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A Reconstruction of the Coastal Antarctic Climate and Summer Sea-Ice Position at 18 ka BP (Abstract)

Published online by Cambridge University Press:  20 January 2017

David H. Bromwich
David H. Bromwich*
Affiliation:
Institute of Polar Studies, Ohio State University, Columbus, Ohio 43210, U.S.A.
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Abstract

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Abstract
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Annals of Glaciology , Volume 5 , 1984 , pp. 201
Copyright
Copyright © International Glaciological Society 1984

The results of an investigation of the oxygen-isotope composition in present-day Antarctic snowfall (Reference Bromwich and WeaverBromvich and Weaver 1983) are assumed to apply at the last glacial maximum, and the resulting coastal climate is derived. Inputs are the observed change in δ180 from ice cores (Reference Lorius, Merlivat, Jouzel and PourchetLorius and others 1979), the extent of winter sea ice at 18 ka BP inferred from ocean sediment cores (Reference Hays, Lozano, Shackleton and IrvingHays and others 1976), and the present-day connections between sea-ice extent and both temperature and δ180 in coastal precipitation. The following variables are calculated: the annual, summer, and winter surface air temperatures, the summer and winter δ180 values in precipitation, and the summer sea-ice extent, all for 18 ka BP.

Contrary to expectation, the derived 18 ka BP summer sea-ice extent and coastal air temperatures are approximately the same as at present. Accompanying the much larger winter sea-ice, the glacial July air temperature is found to be about 15°C cooler. Annual temperatures are about 7°C lower. The derived results imply a much more marked seasonality and a much larger cycle of sea-ice growth and decay.

Some observational evidence in support of these findings is available. The glacial summer sea-ice position is in general agreement with new ocean sediment interpretations (Reference Burckle, Robinson and CookeBurckle and others 1982) which suggest that the pack ice retreated close to the Antarctic continent in many years (personal communication from L H Burckle 1983). Perched deltas in Taylor Valley, which are 14C-dated to 18 ka BP (Reference Stuiver, Denton, Hughes, Fastook, Denton and HughesStuiver and others 1981), imply the presence of liquid water; in turn this may reflect relatively warm summer temperatures. Ice cores show a substantially larger “seasonal” variation in microparticle deposition onto the Antarctic ice sheet during the last glacial maximum (Reference Thompson and Mosley-ThompsonThompson and Hosley-Thompson 1981).

References

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Burckle, L H, Robinson, D, Cooke, D 1982 Reappraisal of sea-ice distribution in Atlantic and Pacific sectors of the Southern Ocean at 18,000 yr BP. Datum 299(5882): 435–437 Google Scholar
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