The last glacial period from 70 000 to 10 000 years ago was punctuated by abrupt climate changes, switching within a few decades between warm and cold stages that lasted for a few thousand years. These abrupt changes are intensively studied in order to improve our knowledge about the climate system behavior and especially to provide insights into how system responses and interactions can be expected to occur in the future. In a new study, which appeared in the journal Nature Geoscience, scientists from the Netherlands and Germany suggest that the rapid glacial cooling events in the North Atlantic region are an expression of dramatic winter conditions rather than a reflection of summer cooling.

Abrupt glacial climate changes have first been documented in great detail in Greenland ice cores and demonstrate how large and rapid these changes were: the annual average air temperature warmed by up to 16º C within two to three decades. These abrupt changes are related to changes in the Atlantic meridional overturning circulation. During periods of increased meltwater influx from the continental ice sheets, deepwater formation in the North Atlantic ceased with the consequence that the northward heat transfer to the high northern latitudes was dramatically reduced. In consequence, these areas cooled. Based on the recognition of these cooling events a scenario evolved in which a reduction of the overturning circulation in response to global warming and sea surface salinity reduction may have eventually lead to severe cooling in NW-Europe in the future.