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A powerful, newly discovered current flowing near Iceland adds another piece to the ocean's “conveyor belt,” and could change models of the North Atlantic's climate future.
The existence of the North Icelandic Jet (NIJ), as the deep-water current is called, was recently confirmed by a multinational team of researchers. The team's measurements of the current were published online in the journal Nature Geoscience.
"In our paper we present the first comprehensive measurements of the NIJ," said study co-author Robert S. Pickart of Woods Hole Oceanographic Institute in a press release. "Our data demonstrate that the NIJ indeed carries overflow water into Denmark Strait and is distinct from the East Greenland Current. We show that the NIJ constitutes approximately half of the total overflow transport and nearly all of the densest component.”
The North Icelandic Jet and East Greenland current feed into the Denmark Strait Overflow Water. These deep cold water currents carry dense water south from the North Atlantic through undersea gaps in the Greenland-Scotland ridge.
This movement of cold water is balanced by warm water moving north closer to the surface. Together the warm and cold currents form the Atlantic Meridional Overturning Circulation, also called the “great ocean conveyor belt.”
This oceanic conveyor belt has been suggested to be the reason Northern Europe and the British Isles have warmer climates than Nova Scotia, Labrador, and Newfoundland, even though they are at similar latitudes.
A break down in the conveyor belt could mean a colder climate in the northern hemisphere. Ironically, it could be global warming that leads to a colder northern hemisphere.
Increasing amounts of fresh water from melting glaciers and icecaps could collect in the North Atlantic. Since fresh water is less dense that salt water, it could prevent the cold water from sinking and feeding into the conveyor belt, according to NASA scientists.
Previous models of this phenomenon did not include the North Icelandic Jet in their calculations.
"If a large fraction of the overflow water comes from the NIJ, then we need to re-think how quickly the warm-to-cold conversion of the AMOC [ocean conveyor belt] occurs, as well as how this process might be altered under a warming climate," Pickart said.
IMAGE 1: Northern part of Denmark Strait showing the location of the newly discovered deep current in relation to the known existing pathway of dense water. (Graphic by Jack Cook, Woods Hole Oceanographic Institution)
IMAGE 2: The North Icelandic Jet shown in cross-section view adjacent to the continental slope of Iceland. (Graphic by Jack Cook, Woods Hole Oceanographic Institution)