorius SK, Condron A, Mix AC, Walczak MH, McKay JL, Du J. The role of Northeast Pacific meltwater events in deglacial climate change. SCIENCE ADVANCES 2020; 6:eaay2915. [PMID: 32133399 PMCID: PMC7043920 DOI: 10.1126/sciadv.aay2915] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 11/22/2019] [Indexed: 06/10/2023]
Abstract
Columbia River megafloods occurred repeatedly during the last deglaciation, but the impacts of this fresh water on Pacific hydrography are largely unknown. To reconstruct changes in ocean circulation during this period, we used a numerical model to simulate the flow trajectory of Columbia River megafloods and compiled records of sea surface temperature, paleo-salinity, and deep-water radiocarbon from marine sediment cores in the Northeast Pacific. The North Pacific sea surface cooled and freshened during the early deglacial (19.0-16.5 ka) and Younger Dryas (12.9-11.7 ka) intervals, coincident with the appearance of subsurface water masses depleted in radiocarbon relative to the sea surface. We infer that Pacific meltwater fluxes contributed to net Northern Hemisphere cooling prior to North Atlantic Heinrich Events, and again during the Younger Dryas stadial. Abrupt warming in the Northeast Pacific similarly contributed to hemispheric warming during the Bølling and Holocene transitions. These findings underscore the importance of changes in North Pacific freshwater fluxes and circulation in deglacial climate events.
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Affiliation(s)
| | - Alan Condron
- Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Alan C. Mix
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Maureen H. Walczak
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Jennifer L. McKay
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - Jianghui Du
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
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7
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Pirog A, Jaquemet S, Ravigné V, Cliff G, Clua E, Holmes BJ, Hussey NE, Nevill JEG, Temple AJ, Berggren P, Vigliola L, Magalon H. Genetic population structure and demography of an apex predator, the tiger shark Galeocerdo cuvier. Ecol Evol 2019; 9:5551-5571. [PMID: 31160982 PMCID: PMC6540675 DOI: 10.1002/ece3.5111] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 01/20/2019] [Accepted: 02/26/2019] [Indexed: 12/16/2022] Open
Abstract
Population genetics has been increasingly applied to study large sharks over the last decade. Whilst large shark species are often difficult to study with direct methods, improved knowledge is needed for both population management and conservation, especially for species vulnerable to anthropogenic and climatic impacts. The tiger shark, Galeocerdo cuvier, is an apex predator known to play important direct and indirect roles in tropical and subtropical marine ecosystems. While the global and Indo-West Pacific population genetic structure of this species has recently been investigated, questions remain over population structure and demographic history within the western Indian (WIO) and within the western Pacific Oceans (WPO). To address the knowledge gap in tiger shark regional population structures, the genetic diversity of 286 individuals sampled in seven localities was investigated using 27 microsatellite loci and three mitochondrial genes (CR,COI, and cytb). A weak genetic differentiation was observed between the WIO and the WPO, suggesting high genetic connectivity. This result agrees with previous studies and highlights the importance of the pelagic behavior of this species to ensure gene flow. Using approximate Bayesian computation to couple information from both nuclear and mitochondrial markers, evidence of a recent bottleneck in the Holocene (2,000-3,000 years ago) was found, which is the most probable cause for the low genetic diversity observed. A contemporary effective population size as low as 111 [43,369] was estimated during the bottleneck. Together, these results indicate low genetic diversity that may reflect a vulnerable population sensitive to regional pressures. Conservation measures are thus needed to protect a species that is classified as Near Threatened.
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Affiliation(s)
- Agathe Pirog
- UMR ENTROPIE (Université de La Réunion/IRD/CNRS)Université de La RéunionSaint Denis, La RéunionFrance
| | - Sébastien Jaquemet
- UMR ENTROPIE (Université de La Réunion/IRD/CNRS)Université de La RéunionSaint Denis, La RéunionFrance
| | | | - Geremy Cliff
- KwaZulu‐Natal Sharks BoardUmhlanga RocksSouth Africa
- School of Life SciencesUniversity of KwaZulu‐NatalDurbanSouth Africa
| | - Eric Clua
- EPHE‐CNRS‐UPVDCNRS UPVDUSR 3278 CRIOBEPSL Research UniversityPerpignanFrance
- Laboratoire d'Excellence CORAILPerpignanFrance
| | - Bonnie J. Holmes
- School of Biological SciencesUniversity of Queensland, St LuciaBrisbaneQueenslandAustralia
| | - Nigel E. Hussey
- Biological SciencesUniversity of WindsorWindsorOntarioCanada
| | | | - Andrew J. Temple
- School of Natural and Environmental SciencesNewcastle UniversityNewcastle‐upon‐TyneUK
| | - Per Berggren
- School of Natural and Environmental SciencesNewcastle UniversityNewcastle‐upon‐TyneUK
| | - Laurent Vigliola
- Laboratoire d'Excellence CORAILPerpignanFrance
- UMR ENTROPIE (Université de La Réunion/IRD/CNRS)Institut de Recherche pour le DéveloppementNouméaNouvelle CalédonieFrance
| | - Hélène Magalon
- UMR ENTROPIE (Université de La Réunion/IRD/CNRS)Université de La RéunionSaint Denis, La RéunionFrance
- Laboratoire d'Excellence CORAILPerpignanFrance
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8
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DiNezio PN, Tierney JE, Otto-Bliesner BL, Timmermann A, Bhattacharya T, Rosenbloom N, Brady E. Glacial changes in tropical climate amplified by the Indian Ocean. SCIENCE ADVANCES 2018; 4:eaat9658. [PMID: 30547084 PMCID: PMC6291310 DOI: 10.1126/sciadv.aat9658] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 11/14/2018] [Indexed: 05/26/2023]
Abstract
The mechanisms driving glacial-interglacial changes in the climate of the Indo-Pacific warm pool are poorly understood. Here, we address this question by combining paleoclimate proxies with model simulations of the Last Glacial Maximum climate. We find evidence of two mechanisms explaining key patterns of ocean cooling and rainfall change interpreted from proxy data. Exposure of the Sahul shelf excites a positive ocean-atmosphere feedback involving a stronger surface temperature gradient along the equatorial Indian Ocean and a weaker Walker circulation-a response explaining the drier/wetter dipole across the basin. Northern Hemisphere cooling by ice sheet albedo drives a monsoonal retreat across Africa and the Arabian Peninsula-a response that triggers a weakening of the Indian monsoon via cooling of the Arabian Sea and associated reductions in moisture supply. These results demonstrate the importance of air-sea interactions in the Indian Ocean, amplifying externally forced climate changes over a large part of the tropics.
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Affiliation(s)
- Pedro N. DiNezio
- Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, J.J. Pickle Research Campus, Building 196 10100 Burnet Road (R2200), Austin, TX 78758, USA
| | - Jessica E. Tierney
- Department of Geosciences, The University of Arizona, 1040 E 4th Street, Tucson, AZ 85721, USA
| | - Bette L. Otto-Bliesner
- National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, 1850 Table Mesa Drive, Boulder, CO 80305, USA
| | - Axel Timmermann
- Center for Climate Physics, Institute for Basic Science, Busandaehak-ro 63beon-gil 2, Geumjeong-gu, Busan 46241, South Korea
- Pusan National University, Busandaehak-ro 63beon-gil 2, Geumjeong-gu, Busan 46241, South Korea
| | - Tripti Bhattacharya
- Department of Earth Science, Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244-1070, USA
| | - Nan Rosenbloom
- National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, 1850 Table Mesa Drive, Boulder, CO 80305, USA
| | - Esther Brady
- National Center for Atmospheric Research, Climate and Global Dynamics Laboratory, 1850 Table Mesa Drive, Boulder, CO 80305, USA
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9
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Zhang Y, Zhang X, Chiessi CM, Mulitza S, Zhang X, Lohmann G, Prange M, Behling H, Zabel M, Govin A, Sawakuchi AO, Cruz FW, Wefer G. Equatorial Pacific forcing of western Amazonian precipitation during Heinrich Stadial 1. Sci Rep 2016; 6:35866. [PMID: 27779213 PMCID: PMC5078807 DOI: 10.1038/srep35866] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 10/07/2016] [Indexed: 11/09/2022] Open
Abstract
Abundant hydroclimatic evidence from western Amazonia and the adjacent Andes documents wet conditions during Heinrich Stadial 1 (HS1, 18–15 ka), a cold period in the high latitudes of the North Atlantic. This precipitation anomaly was attributed to a strengthening of the South American summer monsoon due to a change in the Atlantic interhemispheric sea surface temperature (SST) gradient. However, the physical viability of this mechanism has never been rigorously tested. We address this issue by combining a thorough compilation of tropical South American paleorecords and a set of atmosphere model sensitivity experiments. Our results show that the Atlantic SST variations alone, although leading to dry conditions in northern South America and wet conditions in northeastern Brazil, cannot produce increased precipitation over western Amazonia and the adjacent Andes during HS1. Instead, an eastern equatorial Pacific SST increase (i.e., 0.5–1.5 °C), in response to the slowdown of the Atlantic Meridional Overturning Circulation during HS1, is crucial to generate the wet conditions in these regions. The mechanism works via anomalous low sea level pressure over the eastern equatorial Pacific, which promotes a regional easterly low-level wind anomaly and moisture recycling from central Amazonia towards the Andes.
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Affiliation(s)
- Yancheng Zhang
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany
| | - Xu Zhang
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Cristiano M Chiessi
- School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, Brazil
| | - Stefan Mulitza
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany
| | - Xiao Zhang
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany
| | - Gerrit Lohmann
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany.,Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Matthias Prange
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany
| | - Hermann Behling
- Department of Palynology and Climate Dynamics, Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen, Germany
| | - Matthias Zabel
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany
| | - Aline Govin
- IPSL/LSCE, Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-UVSQ), Université Paris Saclay, Gif sur Yvette, France
| | - André O Sawakuchi
- Institute of Geosciences, University of São Paulo, São Paulo, Brazil
| | - Francisco W Cruz
- Institute of Geosciences, University of São Paulo, São Paulo, Brazil
| | - Gerold Wefer
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany
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10
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Glasser NF, Jansson KN, Duller GAT, Singarayer J, Holloway M, Harrison S. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean. Sci Rep 2016; 6:21064. [PMID: 26869235 PMCID: PMC4751529 DOI: 10.1038/srep21064] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 01/14/2016] [Indexed: 11/30/2022] Open
Abstract
Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface “hosing” to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate.
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Affiliation(s)
- Neil F Glasser
- Department of Geography and Earth Sciences, Aberystwyth University, SY23 3DB, Wales, UK
| | - Krister N Jansson
- Department of Physical Geography, Stockholm University, SE-10691, Stockholm, Sweden
| | - Geoffrey A T Duller
- Department of Geography and Earth Sciences, Aberystwyth University, SY23 3DB, Wales, UK
| | - Joy Singarayer
- Department of Meteorology, University of Reading, Earley Gate, PO Box 243, Reading, RG6 6BB, UK
| | - Max Holloway
- British Antarctic Survey, Madingley Road, Cambridge, UK
| | - Stephan Harrison
- College of Life &Environmental Science, Exeter University TR10 9EZ, Cornwall, UK
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11
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Ford HL, Ravelo AC, Polissar PJ. Reduced El Niño-Southern Oscillation during the Last Glacial Maximum. Science 2015; 347:255-8. [PMID: 25593181 DOI: 10.1126/science.1258437] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
El Niño-Southern Oscillation (ENSO) is a major source of global interannual variability, but its response to climate change is uncertain. Paleoclimate records from the Last Glacial Maximum (LGM) provide insight into ENSO behavior when global boundary conditions (ice sheet extent, atmospheric partial pressure of CO2) were different from those today. In this work, we reconstruct LGM temperature variability at equatorial Pacific sites using measurements of individual planktonic foraminifera shells. A deep equatorial thermocline altered the dynamics in the eastern equatorial cold tongue, resulting in reduced ENSO variability during the LGM compared to the Late Holocene. These results suggest that ENSO was not tied directly to the east-west temperature gradient, as previously suggested. Rather, the thermocline of the eastern equatorial Pacific played a decisive role in the ENSO response to LGM climate.
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Affiliation(s)
- Heather L Ford
- Ocean Sciences Department, University of California, Santa Cruz, CA 95064, USA. Biology and Paleo Environment, Lamont-Doherty Earth Observatory, Palisades, NY 10964, USA.
| | - A Christina Ravelo
- Ocean Sciences Department, University of California, Santa Cruz, CA 95064, USA
| | - Pratigya J Polissar
- Biology and Paleo Environment, Lamont-Doherty Earth Observatory, Palisades, NY 10964, USA
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12
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Palaeoclimate reconstructions reveal a strong link between El Niño-Southern Oscillation and Tropical Pacific mean state. Nat Commun 2014; 4:2692. [PMID: 24176877 DOI: 10.1038/ncomms3692] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 10/01/2013] [Indexed: 11/09/2022] Open
Abstract
The El Niño-Southern Oscillation (ENSO) is one of the most important components of the global climate system, but its potential response to an anthropogenic increase in atmospheric CO2 remains largely unknown. One of the major limitations in ENSO prediction is our poor understanding of the relationship between ENSO variability and long-term changes in Tropical Pacific oceanography. Here we investigate this relationship using palaeorecords derived from the geochemistry of planktonic foraminifera. Our results indicate a strong negative correlation between ENSO variability and zonal gradient of sea-surface temperatures across the Tropical Pacific during the last 22 ky. This strong correlation implies a mechanistic link that tightly couples zonal sea-surface temperature gradient and ENSO variability during large climate changes and provides a unique insight into potential ENSO evolution in the future by suggesting enhanced ENSO variability under a global warming scenario.
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13
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Hydroclimate of the western Indo-Pacific Warm Pool during the past 24,000 years. Proc Natl Acad Sci U S A 2014; 111:9402-6. [PMID: 24979768 DOI: 10.1073/pnas.1323585111] [Citation(s) in RCA: 50] [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
The Indo-Pacific Warm Pool (IPWP) is a key site for the global hydrologic cycle, and modern observations indicate that both the Indian Ocean Zonal Mode (IOZM) and the El Niño Southern Oscillation exert strong influence on its regional hydrologic characteristics. Detailed insight into the natural range of IPWP dynamics and underlying climate mechanisms is, however, limited by the spatial and temporal coverage of climate data. In particular, long-term (multimillennial) precipitation patterns of the western IPWP, a key location for IOZM dynamics, are poorly understood. To help rectify this, we have reconstructed rainfall changes over Northwest Sumatra (western IPWP, Indian Ocean) throughout the past 24,000 y based on the stable hydrogen and carbon isotopic compositions (δD and δ(13)C, respectively) of terrestrial plant waxes. As a general feature of western IPWP hydrology, our data suggest similar rainfall amounts during the Last Glacial Maximum and the Holocene, contradicting previous claims that precipitation increased across the IPWP in response to deglacial changes in sea level and/or the position of the Intertropical Convergence Zone. We attribute this discrepancy to regional differences in topography and different responses to glacioeustatically forced changes in coastline position within the continental IPWP. During the Holocene, our data indicate considerable variations in rainfall amount. Comparison of our isotope time series to paleoclimate records from the Indian Ocean realm reveals previously unrecognized fluctuations of the Indian Ocean precipitation dipole during the Holocene, indicating that oscillations of the IOZM mean state have been a constituent of western IPWP rainfall over the past ten thousand years.
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14
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Increasing summer rainfall in arid eastern-Central Asia over the past 8500 years. Sci Rep 2014; 4:5279. [PMID: 24923304 PMCID: PMC4055903 DOI: 10.1038/srep05279] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Accepted: 05/16/2014] [Indexed: 11/08/2022] Open
Abstract
A detailed and well-dated proxy record of summer rainfall variation in arid Central Asia is lacking. Here, we report a long-term, high resolution record of summer rainfall extracted from a peat bog in arid eastern-Central Asia (AECA). The record indicates a slowly but steadily increasing trend of summer rainfall in the AECA over the past 8500 years. On this long-term trend are superimposed several abrupt increases in rainfall on millennial timescales that correspond to rapid cooling events in the North Atlantic. During the last millennium, the hydrological climate pattern of the AECA underwent a major change. The rainfall in the past century has reached its highest level over the 8500-year history, highlighting the significant impact of the human-induced greenhouse effect on the hydrological climate in the AECA. Our results demonstrate that even in very dry eastern-Central Asia, the climate can become wetter under global warming.
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Collins AF, Bush MB, Sachs JP. Microrefugia and species persistence in the Galápagos highlands: a 26,000-year paleoecological perspective. Front Genet 2013; 4:269. [PMID: 24348520 PMCID: PMC3848256 DOI: 10.3389/fgene.2013.00269] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 11/18/2013] [Indexed: 11/13/2022] Open
Abstract
The Galápagos Islands are known to have experienced significant drought during the Quaternary. The loss of mesophytic upland habitats has been suggested to underlie the relatively lower endemism of upland compared with lowland plant assemblages. A fossil pollen record spanning the last 26,000 years from an upland bog on Santa Cruz Island, revealed the persistent presence of highland pollen and spore types during the last glacial maximum and a millennial-scale series of droughts in the mid Holocene. The absence of lowland taxa and presence of mesic taxa led to the conclusion that the highland flora of the Galápagos persisted during both these periods. The resiliency of the highland flora of the Galápagos to long-term drought contradicts an earlier hypothesis that an extinction of highland taxa occurred during the last glacial maximum and that rapid Holocene speciation created the modern plant assemblage within the last 10,000 years. Based on the palynological data, we suggest that, even during the height of glacial and Holocene droughts, cool sea-surface temperatures and strong trade-wind activity would have promoted persistent ground level cloudiness that provided the necessary moisture inputs to maintain microrefugia for mesophytic plants. Although moist conditions were maintained, the lack of precipitation caused the loss of open water habitat during such events, and accounts for the known extinctions of species such as Azolla sp., and Elatine sp., while other moisture dependent taxa, i.e., Cyathea weatherbyana, persisted.
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Affiliation(s)
- Aaron F Collins
- Department of Biological Sciences, Florida Institute of Technology Melbourne, FL, USA
| | - Mark B Bush
- Department of Biological Sciences, Florida Institute of Technology Melbourne, FL, USA
| | - Julian P Sachs
- School of Oceanography, University of Washington Seattle, WA, USA
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Asynchronous marine-terrestrial signals of the last deglacial warming in East Asia associated with low- and high-latitude climate changes. Proc Natl Acad Sci U S A 2013; 110:9657-62. [PMID: 23720306 DOI: 10.1073/pnas.1300025110] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A high-resolution multiproxy record, including pollen, foraminifera, and alkenone paleothermometry, obtained from a single core (DG9603) from the Okinawa Trough, East China Sea (ECS), provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka. On land, the deglacial stage was characterized by rapid warming, as reflected by paleovegetation, and it began ca. 15 kaBP, consistent with the timing of the last deglacial warming in Greenland. However, sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20-19 kaBP, as in the Western Pacific Warm Pool (WPWP). Sea surface temperatures in the Okinawa Trough were influenced mainly by heat transport from the tropical western Pacific Ocean by the Kuroshio Current, but the epicontinental vegetation of the ECS was influenced by atmospheric circulation linked to the northern high-latitude climate. Asynchronous terrestrial and marine signals of the last deglacial warming in East Asia were thus clearly related to ocean currents and atmospheric circulation. We argue that (i) early warming seawater of the WPWP, driven by low-latitude insolation and trade winds, moved northward via the Kuroshio Current and triggered marine warming along the ECS around 20-19 kaBP similar to that in the WPWP, and (ii) an almost complete shutdown of the Atlantic Meridional Overturning Circulation ca. 18-15 kaBP was associated with cold Heinrich stadial-1 and delayed terrestrial warming during the last deglacial warming until ca. 15 kaBP at northern high latitudes, and hence in East Asia. Terrestrial deglacial warming therefore lagged behind marine changes by ca. 3-4 ka.
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Wang Z, Liu W. Calibration of the U
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index of long-chain alkenones with the in-situ water temperature in Lake Qinghai in the Tibetan Plateau. CHINESE SCIENCE BULLETIN 2012. [DOI: 10.1007/s11434-012-5527-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Minckley TA, Shriver RK, Shuman B. Resilience and regime change in a southern Rocky Mountain ecosystem during the past 17 000 years. ECOL MONOGR 2012. [DOI: 10.1890/11-0283.1] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Nance HA, Klimley P, Galván-Magaña F, Martínez-Ortíz J, Marko PB. Demographic processes underlying subtle patterns of population structure in the scalloped hammerhead shark, Sphyrna lewini. PLoS One 2011; 6:e21459. [PMID: 21789171 PMCID: PMC3137562 DOI: 10.1371/journal.pone.0021459] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Accepted: 06/02/2011] [Indexed: 12/14/2022] Open
Abstract
Genetic diversity (θ), effective population size (N(e)), and contemporary levels of gene flow are important parameters to estimate for species of conservation concern, such as the globally endangered scalloped hammerhead shark, Sphyrna lewini. Therefore, we have reconstructed the demographic history of S. lewini across its Eastern Pacific (EP) range by applying classical and coalescent population genetic methods to a combination of 15 microsatellite loci and mtDNA control region sequences. In addition to significant population genetic structure and isolation-by-distance among seven coastal sites between central Mexico and Ecuador, the analyses revealed that all populations have experienced a bottleneck and that all current values of θ are at least an order of magnitude smaller than ancestral θ, indicating large decreases in N(e) (θ = 4N(e)μ), where μ is the mutation rate. Application of the isolation-with-migration (IM) model showed modest but significant genetic connectivity between most sampled sites (point estimates of Nm = 0.1-16.7), with divergence times (t) among all populations significantly greater than zero. Using a conservative (i.e., slow) fossil-based taxon-specific phylogenetic calibration for mtDNA mutation rates, posterior probability distributions (PPDs) for the onset of the decline in N(e) predate modern fishing in this region. The cause of decline over the last several thousand years is unknown but is highly atypical as a post-glacial demographic history. Regardless of the cause, our data and analyses suggest that S. lewini was far more abundant throughout the EP in the past than at present.
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Affiliation(s)
- Holly A. Nance
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Peter Klimley
- Department of Wildlife, Fish, and Conservation Biology, University of California Davis, Davis, California, United States of America
| | | | | | - Peter B. Marko
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
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Vecchi GA, Clement A, Soden BJ. Examining the Tropical Pacific's Response to Global Warming. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2008eo090002] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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DiNezio P, Clement A, Vecchi G. Reconciling Differing Views of Tropical Pacific Climate Change. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010eo160001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Warming magnitude of Indonesian Throughflow during the penultimate deglaciation (Termination II) and its relationship with climate change in high-latitude regions. CHINESE SCIENCE BULLETIN-CHINESE 2010. [DOI: 10.1007/s11434-010-4172-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Du J, Huang B. Variations in upper water structure during MIS 3 from the western South China Sea. CHINESE SCIENCE BULLETIN-CHINESE 2010. [DOI: 10.1007/s11434-009-0388-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Zhai B, Li T, Chang F, Cao Q. Vast laminated diatom mat deposits from the west low-latitude Pacific Ocean in the last glacial period. Sci Bull (Beijing) 2009. [DOI: 10.1007/s11434-009-0447-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Pichevin LE, Reynolds BC, Ganeshram RS, Cacho I, Pena L, Keefe K, Ellam RM. Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean. Nature 2009; 459:1114-7. [PMID: 19553996 DOI: 10.1038/nature08101] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 04/23/2009] [Indexed: 11/09/2022]
Abstract
The modern Eastern Equatorial Pacific (EEP) Ocean is a large oceanic source of carbon to the atmosphere. Primary productivity over large areas of the EEP is limited by silicic acid and iron availability, and because of this constraint the organic carbon export to the deep ocean is unable to compensate for the outgassing of carbon dioxide that occurs through upwelling of deep waters. It has been suggested that the delivery of dust-borne iron to the glacial ocean could have increased primary productivity and enhanced deep-sea carbon export in this region, lowering atmospheric carbon dioxide concentrations during glacial periods. Such a role for the EEP is supported by higher organic carbon burial rates documented in underlying glacial sediments, but lower opal accumulation rates cast doubts on the importance of the EEP as an oceanic region for significant glacial carbon dioxide drawdown. Here we present a new silicon isotope record that suggests the paradoxical decline in opal accumulation rate in the glacial EEP results from a decrease in the silicon to carbon uptake ratio of diatoms under conditions of increased iron availability from enhanced dust input. Consequently, our study supports the idea of an invigorated biological pump in this region during the last glacial period that could have contributed to glacial carbon dioxide drawdown. Additionally, using evidence from silicon and nitrogen isotope changes, we infer that, in contrast to the modern situation, the biological productivity in this region is not constrained by the availability of iron, silicon and nitrogen during the glacial period. We hypothesize that an invigorated biological carbon dioxide pump constrained perhaps only by phosphorus limitation was a more common occurrence in low-latitude areas of the glacial ocean.
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Affiliation(s)
- L E Pichevin
- School of Geosciences, Grant Institute, University of Edinburgh, West Main Road, EH10 3JW, Edinburgh, UK.
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Sea surface temperature record from the north of the East China Sea since late Holocene. Sci Bull (Beijing) 2009. [DOI: 10.1007/s11434-009-0231-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Pulleniatina Minimum Event during the last deglaciation in the southern South China Sea. Sci Bull (Beijing) 2009. [DOI: 10.1007/s11434-009-0290-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Changes in sea surface temperature in western South China Sea over the past 450 ka. CHINESE SCIENCE BULLETIN 2009. [DOI: 10.1007/s11434-009-0083-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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An exceptionally strengthened East Asian summer monsoon event between 19.9 and 17.1 ka BP recorded in a Hulu stalagmite. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/s11430-009-0031-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Wilson RP, Vargas FH, Steinfurth A, Riordan P, Ropert-Coudert Y, Macdonald DW. WHAT GROUNDS SOME BIRDS FOR LIFE? MOVEMENT AND DIVING IN THE SEXUALLY DIMORPHIC GALÁPAGOS CORMORANT. ECOL MONOGR 2008. [DOI: 10.1890/07-0677.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Partin JW, Cobb KM, Adkins JF, Clark B, Fernandez DP. Millennial-scale trends in west Pacific warm pool hydrology since the Last Glacial Maximum. Nature 2007; 449:452-5. [PMID: 17898765 DOI: 10.1038/nature06164] [Citation(s) in RCA: 284] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Accepted: 08/08/2007] [Indexed: 11/09/2022]
Abstract
Models and palaeoclimate data suggest that the tropical Pacific climate system plays a key part in the mechanisms underlying orbital-scale and abrupt climate change. Atmospheric convection over the western tropical Pacific is a major source of heat and moisture to extratropical regions, and may therefore influence the global climate response to a variety of forcing factors. The response of tropical Pacific convection to changes in global climate boundary conditions, abrupt climate changes and radiative forcing remains uncertain, however. Here we present three absolutely dated oxygen isotope records from stalagmites in northern Borneo that reflect changes in west Pacific warm pool hydrology over the past 27,000 years. Our results suggest that convection over the western tropical Pacific weakened 18,000-20,000 years ago, as tropical Pacific and Antarctic temperatures began to rise during the early stages of deglaciation. Convective activity, as inferred from oxygen isotopes, reached a minimum during Heinrich event 1 (ref. 10), when the Atlantic meridional overturning circulation was weak, pointing to feedbacks between the strength of the overturning circulation and tropical Pacific hydrology. There is no evidence of the Younger Dryas event in the stalagmite records, however, suggesting that different mechanisms operated during these two abrupt deglacial climate events. During the Holocene epoch, convective activity appears to track changes in spring and autumn insolation, highlighting the sensitivity of tropical Pacific convection to external radiative forcing. Together, these findings demonstrate that the tropical Pacific hydrological cycle is sensitive to high-latitude climate processes in both hemispheres, as well as to external radiative forcing, and that it may have a central role in abrupt climate change events.
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Affiliation(s)
- Judson W Partin
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
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Marchant R, Mumbi C, Behera S, Yamagata T. The Indian Ocean dipole ? the unsung driver of climatic variability in East Africa. Afr J Ecol 2007. [DOI: 10.1111/j.1365-2028.2006.00707.x] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abram NJ, Gagan MK, Liu Z, Hantoro WS, McCulloch MT, Suwargadi BW. Seasonal characteristics of the Indian Ocean Dipole during the Holocene epoch. Nature 2007; 445:299-302. [PMID: 17230187 DOI: 10.1038/nature05477] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Accepted: 11/21/2006] [Indexed: 11/09/2022]
Abstract
The Indian Ocean Dipole (IOD)--an oscillatory mode of coupled ocean-atmosphere variability--causes climatic extremes and socio-economic hardship throughout the tropical Indian Ocean region. There is much debate about how the IOD interacts with the El Niño/Southern Oscillation (ENSO) and the Asian monsoon, and recent changes in the historic ENSO-monsoon relationship raise the possibility that the properties of the IOD may also be evolving. Improving our understanding of IOD events and their climatic impacts thus requires the development of records defining IOD activity in different climatic settings, including prehistoric times when ENSO and the Asian monsoon behaved differently from the present day. Here we use coral geochemical records from the equatorial eastern Indian Ocean to reconstruct surface-ocean cooling and drought during individual IOD events over the past approximately 6,500 years. We find that IOD events during the middle Holocene were characterized by a longer duration of strong surface ocean cooling, together with droughts that peaked later than those expected by El Niño forcing alone. Climate model simulations suggest that this enhanced cooling and drying was the result of strong cross-equatorial winds driven by the strengthened Asian monsoon of the middle Holocene. These IOD-monsoon connections imply that the socioeconomic impacts of projected future changes in Asian monsoon strength may extend throughout Australasia.
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Affiliation(s)
- Nerilie J Abram
- Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory 0200, Australia.
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Yancheva G, Nowaczyk NR, Mingram J, Dulski P, Schettler G, Negendank JFW, Liu J, Sigman DM, Peterson LC, Haug GH. Influence of the intertropical convergence zone on the East Asian monsoon. Nature 2007; 445:74-7. [PMID: 17203059 DOI: 10.1038/nature05431] [Citation(s) in RCA: 657] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Accepted: 11/06/2006] [Indexed: 11/09/2022]
Abstract
The Asian-Australian monsoon is an important component of the Earth's climate system that influences the societal and economic activity of roughly half the world's population. The past strength of the rain-bearing East Asian summer monsoon can be reconstructed with archives such as cave deposits, but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct. Here we present high-resolution records of the magnetic properties and the titanium content of the sediments of Lake Huguang Maar in coastal southeast China over the past 16,000 years, which we use as proxies for the strength of the winter monsoon winds. We find evidence for stronger winter monsoon winds before the Bølling-Allerød warming, during the Younger Dryas episode and during the middle and late Holocene, when cave stalagmites suggest weaker summer monsoons. We conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone. Similar migrations of the intertropical convergence zone have been observed in Central America for the period ad 700 to 900 (refs 4-6), suggesting global climatic changes at that time. From the coincidence in timing, we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the Tang dynasty in China and the Classic Maya in Central America.
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Affiliation(s)
- Gergana Yancheva
- GeoForschungsZentrum (GFZ), Section 3.3, Telegrafenberg, Potsdam D-14473, Germany
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Chapter Nineteen Elemental Proxies for Reconstructing Cenozoic Seawater Paleotemperatures from Calcareous Fossils. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s1572-5480(07)01024-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Kienast M, Kienast SS, Calvert SE, Eglinton TI, Mollenhauer G, François R, Mix AC. Eastern Pacific cooling and Atlantic overturning circulation during the last deglaciation. Nature 2006; 443:846-9. [PMID: 17051216 DOI: 10.1038/nature05222] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Accepted: 08/22/2006] [Indexed: 11/09/2022]
Abstract
Surface ocean conditions in the equatorial Pacific Ocean could hold the clue to whether millennial-scale global climate change during glacial times was initiated through tropical ocean-atmosphere feedbacks or by changes in the Atlantic thermohaline circulation. North Atlantic cold periods during Heinrich events and millennial-scale cold events (stadials) have been linked with climatic changes in the tropical Atlantic Ocean and South America, as well as the Indian and East Asian monsoon systems, but not with tropical Pacific sea surface temperatures. Here we present a high-resolution record of sea surface temperatures in the eastern tropical Pacific derived from alkenone unsaturation measurements. Our data show a temperature drop of approximately 1 degrees C, synchronous (within dating uncertainties) with the shutdown of the Atlantic meridional overturning circulation during Heinrich event 1, and a smaller temperature drop of approximately 0.5 degrees C synchronous with the smaller reduction in the overturning circulation during the Younger Dryas event. Both cold events coincide with maxima in surface ocean productivity as inferred from 230Th-normalized carbon burial fluxes, suggesting increased upwelling at the time. From the concurrence of equatorial Pacific cooling with the two North Atlantic cold periods during deglaciation, we conclude that these millennial-scale climate changes were probably driven by a reorganization of the oceans' thermohaline circulation, although possibly amplified by tropical ocean-atmosphere interaction as suggested before.
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Affiliation(s)
- Markus Kienast
- Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, B3H 4J1 Canada.
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Harrison ME, Chivers DJ. The orang-utan mating system and the unflanged male: A product of increased food stress during the late Miocene and Pliocene? J Hum Evol 2006; 52:275-93. [PMID: 17083968 DOI: 10.1016/j.jhevol.2006.09.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Revised: 08/18/2006] [Accepted: 09/04/2006] [Indexed: 10/24/2022]
Abstract
The orang-utan is unique among apes in having an unusually long male developmental period and two distinct adult male morphs (flanged and unflanged), which generally, but not exclusively, employ different reproductive strategies (call-and-wait vs. sneak-and-rape). Both morphs have recently been shown to have roughly similar levels of reproductive success in the one site where such a study has been conducted. This is in stark contrast to the unimale polygynous gorilla, in which dominant males sire almost all infants. Despite this, evidence on sexual dimorphism, life history, diet, and socioecology of extant and extinct apes, as well as the ontogeny, reproductive morphology, and physiology of extant apes, all indicate that the orang-utan's present-day mating system most likely evolved from a gorilla-like base, with one dominant male guarding a harem of females. The available evidence indicates that, due chiefly to the likely onset of the El Niño Southern Oscillation (generally regarded as the trigger for mast fruiting in dipterocarps) approximately 3-5Ma, southeast Asian forests would have begun to experience longer and more severe periods of low food availability. This change in food availability would have meant that full-time gregariousness was no longer energetically tolerable and, as a result, females dispersed more widely in search of food and adult/flanged males were no longer able to effectively guard a harem of females. A niche for a quiet, quick, opportunistic "sexual predator" (i.e., the unflanged male) then became available. This finding implies that, despite being anatomically quite chimpanzee-like, the ancestral hominoid probably had a social and mating system more similar to the gorilla than any other living ape.
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Affiliation(s)
- Mark E Harrison
- Wildlife Research Group, The Anatomy School, University of Cambridge, Downing Street, Cambridge, CB2 3DY, United Kingdom.
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Hong B, Lin Q, Hong Y. Interconnections between the Asian monsoon, ENSO, and high northern latitude climate during the Holocene. ACTA ACUST UNITED AC 2006. [DOI: 10.1007/s11434-006-2112-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
The Seychelles is a small island state in the western Indian Ocean that is vulnerable to the effects of climate change. This vulnerability led the Intergovernmental Panel on Climate Change (IPCC) in 2001 to express concern over the potential economic and social consequences that may be faced by small island states. Small island states should be prepared to adapt to such changes, especially in view of their dependence on natural resources, such as water and coral reefs, to meet basic human welfare needs. Analysis of long-term data for precipitation, air temperature, and sea-surface temperature indicated that changes are already observable in the Seychelles. The increase in dry spells that resulted in drought conditions in 1999 and the 1998 mass coral bleaching are indicative of the events that are likely to occur under future climate change. Pre-IPCC Third Assessment Report scenarios and the new SRES scenarios are compared for changes in precipitation and air surface temperature for the Seychelles. These intercomparisons indicate that the IS92 scenarios project a much warmer and wetter climate for the Seychelles than do the SRES scenarios. However, a wetter climate does not imply readily available water, but rather longer dry spells with more intense precipitation events. These observations will likely place enormous pressures on water-resources management in the Seychelles. Similarly, sea-surface temperature increases predicted by the HADCM3 model will likely trigger repeated coral-bleaching episodes, with possible coral extinctions within the Seychelles region by 2040. The cover of many coral reefs around the Seychelles have already changed, and the protection of coral-resilient areas is a critical adaptive option.
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Affiliation(s)
- Rolph Payet
- Policy and Planning Services Division, Ministry of the Environment and Natural Resources, Republic of Seychelles.
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Brown J, Simmonds I, Noone D. Modeling δ18O in tropical precipitation and the surface ocean for present-day climate. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2004jd005611] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Donders TH, Wagner F, Dilcher DL, Visscher H. Mid- to late-Holocene El Nino-Southern Oscillation dynamics reflected in the subtropical terrestrial realm. Proc Natl Acad Sci U S A 2005; 102:10904-8. [PMID: 16043705 PMCID: PMC1182467 DOI: 10.1073/pnas.0505015102] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
High resolution pollen analysis of mid- to late-Holocene peat deposits from southwest Florida reveals a stepwise increase in wetland vegetation that points to an increased precipitation-driven fresh water flow during the past 5,000 years. The tight coupling between winter precipitation patterns in Florida and the strength of the El Niño-Southern Oscillation (ENSO) strongly suggests that the paleo-hydrology record reflects changes in ENSO intensity. A terrestrial subtropical record outside the Indo Pacific Warm Pool both documents ecosystem response to the known onset of modern-day ENSO periodicities, between approximately 7,000 and 5,000 years B.P., and subsequent ENSO intensification after 3,500 years B.P. The observed increases in "wetness" are sustained by a gradual rise in relative sea level that prevents a return to drier vegetation through natural succession.
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Affiliation(s)
- Timme H Donders
- Department of Palaeoecology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands.
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Knüsel S. ENSO signals of the twentieth century in an ice core from Nevado Illimani, Bolivia. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jd005420] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Wagner T. El Niño induced anomalies in global data sets of total column precipitable water and cloud cover derived from GOME on ERS-2. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2005jd005972] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lamy F, Kaiser J, Ninnemann U, Hebbeln D, Arz HW, Stoner J. Antarctic Timing of Surface Water Changes off Chile and Patagonian Ice Sheet Response. Science 2004; 304:1959-62. [PMID: 15218147 DOI: 10.1126/science.1097863] [Citation(s) in RCA: 259] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Marine sediments from the Chilean continental margin are used to infer millennial-scale changes in southeast Pacific surface ocean water properties and Patagonian ice sheet extent since the last glacial period. Our data show a clear "Antarctic" timing of sea surface temperature changes, which appear systematically linked to meridional displacements in sea ice, westerly winds, and the circumpolar current system. Proxy data for ice sheet changes show a similar pattern as oceanographic variations offshore, but reveal a variable glacier-response time of up to approximately 1000 years, which may explain some of the current discrepancies among terrestrial records in southern South America.
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Affiliation(s)
- Frank Lamy
- GeoForschungsZentrum-Potsdam, Telegrafenberg, 14473 Potsdam, Germany.
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Corrège T, Gagan MK, Beck JW, Burr GS, Cabioch G, Le Cornec F. Interdecadal variation in the extent of South Pacific tropical waters during the Younger Dryas event. Nature 2004; 428:927-9. [PMID: 15118722 DOI: 10.1038/nature02506] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2003] [Accepted: 03/16/2004] [Indexed: 11/09/2022]
Abstract
During the Younger Dryas event, about 12,000 years ago, the Northern Hemisphere cooled by between 2 and 10 degrees C (refs 1, 2) whereas East Antarctica experienced warming. But the spatial signature of the event in the southern mid-latitudes and tropics is less well known, as records are sparse and inconclusive. Here we present high-resolution analyses of skeletal Sr/Ca and 18O/16O ratios for a giant fossil Diploastrea heliopora coral that was preserved in growth position on the raised reef terraces of Espiritu Santo Island, Vanuatu, in the southwestern tropical Pacific Ocean. Our data indicate that sea surface temperatures in Vanuatu were on average 4.5 +/- 1.3 degrees C cooler during the Younger Dryas event than today, with a significant interdecadal modulation. The amplified annual cycle of sea surface temperatures, relative to today, indicates that cooling was caused by the compression of tropical waters towards the Equator. The positive correlation in our record between the oxygen isotope ratios of sea water and sea surface temperatures suggests that the South Pacific convergence zone, which brings 18O-depleted precipitation to the area today, was not active during the Younger Dryas period.
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Affiliation(s)
- Thierry Corrège
- UR 055 Paléotropique, Institut de recherche pour le Développement, BP A5, Nouméa, New Caledonia.
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Affiliation(s)
- Yair Rosenthal
- Institute of Marine and Coastal Sciences and Department of Geology, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901, USA.
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Koutavas A, Lynch-Stieglitz J. Variability of the Marine ITCZ over the Eastern Pacific during the Past 30,000 Years. ADVANCES IN GLOBAL CHANGE RESEARCH 2004. [DOI: 10.1007/978-1-4020-2944-8_13] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Lea DW, Pak DK, Peterson LC, Hughen KA. Synchroneity of tropical and high-latitude Atlantic temperatures over the last glacial termination. Science 2003; 301:1361-4. [PMID: 12958356 DOI: 10.1126/science.1088470] [Citation(s) in RCA: 346] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A high-resolution western tropical Atlantic sea surface temperature (SST) record from the Cariaco Basin on the northern Venezuelan shelf, based on Mg/Ca values in surface-dwelling planktonic foraminifera, reveals that changes in SST over the last glacial termination are synchronous, within +/-30 to +/-90 years, with the Greenland Ice Sheet Project 2 air temperature proxy record and atmospheric methane record. The most prominent deglacial event in the Cariaco record occurred during the Younger Dryas time interval, when SSTs dropped by 3 degrees to 4 degrees C. A rapid southward shift in the atmospheric intertropical convergence zone could account for the synchroneity of tropical temperature, atmospheric methane, and high-latitude changes during the Younger Dryas.
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Affiliation(s)
- David W Lea
- Department of Geological Sciences and Marine Science Institute, University of California, Santa Barbara, CA 93106, USA.
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Burns SJ, Fleitmann D, Matter A, Kramers J, Al-Subbary AA. Indian Ocean climate and an absolute chronology over Dansgaard/Oeschger events 9 to 13. Science 2003; 301:1365-7. [PMID: 12958357 DOI: 10.1126/science.1086227] [Citation(s) in RCA: 245] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Oxygen-isotope ratios of a stalagmite from Socotra Island in the Indian Ocean provide a record of changes in monsoon precipitation and climate for the time period from 42 to 55 thousand years before the present. The pattern of precipitation bears a striking resemblance to the oxygen-isotope record from Greenland ice cores, with increased tropical precipitation associated with warm periods in the high northern latitudes. The largest change, at the onset of interstadial 12, occurred very rapidly, in about 25 years. The chronology of the events found in our record requires a reevaluation of previously published time scales for climate events during this period.
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Affiliation(s)
- Stephen J Burns
- Department of Geosciences, University of Massachusetts, Amherst MA, USA.
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