No one is entirely sure what this
all means and how it all ties in to the persistent loss of gross sea ice
throughout the Arctic . The apparent changes may be coincidental or
not changes at all because our ability to measure these things are no older and
earlier data simply does not exist in a properly comparable form.
It does suggest that the movement
of fresh river water into the Beaufort and the Canadian Arctic as opposed in to
the North Sea for example may have a significant effect on the delivery of heat
into the Arctic from the Gulf Stream .
Unfortunately we are all
speculating and no models yet exist to test out understanding of a naturally
complex and even chaotic situation.
ScienceDaily (Jan. 4, 2012) — A hemispherewide phenomenon -- and
not just regional forces -- has caused record-breaking amounts of freshwater to
accumulate in the Arctic's Beaufort Sea .
Frigid freshwater flowing into the Arctic Ocean from three of Russia
The new findings show that a low pressure pattern created by the Arctic
Oscillation from 2005 to 2008 drew Russian river water away from the Eurasian
Basin, between Russia and Greenland, and into the Beaufort Sea, a part of the
Canada Basin bordered by the United States and Canada. It was like adding 10
feet (3 meters) 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. Too much
freshwater exiting the Arctic would inhibit the interplay of cold water from
the poles and warm water from the tropics," said Jamie Morison, an
oceanographer with the University
of Washington
Morison and his six co-authors from the UW and NASA's Jet Propulsion
Laboratory are the first to detect this freshwater pathway and its connection
to the Arctic Oscillation. The work is based on water samples gathered in the
field combined with satellite oceanography possible for the first time with
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," said
co-author Ron Kwok, senior research scientist with the Jet Propulsion
Laboratory in Pasadena , Calif.
Taken as a whole, the salinity of the Arctic Ocean is similar to the
past, but the change in the freshwater pathway means the Eurasian Basin
has gotten more saline while the Canada
Basin
"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 the Eurasian Basin , the change means less freshwater enters the layer
known as the cold halocline and could be contributing to declines in ice in
that part of the Arctic , Morison said. The
cold halocline normally sits like a barrier between ice and warm water that
comes into the Arctic from the Atlantic Ocean .
Without salt the icy cold freshwater is lighter, which is why it is able to
float over the warm water.
In the Beaufort Sea , the water is the
freshest it's been in 50 years of record keeping, he said. The new findings
show that only a tiny fraction is from melting ice and the vast majority is
Eurasian river water.
The Beaufort Sea stores a significant
amount of freshwater from a number of sources, especially when an atmospheric
condition known as the Beaufort High causes winds to spin the water in a
clockwise gyre. When the winds are weaker or spin in the opposite direction,
freshwater is released back into the rest of the Arctic
Ocean , and from there to the world's oceans. Some scientists have
said a strengthening of the Beaufort High is the primary cause of freshening,
but the paper says salinity began to decline in the early 1990s, a time when
the Beaufort High relaxed and the Arctic Oscillation increased.
"We discovered a pathway that allows freshwater to feed the
Beaufort gyre," Kwok said. "The Beaufort High is important but so are
the broader-scale effects of the Arctic Oscillation."
"A number of people have come up with ways of looking at regional
forces at work in the Arctic," Morison said, "To better understand
changes in sea ice and the Arctic overall we need to look more broadly at the
hemisphere wide Arctic Oscillation, its effects on circulation of the Arctic
Ocean and how global warming might enhance those effects."
In coming years if the Arctic Oscillation stops perpetuating that low
pressure, the freshwater pathway should switch back.
Morison and the co-authors argue that, compared to prior years, the
Arctic Oscillation has been in its current state for the last 20 years. For
example, the changes detected in response to the Arctic Oscillation between
2005 and 2008 are very similar to freshening seen in the early 1990s, Morison
said.
Discerning the track of freshwater from Eurasian rivers would have been
impossible without the ICESat and GRACE satellites, Kwok and Morison agree.
With satellite measurements of ocean height and bottom pressures, the
researchers could separate the changes in mass from changes in density -- or
freshwater content -- of the water column.
"To me it's pretty spectacular that you have these satellites
zipping around hundreds of kilometers above the Earth and they give us a number
about salinity that's very close to what we get from lowering little sampling
bottles into the ocean," Morison said.
Other co-authors are Cecilia Peralta-Ferriz with the UW's School of
Oceanography and Matt Alkire, Ignatius Rigor, Roger Andersen and Mike Steele,
all with the UW's Applied Physics Laboratory.
The work was funded by the National Science Foundation and NASA.
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