About 100,000 years ago, the Northern Hemisphere climate plunged into a deep freeze that allowed massive ice sheets to form. Over a period of about 10,000 years, local mountain glaciers grew and formed large ice sheets covering much of today’s Canada, northern Europe and Siberia.
It has been widely accepted that periodic “wobbling” in the Earth’s orbit around the sun triggered cooling in the Northern Hemisphere summer that caused the start of widespread glaciation but scientists have struggled to explain the extensive ice sheets covering much of Scandinavia and northern Europe, where temperatures are much more mild.
“The problem is we don’t know where those ice sheets (in Scandinavia) came from and what caused them to expand in such a short amount of time,” said the study’s lead author Marcus Lofverstrom.
To solve this problem, Lovverstrom helped develop an extremely comlex Earth-system model, known as the Community Earth System Model, which allowed his team to realistically recreate the conditions that existed at the beginning of the most recent glacial period. Primarily, he expanded the ice-sheet model area from Greenland to cover most of the Northern Hemisphere in high spatial detail. Using this model, the researchers identified the ocean gateways in the Canadian Arctic Archipelago as a critical factor controlling the North Atlantic climate and ultimately determining whether or not ice sheets could grow in Scandinavia.
The model showed that as long as the ocean gateways in the Canadian Arctic Archipelago remain open, Earth’s orbital configuration cooled the Northern Hemisphere enough to allow ice sheets to build up in Northern Canada and Siberia, but not in Scandinavia.
In the second experiment, the researchers simulated a scenario where marine ice sheets obstructed the waterways in the Canadian Arctic Archipelago. In this experiment, the comparatively fresh Arctic and North Pacific water which is usually routed through the Canadian Arctic Archipelago was diverted east of Greenland, where deep water masses typically form. This diversion led to a weakening and freshening of the North Atlantic deep circulation, sea ice expansion and cooler conditions in Scandinavia.
https://phys.org/news/2022-06-long-standing-mystery-triggered-ice-age.html