1
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Wharton JH, Renoult M, Gebbie G, Keigwin LD, Marchitto TM, Maslin MA, Oppo DW, Thornalley DJR. Deeper and stronger North Atlantic Gyre during the Last Glacial Maximum. Nature 2024:10.1038/s41586-024-07655-y. [PMID: 38987602 DOI: 10.1038/s41586-024-07655-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 05/31/2024] [Indexed: 07/12/2024]
Abstract
Subtropical gyre (STG) depth and strength are controlled by wind stress curl and surface buoyancy forcing1,2. Modern hydrographic data reveal that the STG extends to a depth of about 1 km in the Northwest Atlantic, with its maximum depth defined by the base of the subtropical thermocline. Despite the likelihood of greater wind stress curl and surface buoyancy loss during the Last Glacial Maximum (LGM)3, previous work suggests minimal change in the depth of the glacial STG4. Here we show a sharp glacial water mass boundary between 33° N and 36° N extending down to between 2.0 and 2.5 km-approximately 1 km deeper than today. Our findings arise from benthic foraminiferal δ18O profiles from sediment cores in two depth transects at Cape Hatteras (36-39° N) and Blake Outer Ridge (29-34° N) in the Northwest Atlantic. This result suggests that the STG, including the Gulf Stream, was deeper and stronger during the LGM than at present, which we attribute to increased glacial wind stress curl, as supported by climate model simulations, as well as greater glacial production of denser subtropical mode waters (STMWs). Our data suggest (1) that subtropical waters probably contributed to the geochemical signature of what is conventionally identified as Glacial North Atlantic Intermediate Water (GNAIW)5-7 and (2) the STG helped sustain continued buoyancy loss, water mass conversion and northwards meridional heat transport (MHT) in the glacial North Atlantic.
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Affiliation(s)
- Jack H Wharton
- Department of Geography, University College London, London, UK.
| | - Martin Renoult
- Department of Geological Sciences, Stockholm University, Stockholm, Sweden
| | | | | | - Thomas M Marchitto
- Department of Geological Sciences and INSTAAR, University of Colorado, Boulder, CO, USA
| | - Mark A Maslin
- Department of Geography, University College London, London, UK
| | - Delia W Oppo
- Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - David J R Thornalley
- Department of Geography, University College London, London, UK
- Woods Hole Oceanographic Institution, Woods Hole, MA, USA
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2
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Kawamura K, Oyabu I. Two decades of deep ice cores from Antarctica. Nature 2024; 630:825-827. [PMID: 38858549 DOI: 10.1038/d41586-024-01507-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2024]
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3
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Clark PU, Shakun JD, Rosenthal Y, Köhler P, Bartlein PJ. Global and regional temperature change over the past 4.5 million years. Science 2024; 383:884-890. [PMID: 38386742 DOI: 10.1126/science.adi1908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2023] [Accepted: 01/16/2024] [Indexed: 02/24/2024]
Abstract
Much of our understanding of Cenozoic climate is based on the record of δ18O measured in benthic foraminifera. However, this measurement reflects a combined signal of global temperature and sea level, thus preventing a clear understanding of the interactions and feedbacks of the climate system in causing global temperature change. Our new reconstruction of temperature change over the past 4.5 million years includes two phases of long-term cooling, with the second phase of accelerated cooling during the Middle Pleistocene Transition (1.5 to 0.9 million years ago) being accompanied by a transition from dominant 41,000-year low-amplitude periodicity to dominant 100,000-year high-amplitude periodicity. Changes in the rates of long-term cooling and variability are consistent with changes in the carbon cycle driven initially by geologic processes, followed by additional changes in the Southern Ocean carbon cycle.
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Affiliation(s)
- Peter U Clark
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
- School of Geography and Environmental Sciences, University of Ulster, Coleraine BT52 1SA, Northern Ireland, UK
| | - Jeremy D Shakun
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA
| | - Yair Rosenthal
- Department of Marine and Coastal Science, Rutgers The State University, New Brunswick, NJ 08901, USA
- Department of Earth and Planetary Sciences, Rutgers The State University, New Brunswick, NJ 08901, USA
| | - Peter Köhler
- Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany
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4
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Wang Y, Costa KM, Lu W, Hines SKV, Nielsen SG. Global oceanic oxygenation controlled by the Southern Ocean through the last deglaciation. SCIENCE ADVANCES 2024; 10:eadk2506. [PMID: 38241365 PMCID: PMC10798564 DOI: 10.1126/sciadv.adk2506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 12/19/2023] [Indexed: 01/21/2024]
Abstract
Ocean dissolved oxygen (DO) can provide insights on how the marine carbon cycle affects global climate change. However, the net global DO change and the controlling mechanisms remain uncertain through the last deglaciation. Here, we present a globally integrated DO reconstruction using thallium isotopes, corroborating lower global DO during the Last Glacial Maximum [19 to 23 thousand years before the present (ka B.P.)] relative to the Holocene. During the deglaciation, we reveal reoxygenation in the Heinrich Stadial 1 (~14.7 to 18 ka B.P.) and the Younger Dryas (11.7 to 12.9 ka B.P.), with deoxygenation during the Bølling-Allerød (12.9 to 14.7 ka B.P.). The deglacial DO changes were decoupled from North Atlantic Deep Water formation rates and imply that Southern Ocean ventilation controlled ocean oxygen. The coherence between global DO and atmospheric CO2 on millennial timescales highlights the Southern Ocean's role in deglacial atmospheric CO2 rise.
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Affiliation(s)
- Yi Wang
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- NIRVANA Laboratories, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118, USA
| | - Kassandra M. Costa
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Wanyi Lu
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Sophia K. V. Hines
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Sune G. Nielsen
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- NIRVANA Laboratories, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- Centre de Recherches Pétrographiques et Géochimiques, CNRS, Université de Lorraine, 15 rue Notre Dame des Pauvres, 54501 Vandoeuvre lès Nancy, France
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5
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Li T, Robinson LF, MacGilchrist GA, Chen T, Stewart JA, Burke A, Wang M, Li G, Chen J, Rae JWB. Enhanced subglacial discharge from Antarctica during meltwater pulse 1A. Nat Commun 2023; 14:7327. [PMID: 37957152 PMCID: PMC10643554 DOI: 10.1038/s41467-023-42974-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 10/27/2023] [Indexed: 11/15/2023] Open
Abstract
Subglacial discharge from the Antarctic Ice Sheet (AIS) likely played a crucial role in the loss of the ice sheet and the subsequent rise in sea level during the last deglaciation. However, no direct proxy is currently available to document subglacial discharge from the AIS, which leaves significant gaps in our understanding of the complex interactions between subglacial discharge and ice-sheet stability. Here we present deep-sea coral 234U/238U records from the Drake Passage in the Southern Ocean to track subglacial discharge from the AIS. Our findings reveal distinctively higher seawater 234U/238U values from 15,400 to 14,000 years ago, corresponding to the period of the highest iceberg-rafted debris flux and the occurrence of the meltwater pulse 1A event. This correlation suggests a causal link between enhanced subglacial discharge, synchronous retreat of the AIS, and the rapid rise in sea levels. The enhanced subglacial discharge and subsequent AIS retreat appear to have been preconditioned by a stronger and warmer Circumpolar Deep Water, thus underscoring the critical role of oceanic heat in driving major ice-sheet retreat.
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Affiliation(s)
- Tao Li
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China.
- School of Earth Sciences, University of Bristol, Bristol, UK.
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China.
| | - Laura F Robinson
- School of Earth Sciences, University of Bristol, Bristol, UK
- Department of Environment and Geography, University of York, York, UK
| | - Graeme A MacGilchrist
- Program in Atmospheric and Oceanic Science, Princeton University, Princeton, NJ, USA
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Tianyu Chen
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | | | - Andrea Burke
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Maoyu Wang
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | - Gaojun Li
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | - Jun Chen
- Department of Earth and Planetary Sciences, Nanjing University, Nanjing, China
| | - James W B Rae
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
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6
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Liu Z, Bao Y, Thompson LG, Mosley-Thompson E, Tabor C, Zhang GJ, Yan M, Lofverstrom M, Montanez I, Oster J. Tropical mountain ice core δ 18O: A Goldilocks indicator for global temperature change. SCIENCE ADVANCES 2023; 9:eadi6725. [PMID: 37939192 PMCID: PMC10631737 DOI: 10.1126/sciadv.adi6725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 10/12/2023] [Indexed: 11/10/2023]
Abstract
Very high tropical alpine ice cores provide a distinct paleoclimate record for climate changes in the middle and upper troposphere. However, the climatic interpretation of a key proxy, the stable water oxygen isotopic ratio in ice cores (δ18Oice), remains an outstanding problem. Here, combining proxy records with climate models, modern satellite measurements, and radiative-convective equilibrium theory, we show that the tropical δ18Oice is an indicator of the temperature of the middle and upper troposphere, with a glacial cooling of -7.35° ± 1.1°C (66% CI). Moreover, it severs as a "Goldilocks-type" indicator of global mean surface temperature change, providing the first estimate of glacial stage cooling that is independent of marine proxies as -5.9° ± 1.2°C. Combined with all estimations available gives the maximum likelihood estimate of glacial cooling as -5.85° ± 0.51°C.
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Affiliation(s)
- Zhengyu Liu
- Department of Geography, Ohio State University, Columbus, OH, USA
- School of Geography Science, Nanjing Normal University, Nanjing, China
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
| | - Yuntao Bao
- Department of Geography, Ohio State University, Columbus, OH, USA
| | - Lonnie G. Thompson
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
- School of Earth Sciences, Ohio State University, Columbus, OH, USA
| | - Ellen Mosley-Thompson
- Department of Geography, Ohio State University, Columbus, OH, USA
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
| | - Clay Tabor
- Department of Earth Sciences, University of Connecticut, Storrs, CT, USA
| | - Guang J. Zhang
- Scripps Institute of Oceanography, University of California, San Diego, San Diego, CA, USA
| | - Mi Yan
- School of Geography Science, Nanjing Normal University, Nanjing, China
| | | | - Isabel Montanez
- Department of Earth and Planetary Sciences, University of California–Davis, Davis, CA, USA
| | - Jessica Oster
- Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN, USA
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7
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Su F, Fan R, Yan F, Meadows M, Lyne V, Hu P, Song X, Zhang T, Liu Z, Zhou C, Pei T, Yang X, Du Y, Wei Z, Wang F, Qi Y, Chai F. Widespread global disparities between modelled and observed mid-depth ocean currents. Nat Commun 2023; 14:2089. [PMID: 37045863 PMCID: PMC10097707 DOI: 10.1038/s41467-023-37841-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 03/31/2023] [Indexed: 04/14/2023] Open
Abstract
The mid-depth ocean circulation is critically linked to actual changes in the long-term global climate system. However, in the past few decades, predictions based on ocean circulation models highlight the lack of data, knowledge, and long-term implications in climate change assessment. Here, using 842,421 observations produced by Argo floats from 2001-2020, and Lagrangian simulations, we show that only 3.8% of the mid-depth oceans, including part of the equatorial Pacific Ocean and the Antarctic Circumpolar Current, can be regarded as accurately modelled, while other regions exhibit significant underestimations in mean current velocity. Knowledge of ocean circulation is generally more complete in the low-latitude oceans but is especially poor in high latitude regions. Accordingly, we propose improvements in forecasting, model representation of stochasticity, and enhancement of observations of ocean currents. The study demonstrates that knowledge and model representations of global circulation are substantially compromised by inaccuracies of significant magnitude and direction, with important implications for modelled predictions of currents, temperature, carbon dioxide sequestration, and sea-level rise trends.
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Affiliation(s)
- Fenzhen Su
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China.
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China.
- School of Geography and Ocean Sciences, Nanjing University, Nanjing, 210093, China.
- Collaborative Innovation Center for the South China Sea Studies, Nanjing University, Nanjing, 210023, China.
| | - Rong Fan
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Fengqin Yan
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Michael Meadows
- School of Geography and Ocean Sciences, Nanjing University, Nanjing, 210093, China
- Department of Environmental & Geographical Science, University of Cape Town, Rondebosch, 7701, South Africa
- College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China
| | - Vincent Lyne
- IMAS-Hobart, University of Tasmania, Tasmania, 7004, Australia
| | - Po Hu
- Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China
| | - Xiangzhou Song
- College of Oceanography, Hohai University, Nanjing, 211100, China
| | - Tianyu Zhang
- College of Oceanography and Meteorology, Guangdong Ocean University, Zhanjiang, 524088, China
| | - Zenghong Liu
- State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China
| | - Chenghu Zhou
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Tao Pei
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaomei Yang
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yunyan Du
- State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zexun Wei
- First Institute of Oceanography, and Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao, 266061, China
| | - Fan Wang
- Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China
| | - Yiquan Qi
- College of Oceanography, Hohai University, Nanjing, 211100, China
| | - Fei Chai
- State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China
- College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, China
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8
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Pöppelmeier F, Jeltsch-Thömmes A, Lippold J, Joos F, Stocker TF. Multi-proxy constraints on Atlantic circulation dynamics since the last ice age. NATURE GEOSCIENCE 2023; 16:349-356. [PMID: 37064010 PMCID: PMC10089918 DOI: 10.1038/s41561-023-01140-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 01/27/2023] [Indexed: 06/19/2023]
Abstract
Uncertainties persist in the understanding of the Atlantic meridional overturning circulation and its response to external perturbations such as freshwater or radiative forcing. Abrupt reduction of the Atlantic circulation is considered a climate tipping point that may have been crossed when Earth's climate was propelled out of the last ice age. However, the evolution of the circulation since the Last Glacial Maximum (22-18 thousand years ago) remains insufficiently constrained due to model and proxy limitations. Here we leverage information from both a compilation of proxy records that track various aspects of the circulation and climate model simulations to constrain the Atlantic circulation over the past 20,000 years. We find a coherent picture of a shallow and weak Atlantic overturning circulation during the Last Glacial Maximum that reconciles apparently conflicting proxy evidence. Model-data comparison of the last deglaciation-starting from this new, multiple constrained glacial state-indicates a muted response during Heinrich Stadial 1 and that water mass geometry did not fully adjust to the strong reduction in overturning circulation during the comparably short Younger Dryas period. This demonstrates that the relationship between freshwater forcing and Atlantic overturning strength is strongly dependent on the climatic and oceanic background state.
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Affiliation(s)
- Frerk Pöppelmeier
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
| | - Aurich Jeltsch-Thömmes
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
| | - Jörg Lippold
- Institute of Earth Sciences, Heidelberg University, Heidelberg, Germany
| | - Fortunat Joos
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
| | - Thomas F Stocker
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
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9
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Kaufman DS, Broadman E. Revisiting the Holocene global temperature conundrum. Nature 2023; 614:425-435. [PMID: 36792734 DOI: 10.1038/s41586-022-05536-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 11/07/2022] [Indexed: 02/17/2023]
Abstract
Recent global temperature reconstructions for the current interglacial period (the Holocene, beginning 11,700 years ago) have generated contrasting trends. This Review examines evidence from indicators and drivers of global change, as inferred from proxy records and simulated by climate models, to evaluate whether anthropogenic global warming was preceded by a long-term warming trend or by global cooling. Multimillennial-scale cooling before industrialization requires extra climate forcing and major climate feedbacks that are not well represented in most climate models at present. Conversely, global warming before industrialization challenges proxy-based reconstructions of past climate. The resolution of this conundrum has implications for contextualizing post-industrial warming and for understanding climate sensitivity to several forcings and their attendant feedbacks, including greenhouse gases. From a large variety of available evidence, we find support for a relatively mild millennial-scale global thermal maximum during the mid-Holocene, but more research is needed to firmly resolve the conundrum and to advance our understanding of slow-moving climate variability.
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Affiliation(s)
- Darrell S Kaufman
- School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ, USA.
| | - Ellie Broadman
- School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ, USA
- Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ, USA
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10
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Evidence for late-glacial oceanic carbon redistribution and discharge from the Pacific Southern Ocean. Nat Commun 2022; 13:6250. [PMID: 36369161 PMCID: PMC9652385 DOI: 10.1038/s41467-022-33753-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 09/30/2022] [Indexed: 11/13/2022] Open
Abstract
Southern Ocean deep-water circulation plays a vital role in the global carbon cycle. On geological time scales, upwelling along the Chilean margin likely contributed to the deglacial atmospheric carbon dioxide rise, but little quantitative evidence exists of carbon storage. Here, we develop an X-ray Micro-Computer-Tomography method to assess foraminiferal test dissolution as proxy for paleo-carbonate ion concentrations ([CO32-]). Our subantarctic Southeast Pacific sediment core depth transect shows significant deep-water [CO32-] variations during the Last Glacial Maximum and Deglaciation (10-22 ka BP). We provide evidence for an increase in [CO32-] during the early-deglacial period (15-19 ka BP) in Lower Circumpolar Deepwater. The export of such low-carbon deep-water from the Pacific to the Atlantic contributed to significantly lowered carbon storage within the Southern Ocean, highlighting the importance of a dynamic Pacific-Southern Ocean deep-water reconfiguration for shaping late-glacial oceanic carbon storage, and subsequent deglacial oceanic-atmospheric CO2 transfer.
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11
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Jian Z, Wang Y, Dang H, Mohtadi M, Rosenthal Y, Lea DW, Liu Z, Jin H, Ye L, Kuhnt W, Wang X. Warm pool ocean heat content regulates ocean-continent moisture transport. Nature 2022; 612:92-99. [PMID: 36261525 DOI: 10.1038/s41586-022-05302-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 08/31/2022] [Indexed: 11/09/2022]
Abstract
The Indo-Pacific Warm Pool (IPWP) exerts a dominant role in global climate by releasing huge amounts of water vapour and latent heat to the atmosphere and modulating upper ocean heat content (OHC), which has been implicated in modern climate change1. The long-term variations of IPWP OHC and their effect on monsoonal hydroclimate are, however, not fully explored. Here, by combining geochemical proxies and transient climate simulations, we show that changes of IPWP upper (0-200 m) OHC over the past 360,000 years exhibit dominant precession and weaker obliquity cycles and follow changes in meridional insolation gradients, and that only 30%-40% of the deglacial increases are related to changes in ice volume. On the precessional band, higher upper OHC correlates with oxygen isotope enrichments in IPWP surface water and concomitant depletion in East Asian precipitation as recorded in Chinese speleothems. Using an isotope-enabled air-sea coupled model, we suggest that on precessional timescales, variations in IPWP upper OHC, more than surface temperature, act to amplify the ocean-continent hydrological cycle via the convergence of moisture and latent heat. From an energetic viewpoint, the coupling of upper OHC and monsoon variations, both coordinated by insolation changes on orbital timescales, is critical for regulating the global hydroclimate.
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Affiliation(s)
- Zhimin Jian
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China.
| | - Yue Wang
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China.
| | - Haowen Dang
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China.
| | - Mahyar Mohtadi
- MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Yair Rosenthal
- Department of Marine and Coastal Science, Rutgers University, New Brunswick, NJ, USA.,Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ, USA
| | - David W Lea
- Department of Earth Science, University of California, Santa Barbara, CA, USA
| | - Zhongfang Liu
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
| | - Haiyan Jin
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
| | - Liming Ye
- Second Institute of Oceanography, Ministry of Natural Resource, Hangzhou, China
| | - Wolfgang Kuhnt
- Institute of Geosciences, Christian-Albrechts-Universität, Kiel, Germany
| | - Xingxing Wang
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
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12
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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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13
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Multiple carbon cycle mechanisms associated with the glaciation of Marine Isotope Stage 4. Nat Commun 2022; 13:5443. [PMID: 36114188 PMCID: PMC9481522 DOI: 10.1038/s41467-022-33166-3] [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: 12/23/2021] [Accepted: 09/02/2022] [Indexed: 12/01/2022] Open
Abstract
Here we use high-precision carbon isotope data (δ13C-CO2) to show atmospheric CO2 during Marine Isotope Stage 4 (MIS 4, ~70.5-59 ka) was controlled by a succession of millennial-scale processes. Enriched δ13C-CO2 during peak glaciation suggests increased ocean carbon storage. Variations in δ13C-CO2 in early MIS 4 suggest multiple processes were active during CO2 drawdown, potentially including decreased land carbon and decreased Southern Ocean air-sea gas exchange superposed on increased ocean carbon storage. CO2 remained low during MIS 4 while δ13C-CO2 fluctuations suggest changes in Southern Ocean and North Atlantic air-sea gas exchange. A 7 ppm increase in CO2 at the onset of Dansgaard-Oeschger event 19 (72.1 ka) and 27 ppm increase in CO2 during late MIS 4 (Heinrich Stadial 6, ~63.5-60 ka) involved additions of isotopically light carbon to the atmosphere. The terrestrial biosphere and Southern Ocean air-sea gas exchange are possible sources, with the latter event also involving decreased ocean carbon storage. Summary for general audience: We used carbon stable isotope data from an Antarctic ice core to evaluate which mechanisms caused changes in atmospheric carbon dioxide 74-59 thousand years ago, including a ~40 ppm decrease at the beginning of the last ice age.
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14
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Løland MH, Krüger Y, Fernandez A, Buckingham F, Carolin SA, Sodemann H, Adkins JF, Cobb KM, Meckler AN. Evolution of tropical land temperature across the last glacial termination. Nat Commun 2022; 13:5158. [PMID: 36055993 PMCID: PMC9440061 DOI: 10.1038/s41467-022-32712-3] [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: 02/16/2022] [Accepted: 08/10/2022] [Indexed: 11/23/2022] Open
Abstract
The tropical West Pacific hosts the warmest part of the surface ocean and has a considerable impact on the global climate system. Reconstructions of past temperature in this region can elucidate climate connections between the tropics and poles and the sensitivity of tropical temperature to greenhouse forcing. However, existing data are equivocal and reliable information from terrestrial archives is particularly sparse. Here we constrain the magnitude and timing of land temperature change in the tropical West Pacific across the last deglaciation using an exceptionally precise paleothermometer applied to a well-dated stalagmite from Northern Borneo. We show that the cave temperature increased by 4.4 ± 0.3 °C (2 SEM) from the Last Glacial Maximum to the Holocene, amounting to 3.6 ± 0.3 °C (2 SEM) when correcting for sea-level induced cave altitude change. The warming closely follows atmospheric CO2 and Southern Hemisphere warming. This contrasts with hydroclimate, as reflected by drip water δ18O, which responds to Northern Hemisphere cooling events in the form of prominent drying, while temperature was rising. Our results thus show a close response of tropical temperature to greenhouse forcing, independent of shifts in the tropical circulation patterns. Ancient drip water in a Borneo stalagmite reveals a strong land temperature rise across the last glacial termination in close correspondence with atmospheric CO2, and an intriguing decoupling between tropical temperature and hydroclimate.
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Affiliation(s)
- M H Løland
- Department of Earth Sciences, University of Bergen, Bergen, 5007, Norway. .,Bjerknes Centre for Climate Research, Bergen, 5007, Norway.
| | - Y Krüger
- Department of Earth Sciences, University of Bergen, Bergen, 5007, Norway
| | - A Fernandez
- Andalusian Institute of Earth Sciences, CSIC-University of Granada, Granada, Spain
| | - F Buckingham
- Department of Earth Sciences, University of Oxford, Oxford, UK
| | - S A Carolin
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - H Sodemann
- Bjerknes Centre for Climate Research, Bergen, 5007, Norway.,Geophysical Institute, University of Bergen, Bergen, 5007, Norway
| | - J F Adkins
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - K M Cobb
- Department of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - A N Meckler
- Department of Earth Sciences, University of Bergen, Bergen, 5007, Norway.,Bjerknes Centre for Climate Research, Bergen, 5007, Norway
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15
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Reply to: Non-trivial role of internal climate feedback on interglacial temperature evolution. Nature 2021; 600:E4-E6. [PMID: 34853451 DOI: 10.1038/s41586-021-03931-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Obase T, Abe-Ouchi A, Saito F. Abrupt climate changes in the last two deglaciations simulated with different Northern ice sheet discharge and insolation. Sci Rep 2021; 11:22359. [PMID: 34824287 PMCID: PMC8616927 DOI: 10.1038/s41598-021-01651-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 10/21/2021] [Indexed: 11/09/2022] Open
Abstract
There were significant differences between the last two deglaciations, particularly in Atlantic Meridional Overturning Circulation (AMOC) and Antarctic warming in the deglaciations and the following interglacials. Here, we present transient simulations of deglaciation using a coupled atmosphere–ocean general circulation model for the last two deglaciations focusing on the impact of ice sheet discharge on climate changes associated with the AMOC in the first part, and the sensitivity studies using a Northern Hemisphere ice sheet model in the second part. We show that a set of abrupt climate changes of the last deglaciation, including Bolling–Allerod warming, the Younger Dryas, and onset of the Holocene were simulated with gradual changes of both ice sheet discharge and radiative forcing. On the other hand, penultimate deglaciation, with the abrupt climate change only at the beginning of the last interglacial was simulated when the ice sheet discharge was greater than in the last deglaciation by a factor of 1.5. The results, together with Northern Hemisphere ice sheet model experiments suggest the importance of the transient climate and AMOC responses to the different orbital forcing conditions of the last two deglaciations, through the mechanisms of mass loss of the Northern Hemisphere ice sheet and meltwater influx to the ocean.
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Affiliation(s)
- Takashi Obase
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8568, Japan.
| | - Ayako Abe-Ouchi
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8568, Japan.,National Institute of Polar Research, Tachikawa, Japan
| | - Fuyuki Saito
- Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
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17
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Globally resolved surface temperatures since the Last Glacial Maximum. Nature 2021; 599:239-244. [PMID: 34759364 DOI: 10.1038/s41586-021-03984-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 09/01/2021] [Indexed: 11/08/2022]
Abstract
Climate changes across the past 24,000 years provide key insights into Earth system responses to external forcing. Climate model simulations1,2 and proxy data3-8 have independently allowed for study of this crucial interval; however, they have at times yielded disparate conclusions. Here, we leverage both types of information using paleoclimate data assimilation9,10 to produce the first proxy-constrained, full-field reanalysis of surface temperature change spanning the Last Glacial Maximum to present at 200-year resolution. We demonstrate that temperature variability across the past 24 thousand years was linked to two primary climatic mechanisms: radiative forcing from ice sheets and greenhouse gases; and a superposition of changes in the ocean overturning circulation and seasonal insolation. In contrast with previous proxy-based reconstructions6,7 our results show that global mean temperature has slightly but steadily warmed, by ~0.5 °C, since the early Holocene (around 9 thousand years ago). When compared with recent temperature changes11, our reanalysis indicates that both the rate and magnitude of modern warming are unusual relative to the changes of the past 24 thousand years.
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18
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Rohling EJ, Yu J, Heslop D, Foster GL, Opdyke B, Roberts AP. Sea level and deep-sea temperature reconstructions suggest quasi-stable states and critical transitions over the past 40 million years. SCIENCE ADVANCES 2021; 7:7/26/eabf5326. [PMID: 34172440 PMCID: PMC8232915 DOI: 10.1126/sciadv.abf5326] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 05/12/2021] [Indexed: 06/13/2023]
Abstract
Sea level and deep-sea temperature variations are key indicators of global climate changes. For continuous records over millions of years, deep-sea carbonate microfossil-based δ18O (δc) records are indispensable because they reflect changes in both deep-sea temperature and seawater δ18O (δw); the latter are related to ice volume and, thus, to sea level changes. Deep-sea temperature is usually resolved using elemental ratios in the same benthic microfossil shells used for δc, with linear scaling of residual δw to sea level changes. Uncertainties are large and the linear-scaling assumption remains untested. Here, we present a new process-based approach to assess relationships between changes in sea level, mean ice sheet δ18O, and both deep-sea δw and temperature and find distinct nonlinearity between sea level and δw changes. Application to δc records over the past 40 million years suggests that Earth's climate system has complex dynamical behavior, with threshold-like adjustments (critical transitions) that separate quasi-stable deep-sea temperature and ice-volume states.
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Affiliation(s)
- Eelco J Rohling
- Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia.
- School of Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton SO14 3ZH, UK
| | - Jimin Yu
- Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia
- Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China
| | - David Heslop
- Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia
| | - Gavin L Foster
- School of Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton SO14 3ZH, UK
| | - Bradley Opdyke
- Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia
| | - Andrew P Roberts
- Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia
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19
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Widespread six degrees Celsius cooling on land during the Last Glacial Maximum. Nature 2021; 593:228-232. [PMID: 33981051 DOI: 10.1038/s41586-021-03467-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 03/17/2021] [Indexed: 02/03/2023]
Abstract
The magnitude of global cooling during the Last Glacial Maximum (LGM, the coldest multimillennial interval of the last glacial period) is an important constraint for evaluating estimates of Earth's climate sensitivity1,2. Reliable LGM temperatures come from high-latitude ice cores3,4, but substantial disagreement exists between proxy records in the low latitudes1,5-8, where quantitative low-elevation records on land are scarce. Filling this data gap, noble gases in ancient groundwater record past land surface temperatures through a direct physical relationship that is rooted in their temperature-dependent solubility in water9,10. Dissolved noble gases are suitable tracers of LGM temperature because of their complete insensitivity to biological and chemical processes and the ubiquity of LGM-aged groundwater around the globe11,12. However, although several individual noble gas studies have found substantial tropical LGM cooling13-16, they have used different methodologies and provide limited spatial coverage. Here we use noble gases in groundwater to show that the low-altitude, low-to-mid-latitude land surface (45 degrees south to 35 degrees north) cooled by 5.8 ± 0.6 degrees Celsius (mean ± 95% confidence interval) during the LGM. Our analysis includes four decades of groundwater noble gas data from six continents, along with new records from the tropics, all of which were interpreted using the same physical framework. Our land-based result broadly supports a recent reconstruction based on marine proxy data assimilation1 that suggested greater climate sensitivity than previous estimates5-7.
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20
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Gebbie G. Combining Modern and Paleoceanographic Perspectives on Ocean Heat Uptake. ANNUAL REVIEW OF MARINE SCIENCE 2021; 13:255-281. [PMID: 32928022 DOI: 10.1146/annurev-marine-010419-010844] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Monitoring Earth's energy imbalance requires monitoring changes in the heat content of the ocean. Recent observational estimates indicate that ocean heat uptake is accelerating in the twenty-first century. Examination of estimates of ocean heat uptake over the industrial era, the Common Era of the last 2,000 years, and the period since the Last Glacial Maximum, 20,000 years ago, permits a wide perspective on modern-day warming rates. In addition, this longer-term focus illustrates how the dynamics of the deep ocean and the cryosphere were active in the past and are still active today. The large climatic shifts that started with the melting of the great ice sheets have involved significant ocean heat uptake that was sustained over centuries and millennia, and modern-ocean heat content changes are small by comparison.
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Affiliation(s)
- Geoffrey Gebbie
- Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA;
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21
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Cephalopods habitat and trophic ecology: historical data using snares penguin as biological sampler. Polar Biol 2021. [DOI: 10.1007/s00300-020-02776-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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22
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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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23
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Tierney JE, Zhu J, King J, Malevich SB, Hakim GJ, Poulsen CJ. Glacial cooling and climate sensitivity revisited. Nature 2020; 584:569-573. [DOI: 10.1038/s41586-020-2617-x] [Citation(s) in RCA: 108] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 06/15/2020] [Indexed: 01/25/2023]
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24
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Galbraith ED, Skinner LC. The Biological Pump During the Last Glacial Maximum. ANNUAL REVIEW OF MARINE SCIENCE 2020; 12:559-586. [PMID: 31899673 DOI: 10.1146/annurev-marine-010419-010906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Much of the global cooling during ice ages arose from changes in ocean carbon storage that lowered atmospheric CO2. A slew of mechanisms, both physical and biological, have been proposed as key drivers of these changes. Here we discuss the current understanding of these mechanisms with a focus on how they altered the theoretically defined soft-tissue and biological disequilibrium carbon storage at the peak of the last ice age. Observations and models indicate a role for Antarctic sea ice through its influence on ocean circulation patterns, but other mechanisms, including changes in biological processes, must have been important as well, and may have been coordinated through links with global air temperature. Further research is required to better quantify the contributions of the various mechanisms, and there remains great potential to use the Last Glacial Maximum and the ensuing global warming as natural experiments from which to learn about climate-driven changes in the marine ecosystem.
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Affiliation(s)
- Eric D Galbraith
- Department of Earth and Planetary Sciences, McGill University, Montreal H3A 0E8, Canada;
- Institut de Ciència i Tecnologia Ambientals (ICTA-UAB), Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
| | - Luke C Skinner
- Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom;
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25
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Two-million-year-old snapshots of atmospheric gases from Antarctic ice. Nature 2019; 574:663-666. [PMID: 31666720 DOI: 10.1038/s41586-019-1692-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 08/02/2019] [Indexed: 11/09/2022]
Abstract
Over the past eight hundred thousand years, glacial-interglacial cycles oscillated with a period of one hundred thousand years ('100k world'1). Ice core and ocean sediment data have shown that atmospheric carbon dioxide, Antarctic temperature, deep ocean temperature, and global ice volume correlated strongly with each other in the 100k world2-6. Between about 2.8 and 1.2 million years ago, glacial cycles were smaller in magnitude and shorter in duration ('40k world'7). Proxy data from deep-sea sediments suggest that the variability of atmospheric carbon dioxide in the 40k world was also lower than in the 100k world8-10, but we do not have direct observations of atmospheric greenhouse gases from this period. Here we report the recovery of stratigraphically discontinuous ice more than two million years old from the Allan Hills Blue Ice Area, East Antarctica. Concentrations of carbon dioxide and methane in ice core samples older than two million years have been altered by respiration, but some younger samples are pristine. The recovered ice cores extend direct observations of atmospheric carbon dioxide, methane, and Antarctic temperature (based on the deuterium/hydrogen isotope ratio δDice, a proxy for regional temperature) into the 40k world. All climate properties before eight hundred thousand years ago fall within the envelope of observations from continuous deep Antarctic ice cores that characterize the 100k world. However, the lowest measured carbon dioxide and methane concentrations and Antarctic temperature in the 40k world are well above glacial values from the past eight hundred thousand years. Our results confirm that the amplitudes of glacial-interglacial variations in atmospheric greenhouse gases and Antarctic climate were reduced in the 40k world, and that the transition from the 40k to the 100k world was accompanied by a decline in minimum carbon dioxide concentrations during glacial maxima.
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26
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Davis SJM. Rabbits and Bergmann’s rule: how cold was Portugal during the last glaciation? Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/blz098] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Osteometric data from > 450 modern wild rabbits, mostly from Portugal, Spain and France, show an inverse correlation between their size and the temperature of the environment, in accordance with Bergmann’s rule. Similar measurements made on some 1660 rabbit bones from 14 Portuguese late Pleistocene and Holocene archaeological sites indicate that rabbits became considerably smaller at the Pleistocene–Holocene boundary. Thus, rabbit size varies or varied with temperature both today and in the past. A direct temperature–size relationship was assumed, and the regression of modern rabbit bone size on temperature was then used to calibrate the temperature equivalent for the change of size of rabbit bones in the past. The result indicates a Last Glacial Maximum to present-day difference, Δt°, of 7 or 8 °C. An alternative interpretation that does not assume a direct temperature–size relationship would indicate that the environment in Portugal 15 000–30 000 years ago was similar to that in northern France today.
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Affiliation(s)
- Simon J M Davis
- Laboratório de Arqueociências, Direcção Geral do Património Cultural (DGPC), Calçada do Mirante à Ajuda 10ª, Lisbon, Portugal
- UNIARQ – Centro de Arqueologia da Universidade de Lisboa, Faculdade de Letras da Universidade de Lisboa, Lisbon, Portugal
- Centro de Investigação em Biodiversidade, Universidade do Porto, Campus Agrário de Vairão, Vairão, Portugal
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27
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Earth's radiative imbalance from the Last Glacial Maximum to the present. Proc Natl Acad Sci U S A 2019; 116:14881-14886. [PMID: 31285336 DOI: 10.1073/pnas.1905447116] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The energy imbalance at the top of the atmosphere determines the temporal evolution of the global climate, and vice versa changes in the climate system can alter the planetary energy fluxes. This interplay is fundamental to our understanding of Earth's heat budget and the climate system. However, even today, the direct measurement of global radiative fluxes is difficult, such that most assessments are based on changes in the total energy content of the climate system. We apply the same approach to estimate the long-term evolution of Earth's radiative imbalance in the past. New measurements of noble gas-derived mean ocean temperature from the European Project for Ice Coring in Antarctica Dome C ice core covering the last 40,000 y, combined with recent results from the West Antarctic Ice Sheet Divide ice core and the sea-level record, allow us to quantitatively reconstruct the history of the climate system energy budget. The temporal derivative of this quantity must be equal to the planetary radiative imbalance. During the deglaciation, a positive imbalance of typically +0.2 W⋅m-2 is maintained for ∼10,000 y, however, with two distinct peaks that reach up to 0.4 W⋅m-2 during times of substantially reduced Atlantic Meridional Overturning Circulation. We conclude that these peaks are related to net changes in ocean heat uptake, likely due to rapid changes in North Atlantic deep-water formation and their impact on the global radiative balance, while changes in cloud coverage, albeit uncertain, may also factor into the picture.
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Khatiwala S, Schmittner A, Muglia J. Air-sea disequilibrium enhances ocean carbon storage during glacial periods. SCIENCE ADVANCES 2019; 5:eaaw4981. [PMID: 31206024 PMCID: PMC6561735 DOI: 10.1126/sciadv.aaw4981] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 05/09/2019] [Indexed: 06/09/2023]
Abstract
The prevailing hypothesis for lower atmospheric carbon dioxide (CO2) concentrations during glacial periods is an increased efficiency of the ocean's biological pump. However, tests of this and other hypotheses have been hampered by the difficulty to accurately quantify ocean carbon components. Here, we use an observationally constrained earth system model to precisely quantify these components and the role that different processes play in simulated glacial-interglacial CO2 variations. We find that air-sea disequilibrium greatly amplifies the effects of cooler temperatures and iron fertilization on glacial ocean carbon storage even as the efficiency of the soft-tissue biological pump decreases. These two processes, which have previously been regarded as minor, explain most of our simulated glacial CO2 drawdown, while ocean circulation and sea ice extent, hitherto considered dominant, emerge as relatively small contributors.
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Affiliation(s)
- S. Khatiwala
- Department of Earth Sciences, University of Oxford, Oxford, UK
| | - A. Schmittner
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
| | - J. Muglia
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
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29
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Affolter S, Häuselmann A, Fleitmann D, Edwards RL, Cheng H, Leuenberger M. Central Europe temperature constrained by speleothem fluid inclusion water isotopes over the past 14,000 years. SCIENCE ADVANCES 2019; 5:eaav3809. [PMID: 31183398 PMCID: PMC6551184 DOI: 10.1126/sciadv.aav3809] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 04/25/2019] [Indexed: 06/09/2023]
Abstract
The reasons for the early Holocene temperature discrepancy between northern hemispheric model simulations and paleoclimate reconstructions-known as the Holocene temperature conundrum-remain unclear. Using hydrogen isotopes of fluid inclusion water extracted from stalagmites from the Milandre Cave in Switzerland, we established a mid-latitude European mean annual temperature reconstruction for the past 14,000 years. Our Milandre Cave fluid inclusion temperature record (MC-FIT) resembles Greenland and Mediterranean sea surface temperature trends but differs from recent reconstructions obtained from biogenic proxies and climate models. The water isotopes are further synchronized with tropical precipitation records, stressing the Northern Hemisphere signature. Our results support the existence of a European Holocene Thermal Maximum and data-model temperature discrepancies. Moreover, data-data comparison reveals a significant latitudinal temperature gradient within Europe. Last, the MC-FIT record suggests that seasonal biases in the proxies are not the primary cause of the Holocene temperature conundrum.
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Affiliation(s)
- Stéphane Affolter
- Climate and Environmental Physics, Physics Institute, University of Bern, 3012 Bern, Switzerland
- Oeschger Center for Climate Change Research, University of Bern, 3012 Bern, Switzerland
| | - Anamaria Häuselmann
- Oeschger Center for Climate Change Research, University of Bern, 3012 Bern, Switzerland
- Institute of Geological Sciences, University of Bern, 3012 Bern, Switzerland
| | - Dominik Fleitmann
- Oeschger Center for Climate Change Research, University of Bern, 3012 Bern, Switzerland
- Institute of Geological Sciences, University of Bern, 3012 Bern, Switzerland
- Department of Archaeology and Center for Past Climate Change, School of Archaeology, Geography and Environmental Science, University of Reading, Reading, UK
| | - R. Lawrence Edwards
- Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, USA
| | - Hai Cheng
- Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, USA
- Institute of Global Environmental Change, Xi’an Jiatong University, Xi’an 710049, China
| | - Markus Leuenberger
- Climate and Environmental Physics, Physics Institute, University of Bern, 3012 Bern, Switzerland
- Oeschger Center for Climate Change Research, University of Bern, 3012 Bern, Switzerland
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30
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Zhang F, Xu X, He J, Du B, Wang Y. Highly sensitive temperature sensor based on a polymer-infiltrated Mach-Zehnder interferometer created in graded index fiber. OPTICS LETTERS 2019; 44:2466-2469. [PMID: 31090708 DOI: 10.1364/ol.44.002466] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 04/20/2019] [Indexed: 06/09/2023]
Abstract
A highly sensitive temperature sensor is proposed and demonstrated based on a UV-curable polymer-infiltrated Mach-Zehnder interferometer (MZI) created in a graded index fiber (GIF). The device was constructed by splicing a half-pitch GIF between two single-mode fibers and creating an inner air cavity in one lateral side of the GIF core by means of femtosecond laser micromachining. The air cavity and the residual GIF core functioned as two interference arms of the MZI. Moreover, the GIF was used as a miniature in-fiber collimator to reduce insertion loss of the air cavity. Experimental results show such an MZI device has a high refractive index (RI) sensitivity of 24611.54 nm/RIU (RI=1.545-1.565). Subsequently, thermo-sensitive polymer liquid was infiltrated into the air cavity, then cured with UV illumination, and annealed at 50°C for 12 h. The infiltrated MZI exhibits a high temperature sensitivity of -13.27 nm/°C. In addition, this MZI also has excellent thermal stability and repeatability, compact structure, low insertion loss, and high fringe visibility. As such, the proposed MZI could be developed for high-accuracy temperature measurements in many areas such as biomedical or oceanographic applications.
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Sedimentary record from Patagonia, southern Chile supports cosmic-impact triggering of biomass burning, climate change, and megafaunal extinctions at 12.8 ka. Sci Rep 2019; 9:4413. [PMID: 30867437 PMCID: PMC6416299 DOI: 10.1038/s41598-018-38089-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 12/19/2018] [Indexed: 11/09/2022] Open
Abstract
The Younger Dryas (YD) impact hypothesis posits that fragments of a large, disintegrating asteroid/comet struck North America, South America, Europe, and western Asia ~12,800 years ago. Multiple airbursts/impacts produced the YD boundary layer (YDB), depositing peak concentrations of platinum, high-temperature spherules, meltglass, and nanodiamonds, forming an isochronous datum at >50 sites across ~50 million km² of Earth's surface. This proposed event triggered extensive biomass burning, brief impact winter, YD climate change, and contributed to extinctions of late Pleistocene megafauna. In the most extensive investigation south of the equator, we report on a ~12,800-year-old sequence at Pilauco, Chile (~40°S), that exhibits peak YD boundary concentrations of platinum, gold, high-temperature iron- and chromium-rich spherules, and native iron particles rarely found in nature. A major peak in charcoal abundance marks an intense biomass-burning episode, synchronous with dramatic changes in vegetation, including a high-disturbance regime, seasonality in precipitation, and warmer conditions. This is anti-phased with northern-hemispheric cooling at the YD onset, whose rapidity suggests atmospheric linkage. The sudden disappearance of megafaunal remains and dung fungi in the YDB layer at Pilauco correlates with megafaunal extinctions across the Americas. The Pilauco record appears consistent with YDB impact evidence found at sites on four continents.
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Hamme RC, Nicholson DP, Jenkins WJ, Emerson SR. Using Noble Gases to Assess the Ocean's Carbon Pumps. ANNUAL REVIEW OF MARINE SCIENCE 2019; 11:75-103. [PMID: 30216737 DOI: 10.1146/annurev-marine-121916-063604] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Natural mechanisms in the ocean, both physical and biological, concentrate carbon in the deep ocean, resulting in lower atmospheric carbon dioxide. The signals of these carbon pumps overlap to create the observed carbon distribution in the ocean, making the individual impact of each pump difficult to disentangle. Noble gases have the potential to directly quantify the physical carbon solubility pump and to indirectly improve estimates of the biological organic carbon pump. Noble gases are biologically inert, can be precisely measured, and span a range of physical properties. We present dissolved neon, argon, and krypton data spanning the Atlantic, Southern, Pacific, and Arctic Oceans. Comparisons between deep-ocean observations and models of varying complexity enable the rates of processes that control the carbon solubility pump to be quantified and thus provide an important metric for ocean model skill. Noble gases also provide a powerful means of assessing air-sea gas exchange parameterizations.
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Affiliation(s)
- Roberta C Hamme
- School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada;
| | - David P Nicholson
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02540, USA; ,
| | - William J Jenkins
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02540, USA; ,
| | - Steven R Emerson
- School of Oceanography, University of Washington, Seattle, Washington 98195, USA;
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Rae JWB, Burke A, Robinson LF, Adkins JF, Chen T, Cole C, Greenop R, Li T, Littley EFM, Nita DC, Stewart JA, Taylor BJ. CO 2 storage and release in the deep Southern Ocean on millennial to centennial timescales. Nature 2018; 562:569-573. [PMID: 30356182 DOI: 10.1038/s41586-018-0614-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 08/29/2018] [Indexed: 11/09/2022]
Abstract
The cause of changes in atmospheric carbon dioxide (CO2) during the recent ice ages is yet to be fully explained. Most mechanisms for glacial-interglacial CO2 change have centred on carbon exchange with the deep ocean, owing to its large size and relatively rapid exchange with the atmosphere1. The Southern Ocean is thought to have a key role in this exchange, as much of the deep ocean is ventilated to the atmosphere in this region2. However, it is difficult to reconstruct changes in deep Southern Ocean carbon storage, so few direct tests of this hypothesis have been carried out. Here we present deep-sea coral boron isotope data that track the pH-and thus the CO2 chemistry-of the deep Southern Ocean over the past forty thousand years. At sites closest to the Antarctic continental margin, and most influenced by the deep southern waters that form the ocean's lower overturning cell, we find a close relationship between ocean pH and atmospheric CO2: during intervals of low CO2, ocean pH is low, reflecting enhanced ocean carbon storage; and during intervals of rising CO2, ocean pH rises, reflecting loss of carbon from the ocean to the atmosphere. Correspondingly, at shallower sites we find rapid (millennial- to centennial-scale) decreases in pH during abrupt increases in CO2, reflecting the rapid transfer of carbon from the deep ocean to the upper ocean and atmosphere. Our findings confirm the importance of the deep Southern Ocean in ice-age CO2 change, and show that deep-ocean CO2 release can occur as a dynamic feedback to rapid climate change on centennial timescales.
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Affiliation(s)
- J W B Rae
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK.
| | - A Burke
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - L F Robinson
- School of Earth Sciences, University of Bristol, Bristol, UK
| | - J F Adkins
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - T Chen
- School of Earth Sciences, University of Bristol, Bristol, UK.,School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
| | - C Cole
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - R Greenop
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - T Li
- School of Earth Sciences, University of Bristol, Bristol, UK.,School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
| | - E F M Littley
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - D C Nita
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK.,Faculty of Environmental Science and Engineering, Babes-Bolyai University, Cluj-Napoca, Romania
| | - J A Stewart
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK.,School of Earth Sciences, University of Bristol, Bristol, UK
| | - B J Taylor
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
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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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Bereiter B, Kawamura K, Severinghaus JP. New methods for measuring atmospheric heavy noble gas isotope and elemental ratios in ice core samples. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2018; 32:801-814. [PMID: 29500867 DOI: 10.1002/rcm.8099] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 02/21/2018] [Accepted: 02/22/2018] [Indexed: 06/08/2023]
Abstract
RATIONALE The global ocean constitutes the largest heat buffer in the global climate system, but little is known about its past changes. The isotopic and elemental ratios of heavy noble gases (krypton and xenon), together with argon and nitrogen in trapped air from ice cores, can be used to reconstruct past mean ocean temperatures (MOTs). Here we introduce two successively developed methods to measure these parameters with a sufficient precision to provide new constraints on past changes in MOT. METHODS The air from an 800-g ice sample - containing roughly 80 mL STP air - is extracted and processed to be analyzed on two independent dual-inlet isotope ratio mass spectrometers. The primary isotope ratios (δ15 N, δ40 Ar and δ86 Kr values) are obtained with precisions in the range of 1 per meg (0.001‰) per mass unit. The three elemental ratio values δKr/N2 , δXe/N2 and δXe/Kr are obtained using sequential (non-simultaneous) peak-jumping, reaching precisions in the range of 0.1-0.3‰. RESULTS The latest version of the method achieves a 30% to 50% better precision on the elemental ratios and a twofold better sample throughput than the previous one. The method development uncovered an unexpected source of artefactual gas fractionation in a closed system that is caused by adiabatic cooling and warming of gases (termed adiabatic fractionation) - a potential source of measurement artifacts in other methods. CONCLUSIONS The precisions of the three elemental ratios δKr/N2 , δXe/N2 and δXe/Kr - which all contain the same MOT information - suggest smaller uncertainties for reconstructed MOTs (±0.3-0.1°C) than previous studies have attained. Due to different sensitivities of the noble gases to changes in MOT, δXe/N2 provides the best constraints on the MOT under the given precisions followed by δXe/Kr, and δKr/N2 ; however, using all of them helps to detect methodological artifacts and issues with ice quality.
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Affiliation(s)
- Bernhard Bereiter
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
- Climate and Environmental Physics, Physics Institute, and Oeschger Center for Climate Research, University of Bern, 3012, Bern, Switzerland
- Laboratory for Air Pollution/Environmental Technology, Empa, 8600, Dübendorf, Switzerland
| | - Kenji Kawamura
- National Institute of Polar Research, Research Organizations of Information and Systems, 10-3 Midori-cho, Tachikawa, Tokyo, 190-8518, Japan
- Department of Polar Science, Graduate University for Advanced Studies (SOKENDAI), 10-3 Midori-cho, Tachikawa, Tokyo, 190-8518, Japan
- Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
| | - Jeffrey P Severinghaus
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
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