And a few days ago the entire Beaufort sea ice cover literally
shattered. Thus the spring is truly off to an interesting start and
plenty more to come. Everyone has forgotten that we seriously broke
records last season and there is ample reason to think we are
entering uncharted country here. Now the winter recovery is lack
luster as well.
Add in the right wind conditions and we could see the ice been
rapidly removed.
In other words we can expect to see an interesting melt season this
year.
2013 Wintertime
Arctic Sea Ice Maximum Fifth Lowest on Record
by Maria-Jose Vinas for Goddard Space Flight Center,
Greenbelt MD (SPX) Apr 05, 2013
Last September, at the
end of the northern hemisphere summer, the Arctic Ocean's icy cover
shrank to its lowest extent on record, continuing a long-term trend
and diminishing to about half the size of the average summertime
extent from 1979 to 2000.
During the cold and
dark of Arctic winter, sea ice refreezes and achieves its maximum
extent, usually in late February or early March. According to a NASA
analysis, this year the annual maximum extent was reached on Feb. 28
and it was the fifth lowest sea ice winter extent in the past 35
years.
The new maximum -5.82
million square miles (15.09 million square kilometers)- is in line
with a continuing trend in declining winter Arctic sea ice extent:
nine of the ten smallest recorded maximums have occurred during the
last decade. The 2013 winter extent is 144,402 square miles (374,000
square kilometers) below the average annual maximum extent for the
last three decades.
"The Arctic
region is in darkness during winter and the predominant type of
radiation is long-wave or infrared, which is associated with
greenhouse warming," said Joey Comiso, senior scientist at NASA
Goddard Space Flight Center, Greenbelt, Md., and a principal
investigator of NASA's Cryospheric Sciences Program. "A decline
in the sea ice cover in winter is thus a manifestation of the effect
of the increasing greenhouse gases on sea ice."
Satellite data
retrieved since the late 1970s show that sea ice extent, which
includes all areas of the Arctic Ocean where ice covers at least 15
percent of the ocean surface, is diminishing. This decline is
occurring at a much faster pace in the summer than in the winter; in
fact, some models predict that the Arctic Ocean could be ice-free in
the summer in just a few decades.
The behavior of the
winter sea ice maximum is not necessarily predictive of the following
melt season. The record shows there are times when an unusually large
maximum is followed by an unusually low minimum, and vice versa.
"You would think
the two should be related, because if you have extensive maximum,
that means you had an unusually cold winter and that the ice would
have grown thicker than normal. And you would expect thicker ice to
be more difficult to melt in the summer," Comiso said. "But
it isn't as simple as that. You can have a lot of other forces that
affect the ice cover in the summer, like the strong storm we got in
August last year, which split a huge segment of ice that then got
transported south to warmer waters, where it melted."
The NASA Goddard sea
ice record is one of several analyses, along with those produced by
the National Snow and Ice Data Center (NSIDC) in Boulder, Colo. The
two institutions use slightly different methods in their sea ice
tally, but overall, their trends show close agreement. NSIDC
announced that Arctic sea ice reached its winter maximum on Mar. 15,
at an extent of 5.84 million square miles (15.13 million square
kilometers) - a difference of less than half a percent compared to
the NASA maximum extent.
Another measurement
that allows researchers to analyze the evolution of the sea ice
maximum is sea ice "area." The measurement of area, as
opposed to extent, discards regions of open water among ice floes and
only tallies the parts of the Arctic Ocean that are completely
covered by ice. The winter maximum area for 2013 was 5.53 million
square miles (14.3 million square kilometers), also the fifth lowest
since 1979.
While the extent of
winter sea ice has trended downward at a less drastic rate than
summer sea ice, the fraction of the sea ice cover that has survived
at least two melt seasons remains much smaller than at the beginning
of the satellite era. This older, thicker "multi-year ice"
- which buttresses the ice cap against more severe melting in the
summer - grew slightly this past winter and now covers 1.03 million
square miles (2.67 million square kilometers), or about 39,000 square
miles more than last winter. But its extent is still less than half
of what it was in the early 1980s.
"I think the
multi-year ice cover will continue to decline in the upcoming years,"
Comiso said. "There's a little bit of oscillation, so there
still might be a small gain in some years, but it continues to go
down and before you know it we'll lose the multi-year ice
altogether."
This winter, the
negative phase of the Arctic Oscillation kept temperatures warmer
than average in the northernmost latitudes. A series of storms in
February and early March opened large cracks in the ice covering the
Beaufort Sea along the northern coasts of Alaska and Canada, in an
area of thin seasonal ice. The large cracks quickly froze over, but
these new layers of thin ice might melt again now that the sun has
re-appeared in the Arctic, which could split the ice pack into
smaller ice floes.
"If you put a
large chunk of ice in a glass of water, it is going to melt slowly,
but if you break up the ice into small pieces, it will melt faster,"
said Nathan Kurtz, a sea ice scientist at NASA Goddard. "If the
ice pack breaks up like that and the melt season begins with
smaller-sized floes, that could impact melt."
In the upcoming weeks,
Kurtz will analyze data collected over the Beaufort Sea by NASA's
Operation IceBridge, an airborne mission that is currently surveying
Arctic sea ice and the Greenland ice sheet, to see if the sea ice in
the cracked area was abnormally thin.
The sea ice maximum
extent analysis produced at NASA Goddard is compiled from passive
microwave data from NASA's Nimbus-7 satellite and the U.S. Department
of Defense's Defense Meteorological Satellite Program. The record,
which began in November 1978, shows an overall downward trend of 2.1
percent per decade in the size of the maximum winter extent, a
decline that accelerated after 2004.
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