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
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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
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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
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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
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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
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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
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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 .

Annual maximum extent reached

On March 15, 2013, Arctic sea ice extent appears to have reached its annual maximum extent, marking the beginning of the sea ice melt season. This year’s maximum extent was the sixth lowest in the satellite record. NSIDC will release a detailed analysis of the 2012 to 2013 winter sea ice conditions in early April.

Overview of conditions

Figure 1. Arctic sea ice extent on March 15 was 15.13 million square kilometers (5.84 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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On March 15, 2013 Arctic sea ice likely reached its maximum extent for the year, at 15.13 million square kilometers (5.84 million square miles). The maximum extent was 733,000 square kilometers (283,000 square miles) below the 1979 to 2000 average of 15.86 million square kilometers (6.12 million square miles). The maximum occurred five days later than the 1979 to 2000 average date of March 10. The date of the maximum has varied considerably over the years, with the earliest maximum in the satellite record occurring as early as February 24 in 1996 and as late as April 2 in 2010.

This year’s maximum ice extent was the sixth lowest in the satellite record. The lowest maximum extent occurred in 2011. The ten lowest maximums in the satellite record have occurred in the last ten years, 2004 to 2013.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 24, 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
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Over the 2012 to 2013 winter season, sea ice extent grew a record 11.72 million square kilometers (4.53 million square miles). The record growth was primarily a result of the record low minimum last September, leaving a greater extent of ocean surface uncovered in ice to re-freeze this winter. This seasonal ice gain is 645,000 square kilometers (249,000 square miles) higher than the previous record (2007 to 2008) and 2.63 million square kilometer (1.02 million square miles) higher than the 1979 to 2000 average. Last autumn’s record low and this winter’s record ice growth indicate a more pronounced seasonal cycle in Arctic sea ice and the increasing dominance of first-year ice in the Arctic.

Final analysis pending

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

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
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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.