Posted by: JohnnyRook | January 28, 2009

Quick Update on Arctic Sea Ice–January 28, 2009

The hiatus in the refreezing of the Arctic continues. Today’s NSIDC data shows that this year’s refreezing has now dropped below the rate for 2006-2007, the year of the record summer sea-ice melt. Here are the latest NSIDC maps and graphs.

Both images from National Snow and Ice Data Center

I have not seen an explanation yet for why this is happening. A similar phenomenon occurred in December. At that time the NSICD offered the following explanation:

Reasons for December’s pause in ice extent change

December’s week-long pause in expansion of the ice cover appears to have been caused, at least in part, by an anomalous atmospheric pressure pattern. High pressure over Alaska and the European Arctic, coupled with unusually low pressure east of Greenland and over eastern Siberia, brought warm southerly winds over much of the Arctic Ocean. The southerly winds helped keep the ice edge from expanding southward. In addition, warm sea surface temperatures, at least in the Barents Sea, inhibited ice formation.

Chart showing year-long extent lines for 1979-2000 average, 2007, and 2008Figure 4. This timeseries from January through December shows the natural waxing and waning of the Arctic sea ice cover with the seasons. The maximum extent generally occurs in March, the minimum extent in September. Sea ice extent in 2008 (purple) fell well below the 1979 to 2000 long-term average (gray) and was slightly above 2007 (dashed green), in which the lowest summer minimum and the second-lowest winter maximum occurred.

Torsten Hanssen has pointed out the following very interesting web site run by the Japanese Aerospace Exploration Agency (JAXA) where you can download, in spreadsheet format, day-by-day sea ice extent data going back to June 2002. The quickest way to get to the data is to go to this page where you’ll find a very interesting graph.Once you’re on the graph page you can click on the data download button under the graph to download the spreadsheet.

The data here is slightly different from that on the NSIDC graph. After you’ve downloaded the spreadsheet, which is very simple, take a look at the data for January 2009. You’ll notice that sea ice reached it’s maximum extent so far in 2009 on January 19th and that since that date it has stayed below that January 19th figure.

You can also copy the data from January 19, 2007 and paste it next to the corresponding data from 2009. You’ll then see that the two data sets are very close at this point (within 64,000 km2 as of yesterday) and that on January 25th, 2009 the sea-ice extent fell below the January 25, 2007 extent.

I don’t know that one can yet draw any conclusions about this upcoming summer’s sea-ice melt from all of this. That should all be clearer in a month or so. What is clear is this. To the denialists’ chagrin, so far there has not been any big refreeze of sea ice in the Arctic. Indeed, instead it’s tracking very similarly to how it tracked in 2007, the year when the record for minimum summer sea-ice extent was set.

Crossposted at Daily Kos

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Responses

  1. What I don’t understandis the difference in the January 27, 2009 image and the January 2009 monthly image.

    How can the monthly image show more ice overall than the January 27 image? The ice obviously grew through January, yet the Jan 27 image doesn’t show it.

    • Doug,

      I don’t think I understand your question. If ice grew through January 31, (although as we know from the latest comment on the NSIDC site it did not grow linearly) why should it be surprising that the January 31 image (the monthly image) shows more ice than the January 27 image, which was made 4 days earlier?

  2. Compare this, which is the daily snapshot for January 31:
    http://nsidc.org/data/seaice_index/n_extn_daily.html

    To this, which is the monthly snapshot of January:
    http://nsidc.org/data/seaice_index/n_extn.html

    So, the question is how can the monthly snapshot show more ice than the Jan 31 snapshot? Presumably, if the ice is growing, there would be more ice on Jan 31, than the cumulative monthly ice.

    • Doug,

      When I look at the two figures, I’m don’t think that the January monthly average figure does show more ice than the January 31, 2009 figure. I think it’s just distributed differently. I think you would need to see actual daily data. According to the NSIDC in January the ice grew by 1.12 million km2 in January. I compared the NSIDC data with that at JAXA and although the figures are somewhat different they show a similar increase in sea-ice extent.

      Also, sea-ice extent can be influenced by it’s concentration. Currents can cause the sea ice to become more compacted on any given day. Remember, by NSIDC’s definition an area is considered covered with sea ice if it contains 15% sea ice. If sea currents or winds compact that to 25% for example, you will still have the same amount of sea ice although it’s extent will be less because it will be packed more densely into a smaller area.

      During January the ice grew in certain areas and then receded. In other areas the opposite happened. See the map in my latest post on Arctic sea ice, which shows where that happened.


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