Melting polar ice caps make Africa "wet"

Direct relationship between polar and tropical climate proven

This excerpt from the study shows an example: between 12, 900 and 11, 600 years ago, there was a cold spell in Greenland, and in return, rainfall in West Africa fell rapidly. © Weldab
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Climate changes at the poles have a direct effect on the temperature and precipitation in the tropics via the atmosphere: when warmer in the north, it will become humid in the tropics within a very short time and, conversely, Africa will dry out rapidly when the temperature at the north pole drops sharply, This has now been proven by researchers in Kiel, by reconstructing the water cycle of the West African monsoon of the last 155, 000 years.

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For the first time, geologists used a method in their study of how they report on climate change in the past in the current issue of Science. They were based on a 37-meter drill core taken in 2003 from the ocean floor of the Gulf of Guinea at the Niger and Sanagam√ľndungen of the Kiel Research Group. It contains calcareous shells of foraminifera, a plankton group that floats on the ocean surface and accumulates and stratifies along the sea floor over the centuries.

These fossils - more precisely, the ratio of barium to calcium in their shell - reveal the amount of fresh water that has been introduced from the rivers into the Gulf of Guinea: the higher the barium content, the more water the rivers flowed - a direct indicator of rain or drought so.

Extreme precipitation reversals within 40 to 50 years

The researchers then compared the data obtained with those already documented by Northern Greenland ice cores and noted that extreme precipitation reversals in West Africa occurred within 40 to 50 years, following climate changes in polar ice. A higher temporal resolution may prove even faster climatic swings, suspected the geologist Syee Weldeab of the Leibniz Institute of Marine Sciences (IFM-GEOMAR) at the University of Kiel. display

"So far it has been assumed that precipitation in West Africa is mainly determined by solar radiation over the continent. Although this is correct, we are now for the first time providing clear evidence that the monsoon precipitation is also very sensitive to the short-term developments of the ice sheets in the polar regions. This seems to be the case especially in warm periods - comparable to today's climatic situation. "

Sample of foraminifera. By means of the limestone housing of these tiny, up to half a millimeter-sized marine organisms, the Kiel scientists were able to draw conclusions about the West African climate. CAU / Haacks

What that means for the future climate is summarized by Professor Ralph Schneider from the Cluster of Excellence "Future Ocean": "If the climate changes so abruptly from very wet to very dry or vice versa, there are f There is hardly any time for the ecosystems to adapt. Thus, long-term or local forms of life, but also agriculture, have great difficulty keeping pace with such climates. "

Ocean of the future

The Cluster "Ocean of the Future" is an association of 120 Kiel scientists from 20 institutes of the Christian Albrechts University, the Leibniz Institute for Marine Sciences (IFM-GEOMAR), the Institute for World Economy ( IfW) and the Muthesius College of Art. The scientists' work aims to further explore the ocean and develop a marine management system that ultimately leads to a new symbiosis between humans and the sea.

(idw - University of Kiel, 01.06.2007 - DLO)