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Arctic sea ice at minimum extent

Daily image update extent map time series

Sea ice data updated daily, with one-day lag. Orange line in extent image (left) and gray line in time series (right) indicate 1979 to 2000 average extent for the day shown. Click for high-resolution image.
Learn about update delays and other problems which occasionally occur in near-real-time data. Read about the data.   -Credit: National Snow and Ice Data Center

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 flows 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, continents
Figure 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.

NASA logoNSIDC scientists provide Arctic Sea Ice News & Analysis, with partial support from NASA.

RELATED STORY
September 13, 2011 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?

NASA logoNSIDC scientists provide Arctic Sea Ice News & Analysis, with partial support from NASA.


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