Climate change models are only as good as the assumptions plugged into them. Findings published in the December Science could lead those models to predict faster ice melt, and therefore rising sea levels worse than currently foreseen.
Scientists have long had good characterizations of the historical spread and retreat of the ice sheet capping the northern hemisphere. But the dimensions and timing of changes to the Antarctic ice cap emerge clearly for the first time in the studies published this month.
The researchers were surprised to find that at the end of the last ice age, the southern ice cap was melting in sync with the retreat of northern ice, challenging the assumption that climatic isolation protects the Antarctic ice somewhat even as the Arctic caps shrink to record low levels.
"The decline in the Antarctic ice sheets thus commenced almost 5,000 years earlier than assumed to date," according to Dr. Michael Weber from the Geological Institute of the University of Cologne, lead author of the study.
The team behind this study suspects that changes in deepwater circulation carry warm waters to the continental margin of the Antarctic, suggesting a heretofore unsuspected instability in the southern ice cap. Dr. Weber concludes:
Forecasts of the future rise in the sea level caused by climate change will also have to be adjusted accordingly.
The comparative study of climate change history relies on data carefully preserved in archives, including from core samples taken as far back as 1987. This underscores the importance of wide access to high-quality scientific databases for researchers reconstructing climate patterns in hopes of better predicting the future effects of climate change.
The international research team was coordinated by Dr. Gerhard Kuhn of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association, and involved scientists from Oregon State University and Harvard as well as the University of Cologne.
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