NSIDC, NASA Say Arctic Melt Season Lengthening, Ocean Rapidly Warming

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The length of the melt season for Arctic sea ice is growing by several days each decade, and an earlier start to the melt season is allowing the Arctic Ocean to absorb enough additional solar radiation in some places to melt as much as four feet of the Arctic ice cap’s thickness, according to a new study by National Snow and Ice Data Center (NSIDC) and NASA researchers.

Arctic sea ice has been in sharp decline during the last four decades. The sea ice cover is shrinking and thinning, making scientists think an ice-free Arctic Ocean during the summer might be reached this century. The seven lowest September sea ice extents in the satellite record have all occurred in the past seven years.

"The Arctic is warming and this is causing the melt season to last longer," said Julienne Stroeve, a senior scientist at NSIDC, Boulder and lead author of the new study, which has been accepted for publication in Geophysical Research Letters. "The lengthening of the melt season is allowing for more of the sun’s energy to get stored in the ocean and increase ice melt during the summer, overall weakening the sea ice cover."

To study the evolution of sea ice melt onset and freeze-up dates from 1979 to the present day, Stroeve’s team used passive microwave data from NASA’s Nimbus-7 Scanning Multichannel Microwave Radiometer, and the Special Sensor Microwave/Imager and the Special Sensor Microwave Imager and Sounder carried onboard Defense Meteorological Satellite Program spacecraft.

When ice and snow begin to melt, the presence of water causes spikes in the microwave radiation that the snow grains emit, which these sensors can detect. Once the melt season is in full force, the microwave emissivity of the ice and snow stabilizes, and it doesn’t change again until the onset of the freezing season causes another set of spikes. Scientists can measure the changes in the ice’s microwave emissivity using a formula developed by Thorsten Markus, co-author of the paper and chief of the Cryospheric Sciences Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Md.

Results show that although the melt season is lengthening at both ends, with an earlier melt onset in the spring and a later freeze-up in the fall, the predominant phenomenon extending the melting is the later start of the freeze season. Some areas, such as the Beaufort and Chukchi Seas, are freezing up between six and 11 days later per decade. But while melt onset variations are smaller, the timing of the beginning of the melt season has a larger impact on the amount of solar radiation absorbed by the ocean, because its timing coincides with when the sun is higher and brighter in the Arctic sky.

Despite large regional variations in the beginning and end of the melt season, the Arctic melt season has lengthened on average by five days per decade from 1979 to 2013.

Still, weather makes the timing of the autumn freeze-up vary a lot from year to year.

Written By: NASA
continue to source article at nasa.gov

5 COMMENTS

  1. Even for me, this is so easy to understand that I’m deeply puzzled as to how anyone can fail to grasp it; unless they resolutely refuse to refer to the data or even acknowledge its existence.

    And I think that that is precisely what some individuals do do, as has been seen by the refusal of the advocates of a young Earth to recognize the existence of fossils, and any other evidence contrary to what they want, or need, or have been conditioned to believe.

    Such degrees of denial as very strange to me, since they fly in the face of easily accessible and verifiable facts.

    I hesitate to mention the ‘R’ word because doing so has become so hackneyed, but that is what it comes down to I think; every time.

  2. I would be very surprised if this has any effect on the deniers, they simply have become so ingrained in their denial that they would deny any alteration in the climate around them as a conspiracy much as you cannot argue with evolution deniers whatever the evidence..

  3. In reply to #2 by The Orderly Entropianist:

    Boats

    Venice, slowly sinking from degradation and / or rising water from climate change symptoms. Then I thought floating cities, which by coincidence, was the subject of a recent article. It makes mention of a top, if not number one priority – sewage, eww! Let’s not pollute the oceans anymore than they already are.

    (from article)…to reject our natural habitat..

    True, nothing like the feel of terra firma underfoot. Viewed from a different angle, however, we’d be venturing back home, coming full circle, so to speak.

    I’ve been ready ;)

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