Last Ice Age: Ancient Scandinavian Lake Sediments Provide Missing Puzzle Piece

Melting Scandinavian ice may provide the final piece to one of the most difficult puzzles concerning the last Ice Age. While it is believed a catastrophic freshwater flood from melting North American ice sheets resulted in a sudden and final cold snap 13,000 years ago, just before the present warm interglacial period, new evidence helps explain what really happened at the end of the last Ice Age.

Researchers from Stockholm University, Plymouth University and the Natural History Museum (NHM) London recently uncovered moisture-sensitive molecules in the sediment of an ancient Swedish lake, which represent the melting of the Scandinavian ice sheet and indicate climate conditions in Northern Europe became much drier than previously thought 13,000 years ago, according to a news release.

"The remains of midges, contained in the lake sediments, reveal a great deal about the past climate," Steve Brooks, a researcher from the NHM, explained. "The assemblage of species, when compared with modern records, enable us to track how, after an initial warming of up to four degrees Centigrade at the end of the last Ice Age, summer temperatures plummeted by five degrees Celsius over the next 400 years."

Researchers believe that the onset of colder and drier climate conditions was most likely driven by an increased melting of the Scandinavian Ice Sheet, which was triggered by warming at the end of the last Ice Age. Essentially, this led to changes in sea-ice distribution and, as a result, abrupt climate change.

"The melting of the Scandinavian ice sheet is the missing link to understanding current inconsistencies between climate models and reconstructions, and our understanding of the response of the North Atlantic system to climate change," Francesco Muschitiello, a Ph.D. researcher at Stockholm University and lead author of the study, added.

They confirmed their findings by incorporating freshwater from the Scandinavian Ice Sheet into climate models. In doing so, the associated climate shifts lined up with climate reconstructions. Their study was recently published in the journal Nature Communications.

"The Scandinavian ice sheet definitely played a much more significant role in the onset of this final cold period than previously thought," Professor Barbara Wohlfarth, project leader from Stockholm University, concluded. "Our teamwork highlights the importance of paleoclimate studies, not least in respect to the ongoing global warming debate."

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