Figure 1. Arctic sea ice extent for December 2010 was 12.00 million square kilometers (4.63 million square miles). The magenta line shows the 1979 to 2000 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data. —Credit: National Snow and Ice Data Center
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Overview of conditions

Arctic sea ice extent averaged over December 2010 was 12.00 million square kilometers (4.63 million square miles). This is the lowest December ice extent recorded in satellite observations from 1979 to 2010, 270,000 square kilometers (104,000 square miles) below the previous record low of 12.27 million square kilometers (4.74 million square miles) set in 2006 and 1.35 million square kilometers (521,000 square miles) below the 1979 to 2000 average.

As in November, ice extent in December 2010 was unusually low in both the Atlantic and Pacific sides of the Arctic, but particularly in Hudson Bay, Hudson Strait (between southern Baffin Island and Labrador), and in Davis Strait (between Baffin Island and Greenland). Normally, these areas are completely frozen over by late November. In the middle of December, ice extent stopped increasing for about a week, an unusual but not unique event.

Figure 2. The graph above shows daily Arctic sea ice extent as of January 2, 2011, along with daily ice extents for previous low-ice-extent years in the month of November. Light blue indicates 2010-2011, pink shows 2006-2007 (the record low for the month was in 2006), green shows 2007-2008, and dark gray shows the 1979 to 2000 average. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.—Credit: National Snow and Ice Data Center
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Conditions in context

The low ice conditions in December occurred in conjunction with above-average air temperatures in regions where ice would normally expand at this time of year. Air temperatures over eastern Siberia were 6 to 10 degrees Celsius (11 to 18 degrees Fahrenheit) above normal in December. Over the eastern Canadian Arctic Archipelago, Baffin Bay/Davis Strait and Hudson Bay, temperatures were at least 6 degrees Celsius (11 degrees Fahrenheit) higher than average. Southern Baffin Island had the largest anomalies, with temperatures over 10 degrees Celsius (18 degrees Fahrenheit) higher than normal. By sharp contrast, temperatures were lower than average (4 to 7 degrees Celsius, 7 to 13 degrees Fahrenheit) over the Alaska-Yukon border, north-central Eurasia, and Scandinavia.

The warm temperatures in December came from two sources: unfrozen areas of the ocean continued to release heat to the atmosphere, and an unusual circulation pattern brought warm air into the Arctic from the south. Although the air temperatures were still below freezing on average, the additional ocean and atmospheric heat slowed ice growth.

Figure 3. Monthly December ice extent for 1979 to 2010 shows a decline of 3.5% per decade. —Credit: National Snow and Ice Data Center
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December 2010 compared to past years

December 2010 had the lowest ice extent for the month since the beginning of satellite records. The linear rate of decline for the month is –3.5% per decade.

Figure 4. Air temperatures were higher than normal over Baffin Island, Hudson Bay, and eastern Siberia for the month of December, which was associated with low sea ice extent in those areas. The temperature pattern resulted from a negative phase of the Arctic Oscillation.—Credit: NSIDC courtesy NOAA/ESRL PSD
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Negative phase of the Arctic Oscillation

As in December 2009, a strongly negative phase of the Arctic Oscillation dominated the middle and high latitudes of the Northern Hemisphere in December 2010, bringing higher-than-normal pressures to the Arctic region, with lower-than-normal pressures in middle latitudes. However, unlike 2009, when higher-than normal pressures centered near the central Arctic , in December 2010 higher pressures centered near Iceland and the eastern tip of the Aleutians in the Pacific, and yielded a different pattern of winds. As a result, different areas experienced warm anomalies in 2010, and a different pattern of ice extent emerged.

Our January 5, 2010 post discussed the connection between very warm temperatures over much of the high Arctic in December 2009 and a strongly negative phase of the Arctic Oscillation.

Figure 5. This full-year graph puts 2010 sea ice extent in context. The gray line shows the 1979 to 2000 climatology, thick blue-gray indicates the 1979 to 2008 (30-year) climatology, dashed green shows 2007, and 2009 is shown in sky blue. Sea Ice Index data.—Credit: National Snow and Ice Data Center
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2010 year in review

Despite a late date of the maximum in winter sea ice extent, the minimum sea ice extent for September 2010 was third lowest in the 1979 to 2010 satellite record, above only 2007 (the record low) and 2008. The late summer of 2010 saw an open Northwest Passage: this year, the deep water channel (the northern route) from M’Clure Strait to Lancaster Sound was navigable. The Northern Sea Route along the Siberian coast also became briefly navigable.

2010 started out with a highly negative phase of the Arctic Oscillation, an atmospheric pattern that in the past has favored the survival of old ice through the winter, and more ice at the end of this summer. But this tendency seems to be changing. A recent study led by Julienne Strove of NSIDC showed that while wind patterns linked with the strongly negative Arctic Oscillation winter of 2009-2010 transported much old ice into the southern Beaufort and Chukchi Seas, most of this ice later melted. It may be that with a warmer Arctic, old rules regarding links between the atmospheric pressure patterns and sea ice extent no longer hold. So far the winter of 2010-2011 has also had a strongly negative Arctic Oscillation, but it is not yet clear how this pattern will affect summer sea ice.

Figure 6. The graph of Antarctic sea ice extent as of January 3, 2011. Light blue indicates 2010-2011, dark blue shows 2009-2010, and dark gray shows the 1979 to 2000 average. The gray area around the average line shows the two standard deviation range of the data—Credit: National Snow and Ice Data Center
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A note on Antarctica

While sea ice is growing in the Arctic, it is early summer in the Antarctic and sea ice is melting. For the past four months, Antarctic sea ice extent has remained well above average. The high ice extent around Antarctica appears to relate to a persistently positive phase of the Southern Annular Mode—an Antarctic counterpart to the Arctic Oscillation—and to the mild La Niña conditions in the Pacific. In December 2010, the monthly mean Southern Annular Mode index was lower, and Antarctic sea ice extent had dropped back to within about standard deviation of the mean.

For more information about Antarctic sea ice, see the Frequently Asked Questions section.

Antarctic sea ice data is available on the Sea Ice Index.

New sea ice data

NSIDC has recently released a new sea ice extent product, called the Multisensor Analyzed Sea Ice Extent (MASIE). The MASIE project is a collaborative effort with the U.S. National Ice Center to provide a daily high-resolution sea ice extent estimate based on the NOAA Interactive Mapping System (IMS) product. This new product is considered more accurate for tracking the current position of the ice edge; for climate studies, the passive microwave product (on which Arctic Sea Ice News & Analysis is based) is preferred for a more consistent, long-term average. For more information, read an article about the product at the NSIDC Monthly Highlights Web site.

Further reading

Stammerjohn, S. E., D. G. Martinson, R. C. Smith, X. Yuan, and D. Rind, 2008. Trends in Antarctic annual sea ice retreat and advance and their relation to El Nino — Southern Oscillation and Southern Annular Mode variability. Journal of Geophysical Research, 113, C03S90, doi: 10.1029/2007JC004269.

Stroeve, J.C., J. Maslanik, M. C. Serreze, I. Rigor, W. Meier, and C. Fowler. 2010. Sea ice response to an extreme negative phase of the Arctic Oscillation during winter 2009/2010. Geophysical Research Letters. In Press.

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