Sea Ice Extent Low Record Smashed. Still no Bottom Yet.

September 9, 2011

This and more at Arctic Sea Ice Blog:

The Arctic sea ice extent index calculated by a University of Bremen research team led by Dr. Georg Heygster reached a new historical low point of 4.24 million kmon September 8. The previous one-day minimum was 4.27 million km2 on September 17, 2007 (Figure 1). The usual melt season is not yet over, however, so 2011 extent could decline further.

The Uni Bremen researchers announced the new ice extent minimum in a press release (in German). An English translation of the text, provided by Dr. Heygster, appears below (or go here for a version with graphics).

Arctic sea ice extent small as never before

 Alerting message from the Arctic: The extent the the Arctic sea ice has reached on Sep. 8 with 4.240 million km2 a new historic minimum. Physicists of the University of Bremen now confirm the apprehension existing since July 2011 that the ice melt in the Arctic could further proceed and even exceed the previous historic minimum of 2007. It seems to be clear that this is a further consequence of the man-made global warming with global consequences. Directly, the livehood of small animals, algae, fishes and mammals like polar bears and seals is more and more reduced.

The work group of Georg Heygster at the University of Bremen observes since many years the the sea ice at both poles. With the support of the ESA/GMES project Polar View, daily maps  of the sea ice extent are publicly provided at http://www.iup.uni-bremen.de/seaice/amsr/. The retreat of the summerly sea ice since 1972 amount to 50%. For algae and small animals living at the lower side of the ice, less and less living environment remains since they need a certain time to settle there. They are at the beginning of the food chain for fishes, mammals and also man.

The extent of the Arctic sea ice shows a pronounced yearly cycle, with about 15 million km2 in March and five million km2 in September. In 2007 however, it was only 4.267 million km2, the previous smallest value since start of satellite observations in 1972, and most probably since the last climate optimum about 8000 years ago. The current value is 27,000 km2 or 0.6% lower and could even be undercut in the next weeks. The ice maps of the University of Bremen show also that in this year, the Northwest and Northeast passages are simultaneously ice free. This had happed for the first time in 2008, and in 2009 the German shipping company Beluga has traveled it commercially for the first time. Recently, it was crossed in the record time of 8 days only by a tanker, traveling from Huston, Texas to Map Ta Phut, Thailand.

Already in July the new record minimum had been expected because in this month the sea ice extent was minimum, compared with the same month in other years. Due to the high sun elevation and long days in July, the sea ice extent in this period is climatologically more important than that of September. The increased insolation into the open water heat it up, leading to an additional sea ice melt from the bottom and delays formation of new ice in autumn. Moreover, the sea ice retreat can no more be explained with the natural variability from one year to the next, caused e.g. by weather influence. Climate models show rather, that the reduction is related  to the man-made global warming which, due to the ice albedo effect, is particular pronounced in the Arctic: an ice area melted by a small temperature increase will then as open water have a much darker surface, absorb more solar radiation as before which causes an additional heating.

In contrast to the minimum in September, the yearly maximum in March decreases less (Figure 3): despite the reduced in in summer, in winter large areas of the arctic ocean freeze up. However, this first-year ice is clearly thinner than multiyear ice having survived one summer. Therefore, in summer first-year ice melts much easier than multiyear ice and after a historic minimum, the ice cover needs even in an unchanged climate several year to fully recover. Observation of the last years show further, that the sea ice thickness reduces, so that the total mass of Arctic sea ice decreases even more drastically than the sea ice extent.

The daily sea ice maps of the University of Bremen are based on observations of the Japanese microwave sensor AMSR-E, in orbit on board the NASA spacecraft Aqua. The institute receives the data from two servers in the US and Japan and produces the maps based on these observations.

18 Responses to “Sea Ice Extent Low Record Smashed. Still no Bottom Yet.”

  1. SJ Says:

    I was listening to Mark Serrez from NSIDC give a talk last night, and I think their number for the 2007 minimum was about 4.13 million… Just different methods?

    (Yes, here’s a link http://www.colorado.edu/news/releases/2007/362.html)


  2. Another big melt down

    without those aerosols I wonder where we would be in warming now….

    • otter17 Says:

      Aerosol dimming is one subject that very few people in the general public seem to know about. When I communicate, I say something like this:

      I tell people that the aerosols can drop out of the atmosphere within a matter of weeks, and they cover up the effects of the long-lived greenhouse gases. If we are lucky, the increase in global warming force will only be 1.5x when all dimming aerosol emissions are removed. If we are unlucky, that figure will be more like 3x. Most likely, the figure is 2x right now.

      I like the BBC documentary “Global Dimming”. It is a pretty good primer on the subject and how scientists came to discover global dimming.

      • otter17 Says:

        youtube.com/
        watch?v=bLfBXRPoHRc

        • greenman3610 Says:

          IPCC chapter 2 deals with this, page 183.
          http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf

          they weren’t too excited one way or the other about it, due to very limited data.

        • otter17 Says:

          They weren’t too excited about the question of where the Earth’s climate would be without the aerosols? I guess few people have modeled a hindcast scenario that discounts aerosols?

          Or they weren’t too excited since the data on the aerosol forcing itself was scattered? To me, it seems reasonable to use the expected value and range of the probability distribution for the total aerosol forcing estimates to see that there is some reason to get excited.

          • greenman3610 Says:

            there is an extended discussion of aerosols. The movie features a study that was done after planes stopped flying on 9/11, and had some interesting results in terms of temps – diurnal temp differences etc – but the writeup suggested that there was insufficient data on that particular point to go as far as the movie suggests.
            lots of info on the various other aerosol sources, tho.

          • otter17 Says:

            Ah, got it. Thanks for clarifying.

  3. kokuaguy Says:

    Peter, please email me so I will know why my comment was not deemed appropriate for posting. I know of no other way to communicate with you other than this. I apologize if I violated some guideline of the site that I am not familiar with.

  4. otter17 Says:

    “The previous one-day minimum was 4.27 million km2 on September 17, 2007.”

    I guess there is another week left in the melting season, roughly. I wonder if this year it will be even longer by like a day or two. It would be interesting to see the data on melt season begin/end dates and how the melt season has lengthened over the years. Maybe I ought to check out NSIDC.

  5. Steven Raine Says:

    There’s a good sea-ice graph here :

    which seems to show its pretty much a tie for 2007 and this year for lowest ever sea ice. I think it gets updated regularly and could be agood way tokeep track of things.


  6. […] Sinclair yells “Sea Ice Extent Low Record Smashed. Still no Bottom Yet.” on Sep 9. And “Arctic sea ice has melted to a level not recorded since satellite observations […]


  7. […] all the other institutions that show either a record low for 2011 or a “tie” with 2007. University of Bremen already announced it is a new record low. In my opinion, given the error margin of the measurement and algorithms, 2007 and 2011 basically […]


  8. […] Sinclair yells “Sea Ice Extent Low Record Smashed. Still no Bottom Yet.” on Sep 9. And “Arctic sea ice has melted to a level not recorded since satellite […]


  9. […] will remember that last week the University of Bremen, another important sea ice data set, concluded that the sea ice was now at an all time low minimum. […]


  10. […] In September, Germany’s University of Bremen reported that sea ice had hit a record low, based on data from a Japanese sensor on NASA’s Aqua satellite. The U.S. National Snow and Ice Data Center, using a different satellite data set, reported that the sea ice coverage in 2011 was the second-lowest on record, after the record set in 2007.  […]


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