Scientist contributes to study explaining prehistoric ice sheet

By Robert Emro, CEPS

A UNH researcher has helped devise an explanation for a scientific mystery that, if confirmed, will aid efforts to understand the forces at work in the Earth’s climate system.

The researchers believe that huge lakes – together more than twice as large as the Caspian Sea – enhanced the formation of a giant ice sheet that covered the Russian Arctic 90,000 years ago.

Martin Jakobsson, a research scientist with the UNH Center for Coastal and Ocean Mapping, co-authored a paper detailing the findings in the Jan. 29 issue of the journal Nature.

Explaining how climate behaved in the past is crucial to explaining how it is likely to behave in the future – a question of overarching importance given the current trend toward global warming. “The overall theme that is behind much of what paleogeologists like us do,” explained Jakobsson, “is trying to understand with the greatest accuracy what happened in the past so that people trying to determine what will happen in the future will have the best possible information.”

Scientists have long known that a huge ice sheet was centered over the Barents and Kara seas, stretching from Scandinavia in the west to Siberia in the east, but they did not know how it grew to be so large. “It’s very hard to explain the very large ice sheets in these areas. It’s very dry in this area otherwise,” said Jakobsson.

The international team of researchers from France, Belgium, Norway and the United States concluded that huge lakes – created when the Barents-Kara ice sheet grew large enough to dam the major north flowing rivers in what is present-day Russia – had a cooling effect on the regional climate, allowing the ice sheet to grow larger than it otherwise would have.

By reducing melting during the summer, the cooling effect caused by the lakes allowed the ice sheet to grow by leaps and bounds, rather than just a small amount every year.

“What we see in the past is that we have drastic climate changes, and synergistic effects such as these help explain why,” said Jakobsson.
While his colleagues were in the frigid Russian Arctic looking for the boundaries of the ancient lakes, Jakobsson’s job was to fill in the gaps by digitally reconstructing the lakes where no sign of them remained.

The image he created showing the lakes and the ice sheet appears on the cover of Nature. “It’s been a very nice team, because we’ve all had a small part,” he said. “The people in Europe have been working in the field for years and years while I’ve been in front of the computer.”