[asa] Re: Arctic and Antarctic Ice in Trouble

From: John Burgeson (ASA member) <hossradbourne@gmail.com>
Date: Mon Apr 06 2009 - 15:15:26 EDT

RealClimate.org has a new thread developing on this subject.
Useful stuff.
The dittoheads have not (yet) found it.


On 4/6/09, Rich Blinne <rich.blinne@gmail.com> wrote:
> http://www.eurekalert.org/pub_releases/2009-04/uoca-nas040609.php
> New Arctic satellite data shows Arctic literally on thin ice
> The latest data from NASA and the University of Colorado at Boulder's
> National Snow and Ice Data Center show the continuation of a decade-long
> trend of shrinking sea ice extent in the Arctic, including new evidence for
> thinning ice as well.
> The researchers, who have been tracking Arctic sea ice cover with
> satellites
> since 1979, found that the winter of 2008-09 was the fifth lowest maximum
> ice extent on record. The six lowest maximum events in the satellite record
> have all occurred in the past six years, according to CU-Boulder researcher
> Walt Meier of NSIDC.
> The new measurements by CU-Boulder's NSIDC show the maximum sea ice extent
> for 2008-09 reached on Feb. 28 was 5.85 million square miles, which is
> 278,000 square miles below the average extent for 1979 to 2000, an area
> slightly larger than the state of Texas, said Meier.
> In addition, a team of CU-Boulder researchers led by Research Associate
> Charles Fowler of the Colorado Center for Astrodynamics Research, or CCAR,
> has found that younger, thinner ice has replaced older, thicker ice as the
> dominant type over the past five years, making it more prone to summer
> melt.
> "Ice extent is an important measure of the health of the Arctic, but it
> only
> gives us a two dimensional view of the ice cover," said Meier. "Thickness
> is
> important, especially in the winter, because it is the best overall
> indicator of the health of the ice cover. As the ice cover in the Arctic
> grows thinner, it becomes more vulnerable to summer melt."
> Until recent years, measurements have shown most Arctic ice has survived at
> least one summer and often several, said Meier. But the balance has now
> flipped, and seasonal ice -- which melts and re-freezes every year -- now
> comprises about 70 percent of Arctic sea ice in winter, up from 40 to 50
> percent in the 1980s and 1990s, he said. Thicker ice that has survived two
> or more years now comprises just 10 percent of ice cover, down from 30 to
> 40
> percent in years past.
> Scientists believe Arctic sea ice functions like an air conditioner for the
> global climate system by naturally cooling air and water masses, playing a
> key role in ocean circulation and reflecting solar radiation back into
> space.
> In a related study led by Ron Kwok of NASA's Jet Propulsion Laboratory in
> Pasadena, Calif., researchers have demonstrated a way to estimate ice
> thickness over the entire Arctic Ocean. Using two years of data from NASA's
> Ice, Cloud and Land Elevation Satellite, or ICESat, the team made the first
> basin-wide estimate of the thickness and volume of the Arctic Ocean ice
> cover for 2005 and 2006.
> "With the new data on the area and thickness of Arctic sea ice, we can now
> better understand the sensitivity and vulnerability of the ice cover to
> changes in climate," Kwok said.
> A recent study by a team from CU-Boulder's CCAR concluded there has been a
> near complete loss of the oldest, thickest Arctic ice, and that 58 percent
> of perennial ice was only two to three years old. In the mid-1980s, only 35
> percent of that sea ice was that young and that thin, according to
> aerospace
> engineering sciences department Research Professor James Maslanik, who led
> the 2008 study published in *Geophysical Research Letters*.
> "Heading into the 2009 summer melt season, the potential continues for
> extensive ice retreat due to the trend toward younger, thinner ice that has
> accelerated in recent years," said Maslanik, also a member of the
> Cooperative Institute for Research in Environmental Sciences. "A key
> question will be whether this second year ice is thick enough to survive
> summer melt," said Maslanik.
> "If it does, this might start a trend toward recovery of the perennial sea
> ice pack," Maslanik said. "If it doesn't, then this would be further
> evidence of the difficulty of re-establishing the ice conditions that were
> typical of 20 or 30 years ago."
> The Arctic ice cap grows each winter as the sun sets for several months and
> intense cold sets in. The total volume of winter Arctic ice is equal to the
> volume of fresh water in Lake Superior and Lake Michigan combined.
> While some sea ice is naturally pushed out of the Arctic by winds, much of
> it melts in place. First-year sea ice usually reaches 6 feet in thickness,
> while ice that has lasted through more than one summer averages 9 feet and
> can grow much thicker in some locations near the coast.
> ###
> And on the Antarctica front.
> Note this ESA animation of the Wilkins Ice Shelf.
> http://www.esa.int/esaEO/SEMWZS5DHNF_index_0.html
> If the ice bridge were to open, it could put the entire ice shelf at risk
> of
>> further disintegrating.
> Well that appears to be happening this week.
> http://www.google.com/hostednews/ap/article/ALeqM5h1YwRKCHpwN65ds0uwNjB7W0JQ-QD97B7K100
> A massive ice shelf anchored to the Antarctic coast by a narrow and quickly
>> deteriorating ice bridge could break away soon, the European Space Agency
>> warned Friday.
>> The Paris-based agency said satellite images show the bridge that
>> connects
>> the Wilkins Ice Shelf to Charcot and Latady Islands "looks set to
>> collapse."
>> "The beginning of what appears to be the demise of the ice bridge began
>> this week when new rifts" appeared and a large block of ice broke away,
>> it
>> said.
> This is the tenth major ice shelf to collapse in recent times. If you are
> going to worry about something ice shelves are a bigger deal than sea ice.
> Think of sea ice as ice cubes in your drink. If they melt they don't make
> your drink take up any more volume. The relevance of sea ice is as a canary
> in the mine. Ice shelves do increase your sea surface level and are
> susceptible to unpredictable effects such as the ice bridge collapse on the
> Wilkins. Because of this IPCC AR4 punted on predicting this effect and gave
> the false impression that sea level rise is less than it will be.
> Rich Blinne
> Member ASA

To unsubscribe, send a message to majordomo@calvin.edu with
"unsubscribe asa" (no quotes) as the body of the message.
Received on Mon Apr 6 15:16:31 2009

This archive was generated by hypermail 2.1.8 : Mon Apr 06 2009 - 15:16:31 EDT