Sea ice acts as ‘pacemaker’ for abrupt climate change

Substantial variations in past sea ice cover in the Norwegian Sea were instrumental for several abrupt climate changes in large parts of the world, researchers have found.

Icebergs in Ilulissat Icefjord, Greenland Credit: United Nations Photo
Icebergs in Ilulissat Icefjord, Greenland Credit: United Nations Photo

The last glacial period was marked by pronounced millennial-scale variability in ocean circulation and global climate. Shifts in sea ice cover within the Nordic Seas are believed to have amplified the glacial climate variability in northern high latitudes and contributed to abrupt, high-amplitude temperature changes over Greenland.

In a new international study, scientists have confirmed that changes in sea ice cover in the Norwegian Sea assumed a key job in driving unexpected climate change events between 32,000 and 40,000 years ago, where global temperatures moved as much as 15 degrees Celsius.

Their outcome indicates that primary sea ice reduction began before the unexpected warming over Greenland, and that sea ice expansion began before the finish of the warm periods in Greenland.

The Arctic sea ice is a key component of the global climate system and the strong continuous warming of the Arctic Ocean can have major effects on the stability of the Greenland Ice Sheet, most importantly accelerated sea level rise.

The Nordic Sea system and its water column structure amid the last glacial cycle is the nearest simple to the present-day Arctic Ocean, which makes it an ideal characteristic research center to comprehend the job of the rapid disappearance of regional sea ice on unexpected warming on the Greenland Ice Sheet.

The last chilly time frame, 10,000– 100,000 years ago, was set apart by repeated abrupt climate changes with global implications. Inside only decades, temperature shifts of as much as 15 degrees Celsius occurred around Greenland, however, the components driving these changes – known as Dansgaard-Oeschger occasions – are not completely comprehended.

Co-author Dr. Francesco Muschitiello, from the University of Cambridge’s Department of Geography, said, “One of the most challenging aspects of paleoclimatology is to precisely resolve and reconstruct the exact timing of the events that took place across the major climate transitions of the last glacial cycle. As a result, a detailed account of the temporal relationship between changes in sea-ice extent in the Nordic Seas, and North Atlantic ocean circulation and climate across Dansgaard-Oeschger events have been so far elusive.”

During the study, scientists investigated explicit natural atoms in a residue center from the southern Norwegian Sea, one of which was created by algae that live in sea ice and others that were produced by organisms living in open, without ice waters a huge number of years prior. The new sea ice reconstruction based on organic molecules in marine sediments was also evaluated by means of results from a model simulation of past sea ice conditions.

The data suggests that there were substantial changes in the sea ice cover in the southern Norwegian Sea between 32,000 and 40,000 years ago. Most extensive sea ice conditions happened at the onsets and early pieces of cold periods over Greenland and the most pronounced open-ocean conditions happened at the onsets of the sudden changes to warm periods over Greenland.

In turn, sea ice reduction allowed for heat release from the exposed Norwegian Sea waters to the atmosphere, which was a prime ingredient in shaping the abrupt warming of the Dansgaard-Oeschger climate events in Greenland.

The Dansgaard–Oeschger climate events have stirred interest in documenting that the climate system contains mechanisms that may lead to abrupt and surprising climate changes.

These findings clarify the series of events taking place in the high-latitude North Atlantic across the abrupt Dansgaard–Oeschger cycles of the last glacial period. However, further work is needed to ultimately identify the physical mechanisms linking the current sudden demise of Arctic sea ice to abrupt Greenland Ice Sheet changes.

The team included scientists from the UK, Norway, Germany Australia, South Korea, and the US. The study is published in the journal Science Advances.