New current that transports water to one of world’s largest ‘waterfalls’ discovered in deep ocean

July 29, 2020
Large ferry boat, the MS Norröna, powering to its next destination.
The high-seas ferry MS Norröna, cited in the Nature Communications paper, measures upper ocean currents with an ADCP (acoustic Doppler current profiler) installed in its hull as it makes a weekly roundtrip between Denmark, the Faroe Islands and Iceland. (Photo: Erik Christensen - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=45707529)

URI professor emeritus part of research team

July 29, 2020

An international team discovered a previously unrecognized ocean current that transports water to one of the world’s largest “waterfalls” in the North Atlantic Ocean: the Faroe Bank Channel Overflow into the deep North Atlantic. While investigating the pathways that water takes to feed this major waterfall, the research team identified a surprising path of the cold and dense water flowing at depth, which led to the discovery of this new ocean current.

“This new ocean current and the path it takes toward the Faroe Bank Channel are exciting findings,” said Léon Chafik, the lead author of the paper published in Nature Communications and a research scientist at Stockholm University, Sweden.

“The two discoveries reported here, in one of the best studied areas of the world ocean, is a stark reminder that we still have much to learn about the Nordic Seas,” said co-author Thomas Rossby, emeritus professor at the URI Graduate School of Oceanography. “This is crucial given the absolutely fundamental role they play in the major glacial-interglacial climate swings.”

Previous studies dealing with this deep flow have long assumed that these cold waters, which flow along the northern slope of the Faroes, turn directly into the Faroe-Shetland Channel (the region the water flows through before reaching the Faroe Bank Channel). Instead, Chafik and the paper’s co-authors show that there exists another path into the Faroe-Shetland Channel. They show that water can take a longer path all the way to the continental margin outside Norway before turning south heading toward this major waterfall. “Revealing this newly identified path from available observations was not a straightforward process and took us a good deal of time to piece together” said Chafik.

The researchers also found this new path depends on prevailing wind conditions. “It seems that the atmospheric circulation plays a major role in orchestrating the identified flow regimes,” added Chafik.

The study further reveals that much of the water that will end up in the Faroe Bank Channel is not in fact transported along the western side of the Faroe-Shetland Channel (the region the water flows through before reaching the Faroe Bank Channel), as previously thought. Instead, most of this water comes from the eastern side of the Faroe-Shetland Channel where it is transported by a jet-like and deep-reaching ocean current. “This was a curious but very exciting finding, especially since we are aware that a very similar flow structure exists in the Denmark Strait. We are pleased that we were able to identify this new ocean current both in observations and a high-resolution ocean general circulation model,” said Chafik.

“Because this newly discovered flow path and ocean current play an important part in the ocean circulation at higher latitudes, its discovery adds to our limited understanding of the overturning circulation in the Atlantic Ocean,” said Chafik. “This discovery would not have been possible without many institutional efforts over the years.”