average global temperature 2010=2005=1998, where is the warming
Guthard
k...@kymhorsell.com
Greenland's Ice Feels the Heat in Record-Setting 2010
Greenland's massive ice sheet experienced record surface melting and runoff
last y, according to research released today.
By LAUREN MORELLO of ClimateWire
Published: January 21, 2011
New York Times
Unusually warm conditions in much of the country helped extend the annual
melting season by up to 50 days longer in 2010 than the average observed
between 1979 and 2009, researchers found.
Last y also set records for the amount of water runoff from the ice surface,
loss of surface ice and the number of days when ice was bare rather than
blanketed by snow. Summer snowfall was below average.
"In 2010, generally speaking, surface temperatures were higher than average,"
said lead author Marco Tedesco of the City College of New York's Cryosphere
Processes Laboratory. "It was not just the summer temperatures, but also the
spring and later winter temperatures. The melting season started early and
lasted much longer than normal."
Tedesco's co-authors include researchers from the University of Liege in
Belgium, Utrecht University in the Netherlands, the National Snow and Ice Data
Center in Boulder, Colo., and Ohio State University. Their work was published
today in the journal Environmental Research Letters.
The researchers based their analysis on satellite observations of surface
temperatures, satellite estimates of surface melting, ground observations from
automated weather stations on the ice sheet's surface and computer models.
"The overall idea of the project is to improve the capability of the models by
ingesting this information from satellites and ground observations," Tedesco
said. That will help scientists project how future warming will affect the
behavior of Greenland's ice, which could help improve estimates of sea level
rise.
Recent studies suggest that sea level will rise between 3 and 6 feet by 2100,
with a significant contribution coming from the more rapid melting of huge ice
sheets in Antarctica and Greenland.
Mechanisms that accelerated the melting
Last y was the warmest in Greenland's capital, Nuuk, since record keeping
began there in 1873. Nuuk, on the country's southwest coast, also set records
in 2010 for warmest winter, spring and summer seasons.
Meanwhile, the southern Greenland community of Narsarssuaq recorded its
warmest-ever winter and spring, warmest May, and warmest y since observations
began in 1951. The town of Aasiat in western Greenland saw its warmest y,
winter, spring, and months of May and June since record keeping started in
1951.
But that unusual warmth is just the beginning of the story of what happened
last y, Tedesco said.
Greenland's annual melt began earlier than normal last spring. As that melt
reduced the amount of snow on the ice surface, it also "aged" the snow that
remained so it became less reflective and absorbed more heat from the sun --
accelerating the melting further.
Eventually, the combination of unusual warmth and below-average summer
snowfall exposed large portions of bare ice, which is less reflective than
snow and absorbs even more heat. That helped extend the length of the melt
season well into the fall.
"Everything adds up to accelerate things," Tedesco said. "They are all guilty."
While 2010 was a record-setting y in Greenland, the scientist said his study
is important because it used a variety of data, estimates and models to
construct a detailed picture of how processes affecting the ice sheet
influence each other.
A process that could become 'exponential'
"The bottom line of the paper is that we know that it is important to look at
the surface temperature," Tedesco said. "We know the warmer it is, the more
melting you have. But this is not just a linear relationship. It can be
exponential, and increase much faster. ... It's important to look at all of
these processes as a whole."
That can help improve scientists' understanding of how the Greenland ice sheet
will respond to future climate change, and how that will affect sea level
rise, he said.
The new study didn't examine one of the major processes by which Greenland
loses ice and contributes to sea level rise -- the calving of icebergs. But it
did examine melting at the surface of the ice sheet, which scientists believe
influences the speed at which the ice sheet slides to the sea.
Earlier research has shown that some of the meltwater drains into cracks in
the ice down to the bedrock below, where it helps lubricate the ice sheet's
movements.
--
Ah yes, a very strong brand of anecdotal evidence. Climate science will
be proud. The science remains settled, the consensus unshaken.
-- Mickey Langan, Sun 2 Jan 2011 10:00 am