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
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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
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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
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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.