Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures
Oxygen isotopes from ocean sediments (δ18O) used to reconstruct past continental ice volumes additionally record deep water temperatures (DWTs). Traditionally, these are assumed to be coupled (ice-volume changes cause DWT changes). However, δ18O records during peak Middle Miocene warmth (~16–15 mill...
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Online Access: | https://hdl.handle.net/11250/2831807 https://doi.org/10.1038/s41561-021-00745-w |
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ftnorce:oai:norceresearch.brage.unit.no:11250/2831807 2023-05-15T13:37:33+02:00 Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures Bradshaw, Catherine Langebroek, Petra Lear, Caroline H. Lunt, Daniel J. Coxall, Helen Sosdian, Sindia M. De Boer, Agatha 2021 application/pdf https://hdl.handle.net/11250/2831807 https://doi.org/10.1038/s41561-021-00745-w eng eng urn:issn:1752-0894 https://hdl.handle.net/11250/2831807 https://doi.org/10.1038/s41561-021-00745-w cristin:1910391 Navngivelse 4.0 Internasjonal http://creativecommons.org/licenses/by/4.0/deed.no CC-BY Nature Geoscience Peer reviewed Journal article 2021 ftnorce https://doi.org/10.1038/s41561-021-00745-w 2022-10-13T05:50:48Z Oxygen isotopes from ocean sediments (δ18O) used to reconstruct past continental ice volumes additionally record deep water temperatures (DWTs). Traditionally, these are assumed to be coupled (ice-volume changes cause DWT changes). However, δ18O records during peak Middle Miocene warmth (~16–15 million years ago) document large rapid fluctuations (~1–1.5‰) difficult to explain as huge Antarctic ice sheet (AIS) volume changes. Here, using climate modelling and data comparisons, we show DWTs are coupled to AIS spatial extent, not volume, because Antarctic albedo changes modify the hydrological cycle, affecting Antarctic deep water production regions. We suggest the Middle Miocene AIS had retreated substantially from previous Oligocene maxima. The residual ice sheet varied spatially more rapidly on orbital timescales than previously thought, enabling large DWT swings (up to 4 °C). When Middle Miocene warmth terminated (~13 million years ago) and a continent-scale AIS had stabilized, further ice-volume changes were predominantly in height rather than extent, with little impact on DWT. Our findings imply a shift in ocean sensitivity to ice-sheet changes occurs when AIS retreat exposes previously ice-covered land; associated feedbacks could reduce the Earth system’s ability to maintain a large AIS. This demonstrates ice-sheet changes should be characterized not only by ice volume but also by spatial extent. publishedVersion Article in Journal/Newspaper Antarc* Antarctic Ice Sheet NORCE vitenarkiv (Norwegian Research Centre) Antarctic Nature Geoscience 14 6 429 436 |
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NORCE vitenarkiv (Norwegian Research Centre) |
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ftnorce |
language |
English |
description |
Oxygen isotopes from ocean sediments (δ18O) used to reconstruct past continental ice volumes additionally record deep water temperatures (DWTs). Traditionally, these are assumed to be coupled (ice-volume changes cause DWT changes). However, δ18O records during peak Middle Miocene warmth (~16–15 million years ago) document large rapid fluctuations (~1–1.5‰) difficult to explain as huge Antarctic ice sheet (AIS) volume changes. Here, using climate modelling and data comparisons, we show DWTs are coupled to AIS spatial extent, not volume, because Antarctic albedo changes modify the hydrological cycle, affecting Antarctic deep water production regions. We suggest the Middle Miocene AIS had retreated substantially from previous Oligocene maxima. The residual ice sheet varied spatially more rapidly on orbital timescales than previously thought, enabling large DWT swings (up to 4 °C). When Middle Miocene warmth terminated (~13 million years ago) and a continent-scale AIS had stabilized, further ice-volume changes were predominantly in height rather than extent, with little impact on DWT. Our findings imply a shift in ocean sensitivity to ice-sheet changes occurs when AIS retreat exposes previously ice-covered land; associated feedbacks could reduce the Earth system’s ability to maintain a large AIS. This demonstrates ice-sheet changes should be characterized not only by ice volume but also by spatial extent. publishedVersion |
format |
Article in Journal/Newspaper |
author |
Bradshaw, Catherine Langebroek, Petra Lear, Caroline H. Lunt, Daniel J. Coxall, Helen Sosdian, Sindia M. De Boer, Agatha |
spellingShingle |
Bradshaw, Catherine Langebroek, Petra Lear, Caroline H. Lunt, Daniel J. Coxall, Helen Sosdian, Sindia M. De Boer, Agatha Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures |
author_facet |
Bradshaw, Catherine Langebroek, Petra Lear, Caroline H. Lunt, Daniel J. Coxall, Helen Sosdian, Sindia M. De Boer, Agatha |
author_sort |
Bradshaw, Catherine |
title |
Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures |
title_short |
Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures |
title_full |
Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures |
title_fullStr |
Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures |
title_full_unstemmed |
Hydrological impact of Middle Miocene Antarctic ice-free areas coupled to deep ocean temperatures |
title_sort |
hydrological impact of middle miocene antarctic ice-free areas coupled to deep ocean temperatures |
publishDate |
2021 |
url |
https://hdl.handle.net/11250/2831807 https://doi.org/10.1038/s41561-021-00745-w |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic Ice Sheet |
genre_facet |
Antarc* Antarctic Ice Sheet |
op_source |
Nature Geoscience |
op_relation |
urn:issn:1752-0894 https://hdl.handle.net/11250/2831807 https://doi.org/10.1038/s41561-021-00745-w cristin:1910391 |
op_rights |
Navngivelse 4.0 Internasjonal http://creativecommons.org/licenses/by/4.0/deed.no |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1038/s41561-021-00745-w |
container_title |
Nature Geoscience |
container_volume |
14 |
container_issue |
6 |
container_start_page |
429 |
op_container_end_page |
436 |
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1766093873524768768 |