Poles apart: A record-breaking summer and winter

The sun has set over the central Arctic Ocean and sea ice extent is now increasing. While much attention has been paid to the record minimum Arctic ice extent set on September 16, 2012, winter sea ice extent in Antarctica has reached a record high. The Antarctic extent increase is an interesting response to changes in circulation patterns in the Southern Hemisphere.

Overview of conditions

Figure 1. Arctic sea ice extent for September 2012 was 3.61 million square kilometers (1.39 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

Following the record minimum that was set on September 16, 2012, Arctic sea ice has started its seasonal pattern of growth; maximum seasonal extent is expected to be reached by the end of March of next year.

Arctic sea ice extent averaged for September 2012 was 3.61 million square kilometers (1.39 million square miles). This was 3.43 million square kilometers (1.32 million square miles) below the 1979 to 2000 average extent. September 2012 ice extent was 690,000 square kilometers (266,000 square miles) less than the previous record low for the month that occurred in 2007.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 30, 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

The seasonal minimum in extent that occurred this year on September 16 was three days later than the average date of the minimum (September 13). Because ice extent falls through the first part of September and rises in the latter part, statistics on the average daily rate of ice loss or gain through the month are largely meaningless. More relevant is the total ice loss through the melt season. Between the seasonal maximum extent that occurred on March 20, 2012 and the September 16 minimum, the Arctic Ocean lost a total of 11.83 million square kilometers (4.57 million square miles) of ice; this is by far the largest seasonal loss of sea ice in the satellite record. The second largest seasonal loss was 10.65 million square kilometers (4.11 million square miles), in 2008. Due in part to transfers of heat from extensive open water areas to the atmosphere, air temperatures at the 925 hPa level averaged for September 2012 were from 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) above average over much of the Arctic Ocean; much larger departures from average were the rule at levels closer to the surface.

September 2012 compared to previous years

Figure 3. Monthly September ice extent for 1979 to 2012 shows a decline of 13.0% per decade.

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

Arctic sea ice extent averaged for September 2012 was the lowest in the satellite record, and was 16% lower than the previous low for the month, which occurred in 2007. Through 2012, the linear rate of decline for September Arctic ice extent over the satellite record is now 13.0% per decade, relative to the 1979 to 2000 average. The six lowest September ice extents over the satellite record have all occurred in the last six years. Compared to the 1979 to 2000 average ice conditions, the September 2012 ice cover represents a 49% reduction in the area of the Arctic Ocean covered by sea ice. It is 2.91 million square kilometers (1.12 million square miles), or 45%, below the 30-year average over 1981 to 2010.

Summer weather conditions: 2012 compared to 2007

Figure 4. These images compare sea level pressure and temperature anomalies (at the 925 hPa level) during summer 2007, the previous record low extent year, and summer 2012. Anomalies were less pronounced in 2012 than in 2007 (as shown in reds and oranges). While weather was a factor in the 2007 record low extent, the 2012 record extent occurred during near average weather conditions.

Credit: NSIDC courtesy NOAA/ESRL PSD
High-resolution image

Weather conditions prevailing over the summer of 2012 were quite different from those in 2007. The summer of 2007 featured unusually high sea level pressure centered north of the Beaufort Sea and Greenland, and unusually low pressure along northern Eurasia, bringing in warm southerly winds along the shores of the East Siberian and Chukchi seas (3 to 5 degrees Celsius, or 5 to 9 degrees Fahrenheit above normal), favoring strong ice melt in these sectors and pushing the ice away from the coast, leaving open water. The pressure pattern also favored the transport of ice out of the Arctic Ocean and into the North Atlantic through Fram Strait.

In contrast, the summer of 2012 saw unusually low pressure along the Eurasian coastal seas and extending eastward into the Beaufort sea, most prominently over the East Siberian Sea, with unusually high pressure centered over Greenland and the northern North Atlantic. Air temperatures for summer 2012 were above average over most of the Arctic Ocean (1 to 3 degrees Celsius, or 2 to 5 degrees Fahrenheit), most prominently over the Beaufort Sea, where, because of the pressure pattern, winds were anomalously from the south. Melt began two to three weeks earlier than average in the Barents and Kara seas, leading to earlier retreat of sea ice in the region; however, air temperatures remained below average during summer in this region. This points to the impact the continued loss of old, thick ice is having on the ability of the sea ice cover to survive summer melt. Other than the August storm, the pressure pattern in 2012 does not appear to have been as favorable in promoting ice loss as was the case in 2007, and yet a new record low occurred.

Old, thick ice dwindles; young, thin ice prevails

Figure 5. These images from September 2007 (top, left) and September 2012 (top, right) show the decline of multiyear ice since the previous record minimum extent was set in 2007. The chart at bottom shows the changes in multiyear ice from 1983 to 2012. Ice of all ages has declined; 5+ year old ice has declined quite sharply. Much of the Arctic ice cover now consists of first-year ice (shown in purple), which tends to melt rapidly in summer’s warmth.

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

Entering the melt season, a thinner ice cover made the Arctic sea ice cover more vulnerable to weather, such as the storm that tracked through the Arctic in early August. Because the ice was thin and already decaying by the time of the storm, it was quickly broken up and melted by winds and waves.

The end-of-summer sea ice cover was not only the least extensive in the satellite record, but also very likely the lowest volume, based on combined model-observation estimates from the University of Washington, and inferred from ice age. The extent of ice of nearly all age categories declined from last year and remained at record low levels. The only category that increased was 4-year-old ice. This is ice that has aged since the previous record low minimum extent in 2007, when substantial amounts of first-year ice were lost. This 4-year-old ice will now age into the 5+ year category as the ice-growth season begins. However, even with this replenishment this winter will see only approximately 20% of the old (5+ year) ice compared to the 1980s. Because of the record summer ice loss, this winter will see the Arctic Ocean region even more dominated by the thinner first-year ice. As shown in Figure 5, the amount of ice in nearly all age categories has decreased since 2007, particularly the oldest ice.

For more information and visualizations of thinning sea ice, see the NOAA Climate Watch article, “Arctic Sea Ice Getting Thinner, Younger.”

A view towards the south

Figure 6a. Antarctic sea ice extent for September 26, 2012 (top image) was 19.44 million square kilometers (7.51 million square miles). The orange line shows the 1979 to 2000 median extent for that day of the year. The black cross indicates the geographic South Pole. The graph (bottom) shows Antarctic sea ice extent as of September 30, 2012. 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

Figure 6b. The monthly September Antarctic extent trend for 1979 to 2012 is +0.9% per decade.

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

As the Arctic was experiencing a record low minimum extent, the Antarctic was reaching record high levels in the satellite record, culminating in a winter maximum extent of 19.44 million square kilometers (7.51 million square miles) on September 26. The September 2012 monthly average was also a record high, at 19.39 million square kilometers (7.49 million square miles) slightly higher than the previous record in 2006.

The September extent trend for 1979 to 2012 is just above the statistical significance level (0.9% per decade, plus or minus 0.6%). The new Antarctic sea ice September value is slightly greater than typical year-to-year variations, and is roughly equal to a 25 mile (40 kilometer) northward shift in the location of the ice edge relative to the 1979 to 2000 average. The trend for ice extent growth during Antarctic winters is about 16,000 square kilometers per year (6,200 square miles) or roughly an area the size of Connecticut. In comparison, the decline in Arctic summer sea ice extent is an area about the size of Indiana (91,600 square kilometers per year, or about 35,400 square miles).

Our colleague, Dr. Sharon Stammerjohn of INSTAAR, University of Colorado, provides a review of the differences between Arctic and Antarctic climate controls on sea ice and helps place the events in context. First, climate is warming over much of the Antarctic continent, as shown in several recent studies (e.g., Chapman and Walsh, 2007, Monaghan et al., 2008, Steig et al., 2009) and is related to Pacific Ocean warming (Ding et al., 2010) and circumpolar winds. Both warming and ozone loss act to strengthen the circumpolar winds in the south. This is due primarily to persistently cold conditions prevailing on Antarctica year-round, and a cold stratosphere above Antarctica due to the ozone hole. Stronger winds generally act to blow the sea ice outward, slightly increasing the extent, except in the Antarctic Peninsula region, where due to geography, winds from the north have also increased, pushing the ice southward. Thus, sea ice extent near the northwestern Antarctic Peninsula continues to decline rapidly, while areas in the Ross Sea and the southern Indian Ocean show significant increases (Stammerjohn et al., 2012). Circumpolar-averaged sea ice extent changes nearly cancel each other out for all months of the year (Parkinson and Cavalieri, 2012). This winter, atmospheric conditions were near average overall, with roughly equal areas of cooler and warmer air temperatures over the sea ice.

Comparing winter and summer sea ice trends for the two poles is problematic since different processes are in effect. During summer, surface melt and ice-albedo feedbacks are in effect; winter processes include snowfall on the sea ice, and wind. Small changes in winter extent may be a more mixed signal than the loss of summer sea ice extent. An expansion of winter Antarctic ice could be due to cooling, winds, or snowfall, whereas Arctic summer sea ice decline is more closely linked to decadal climate warming.

For more information on Antarctic climate and sea ice, see NSIDC’s Icelights, our Sea Ice Index, and our State of the Cryosphere Web sites. The NASA Goddard Ozone Watch site also provides additional background information.

Table 1: Previous Arctic sea ice extents for the month of September

Year Average Arctic Sea Ice Extent for September Trend, in % per decade (relative to 1979-2000 avg.)
in millions of square kilometers in millions of square miles
2007 4.30 1.66 -10.2
2008 4.73 1.83 -11.0
2009 5.36 2.08 -11.1
2010 4.90 1.90 -11.5
2011 4.61 1.78 -12.0
2012 3.61 1.39 -13.0
1979 to 2000 average 7.04 2.72
1979 to 2010 average 6.52 2.52

References

Parkinson, C., and D. Cavalieri. 2012. Antarctic sea ice variability and trends. The Cryosphere 6, 871-880, doi:10.5194/tc-6-871-2012.

Stammerjohn, S., R. Massom, D. Rind, and D. Martinson. 2012. Regions of rapid sea ice change: an inter-hemispheric seasonal comparison. Geophysical Research Letters 39, L06501, doi:10.1029/2012GL050874.

Ding, Q., E. Steig, D. Battisi, and M. Kuttel. 2011. Winter warming in West Antarctica caused by central tropical Pacific warming. Nature Geoscience 4, doi:10.1038/ngeo1129.

Steig, E., D. P. Schneider, S. D. Rutherford, M. Mann, J. C. Comiso, and D. T. Shindell. 2009. Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year. Nature 457, 459-462, doi:10.1038/nature07669.

Monaghan, A. J., D. H. Bromwich, W. Chapman, and J. Comiso. 2008. Recent variability and trends of Antarctic near-surface temperature. Journal of Geophysical Research 113, D04105, doi:10.1029/2007JD009094.

Chapman, W. L., and J. E. Walsh. 2007. A synthesis of Antarctic temperatures. Journal of Climate 20 (16), 4096-4117, doi:10.1175/JCLI4236.1.

Video animations of sea ice extent

Arctic sea ice extent settles at record seasonal minimum

On September 16, Arctic sea ice appeared to have reached its minimum extent for the year of 3.41 million square kilometers (1.32 million square miles). This is the lowest seasonal minimum extent in the satellite record since 1979 and reinforces the long-term downward trend in Arctic ice extent. The sea ice extent will now begin its seasonal increase through autumn and winter.

Please note that this is a preliminary announcement. Changing winds could still push ice floes together, reducing ice extent further. NSIDC scientists will release a full analysis of the melt season in early October, once monthly data are available for September.

Overview of conditions

Figure 1. Arctic sea ice extent for September 16, 2012 was 3.41 million square kilometers (1.32 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
High-resolution image

On September 16, 2012 sea ice extent dropped to 3.41 million square kilometers (1.32 million square miles). This appears to have been the lowest extent of the year. In response to the setting sun and falling temperatures, ice extent will now climb through autumn and winter. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower. The minimum extent was reached three days later than the 1979 to 2000 average minimum date of September 13.

This year’s minimum was 760,000 square kilometers (293,000 square miles) below the previous record minimum extent in the satellite record, which occurred on September 18, 2007.  This is an area about the size of the state of Texas. The September 2012 minimum was in turn 3.29 million square kilometers (1.27 million square miles) below the 1979 to 2000 average minimum, representing an area nearly twice the size of the state of Alaska. This year’s minimum is 18% below 2007 and 49% below the 1979 to 2000 average.

Overall there was a loss of 11.83 million square kilometers (4.57 million square miles) of ice since the maximum extent occurred on March 20, 2012, which is the largest summer ice extent loss in the satellite record, more than one million square kilometers greater than in any previous year.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 17, 2012, along with daily ice extent data for 2007 and 2005, the previous record low years. 2012 is shown in blue 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

The six lowest seasonal minimum ice extents in the satellite record have all occurred in the last six years (2007 to 2012). In contrast to 2007, when climatic conditions (winds, clouds, air temperatures) favored summer ice loss, this year’s conditions were not as extreme. Summer temperatures across the Arctic were warmer than average, but cooler than in 2007. The most notable event was a very strong storm centered over the central Arctic Ocean in early August. It is likely that the primary reason for the large loss of ice this summer is that the ice cover has continued to thin and become more dominated by seasonal ice. This thinner ice was more prone to be broken up and melted by weather events, such as the strong low pressure system just mentioned. The storm sped up the loss of the thin ice that appears to have been already on the verge of melting completely.

 Varying distribution of ice in 2012 vs. 2007

Figure 3. The image above shows the different distribution of ice extent at the time of the September 2012 minimum, compared to the September 2007 minimum. Dark gray indicates where ice extent was present only in 2007; white indicates where ice extent was present only in 2012; and light gray shows where ice extent was present in both 2007 and 2012.

Credit: National Snow and Ice Data Center
High resolution image

The spatial pattern of ice extent at this year’s seasonal minimum is different than that observed for 2007. This year the ice is more extensive in some parts of the central Arctic Ocean. However, the ice is less extensive this year compared to 2007 in the Beaufort Sea, the western Laptev Sea, the East Greenland Sea, and parts of the Canadian Archipelago. As mentioned in our previous post, the Northern Sea Route opened around mid August this year, compared to 2007 when a tongue of ice extended to the coast, blocking the route throughout the summer.

Previous minimum Arctic sea ice extents

Table 1. Previous minimum Arctic sea ice extents
 Year Minimum Ice Extent Date
in millions of square kilometers in millions of square miles
2007 4.17 1.61 September 18
2008 4.59 1.77 September 20
2009 5.13 1.98 September 13
2010 4.63 1.79 September 21
2011 4.33 1.67 September 11
2012 3.41 1.32 September 16
1979 to 2000 average 6.70 2.59 September 13
1979 to 2010 average 6.14 2.37 September 15

Note that the dates and extents of the minimums have changed since we originally posted in 2007; see our Frequently Asked Questions for more information.

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.

A most interesting Arctic summer

Arctic sea ice extent declined quickly in July, continuing the pattern seen in June. On August 1, ice extent was just below levels recorded for the same date in 2007, the year that saw the record minimum ice extent in September. Low sea ice concentrations are present over large parts of the western Arctic Ocean. Warm conditions dominated the weather for most of the Arctic Ocean and surrounding lands. For a brief period in early July, nearly all of the Greenland ice sheet experienced surface melt, a rare event.

Overview of conditions

Sea ice image for July 2012

Figure 1. Arctic sea ice extent for July 2012 was 7.94 million square kilometers (3.07 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 for July 2012 averaged 7.94 million square kilometers (3.07 million square miles). This was 2.12 million square kilometers (819,000 square miles) below the 1979 to 2000 average extent. July 2012 ice extent was 20,000 square kilometers (7,700 square miles) above the 2011 record July low.

As throughout the summer, the low ice extent for the Arctic as a whole is primarily due to extensive open water on the Atlantic side of the Arctic (Kara, Laptev and East Siberian seas) and the Beaufort Sea. By August 1, open water in the Laptev Sea, along the Siberian coast, had reached nearly 80oN latitude. Ice extent remains near average in the Chukchi Sea, and ice continues to block sections of the both the Northern Sea Route and the Northwest Passage. The ice extent recorded for August 1 of 6.53 million square kilometers (2.52 million square kilometers) is the lowest in the satellite record. The previous record for the same date was set in 2007 at 6.64 million square kilometers (2.56 million square miles), when the current record low September ice extent was set.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 5, 2012, along with daily ice extent data for the 2011 and for 2007, the record low year. 2012 is shown in blue, 2011 in orange, 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

In July, the Arctic lost a total of 2.97 million square kilometers (1.15 million square miles) of ice. The largest July total loss, 3.53 million square kilometers (1.36 million square miles) occurred in the year 2007. Warm conditions prevailed over most of the Arctic Ocean; temperatures at the 925 hPa level (about 3,000 feet above the ocean surface) were typically 1 to 3 degrees Celsius (1.8 to 5.4 degrees Fahrenheit) above the 1981 to 2010 average over the Beaufort Sea and regions to the north, as well as over Baffin Bay. By contrast, temperatures were 1 to 3 degrees Celsius below average over the Norwegian Sea. Weather patterns over the Arctic Ocean varied substantially through the month, as they have done throughout the melt season.

July 2012 compared to recent years

Graph of sea ice extent trend

Figure 3. Monthly July ice extent for 1979 to 2012 shows a decline of 7.1% per decade.

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

Arctic sea ice extent for July 2012 was the second lowest in the satellite record, behind 2011. Through 2012, the linear rate of decline for July Arctic ice extent over the satellite record is 7.1% per decade.

MODIS data shows low concentration ice

MODIS image of sea ice

Figure 4. This image from the Moderate Resolution Imaging Spectroradiometer (MODIS), taken in late July, shows areas of low concentration sea ice in the Beaufort Sea, north of Alaska. Barrow, Alaska is at the top left. The resolution is 500 meters. The cloud band covering much of the lower right part of the image is associated with an approaching storm.

Credit: NASA Goddard Space Flight Center, Rapid Response
High-resolution image

In our last post (July 24, 2012) we commented on large areas of low ice concentration depicted in Special Sensor Microwave Imager/Sounder (SSMIS) data in the Beaufort and Chukchi seas, the Canadian Archipelago, the East Greenland Sea, and north of Siberia. These areas of low ice concentration ice can be seen clearly in visible-band data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua and Terra satellites.

The MODIS image shows polygonal floes of multi-year ice, as well as thin, gray first-year ice, and dark open water in the Beaufort Sea, north of Alaska. Most of these areas of low concentration ice will likely melt over the next month. Because MODIS senses light reflected from the surface as opposed to the emission of microwave radiation, its ability to see the surface depends on cloud cover.

Comparisons between observed and modeled September sea ice trends

Graph of sea ice model results

Figure 5. This figure shows the observed September sea ice extent for 1952 to 2011 (bold black line) and extents for 1900 to 2100 from the CMIP3 models using the “business as usual” SRESA1B greenhouse gas emissions scenario (the blue line averaging results from all of the model runs with the blue shading showing the +/- 1 standard deviation of the different model runs) and from the CMIP5 archive, using the RCP 4.5 scenario (pink line and pink shading). The darker pink shading shows where the simulations from CMIP3 and CMIP5 overlap each other.

Credit: National Snow and Ice Data Center courtesy Stroeve et al. 2012
High-resolution image

Previous research at NSIDC documented that September Arctic ice extent has declined faster than models predicted it would. The comparison was between observations and simulated trends from models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (CMIP3). These climate models were used in the 2007 4th Assessment report of the Intergovernmental Panel on Climate Change (IPCC). In a new paper, Stroeve et al. (2012) compared the observed 1979-2011 September trend for the Arctic against trends over the same period from the next generation of models in the CMIP5 archive. While the newer CMIP5 models do a better job of simulating the observed trend, most of the modeled ice extent trends are still smaller than the observed downward trend. NSIDC is working with researchers to further improve the models, which help extend and refine our understanding of the climate system.

Extensive melt over the Greenland Ice Sheet

Figure 6. This figure shows the daily, cumulative area of the Greenland ice sheet showing surface melt for 2012, 2011, 2010 and for the 1980 to 1999 mean. While melt was unusually extensive through May and June of 2012, the melt area increased rapidly in early July in response to an unusually warm weather event.

Credit: National Snow and Ice Data Center courtesy Marco Tedesco, CUNY
High-resolution image

This summer, the ocean has not been the only place where unusual melt has been observed in the Arctic. NASA researchers reported that for several days in early July, nearly the entire Greenland ice sheet experienced a brief period of surface melt, including at the summit of the ice sheet. Typically, about half of the ice sheet sees some surface melting during summer, but this tends to be confined to the lower elevations. The 2012 event was associated with a high-pressure weather pattern bringing unusually warm temperatures over the higher elevations of the ice sheet. While the event has not been seen previously in the 34-year satellite record, there is evidence in ice core data from Summit, Greenland of similar events occurring several times over the past few thousand years. These melt events recorded in the ice cores from Summit show an overall average frequency of about once every 150 years since the end of the last ice age. Perhaps more important, however, is the extraordinary high melting occurring this year around the lower elevations in Greenland. Figure 6 shows that the first few months of melt exceeded past higher-than-average melt seasons. Flooding and damage to structures has been reported in some areas where this melt runs off the ice sheet and fills streams and rivers along the Greenland coast. The surface melt runoff, as well as the flow of ice and the resulting calving of icebergs, are contributors to sea level rise. Along with the substantial summer sea ice extent decline and the early Northern Hemisphere snow melt, the pace of Greenland surface melt suggests that 2012 is yet another interesting summer in the Arctic.

For more information and images, visit Greenland Melting.

References

Stroeve, J. C., V. Kattsov, A. P. Barrett, M. C. Serreze, T. Pavlova, M. M. Holland, and W. N. Meier. 2012. Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations. Geophys. Res. Lett., doi:10.1029/2012GL052676, in press.

Rapid sea ice retreat in June

Arctic sea ice extent declined quickly in June, setting record daily lows for a brief period in the middle of the month. Strong ice loss in the Kara, Bering, and Beaufort seas, and Hudson and Baffin bays, led the overall retreat. Northern Hemisphere snow extent was unusually low in May and June, continuing a pattern of rapid spring snow melt seen in the past six years.

sea ice extent

Figure 1. Arctic sea ice extent for June 2012 was 10.97 million square kilometers (4.24 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
Daily data files

Overview of conditions
Arctic sea ice extent for June 2012 averaged 10.97 million square kilometers (4.24 million square miles). This was 1.18 million square kilometers (456,000 square miles) below the 1979 to 2000 average extent. The last three Junes (2010-2012) are the three lowest in the satellite record. June 2012 ice extent was 140,000 square kilometers (54,000 square miles) above the 2010 record low. Ice losses were notable in the Kara Sea, and in the Beaufort Sea, where a large polynya has formed. Retreat of ice in the Hudson and Baffin bays also contributed to the low June 2012 extent. The only area of the Arctic where sea ice extent is currently above average is along the eastern Greenland coast.

The ice extent recorded for 30 June 2012 of 9.59 million square kilometers (3.70 million square miles) would not normally be expected until July 21, based on 1979-2000 averages. This puts extent decline three weeks ahead of schedule.

graph of sea ice extents

Figure 2. The graph above shows Arctic sea ice extent as of July 2, 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
Daily data files

Conditions in context
In June, the Arctic lost a total of 2.86 million square kilometers (1.10 million square miles) of ice. This is the largest June ice loss in the satellite record. Similar to May, the month was characterized by a period of especially rapid ice loss (discussed in the mid-month entry, June 19th) followed by a period of slower loss. Warm conditions prevailed over most of the Arctic; temperatures at the 925 hPa level (about 3000 feet above the ocean surface) were typically 1 to 4 degrees Celsius (1.8 to 7.2 degrees Fahrenheit) above the 1981 to 2010 average, and as much as 7 to 9 degrees Celsius (12.6 to 16.2 degrees Fahrenheit) above average over northern Eurasia and near southern Baffin Bay. Weather patterns over the Arctic Ocean varied substantially through the month.

Figure 3. Monthly June ice extent for 1979 to 2012 shows a decline of 3.7% per decade.

Credit: National Snow and Ice Data Center
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June 2012 compared to recent years
Arctic sea ice extent for June 2012 was well below average for the month compared to the satellite record from 1979 to 2000. It was the second lowest in the satellite record, behind 2010. Through 2012, the linear rate of decline for June Arctic ice extent over the satellite record is 3.7% per decade.

ice conditions in the field

Figure 4. These photographs show sea ice on the fast ice near Barrow, Alaska. (a) Chris Polashenski stands in a melt pond with instrumentation, (b) honeycombed sample of rotten ice taken from the bottom of a melt pond, (c) sea ice rubble field after winds pushed the weakened sea ice onto the shore.

Credit: National Snow and Ice Data Center, courtesy Chris Polanshenski of CRREL as part of the SIZONET project.
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A report from the field
Dr. Chris Polashenski of the Cold Regions Research Lab (CRREL) recently returned from making sea ice measurements on landfast ice a few kilometers offshore near Barrow, Alaska as part of the National Science Foundation and NASA funded Seasonal Ice Zone Observing Network (SIZONET) project. He and his fellow researchers made some interesting observations. Prior to the onset of melt, the ice was thicker than observed in recent years – around 1.8 meters (5.9 feet) as compared to typical conditions of around 1.4 meters (4.6 feet). Despite this thick ice at the beginning of the season, melt proceeded relatively rapidly. Melt ponds began forming on June 4—a typical timing for recent years, but high temperatures, sunny afternoons, and foggy nights combined to speed the melt of ice thereafter.

On June 17-18, a confluence of weather conditions, including a daytime high of 19 degrees Celsius (66 degrees Fahrenheit), overnight condensing fog, and bright sun in the afternoon combined to produce exceptional surface melt of just under 11 centimeters (4.3 inches) in a 24-hour period, according to preliminary lidar data. By June 18, ice conditions had deteriorated significantly and with strong winds forecast out of the west, safety dictated it was time to get off the ice. Collisions of the pack with the weakened shore fast ice on June 21-23 resulted in substantial deformation and a series of ice pushes onto the beach, an amazing process to watch from the safety of land.

Such field observations may only be representative of the local area. However, they provide context for basin-wide observations and a better understanding of local processes.

map of snow cover anomaliesmap of snow cover anomalies

Figure 5. June 2012 set a record low for Northern Hemisphere snow cover extent. Figure 5 (a) graphs snow extent for Junes from 1967 to 2012. Figure 5 (b) maps snow cover anomalies in the Northern Hemisphere.

Credit: National Snow and Ice Data Center courtesy Rutgers University Snow Lab.

High-resolution image: June snow cover anomalies graph
High-resolution image: June snow cover anomalies map

Graph of May snow cover anomalies

Map of May snow cover anomalies

Low June snow extent
Snow cover over Northern Hemisphere lands retreated rapidly in May and June, leaving the Arctic Ocean coastline nearly snow free. June 2012 set a record low for snow extent (for a 45-year period of record spanning 1967-2012) by a significant margin. Snow extent for June 2012 was more than 1 million square kilometers (386,000 square miles) below the previous record set in 2010. Snow extent for 2011 was a close third lowest. May 2012 had third lowest snow extent for the period of record. This rapid and early retreat of snow cover exposes large, darker underlying surfaces to the sun early in the season, fostering higher air temperatures and warmer soils.

A note on the daily sea ice data
NSIDC has published the underlying data used for the Daily Sea Ice Extent image and the Daily Sea Ice Extent 5-Month Time Series graph. Please see the links below for documentation for the Sea Ice Index and links to the data:

Documentation–Daily extent data file

Documentation–Climatology file

Arctic sea ice variable, ends May below average

After reaching near-average levels in late April, sea ice extent declined rapidly during the early part of May. The rest of the month saw a slower rate of decline. Ice extent in the Bering Sea remained above average throughout the month.

Figure 1. Arctic sea ice extent for May 2012 was 13.13 million square kilometers (5.07 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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Overview of conditions
Arctic sea ice extent for May 2012 averaged 13.13 million square kilometers (5.07 million square miles). This was 480,000 square kilometers (185,000 square miles) below the 1979 to 2000 average extent. This May’s extent was similar to the May 2008 – 2010 extent, but it was higher than May 2011. May ice extent was 550,000 square kilometers (212,000 square miles) above the record low for the month, which happened in the year 2004.

Ice cover remained extensive in the Bering Sea, continuing the pattern observed this past winter and spring. The anomalously heavy ice conditions were countered by unusually low extents in the Barents and Kara Seas, resulting in Arctic-wide ice conditions that remained below normal. By the end of the month, open water areas had begun to form along some parts of Arctic Ocean coast.

While the ice extent for May is not especially low this year, there is little correlation between the extent of the ice cover in May and that at the end of the melt season in September.

Figure 2. The graph above shows Arctic sea ice extent as of June 4, 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

Conditions in context
For May, the Arctic as a whole lost 1.62 million square kilometers (625,000 square miles) of ice, which was 180,000 square kilometers (69,500 square miles) more than the 1979 to 2000 average. The average daily rate of ice loss was 52,000 square kilometers (20,000 square miles) per day, which was slightly faster than the long-term average of 46,000 square kilometers (18,000 square miles) per day. However, the rate of ice loss for the month was composed of two distinct periods: a rapid loss of ice during the first part of the month, followed by near-average rates during the latter part of the month.

Air temperatures for May were higher than usual over the central Arctic Ocean and the Canadian Archipelago. Over the Bering Sea, Hudson Bay, and parts of the East Greenland and Norwegian seas, temperatures were slightly below average.

Figure 3. Monthly May ice extent for 1979 to 2012 shows a decline of 2.3% per decade.

Credit: National Snow and Ice Data Center
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May 2012 compared to past years
Arctic sea ice extent for May 2012 was below average for the month, compared to the satellite record from 1979 to 2000. However, the ice extent this May was not as low as it has been in some recent years. Including the year 2012, the linear rate of decline for May ice extent over the satellite record is 2.3% per decade.

May and April have the smallest trends of the year, indicating that spring is a period during the year when there is less variability and conditions tend to converge. It also demonstrates that spring extents are not necessarily indicative of conditions later in the summer.

Figure 4. This map of sea level pressure anomalies for May 2012 shows that low pressure continued to dominate off of southern Alaska, resulting in northerly winds in the Bering Sea.

Credit: NSIDC courtesy NOAA/ESRL PSD
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A persistent pattern of extensive ice in the Bering Sea

Continuing the pattern of the past six months, ice cover remained unusually extensive in the Bering Sea. Normally by the end of May, the Bering is largely ice-free, but this year, 350,000 square kilometers (135,000 square miles) of ice remained. As was also the case for February through April, May 2012 had the highest average Bering Sea ice extent for the month in the satellite record.

The higher than normal extent and late spring break up of the ice cover in the Bering Sea are mainly due to unusually low air temperatures and persistent winds from the north, related to a region of low atmospheric pressure centered over Kodiak, Alaska. As these cold winds slowed ice melt, they also pushed the ice edge to the south. The heavy ice in the region may delay the start of Shell Alaska’s Arctic drilling this summer, which will be the first exploratory drilling in the Arctic Ocean in 20 years.

With the overall springtime warming of the Arctic, the ice has nevertheless started to break up and large areas of open water are now present in the northern part of the Bering Sea.

Figure 5. In this Moderate Resolution Imaging Spectroradiometer (MODIS) Arctic Mosaic image for the Beaufort Sea on May 29, 2012, open water is apparent between fast ice along the coast and the broken-up floes off-shore. Toward the bottom of the image, thin clouds can be seen over the open water.

Credit: NASA/GSFC, Rapid Response
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Open water areas within the Arctic Ocean

Although ice extent has remained high in the Bering Sea, open water areas have developed in parts of the Arctic Ocean, notably along the coasts of the Beaufort and Laptev seas. These openings are largely driven by winds pushing the ice away from fast ice, ice that is attached to the coast and that does not move with the winds. That the open water areas have not refrozen points to the relatively warm conditions over the Arctic, particularly in the Beaufort Sea.

The ice cover in the southern Beaufort Sea is also substantially broken up, with many individual ice floes instead of a consolidated pack. This makes the ice in this region vulnerable to enhanced melt during summer, as the sun rises higher in the sky and the dark open water areas between the floes readily absorb solar energy.

Quicker thickness data from NASA IceBridge

As we discussed last month, thickness information is extremely important for understanding the state of the ice cover. It is particularly important to seasonal forecasts (such as the SEARCH Sea Ice Outlook that will be released later this month), because thinner ice is more likely to melt completely during summer.

Sea ice age can be inferred from satellite data, and can help indicate the locations of relatively thin versus relatively thick ice. But direct measurements of ice thickness have been limited. Satellite missions such as ICESat and CryoSat, which measure ice thickness with altimeters, have been extremely valuable in better understanding overall changes in Arctic sea ice volume.

Currently, the NASA IceBridge mission supplies both sea ice thickness and snow depth measurements in spring, providing timely information on the state of the ice cover as the melt season begins. IceBridge data are collected from aircraft that fly over the ice cover carrying a suite of instruments, including altimeters that can directly measure ice thickness above the surface. These measurements are at high spatial resolution that can also be used to validate satellite data.

This year, the IceBridge Arctic sea ice campaign collected data in late March and early April, and provided data to NSIDC for distribution shortly thereafter. The data, collected from the North American side of the Arctic, indicate thick ice north of Greenland due to wind and ocean current patterns piling ice into thick ridges. In the Beaufort Sea, the offshore ice is fairly thin (1 to 2 meters, or 3 to 6 feet), indicative of first-year ice. Such thin ice will be prone to melt out completely this summer.

Ice along the Alaskan coast is thicker. Thicker ice tends to have a deeper overlying snow cover. The amount of snow is an important factor in the summer melt, because the snow reflects solar energy. The snow must melt away before surface melting of the ice can begin in earnest.

A rapid freeze-up

Arctic sea ice extent increased rapidly through October, as is typical this time of year. Large areas of open water were still present in the Beaufort and Chukchi seas at the end of the month. The open water contributed to unusually warm conditions along the coast of Siberia and in the Beaufort and Chukchi seas.

map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent for October 2011 was 7.10 million square kilometers (2.74 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

Average ice extent for October 2011 was 7.10 million square kilometers (2.74 million square miles), 2.19 million square kilometers (846,000 square miles) below the 1979 to 2000 average. This was 330,000 square kilometers (127,000 square miles) above the average for October 2007, the lowest extent in the satellite record for that month. By the end of October, ice extent remained below the 1979 to 2000 average in the Beaufort and Chukchi seas and in the Barents and Kara seas. Extent was near average in the East Greenland Sea. New ice growth has closed both the Northwest Passage and the Northern Sea Route.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily Arctic sea ice extent as of November 6, 2011, along with the lowest ice extents in the preceding decades, 1984 and 1999. 2011 is shown in light blue. 2007, the year with the record low minimum, is dashed green. Purple indicates 1999 and light green shows 1984. 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

Arctic sea ice extent increased rapidly through October. Ice extent during October 2011 increased at an average rate of 114,900 square kilometers (44,360 square miles) per day, about 40% faster than the average growth rate for October 1979 to 2000. On October 30, Arctic sea ice extent was 8.41 million square kilometers (3.25 million square miles), 226,000 square kilometers (87,300 square miles) more than the ice extent on October 30, 2007, the lowest extent on that date in the satellite record.

During the month of October, the freeze-up that begins in September kicks into high gear. The rate of freeze-up depends on several factors including the atmospheric conditions and the amount of heat in the ocean that was accumulated during the summer. However, each decade, the October extent has started from a lower and lower point, with the record low extent during the 1980s (1984) substantially higher than the record low extent during the 1990s (1999), which in turn is substantially higher than the record low extent during the 2000s (2007).

graph with months on x axis and extent on y axis Figure 3. Monthly October ice extent for 1979 to 2011 shows a decline of 6.6% per decade. —Credit: National Snow and Ice Data Center
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October 2011 compared to past years

Ice extent for October 2011 was the second lowest in the satellite record for the month, behind 2007. The linear rate of decline for October over the satellite record is now -61,700 square kilometers (-23,800 square miles) per year, or -6.6% 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 October 2011 shows unusually high temperatures over most of the Arctic Ocean (yellow shading) and unusually low temperatures over the eastern Canadian Arctic Archipelago and Greenland (blue shading). —Credit: National Snow and Ice Data Center
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Atmospheric conditions

In recent years, low sea ice extent in the summer has been linked to unusually warm temperatures at the surface of the Arctic Ocean in the fall. This pattern appeared yet again this fall.

Air temperatures over most of the Arctic Ocean for October 2011 ranged from 1 to 4 degrees Celsius (1.8 to 7.2 degrees Fahrenheit) above average, measured at the 925 millibar level, about 1,000 meters or 3,000 feet above the surface. However, over the eastern Canadian Arctic and Greenland, temperatures were as much as 3 degrees Celsius (5.4 degrees Fahrenheit) below average.

These temperature anomalies in part reflect a pattern of above-average sea level pressure centered over the northern Beaufort Sea, and lower than average sea level pressure extending across northern Eurasia. This pattern is linked to persistence of the positive phase of the Arctic Oscillation through most of the month. These pressure and temperature anomalies tend to bring in heat from the south, warming the Eurasian coast, but they also lead to cold northerly winds over the eastern Canadian Arctic Archipelago. However, along the Siberian coast and in the Beaufort and Chukchi seas, warmer temperatures came primarily from the remaining areas of open water in the region, as heat escaped from the water. These effects are more strongly apparent in the surface air temperatures: average October temperatures in the region were 5 to 8 degrees Celsius (9.0 to 14.4 degrees Fahrenheit) above average.

graph with months on x axis and extent on y axis Figure 5. The top panel of this figure shows the number of open water days for the approximate 75 kilometer (46.6 mi) coastal zone along the Beaufort Sea (data for each year and linear trend). The bottom panel shows the average annual coastal erosion rate for three periods, 1979-1999, 2000-2007 and 2008-2009. —Credit: NSIDC courtesy Irina Overeem, CU Boulder
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Sea ice loss and coastal erosion

Declining sea ice in the Arctic has led to increasing erosion rates along the coast of the Beaufort Sea over the past fifty years, according to a new study led by Irina Overeem of the University of Colorado Institute for Arctic and Alpine Research (INSTAAR). Their study used a wave model driven by sea ice position and wind data.

As the period of open water on the coast of the Beaufort Sea has increased, so has the mean annual erosion rate, the study showed. From 1979 to 1999, the average erosion rate was 8.5 meters (27.9 feet) per year. The average rate over the period 2000 to 2007 was 13.6 meters (44.6 feet) per year, while the rate for the last two years of the record, 2008 to 2009, was 14.4 meters (47.2 feet) per year.

With a longer open water season, ocean water warms more and waves eat away at the coastline. The sediments comprising the coastal bluffs are locked together by permafrost—hard frozen ground with a concrete-like consistency. As the waves lap at the permafrost, they also help to thaw it, making the ground much more vulnerable to erosion.

Further ReadingOvereem, I., R.S. Anderson, C.W. Wobus, G.D. Clow, F.E. Urban, and N. Matell. 2011: Sea ice loss enhances wave action at the Arctic coast. Geophysical Research Letters, 38, L17503, doi:10.1029/2011GL048681.

Serreze, M.C., and R.G. Barry. 2011: Processes and impacts of Arctic Amplification: A research synthesis. Global and Planetary Change, 77,85-96.

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

Weather and feedbacks lead to third-lowest extent

An eventful summer sea ice melt season has ended in the Arctic. Ice extent reached its low for the year, the third lowest in the satellite record, on 19 September. Both the Northwest Passage and the Northern Sea Route were open for a period during September.
map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent for September 2010 was 4.90 million square kilometers (1.89 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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Overview of conditions

Average ice extent for September 2010 was 4.90 million square kilometers (1.89 million square miles), 2.14 million square kilometers (830,000 square miles) below the 1979 to 2000 average, but 600,000 square kilometers (230,000 square miles) above the average for September 2007, the lowest monthly extent in the satellite record. Ice extent was below the 1979 to 2000 average everywhere except in the East Greenland Sea near Svalbard.

The U.S. National Ice Center declared both the Northwest Passage and the Northern Sea Route open for a period during September. Stephen Howell of Environment Canada reported a record early melt-out and low extent in the western Parry Channel region of the Northwest Passage, based on analyses of the Canadian Ice Service. Two sailing expeditions, one Norwegian and one Russian, successfully navigated both passages and are nearing their goal of circumnavigating the Arctic.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily Arctic sea ice extent as of October 3, 2010, along with daily ice extents for years wtih the previous four lowest minimum extents. The solid light blue line indicates 2010; dark blue shows 2009, purple shows 2008; dashed green shows 2007; light green shows 2005; and solid gray indicates average extent from 1979 to 2000. 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

After the minimum extent of 4.60 million square kilometers (1.78 million square kilometers) on September 19, 2010, a rapid freeze-up has begun. On October 1, the 5-day average ice extent was 5.44 million square kilometers (2.10 million square miles).

monthly graph
Figure 3. Monthly September ice extent for 1979 to 2010 shows a decline of 11.5% per decade. 

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

September 2010 compared to past years

Ice extent for September 2010 was the third lowest in the satellite record for the month, behind 2007 (lowest) and 2008 (second lowest). The linear rate of decline of September ice extent over the period 1979 to 2010 is now 81,400 square kilometers (31,400 square miles) per year, or 11.5% per decade relative to the 1979 to 2000 average. Sea ice extent at the end of the melt season is shaped by conditions in the atmosphere and ocean, as well as the condition of the ice cover itself.

figure 4: SLP fields for Sept 2010
Figure 4. These maps of sea level pressure for late summer show atmospheric conditions during August 2010 (left), and September 2010 (right). In August, high pressure over the Beaufort was paired with low pressure over Siberia. This pattern persisted through the first week of September, then broke down. —Credit: NSIDC courtesy NOAA/ESRL PSD
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The atmosphere
During the summer of 2010, atmospheric conditions shifted between warm conditions that favored melt, and stormy conditions that slowed the melt rate but helped break up the ice. The net effects of atmospheric conditions this season contributed to the low ice extent.

At the beginning of the melt season, ice extent was relatively high after a long winter dominated by an extreme negative phase of the Arctic Oscillation. Historically, these winter conditions would favor retention of ice through the summer. But in June, a combination of high pressure over the central Arctic Ocean and unusually low pressure over Siberia gave rise to warm conditions over much of the Arctic Ocean and strong westward ice motion off the Siberian Coast, favoring rapid ice melt. In contrast, a series of low-pressure systems moved into the central Arctic Ocean in July. While slowing the melt rate, the stormy conditions helped to break up the sea ice cover. August saw a return to the basic pattern seen in June, although not as prominent. This pattern persisted through the first week of September, helping to drive the sea ice toward what appeared to be its seasonal minimum on September 10. After ice extent started to climb, a change in atmospheric conditions caused it to fall again, to reach its final value of 4.60 million square kilometers (1.78 million square miles) on September 19.

figure 4: SST for August 2007 to 2010
Figure 5. This summer, sea surface temperatures were higher than average, but lower than in the last three years. The maps above show average sea surface temperatures and anomalies for August 2007 to 2010.—Credit: National Snow and Ice Data Center courtesy M. Steele, University of Washington
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The ocean

As in recent years, sea surface temperatures this summer were higher than normal in much of the Arctic Ocean, according to researchers at the University of Washington. Mike Steele, Wendy Ermold, and Ignatius Rigor found that temperatures in the Beaufort/Chukchi Seas and the region north of the Laptev Sea were particularly high. The high sea surrface temperatures resulted largely from the loss of sea ice: dark open water areas absorb more solar radiation than reflective ice. The warmer water in turn helps to melt more sea ice. This positive feedback likely contributed to the ice loss through summer 2010, especially late in the season when surface melt had largely ceased.

figure 6: ice age image
Figure 6. These images show the change in ice age from spring 2010 to fall 2010. The negative phase of the Arctic Oscillation this winter slowed the export of older ice out of the Arctic in the winter, but a large amount of older ice melted out during the summer.—Credit: National Snow and Ice Data Center ourtesy C. Fowler and J. Maslanik, CU Boulder
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The ice

Researchers often look at ice age as a way to estimate ice thickness. Older ice tends to be thicker than younger, one- or two-year-old ice. Last winter, the wind patterns associated with the negative phase of the Arctic Oscillation transported a great deal of multiyear ice from the coast of the Canadian Arctic into the Beaufort and Chukchi seas. Scientists speculated that much of this ice, some five years or older, would survive the summer melt period. Instead, it mostly melted away. At the end of the summer 2010, under 15% of the ice remaining the Arctic was more than two years old, compared to 50 to 60% during the 1980s. There is virtually none of the oldest (at least five years old) ice remaining in the Arctic (less than 60,000 square kilometers [23,000 square miles] compared to 2 million square kilometers [722,000 square miles] during the 1980s).

Whether younger multiyear ice (two or three years old) in the Arctic Ocean will continue to age and thicken depends on two things: first, how much of that ice stays in the Arctic instead of exiting into the North Atlantic through Fram Strait; and second, whether the ice survives its transit across the Beaufort and Chukchi Seas or instead melts away.

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

Updated minimum Arctic sea ice extent

After appearing to reach its annual minimum extent on September 10, and beginning to freeze up, Arctic sea ice again declined for several days. Ice extent reached its lowest value for the season on September 19, 2010, and has now been expanding for seven days.
map from space showing sea ice extent, continentsFigure 1. Daily Arctic sea ice extent on September 19, 2010 was 4.60 million square kilometers (1.78 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

After appearing to reach a low point on September 10, sea ice extent rose for three days and then began a second decline. Ice extent dropped to its lowest extent for the year on September 19, at 4.60 million square kilometers (1.78 million square miles) .

The 2010 minimum ice extent was the third-lowest recorded since 1979. The 2010 minimum ice extent was 37,000 square kilometers (14,000 square miles) above 2008; 470,000 square kilometers (181,000 square miles) above the record minimum in 2007; and 500,000 square kilometers (193,000 square miles) below 2009, previously the third lowest extent since 1979. The 2010 minimum ice extent was 2.11 million square kilometers (815,000 square miles) below the 1979 to 2000 average and 1.74 million square kilometers (672,000 square miles) below the 1979 to 2009 average.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily Arctic sea ice extent as of September 26, 2010, along with daily ice extents for years wtih the previous four lowest minimum extents. The solid light blue line indicates 2010; orange shows 2009, pink shows 2008; dashed green shows 2007; light green shows 2005; and solid gray indicates average extent from 1979 to 2000. 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 revised minimum ice extent on September 19 occurred ten days later than the average date of the minimum ice extent for the period 1979 to 2000, and 8 days later than the 1979 to 2009 average. With the additional days of ice loss, 2010 is no longer the shortest period of summer ice loss since 1979.

comparison map showing ice extent in 2010 and 2007 Figure 3. This image compares differences in ice-covered areas between September 19, 2010, the date of this year’s minimum, and September 16, 2007, the record low minimum extent. Light gray shading indicates the region where ice occurred in both 2007 and 2010, while white and dark gray areas show ice cover unique to 2010 and to 2007, respectively. Sea Ice Index data. —Credit: National Snow and Ice Data Center
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2010 minimum ice extent compared to 2007

Compared to the 2007 seasonal minimum, the 2010 minimum had less ice in the northern Beaufort Sea region, the East Greenland Sea and the western Laptev Sea. However, there was much more ice in the East Siberian Sea this year compared to 2007.

Final analysis pending

In the beginning of October, NSIDC will issue a formal announcement with a full analysis of the melt season, and graphics comparing this year to the long-term record. We will also announce the monthly average September sea ice extent, the measure scientists rely on for accurate analysis and comparison over the long term.

We will continue to post analyses of sea ice conditions throughout the year, with frequency determined by sea ice conditions. The near-real-time daily image update will continue each day.

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

Arctic sea ice reaches annual minimum extent

Update: 21 September 2010

Although ice extent appeared to reach a minimum on September 10, rising afterwards for three straight days, it has subsequently declined even further. NSIDC scientists are closely monitoring the ice extent and will provide another update on the data, as conditions develop.

Our season-end announcement in October will provide the final numbers for the minimum extent, as well as the monthly data for September, which scientists use for establishing long-term trends.

Arctic sea ice appears to have reached its annual minimum extent on 10 September. The minimum ice extent was the third-lowest in the satellite record, after 2007 and 2008, and continues the trend of decreasing summer sea ice.

map from space showing sea ice extent, continentsFigure 1. Daily Arctic sea ice extent on September 10, 2010 was 4.76 million square kilometers (1.84 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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Overview of conditions

On September 10, 2010 sea ice extent dropped to 4.76 million square kilometers (1.84 million square miles). This appears to have been the lowest extent of the year; sea ice has now begun its annual cycle of growth.

The 2010 minimum ice extent is the third-lowest recorded since 1979. The 2010 minimum extent is 240,000 square kilometers (93,000 square miles) above 2008 and 630,000 square kilometers (240,000 square miles) above the record low in 2007. This is 340,000 square kilometers (130,000 square miles) below 2009. The 2010 minimum is 1.95 million square kilometers (753,000 square miles) below the 1979 to 2000 average minimum and 1.62 million square kilometers (625,000 square miles) below the thirty-one-year 1979 to 2009 average minimum.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily Arctic sea ice extent as of September 13, 2010, along with daily ice extents for years wtih the previous four lowest minimum extents. The solid light blue line indicates 2010; orange shows 2009, pink shows 2008; dashed green shows 2007; light green shows 2005; and solid gray indicates average extent from 1979 to 2000. 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

This is only the third time in the satellite record that ice extent has fallen below 5 million square kilometers (1.93 million square miles), and all those occurrences have been within the past four years. The minimum for 2009 was 5.10 million square kilometers (1.97 million square miles), fourth lowest in the satellite record.

Despite a late start to the melt season, the ice extent declined rapidly thereafter, with record daily average ice loss rates for the Arctic as a whole for May and June. Assuming that we have indeed reached the seasonal minimum extent, 2010 would have the shortest melt season in the satellite record, spanning 163 days between the seasonal maximum and minimum ice extents.

difference chart
Figure 3. This image compares differences in ice-covered areas between September 10, 2010, the date of this year’s minimum, and September 16, 2007, the record low minimum extent. Light gray shading indicates the region where ice occurred in both 2007 and 2010, while white and dark gray areas show ice cover unique to 2010 and to 2007, respectively. Sea Ice Index data. About the data. —Credit: National Snow and Ice Data Center
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Comparison of the 2010 and 2007 September minima

At the 2010 seasonal minimum, ice remained fairly extensive in the East Siberian Sea, compared to 2007, when this area was ice free. 2010 ended up having less ice than 2007 in the Beaufort Sea and in the East Greenland Sea. Both the Northwest Passage and Northern Sea Route (along the shores of Eurasia) were open at the 2010 sea ice minimum, whereas in 2007, ice blocked part of the Northern Sea Route.

modis map
Figure 4. This image, from the NASA MODIS sensor on the Aqua satellite on September 14, shows new ice (dark gray region within circled area) is evident, growing outward from the remaining ice pack (white colored region) in the northwestern East Siberian Sea. The new ice appeared within the previous two days. —Credit: NSIDC courtesy NASA/GSFC MODIS Rapid Response
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Evidence of freeze onset

Visible imagery from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) confirms that freeze-up is starting in some parts of the Arctic. Growth of new ice is visible in the image from September 14, 2010 extending off the remaining ice pack in the northwestern part of the East Siberian Sea. The new ice formed within the past couple days. Extent may still be declining in other regions, primarily due to heat from ocean waters.

A word of caution on calling the minimum

Because of the variability of sea ice at this time of year, the National Snow and Ice Data Center determines the minimum using a five-day running mean value. We have now seen four days of gains in extent. It is still possible that ice extent could fall slightly, because of either further melting or a contraction in the area of the pack due to the motion of the ice. For example, in 2005, the time series began to level out in early September, prompting speculation that we had reached the minimum. However, the sea ice contracted later in the season, again reducing sea ice extent and causing a further drop in the absolute minimum. When all the data for September are in, we will confirm the minimum ice extent for the season.

Final analysis pending

In the beginning of October, NSIDC will issue a formal announcement with a full analysis of the melt season, and graphics comparing this year to the long-term record. We will also announce the monthly average September sea ice extent, the measure scientists rely on for accurate analysis and comparison over the long term.

We will continue to post analyses of sea ice conditions throughout the year, with frequency determined by sea ice conditions. The near-real-time daily image update will continue each day.

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