New research by an international team of scientists describes the causes for the stalled trend in Arctic Ocean sea-ice loss since 2007. The findings indicate that stronger declines in sea ice will occur when an atmospheric feature known as the Arctic dipole reverses itself in its recurring cycle.
Environmental responses to the Arctic dipole are described in a paper published in the journal Science. The analysis helps explain how North Atlantic water influences the Arctic Ocean climate. Scientists refer to this phenomenon as Atlantification.
The U.S. National Science Foundation-supported research is led by Igor Polyakov of the University of Alaska Fairbanks. "This is a multidisciplinary view on what's going on in the Arctic and beyond," Polyakov said. "Our analysis covered the atmosphere, ocean, ice, changing continents and changing biology in response to climate change."
A wealth of data, including direct instrumental observations, reanalysis products and satellite information going back several decades, show that the Arctic dipole alternates in an approximately 15-year cycle and that the system is probably at the end of the present period.
"Evidence of Atlantification in the Arctic demonstrates that local to regional changes in atmospheric processes and ocean properties have implications for understanding and forecasting Earth climate systems arising from a changing Arctic," said Roberto Delgado, a program director in NSF's Office of Polar Programs.
In the Arctic dipole's present "positive" state, which scientists say has been in place since 2007, high pressure is centered over the Canadian sector of the Arctic and produces clockwise winds. Low pressure is centered over the Siberian Arctic and features counterclockwise winds.
This wind pattern drives upper ocean currents, with year-round effects on regional air temperatures, atmosphere-ice-ocean heat exchanges, sea-ice drift and exports, and ecological consequences.
The authors write that "water exchanges between the Nordic seas and the Arctic Ocean are critically important for the state of the Arctic climate system" and that sea-ice decline is "a true indicator of climate change."
In analyzing oceanic responses to the wind pattern since 2007, the researchers found decreased flow from the Atlantic Ocean into the Arctic Ocean through the Fram Strait, east of Greenland, along with increased Atlantic flow into the Barents Sea, located north of Norway and western Russia.
The new research refers to these alternating changes in the Fram Strait and the Barents Sea as a "switchgear mechanism" caused by the Arctic dipole cycles.
The scientists state that the switchgear mechanism regulating inflows of sub-Arctic waters has profound impacts on marine life. It could lead to more suitable living conditions for sub-Arctic boreal species near the eastern part of the Eurasian Basin, relative to its western part.
"We are beyond the peak of the currently positive Arctic dipole regime, and at any moment it could switch back again," Polyakov said. "This could have significant climatological repercussions, including a potentially faster pace of sea-ice loss across the entire Arctic and sub-Arctic climate systems."
