1
|
Slodownik MA. The non-flowering plants of a near-polar forest in East Gondwana, Tasmania, Australia, during the Early Eocene Climatic Optimum. AMERICAN JOURNAL OF BOTANY 2024:e16398. [PMID: 39192571 DOI: 10.1002/ajb2.16398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 06/02/2024] [Accepted: 06/03/2024] [Indexed: 08/29/2024]
Abstract
PREMISE The Cenozoic Macquarie Harbour Formation (MHF) hosts one of the oldest and southernmost post-Cretaceous fossil plant assemblages in Australia. Coinciding with the Early Eocene Climatic Optimum (EECO) and predating the breakup of Australia from Antarctica, it offers critical data to study the diversity and extent of the Austral Polar Forest Biome, and the floristic divergence between Australasia and South America resulting from the Gondwana breakup. METHODS The micromorphology and macromorphology of new fossil plant compressions from the MHF were described and systematically analyzed. Previously published non-flowering plant records were reviewed and revised. Macrofossil abundance data were provided. The flora was compared with other early Paleogene assemblages from across the Southern Hemisphere. RESULTS Twelve species of non-flowering plants were identified from the macrofossil record. Conifers include Araucariaceae (Araucaria macrophylla, A. readiae, A. timkarikensis sp. nov., and Araucarioides linearis), Podocarpaceae (Acmopyle glabra, Dacrycarpus mucronatus, Podocarpus paralungatikensis sp. nov., and Retrophyllum sp.), and Cupressaceae (Libocedrus microformis). Dacrycarpus linifolius was designated a junior synonym of D. mucronatus. Further components include a cycad (Bowenia johnsonii, Zamiaceae), a pteridosperm (Komlopteris cenozoicus, Umkomasiaceae), and a fern (Lygodium dinmorphyllum, Schizaeaceae). CONCLUSIONS The fossil assemblage represents a mixed near-polar forest with a high diversity of conifers. The morphology and preservation of several species indicate adaptations to life at high latitudes. The coexistence of large- and small-leaved conifers implies complex, possibly open forest structures. Comparisons with contemporaneous assemblages from Argentina support a circumpolar biome during the EECO, reaching from southern Australia across Antarctica to southern South America.
Collapse
Affiliation(s)
- Miriam A Slodownik
- School of Biological Sciences, University of Adelaide, Adelaide, 5005, South Australia, Australia
| |
Collapse
|
2
|
Halberstadt ARW, Gasson E, Pollard D, Marschalek J, DeConto RM. Geologically constrained 2-million-year-long simulations of Antarctic Ice Sheet retreat and expansion through the Pliocene. Nat Commun 2024; 15:7014. [PMID: 39147756 PMCID: PMC11327337 DOI: 10.1038/s41467-024-51205-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 08/01/2024] [Indexed: 08/17/2024] Open
Abstract
Pliocene global temperatures periodically exceeded modern levels, offering insights into ice sheet sensitivity to warm climates. Ice-proximal geologic records from this period provide crucial but limited glimpses of Antarctic Ice Sheet behavior. We use an ice sheet model driven by climate model snapshots to simulate transient glacial cyclicity from 4.5 to 2.6 Ma, providing spatial and temporal context for geologic records. By evaluating model simulations against a comprehensive synthesis of geologic data, we translate the intermittent geologic record into a continuous reconstruction of Antarctic sea level contributions, revealing a dynamic ice sheet that contributed up to 25 m of glacial-interglacial sea level change. Model grounding line behavior across all major Antarctic catchments exhibits an extended period of receded ice during the mid-Pliocene, coincident with proximal geologic data around Antarctica but earlier than peak warmth in the Northern Hemisphere. Marine ice sheet collapse is triggered with 1.5 °C model subsurface ocean warming.
Collapse
Affiliation(s)
- Anna Ruth W Halberstadt
- Department of Earth and Planetary Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, USA.
| | - Edward Gasson
- School of Geographical Sciences, University of Bristol, Bristol, UK
| | - David Pollard
- Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA, USA
| | - James Marschalek
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | - Robert M DeConto
- Department of Geosciences, University of Massachusetts Amherst, Amherst, MA, USA
| |
Collapse
|
3
|
Wang Y, Shi D, Liu G, Huang B, Li Z. Shear-Enhanced Ion Rejection during Seawater Freezing. J Phys Chem B 2023; 127:10404-10410. [PMID: 37997846 DOI: 10.1021/acs.jpcb.3c05432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2023]
Abstract
Ion rejection during seawater freezing is the basis for freeze desalination. A high ion rejection rate is desired for improving the performance of freeze desalination. In this work, we propose a method to enhance the ion rejection rate through external shear, which is demonstrated through molecular dynamics (MD) simulations and experiments. MD simulations show that the ion rejection rate increases with an increasing shear rate. This is attributed to the disruption of the hydration bonds between ions and water molecules in the hydration shell caused by the shear. Consequently, the mobility of ions is increased, and the energy barrier is reduced at the ice-water interface such that ions have a greater chance of diffusing into the aqueous solution, leading to an enhanced ion rejection rate. The MD results in this work are qualitatively confirmed by experiments and provide insights into the enhancement of the ion rejection rate through external parameters.
Collapse
Affiliation(s)
- Yixiang Wang
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong
| | - Dachuang Shi
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong
| | - Gongze Liu
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong
| | - Baoling Huang
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong
| | - Zhigang Li
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong
| |
Collapse
|
4
|
Jamieson SSR, Ross N, Paxman GJG, Clubb FJ, Young DA, Yan S, Greenbaum J, Blankenship DD, Siegert MJ. An ancient river landscape preserved beneath the East Antarctic Ice Sheet. Nat Commun 2023; 14:6507. [PMID: 37875503 PMCID: PMC10597991 DOI: 10.1038/s41467-023-42152-2] [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: 05/10/2023] [Accepted: 10/02/2023] [Indexed: 10/26/2023] Open
Abstract
The East Antarctic Ice Sheet (EAIS) has its origins ca. 34 million years ago. Since then, the impact of climate change and past fluctuations in the EAIS margin has been reflected in periods of extensive vs. restricted ice cover and the modification of much of the Antarctic landscape. Resolving processes of landscape evolution is therefore critical for establishing ice sheet history, but it is rare to find unmodified landscapes that record past ice conditions. Here, we discover an extensive relic pre-glacial landscape preserved beneath the central EAIS despite millions of years of ice cover. The landscape was formed by rivers prior to ice sheet build-up but later modified by local glaciation before being dissected by outlet glaciers at the margin of a restricted ice sheet. Preservation of the relic surfaces indicates an absence of significant warm-based ice throughout their history, suggesting any transitions between restricted and expanded ice were rapid.
Collapse
Affiliation(s)
| | - Neil Ross
- School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
| | - Guy J G Paxman
- Department of Geography, Durham University, Durham, DH1 3LE, UK
| | - Fiona J Clubb
- Department of Geography, Durham University, Durham, DH1 3LE, UK
| | - Duncan A Young
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, USA
| | - Shuai Yan
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, USA
- Department of Geosciences, Jackson School of Geosciences, University of Texas at Austin, Austin, USA
| | - Jamin Greenbaum
- Scripps Institute for Oceanography, University of California at San Diego, San Diego, USA
| | - Donald D Blankenship
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, USA
| | - Martin J Siegert
- Tremough House, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
| |
Collapse
|
5
|
Hirano D, Tamura T, Kusahara K, Fujii M, Yamazaki K, Nakayama Y, Ono K, Itaki T, Aoyama Y, Simizu D, Mizobata K, Ohshima KI, Nogi Y, Rintoul SR, van Wijk E, Greenbaum JS, Blankenship DD, Saito K, Aoki S. On-shelf circulation of warm water toward the Totten Ice Shelf in East Antarctica. Nat Commun 2023; 14:4955. [PMID: 37591840 PMCID: PMC10435550 DOI: 10.1038/s41467-023-39764-z] [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: 01/14/2022] [Accepted: 06/26/2023] [Indexed: 08/19/2023] Open
Abstract
The Totten Glacier in East Antarctica, with an ice volume equivalent to >3.5 m of global sea-level rise, is grounded below sea level and, therefore, vulnerable to ocean forcing. Here, we use bathymetric and oceanographic observations from previously unsampled parts of the Totten continental shelf to reveal on-shelf warm water pathways defined by deep topographic features. Access of warm water to the Totten Ice Shelf (TIS) cavity is facilitated by a deep shelf break, a broad and deep depression on the shelf, a cyclonic circulation that carries warm water to the inner shelf, and deep troughs that provide direct access to the TIS cavity. The temperature of the warmest water reaching the TIS cavity varies by ~0.8 °C on an interannual timescale. Numerical simulations constrained by the updated bathymetry demonstrate that the deep troughs play a critical role in regulating ocean heat transport to the TIS cavity and the subsequent basal melt of the ice shelf.
Collapse
Grants
- JP20H04961 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP20K12132 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP22H05003 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H06316 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H06317 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H06322 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H04710 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP21H04931 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP22H05003 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H06323 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP19K12301 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP22H05003 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP22H01337 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP21K13989 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP21H03587 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP20H04970 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP22H05003 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H06316 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H06317 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H01157 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP20H05707 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H06322 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP17H01615 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP21H04918 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- OPP-2114454 National Science Foundation (NSF)
- OPP-1543452 National Science Foundation (NSF)
- OPP-1543452 National Science Foundation (NSF)
- the Joint Research Program of the Institute of Low Temperature Science, Hokkaido University
- National Institute of Polar Research (NIPR) through Project Research KP-303; the Center for the Promotion of Integrated Sciences of SOKENDAI
- MEXT-Program for the advanced studies of climate change projection (SENTAN) Grant Number JPMXD0722681344
- National Institute of Polar Research (NIPR) through Project Research KP-306; "Challenging Exploratory Research Projects for the Future" grant from Research Organization of Information and Systems
- Inoue Science Research Award from Inoue Science Foundation
- the Australian Government as part of the Antarctic Science Collaboration Initiative program; the Centre for Southern Hemisphere Oceans Research
- NASA’s Cryosphere Program under grant 80NSSC22K0387; the G. Unger Vetlesen Foundation
- the Science Program of Japanese Antarctic Research Expedition (JARE) as Prioritized Research Project
Collapse
Affiliation(s)
- Daisuke Hirano
- National Institute of Polar Research, Tachikawa, Japan.
- The Graduate University for Advanced Studies, SOKENDAI, Tachikawa, Japan.
| | - Takeshi Tamura
- National Institute of Polar Research, Tachikawa, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Tachikawa, Japan
| | - Kazuya Kusahara
- Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
| | - Masakazu Fujii
- National Institute of Polar Research, Tachikawa, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Tachikawa, Japan
| | - Kaihe Yamazaki
- National Institute of Polar Research, Tachikawa, Japan
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
- The Australian Centre for Excellence in Antarctic Science, University of Tasmania, Hobart, TAS, Australia
| | - Yoshihiro Nakayama
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
| | - Kazuya Ono
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | - Takuya Itaki
- National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
| | - Yuichi Aoyama
- National Institute of Polar Research, Tachikawa, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Tachikawa, Japan
| | | | - Kohei Mizobata
- Tokyo University of Marine Science and Technology, Tokyo, Japan
| | - Kay I Ohshima
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
| | - Yoshifumi Nogi
- National Institute of Polar Research, Tachikawa, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Tachikawa, Japan
| | - Stephen R Rintoul
- CSIRO Environment, Hobart, TAS, Australia
- Centre for Southern Hemisphere Oceans Research, Hobart, TAS, Australia
- Australian Antarctic Program Partnership, University of Tasmania, Hobart, TAS, Australia
| | - Esmee van Wijk
- CSIRO Environment, Hobart, TAS, Australia
- Australian Antarctic Program Partnership, University of Tasmania, Hobart, TAS, Australia
| | - Jamin S Greenbaum
- Scripps Institution of Oceanography, University of California, San Diego, CA, USA
| | | | - Koji Saito
- Japan Coast Guard, Hydrographic and Oceanographic Department, Tokyo, Japan
| | - Shigeru Aoki
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
- Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan
| |
Collapse
|
6
|
Hochmuth K, Whittaker JM, Sauermilch I, Klocker A, Gohl K, LaCasce JH. Southern Ocean biogenic blooms freezing-in Oligocene colder climates. Nat Commun 2022; 13:6785. [PMID: 36351905 PMCID: PMC9646741 DOI: 10.1038/s41467-022-34623-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 11/01/2022] [Indexed: 11/10/2022] Open
Abstract
Crossing a key atmospheric CO2 threshold triggered a fundamental global climate reorganisation ~34 million years ago (Ma) establishing permanent Antarctic ice sheets. Curiously, a more dramatic CO2 decline (~800-400 ppm by the Early Oligocene(~27 Ma)), postdates initial ice sheet expansion but the mechanisms driving this later, rapid drop in atmospheric carbon during the early Oligocene remains elusive and controversial. Here we use marine seismic reflection and borehole data to reveal an unprecedented accumulation of early Oligocene strata (up to 2.2 km thick over 1500 × 500 km) with a major biogenic component in the Australian Southern Ocean. High-resolution ocean simulations demonstrate that a tectonically-driven, one-off reorganisation of ocean currents, caused a unique period where current instability coincided with high nutrient input from the Antarctic continent. This unrepeated and short-lived environment favoured extreme bioproductivity and enhanced sediment burial. The size and rapid accumulation of this sediment package potentially holds ~1.067 × 1015 kg of the 'missing carbon' sequestered during the decline from an Eocene high CO2-world to a mid-Oligocene medium CO2-world, highlighting the exceptional role of the Southern Ocean in modulating long-term climate.
Collapse
Affiliation(s)
- Katharina Hochmuth
- grid.9918.90000 0004 1936 8411School of Geography, Geology and the Environment, University of Leicester, Leicester, UK ,grid.1009.80000 0004 1936 826XInstitute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS Australia ,grid.1009.80000 0004 1936 826XAustralian Center for Excellence in Antarctic Sciences, University of Tasmania, Hobart, TAS Australia
| | - Joanne M. Whittaker
- grid.1009.80000 0004 1936 826XInstitute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS Australia ,grid.1009.80000 0004 1936 826XAustralian Center for Excellence in Antarctic Sciences, University of Tasmania, Hobart, TAS Australia
| | - Isabel Sauermilch
- grid.5477.10000000120346234Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands
| | - Andreas Klocker
- grid.5510.10000 0004 1936 8921Department of Geosciences, University of Oslo, Oslo, Norway ,Present Address: NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
| | - Karsten Gohl
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute Helmholtz-Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Joseph H. LaCasce
- grid.5510.10000 0004 1936 8921Department of Geosciences, University of Oslo, Oslo, Norway
| |
Collapse
|
7
|
Polar amplification comparison among Earth's three poles under different socioeconomic scenarios from CMIP6 surface air temperature. Sci Rep 2022; 12:16548. [PMID: 36192431 PMCID: PMC9529914 DOI: 10.1038/s41598-022-21060-3] [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: 02/04/2022] [Accepted: 09/22/2022] [Indexed: 11/26/2022] Open
Abstract
The polar amplification (PA) has become the focus of climate change. However, there are seldom comparisons of amplification among Earth’s three poles of Arctic (latitude higher than 60 °N), Antarctica (Antarctic Ice Sheet) and the Third Pole (the High Mountain Asia with the elevation higher than 4000 m) under different socioeconomic scenarios. Based on CMIP6 multi-model ensemble, two types of PA index (PAI) have been defined to quantify the PA intensity and variations, and PAI1/PAI2 is defined as the ratio of the absolute value of surface air temperature linear trend over Earth’s three poles and that for global mean/over other regions except Earth’s three poles. Arctic warms fastest in winter and weakest in summer, followed by the Third Pole, and Antarctica warms least. The similar phenomenon proceeds when global warming of 1.5–2.0 °C, and 2.0–3.0 °C above pre-industrial levels. After removing the Earth’s three poles self-influence, all the PAI2s increase much more obviously relative to the PAI1s, especially the Antarctic PAI. Earth’s three poles warm faster than the other regions. With the forcing increasing, PA accelerates much more over Antarctica and the Third Pole, but becomes weaker over Arctic. This demonstrates that future warming rate might make a large difference among Earth’s three poles under different scenarios.
Collapse
|
8
|
Stokes CR, Abram NJ, Bentley MJ, Edwards TL, England MH, Foppert A, Jamieson SSR, Jones RS, King MA, Lenaerts JTM, Medley B, Miles BWJ, Paxman GJG, Ritz C, van de Flierdt T, Whitehouse PL. Response of the East Antarctic Ice Sheet to past and future climate change. Nature 2022; 608:275-286. [PMID: 35948707 DOI: 10.1038/s41586-022-04946-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 06/07/2022] [Indexed: 11/09/2022]
Abstract
The East Antarctic Ice Sheet contains the vast majority of Earth's glacier ice (about 52 metres sea-level equivalent), but is often viewed as less vulnerable to global warming than the West Antarctic or Greenland ice sheets. However, some regions of the East Antarctic Ice Sheet have lost mass over recent decades, prompting the need to re-evaluate its sensitivity to climate change. Here we review the response of the East Antarctic Ice Sheet to past warm periods, synthesize current observations of change and evaluate future projections. Some marine-based catchments that underwent notable mass loss during past warm periods are losing mass at present but most projections indicate increased accumulation across the East Antarctic Ice Sheet over the twenty-first century, keeping the ice sheet broadly in balance. Beyond 2100, high-emissions scenarios generate increased ice discharge and potentially several metres of sea-level rise within just a few centuries, but substantial mass loss could be averted if the Paris Agreement to limit warming below 2 degrees Celsius is satisfied.
Collapse
Affiliation(s)
| | - Nerilie J Abram
- Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory, Australia.,Australian Centre for Excellence in Antarctic Science, Australian National University, Canberra, Australian Capital Territory, Australia
| | | | | | - Matthew H England
- Climate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia.,Australian Centre for Excellence in Antarctic Science, University of New South Wales, Sydney, New South Wales, Australia
| | - Annie Foppert
- Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
| | | | - Richard S Jones
- School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria, Australia.,Securing Antarctica's Environmental Future, Monash University, Clayton, Victoria, Australia
| | - Matt A King
- School of Geography, Planning, and Spatial Sciences, University of Tasmania, Hobart, Tasmania, Australia.,Australian Centre for Excellence in Antarctic Science, University of Tasmania, Hobart, Tasmania, Australia
| | - Jan T M Lenaerts
- Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA
| | - Brooke Medley
- Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | | | - Guy J G Paxman
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
| | - Catherine Ritz
- Institut des Géosciences de l'Environnement, Université Grenoble Alpes, Grenoble, France
| | - Tina van de Flierdt
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | | |
Collapse
|
9
|
Tierney JE, Poulsen CJ, Montañez IP, Bhattacharya T, Feng R, Ford HL, Hönisch B, Inglis GN, Petersen SV, Sagoo N, Tabor CR, Thirumalai K, Zhu J, Burls NJ, Foster GL, Goddéris Y, Huber BT, Ivany LC, Kirtland Turner S, Lunt DJ, McElwain JC, Mills BJW, Otto-Bliesner BL, Ridgwell A, Zhang YG. Past climates inform our future. Science 2020; 370:370/6517/eaay3701. [DOI: 10.1126/science.aay3701] [Citation(s) in RCA: 111] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
| | - Christopher J. Poulsen
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Isabel P. Montañez
- Department of Earth and Planetary Sciences, University of California, Davis, Davis, CA, USA
| | - Tripti Bhattacharya
- Department of Earth and Environmental Sciences, Syracuse University, Syracuse, NY, USA
| | - Ran Feng
- Department of Geosciences, University of Connecticut, Storrs, CT, USA
| | - Heather L. Ford
- School of Geography, Queen Mary University of London, London, UK
| | - Bärbel Hönisch
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
| | - Gordon N. Inglis
- Department of Earth and Environmental Sciences, Columbia University, Palisades, NY, USA
| | - Sierra V. Petersen
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Navjit Sagoo
- Department of Meteorology, University of Stockholm, Stockholm, Sweden
| | - Clay R. Tabor
- Department of Geosciences, University of Connecticut, Storrs, CT, USA
| | | | - Jiang Zhu
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Natalie J. Burls
- Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, VA, USA
| | - Gavin L. Foster
- Department of Earth and Environmental Sciences, Columbia University, Palisades, NY, USA
| | - Yves Goddéris
- Centre National de la Recherche Scientifique, Géosciences Environnement Toulouse, Toulouse, France
| | - Brian T. Huber
- Department of Paleobiology, Smithsonian National Museum of Natural History, Washington, DC, USA
| | - Linda C. Ivany
- Department of Earth and Environmental Sciences, Syracuse University, Syracuse, NY, USA
| | | | - Daniel J. Lunt
- School of Geographical Sciences, University of Bristol, Bristol, UK
| | | | | | | | - Andy Ridgwell
- Department of Earth Science, University of California, Riverside, Riverside, CA, USA
| | - Yi Ge Zhang
- Department of Oceanography, Texas A&M University, College Station, TX, USA
| |
Collapse
|
10
|
Miller KG, Browning JV, Schmelz WJ, Kopp RE, Mountain GS, Wright JD. Cenozoic sea-level and cryospheric evolution from deep-sea geochemical and continental margin records. SCIENCE ADVANCES 2020; 6:eaaz1346. [PMID: 32440543 PMCID: PMC7228749 DOI: 10.1126/sciadv.aaz1346] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 03/16/2020] [Indexed: 05/14/2023]
Abstract
Using Pacific benthic foraminiferal δ18O and Mg/Ca records, we derive a Cenozoic (66 Ma) global mean sea level (GMSL) estimate that records evolution from an ice-free Early Eocene to Quaternary bipolar ice sheets. These GMSL estimates are statistically similar to "backstripped" estimates from continental margins accounting for compaction, loading, and thermal subsidence. Peak warmth, elevated GMSL, high CO2, and ice-free "Hothouse" conditions (56 to 48 Ma) were followed by "Cool Greenhouse" (48 to 34 Ma) ice sheets (10 to 30 m changes). Continental-scale ice sheets ("Icehouse") began ~34 Ma (>50 m changes), permanent East Antarctic ice sheets at 12.8 Ma, and bipolar glaciation at 2.5 Ma. The largest GMSL fall (27 to 20 ka; ~130 m) was followed by a >40 mm/yr rise (19 to 10 ka), a slowing (10 to 2 ka), and a stillstand until ~1900 CE, when rates began to rise. High long-term CO2 caused warm climates and high sea levels, with sea-level variability dominated by periodic Milankovitch cycles.
Collapse
Affiliation(s)
- Kenneth G. Miller
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
- Corresponding author.
| | - James V. Browning
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - W. John Schmelz
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - Robert E. Kopp
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - Gregory S. Mountain
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - James D. Wright
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
- Institute of Earth, Ocean, and Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| |
Collapse
|
11
|
Radar-Derived Internal Structure and Basal Roughness Characterization along a Traverse from Zhongshan Station to Dome A, East Antarctica. REMOTE SENSING 2020. [DOI: 10.3390/rs12071079] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The internal layers of ice sheets from ice-penetrating radar (IPR) investigation preserve critical information about the ice-flow field and englacial conditions. This paper presents a new detailed analysis of spatial distribution characteristics of internal layers and subglacial topography of the East Antarctic ice sheet (EAIS) from Zhongshan Station to Dome A. The radar data of 1244 km along a traverse between Zhongshan Station and Dome A of EAIS were collected during the 29th Chinese National Antarctic Research Expedition (CHINARE 29, 2012/2013). In this study, the Internal Layering Continuity Index (ILCI) and basal roughness were taken as indicators to provide an opportunity to evaluate the past internal environment and dynamics of the ice sheet. Except for the upstream of Lambert Glacier, the fold patterns of internal layers are basically similar to that of the bed topography. The relatively flat basal topography and the decrease of ILCI with increasing depth provide evidence for identifying previous rapid ice flow areas that are unavailable to satellites, especially in the upstream of Lambert Glacier. Continuous internal layers of Dome A, recording the spatial change of past ice accumulation and ice-flow history over 160 ka, almost extend to the bed, with high ILCI and high basal roughness of the corresponding bed topography. There are three kinds of basal roughness patterns along the traverse, that is, “low ξt low η”, “low ξt high η”, and “high ξt high η”, where ξt represents the amplitude of the undulations, and quantifies the vertical variation of the bedrock, and η measures the frequency variation of fluctuations and the horizontal irregularity of the profile. The characteristics of internal layers and basal topography of the traverse between Zhongshan Station and Dome A provide new information for understanding the ancient ice-flow activity and the historical evolution of EAIS.
Collapse
|
12
|
Divergent mammalian body size in a stable Eocene greenhouse climate. Sci Rep 2020; 10:3987. [PMID: 32132560 PMCID: PMC7055232 DOI: 10.1038/s41598-020-60379-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Accepted: 01/21/2020] [Indexed: 11/08/2022] Open
Abstract
A negative correlation between body size and the latitudinal temperature gradient is well established for extant terrestrial endotherms but less so in the fossil record. Here we analyze the middle Eocene site of Geiseltal (Germany), whose record is considered to span ca. 5 Myrs of gradual global cooling, and generate one of the most extensive mammalian Paleogene body size datasets outside North America. The δ18O and δ13C isotopic analysis of bioapatite reveals signatures indicative of a humid, subtropical forest with no apparent climatic change across Geiseltal. Yet, body mass of hippomorphs and tapiromorphs diverges rapidly from a respective median body size of 39 kg and 124 kg at the base of the succession to 26 kg and 223 kg at the top. We attribute the divergent body mass evolution to a disparity in lifestyle, in which both taxa maximize their body size-related selective advantages. Our results therefore support the view that intrinsic biotic processes are an important driver of body mass outside of abrupt climate events. Moreover, the taxonomy previously used to infer the duration of the Geiseltal biota is not reproducible, which precludes chronological correlation with Eocene marine temperature curves.
Collapse
|
13
|
Warny S, Ferguson S, Hafner MS, Escarguel G. Using museum pelt collections to generate pollen prints from high-risk regions: A new palynological forensic strategy for geolocation. Forensic Sci Int 2019; 306:110061. [PMID: 31841931 DOI: 10.1016/j.forsciint.2019.110061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 10/24/2019] [Accepted: 11/11/2019] [Indexed: 10/25/2022]
Abstract
The use of pollen as a forensic tool for geolocation is a well-established practice worldwide in cases ranging from the provenance of drugs and other illicit materials to tracking the travel of individuals in criminal investigations. Here we propose a novel approach to generation of pollen databases that uses pollen vacuumed from mammal pelts collected historically from international areas that are now deemed too high risk to visit. We present the results of a study we conducted using mammal pelts collected from Mexico. This new investigative technique is important because, although it would seem that the ubiquitous and geo-specific nature of pollen would make pollen analysis among the most promising forensic tools for law enforcement and intelligence agencies, it is not the case. The process is notoriously slow because pollen identification is a tedious task requiring trained specialists (palynologists) who are few in number worldwide, and the reference materials necessary for geolocation usually are rare or absent, especially from regions of the world that are no longer safe to visit because of war or threat of terrorism. Current forensic palynological work is carried out by a few highly trained palynologists who require accurate databases of pollen distribution, especially from sensitive areas, to do their jobs accurately and efficiently. Our project shows the suitability of using the untapped museum pelt resources to support homeland security programs. This first palynological study using museum pelts yielded 133 different pollen and spore types, including 8 moss or fern families, 12 gymnosperm genera and 112 angiosperm species. We show that the palynological print from each region is statistically different with some important clustering, demonstrating the potential to use this technique for geolocation.
Collapse
Affiliation(s)
- Sophie Warny
- Department of Geology and Geophysics, E235 Howe-Russell, Louisiana State University, Baton Rouge, LA, 70803, USA; Museum of Natural Science, 109 Foster Hall, Louisiana State University, Baton Rouge, LA, 70803, USA.
| | - Shannon Ferguson
- Department of Geology and Geophysics, E235 Howe-Russell, Louisiana State University, Baton Rouge, LA, 70803, USA; Museum of Natural Science, 109 Foster Hall, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Mark S Hafner
- Museum of Natural Science, 109 Foster Hall, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Gilles Escarguel
- Laboratoire d'écologie des hydrosystèmes naturels et anthropisés, UMR CNRS 5023, Université Claude Bernard Lyon 1, Boulevard du 11 novembre 1918, F69622, Villeurbanne Cedex, France
| |
Collapse
|
14
|
Fingerprinting Proterozoic Bedrock in Interior Wilkes Land, East Antarctica. Sci Rep 2019; 9:10192. [PMID: 31308422 PMCID: PMC6629686 DOI: 10.1038/s41598-019-46612-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 07/02/2019] [Indexed: 11/17/2022] Open
Abstract
Wilkes Land in East Antarctica remains one of the last geological exploration frontiers on Earth. Hidden beneath kilometres of ice, its bedrock preserves a poorly-understood tectonic history that mirrors that of southern Australia and holds critical insights into past supercontinent cycles. Here, we use new and recently published Australian and Antarctic geological and geophysical data to present a novel interpretation of the age and character of crystalline basement and sedimentary cover of interior Wilkes Land. We combine new zircon U–Pb and Hf isotopic data from remote Antarctic outcrops with aeromagnetic data observations from the conjugate Australian-Antarctic margins to identify two new Antarctic Mesoproterozoic basement provinces corresponding to the continuation of the Coompana and Madura provinces of southern Australia into Wilkes Land. Using both detrital zircon U–Pb–Hf and authigenic monazite U–Th–Pb isotopic data from glacial erratic sandstone samples, we identify the presence of Neoproterozoic sedimentary rocks covering Mesoproterozoic basement. Together, these new geological insights into the ice-covered bedrock of Wilkes Land substantially improve correlations of Antarctic and Australian geological elements and provide key constraints on the tectonic architecture of this sector of the East Antarctic Shield and its role in supercontinent reconstructions.
Collapse
|
15
|
Back to the Future: Using Long-Term Observational and Paleo-Proxy Reconstructions to Improve Model Projections of Antarctic Climate. GEOSCIENCES 2019. [DOI: 10.3390/geosciences9060255] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Quantitative estimates of future Antarctic climate change are derived from numerical global climate models. Evaluation of the reliability of climate model projections involves many lines of evidence on past performance combined with knowledge of the processes that need to be represented. Routine model evaluation is mainly based on the modern observational period, which started with the establishment of a network of Antarctic weather stations in 1957/58. This period is too short to evaluate many fundamental aspects of the Antarctic and Southern Ocean climate system, such as decadal-to-century time-scale climate variability and trends. To help address this gap, we present a new evaluation of potential ways in which long-term observational and paleo-proxy reconstructions may be used, with a particular focus on improving projections. A wide range of data sources and time periods is included, ranging from ship observations of the early 20th century to ice core records spanning hundreds to hundreds of thousands of years to sediment records dating back 34 million years. We conclude that paleo-proxy records and long-term observational datasets are an underused resource in terms of strategies for improving Antarctic climate projections for the 21st century and beyond. We identify priorities and suggest next steps to addressing this.
Collapse
|
16
|
Past continental shelf evolution increased Antarctic ice sheet sensitivity to climatic conditions. Sci Rep 2018; 8:11323. [PMID: 30054536 PMCID: PMC6063862 DOI: 10.1038/s41598-018-29718-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 07/12/2018] [Indexed: 11/17/2022] Open
Abstract
Over the past 34 Million years, the Antarctic continental shelf has gradually deepened due to ice sheet loading, thermal subsidence, and erosion from repeated glaciations. The deepening that is recorded in the sedimentary deposits around the Antarctic margin indicates that after the mid-Miocene Climate Optimum (≈15 Ma), Antarctic Ice Sheet (AIS) dynamical response to climate conditions changed. We explore end-members for maximum AIS extent, based on ice-sheet simulations of a late-Pleistocene and a mid-Miocene glaciation. Fundamental dynamical differences emerge as a consequence of atmospheric forcing, eustatic sea level and continental shelf evolution. We show that the AIS contributed to the amplification of its own sensitivity to ocean forcing by gradually expanding and eroding the continental shelf, that probably changed its tipping points through time. The lack of past topographic and bathymetric reconstructions implies that so far, we still have an incomplete understanding of AIS fast response to past warm climate conditions, which is crucial to constrain its future evolution.
Collapse
|
17
|
Cramwinckel MJ, Huber M, Kocken IJ, Agnini C, Bijl PK, Bohaty SM, Frieling J, Goldner A, Hilgen FJ, Kip EL, Peterse F, van der Ploeg R, Röhl U, Schouten S, Sluijs A. Synchronous tropical and polar temperature evolution in the Eocene. Nature 2018; 559:382-386. [PMID: 29967546 DOI: 10.1038/s41586-018-0272-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 04/13/2018] [Indexed: 11/09/2022]
Abstract
Palaeoclimate reconstructions of periods with warm climates and high atmospheric CO2 concentrations are crucial for developing better projections of future climate change. Deep-ocean1,2 and high-latitude3 palaeotemperature proxies demonstrate that the Eocene epoch (56 to 34 million years ago) encompasses the warmest interval of the past 66 million years, followed by cooling towards the eventual establishment of ice caps on Antarctica. Eocene polar warmth is well established, so the main obstacle in quantifying the evolution of key climate parameters, such as global average temperature change and its polar amplification, is the lack of continuous high-quality tropical temperature reconstructions. Here we present a continuous Eocene equatorial sea surface temperature record, based on biomarker palaeothermometry applied on Atlantic Ocean sediments. We combine this record with the sparse existing data4-6 to construct a 26-million-year multi-proxy, multi-site stack of Eocene tropical climate evolution. We find that tropical and deep-ocean temperatures changed in parallel, under the influence of both long-term climate trends and short-lived events. This is consistent with the hypothesis that greenhouse gas forcing7,8, rather than changes in ocean circulation9,10, was the main driver of Eocene climate. Moreover, we observe a strong linear relationship between tropical and deep-ocean temperatures, which implies a constant polar amplification factor throughout the generally ice-free Eocene. Quantitative comparison with fully coupled climate model simulations indicates that global average temperatures were about 29, 26, 23 and 19 degrees Celsius in the early, early middle, late middle and late Eocene, respectively, compared to the preindustrial temperature of 14.4 degrees Celsius. Finally, combining proxy- and model-based temperature estimates with available CO2 reconstructions8 yields estimates of an Eocene Earth system sensitivity of 0.9 to 2.3 kelvin per watt per square metre at 68 per cent probability, consistent with the high end of previous estimates11.
Collapse
Affiliation(s)
- Margot J Cramwinckel
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands.
| | - Matthew Huber
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA
| | - Ilja J Kocken
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands
| | - Claudia Agnini
- Department of Geosciences, University of Padova, Padova, Italy
| | - Peter K Bijl
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands
| | - Steven M Bohaty
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, UK
| | - Joost Frieling
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands
| | - Aaron Goldner
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA
| | - Frederik J Hilgen
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands
| | - Elizabeth L Kip
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands
| | - Francien Peterse
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands
| | - Robin van der Ploeg
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands
| | - Ursula Röhl
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Stefan Schouten
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands.,NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry and Utrecht University, Den Burg, The Netherlands
| | - Appy Sluijs
- Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands
| |
Collapse
|
18
|
Colleoni F, De Santis L, Siddoway CS, Bergamasco A, Golledge NR, Lohmann G, Passchier S, Siegert MJ. Spatio-temporal variability of processes across Antarctic ice-bed-ocean interfaces. Nat Commun 2018; 9:2289. [PMID: 29915266 PMCID: PMC6006349 DOI: 10.1038/s41467-018-04583-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 05/11/2018] [Indexed: 11/23/2022] Open
Abstract
Understanding how the Antarctic ice sheet will respond to global warming relies on knowledge of how it has behaved in the past. The use of numerical models, the only means to quantitatively predict the future, is hindered by limitations to topographic data both now and in the past, and in knowledge of how subsurface oceanic, glaciological and hydrological processes interact. Incorporating the variety and interplay of such processes, operating at multiple spatio-temporal scales, is critical to modeling the Antarctic's system evolution and requires direct observations in challenging locations. As these processes do not observe disciplinary boundaries neither should our future research.
Collapse
Affiliation(s)
- Florence Colleoni
- Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici, 40129, Bologna, Italy.
| | - Laura De Santis
- Istituto Nazionale di Oceanografia Sperimentale, 34010, Sgonico, Italy
| | | | - Andrea Bergamasco
- Centro Nazionale delle Ricerche - Istituto di Scienze Marine, 30122, Venice, Italy
| | - Nicholas R Golledge
- Antarctic Research Centre, Victoria University of Wellington, Wellington, 6140, New Zealand
- GNS Science, Avalon, Lower Hutt, 5010, New Zealand
| | - Gerrit Lohmann
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, 27570, Bremerhaven, Germany
- University of Bremen, 28359, Bremen, Germany
| | - Sandra Passchier
- Department of Earth and Environmental Studies, Center for Environmental and Life Sciences, Montclair State University, Montclair, NY, 07043, USA
| | - Martin J Siegert
- Grantham Institute and Department of Earth Science and Engineering, Imperial College of London, London, SW7 2AZ, UK
| |
Collapse
|
19
|
Shakun JD, Corbett LB, Bierman PR, Underwood K, Rizzo DM, Zimmerman SR, Caffee MW, Naish T, Golledge NR, Hay CC. Minimal East Antarctic Ice Sheet retreat onto land during the past eight million years. Nature 2018; 558:284-287. [PMID: 29899483 DOI: 10.1038/s41586-018-0155-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 03/20/2018] [Indexed: 11/09/2022]
Abstract
The East Antarctic Ice Sheet (EAIS) is the largest potential contributor to sea-level rise. However, efforts to predict the future evolution of the EAIS are hindered by uncertainty in how it responded to past warm periods, for example, during the Pliocene epoch (5.3 to 2.6 million years ago), when atmospheric carbon dioxide concentrations were last higher than 400 parts per million. Geological evidence indicates that some marine-based portions of the EAIS and the West Antarctic Ice Sheet retreated during parts of the Pliocene1,2, but it remains unclear whether ice grounded above sea level also experienced retreat. This uncertainty persists because global sea-level estimates for the Pliocene have large uncertainties and cannot be used to rule out substantial terrestrial ice loss 3 , and also because direct geological evidence bearing on past ice retreat on land is lacking. Here we show that land-based sectors of the EAIS that drain into the Ross Sea have been stable throughout the past eight million years. We base this conclusion on the extremely low concentrations of cosmogenic 10Be and 26Al isotopes found in quartz sand extracted from a land-proximal marine sediment core. This sediment had been eroded from the continent, and its low levels of cosmogenic nuclides indicate that it experienced only minimal exposure to cosmic radiation, suggesting that the sediment source regions were covered in ice. These findings indicate that atmospheric warming during the past eight million years was insufficient to cause widespread or long-lasting meltback of the EAIS margin onto land. We suggest that variations in Antarctic ice volume in response to the range of global temperatures experienced over this period-up to 2-3 degrees Celsius above preindustrial temperatures 4 , corresponding to future scenarios involving carbon dioxide concentrations of between 400 and 500 parts per million-were instead driven mostly by the retreat of marine ice margins, in agreement with the latest models5,6.
Collapse
Affiliation(s)
- Jeremy D Shakun
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA, USA.
| | - Lee B Corbett
- Department of Geology and Rubenstein School of the Environment and Natural Resources, University of Vermont, Burlington, VT, USA
| | - Paul R Bierman
- Department of Geology and Rubenstein School of the Environment and Natural Resources, University of Vermont, Burlington, VT, USA
| | - Kristen Underwood
- Civil and Environmental Engineering, University of Vermont, Burlington, VT, USA
| | - Donna M Rizzo
- Civil and Environmental Engineering, University of Vermont, Burlington, VT, USA
| | - Susan R Zimmerman
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - Marc W Caffee
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA.,Department of Physics and Astronomy, Purdue University, West Lafayette, IN, USA
| | - Tim Naish
- Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand
| | - Nicholas R Golledge
- Antarctic Research Centre, Victoria University of Wellington, Wellington, New Zealand
| | - Carling C Hay
- Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA, USA
| |
Collapse
|
20
|
Shen Q, Wang H, Shum CK, Jiang L, Hsu HT, Dong J. Recent high-resolution Antarctic ice velocity maps reveal increased mass loss in Wilkes Land, East Antarctica. Sci Rep 2018. [PMID: 29540750 PMCID: PMC5852037 DOI: 10.1038/s41598-018-22765-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
We constructed Antarctic ice velocity maps from Landsat 8 images for the years 2014 and 2015 at a high spatial resolution (100 m). These maps were assembled from 10,690 scenes of displacement vectors inferred from more than 10,000 optical images acquired from December 2013 through March 2016. We estimated the mass discharge of the Antarctic ice sheet in 2008, 2014, and 2015 using the Landsat ice velocity maps, interferometric synthetic aperture radar (InSAR)-derived ice velocity maps (~2008) available from prior studies, and ice thickness data. An increased mass discharge (53 ± 14 Gt yr-1) was found in the East Indian Ocean sector since 2008 due to unexpected widespread glacial acceleration in Wilkes Land, East Antarctica, while the other five oceanic sectors did not exhibit significant changes. However, present-day increased mass loss was found by previous studies predominantly in west Antarctica and the Antarctic Peninsula. The newly discovered increased mass loss in Wilkes Land suggests that the ocean heat flux may already be influencing ice dynamics in the marine-based sector of the East Antarctic ice sheet (EAIS). The marine-based sector could be adversely impacted by ongoing warming in the Southern Ocean, and this process may be conducive to destabilization.
Collapse
Affiliation(s)
- Qiang Shen
- State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Hansheng Wang
- State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - C K Shum
- State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China.,Division of Geodetic Science, School of Earth Sciences, The Ohio State University, Columbus, Ohio, 43210, USA
| | - Liming Jiang
- State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hou Tse Hsu
- State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jinglong Dong
- State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| |
Collapse
|
21
|
Ma H, Yan W, Xiao X, Shi G, Li Y, Sun B, Dou Y, Zhang Y. Ex Situ Culturing Experiments Revealed Psychrophilic Hydrogentrophic Methanogenesis Being the Potential Dominant Methane-Producing Pathway in Subglacial Sediment in Larsemann Hills, Antarctic. Front Microbiol 2018. [PMID: 29515536 PMCID: PMC5826372 DOI: 10.3389/fmicb.2018.00237] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
It was recognized only recently that subglacial ecosystems support considerable methanogenic activity, thus significantly contributing the global methane production. However, only limited knowledge is available on the physiological characteristics of this kind of methanogenic community because of the technical constraints associated with sampling and cultivation under corresponding environmental conditions. To elucidate methanogenesis beneath the glacial margin in East Antarctic Ice Sheet, we took an integrated approach that included cultivation of microbes associated with the sediment samples in the lab and analysis of mcrA gene therein. After 7 months of incubation, the highest rate of methanogenesis [398 (pmol/day)/gram] was observed at 1°C on a supply of H2. The rates of methanogenesis were lower on acetate or unamended substrate than on H2. The rates on these two substrates increased when the temperature was raised. Methanomicrobiales predominated before and after prolonged incubation, regardless whether H2, acetate, or unamended substrate were the energy source. Therefore, it was inferred that psychrophilic hydrogenotrophic methanogenesis was the primary methane-producing pathway in the subglacial ecosystem we sampled. These findings highlight the effects of temperature and substrate on potential methanogenesis in the subglacial sediment of this area, and may help us for a better estimation on the Antarctica methane production in a changing climate.
Collapse
Affiliation(s)
- Hongmei Ma
- SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, China
| | - Wenkai Yan
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Xiang Xiao
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Guitao Shi
- SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, China
| | - Yuansheng Li
- SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, China
| | - Bo Sun
- SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, China
| | - Yinke Dou
- College of Electrical and Power Engineering, Taiyuan University of Technology, Taiyuan, China
| | - Yu Zhang
- State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, China.,Institute of Oceanography, Shanghai Jiao Tong University, Shanghai, China
| |
Collapse
|
22
|
Greenwood S. Antarctic ice dynamics in warm climates. Nature 2017; 552:183-184. [PMID: 29239370 DOI: 10.1038/d41586-017-08285-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|