Arctic sea ice now lowest on satellite record

Tuesday 28 August 2012, 16:20

Paul Hudson Paul Hudson

The extent of sea ice in the Arctic region has dropped sharply in the last few months.

Only in April, Arctic sea ice had staged an impressive recovery and was close to the 1979-2012 average, reaching levels not seen in April for over 10 years.

But yesterday, the National Snow and Ice data centre reported that the extent of Arctic sea ice shrank to 1.58 million square miles, breaking the previous record set in the summer of 2007, based on satellite data which was first gathered in 1979.



Usually the minimum ice extent is not reached until September, suggesting that further ice loss is likely.

Including this year, the six lowest ice extents in the satellite record have occurred in the last six years.



And most scientists, whilst accepting that some of the decline in sea ice is likely to be down to natural factors such as prevailing weather conditions and natural ocean cycles, believe a substantial proportion is down to man-made influences such as global warming due to higher greenhouse gases in the atmosphere.

The big worry is that continued melting sea ice would cause serious feedback mechanisms to kick-in.

Firstly with less sea ice to reflect incoming solar radiation back into space, the sea will warm more quickly than would otherwise be the case, speeding up global warming.

And secondly, natural methane trapped under the sea-bed by permafrost could be released. Methane is a much more powerful greenhouse gas than carbon dioxide, and would also accelerate global warming.

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    Comment number 1.

    "Only in April, Arctic sea ice had staged an impressive recovery and was close to the 1979-2012 average"

    That was purely sea ice extent. Volumes have been steadily going down to the point that some researches refer to much of the 'recovered' ice as rotten or a slushie. That accounts somewhat for the steep decline from near average extent to record low.

  • rate this
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    Comment number 2.

    Yes, and crucially very different from the Little Ice Age (which certain groups seem convinced will re occur today) when arctic ice extent increased substantially - according to past research.

  • rate this
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    Comment number 3.

    We are currently in an inter-glacial period between ice ages.
    During such periods, the Earth is ice-free, even at the poles.
    About 12500 years ago, Britain was covered in an ice sheet, since when
    the extent of the ice has been declining.
    Is it surprising that the ice is still declining?
    Would it be a good thing if the ice was extending?

  • rate this
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    Comment number 4.

    The LIA is interesting. Some say we are still exiting from the LIA so the warming and ice loss are due to that. Others are saying we are entering a LIA and cooling has started. Both can't be right (though both could have wrong conclusions!).

  • rate this
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    Comment number 5.

    A quick word on the satellite record

    According to the final report of working group 1 of the intergovernment panel on climate change sea-ice extent has been measured by satellits since the early 1970s

    http://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_full_report.pdf

    "Especialy importantly, satellite observations have been used to map sea-ice extent routinley since the early 1970s. The American Navy Joint Ice Centre has produced weekly charts which have been digitised by NOAA"

    Page 224

 

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