Spring has sprung in the Arctic

Arctic sea ice has passed its annual maximum extent and is beginning its seasonal decline through the spring and summer. While total extent was not at record low, it remained well below average through March. Ice fracturing continued north of Alaska, and the Arctic Oscillation was in a strongly negative phase during the second half of the month, with unusually high sea level pressure over almost all of the Arctic Ocean. Levels of multiyear ice remain extremely low. The ice is thinner, and satellite data suggests that first-year ice may now cover the North Pole area for the first time since winter 2008.

Overview of conditions

Figure 1. Arctic sea ice extent for March 2013 was 15.04 million square kilometers (5.81 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

Arctic sea ice extent in March 2013 averaged 15.04 million square kilometers (5.81 million square miles). This is 710,000 kilometers (274,000 square miles) below the 1979 to 2000 average extent, and 610,000 square kilometers (236,000 square miles) above the record low for the month, which happened in 2006. Continuing a trend in recent winters, ice extent was near or below average levels throughout most of the Arctic, with the exception of higher extent in the Bering Sea.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of April 1, 2013, along with daily ice extent data for the previous five years. 2012 to 2013 is shown in blue, 2011 to 2012 in green, 2010 to 2011 in pink, 2009 to 2010 in navy, and 2008 to 2009 in purple. The 1979 to 2000 average is in dark gray. The gray area around this 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

As Arctic sea ice reaches its maximum extent in March, the net gain or loss through the month tends to be small. This year, extent decreased 5,400 square kilometers (2,100 square miles) between the beginning and end of the month, with the decline in the second half of the month slightly outweighing the increase over the first half. Air temperatures (at the 925 mb level, or about 3,000 feet) were 3 to 6 degrees Celsius (5 to 11 degrees Fahrenheit) higher than average over the central Arctic Ocean, with cooler conditions compared to average (3 to 6 degrees Celsius, or 5 to 11 degrees Fahrenheit) over the Kara and Barents seas.

The circulation pattern known as the Arctic Oscillation (AO) reached an extreme negative phase in the second half of the month, associated with unusually high sea level pressure covering nearly the entire Arctic Ocean. The AO index , a measure of the state of the atmosphere over the Arctic, fell to as low as -5 sigma in mid March. This caps several months of a persistently negative AO. In the past, a negative AO in winter has been associated with the retention of thick ice in the Arctic Ocean and reduced export by drift into the Atlantic, favoring more extensive sea ice at the end of the summer melt season. However, in recent years, this relationship has not held and low summer extents have followed winters with strong negative AO. The month was also notable for continued fracturing of the ice cover in the Beaufort and Chukchi seas north of Alaska, as seen in a new animation by the NASA Earth Observatory . This is consistent with wind patterns associated with the strong negative pattern of the AO.

March 2013 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2013 shows a decline of 2.5% per decade.

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

Average ice extent for March 2013 was the fifth lowest for the month in the satellite record. Through 2013, the linear rate of decline for March ice extent is 2.5% per decade relative to the 1979 to 2000 average. While the percentage trend is lower than in the summer, the average rate of decrease is 39,800 square kilometers (15,300 square miles) per year, roughly the size of Maryland and Delaware combined.

A record extent of first-year ice in the Arctic

Figure 4. Imagery from the European Advanced Scatterometer (ASCAT) for December 2, 2012 (top) and March 28, 2013 (bottom) show the change in multiyear ice coverage over the winter season, as outlined by the colored lines. In winter, multiyear ice changes are due to the motion of the ice, either export through Fram Strait or redistribution within the Arctic Ocean.

Credit: Advanced Scatterometer imagery courtesy NOAA NESDIS, analysis courtesy T. Wohlleben, Canadian Ice Service
High-resolution image

Between the 2012 summer minimum and the 2013 winter maximum, sea ice extent increased 11.72 million square kilometers (4.53 million square miles), the largest increase in the satellite record. This was primarily due to the extreme record low ice extent in September 2012, which resulted in a near-record high first-year ice extent. This is evident in imagery from the Advanced Scatterometer (ASCAT) sensor on the European METOP-A satellite provided by National Oceanic and Atmospheric Administration’s National Environmental Satellite, Data, and Information Service (NOAA NESDIS). Analysis by Trudy Wohlleben at Environment Canada indicates that multiyear ice is relegated to areas far from the Alaskan and Eurasian coasts. Over the winter, some multiyear ice recirculated into the Beaufort Sea where significant melt of multiyear ice has occurred in recent summers. Also, some multiyear ice has been lost, as it moved out of the Arctic through Fram Strait. The boundary between primarily first-year ice and multiyear ice is now near the North Pole (indicated by the small black circle near the center of the image), marking the first time since the winter of 2008 that a substantial amount of first-year ice may be covering the pole as we enter the melt season.

Oldest ice continues to decline

Figure 5. The map at top shows the ages of ice in the Arctic at the end of March 2013; the bottom graph shows how the percentage of ice in each age group has changed from 1983 to 2013.

Credit: NSIDC courtesy J. Maslanik and M. Tschudi, University of Colorado
High-resolution image

While multiyear ice used to cover up to 60% of the Arctic Ocean, it now covers only 30%. There is a slight rebound in the oldest ice (4+ years old), a remnant of the large amount of first-year ice that formed during the winter after the 2007 record minimum. However, most of that new ice has not survived through the subsequent years. The oldest ice now comprises only 5% of the ice in the Arctic Ocean. This is a slight uptick from last winter’s record low of 3%, but still far less than during the 1980s when old ice covered roughly 25% of the region.

 Satellite estimates show continued thinning

Figure 6. Estimates of February/March average sea ice thickness for 2004 to 2008 from NASA’s ICESat (left) and February/March 2012 from CryoSat-2 (right). Colors indicate ice thickness in meters, with blue indicating 1-meter thick sea ice and red indicating 5-meter thick sea ice. The black and gray lines in the CryoSat-2 image are tracks of airborne data collected for validation. The triangle, circle, and square are locations of upward-looking sonar (ULS) moorings, also used for validation of the CryoSat-2 estimates.

Credit: American Geophysical Union
High-resolution image

The ASCAT data and ice age data both suggest a continued thinning of the ice pack, and overall decline in its volume, but they do not provide direct information on ice thickness. However, the European Space Agency’s CryoSat-2 satellite, launched in April 2010, now provides estimates of sea ice thickness distribution across the Arctic Ocean. A new paper by Laxon et al. (2013) shows the first published results from CryoSat-2 and compares them with thickness estimates from NASA’s ICESat satellite, which operated from 2003 to 2009. The CryoSat-2 results indicate continued thinning since 2008. Significantly, ice along the north coast of Greenland appears to have thinned—in the past this has been the site of some of the thickest sea ice in the Arctic. The paper also shows that total volume estimates from CryoSat-2 agree well with University of Washington’s Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS)  estimates.

In memoriam

We dedicate this post to Seymour Laxon, who tragically passed away in early January. Laxon was a driving force behind the CryoSat-2 mission, a leading innovator in the development of sea ice altimetry, an outstanding scientist, and a great friend to the sea ice community, including the contributors to Arctic Sea Ice & News Analysis.

Further reading

Laxon S. W. , K. A. Giles , A. L. Ridout , D. J. Wingham , R. Willatt , R. Cullen , R. Kwok , A. Schweiger , J. Zhang , C. Haas , S. Hendricks , R. Krishfield , N. Kurtz , S. Farrell, and M. Davidson. 2013. CryoSat-2 estimates of Arctic sea ice thickness and volume , Geophysical Research Letters 40, doi: 10.1002/grl.50193 .

A fractured winter

Arctic sea ice is nearing its winter maximum and will soon begin its seasonal decline. Ice extent remains below average, in part a result of the persistence of the negative phase of the Arctic Oscillation that has kept winter temperatures warmer than average. The Antarctic passed its summer minimum ice extent, reaching the second highest level in the satellite record at this time of year, primarily due to continued higher-than-average ice in the Weddell Sea.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2013 was 14.66 million square kilometers (5.66 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

Average sea ice extent for February 2013 was 14.66 million square kilometers (5.66 million square miles). This is 980,000 square kilometers (378,000 square miles) below the 1979 to 2000 average for the month, and is the seventh-lowest February extent in the satellite record. Since 2004, the February average extent has remained below 15 million square kilometers (5.79 million square miles) every year except 2008. Prior to 2004, February average extent had never been less than 15 million square kilometers. Ice extent remains slightly below average everywhere except the Bering Sea.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 3, 2013, along with daily ice extent data for the 2012, the record low year. 2013 is shown in blue, and 2012 in green. 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

Through the month of February, the Arctic gained 766,000 square kilometers of ice (296,000 square miles), which is 38% higher than the 1979 to 2000 average for the month. Air temperatures at the 925 hPa level were 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) higher than average across the Atlantic sector of the Arctic, especially near Iceland and in Baffin Bay. Temperatures were lower than average by 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) north of Greenland and the Canadian Archipelago, and in the Beaufort, Chukchi and East Siberian seas, linked to anomalously low sea level pressure over Alaska and Canada. The dominant feature of Arctic sea level pressure for February 2013 was unusually high pressure over the East Greenland and Barents seas, consistent with a predominantly negative phase of the Arctic Oscillation.

February 2013 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2012 shows a decline of -2.9% per decade.

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

Average Arctic sea ice extent for February 2013 was the seventh lowest for the month in the satellite record. Through 2013, the linear rate of decline for February ice extent is -2.9% per decade relative to the 1979 to 2000 average. Although the relative reduction in winter sea ice extent remains small compared to reductions in summer, the linear trend represents an overall reduction of more than 1.57 million square kilometers (606,000 square miles) from 1979 to 2013.

Persistence of the negative phase of the Arctic Oscillation

Figure 4. These ice motion images for November 2012 (left) and December 2012 (right) show strong export of ice through the Fram Strait in November, while in December ice export through the Fram was about average.

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

As discussed in the January and February posts, sea level pressure in the Arctic has remained higher than average, resulting in persistence of the negative phase of the Arctic Oscillation (AO). During the negative phase of the Arctic Oscillation, enhanced poleward transport of warm air tends to keep temperatures in the Arctic above average. At the same time, the negative phase of the Arctic Oscillation allows for more cold Arctic air to intrude or mix with air at lower latitudes. These cold air outbreaks can result in low temperatures and increased storminess in mid latitudes.

The Arctic Oscillation also impacts sea ice movement in the Arctic. The negative phase of the Arctic Oscillation is linked to an increase in the strength of the Beaufort Gyre and reduced outflow of ice through Fram Strait. A negative AO used to help promote ice survival through summer by strengthening the Beaufort Gyre and thereby increasing the distribution of old, thick ice along coastal Alaska and Siberia. However, the location and strength of positive sea level pressure anomalies has varied throughout winter, with varied impacts on ice motion.

For example, during November (weak AO index of -0.111) positive sea level pressure anomalies were centered over the Bering Sea and Alaska, resulting in strong ice motion from the central Arctic towards coastal Canada and north of Greenland outwards towards Fram Strait. In December, the strong negative AO index of -1.749 was reflected in positive sea level pressure anomalies centered over the Kara and Barents seas, enhancing ice motion from the southern Beaufort into the Chukchi sea and out towards the Bering Sea. Export of ice out of Fram Strait was about average. Similar variations in positive sea level pressure anomalies have continued, with the largest positive anomalies over the central Arctic in January, and over the Barents Sea in February.

This pattern is similar to that observed during the extreme negative Arctic Oscillation year of 2009/2010, when old ice was transported into the southern Beaufort and Chukchi seas where it then melted out during summer 2010, further depleting the Arctic of its store of old, thick ice.

Ice fracture

Figure 5. In this series of images from February 13 to March 2, from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS), a large crack expands in the sea ice near the coasts of Canada and Alaska. Black areas indicate where the satellite instrument did not collect data due to lack of sunlight. The dark area decreases as the sun rises in the Arctic. Rapid Response imagery was obtained from the NASA Land Atmosphere Near-real time Capability for EOS (LANCE) system.

Credit: NASA LANCE/National Snow and Ice Data Center
View the image series

During the last couple of weeks of February, a broad area of sea ice has fractured off the coast of Alaska and Canada, extending from Ellesmere Island in the Canadian Arctic to Barrow, Alaska. This fracturing event appears to be related to a series of storms that moved across central Alaska starting on February 10, 2013, causing intense easterly winds along the coast and strong off-shore ice motion.* The large area of fractured ice is located in predominantly first-year ice, which is thinner and easier to fracture than thick, multiyear ice. Similar patterns were observed in early 2011 and 2008, but the 2013 fracturing is quite extensive.  The animation (Figure 5) shows the progress of the fracturing, and the general strong rotation of the Beaufort Gyre ice motion pattern during late February. (See also this animation of the fracture from the AVHRR instrument, posted on the Arctic Sea Ice Blog.)

* Note: We originally attributed the fracturing event to a storm that passed over the North Pole, and stated “This fracturing event appears to be related to a storm that passed over the North Pole on February 8, 2013, creating strong off-shore ice motion.” We corrected this sentence after reexamining weather charts. The updated version now reads, “This fracturing event appears to be related to a series of storms that moved across central Alaska starting on February 10, 2013, causing intense easterly winds along the coast and strong off-shore ice motion.”

Antarctic sea ice extent continues above average

Figure 6. Antarctic sea ice extent for February 2013 was 3.83 million square kilometers (1.48 million square miles). The magenta line shows the 1979 to 2000 median extent for that month. The black cross indicates the geographic South Pole. Sea Ice Index data. About the data

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

The Antarctic sea ice minimum extent appears to have passed, on February 20. Ice was quite extensive throughout the austral summer period. Monthly average sea ice extent for February 2013 was 3.83 million square kilometers (1.48 million square miles) and minimum daily sea ice extent for the Antarctic region was 3.68 million square kilometers (1.42 million square miles) on February 20. Unusual circulation patterns, likely resulting from higher-than-average pressure in the Bellingshausen Sea, pushed sea ice in the northwestern Weddell Sea far to the north, as we mentioned in our February post. NASA’s Earth Observatory posted this image of ice in the Weddell Sea as Image of the Day for March 1st, 2013. Extent was also well above average for the Ross Sea region relative to the entire 1979 to 2013 satellite record.

The Odden

Figure 7. This image shows sea ice cover in early May, 2012 in the east Greenland Sea. Sea ice extent is provided at 4 kilometer resolution by the NSIDC/NIC multi-sensor MASIE product and sea ice concentration (varying from 0 to 1) at 25 kilometer resolution by NSIDC’s Near-Real Time Passive Microwave product. The red dot shows the estimated position of an ARGO profiling float deployed as part of a NASA-sponsored project led by Michael Steele  and Patricia Matrai. This float is capable of storing ocean data while under the ice pack, which are then received via satellite when the ice recedes. Ongoing analysis of these data indicates that cold, fresh surface water lies just under the ice extension along the Jan Mayen Ridge, a signature of Arctic waters.

Credit: M. Steele, University of Washington and P. Matrai, Bigelow Lab/National Snow and Ice Data Center
High-resolution image

Within the East Greenland Sea, an ice tongue about 1,300 kilometers (807 miles) in length, referred to as “The Odden” (Norwegian word for headland), would regularly form during winter months eastwards from the main East Greenland ice edge. The Odden would form in winter because of an eastward flow of very cold ocean waters in the Jan Mayen current and may have played an important role in winter ocean convection as new ice would form. It would form as early as December and as late as April and was present during the 1980s, a few times in the 1990s, and very rarely since 2000. While the Odden rarely formed in last two decades, there is frequently a small extension of ice along the Jan Mayen Ridge, which may indicate that eastward flow of cold ocean water is still occurring.

Arctic sea ice falls below 4 million square kilometers

Following the new record low recorded on August 26, Arctic sea ice extent continued to drop and is now below 4.00 million square kilometers (1.54 million square miles). Compared to September conditions in the 1980s and 1990s, this represents a 45% reduction in the area of the Arctic covered by sea ice. At least one more week likely remains in the melt season.

Overview of conditions

Figure 1. Arctic sea ice extent for August 2012 was 4.72 million square kilometers (1.82 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

Throughout the month of August, Arctic sea ice extent tracked below levels observed in 2007, leading to a new record low for the month of 4.72 million square kilometers (1.82 million square miles), as assessed over the period of satellite observations,1979 to present. Extent was unusually low for all sectors of the Arctic, except the East Greenland Sea where the ice edge remained near its normal position. On August 26, the 5-day running average for ice extent dropped below the previous record low daily extent, observed on September 18, 2007, of 4.17 million square kilometers (1.61 million square miles). By the end of the month, daily extent had dropped below 4.00 million square kilometers (1.54 million square miles). Typically, the melt season ends around the second week in September. 

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 3, 2012, along with daily ice extent data for the previous five years. 2012 is shown in blue, 2011 in orange, 2010 in pink, 2009 in navy, 2008 in purple, and 2007 in green. The 1979 to 2000 average is in dark gray. The gray area around this 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

In 2012, the rate of ice loss for August was 91,700 square kilometers (35,400 square miles) per day, the fastest observed for the month of August over the period of satellite observations. In August 2007, ice was lost at a rate of 66,000 square kilometers (25,400 square miles) per day, and in 2008, the year with the previous highest August ice loss, the rate was 80,600 square kilometers (31,100 square miles) per day. The average ice loss for August is 55,100 square kilometers (21,300 square miles) per day. This rapid pace of ice loss in 2012 was dominated by large losses in the East Siberian and the Chukchi seas, likely caused in part by the strong cyclone that entered the region earlier in the month and helped to break up the ice. However, even after the cyclone had dissipated, ice loss continued at a rate of 77,800 square kilometers (30,000 square miles) per day.

August air temperatures at the 925 hPa level (approximately 3,000 feet above the surface) remained slightly above average (1 to 3 degrees Celsius, or 2 to 5 degrees Fahrenheit) over the much of the Pacific sector of the Arctic Ocean as well as at its central sector, with slightly higher temperatures in the Beaufort Sea (approximately 4 degrees Celsius, or 7 degrees Fahrenheit above average). On the Atlantic side, the Kara and Barents seas continued to have air temperatures around 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) below average.

At the end of August, ice remained in the Western Parry Channel, and neither the northern or southern routes of the Northwest Passage were open. While much of the ice has cleared out, ice still remains, as confirmed by our colleague Steve Howell at the Canadian Ice Service. In the latter half of August, more ice actually moved into the passage routes when ice was pushed down into the channels from the north. Whether that ice will clear out remains to be seen.

August 2012 compared to previous years

Figure 3. Monthly August ice extent for 1979 to 2012 shows a decline of 10.2% per decade.


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

The monthly averaged ice extent for August was 4.72 million square kilometers (1.82 square miles). This is 2.94 million square kilometers (1.14 million square miles) below the 1979 to 2000 average extent, and 640,000 square kilometers (247,000 square miles) below the previous record low for August set in 2007. Including 2012, the August trend is -78,100 square kilometers (-30,200 square miles) per year, or -10.2 % per decade relative to the 1979 to 2000 average.

Evolution of sea surface temperatures in August

sea surface temperature images

Figure 4. A buoy deployed on August 8, 2012 in open water during the storm initially shows a very warm 10-meter (33-foot) thick surface mixed layer (upper left image). On August 12 (upper right image), the buoy enters a relatively cooler patch, gradually warms, enters another cool patch 12 days later (bottom left image), and then starts to warm again through August 26 (bottom right image). Red, orange, and yellow indicate higher temperatures, while blues and purples indicate lower temperatures.

Credit: University of Washington Polar Science Center
High-resolution image

In recent summers, Arctic Ocean sea surface temperatures (SSTs) have been anomalously high (see our 2010 and 2011 end-of-summer posts), in part linked to loss of the reflective ice cover that allows darker open water areas to readily absorb solar radiation and warm the mixed layer of the ocean. According to Mike Steele, Wendy Ermold and Ignatius Rigor of the University of Washington, SSTs in the Beaufort, Chukchi, and Laptev seas were once again anomalously high before the strong cyclone (mentioned earlier and discussed in our previous post) entered the East Siberian and Chukchi seas on August 5, 2012. SSTs were as much as 5 degrees Celsius (9 degrees Fahrenheit) above normal along the coastal areas in those seas. After the storm, the warm water that developed through summer was interspersed with large areas of cold water created by ice melt. By the third week of August, sea surface temperatures were mostly back to levels observed before the storm, but with a few more patches of colder water interspersed from additional ice melt.

A closer view of the variation in SSTs before and after the storm is recorded in the University of Washington Polar Science Center UpTempO buoy data. A buoy deployed on August 8, 2012 in open water during the storm initially shows a very warm 10-meter (33-foot) thick surface mixed layer, likely the result of solar heating. On August 12, the buoy enters a relatively cooler patch, gradually warms, enters another cool patch 12 days later and then starts to warm again through August 26. These patches of cooler water may be a result of ice melt and/or the impact of advection from the storm.

Old ice continues to decline

Figure 5. These images from March 2012 (left) and August 2012 (right) show the age of the ice cover in spring and at the end of summer. Much of the Arctic ice cover now consists of first-year ice (shown in purple), which tends to melt rapidly in summer’s warmth. However, the oldest ice, that had survived five or more summers (shown in white), declined by 51%.

Credit: M. Tschudi and J. Maslanik, University of Colorado Boulder
High-resolution image

Ice age is an important indicator of the health of the ice cover. Old ice, also called multiyear ice, tends to be thicker ice and less prone to melting out in summer. The last few summers have seen increased losses of multiyear ice in the Pacific sector of the Arctic; multiyear ice that is transported into the Beaufort and Chukchi seas tends to melt out in summer before being transported back to the central Arctic Ocean through the clockwise Beaufort Gyre circulation. This summer, the tongue of multiyear ice along the Alaska coast mostly melted out by the end of August, with a small remnant left in the Chukchi Sea. The ice on the Pacific side of the Arctic has melted back to the edge of the multiyear ice cover, which should help to slow further ice loss in the region. In the Laptev Sea, by contrast, a large amount of first-year ice remains. In the last two weeks, open water areas have developed within the first-year ice in the Laptev Sea, helping to further foster melt in that region.

Between mid-March and the third week of August, the total amount of multiyear ice within the Arctic Ocean declined by 33%, and the oldest ice, ice older than five years, declined by 51%.

Further reading

Kwok, R., and G. F. Cunningham. 2010. Contribution of melt in the Beaufort Sea to the decline in Arctic multiyear sea ice coverage: 1993–2009. Geophys. Res. Lett., 37, L20501, doi:10.1029/2010GL044678.

Maslanik, J.A., C. Fowler, J. Stroeve, and W. Emery. 2011. Distribution and trends in Arctic sea ice age through spring 2011. Geophys. Res. Lett., 38, L13502, doi:10.1029/2011GL047735.

Arctic ice extent low overall, high in the Bering Sea

Overall, Arctic sea ice extent remained lower than average in January. However, in the Bering Sea, ice extent was much greater than normal. The heavy ice cover caused problems for fishermen and made for an arduous late-season resupply mission to Nome, Alaska. The Arctic Oscillation, which had been in its positive phase most of the winter so far, switched to a negative mode, bringing cold weather to Europe and changing the direction of sea ice movement.

Figure 1. Arctic sea ice extent for January 2012 was 13.73 million square kilometers (5.30 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.

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

Overview of conditions
Arctic sea ice extent in January 2012 averaged 13.73 million square kilometers (5.30 million square miles). This is the fourth-lowest January ice extent in the 1979 to 2012 satellite data record, 1.10 million square kilometers (425,000 square miles) below the 1979 to 2000 average extent.

As in December, ice extent was lower than normal on the Atlantic side of the Arctic, especially in the Barents Sea. However, on the other side of the Arctic, ice extent in the Bering Sea was much greater than average, reaching the second-highest levels for January in the satellite record. The greater-than-normal ice extent in the Bering Sea partly compensated for low ice extent on the Atlantic side of the Arctic Ocean, but ice extent as a whole remained far below average.

Figure 2. The graph above shows daily Arctic sea ice extent as of February 5, 2012, along with the ice extents for the previous four years. 2011 is shown in light blue, 2010 is in pink, 2009 in dark blue, 2008 is in purple, and 2007, the year with the record low minimum, is dashed green. 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 growth rate for Arctic sea ice in January was the slowest in the satellite record. After growing relatively quickly early in January, ice extent declined briefly in the middle of the month, and then grew more slowly than normal for the rest of the month. The slow growth likely stemmed from winds from the south and west that compressed the sea ice in the Barents Sea, and above-average temperatures and winds that limited ice growth in the Sea of Okhotsk.

Overall, the Arctic gained 765,000 square kilometers (295,000 square miles) of ice during the month. This was 545,000 square kilometers (210,000 square miles) less than the average ice growth rate for January 1979 to 2000.

Figure 3. Monthly January ice extent for 1979 to 2012 shows a decline of 3.2% per decade.

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


January 2012 compared to past years

Arctic sea ice extent for January 2012 was the fourth lowest in the satellite record. Including the year 2012, the linear rate of decline for January ice extent over the satellite record is 3.2% per decade.
Based on the satellite record, before 2005 average January ice extent had never been lower than 14 million square kilometers (5.41 million square miles). January ice extent has now fallen below that mark six out of the last seven years.

Figure 4. Monthly average sea ice motion for December 2011 (top) and January 2012 (bottom), derived from the DMSP Special Sensor Microwave Imager and Sounder (SSMIS) shows how the changing Arctic Oscillation (AO) phase affects the movement of ice. In January, the AO switched from a positive phase to a negative phase.

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


The Arctic Oscillation turns negative

From November through the first part of January, the Arctic Oscillation (AO) was in a generally positive phase, which tends to bring warm conditions to the United States and Europe, and colder conditions to the Arctic. However, in the middle of the month, the AO shifted back to a negative phase. This shift helped bring cold air outbreaks over middle latitudes, notably a record cold snap throughout much of Europe.

The Arctic Oscillation also affects how sea ice moves in the Arctic, which can affect how much ice melts in the summer months. In December, when the AO was in its positive phase, ice was flowing from Siberia toward North America, and also south out of the Arctic through Fram Strait. That pattern favors a thinner, younger ice cover in the summer. In mid-January, the AO switched to its negative phase. In general, the negative phase of the AO tends to retain ice in the Arctic Ocean, leading to a stronger, more resilient summer sea ice cover. Ice motion charts for January confirm that in January, there was less motion across the pole and through Fram Strait but a stronger clockwise motion in the Beaufort Sea called the Beaufort Gyre.

For background on the Arctic Oscillation, see the NSIDC Icelights post: The Arctic Oscillation, winter storms and sea ice.

Figure 5. This NASA Moderate Resolution Imaging Spectroradiometer (MODIS) image, acquired in mid-January, shows heavy sea ice conditions in Bristol Bay and the Bering Sea, off the western coast of Alaska.

Credit: NASA Earth Observatory courtesy Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team at NASA GSFC.
High-resolution image

Ice-covered Bering Sea
Arctic sea ice extent in the Bering Sea was the second highest in the satellite record for the month of January. Ice extent in the Bering Sea was 562,000 square kilometers (217,000 square miles), which is 104,600 square kilometers (40,400 square miles) above the 1979 to 2000 average. The record high ice extent for the month occurred in January 2000, at 629,000 square kilometers (242,900 square miles).

The above-average sea ice extent in the Bering Sea stemmed from a weather pattern that brought cold air from the Arctic into the Bering Sea, driving sea ice southwards. The weather pattern, which has persisted since November, features unusually low surface pressure south and east of the Alaskan coast, which leads to winds from the north or northeast that blow into the Bering Sea region. This weather pattern also brought moist air from the Pacific Ocean to the southern Alaska coast, helping to explain record snowfalls in towns such as Cordova, Alaska, which received over 15 feet of snow between early November and mid-January.

The extensive sea ice impeded winter fishing in the Bering Sea and slowed an important fuel resupply mission to Nome, on the west coast of Alaska. More information on sea ice conditions off southwestern Alaska, and a full-resolution version of the image at left, are available on the NASA Earth Observatory Web site.