Daily Image Update

Read scientific analysis on Arctic sea ice conditions. We provide an update during the first week of each month, or more frequently as conditions warrant.

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Sea ice data updated daily, with one-day lag. Orange line in extent image (left) and gray line in time series (right) indicate 1981 to 2010 average extent for the day shown. The graph also includes lines for selected earlier years, for comparison. Learn about update delays and other problems which occasionally occur in near-real-time data. Read about the data.

ABOUT THESE IMAGES

extent map time series

Click for high-resolution image. —Credit: National Snow and Ice Data Center

Arctic sea ice reaches near-average extent in April

Arctic sea ice extent declined slowly through the first three weeks of April, compared to recent years. The slow decline through March and the first few weeks of April meant that by mid-April, ice extent was at near-average levels. However, much of the extensive ice cover is thin ice that will melt quickly once temperatures rise in the Arctic. Over the past week, extent has started to fall sharply.

Figure 1. Arctic sea ice extent for April 2012 was 14.73 million square kilometers (5.69 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
Arctic sea ice extent in April 2012 averaged 14.73 million square kilometers (5.69 million square miles). Because of the very slow rate of ice loss through the last half of March and the first three weeks of April, ice extent averaged for April ranked close to average out of 34 years of satellite data.  It was the highest average ice extent for the month since 2001, only 270,000 square kilometers (104,000 square miles) below the 1979 to 2000 average extent. April ice extent was 860,000 square kilometers (330,000 square miles) above the record low for the month, which happened in 2007.

In April, ice cover remained unusually extensive in the Bering Sea, continuing a pattern that persisted over the winter.  Ice extent was also slightly higher than average in Baffin Bay and part of the Sea of Okhotsk.  As in recent winters, ice extent was well below normal in the Barents Sea, compensating for the extensive ice in the Bering Sea.

As discussed in previous posts, the high Bering Sea ice extent this winter stemmed from unusually low air temperatures and persistent winds that helped to push ice southwards. During April, atmospheric conditions changed, warming the air to near-average temperatures for this time of year and slowing the strong southerly winds.

During April, air temperatures over most of the Arctic were higher than usual, particularly over the central Arctic Ocean.  Over the Bering Sea and parts of the East Greenland and Norwegian seas, temperatures ranged from average to slightly below average.

Figure 2. The graph above shows Arctic sea ice extent as of May 1, 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 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
Note: That image originally published on May 3 contained an error in the climatology. The image has been replaced with the correct image. About the data

Conditions in context
Overall, the Arctic lost 1.07 million square kilometers (413,000 square miles) of ice during April, somewhat less than the 1979 to 2000 average April loss of 1.21 million square kilometers (467,000 square miles). The average daily rate of ice loss was 35,600 square kilometers (13,700 square miles) per day.  On April 24, ice extent was only 118,000 square kilometers (45,6000 square miles) below the 1979 to 2000 average for that day, although the difference has increased since then.

While ice conditions approached the 1979 to 2000 average levels for this time of year, the high ice extent will have little influence on how much ice melts this summer. Much of the ice cover is recently formed thin ice that will melt out quickly. Research has shown that sea ice extent in spring does not tell us much about ice extent the following summer. More important to the summer melt is the thickness of the ice cover, and summer weather.

Figure 3. Monthly April ice extent for 1979 to 2012 shows a decline of 2.6% per decade.

Credit: National Snow and Ice Data Center
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April 2012 compared to past years
Arctic sea ice extent for April 2012 was near average for the month in the satellite record, but was the highest since 2001. Including the year 2012, the linear rate of decline for April ice extent over the satellite record is 2.6% per decade.

Figure 4. This graph shows Antarctic sea ice extent as of May 1, 2012 (light blue line), along with the average ice extent and the ice extent from last year (dark blue). The average Southern Annular Mode (SAM) index number for each month is overlaid on the image. A stronger SAM correlates to stronger winds, which help to spread the sea ice and increase ice extent.

Credit: National Snow and Ice Data Center
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Antarctic sea ice spread by strong winds

The sea ice cover that surrounds the continent of Antarctica has been higher than average through most of the Southern Hemisphere summer (December to March). Ice extent declined much more slowly than usual in late November and remained above average through December and January, although it did not reach record highs for those months. At its minimum extent in March, Antarctic sea ice remained above average. Ice extent was the highest in the Weddell Sea and the northwestern Ross Sea.

The high ice extent likely stemmed from unusually strong winds that circled the continent of Antarctica during most the southern summer. These circumpolar winds tend to push the ice out from the continent, increasing the extent of the ice, although not necessarily the volume. Air temperatures in December and January were close to average over most of the sea ice-covered water. Researchers approximate the circumpolar wind intensity by an index called the Southern Annular Mode (SAM). A positive value for SAM indicates strong circumpolar winds around the continent; negative values indicate weaker winds. This index was at a record high for the two months of December 2011 and January 2012, at the same period of the higher-than-normal seasonal extents. For more information on Antarctic sea ice, see the NSIDC Icelights article: Sea ice down under: Antarctic sea ice and climate.

Figure 5. This map shows Arctic sea ice thickness, as well as the elevation of the Greenland Ice Sheet, for March 2011. The data come from the European Space Agency CryoSat-2 satellite. For the sea ice, green shades indicate thinner ice, while the yellows and oranges indicate thicker ice.

Credit: NSIDC courtesy CPOM/UCL/Leeds/ESA/PVL
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Cryosat provides new ice thickness data

NSIDC data provide a long-term record of the Arctic and Antarctic sea ice cover. But researchers also want to know how thick the ice cover is, since thinner ice melts faster than thicker ice. Ice thickness measurements are more limited than ice extent, because researchers can only sample small regions in person, and there have only been a few satellite sensors that can measure ice thickness. For example, the NASA ICESat satellite recorded Arctic sea ice thickness between 2003 and 2008, but the mission ended in 2009, and the follow-on mission is not expected to begin until 2016. In the meantime, NASA is filling some of the data gap with airplane-borne instruments as part of Operation IceBridge.

The European Space Agency (ESA) has released initial data from the radar altimeter on their CryoSat-2 satellite. Last week, ESA released the first calibrated maps of Arctic sea ice thickness capturing thickness changes through the winter from October 2010 through March 2011. In the coming years, CryoSat-2 will provide monthly fields of thickness that will allow scientists to track the evolution of the ice cover. For more information on CryoSat-2 and an animation of the thickness maps, see: http://www.esa.int/SPECIALS/Cryosat/SEMU55NW91H_0.html.

Further Reading

Kwok, R., G. F. Cunningham, M. Wensnahan, I. Rigor, H. J. Zwally, and D. Yi. 2009. Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008, J. Geophys. Res., 114, C07005, doi:10.1029/2009JC005312.

Kwok, R., G. F. Cunningham, S. S. Manizade, and W. B. Krabill. 2012. Arctic sea ice freeboard from IceBridge acquisitions in 2009: Estimates and comparisons with ICESat, J. Geophys. Res., 117, C02018, doi:10.1029/2011JC007654.

Kwok, R., and G. F. Cunningham. 2008. ICESat over Arctic sea ice: Estimation of snow depth and ice thickness, J. Geophys. Res., 113, C08010, doi:10.1029/2008JC004753.

Laxon, S., N. Peacock, and D. Smith. 2003. High interannual variability of sea ice thickness in the Arctic region, Nature, 424, 947-950, October, doi:10.1038/nature02063.

Arctic sea ice enters the spring melt season

Arctic sea ice reached its annual maximum extent on March 18, after reaching an initial peak early in the month and declining briefly. Ice extent for the month as a whole was higher than in recent years, but still below average.

As the melt season begins, researchers look at a variety of factors that may contribute to summer ice melt. While the maximum extent occurred slightly later than average, the new ice growth is very thin and likely to melt quickly. Ice age data indicate that despite the higher extent compared to recent years, the winter sea ice continues to be dominated by younger and thinner sea ice.

Figure 1. Arctic sea ice extent for March 2012 was 15. 21 million square kilometers (5.87 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
Arctic sea ice extent in March 2012 averaged 15.21 million square kilometers (5.87 million square miles). Ice extent this March ranked ninth lowest out of the 34 years of satellite data for the month, but it was the highest March average ice extent since 2008 and one of the higher March extents in the past decade. Ice extent was 530,000 kilometers (205,000 square miles) below the 1979 to 2000 average extent, and 780,000 square kilometers (301,000 square miles) above the record low for the month, which happened in 2006.

Ice cover remained extensive in the Bering Sea, where it has been above average all winter. Ice extent was also higher than average in Baffin Bay, between Greenland and Canada, and the Sea of Okhotsk, east of Russia. These conditions stemmed from a combination of wind patterns and low temperatures. Air temperatures were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) below average over the Bering Sea, Baffin Bay, and parts of the Sea of Okhotsk, at the 925 millibar level (about 3,000 feet above sea level). View a map of Arctic regions.

In the Kara Sea, where ice extent had been below average during January and February, ice extent rebounded to near-average levels in March. Winds that had been pushing the ice cover back shifted, allowing areas of open water in the Kara Sea to freeze over and the ice to spread out. Ice extent in the Barents Sea remained well below normal. In both the Barents and Kara seas, temperatures remained above normal by 4 to 6 degrees Celsius (7 to 11 degrees Fahrenheit).

Figure 2. The graph above shows daily Arctic sea ice extent as of April 2, 2012, along with the ice extents for the previous four years. The current year is shown in light blue, 2010-11 is in pink, 2009-10 in dark blue, 2008-09 is in purple, and 2006-2007, 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
Overall, the Arctic gained 140,000 square kilometers (54,000 square miles) of ice during March. Typically, March has been a month of net ice loss (an average of 260,000 square kilometers [100,000 square miles] for 1979 to 2000), but the last three Marches have had net ice growth. At its maximum extent on March 18, Arctic sea ice extent was within two standard deviations of the average, a measure that scientists look at as an estimate of the natural range of variability for the data.

Over the past thirty years of satellite data, the day of the maximum has varied by over six weeks, occurring as early as mid-February and as late as the end of March. However, even with so much variability, there is a small trend towards later maximum ice extents. This year’s maximum ice extent continued that trend, occurring 12 days later than average.

It is not clear why the maximum ice extent would happen later, given that in general, ice extent is decreasing. One possibility is that the lower winter ice extents might make it easier for ice to continue growing later in the season. With lower winter extents, a late cold snap or northerly wind could spread ice southward over ocean that would normally be ice-covered at that point. Researchers do not expect the late maximum ice extent to strongly influence summer melt. The ice that grew late this winter is quite thin, and will melt rapidly as the sun rises higher in the sky and the air and water get warmer.

Figure 3. Monthly March ice extent for 1979 to 2012 shows a decline of 2.6% per decade.

Credit: National Snow and Ice Data Center
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March 2012 compared to past years
Arctic sea ice extent for March 2012 was the 9th lowest in the satellite record, but the highest since 2008 and one of the highest March extents in the past decade. Including the year 2012, the linear rate of decline for March ice extent over the satellite record is 2.6% per decade.

Figure 4. This image, from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS), shows extensive sea ice cover in the Bering Sea on March 18, 2012. For more details and a full-resolution image, visit the NASA Earth Observatory Web site.
Credit:NASA image by Rob Simmon based on data from Jeff Schmaltz, NASA GSFC.
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High ice extent in the Bering Sea
In the Bering Sea, off Alaska, ice extent reached a record high for the month of March. Persistent winds pushed the sea ice southward and froze more seawater into ice.

As winds from the north pushed Arctic ice southward through the Bering Strait, the ice locked together and formed a structurally continuous band known as an ice arch, which acts a bit like a keystone arch in a building. The ice arch temporarily held back the ice behind it, but as the winds continued, the arch failed along its southern edge, and ice cascaded south through the strait into the Bering Sea. Sea ice also piled up on the northern coast of St. Lawrence Island, streaming southward on either side of it.

Figure 5. Ice age data show that first-year ice made up 75% of the Arctic sea ice cover this March. Thicker multiyear ice used to make up around a quarter of the Arctic sea ice cover. Now it constitutes only 2%.

Credit: NSIDC courtesy J. Maslanik and M. Tschudi, University of Colorado
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Ice age data shows thin ice cover
One key predictor for summer ice melt is the amount of old, thick ice in the Arctic at the end of the winter. Some ice thickness data are available from satellites, but these records are short and discontinuous. Data from the NASA ICESat satellite covers only 2003 to 2009, and the new European Space Agency CryoSat satellite began collecting data in 2011. So researchers look at ice age data as one indicator of Arctic sea ice thickness. Older ice that has survived multiple melt seasons tends to be thicker than newly formed ice.

Ice age data this year show that the ice cover remains much thinner than it was in the past, with a high proportion of first-year ice, which is thin and vulnerable to summer melt. After the record low minimum of 2007 the Arctic lost a significant amount of older, thicker ice, both from melting and from movement of ice out of the Arctic the following winter. In the last few years, the melt and export of old ice was less extreme than in 2007 and 2008, and multiyear ice started to regrow, with second and third-year ice increasing over the last three years.

After the near-record melt last summer, second-year ice declined again, but some of the ice that had survived the previous few summers made it through another year, increasing the proportion of third- and fourth-year ice. However the oldest, thickest ice, more than four years old, continued to decline. Ice older than four years used to make up about a quarter of the winter sea ice cover, but now constitutes only 2%. First-year ice (0 to 1 years old) this year makes up 75% of the total ice cover, the third highest at this time of year in the satellite record. In 2008 the proportion of first-year ice was 79%, and in 2009 it was 76%.

Figure 6. The top image shows a decline in upper-atmosphere winds (solid line) over the last 30 years that mirrors the decline in sea ice over the same time period (dashed line). The bottom image shows the expected change in trajectory of the jet stream (dotted line) compared to the current jet stream trajectory (solid line).

Credit: Jennifer Francis, Rutgers University
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Rapid Arctic warming and mid-latitude weather
The Arctic has warmed about twice as fast as the rest of the Northern Hemisphere in recent decades. Summer Arctic sea ice has declined by 40%, and snow is melting earlier in spring on the surrounding land. This dramatic change in the climate system is expected to affect weather patterns well beyond the confines of the Arctic—but researchers are working to understand exactly how those changes are affecting other regions.

New research by Jennifer Francis of Rutgers University and Steve Vavrus of the University of Wisconsin suggests that warming in the Arctic is causing weather patterns in mid-latitudes to become more persistent. This persistence can lead to conditions like heat waves, cold spells, drought, flooding, and heavy snows. The researchers found that as temperatures in the Arctic warm and become closer to temperatures in lower latitudes, the waves of the jet stream tend to spread out, and west-to-east winds slow down in the upper level of the atmosphere (where storm tracks form). Both of these effects tend to slow the progression of weather patterns, which means that a weather pattern, whether hot or cold, is more likely to stick around.

References

Francis, J.A. and S.J. Vavrus. 2012. Evidence linking Arctic amplification to extreme weather in mid-latitudes. Geophysical Research Letters, 39, L06801, doi:10.1029/2012GL051000.

Francis, J.A. 2012. Linking weird weather to rapid warming of the Arctic. Yale Environment 360, http://e360.yale.edu/feature/linking_weird_weather_to_rapid_warming_of_the_arctic/2501/

Kwok, R., T. Pederson, P. Gudmandsen, S. Pang. 2010. Large sea ice outflow in the Nares Strait in 2007. Geophysical Research Letters, 37, L03502, doi:10.1029/2009GL041872.

Sodhi, D. S. 1977. Ice arching and the drift of pack ice through restricted channels, Rep. 77‐18, Cold Reg. Res. and Eng. Lab., Hanover, N. H.

Arctic sea ice maximum marks beginning of melt season

On March 18, 2012, Arctic sea ice extent reached its annual maximum extent, marking the beginning of the melt season for Northern Hemisphere sea ice. This year’s maximum extent was the ninth lowest in the satellite record.

Figure 1. Arctic sea ice extent on March 18 was 15.24 million square kilometers (5.88 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. About the data.

Credit: National Snow and Ice Data Center
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Overview of conditions

On March 18, 2012 Arctic sea ice likely reached its maximum extent for the year, at 15.24 million square kilometers (5.88 million square miles). The maximum extent was 614,000 square kilometers (237,000 square miles) below the 1979 to 2000 average of 15.86 million square kilometers (6.12 million square miles). The maximum occurred this year 12 days later than the 1979 to 2000 average date of March 6.

This year’s maximum ice extent was the ninth lowest in the satellite record, slightly higher than the 2008 maximum (15.24 million square kilometers or 5.88 million square miles) Last year, 2011, was the lowest maximum on record, 14.64 million square kilometers (5.65 million square miles). Including this year, the nine years from 2004 to 2012 are the nine lowest maximums in the satellite record.

The graph above shows daily Arctic sea ice extent as of March 25, 2012, along with the ice extents for the previous four years. 2011-12 is shown in light blue, 2010-11 is in pink, 2009-10 in dark blue, 2008-09 is in purple, and 2006-2007, 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
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Conditions in context
As of March 23, ice extent has declined for five days. However, there is still a chance that the ice extent could expand again. Sea ice extent in February and March tends to be quite variable, because ice near the edge is thin and often quite dispersed. The thin ice is highly sensitive to weather, moving or melting quickly in response to changing winds and temperatures, and it often oscillates near the maximum extent for several days or weeks, as it has done this year.

Arctic sea ice extent is declining in winter as well as in summer months, although the decline is not as steep in the winter months. At the beginning of April, NSIDC scientists will release a full analysis of winter conditions, along with monthly data for March. For more information about the maximum extent and what it means, see the NSIDC Icelights post, the Arctic sea ice maximum.

February ice extent low in the Barents Sea, high in the Bering Sea

As in January, sea ice extent in February was low on the Atlantic side of the Arctic, but unusually high on the Pacific side of the Arctic, remaining lower than average overall. At the end of the month, ice extent rose sharply, as winds changed and started spreading out the ice cover.

Sea ice extent in late winter can go up and down very quickly, getting pushed together or dispersed by strong winds. Ice extent usually reaches its annual maximum sometime in late February or March, but the exact date varies widely from year to year.

Arctic sea ice extent for February 2012 was 14.56 million square kilometers (5.62 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 February 2012 averaged 14.56 million square kilometers (5.62 million square miles). This is the fifth-lowest February ice extent in the 1979 to 2012 satellite data record, 1.06 million square kilometers (409,000 square miles) below the 1979 to 2000 average extent.

Continuing the pattern established in January, conditions differed greatly between the Atlantic and Pacific sides of the Arctic. On the Atlantic side, especially in the Barents Sea, air temperatures were higher than average and ice extent was unusually low. February ice extent for the Barents Sea was the lowest in the satellite record.  Air temperatures over the Laptev, Kara and Barents seas ranged from 4 to 8 degrees Celsius (7 to 14 degrees Fahrenheit) above average at the 925 hectopascal (hPa ) level (about 3000 feet above sea level).  In contrast, on the Pacific side, February ice extent in the Bering Sea was the second highest in the satellite record, paired with air temperatures that were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) below average at the 925 hPa level.

graph showing years and ice extent

The graph above shows daily Arctic sea ice extent as of March 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

Overall, the Arctic gained 956,000 square kilometers (369,000 square miles) of ice during the month. This was 486,000 square kilometers (188,000 square miles) more than the average ice growth for February 1979 to 2000. The overall low ice extent for the month stemmed mostly from the low ice extent in the Barents Sea: the extensive ice in the Bering Sea was not enough to compensate. On average, the Barents Sea has 865,000 square kilometers (334,000 square miles) of ice for the month of February. This year there were only 401,000 square kilometers (155,000 square miles) of ice in that region, the lowest recorded in the satellite data record.

At the end of February, ice extent rose sharply. Data from the NSIDC Multisensor Analyzed Sea Ice Extent (MASIE) showed that the rise came mainly from the Bering Sea and Baffin Bay. In the Bering Sea and Baffin Bay, winds pushed the ice extent southward. Ice growth in the Kara Sea also contributed to the rise in ice extent. In the Kara Sea, westerly winds that had been keeping the area ice-free shifted, allowing the open water areas to freeze over. During late winter, ice extent can change quickly as winds push extensive ice cover together, or spread out ice floes over a greater area.

Monthly February ice extent for 1979 to 2012 shows a decline of 3.0% per decade.

Credit: National Snow and Ice Data Center
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February 2012 compared to past years
Arctic sea ice extent for February 2012 was the fifth lowest in the satellite record. Including the year 2012, the linear rate of decline for February ice extent over the satellite record is 3.0% per decade. Based on the satellite record, through 2003, average February ice extent had never been lower than 15 million square kilometers (5.79 million square miles). February ice extent has not exceeded that mark eight out of the nine years since 2003.

This photograph of sea ice near Greenland was taken on March 18, 2011 from the NASA P3 aircraft. The IceBridge mission is collecting data on ice thickness, an important measure of the health of sea ice.

Credit: NASA/ATM automatic Cambot system
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IceBridge thickness data
Measuring ice thickness is critical to assessing the overall health of Arctic sea ice. The passive microwave data that NSIDC presents here provide only ice extent, a two-dimensional measure of ice cover. But ice can vary in thickness from a few centimeters to several meters, and scientists want to know if the ice pack is thinning overall as well as declining in extent. A new study by NASA scientist Ron Kwok compared ice thickness data collected by airplanes during the ongoing Operation IceBridge with thickness data from the NASA Ice, Cloud and Land Elevation Satellite (ICESat), which ended its mission in 2009. IceBridge is an airborne data-collection mission that started in 2009, in order to bridge the data gap between the first ICESat and ICESat-2, which is scheduled to launch in 2016.

Kwok found good agreement between simultaneous IceBridge and ICESat freeboard measurements made in 2009. Freeboard is the elevation of sea ice above the ocean surface, and provides a measure of ice thickness. These results show that IceBridge measurements will be able to bridge the gap between the ICESat and ICESat-2 satellite missions and add to other ice thickness data from the European Space Association (ESA) Cryosat-2. Satellite measurements of ice thickness provide a third dimension of information on the changing sea ice cover, helping scientists to more accurately assess the amount of sea ice in the Arctic.

Data collected by the IceBridge mission is archived and distributed by the NSIDC IceBridge Data program.

These images show the general effects of the positive phase (left) and negative phase (right) of the NAO. Red dots show the location of harp seal breeding grounds.

Credit: Johnston, et. al., 2012
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Regional ice conditions and harp seals
Many animals rely on sea ice as part of their habitat. Harp seals, for example, give birth to and care for their young on floes of sea ice. Recent research by David Johnston and colleagues at Duke University showed that harp seals in the northwest Atlantic have higher mortality rates during years when the North Atlantic Oscillation (NAO) is in its negative phase, a pattern that favors low ice cover in the Labrador Sea and Gulf of St. Lawrence, where harp seals breed. 

This winter, the NAO has mostly been in a positive phase and ice conditions in the Labrador Sea and Gulf of St. Lawrence have been at near-normal levels. However, in recent years, ice conditions in the region have been very low. The study showed a longer-term decline in sea ice cover of up to 6% per decade across all North Atlantic harp seal breeding grounds since 1979. While harp seals are well-suited to deal with natural short-term shifts in ice conditions, they may not be able to adapt to the combined effects of both short-term variability and long-term climate change.

Further reading
Friedlaender, A.S., D.W. Johnston and P.N. Halpin. 2010. Effects of the North Atlantic Oscillation on sea ice breeding habitats of harp seals (Pagophilus groenlandicus) across the North Atlantic, Progress in Oceanography, 86, 261-266. 

Johnston DW, Bowers MT, Friedlaender AS , Lavigne DM. 2012. The Effects of Climate Change on Harp Seals (Pagophilus groenlandicus). PLoS ONE, 7(1): e29158. doi:10.1371/journal.pone.0029158.

Kwok, R., G.F. Cunningham, S.S. Manizade and W.B. Krabill. 2012. Arctic sea ice freeboard from IceBridge acquisitions in 2009: Estimates and comparisons with ICESat, Journal of Geophysical Research, Vol. 117, C02018, doi:10.1029/2011JC007654.

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
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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
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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
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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.

Positively Arctic: Arctic Oscillation switches phase

Arctic sea ice extent remained unusually low through December, especially in the Barents and Kara seas.  In sharp contrast to the past two winters, the winter of 2011 has so far seen a generally positive phase of the Arctic Oscillation, a weather pattern that helps to explain low snow cover extent and warmer than average conditions over much of the United States and Eastern Europe.  In Antarctica, where summer is beginning, sea ice extent is presently above average.

Figure 1. Arctic sea ice extent for December 2011 was 12.38 million square kilometers (4.78 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
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Overview of Conditions

Arctic sea ice extent in December 2011 averaged 12.38 million square kilometers (4.78 million square miles). This is the third lowest December ice extent in the 1979 to 2011 satellite data record, 970,000 square kilometers (375,000 square miles) below the 1979 to 2000 average extent.

Ice extent was particularly low on the Atlantic side of the Arctic, most notably in the Barents and Kara seas. The eastern coast of Hudson Bay did not freeze entirely until late in the month: normally, Hudson Bay has completely frozen over by the beginning of December. In the Bering Sea, ice extent was slightly above average.

Figure 2. The graph above shows daily Arctic sea ice extent as of January 3, 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
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Conditions in context
For the Arctic as a whole, ice extent for the month remained far below average. The Arctic sea ice cover grew slightly faster than average, but December started out with a lower-than-average ice extent.

Overall, the Arctic gained 2.37 million square kilometers (915,000 square miles) of ice during the month. The average ice gain for December was 1.86 million square kilometers (718,000 square miles). On December 31, Arctic sea ice extent was 13.25 million square kilometers (5.12 million square miles), 561,000 square kilometers (217,000 square miles) more than the ice extent on December 31, 2010, the lowest extent on December 31 in the satellite record.

Figure 3. Monthly December ice extent for 1979 to 2011 shows a decline of 3.5% per decade.

Credit: National Snow and Ice Data Center
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December 2011 compared to past years
Arctic sea ice extent for December 2011 was the third lowest in the satellite record. The five lowest December extents in the satellite record have occurred in the past six years. Including the year 2011, the linear rate of decline ice December ice extent over the satellite record is -3.5% per decade.

Figure 4. This map of air temperature anomalies at the 925 hPa level (approximately 3000 feet) for December 2011 shows near-normal or lower-than-average temperatures over much of the Arctic basin, while air temperatures over the Kara and Barents seas were warmer than normal.

Credit: NSIDC courtesy NOAA/ESRL PSD
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Arctic temperatures
Air temperatures in December were lower than average over much of the Arctic Ocean, but higher than average over the Kara and Barents seas. Higher-than-average temperatures in these regions stemmed from two major factors. First, where sea ice extent is low, heat can escape from areas of open water, warming the atmosphere. Second, surface winds in the Kara and Barents Sea ice blew persistently from the south, bringing in heat from lower latitudes. This imported heat also helped to keep sea ice extent low in this area. Conditions over Canada were also unusually warm during December, but conditions over southeast Greenland have been 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) colder than average, partly because of northerly winds in the area.

Figure 5. This graph shows daily Arctic Oscillation Index values from the NOAA Climate Prediction Center for early September 2011 to early January 2012. The index is a normalized (unitless) index of relative pressure anomalies between polar and mid-latitude regions.

Credit: NSIDC courtesy NOAA NWS Climate Prediction Center
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Positive phase of the Arctic Oscillation
The past two Arctic winters were dominated by a negative phase of the Arctic Oscillation, a large-scale weather pattern that brings generally warm conditions to the Arctic and colder conditions to Europe and North America. In contrast, the winter of 2011 has so far seen a mostly positive phase of the Arctic Oscillation. While temperatures were above normal in the Kara and Barents seas, the positive phase of the Arctic Oscillation tends to keep the coldest winter air locked up in the Arctic, which keeps the middle latitudes free of frigid Arctic temperatures and strong snowstorms. This weather pattern helps to explain the low snow cover and warm conditions over much of the United States and Eastern Europe so far this winter.

Several studies have shown that during the positive phase of the Arctic Oscillation, thick ice tends to move out of the Arctic through Fram Strait, leaving the Arctic with thinner ice that melts out more easily in summer. Scientists will be watching closely for this connection if the positive phase of the Arctic Oscillation continues through the winter.

Some scientists have speculated that the negative Arctic Oscillation pattern of the last two winters was in part driven by low sea ice extent. The recurrence of the positive phase of the Arctic Oscillation so far this winter, following a near-record low summer sea ice extent, suggests that other factors play an important role.

Figure 6. This full-year graph puts 2011 sea ice extent in context. The gray line shows the 1979 to 2000 climatology, thick blue-gray indicates the 1981 to 2010 (30-year) climatology. NOAA this year switched to using the period 1981 to 2010 for their thirty-year climate comparison period. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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2011 year in review
Arctic sea ice extent fell to its seasonal minimum on September 9, 2011, falling just short of the record low set in September 2007, when summer weather conditions were extremely favorable for ice loss. This summer, the weather was not as extreme as 2007, so it was surprising that ice extent dropped so low. The low ice extent, along with data on ice age, suggests that the Arctic ice cover remains thin and vulnerable to summer melt.

Northern Hemisphere snow cover retreated very rapidly last spring, with record and near-record low snow cover extents in May and June despite higher-than-average winter snow extent as of February and March.

Figure 7. This graph shows Antarctic sea ice extent as of January 3, 2011. This year’s sea ice extent is shown in light blue, and 2010 is shown in dark blue. 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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A quick look at Antarctica
After a particularly slow ice loss rate at the beginning of the month, Antarctic sea ice extent was unusually high through much of December, in particular in the northern Ross Sea and the eastern Weddell Sea. December and November have had a markedly strong Amundsen Sea Low, an atmospheric pressure pattern that tends to spread the sea ice cover northward in the Ross Sea. Low pressure over the eastern Weddell Sea later in the month had the same effect there. Sea ice for the Antarctic in December 2011 was the fifth-highest for that month in the satellite record; the highest December extent occurred in 2007. Overall though, Antarctic sea ice extent remained below or near normal for most of 2011. Antarctic sea ice data are available on the Sea Ice Index Web site.

References
Rigor, I. G., and J. M. Wallace. 2004. Variations in the age of Arctic sea-ice and summer sea-ice extent, Geophys. Res. Lett., 31, L09401, doi:10.1029/2004GL019492.

Winter in the Arctic: Ice and storms

Arctic sea ice continued its winter expansion, although ice growth slowed briefly in early November. The slowdown may have been related to a strong Arctic storm that tracked from the Bering Sea into the Beaufort and Chukchi seas. In the Southern Hemisphere, Antarctic sea ice is tracking near average for this time of year.

map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent for November 2011 was 10.01 million square kilometers (3.86 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
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Overview of conditions

Average ice extent for November 2011 was 10.01 million square kilometers (3.86 million square miles), 1.30 million square kilometers (502,000 square miles) below the 1979 to 2000 average. This was 170,000 square kilometers (66,000 square miles) above the average for November 2006, the lowest extent recorded for that month in the satellite data record.

At the end of November, ice extent remained below the 1979 to 2000 average in the Chukchi, Barents and Kara seas, and Hudson Bay was still nearly ice free. Ice extent was near average in the East Greenland and the Bering seas. These ice conditions may be connected to a strong positive phase of the Arctic Oscillation, which began during the last week of November. A positive Arctic Oscillation tends to help move ice out of Fram Strait and into the North Atlantic.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily Arctic sea ice extent as of December 1, 2011, 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
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Conditions in context

The Arctic sea ice cover grew at an average pace through November, despite a brief slowdown early in the month. However, the ice extent remained far below average. Overall, the Arctic gained 2.36 million square kilometers (911,000 square miles) of ice during the month, which was slightly more than the average ice gain for November of 2.13 million square kilometers (822,000 square miles). On November 30, Arctic sea ice extent was 10.85 million square kilometers (4.19 million square miles), 625,000 square kilometers (241,000 square miles) more than the ice extent on November 30, 2006, the lowest extent on November 30 in the satellite record.

graph with months on x axis and extent on y axis Figure 3. Monthly November ice extent for 1979 to 2011 shows a decline of 4.7% per decade.

—Credit: National Snow and Ice Data Center
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November 2011 compared to past years

Ice extent for November 2011 was the third lowest in the satellite record for the month, behind 2006 and 2010. The linear rate of decline for November over the satellite record is now 53,200 square kilometers (20,500 square miles) per year, or 4.7% per decade relative to the 1979 to 2000 average.

graph with months on x axis and extent on y axis Figure 4. This map of air temperature anomalies at the 925 hPa level (approximately 3000 feet) for November 2011 shows near-normal or lower-than-average temperatures over much of the Arctic basin, while air
temperatures over the Kara and Barents Seas and Greenland were warmer than normal.
—Credit: NSIDC courtesy NOAA/ESRL PSD
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Atmospheric conditions and an Arctic storm

Low sea ice extent this summer may be contributing to warmer November temperatures and lower November ice extents in some areas. In recent years, low sea ice extent in the summer has been linked to unusually warm autumn air temperatures, resulting from the larger areas of open water that absorb more heat during the summer. This heat must escape back to the atmosphere in the fall, before the ocean can freeze over. This escaping heat contributes to warmer-than-average conditions, which have been most apparent in October but may also extend into November.

This November, air temperatures were near or slightly below average over most of the Arctic basin, but higher air temperatures were found over the Kara and Barents seas, the East Greenland Sea and the Canadian Archipelago: in general, the regions with above-average temperatures were the regions with below-average ice extent.

Lower than average temperatures in the Beaufort and Bering seas may be in part related to a strong low-pressure system that developed early in the month. In early November, a low-pressure system moved up from the Bering Sea into the Arctic, bringing strong winds and flooding to coastal villages in western Alaska. With a core pressure as low as 947 millibars, it was the strongest November storm to hit northwest Alaska since 1974. Much of the area affected by the storm was in areas that are typically ice-free, so the lack of sea ice probably did not play a direct role in the damage. For more information, see the Icelights article: An Arctic Hurricane?

graph with months on x axis and extent on y axis Figure 5. This map shows snow cover this November, compared to the 1971 to 2000 average. Areas in orange and red had lower snow cover than usual, while areas in blue had more snow than normal during November.

—Credit: NSIDC courtesy David Robinson, Rutgers University Snow Cover Laboratory
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Northern Hemisphere snow cover

The positive phase of the Arctic Oscillation also tends to be associated with unusually warm conditions over Scandinavia. According to Sweden’s meteorological office, the country’s average temperature for the month of November so far was 7 degrees Celsius (12.6 degrees Fahrenheit) above average. Typically by November, much of Scandinavia is already covered with snow, but maps from the Rutgers University Global Snow Lab show that snow cover levels were anomalously low over Scandinavia and northwestern Europe during November. Below-normal snow conditions were also evident over most of the continental United States, except for the northern Rockies.

However, overall Northern Hemisphere snow cover was more extensive than normal this November, with most of the extra snow cover found in Canada and Russia. Snow covered an average of 36.2 million square kilometers (14.0 million square miles) of Northern Hemisphere land. This is 2.79 million square kilometers (1.08 million square miles) above the 1971 to 2000 mean, and ranks as the fourth most extensive cover in the past 46 years of satellite-derived snow cover records.

Along with sea ice, change in snow cover can be an indicator of climate change. Higher air temperatures have resulted in a decline in snow cover in the spring, but in fall, the signal is more mixed. Some scientists also suspect there may be a link between early season high-latitude snow cover and winter weather patterns in the mid-latitudes. Judah Cohen and Justin Jones of Atmospheric and Environmental Research in Massachusetts have examined a potential link and suggest that this information could be used to improve winter forecasts. However, this research is still preliminary.

graph with months on x axis and extent on y axis Figure 6. This graph shows Antarctic sea ice extent as of December 1, 2011. This year’s sea ice extent is shown in light blue, and 2010 is shown in dark blue. 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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A look at Antarctica

Arctic Sea Ice News & Analysis generally focuses on sea ice conditions in the Arctic, since these conditions are closely tied to climate and weather in the Northern Hemisphere. A seasonal cover of sea ice also surrounds the continent of Antarctica. Since reaching its seasonal maximum in September, Antarctic sea ice has been near average in recent months. In November, Antarctic extent was 16.15 million square kilometers (6.24 million square miles), 87,000 square kilometers (33,600 square miles) less than the 1979 to 2000 average. In recent years, the sea ice cover that surrounds the Antarctic continent has been higher than average, even reaching near-record highs.

Antarctic sea ice varies much more from year to year than Arctic sea ice, but overall, ice extent around Antarctica has been growing slightly over the past 30 years. The ice cover around Antarctica also varies widely by region, with some regions, for example the Amundsen and Bellingshausen seas, showing strong declines over the past three decades, while other regions such as the Ross Sea have seen significant increases. For more information on Antarctic sea ice, see All About Sea Ice: Antarctic vs. Arctic. Antarctic sea ice data are available from the Sea Ice Index.

Further Reading

Cohen, J., and J. Jones, 2011. A new index for more accurate winter predictions, Geophysical Research Letters, vol. 38, L21701, doi:10.1029/2011/GL049626.

NOAA has released their annual Arctic Report Card, an annual compilation of scientific observations of the changing Arctic region. NSIDC scientist Walt Meier contributed to the sea ice section of the report.

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