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
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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.

Cold snap causes late-season growth spurt

Arctic sea ice reached its maximum extent for the year on March 31 at 15.25 million square kilometers (5.89 million square miles). This was the latest date for the maximum Arctic sea ice extent since the start of the satellite record in 1979.

Early in March, Arctic sea ice appeared to reach a maximum extent. However, after a short decline, the ice continued to grow. By the end of March, total extent approached 1979 to 2000 average levels for this time of year. The late-season growth was driven mainly by cold weather and winds from the north over the Bering and Barents Seas. Meanwhile, temperatures over the central Arctic Ocean remained above normal and the winter ice cover remained young and thin compared to earlier years.

map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent for March 2010 was 15.10 million square kilometers (5.83 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 averaged for March 2010 was 15.10 million square kilometers (5.83 million square miles). This was 650,000 square kilometers (250,000 square miles) below the 1979 to 2000 average for March, but 670,000 square kilometers (260,000 square miles) above the record low for the month, which occurred in March 2006.

Ice extent was above normal in the Bering Sea and Baltic Sea, but remained below normal over much of the Atlantic sector of the Arctic, including the Baffin Bay, and the Canadian Maritime Provinces seaboard. Extent in other regions was near average.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of April 4, 2010. The solid light blue line indicates 2010; green shows 2007; dark blue indicates 1999, the year with the previous latest maximum extent, which occurred on March 29, 1999; 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

Sea ice reached its maximum extent for the year on March 31, the latest maximum date in the satellite record. The previous latest date was on March 29, 1999. The maximum extent was 15.25 million square kilometers (5.89 million square miles). This was 670,000 square kilometers (260,000 square miles) above the record low maximum extent, which occurred in 2006.

Sea ice extent seemed to reach a maximum during the early part of the month, but after a brief decline, ice extent increased slowly and steadily through the end of the month. By the end of the month, extent had approached the 1979 to 2000 average. During March 2010, ice extent grew at an average of 13,200 square kilometers (5100 square miles) per day. Usually there is a net loss of ice through the month.

average monthly data from 1979-2009
Figure 3. Monthly March ice extent for 1979 to 2010 shows a decline of 2.6% per decade. —Credit: National Snow and Ice Data Center
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March 2010 compared to past years

The average ice extent for March 2010 was 670,000 square kilometers (260,000 square miles) higher than the record low for March, observed in 2006. The linear rate of decline for March over the 1978 to 2010 period is 2.6% per decade.

figure 4: air pressure map
Figure 4. The map of sea level pressure (in millibars) for March 2010 shows high pressure over the central Arctic (areas in yellow and orange) and areas of low pressure over the Bering and Barents seas (areas in blue and purple). The low pressure systems over the Bering and Barents seas have helped to push the ice edge southward. —Credit: National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Division
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Late-season growth spurt

The maximum Arctic sea ice extent may occur as early as mid-February to as late as the last week of March. As sea ice extent approaches the seasonal maximum, extent can vary quite a bit from day to day because the thin, new ice at the edge of the pack is sensitive to local wind and temperature patterns. This March, low atmospheric pressure systems persisted over the Gulf of Alaska and north of Scandinavia. These pressure patterns led to unusually cold conditions and persistent northerly winds in the Bering and Barents Seas, which pushed the ice edge southward in these two regions.

figure 5: air temperature map
Figure 5. This map of air temperature anomalies for March 2010, at the 925 millibar level (roughly 1,000 meters or 3,000 feet above the surface), shows warmer than usual temperatures over most of the Arctic Ocean, but colder than usual temperatures in the Bering and Barents seas, where sea ice extent is above normal. Areas in orange and red correspond to positive (warm) anomalies. Areas in blue and purple correspond to negative (cool) anomalies. —Credit: National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Division
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Meanwhile, elsewhere in the Arctic

This winter’s strong negative mode of the Arctic Oscillation was moderated through the month of March. Average air temperatures for the month nevertheless remained above average over the Arctic Ocean region. Overall for the winter, temperatures over most of the Arctic were above average, while northern Europe and Siberia were colder than usual.

figure 6: ice age image
Figure 6. These images show the change in ice age from fall 2009 to spring 2010. The negative Arctic Oscillation this winter slowed the export of older ice out of the Arctic. As a result, the percentage of ice older than two years was greater at the end of March 2010 than over the past few years. —Credit: National Snow and Ice Data Center courtesy J. Maslanik and C. Fowler, CU Boulder
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Ice age and thickness

The late date of the maximum extent, though of special interest this year, is unlikely to have an impact on summer ice extent. The ice that formed late in the season is thin, and will melt quickly when temperatures rise.

Scientists often use ice age data as a way to infer ice thickness—one of the most important factors influencing end-of-summer ice extent. Although the Arctic has much less thick, multiyear ice than it did during the 1980s and 1990s, this winter has seen some replenishment: the Arctic lost less ice the past two summers compared to 2007, and the strong negative Arctic Oscillation this winter prevented as much ice from moving out of the Arctic. The larger amount of multiyear ice could help more ice to survive the summer melt season. However, this replenishment consists primarily of younger, two- to three-year-old multiyear ice; the oldest, and thickest multiyear ice has continued to decline. Although thickness plays an important role in ice melt, summer ice conditions will also depend strongly on weather patterns through the melt season.

At the moment there are no Arctic-wide satellite measurements of ice thickness, because of the end of the NASA Ice, Cloud, and Land Elevation Satellite (ICESat) mission last October. NASA has mounted an airborne sensor campaign called IceBridge to fill this observational gap.

More Information

For more information, including animations and satellite images, visit the NASA Arctic 2010 Sea Ice Maximum Web page.

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