A warm climate in northern Europe can be hit by a sudden cooling leading to an Ice Age associated with an interruption of the North Atlantic Ocean circulation and the Gulf Stream, a new record of past climate change shows.

The study, published in Quaternary Science Reviews, looked into the development of northern European climate during the last inter-glacial period about 120 thousand years ago.

The investigated time interval, called the Eemian, occurred before the last Ice Age and was characterized by warmer-than-present temperatures in large parts of the globe.

The Eemian climate evolution can therefore serve as an analogue for a future warmer climate.

The study of fossil remains, such as plants and insects, preserved in geological deposits in northern Finland revealed an abrupt climatic cooling event that happened in an otherwise warmer climate.

During this event the temperatures dropped 2–4°C and remained low for a period of 500–1000 years.

Comparison with seaf loor sediment records from the Norwegian Sea and the North Atlantic indicates that the rapid cooling was associated with a sudden slowdown in North Atlantic deep water formation and a reduction in the northward extension of the Gulf Stream that transports heat to northern Europe.

The new evidence shows that the last time when temperatures were significantly warmer than today, climate instability occurred.

“This may have been caused by melt water coming from the Greenland Ice Sheet, disrupting the North Atlantic Ocean circulation,” Karin Helmens at the Department of Physical Geography, Stockholm University, said. “While the exact mechanism behind the sudden cooling still remains uncertain, the study illustrates the potential for major climatic instability in and around the North Atlantic region under future global warming”

The study was performed by an international research group led by Dr. Karin Helmens from Stockholm University and Bolin Centre for Climate Research (Sweden).

The group also includes scientists from the University of Helsinki (Finland), University of Bergen and Bjerknes Centre for Climate Research (Norway), and VU University Amsterdam and University of Amsterdam (The Netherlands).