Speedy ice withdrawal over the past de-icing corresponds to present melting charges – Watts Up With That?
UIT THE ARCTIC UNIVERSITY OF NORWAY
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IMAGE: MAP OF STORFJORDEN AND STORFJORDEN WITH ICE SHEETS INDICATED WITH 22,000 YEARS AND ICE TREAMS. AREAS IN WHICH THE ICE SHELVES AND THE ICE TRAAMS ARE BROKEN DURING THE ATMOSPHERIC AND OCEAN … show more CREDIT: ILLUSTRATION T. RASMUSSEN / E. THOMSEN
A new study shows that 10,000 km2 of ice disappeared in no time from an ice sheet in the Storfjord through offshore Svalbard. This dramatic collapse was preceded by a rather rapid melt of 2.5 kilometers of ice per year. This is in line with current melt rates in Antarctica and Greenland and worries the scientists behind the study.
“Our measurements of the ice retreat at Storfjorden Through show that the prevailing conditions for the great eruption coincide with those we see today in Antarctica and Greenland. It’s scary. New studies are published almost every week that show that the current ice sheets are retreating two to four kilometers per year and are accelerating. “Says CAGE professor and lead author Tine Lander Rasmussen.
Climatically unstable time
The last de-icing between 20,000 and 10,000 years ago was a time of coexisting global warming and rapidly shrinking ice sheets. However, specifying the actual correlation between the two is not as easy as it sounds. The time in question was climatically unstable and large melts were interrupted by renewed freezing and the formation of new ice. The rate of ice retreat in relation to climate change was therefore difficult to determine.
“We examined the development of the ice sheet 20,000-10,000 years ago using marine sediment cores. The 12 nuclei have been collected in the region over the past 18 years and carefully examined for different types of microfossils of unicellular organisms called foraminifera, ”says Rasmussen.
The biochemistry in the foraminifera fossils helps to reconstruct the vast amount of information about the state of the environment in prehistoric times. The sediments were cut into slices representing periods of 30 to 70 years. Over 70 samples were dated and analyzed.
“We saw that the ice cover retreats about 20,000 years ago, but lingers on a ridge in the fjord. Then, about 15,000 years ago, the atmosphere and ocean temperatures warm up and affect ocean circulation. At the same time, a huge part of the ice cover disappears. Things are really picking up speed at the start of the Holocene Warm Period 11,000 years ago. After this time we can no longer see any evidence of an ice sheet covering the ocean floor. “
Consistent correlation between global warming and ice retreat
The periods of extremely rapid ice sheet retreats correlate consistently with periods of global ocean warming and temperature. This is reflected in the retreat of the ice sheet from the other eight northern Norwegian fjord systems.
“This confirms our hypothesis that an increase in sea temperature and global warming is the direct cause of the chain of events that lead to the dramatically rapid collapse of the ice sheet.” Says Rasmussen.
This gives some alarming prospects on today’s prospect. The great melt of the glacier maximum during the Holocene was 10,000 years in the making. The current climate change is much faster.
“The final retreat of the Storfjorden Through ice sheet was just as quick in the outer parts as it was above. This means that once warmer oceanic water gained access to the ice sheet, it shot inward from the edge of the ice shelf fairly quickly. To the inside of the leaf itself. We see this today in Antarctica. The terminations of Larsen A (1995), B (2003) and C (2017) are examples of this process. “
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From EurekAlert!
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