Sea Ice Extent for 2013

[Lauren Johnson]

Although I have posted that the volume of polar ice is the big number, and that the extent is a much more volatile number, here is the 2013 update. In short, up from last year but still well within the trend of the latest decades.

On September 13, Arctic sea ice reached its likely minimum extent for 2013. The minimum ice extent was the sixthlowest* in the satellite record, and reinforces the long-term downward trend in Arctic ice extent. Sea ice extent will now begin its seasonal increase through autumn and winter. Meanwhile, in the Antarctic, sea ice extent reached a record high on September 18, tied with last year's maximum.Please note that this is a preliminary announcement. Changing winds could still push ice floes together, reducing ice extent further. NSIDC scientists will release a full analysis of the melt season in early October, once monthly data are available for September.
[B]Overview of conditions[/B]

Figure 1. Arctic sea ice extent for September 13, 2013 was 5.10 million square kilometers (1.97 million square miles). The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

On September 13, 2013, sea ice extent dropped to 5.10 million square kilometers (1.97 million square miles). This appears to have been the lowest extent of the year. In response to the setting sun and falling temperatures, ice extent will now climb through autumn and winter. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower. The minimum extent was reached two days earlier than the 1981 to 2010 average minimum date of September 15.
[B]Conditions in context[/B]

Figure 2. The graph above shows Arctic sea ice extent as of September 19, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High-resolution image

This year's minimum was 1.69 million square kilometers (653,000 square miles) above the record minimum extent in the satellite era, which occurred on September 16, 2012, and 1.12 million square kilometers (432,000 square miles) below the 1981 to 2010 average minimum.
Varying distribution of ice in 2013 versus 2012

Figure 3. This image compares differences in ice-covered areas between September 13, 2013, the date of this year's minimum, and September 16, 2012, the record low minimum extent. Light gray shading indicates the region where ice occurred in both 2013 and 2012, while white and dark gray areas show ice cover unique to 2013 and to 2012, respectively. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
High-resolution image

Comparing this year's minimum extent to 2012, while extent was higher on average this year, there were variations from region to region. There was considerably higher sea ice extent in the Beaufort, Chukchi, and East Siberian sea regions, with the ice edge several hundred kilometers farther south compared to last year. This year the Canadian Archipelago also retained much more ice, keeping the Northwest Passage closed. The most notable area of less ice this year compared to last was off the east coast of Greenland, south of Fram Strait. Other small areas of decreased extent were found north of the Kara and Laptev seas.
See an animation of this summer's sea ice extent produced by the NASA Scientific Visualization Studio at http://svs.gsfc.nasa.gov/goto?4104.
Previous minimum Arctic sea ice extents**

[TABLE="width: 0"]
[TR]
[TH] YEAR[/TH]
[TH="bgcolor: #F6F6F6, colspan: 2"]MINIMUM ICE EXTENT[/TH]
[TH="width: 110, bgcolor: #F6F6F6"]DATE[/TH]
[/TR]
[TR]
[TH="width: 196, bgcolor: #F6F6F6"]IN MILLIONS OF SQUARE KILOMETERS[/TH]
[TH="width: 221, bgcolor: #F6F6F6"]IN MILLIONS OF SQUARE MILES[/TH]
[/TR]
[TR]
[TD]2007[/TD]
[TD]4.17[/TD]
[TD]1.61[/TD]
[TD]September 18[/TD]
[/TR]
[TR]
[TD]2008[/TD]
[TD]4.59[/TD]
[TD]1.77[/TD]
[TD]September 20[/TD]
[/TR]
[TR]
[TD]2009[/TD]
[TD]5.13[/TD]
[TD]1.98[/TD]
[TD]September 13[/TD]
[/TR]
[TR]
[TD]2010[/TD]
[TD]4.63[/TD]
[TD]1.79[/TD]
[TD]September 21[/TD]
[/TR]
[TR]
[TD]2011[/TD]
[TD]4.33[/TD]
[TD]1.67[/TD]
[TD]September 11[/TD]
[/TR]
[TR]
[TD]2012[/TD]
[TD]3.41[/TD]
[TD]1.32[/TD]
[TD]September 16[/TD]
[/TR]
[TR]
[TD]2013[/TD]
[TD]5.10[/TD]
[TD]1.97[/TD]
[TD]September 13[/TD]
[/TR]
[TR]
[TD]1979 to 2000 average[/TD]
[TD]6.70[/TD]
[TD]2.59[/TD]
[TD]September 13[/TD]
[/TR]
[TR]
[TD]1981 to 2010 average[/TD]
[TD]6.22[/TD]
[TD]2.40[/TD]
[TD]September 15[/TD]
[/TR]
[/TABLE]

* According to near-real-time data, this year's minimum extent is slightly lower than 2009. However, the ranking between 2009 and 2013 is close, and may change once the final version of the data are processed. See our Frequently Asked Questions: Do your data undergo quality control? for more information about near-real-time data.
** Note that the dates and extents of the minimums have been re-calculated from what we posted in previous years; see our Frequently Asked Questions for more information.

This post comes from Arctic Sea Ice News and Analysis blog.

http://nsidc.org/arcticseaicenews/2013/0...-for-2013/