Potsdam,
23 Feb. 2005
Where Does the North Pole Ice Come From?
The Origin of the Northern Hemisphere Ice Age
Large areas of the Northern Hemisphere are currently covered with ice. This has, however, not always been the case. In the current issue of the science magazine "Nature", scientists from the GeoForschungsZentrum Potsdam (GFZ) and the Potsdam Institute for Climate Impact Research (PIK) present a possible solution for the oldest mystery of palaeo climate research - how the ice age developed in the Northern Hemisphere some 2.7 million years ago.
Two preconditions are necessary for ice shields to grow: first, the polar regions need to be sufficiently cold so that precipitation can turn into snow. Second, precipitation needs to be high enough so that snowfall in winter exceeds melting in summer. Palaeoclimatic data show that the Northern Hemisphere has been sufficiently cold for glaciers to grow for 14 million years. So why did the great glaciation in the Northern Hemisphere start only 2.7 million years ago?
The current study by the Potsdam scientists shows that the oceanic circulation changed dramatically 2.7 million years ago. New climate data and model calculations reveal that the upper layer of the sub-arctic North Pacific became more stratified leading to larger seasonal differences in the North Pacific sea surface temperatures. The warmer ocean in autumn maximized evaporation and the colder winters and springs ensured that the resulting additional snow did not melt. Thus, the North Pacific is the decisive source of humidity for the American ice shield and the entire Northern Hemisphere.
After the beginning of the ice age approx 2.7 million years ago, the Earth cooled down dramatically. A permanent ice cap coated from then on the Northern Polar regions, and ice shields of several kilometres thickness covered not only Greenland but also large parts of Scandinavia, North Asia and Northern America. Since then, the pulsation of climate levelled off to a continuous change between warm and cold periods with rather low temperatures in general.
Original article:
Haug, G. H.; Ganopolski, A.; Sigman, D. M.; Rosell-Mele, A.; Swann, G. E. A.; Tiedemann, R.; Jaccard, S. L.; Bollmann, J.; Maslin, M. A.; Leng, M. J.; Eglinton, G. (2005): North Pacific seasonality and the glaciation of North America 2.7 million years ago. Nature, 433, 821-825.
Contact:
GFZ, Prof. Dr. Gerald Haug, Tel. +49/331/288-1330, E-Mail haug@gfz-potsdam.de
PIK, Dr. Andrey Ganopolski, Tel. +49/331/288-2594, E-Mail andrey.ganopolski@pik-potsdam.de
Press office:
GFZ, Franz Ossing, Tel. +49 331 288-1040, E-Mail ossing@gfz-potsdam.de
PIK, Anja Wirsing, Tel. +49 331 288-2507, E-Mail press@pik-potsdam.de
