The mystery of what started the last ice age may have been solved – Two mysteries have been a headache for many paleoclimate experts: where did the ice sheets of the last ice age come from and how did they pushed so quickly? A new study published in Nature Geoscience may have solved these mysteries, offering an explanation. These findings could also be applied to other historical ice ages.
The last glacial cycle began 116,000 years ago and a huge ice sheet covered the northern hemisphere. However, these leaves only took 10,000 years to grow and coalesce, which surprised scientists.
Scientists have already struggled to explain the vast ice sheets that covered warmer northern Europe and Scandinavia – warm water brought in by the North Atlantic Current should have made Scandinavia largely ice-free.
"The problem is that we don't know where these ice sheets (in Scandinavia) came from and what caused them to expand in such a short time," lead author Marcus Lofverstrom said in a statement.
The study authors developed a complex model of the Earth system called the Community Earth System Model. This model could recreate the early climatic conditions of the recent ice age with a high level of spatial detail.
Researchers have discovered that the ocean gateways of the Canadian Arctic Archipelago are critical to controlling the North Atlantic climate. This gateway then made it possible to decide whether the ice sheets in Scandinavia developed or not. The models revealed that as long as the Canadian Arctic Archipelago remained open, the northern hemisphere was sufficiently cooled by Earth's orbital configuration to allow ice sheets to form in northern Canada and Siberia.
The research team also examined whether marine ice sheets were obstructing waterways in the Canadian Arctic archipelago. Normally, fresh waste from the Arctic and North Pacific is routed via the Canadian Arctic Archipelago – in this scenario, it was actually diverted east of Greenland. The diversion caused a weakening and cooling of the North Atlantic deep circulation, cooler conditions in Scandinavia and an expansion of sea ice.
/"Using both climate model simulations and marine sediment analyses, we show that ice formation in northern Canada can obstruct ocean gateways and divert water transport from the Arctic to the Atlantic North," Lofverstrom said, "and that in turn leads to a weakened ocean circulation and cold conditions off the Scandinavian coast, which is enough to start growing ice in that region./"
“These results are supported by marine sediment records from the North Atlantic, which show traces of glaciers in northern Canada several thousand years before the European part,” said Diane Thompson, author of the study. /"The sedimentary records also show compelling evidence of weakened deep ocean circulation before the formation of glaciers in Scandinavia, similar to our modeling results./"
Overall, the experiments may suggest that the formation of sea ice in northern Canada was necessary for the formation of Scandinavian glaciers.
"It's possible that the mechanisms we identified here apply to every ice age, not just the most recent one," Lofverstrom said. /"It may even help explain shorter-lived cold periods such as the cold reversal of the Younger Dryas (12,900 to 11,700 years ago) that punctuated the general warming at the end of the last ice age ./"
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