A concerted 12-year study of a remote interior region of the Arctic Ocean—considered the flywheel of Arctic climate—has revealed significant environmental changes that could in turn cause further changes in ocean circulation and climate.
A multinational team of scientists investigated the Beaufort Gyre—a pool of cold, icy, relatively fresh waters north of Alaska corralled by prevailing winds into a circular swirl ten times the size of Lake Michigan. If the gyre weakens, vast volumes of trapped freshwater leak out, and climate conditions can shift.
Over the past 12 years, the scientists found that the extent and thickness of sea ice in the gyre has diminished, while the volume of freshwater has increased by 25 percent since the 1970s.
Scientists from the United States, Canada, and Japan began their large-scale collective effort in 2003 and have returned to the region every summer since. With funding from the National Science Foundation, the team included researchers from Woods Hole Oceanographic Institution, Andrey Proshutinsky and Rick Krishfield, who deployed moorings and instruments from icebreakers to gather data on sea ice and ocean conditions.
According to Proshutinsky, “One of the most striking observations in the past decade has been a reduction in both sea-ice extent and thickness, particularly in the Beaufort Gyre region.”
The big increase in freshwater is also a concern because if it is released from the gyre, it can flow out of the Arctic Ocean and form a cap of cold, less-dense freshwater atop the North Atlantic. Such a cap can alter the ocean’s circulation and the heat exchange between ocean and atmosphere, cooling the North Atlantic region. A significant freshwater release in the North Atlantic in the late 1960s and early 1970s, known as a Great Salinity Anomaly, produced such climate impacts.
The scientists found that the volume of freshwater in the gyre increased considerably from 2003 to 2008 but then stabilized at that point through 2012. In fact, in 2013, “the liquid freshwater component was at its lowest value since 2007,” remarked Krishfield. But initial findings for 2014 show a remarkable rebound of freshwater in the gyre, indicating that 2013 may have been an anomaly. Krishfield says, “The climate system may have exceeded a ‘tipping point’ where the freshwater could continue to accumulate and exceed anything observed in the past.”
Present funding will allow for the annual cruises to continue until at least 2017 to monitor the environment. More information can be found at the project’s website: www.whoi.edu/beaufortgyre.