Minimum sea ice extent in the Arctic now

In the middle of September every year the minimum sea ice extent appears in the Arctic Ocean – so also this year. Both the Northeast- and Northwest- passages are ice free and open for ship traffic. According to the ArcticROOS analysis of satellite microwave data the minimum sea ice area occurred on September 8th 2010 with an ice area of 4.12 mill. km2 in the Arctic Ocean. The sea ice area was then 16% larger that the previous minimum observed in 2007.

The ice area during the 2010 minimum ice extent in the Arctic Ocean (Figure 1) is 4.12 mill. km2 (on 8/9/2010) or 300 000 km2 larger than minimum in 2008 and 550 000 km2 larger than the previous minimum record from 2007, when the ice area reached 3.57 million km2 (Figure 2).
Both the Northeast Passage, along the Siberian coast, and Northwest Passage, along the Canadian coast, are open this year. The near shore ice conditions have this year made it possible also for sailboats to be close (yet not completely through) to make a circumpolar voyage around the Arctic Ocean. The Norwegian Børge Ausland and the Russian ”Peter the 1ste” expeditions are now both in the Northwest Passage (in Cambridge Bay) after sailing along the entire Russian coast and through the Beaufort Sea.

Natural variability in meteorological and oceanographic conditions are essential for the intra-annual variations of the sea ice cover in the Arctic, now 32 years long records of satellite observations document clear trends in their changes (Figure 3). During the last three decades the minimum sea ice area during the fall – the sea ice that form the basis for the thicker multi-year sea ice the following winter – has declined by 9.05 % per decade (based on monthly data updated per 31st August, 2010). In comparison the maximum winter sea ice area has declined only by 2.83% per decade and the annual average ice area by 4.31% per decade. These trends indicate an accumulative effect of the large reductions of sea ice coverage during the last four summers – caused by the thinning of the Arctic sea ice cover - on the sea ice melting the following summer season.

AcrticROOS estimate both the sea ice area and sea ice extent - most similar service are limited to the ice extent, but are all using the same satellite data sources. In estimation of the sea ice area both completely and partly ice-free areas (large leads etc.) within the ice-covered areas are subtracted from the total ice extent to obtain the actual sea ice covered area. Accordingly, ArcticROOS estimates a total sea ice area of 4.12 mill km2 on the 8/9/2010, while e.g. National Snow and Ice Data Center (NSIDC) reports a minimum sea ice extent on 4.76 mill. km2 on the 10/9/2010. Also the different processing algorithms used contribute to differences in the actual estimates of the sea ice coverage. A comparison of the different processing algorithms is found at http://arctic-roos.org/observations/comparison-of-algorithms.

Figure captions;
Figure 1; Sea ice extent and concentration in the Arctic on 8th September 2010, based on data from the American microwave satellite sensor AMSR-E.

Figure 2; Seasonal variation of the daily sea ice area for the Arctic Ocean. Average for the yeas 1979-2006 (sort), daily values for the years 2007 (purple), 2008 (green), 2009 (blue) and 2010 (red) based on microwave satellite data retrieval of sea ice area. Updated per 14/9/2010.

Figure 3: Monthly deviation in sea ice area in the Arctic Ocean from 1979 to 31. August 2010.
All figures source: http://arctic-roos.org.

Daily updated satellite data and information is found at:

http://arctic-roos.org