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Birmingham scientists have contributed to a new study on ice cores which shows that reductions in sea ice in the Arctic in the period between 30-100,000 years ago led to major climate events.

During this period, Greenland temperatures rose by as much as 16 degrees Celsius. The results are published this week (Monday 11 February) in Proceedings of the National Academy of Sciences (PNAS).

A team from British Antarctic Survey (BAS), University of Cambridge and University of Birmingham studied data from ice cores drilled in Greenland. They looked at oxygen isotopes and compared them to climate models run on the ARCHER supercomputer1. From this they determined that sea ice changes were massively significant in past climate change events in the North Atlantic. These periods, called Dansgaard-Oeschger events2, are some of the fastest and largest abrupt climate changes ever recorded. During some of these events, Greenland temperatures are likely to have increased by 16 degrees Celsius in less than a decade.

This work confirms a major significance of sea ice for past abrupt warming events. This is important because changes in sea ice have profound consequences on both global and local scales, including impacts on global climate and local ecosystems.  Accurate forecasts of Arctic sea ice over the coming decades to centuries are crucial to understanding how the earth will respond to any changes.

Impact of abrupt sea ice loss on Greenland water isotopes during the last glacial period by Louise C. Sime, Peter O. Hopcroft, Rachael H. Rhodes is published in the Proceedings of the National Academy of Sciences.

1.The researchers’ numerical model simulations were run on the large ARCHER supercomputer. ARCHER is based around a Cray XC30 supercomputer and is provided by EPSRC, NERC, EPCC, Cray Inc. and The University of Edinburgh. The simulations were run over the course of two years and were compared to ice core data that has been collected over the last twenty to thirty years.

2.Dansgaard-Oeschger events are rapid climate fluctuations that occurred about 25 times during the last glacial period. They are named after Willi Dansgaard who was a Danish paleoclimatologist (1922-2011) and Hans Oeschger (1927-1998), another paleoclimatologist, who jointly identified them in Greenland ice core records.