January 5, 2012
Russian River Runoff Freshening Beaufort Sea
According to findings published in the journal Nature, Russian river water was diverted hundreds of miles to a different part of the ocean in response to a decades-long shift in atmospheric pressure.
Researchers found that a low pressure pattern created by the Arctic Oscillation from 2005 to 2008 drew Russian river water away from the Eurasian Basin and into the Beaufort Sea.This diversion resulted in adding 10 feet of freshwater over the central part of the Beaufort Sea.
"Knowing the pathways of freshwater in the upper ocean is important to understanding global climate because of freshwater's role in protecting sea ice — it can help create a barrier between the ice and warmer ocean water below — and its role in global ocean circulation," Jamie Morison, an oceanographer with the University of Washington's Applied Physics Laboratory, said in a press release.
"Too much freshwater exiting the Arctic would inhibit the interplay of cold water from the poles and warm water from the tropics."
The team based their findings on water samples gathered in the field combined with satellite oceanography data from NASA satellites known as ICESat and GRACE.
"Changes in the volume and extent of Arctic sea ice in recent years have focused attention on the impacts of melting ice," co-author Ron Kwok, senior research scientist with the Jet Propulsion Laboratory in Pasadena, California, said in a press release. "The combined GRACE and ICESat data allow us to now examine the impacts of widespread changes in ocean circulation."
The salinity of the Arctic Ocean is similar to the past, but changes in the freshwater pathway means the Eurasian Basin has gotten more saline while the Canada Basin has gotten fresher.
"The freshening on the Canadian side of the Arctic over the last few years represents a redistribution of freshwater, there does not seem to be a net freshening of the ocean," Kwok said in a press release.
Morison said the change in the Eurasian Basin could mean less freshwater enters the layer known as the cold halocline and could be contributing to declines in ice in that part of the Arctic.
He said the water is the freshest it has been in 50 years of record keeping in the Beaufort Sea.
This sea stores more freshwater when an atmospheric pressure system called the Beaufort high strengthens, driving a counterclockwise wind pattern.
Some say the primary cause of freshening is a strengthening of the Beaufort High, but salinity began to decline early in the 1990s, when the Beaufort High relaxed and the counterclockwise Arctic Oscillation pattern increased.
"We discovered a pathway that allows Russian river runoff to feed the Beaufort gyre," Kwok said in a press release. "The Beaufort High is important, but so are the hemispheric-scale effects of the Arctic Oscillation."
"To better understand climate-related changes in sea ice and the Arctic overall, climate models need to more accurately represent the Arctic Oscillation's low pressure and counterclockwise circulation on the Russian side of the Arctic Ocean," Morison added.
Image 1: An instrument about to be dropped through an opening in the ice to the seafloor will record ocean bottom pressure to compare with similar data recorded by NASA's GRACE satellites. Data from GRACE, ICESat and actual water samples led to the discovery of a new pathway of freshwater in the Arctic. Credit: C. Peralta-Ferriz/UW Applied Physics Laboratory
Image 2: Increasing freshwater on the U.S. and Canadian side of the Arctic from 2005 to 2008 is balanced by decreasing freshwater on the Russian side, so that on average the Arctic did not have more freshwater. Here blue represents maximum freshwater increases and the yellows and oranges represent maximum freshwater decreases. Credit: University of Washington
Image 3: Red arrows show the new path of Russian river water into the Canada Basin. The previous freshwater pathway - across the Eurasian Basin toward Greenland and the Atlantic - was altered by atmospheric conditions created by the Arctic Oscillation. Credit: University of Washington
On the Net:
- University of Washington Applied Physics Laboratory
- NASA Jet Propulsion Laboratory
- For more on Grace and ICESat, visit: http://www.csr.utexas.edu/grace/ , http://grace.jpl.nasa.gov/ , and http://icesat.gsfc.nasa.gov/icesat/ .