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Arctic/Antarctic Sea Ice 2021/22

  • 16-09-2021 10:36pm
    #1
    Registered Users Posts: 8,200 ✭✭✭ Gaoth Laidir


    We're near or at the annual Arctic minimum extent about now. Latest extent is 4.728 million km², one of the highest extents of the past decade. Some good freezing already occurring in the Siberian Arctic area.

    An odd summer’s end | Arctic Sea Ice News and Analysis (nsidc.org)

    As of September 15, Arctic sea ice extent stood at 4.73 million square kilometers (1.83 million square miles), placing it tenth lowest in the satellite record for the date. While extent continues to decline as of this post, the seasonal minimum is likely to occur soon, depending on how much heat remains in the upper ocean and on winds, which can compact the ice cover or spread it out. If the winds push the ice poleward, this may further reduce the total extent. Nevertheless, the seasonal minimum extent promises to be one of the highest of the past decade—only 2013, 2014, and 2018 are currently tracking above the 2021 sea ice extent.

    It has been an odd summer. While fairly cool and stormy summer conditions limited summer melt, as discussed in our earlier post, the amount of multiyear ice is at a record low, roughly one-fourth of the amount seen in the early 1980s. Ice loss the first two weeks of September primarily occurred in the Beaufort and Chukchi Seas, and to a lesser extent also surrounding Severnaya Zemlya. As seen in Advanced Microwave Scanning Radiometer 2 (AMSR-2) imagery (Figure 1b), areas of low concentration ice persist in the Beaufort and Chukchi Seas; how much of this ice melts away largely depends on ocean heat. Satellite mapping of sea surface temperatures shows much of the open ocean surrounding the low ice concentration area is already near the freezing point. By contrast, the compact, well-defined ice edge along most of the Russian side of the Arctic Ocean indicates that freezing is already underway in this area.

    Air temperatures at the 925 hPa level (about 2,500 feet above the surface) as assessed over the first 13 days of September were near average over most of the Arctic Ocean. Temperatures from 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average were the rule along the coasts of the Kara and Laptev Seas (Figure 2a). In sharp contrast to the persistent pattern of low pressure over the Arctic Ocean characterizing this summer, the first 13 days of September saw high average air pressure (Figure 2b).




Comments

  • Registered Users Posts: 8,200 ✭✭✭ Gaoth Laidir


    Of course that last chart should indicate "2021" instead of "2020". The new site won't let me delete or edit the chart.


    Post edited by Gaoth Laidir on


  • Registered Users Posts: 21,811 ✭✭✭✭ Kermit.de.frog


    Looks like we have reached ice pack minima for this year in the Arctic. Looking at the surface temperature profile over the coming week or so should see the first meaningful expansions toward the East Siberian and Beaufort Seas, shoring up of the pack outside the Laptev Sea as well. It will be a while yet with Laptev and that side itself. Generally sustained sub -1.7c required for sea ice formation.



  • Registered Users Posts: 8,200 ✭✭✭ Gaoth Laidir


    It's fairly safe to say that we can take yesterday's figure of 4.724 million km² as our minimum for the year, given that it's actually a 5-day mean and is unlikely to go lower. It ranks as 12th in the satellite era (43 years).

    The overall trend in annual minimum extent for the whole period (1979-2021) is -806,000 km²/decade.

    The decadal trends for the 4 decades are shown below, both annual minimum extent (red) and annual maximum extent (blue). Strangely, the trend in annual minimum extent for the most recent period (the 12 years 2010-2021) is about 7 times less than that of the first period (1980-1989) and is 42 times less than that of the worst period, 2000-2009. There has been practically no net loss in minimum extent in the past 12 years (just -44,000 km²/decade).

    The 22 years of the 21st century so far show a trend of -907,000 km²/decade, which is 2.8 times higher than 1980-1999 (-322,000 km²/decade), pretty much all due to the large losses in 2000-2009.

    Annual maximum extent (March) is showing an increasingly negative trend, with 2010-2021 running 2.6 times higher than 1980-1989. The 21st century trend (-411,000 km²/decade) is 1.6 times higher than that of 1980-1999 (-258,000 km²/decade)

    As outlined above, multi-year ice is at a record low this year, so the lower maximum extents are having some effect.

    Al graphs mine and from the NSIDC data source here.




  • Registered Users Posts: 19,161 ✭✭✭✭ Akrasia


    I'm glad that the ice loss in the arctic isn't as fast as it could theoretically have been. I certainly do not look forward to the imminent first ice free summers.

    Any help we can get from mother nature (chaotic weather impacting conditions for ice formation) to preserve the arctic ice for as long as possible is greatly welcomed.

    We need to make the most of this time. When the ice is gone, it sets off feedbacks that mean it's not likely to come back any time soon, and there are some potential consequences for the AMOC and the polar vortex that could impact us directly here in Ireland



  • Registered Users Posts: 8,200 ✭✭✭ Gaoth Laidir


    Based on the most recent trend, ice-free would occur in about 100 years. Not that imminent,



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  • Registered Users Posts: 19,161 ✭✭✭✭ Akrasia


    and based on the overall trend, it will be within the next few decades

    And the IPCC estimate it will be around mid century

    I hope you’re right Gaoth, although extracting the flat parts of trend lines and showing them on their own, (I think there’s a term for that) and then projecting them forwards isn’t the most rigorous analysis I’ve ever seen



  • Registered Users Posts: 8,409 ✭✭✭ Danno


    Likewise starting at 1979 and projecting forward isn't the most rigorous either. It's known that the arctic has been in states with alot less ice than now over past centuries. Yet the C02 levels were lower. What gives?



  • Registered Users Posts: 8,200 ✭✭✭ Gaoth Laidir


    I said on current trends. I posted an extensive set of data, so you can't accuse me of cherrypicking. We'd want to be seeing a fairly massive drop off a cliff to see ice-free by mid-century. Even at your overall 42-yr trend of 800,000 km2/decade it won't make it.



  • Registered Users Posts: 6,033 ✭✭✭ Oneiric 3


    According to this graph, September Arctic sea ice is losing, on average, 12% of extent per decade, or 1.2% per year.


    New Moon



  • Registered Users Posts: 22,407 ✭✭✭✭ blanch152


    At that rate - 84k km2 per year - it will take 56 years to see ice-free Septembers, so 2076, so not within most people's lifetime.



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  • Registered Users Posts: 19,161 ✭✭✭✭ Akrasia


    On what basis do you expect this to be a linear trend?



  • Registered Users Posts: 8,200 ✭✭✭ Gaoth Laidir


    Antarctic Extent

    The Antarctic has been much more stable over the decades, with very little trend either way. The 2021 minimum (back in February), just like the Arctic minimum, ranks 12th out of the 43 years.

    There has been a downward trend in both maximum and minimum in the most recent period of 2010-2021, following a period of no real trends either way. Overall, the 1979-2021 trend is flat or slightly increasing, especially for the maximum extent (+97,000 & +29,000 km²/decade, respectively).




  • Registered Users Posts: 5,852 ✭✭✭ pauldry


    Arctic trend looks pretty benign this year but there was a lot of dispersion of poor quality ice.

    Always some parts of Arctic fare worse than others. This year Greenland had a pretty serious year melt wise and rain was even observed at Summit for the first time on record. Its normally -30c here in Summer.



  • Registered Users Posts: 22,407 ✭✭✭✭ blanch152


    Some people on here expect an increasing trend of melt, some claim the melt isn't happening at all. Plotting a middle course of the linear trend to see where it goes is useful in that context.



  • Registered Users Posts: 8,200 ✭✭✭ Gaoth Laidir


    The average daily maximum around then is -11 to -14 °C, but isolated days close to zero do occur.




  • Registered Users Posts: 8,200 ✭✭✭ Gaoth Laidir


    This year's minimum Arctic extent has now been achieved and lies 12th lowest in the 44-year satellite record, one place higher than last year's 13th.

    On a decadal scale, the period 2010-2022 has been the only period on record to show an actual increasing trend in annual minima, albeit very small. Good to know that we've at least 13 more years to wait for an ice-free September. Surely that's positive news that The Guardian should be running with?



    Post edited by Gaoth Laidir on


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