Icelandic oceanic current discovered

An international research team recently found a deep-ocean current off the coast of Iceland. The discovery of the current, also known as the North Icelandic Jet (NIJ), may change model predictions for oceanic responses to climate change.  

The North Icelandic Jet is part of the Atlantic Meridional Overturning Circulation (AMOC), an ocean conveyor belt responsible for regulating Earth's climate. The aquatic component of the system works by balancing warm surface waters with cold deep-ocean currents.

When seawater is warmed, it expands and becomes less dense. The conveyor belt transports warm surface waters to higher latitudes, where they cool and sink after releasing heat to the air. The waters are then returned to the equator as deep-ocean currents.

The conveyor belt is thought to account for why Northern Europe and the British Isles have warmer climates than Nova Scotia, Labrador, and Newfoundland, even though they are situated at similar latitudes.

The Denmark Strait Overflow Water (DSOW), large deep-water currents that return dense water south through gaps in the Greenland-Scotland Ridge, is critical for the maintenance of the conveyor system. The research team, whose findings were published in Nature Geoscience, identified the Icelandic Jet as the primary source of the overflow.

Robert S. Pickart, a researcher from Woods Hole Oceanographic Institute and co-author of the study, says that the NIJ is responsible for half of the total overflow transport and carries almost all of the densest component. The NIJ and East Greenland Current, previously thought to be the primary source, feed into the overflow waters.

The researchers hypothesized, using a numerical model, how and where the NIJ is formed. They also hypothesized a new, overturning loop of warm to cold water. Pickart says that these results will have important ramifications for the impact of ocean circulation on climate.

Climatologists believe that rising global temperatures are causing the conveyor belt to slow down. They suggest that increasing amounts of fresh water from melting glaciers could freeze in the northern North Atlantic. As fresh water is less dense than salt water, this could prevent the water from sinking and feeding into the conveyor belt, thus causing the loop to deliver smaller amounts of warm water. This could eventually result in colder climates in the northern hemisphere.

Understanding the overturning process is crucial if scientists are to make accurate predictions about future climate and circulation interactions.

If a large proportion of the overflow water comes from the NIJ, says Pickart, then there is a need to rethink how quickly the warm-to-cold water conversion occurs, as well as how a warming climate may alter this process.

According to Eric Itsweire, program director of the U.S. National Science Foundation's Division of Ocean Sciences, which funded the research, these results suggest that a local water mass transformation and exchange near Iceland is a central contributor to the overturning circulation.

Pickart and a multinational team of scientists from the U.S., Iceland, Norway, and the Netherlands plan have embarked on a cruise to collect more information about overturning in the Iceland Sea. The team aims to quantify the NIJ, distinguish it from the East Greenland Current, and use shipboard measurements to determine where and how the NIJ originates.