Something new for ice age theorists to consider, in particular the ‘sudden melting’. This sequence of three sketches illustrates the processes thought to be involved (see below for explanatory caption).
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The Arctic Ocean was covered by up to 900-meter-thick shelf ice and was filled entirely with freshwater at least twice in the last 150,000 years.
This surprising finding, reported in the latest issue of the journal Nature, is the result of long-term research by scientists from the Alfred Wegener Institute and the MARUM, says Phys.org.
With a detailed analysis of the composition of marine deposits, the scientists could demonstrate that the Arctic Ocean as well as the Nordic Seas did not contain sea-salt in at least two glacial periods.
Instead, these oceans were filled with large amounts of freshwater under a thick ice shield. This water could then be released into the North Atlantic in very short periods of time.
Such sudden freshwater inputs could explain rapid climate oscillations for which no satisfying explanation had been previously found.
In glacial periods with low sea levels, exchange with the Pacific was halted and exchange with the North Atlantic was extremely reduced, while the Arctic basin was still receiving freshwater input. Exchange could only occur through narrow gateways in the Greenland-Scotland-Ridge. The sequence of three sketches shows (1) a period of freshening of the Arctic Ocean followed by (2) the release of freshwater to the North Atlantic, when saline water entered the Arctic Ocean and (3) sudden melting of the Arctic ice sheet upon contact with the relatively warm and salty Atlantic water. Credit: Alfred Wegener Institute/Martin Künsting
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February 4, 2021 at 05:12AM