1. Widespread southern elephant seal occupation of the Victoria land coast implies a warmer-than-present Ross Sea in the mid-to-late Holocene.
- Author
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Hall, Brenda L., Koch, Paul L., Baroni, Carlo, Salvatore, Maria Cristina, Hoelzel, A. Rus, de Bruyn, Mark, and Welch, Andreanna J.
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SEA ice , *GLACIERS , *OCEAN temperature , *ANTARCTIC ice , *LAST Glacial Maximum , *ICE shelves , *HOLOCENE Epoch - Abstract
Prediction of future ice-sheet behavior in Antarctica and its contribution to sea-level rise depends on accurate understanding of ice-sheet response to a warm climate. Examination of how the ice sheet reacted to past warm episodes affords a means of assessing its tolerances to climate change. The West Antarctic Ice Sheet (WAIS), in particular, is thought to be highly susceptible to variations in ocean temperature at its grounding lines. Yet, detailed records of past ocean temperatures close to the continent are rare. Here, we present a record of past relative ocean-temperature and sea-ice change derived from the presence and then eventual abandonment of southern elephant seal (Mirounga leonina) occupation sites along the Victoria Land Coast (VLC) of the western Ross Embayment. Our results suggest greatly reduced landfast and likely pack ice, as well as potentially the incursion of relatively warm modified Circum-Polar Deep Water from ∼7100 to 500 yr BP, with the greatest reduction in ice/warmest water temperatures at ∼5200 and ∼2300-1800 yr BP. These changes in ocean conditions would have had a strong influence on VLC marine-terminating glaciers through variations in buttressing sea ice and melt rates on the underside of floating ice. Independent data suggest that these glaciers had restricted extent in the mid-Holocene, consistent with our inference of warm ocean temperatures and low sea ice. The glaciers subsequently expanded within the last millennium, coincident with the disappearance of southern elephant seals from the coast and the inferred return to icy conditions. Our relative sea-ice and ocean-temperature reconstruction also is consistent with the hypothesized retreat of the WAIS inland of its present position in the mid to late Holocene, although the distance between our sites and the current WAIS grounding lines is large (600–1000 km), and thus any linkage is speculative at present. Finally, limited pre-Holocene southern elephant seal data support the existence of warm ocean temperatures immediately prior to and perhaps even during build-up to the Last Glacial Maximum (LGM) ice position. If this could be confirmed, it would suggest that factors other than ocean temperatures, such as lowered sea level, might have been critical in causing ice-sheet advance in the Ross Embayment at the LGM. • Molted skin and remains show southern elephant seals once occupied the Ross Sea. • 305 radiocarbon dates show colonies on the Victoria Land Coast ∼7000-500 yr BP. • The colonies indicate reduced landfast sea ice at several times in the Holocene. • We attribute low sea ice to incursion of circumpolar deepwater into the Ross Sea. • Colony abandonment ∼1000 yr BP was accompanied by sea ice and glacier advance. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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