Arctic sea ice at minimum extent

Arctic sea ice appears to have reached its lowest extent for the year. The minimum ice extent was the second lowest in the satellite record, after 2007, and continues the decadal trend of rapidly decreasing summer sea ice.

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.

map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent on September 9, 2011 was 4.33 million square kilometers (1.67 million square miles). The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data.—Credit: National Snow and Ice Data Center
High-resolution image


Overview of conditions

On September 9, 2011 sea ice extent dropped to 4.33 million square kilometers (1.67 million square miles). This appears to have been the lowest extent of the year, and may mark the point when sea ice begins its cold-season cycle of growth. However, a shift in wind patterns or late season melt could still push the ice extent lower.

This year’s minimum was 160,000 square kilometers (61,800 square miles) above the 2007 record minimum extent, and 2.38 million square kilometers (919,000 square miles) below the 1979 to 2000 average minimum. Note that our estimated uncertainty for extent is plus or minus 50,000 square kilometers (about 20,000 square miles). The minimum ice extent this year is very close to 2007, and indeed some other research groups place 2011 as the lowest on record. At this point, using our processing and sensor series, the 2011 minimum is a close second.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily Arctic sea ice extent as of September 13, 2011, along with daily ice extents for the previous three lowest years for the minimum ice extent. Light blue indicates 2011, dashed green shows 2007, dark blue shows 2010, purple shows 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
High-resolution image


Conditions in context

The last five years (2007 to 2011) have been the five lowest extents in the continuous satellite record, which extends back to 1979. While the record low year of 2007 was marked by a combination of weather conditions that favored ice loss (including clearer skies, favorable wind patterns, and warm temperatures), this year has shown more typical weather patterns but continued warmth over the Arctic. This supports the idea that the Arctic sea ice cover is continuing to thin. Models and remote sensing data also indicate this is the case. A large area of low concentration ice in the East Siberian Sea, visible in NASA Moderate Resolution Imaging Spectroradiometer (MODIS) imagery, suggests that the ice cover this year is particularly thin and dispersed this year.

Table 1. Previous minimum Arctic sea ice extents
Year Minimum Ice Extent Date
in millions of square kilometers in millions of square miles
2007 4.17 1.61 September 16
2008 4.55 1.76 September 18
2009 5.10 1.97 September 12
2010 4.60 1.78 September 19
2011 4.33 1.67 September 9
1979 to 2000 average 6.71 2.59 September 10
1979 to 2010 average 6.29 2.43 September 12

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

Arctic sea ice nears minimum extent

In the last few days, the decline in Arctic sea ice extent has slowed. NSIDC data show Arctic sea ice extent currently at the second-lowest levels in the satellite record.

map from space showing sea ice extent, continentsFigure 1. The graph above shows ice extent this year, along with daily ice extents for the previous three lowest extent years. Light blue indicates 2011, dashed green shows 2007, dark blue shows 2010, purple shows 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. About the data. —Credit: National Snow and Ice Data Center
High-resolution image


Overview of conditions

On September 10, Arctic sea ice extent was 4.34 million square kilometers (1.68 million square miles). This was 110,000 square kilometers (42,500 square miles) above the 2007 value on the same date. The record minimum Arctic sea ice extent, recorded in 2007, was 4.17* million square kilometers (1.61 million square miles).

The rate of decline has flattened considerably the last few days: Arctic sea ice is likely near its minimum value for the year. However, weather patterns could still push the ice extent lower. NSIDC scientists will make an announcement when ice extent has stopped declining and has expanded for several days in a row, indicating that the Arctic sea ice has reached its lowest extent for the year and has begun freezing over. During the first week of October, after data are processed and analyzed for the month of September, NSIDC scientists will issue a more detailed analysis of this year’s melt season and the state of the sea ice.

NSIDC’s sea ice data come from the Special Sensor Microwave Imager/Sounder (SSMIS) sensor on the Defense Meteorological Satellite Program (DMSP) F17 satellite. This data record, using the NASA Team algorithm developed by scientists at NASA Goddard Space Flight Center, is the longest time series of sea ice extent data, extending back to 1979.

Other sea ice data are available from other data providers, using different satellite sensors and sea ice algorithms. For example, data from the University of Bremen indicate that sea ice extent from their algorithm fell below the 2007 minimum. They employ an algorithm that uses high resolution information from the JAXA AMSR-E sensor on the NASA Aqua satellite. This resolution allows small ice and open water features to be detected that are not observed by other products. This year the ice cover is more dispersed than 2007 with many of these small open water areas within the ice pack. While the University of Bremen and other data may show slightly different numbers, all of the data agree that Arctic sea ice is continuing its long-term decline.

For more information about the Arctic sea ice minimum, see the NSIDC Icelights article, Heading Towards the Summer Minimum Ice Extent.

*Near-real-time data initially recorded the 2007 record low as 4.13 million square kilometers 1.59 million square miles). The final data, reprocessed by NASA Goddard Space Flight Center using slightly different processing and quality control procedures, record the number as 4.17 million square kilometers (1.61 million square miles). NSIDC reports daily extent as a 5-day average. For more about the data, see the FAQ, Do your data undergo quality control?

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

Arctic sea ice near record lows

Arctic sea ice extent averaged for August 2011 reached the second lowest level for the month in the 1979 to 2011 satellite record. Both the Northwest Passage and the Northern Sea route appear to be open. Throughout August, sea ice extent tracked near the record lows of 2007, underscoring the continued decline in Arctic ice cover.

Note: Arctic sea ice extent will likely reach its minimum extent for the year sometime in the next two weeks. NSIDC will make a preliminary announcement when ice extent has stopped declining and has increased for several days in a row. Monthly data for September will be released in early October.

map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent for August 2011 was 5.52 million square kilometers (2.13 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
High-resolution image


Overview of conditions

Average ice extent for August 2011 was 5.52 million square kilometers (2.13 million square miles). This is 160,000 square kilometers (61,800 square miles) above the previous record low for the month, set in August 2007, and 2.15 million square kilometers (830,000 square miles), or 28% below the average for 1979 to 2000. Sea ice coverage remained below normal everywhere except the East Greenland Sea. In addition, several large areas of open water (polynyas) have opened within the ice pack.

On August 31, 2011 Arctic sea ice extent was 4.63 million square kilometers (1.79 million square miles). This is 100,000 square kilometers (38,600 square miles) higher than the previous record low for the same day of the year, set in 2007. As of September 5, ice extent had fallen below the minimum ice extents in September 2010 and 2008 (previously the third- and second-lowest minima in the satellite record). If ice stopped declining in extent today it would be the second-lowest minimum extent in the satellite record.

Higher-resolution Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) data processed by the University of Bremen showed ice extent on September 5 as falling below the same date in 2007.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily Arctic sea ice extent as of September 5, 2011, along with daily ice extents for previous low-ice-extent years. Light blue indicates 2011, dashed green shows 2007, dark blue shows 2010, purple shows 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
High-resolution image


Conditions in context

In August, sunlight wanes in the Arctic and the sea ice decline starts to slow down. Although the decline slowed somewhat during August, ice extent retreated at a faster pace than average, at a pace of 67,700 square kilometers (26,100 square miles) per day. In comparison, the average rate of decline for August 1979 to 2000 was 53,700 square kilometers (20,700 square miles) per day.

Air temperatures were 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) higher than average (relative to the 1981 to 2010 climatology) over the Arctic Ocean (measured approximately 1000 meters above the surface). The strongest anomalies were over the Northwest Passage region. High pressure persisted over much of the central Arctic Ocean, associated with a wind pattern that helped to push ice from the Beaufort Sea westward into the Chukchi Sea. This may have slowed some ice loss in the Chukchi Sea region. However, the wind pattern also transported ice into open waters warmed during the summer, fostering melt.

monthly average data graph Figure 3. Monthly August ice extent for 1979 to 2011 shows a decline of 9.3% per decade. —Credit: NSIDC
High-resolution image


August 2011 compared to previous years

Average Arctic sea ice extent for August 2011 was the second-lowest for August in the satellite data record. Including 2011 the linear trend for August now stands at –9.3% per decade.

figure 4 Figure 4. This time series shows total sea ice area (top) and multi-year ice area (bottom) for selected years within the Western Parry Channel route of the Northwest Passage. The black line with red dots shows 2011, and other colors show ice conditions in different years.—Credit: NSIDC courtesy Stephen Howell, Environment Canada, from Canadian Ice Service data
High-resolution image


Northwest Passage sea ice at record low levels

Sea ice is now almost completely gone from the channels of the Northwest Passage, with the exception of a small strip of ice across a stretch of the Parry Channel. The southern route (Amunden’s Route) is ice free. According to the Canadian Ice Service, sea ice extent in the western Parry Channel is now the lowest at this time of year since record keeping began in 1966 and very little multi-year ice remains. According to Multisensor Analyzed Sea Ice Extent (MASIE) data, ice cover across the Canadian Archipelago is at record low levels.

The Northern Sea Route along Siberia remains ice-free, with a number of cargo ships passing through in recent weeks. However, some areas of older, thicker ice have helped preserve the tongue of ice extending into the East Siberian Sea.

figure 5 Figure 5. This photograph from the NASA ICESCAPE mission in July shows melt ponds on the surface of the Arctic sea ice cover. Surface melt has now stopped as air temperatures have cooled. But relatively warm water will continue to melt the ice from below for another couple of weeks.—Credit: NASA/Kathryn Hansen
High-resolution image


Will Arctic sea ice extent reach a new record in 2011?

The melt season for Arctic sea ice will soon draw to a close. Surface melt has already largely ended and the ocean waters are cooling. Air temperatures at the North Pole have fallen below freezing. However, with the ice cover now thinner than in years past, there is a greater potential for late-season ice loss, caused by warm water melting ice from below or winds that push the ice together.

Whether Arctic sea ice breaks a new record hinges on three factors: First, how much heat is left in the ocean to eat away at the ice edge and bottom? Second, will wind patterns blow the ice together and reduce ice extent or will they disperse the ice and expand ice extent? Finally, just how thin is the remaining ice cover? Thin ice quickly melts away when it is surrounded by warm water.

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.