24 February 2005
Cool effects of warmth
The onset of glaciation in the Northern Hemisphere during the Late Cenozoic ice age, 2.7 million years ago, was one of the most dramatic climate shifts on record, but its causes are not yet clear. Changes in North Atlantic circulation that were once thought to be a factor are now known to have occurred long before the glaciation. New palaeoceanographic data, combined with the results of a climate model, indicate that changes in the subarctic North Pacific may have driven this climate transition. A stronger seasonality in the North Pacific, the major source of atmospheric water vapour upstream of the North American continent, seems to have initiated Northern Hemisphere glaciation by inducing warming in late summer and autumn thus increasing the amount of water available to fall as snow.
North Pacific seasonality and the glaciation of North America 2.7 million years ago
GERALD H. HAUG, ANDREY GANOPOLSKI, DANIEL M. SIGMAN, ANTONI ROSELL-MELE, GEORGE E. A. SWANN, RALF TIEDEMANN, SAMUEL L. JACCARD, JÖRG BOLLMANN, MARK A. MASLIN, MELANIE J. LENG & GEOFFREY EGLINTON
Nature 433, 821–825 (2005); doi:10.1038/nature03332
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Climate change: Snow maker for the ice ages
KATHARINA BILLUPS
In the Northern Hemisphere, large-scale glaciation was initiated comparatively recently. Paradoxically, it seems that the trigger was a seasonal warming of the sea surface in an upwind oceanic region.
Nature 433, 809–810 (2005); doi:10.1038/433809a
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