Suchergebnisse

The future response of the Antarctic ice sheet to rising temperatures remains highly uncertain. A useful period for assessing the sensitivity of Antarctica to warming is the Last Interglacial (LIG) (129 to 116 ky), which experienced warmer polar temperatures and higher global mean sea level (GMSL) (+6 to 9 m) relative to present day. LIG sea level cannot be fully explained by Greenland Ice Sheet melt (similar to 2 m), ocean thermal expansion, and melting mountain glaciers (similar to 1 m), suggesting substantial Antarctic mass loss was initiated by warming of Southern Ocean waters, resulting from a weakening Atlantic meridional overturning circulation in response to North Atlantic surface freshening. Here, we report a blue-ice record of ice sheet and environmental change from the Weddell Sea Embayment at the periphery of the marine-based West Antarctic Ice Sheet (WAIS), which is underlain by major methane hydrate reserves. Constrained by a widespread volcanic horizon and supported by ancient microbial DNA analyses, we provide evidence for substantial mass loss across the Weddell Sea Embayment during the LIG, most likely driven by ocean warming and associated with destabilization of subglacial hydrates. Ice sheet modeling supports this interpretation and suggests that millennial-scale warming of the Southern Ocean could have triggered a multimeter rise in global sea levels. Our data indicate that Antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice-climate feedbacks that further amplify warming. ; Australian Research Council Royal Society of New Zealand Linkage Partner Antarctic Logistics and Expeditions LP120200724 NERC Natural Environment Research Council NE/I027576/1 Coleg Cymraeg Cenedlaethol European Research Council (ERC) Fulbright Commission 259253 Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of Science Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) 15KK0027 17H06320 Australian Government

Increased Southern Ocean productivity driven by sea-ice feedbacks contributed to a slowdown in rising CO(2)levels during the last deglaciation, according to analyses of marine-derived aerosols from an Antarctic ice core. The Southern Ocean occupies 14% of the Earth's surface and plays a fundamental role in the global carbon cycle and climate. It provides a direct connection to the deep ocean carbon reservoir through biogeochemical processes that include surface primary productivity, remineralization at depth and the upwelling of carbon-rich water masses. However, the role of these different processes in modulating past and future air-sea carbon flux remains poorly understood. A key period in this regard is the Antarctic Cold Reversal (ACR, 14.6-12.7 kyrbp), when mid- to high-latitude Southern Hemisphere cooling coincided with a sustained plateau in the global deglacial increase in atmospheric CO2. Here we reconstruct high-latitude Southern Ocean surface productivity from marine-derived aerosols captured in a highly resolved horizontal ice core. Our multiproxy reconstruction reveals a sustained signal of enhanced marine productivity across the ACR. Transient climate modelling indicates this period coincided with maximum seasonal variability in sea-ice extent, implying that sea-ice biological feedbacks enhanced CO(2)sequestration and created a substantial regional marine carbon sink, which contributed to the plateau in CO(2)during the ACR. Our results highlight the role Antarctic sea ice plays in controlling global CO2, and demonstrate the need to incorporate such feedbacks into climate-carbon models. ; Australian Research Council Royal Society of NZ fellowships Linkage Partner Antarctic Logistics and Expeditions LP120200724 Australian Climate Change Science Program (ACCSP), an Australian Government Initiative Coleg Cymraeg Cenedlaethol European Research Council (ERC) 25923 German Research Foundation (DFG) We2039/8-1 Keele University