Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination

Fogwill, Chris, Turney, Chris, Golledge, Nick, Etheridge, D. M., Rubino, M., Thornton, D. P., Baker, Andy, Woodward, John, Winter, Kate, van Ommen, Tas, Moy, Andrew, Curran, Mark, Davies, Siwan, Weber, Michael, Bird, M. I., Munksgaard, Niels, Menviel, Laurie, Rootes, Camilla, Ellis, Bethany, Millman, Helen, Vohra, J., Rivera, Andrés and Cooper, Alan (2017) Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination. Scientific Reports, 7. p. 39979. ISSN 2045-2322

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Abstract

Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved ‘horizontal ice core’ from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600–12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise.

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