NASA data show Arctic saw fastest August sea ice retreat on record

Sep 28, 2008
The graph shows the daily retreat of sea ice during 2008 compared to the long-term average and the 2007 record low. Credit: Robert Simmon/Jesse Allen/Michon Scott/NSIDC

Following a record-breaking season of arctic sea ice decline in 2007, NASA scientists have kept a close watch on the 2008 melt season. Although the melt season did not break the record for ice loss, NASA data are showing that for a four-week period in August 2008, sea ice melted faster during that period than ever before.

Each year at the end of summer, sea ice in the Arctic melts to reach its annual minimum. Ice that remains, or "perennial ice," has survived from year to year and contains old, thick ice. The area of arctic sea ice, including perennial and seasonal ice, has taken a hit in past years as melt has accelerated. Researchers believe that if the rate of decline continues, all arctic sea ice could be gone within the century.

"I was not expecting that ice cover at the end of summer this year would be as bad as 2007 because winter ice cover was almost normal," said Joey Comiso of NASA's Goddard Space Flight Center in Greenbelt, Md. "We saw a lot of cooling in the Arctic that we believe was associated with La NiƱa. Sea ice in Canada had recovered and even expanded in the Bering Sea and Baffin Bay. Overall, sea ice recovered to almost average levels. That was a good sign that this year might not be as bad as last year."

The 2008 sea ice minimum was second to 2007 for the record-lowest extent of sea ice, according to a joint announcement Sept. 16 by NASA and the University of Colorado's National Snow and Ice Data Center (NSIDC) in Boulder, Colo. As of Sept. 12, 2008, the ice extent was 1.74 million square miles. That's 0.86 million square miles below the average minimum extent recorded from 1979 to 2000, according to NSIDC.

Contributing to the near-record sea ice minimum in 2008 was a month-long period in the summer that saw the fastest-ever rate of seasonal retreat during that period. From August 1 to August 31, NASA data show that arctic sea ice extent declined at a rate of 32,700 square miles per day, compared to a rate of about 24,400 square miles per day in August 2007. Since measurements began, the arctic sea ice extent has declined at an average rate of 19,700 miles per day at the point when the extent reaches its annual minimum.

Observations of changes to sea ice over time are possible due to a 30-year record of data from NASA and other agency satellites, including Nimbus-7, Aqua, Terra and the Ice, Cloud, and land Elevation Satellite (ICESat).

Researchers say that the recent seasonal acceleration could be in part due to conditioning going on in the Arctic. For example, research by Jennifer Kay of the National Center for Atmospheric Research in Boulder, Colo., and colleagues reported this April in Geophysical Research Letters that reduced cloud cover in 2007 allowed more sunlight to reach Earth, contributing to a measureable amount of sea ice melt at the surface. Reduced cloud cover also contributed to warmer ocean surface temperatures that led to melting of the ice from below.

"Based on what we've learned over the last 30 years, we know that the perennial ice cover is now in trouble," Comiso said. "You need more than just one winter of cooling for the ice to recover to the average extent observed since the measurements began. But the trend is going the other way. A warming Arctic causes the surface water to get warmer, which delays the onset of freeze up in the winter and leads to a shorter period of ice growth. Without the chance to thicken, sea ice becomes thinner and more vulnerable to continued melt."

Source: NASA's Goddard Space Flight Center

Explore further: For the first time scientists map elevation changes of Greenlandic and Antarctic glaciers

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User comments : 4

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3 / 5 (8) Sep 28, 2008
Its a lie! Ice doesnt melt, i have proof!
Assume a Ladder
3.1 / 5 (7) Sep 28, 2008
sea ice melted faster during that period than ever before.

I am shocked (SHOCKED!!!) to discover that the max melting rate this year exceeded that of any other year in our extensive 30-year data set.

I mean, really, it is utterly, totally, and without question inconceivable that our data - which, after all, covers approximately 0.000000667% of the Earth's 4.5 billion-year existence - doesn't indicate the set of all possible "normal" melting rates, so anything outside our baseline data must be extraordinary and cause for immediate concern.

This article is sloppy tripe, at best.

1. Assuming a human life-span of 100 years, 30 years of Earth's existence is the equivalent of roughly 21.04 seconds of a human's life. (For that matter, the 12000 years since the beginning of the Neolithic translate to around 2 hours and 20 minutes of a human lifetime).

2. The pretty picture and its associated graph look nice, but are uninformative at best and misleading at worst. The map shows the "long-term" (1979-2000) median minimum ice sheet (why stop in 2000? Why not 1999 or 2006 or 1985?), but tells us nothing about the variance, prior minimum and maximum, standard deviation, or even the mean. If I sample the net worth of 30 households in my neighborhood, where 20 are young, 1st-time homeowners and 10 are retired empty-nesters with no debt, what value does the median net worth have? Can it really tell you something useful about my neighborhood, let alone the entire state, country, or world? And how does charting the "average" (mean? median? mode?) daily sea ice retreat against 2 apparent outliers tell us anything useful without the afformentioned variance, standard deviation, etc? Of course, it doesn't.

3. With all we know about the geologic history of our planet, how we can possibly proceed with "science" that presumes a static environment is beyond my comprehension. Western society has developed an unfortunate and sickening arrogance regarding mankind's impact on the Earth. Basically, there is an implicit assumption that "natural" changes (a la evolution) ceased with the advent of "scientific man", and that all subsequent changes to our suddenly static planet were the result of man's "interference" with nature (as if we aren't PART of nature). This manifests itself everywhere from the dogma of climate change, to the introductory movie at Volcano National Park on Hawaii, where the narrator describes the "pristine" environment created when Polynesian explorers brought their domestic animals to the islands, as compared to the invasive and destructive results of Western explorers arriving in the 19th century. Strip away everything else, and you have two separate instances of the same event: human explorers introduce alien species into an isolated ecosystem. To paraphrase Hamlet, the only thing that makes either event "good" or "bad" is our perception. I'm not saying that man doesn't impact the world in ways large and small, but I am saying that we have a tendency to over-estimate our own importance.

And no, I'm sure none of this has to do with employing alarmist rhetoric to scare up research sponsors and grant money. That can't be why climate change has seen what is possibly the fastest formation of a "scientific consensus" ever for a question this complicated.

Please, try to think for yourselves just a little bit. It won't hurt much, I promise.

3.5 / 5 (6) Sep 28, 2008
Anything coming out of Hansen and GSFC is suspect. (It hurts to say that but Hansen is anything but unbiased and runs GSFC as his personal fiefdom.) They couldn't have the lowest ice coverage so they've gone for a different 'most'. Even saying the ice coverage was the least after 2007 is misleading since satellite coverage of the poles happened AFTER the last low ice period in the 1920s through 1940s when the ice retreated to 85 degrees North latitude.
1.7 / 5 (3) Sep 28, 2008