Icelandic current could change North Atlantic climate picture, says study

The presence of a deep-reaching ocean circulation system off Iceland that could significantly influence the ocean”s response to climate change in previously unforeseen ways has been confirmed by an international team of researchers, including physical oceanographers from the Woods Hole Oceanographic Institution (WHOI).

The current, called the North Icelandic Jet (NIJ), has contributed to a key component of the Atlantic Meridional Overturning Circulation (AMOC), also known as the “great ocean conveyor belt”, which is critically important for regulating Earth’s climate.

As part of the planet’s reciprocal relationship between ocean circulation and climate, this conveyor belt transports warm surface water to high latitudes where the water warms the air, then cools, sinks, and returns towards the equator as a deep flow.

Crucial to this warm-to-cold oceanographic choreography is the Denmark Strait Overflow Water (DSOW), the largest of the deep, overflow plumes that feed the lower limb of the conveyor belt and return the dense water south through gaps in the Greenland-Scotland Ridge.

For years it has been thought that the primary source of the Denmark Overflow is a current adjacent to Greenland known as the East Greenland Current.

However, this view was recently called into question by two oceanographers from Iceland who discovered a deep current flowing southward along the continental slope of Iceland.

They named the current the North Icelandic Jet and hypothesized that it formed a significant part of the overflow water.

Now, the team of researchers—including the two Icelanders who discovered it—has confirmed that the Icelandic Jet is not only a major contributor to the DSOW but “is the primary source of the densest overflow water”.

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“In our paper we present the first comprehensive measurements of the NIJ,” said Robert S. Pickart of WHOI, one of the authors of the study.

“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,” added Pickart.

The study has been detailed in the online issue of the journal Nature Geoscience.

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