A real hole near the pole

Sea ice continued its late-season summer decline through August at a near-average pace. Ice extent is still well above last year’s level, but below the 1981 to 2010 average. Open water was observed in the ice cover close to the North Pole, while in the Antarctic, sea ice has been at a record high the past few days.

Overview of conditions

Figure 1. Arctic sea ice extent for August 2013 was X.xx million square kilometers (X.XX million square miles). The magenta line shows the 1981 to 2010 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

Figure 1. Arctic sea ice extent for August 2013 was 6.09 million square kilometers (2.35 million square miles). The magenta line shows the 1981 to 2010 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

Sea ice extent for August 2013 averaged 6.09 million square kilometers (2.35 million square miles). This was 1.13 million square kilometers (398,000 square miles) below the 1981 to 2010 average for August, but well above the level recorded last year, which was the lowest September extent in the satellite record. Ice extent this August was similar to the years 2008 to 2010. These contrasts in ice extent from one year to the next highlight the year-to-year variability attending the overall, long-term decline in sea ice extent.

Extent in the Beaufort and Chukchi seas has dropped below average, after near average conditions in July. The only region with average extent is the East Siberian Sea.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 4, 2013, along with daily ice extent data for the previous five years. 2013 is shown in light blue, 2012 in green, 2011 in orange, 2010 in light purple, 2009 in dark blue, and 2008 in dark purple. 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

Figure 2. The graph above shows Arctic sea ice extent as of September 4, 2013, along with daily ice extent data for the previous five years. 2013 is shown in light blue, 2012 in green, 2011 in orange, 2010 in light purple, 2009 in dark blue, and 2008 in dark purple. 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

Relatively cool conditions over the central Arctic Ocean continued, a pattern that has characterized this summer. Temperatures at the 925 hPa level in the high Arctic (north of Greenland to the North Pole) were 0.5 to 3 degrees Celsius (1 to 5 degrees Fahrenheit) below the 1981 to 2010 average. In comparison, temperatures in coastal areas of the Arctic were mostly near average, and temperatures in the Barents and Beaufort seas were about 2 degrees Celsius (4 degrees Fahrenheit) above average. The distribution of the temperature anomalies can be related to the sea level pressure pattern. Below-average sea level pressures were linked to cloudy and cool conditions near the North Pole and extending into the northern North Atlantic. In contrast, above-average pressures dominated the Eurasian coast.

August 2013 compared to previous years

Figure 3. Monthly June ice extent for 1979 to 201X shows a decline of X.X% per decade.||Credit: National Snow and Ice Data Center |High-resolution image

Figure 3. Monthly August ice extent for 1979 to 2013 shows a decline of 10.6% per decade.

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

The seasonal decline of extent through the month of August was slightly above average at 56,400 square kilometers (21,800 square miles) per day, but more than a third slower than the record decline rate in August 2012. This year’s August extent was the sixth lowest in the 1979 to 2013 satellite record.

August 2013 ice extent was 1.38 million square kilometers (533,000 square miles) above the record low August extent in 2012. The monthly trend is –10.6% per decade relative to the 1981 to 2010 average.

Water near the pole

Figure 4. This image from the AMSR2 satellite instrument shows Arctic sea ice concentration for September 2, 2013. A dark blue area of apparent open water can be seen near the North Pole, surrounded by a low ice concentration area. The gray circle indicates where the instrument did not acquire data, due to its orbit.|\Credit: NSIDC/University of Bremen|High-resolution image

Figure 4. This image from the AMSR2 satellite instrument shows Arctic sea ice concentration for September 2, 2013. A dark blue area of apparent open water can be seen near the North Pole, surrounded by a low ice concentration area. The gray circle around the North Pole indicates where the instrument did not acquire data, due to its orbit.

Credit: NSIDC/University of Bremen
High-resolution image

Earlier this summer, there was considerable interest in seeing liquid water in the North Pole Environmental Observatory (NPEO) web cam. As explained in our August 7 post, that region was simply a shallow melt pond of water atop the ice and not an actual opening in the ice. Nevertheless, our August 19 post described an extensive region of low ice concentration located fairly close to the pole.

Now, a large hole (roughly 150 square kilometers or 58 square miles) of near-zero ice concentration appears to have opened up at about 87 degrees North latitude. Small areas of open water are common within the ice pack, even at the North Pole, as the ice pack shifts in response to winds and currents, resulting in cracks (called leads) in the ice. The current opening seen in our satellite imagery is much larger. In 2006, a larger polynya appeared in the Beaufort and Chukchi seas, but it was much farther south.

Melting ice from above and below

Figure 4. . Results from six ice mass balance buoys that operated throughout the summer of 2013. The red dot denotes the buoy position on 28 August 2013. The red bar indicates the total amount of summer surface melt and the yellow bar shows bottom melt. The white background is the MASIE ice extent on 28 August 2013 mapped on Google Earth.||Credit: Julienne Stroeve/National Snow and Ice Data Center |High-resolution image

Figure 5. This map of the Arctic shows results from six ice mass balance buoys that operated throughout the summer of 2013. A red dot denotes each buoy position on August 28, 2013. The red bars indicate the total amount of summer surface melt and the yellow bars show bottom melt. The white background is the MASIE ice extent on August 28, 2013 mapped on Google Earth.

Credit: NSIDC courtesy Jackie Richter-Menge and Don Perovich/CRREL
High-resolution image

It may seem contradictory for a polynya-like opening to form near the pole while temperatures are lower than average, but it highlights the complex interplay between the ice, atmosphere, and ocean. Such openings in the ice occur two ways: through winds pushing the ice apart, or through melting. Both processes likely played a role in forming the current opening, but another key factor is a significant amount of thin, first-year ice in the region. This thin ice was more likely to melt completely than surrounding thicker ice. Heat from the ocean also contributes to melting of the ice from below, even though air temperatures have been below average in the region. Buoys that measure ice mass can provide information on surface and bottom melting.

During the summer of 2013 there were six ice mass balance buoys deployed in the Arctic over a wide area (red dots in Figure 5). The buoys were deployed in undeformed, multiyear ice, with a thickness between 2.2 and 3.5 meters (7 and 11 feet) before melt began. Data from the buoys show that the amount of surface ice melting ranged from 0 in the central Arctic, to 75 centimeters (30 inches) in the Beaufort Sea. Bottom melting varied from 8 to 108 centimeters (3 to 43 inches). The largest amount of bottom melting was observed at a buoy near the ice edge in the Beaufort Sea. This buoy had the largest total amount of melt, thinning from 339 centimeters (133 inches) in early June, to 157 centimeters (62 inches) on August 28. Ice thicknesses at the other buoys on August 28 ranged from 121 to 267 centimeters (48 to 105 inches). While bottom melting is continuing in some locations, most of this year’s surface melting has occurred. Data from the ice mass balance buoys are available at http://imb.crrel.usace.army.mil. (Thanks to Jackie Richter-Menge and Don Perovich at the Cold Regions Research and Engineering Laboratory [CRREL] for this part of the discussion.)

A change of pace

Sea ice extent retreated fairly rapidly through the first two weeks of July as a high pressure cell moved into the central Arctic, bringing warmer temperatures over much of the Arctic Ocean. Ice extent remains below average on the Atlantic side of the Arctic, and is near average to locally above average in the Beaufort and Chukchi seas and along much of the Eurasian coast.

Overview of conditions

Figure 1. Arctic sea ice extent for July 15, 2013 was 8.20 million square kilometers (3.17 million square miles). The orange line shows the 1981 to 2010 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

While the rate of Arctic sea ice loss is normally fastest during July, the warmest month of the year, ice loss was even faster than usual over the first two weeks of July 2013. As a result, on July 15 extent came within 540,000 square kilometers (208,000 square miles) of that seen in 2012 on the same date. The ice loss is dominated by retreat on the Atlantic side of the Arctic, including the East Greenland, Kara and Laptev seas, and Baffin Bay. In the Beaufort and Chukchi seas and much of the Eurasian coast, the ice cover remains fairly extensive, especially compared to recent summers. Compared to the 1981 to 2010 average, ice extent on July 15, 2013 was 1.06 million square kilometers (409,000 square miles) below average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July 15, 2013, along with daily ice extent data for 2012, the record low year. 2013 is shown in blue, and 2012 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

During the first two weeks of July, ice extent declined at a rate of 132,000 square kilometers (51,000 square miles) per day. This was 61% faster than the average rate of decline over the period 1981 to 2010 of 82,000 square kilometers (32,000 square miles) per day. The fast pace of ice loss was dominated by retreat in the Kara and East Greenland seas, where the ice loss rate from July 1 to 12 was -16,409 and -17,678 square kilometers (-6,336 and -6,826 square miles) per day, respectively. The Laptev Sea ice retreated at about half that rate, at -8,810 square kilometers (-3,402 square miles) per day.  In contrast, on the Pacific side, sea ice has been slow to retreat. During the first part of July, the rate of ice loss in the Beaufort and Chukchi seas was only -3,375 and -6,829 square kilometers (-1,303 and -2,637 square miles), respectively.

A change in the weather

Figure 3a

Figure 3a. This image of air temperature anomalies at the 925 hPa level from July 1 to 10 July 10, 2013 shows higher than average temperatures over the Arctic, especially over the Kara Sea. Air temperature anomalies are relative to the 1981 to 2010 average.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

Fig3b

Figure 3b. This image of average sea level pressure from July 1 to 10, 2013 shows high pressure in the central Arctic.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
High-resolution image

Temperatures at the 925 hPa level for the first two weeks in July were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) above average over much of the Arctic Ocean and as much as 5 degrees Celsius (9 degrees Fahrenheit) above average over the Kara Sea, where ice loss was pronounced. In contrast, temperatures over Alaska, Siberia and the Canadian Arctic were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) lower than average.

Warmer conditions have been paired with a shift in the atmospheric circulation, with a high pressure cell at sea level pressure moving into the central Arctic, replacing then pattern of low pressure that dominated the month of June. This has helped to bring in warm air from the south over the Arctic Ocean. This pattern has also helped to create open water areas in the Laptev Sea because offshore winds push the ice away from shore.

 

Slow ice retreat along coastal Alaska and Canada

Figure 4.

Figure 4. This graph of sea ice extent in the Beaufort and Chukchi Seas as of July 12 each year shows an increase in ice extent in the Beaufort Sea over the last seven summers.

Credit: NSIDC
High-resolution image

The slow retreat of sea ice in the Beaufort Sea has resulted in the most extensive ice cover seen there in the last seven summers (Figure 4). Ice extent also remains rather extensive in the Chukchi Sea, though other recent years have seen more ice at this same time of year, particularly in 2012, when Shell was forced to delay drilling operations and reduce the number of wells planned. Despite extensive ice cover, visible imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument shows melt is well underway.

A new normal for Arctic sea ice

Arctic sea ice continues to track below average but remains well above the levels seen last year. The relatively slow ice loss is a reflection of the prevailing temperature and wind patterns. As of July 1, NSIDC Arctic Sea Ice News and Analysis and the Sea Ice Index have transitioned to a new 30-year baseline period, 1981 to 2010.

Overview of conditions

June 2013 sea ice extent

Figure 1. Arctic sea ice extent for June 2013 was 11.58 million square kilometers (4.47 million square miles). The magenta line shows the 1981 to 2010 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

June is a transition period for Arctic sea ice as 24-hour daylight reigns, and melt reaches towards the North Pole. Thus it is an appropriate time for NSIDC to transition to a new 30-year baseline period, also called a “climate normal.” The satellite record is now long enough to allow NSIDC to match current National Ocean and Atmospheric Administration (NOAA) and World Meteorological Organization (WMO) standard baselines of 1981 to 2010 for weather and climate data. Full details of the changes and the implications for NSIDC sea ice statistics are described in the NSIDC Sea Ice Index.

Average sea ice extent for June 2013 was 11.58 million square kilometers (4.47 million square miles). This was 310,000 square kilometers (120,000 square miles) below the 1981 to 2010 average (the new baseline period) of 11.89 million square kilometers (4.59 million square miles). In comparison, the 1979 to 2000 period that we previously used averaged 12.16 million square kilometers (4.70 million square miles). June 2013 was 760,000 square kilometers (293,000 square miles) above the record low June extent in 2010.

Conditions in context

graph of sea ice extent

Figure 2a. The graph above shows Arctic sea ice extent as of June 30, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

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

graph with both  baselines

Figure 2b. The graph above shows Arctic sea ice extent as of June 30, 2013, along with daily ice extent data for 2012, the record low year, and both the new and old baseline average periods. The 1981 to 2010 average is shown by a dark gray line. The gray area around this average line shows the two standard deviation range of the 1981 to 2010 average. The 1979 to 2000 average is shown by a blue line. The light purple shading around this line shows the two standard deviation range of the 1979 to 2000 average.

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

Although the rate of ice loss increased toward the end of June, overall ice has retreated more slowly this summer compared to last summer, reflecting patterns of atmospheric circulation and air temperature. Average June temperatures at the 925 mb level were average to slightly below average over most of the Arctic Ocean, contrasting with above average temperatures over most of the surrounding land. This temperature pattern is associated with unusually low sea level pressure centered near the North Pole. This type of circulation pattern is known to slow the summer retreat of ice, not just because it fosters cool conditions, but also because the pattern of cyclonic (counterclockwise) winds tends to spread the ice out. An interesting regional aspect of this pattern is that on the heels of unusually cold spring conditions, the Alaska interior experienced some days of record high temperatures during June.

 

June 2013 compared to previous years

Monthly June ice extent

Figure 3. Monthly June ice extent for 1979 to 2013 shows a decline of 3.6% per decade relative to the 1981 to 2010 average.

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

Sea ice extent declined steadily through most of the month, in sharp contrast to last year when June experienced a record fast pace of sea ice retreat. There was a speed-up in ice loss toward the end of the month. Overall, extent dropped an average of 70,300 square kilometers (27,000 square miles) per day through the month, slightly higher than the 1981 to 2010 average.

June 2013 was the 11th lowest June in the 1979 to 2013 satellite record, 760,000 square kilometers (293,000 square miles) above the record low in 2010. The monthly trend is -3.6% percent per decade relative to the 1981 to 2010 average (also -3.6% per decade relative to the old 1979 to 2000 baseline).

An Arctic pre-conditioned for rapid summer ice loss?

Figure 4. Data from NASA Operation IceBridge flights over the Arctic Ocean during March and April 2013 indicate

Figure 4. Data from NASA Operation IceBridge flights over the Arctic Ocean during March and April 2013 indicate thick ice along the Greenland coast (shown in reds), but thin ice north of Alaska (blues and greens).

Credit: National Snow and Ice Data Center/NASA Operation IceBridge
High-resolution image

Through most of June, we did not see the precipitous decline in ice extent that was observed in June 2012 and 2007 (the years with the lowest and second lowest September ice extent in the satellite record). However, the rate of ice loss did increase in late June. Ice cover this spring was very thin in parts of the Arctic, suggesting that large areas may soon start melting out completely. Much depends on whether the atmospheric circulation pattern seen in June persists through July.

NASA Operation IceBridge data collected during March and April indicated thick ice along the Greenland coast (5 meters, or 16 feet or more), but thin ice north of Alaska in the Beaufort and Chukchi seas, ranging from 1 to 1.5 meters (3 to 5 feet) in most areas and as low as 0.5 meters (approximately 2 feet) in others. These thin areas are quite likely refrozen leads, linked to the major fracturing events that occurred in the region during February and March. According to Andrew Shepherd at the University of Leeds, preliminary results from the European Space Agency CryoSat satellite suggest that the ice pack was 8% thinner in March 2013 compared to March 2012.

An ocean of small floes

figure5

Figure 5. High-resolution passive microwave data from AMSR2 on June 26, 2013 (left image) shows areas of low ice concentration near the North Pole, indicated in greens. Visible imagery from MODIS on June 27, 2013 (right image) of the inset area reveals a fractured ice surface with small floes.

Credit: University of Bremen/AMSR2; NASA/GSFC, Rapid Response
High-resolution image

High-resolution passive microwave concentration data from the Japan Aerospace Exploration Agency AMSR2 sensor, produced by the University of Bremen, indicate a highly unusual region of broken-up ice near the North Pole. Development of this low concentration ice may have been assisted by the cyclonic atmospheric pattern noted earlier.

While the AMSR2 image in Figure 5 suggests concentrations as low as 50%, visible imagery from the MODIS sensor on the NASA Aqua satellite indicate that AMSR2 is underestimating concentration, likely due to biases from surface melt.

Still, the MODIS data do confirm that the ice is highly fractured with numerous small floes. Such small floes are more easily melted from the sides and the bottom by ocean waters that are exposed to the 24-hour sunlight. It remains to be seen how many of these small floes will ultimately melt completely.

Updating the sea ice baseline

This July, NSIDC plans to change the baseline climatological period for Arctic Sea Ice News and Analysis and the Sea Ice Index, the data set we use for our sea ice analysis. We are making this change to match the comparison time frames used by other climate research.

Until now, we have used the 22-year period 1979 to 2000 when comparing current sea ice extent to past conditions. When NSIDC first began to monitor and analyze sea ice extent, a longer period was not available. Since the satellite record is now extended, we are choosing to move to a more standard 30-year reference period, from 1981 to 2010.

A 30-year period typically defines a climatology (comparsion period) and is the standard used by organizations such as the World Meteorological Organization (WMO) and the U.S. National Oceanic and Atmospheric Administration (NOAA). Thirty years is considered long enough to average out most variability from year to year, but short enough so that longer-term climate trends are not obscured.

These maxims about climate averages come from the world of weather and climate. Sea ice responds to changes in energy or heat differently from other systems on Earth. So the assumptions behind the use of 30-year averages for weather may not hold true for sea ice, particularly in light of the rapid decrease and repeated record low minimum extents in the Arctic during the past decade. However, matching the 1981 to 2010 period brings us in line with other climate research.

The monthly and daily sea ice extent images and data values will not change, but data and images that are based on the average or median will change. For example, the trend plot for sea ice extent will have a different scale, and the value of the slope, expressed as change in percent per decade, will change, because this value is relative to the average period. On the the monthly and daily extent images, the position of the average extent lines will change.

In our July analysis, we will provide more information to help readers put these changes into the larger context of changing climate and changing ice.

April on average

Arctic sea ice extent declined at an approximately average rate through April. While the Arctic Oscillation was in its negative phase for most of winter, in mid April it turned positive. This helped to bring in warm air over Eurasia, although air temperatures over the sea ice cover remain below freezing.

Overview of conditions

Figure 1. Arctic sea ice extent for April 2013 was X.XX million square kilometers (X.XX 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

Figure 1. Arctic sea ice extent for April 2013 was 14.37 million square kilometers (5.54 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

Sea ice extent averaged for the month of April 2013 was 14.37 million square kilometers (5.54 million square miles). This is 630,000 square kilometers (243,000 square miles) below the 1979 to 2000 average for the month, and is the seventh-lowest April extent in the satellite record.

In the earlier part of the satellite data record, average April extent remained above 15 million square kilometers (5.8 million square miles). Since 1989 the extent has mostly remained between 14 and 15 million square kilometers (5.4 and 5.8 million square miles). The years 1993 and 1999 were exceptions, when extent exceeded 15 million square kilometers (5.8 million square miles), as well as 2006 and 2007, when extent dropped below 14 million square kilometers (5.4 million square miles).

A large area of open water has started to form around Franz Josef Land and north of Svalbard. Polynyas are also appearing in the Kara and East Siberian seas.

The walrus and whaling season has begun in Arctic Alaska. The Study of Environmental Arctic Change (SEARCH) Sea Ice for Walrus Outlook (SIWO) is now providing weekly sea ice outlooks as a resource for Alaska Native subsistence hunters, coastal communities, and others interested in sea ice and walrus or whales. With spring sea ice conditions being thinner and less predictable than in the past due to warming in the Arctic, the sea ice outlook helps hunters plan their activities.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of April 30, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1979 to 2000 average is in dark gray. 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

Figure 2. The graph above shows Arctic sea ice extent as of April 30, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1979 to 2000 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Note: 2011 was inadvertently omitted from this graph; corrected June 17. Sea Ice Index data.

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

Through the month of April, the Arctic lost 1.5 million square kilometers of ice (444,000 square miles), which is slightly higher than the average for the month. Air temperatures at the 925 hPa level (approximately 3,000 feet above sea level) in April were 5 to 7 degrees Celsius (9 to 13 degrees Fahrenheit) higher than average in the East Siberian Sea and 3 to 5 degrees Celsius (5 to 9 degress Fahrenheit) higher than average in the Kara Sea. Temperatures were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) below average over Alaska. The dominant feature of the Arctic sea level pressure field for April 2013 was unusually high pressure over Alaska and Siberia and below average pressure over the Kara and Barents seas.  During the middle of the month, the Arctic Oscillation switched from a negative to a positive phase, with anomalously high sea level pressure over Alaska combined with below average pressure over Greenland and the North Atlantic. This brought in warm air over Eurasia, and above average air temperatures throughout the eastern Arctic.

The reductions in April ice extent this year and over the satellite record are predominantly due to reduced ice cover in the Kara and Barents seas. In contrast, ice extent continues to remain slightly above normal in the Bering Sea.

April 2013 compared to previous years

Figure 3. Monthly April ice extent for 1979 to 2013 shows a decline of -2.3% per decade.

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

Average Arctic sea ice extent for April 2013 was the seventh lowest for the month in the satellite record. Through 2013, the linear rate of decline for April ice extent is -2.3 percent per decade relative to the 1979 to 2000 average.

IceBridge Arctic flights

Figure 4. This chart shows the flight tracks of IceBridge P-3 aircraft flights over the Arctic through April 26, 2013.

Credit: NASA Operation IceBridge
High-resolution image

On 20 March 2013, NASA resumed Operation IceBridge aircraft missions over the Arctic. The IceBridge mission was initiated in 2009 to collect airborne measurements of sea ice and ice sheet thickness, to bridge the gap between NASA’s Ice, Cloud and Land Elevation Satellite (ICESat) and the upcoming ICESat-2 mission. This spring, areas not extensively covered in previous campaigns were a focus as well as flight tracks corresponding to the European CryoSat-2 satellite. Several successful flights were flown across the Beaufort and Chukchi seas in March and early April while the aircraft was stationed in Fairbanks, Alaska and Greenland’s Thule Air Base. Afterwards NASA’s P-3B aircraft was moved to Kangerlussuaq, Greenland for flights over the ice sheet. Towards the end of April, the aircraft was once again stationed in Thule, allowing additional ice sheet flights over the north central part of Greenland ice sheet and the resumption of sea ice flights over large portions of Arctic sea ice. The latter included a repeat of a 2012 flight line aimed at sampling a large region of the Canada Basin. This year’s Arctic IceBridge mission ended on 2 May, with the successful completion of ten sea ice and fifteen ice sheet flights.

Earliest satellite maps of Antarctic and Arctic sea ice

Figure 5. The National Snow and Ice Data Center scanned close to 40,000 images from Nimbus 1 satellite data to produce the earliest satellite images of Arctic and Antarctic satellite extent. The left image is a composite of the Arctic and the right image is a composite of the Antarctic.

Credit: NSIDC
High-resolution image

While the modern satellite data record for sea ice begins in late 1978, some data are available from earlier satellite programs. NSIDC has been involved in a project to map sea ice extent using visible and infrared band data from NASA’s Nimbus 1, 2, and 3 spacecraft, which were launched in 1964, 1966, and 1969. Analysis of the Nimbus data has revealed Antarctic sea ice extents that are significantly larger and smaller than seen in the modern 1979 to 2012 satellite passive microwave record. The September 1964 average ice extent for the Antarctic is 19.7 ± 0.3 million square kilometers (7.6 million ± 0.1 square miles. This is more than 250,000 square kilometers (97,000 square miles) greater than the 19.44 million square kilometers (7.51 million square miles) seen in 2012, the record maximum in the modern data record. However, in August 1966 the maximum sea ice extent fell to 15.9 ± 0.3 million square kilometers (6.1 ± 0.1 million square miles). This is more than 1.5 million square kilometers (579,000 square miles) below the passive microwave record low September of 17.5 million square kilometers (6.76 million square miles) set in 1986.

The early satellite data also reveal that September sea ice extent in the Arctic was broadly similar to the 1979 to 2000 average, at 6.9 million square kilometers (2.7 million square miles) versus the average of 7.04 million square kilometers (2.72 million square miles).

In memoriam

We dedicate this post to Dr. Katharine Giles, who was tragically killed cycling to work on 8 April 2013. Together with Dr. Laxon, Katherine Giles worked to retrieve sea ice thickness from satellite radar altimeter data. In 2007 she was the first to show that this data could also be used to show how winds affect the newly exposed Arctic Ocean. Since Dr. Laxon’s death earlier this year, Katharine worked hard to continue his legacy and supervise his students. We have lost yet another talented scientist and a great friend.

Reference

Meier, W. N., D. Gallaher, and G. C. Campbell. 2013. New estimates of Arctic and Antarctic sea ice extent during September 1964 from recovered Nimbus I satellite imagery. The Cryosphere, 7, 699–705, doi:10.5194/tc-7-699-2013.

A fractured winter

Arctic sea ice is nearing its winter maximum and will soon begin its seasonal decline. Ice extent remains below average, in part a result of the persistence of the negative phase of the Arctic Oscillation that has kept winter temperatures warmer than average. The Antarctic passed its summer minimum ice extent, reaching the second highest level in the satellite record at this time of year, primarily due to continued higher-than-average ice in the Weddell Sea.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2013 was 14.66 million square kilometers (5.66 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

Average sea ice extent for February 2013 was 14.66 million square kilometers (5.66 million square miles). This is 980,000 square kilometers (378,000 square miles) below the 1979 to 2000 average for the month, and is the seventh-lowest February extent in the satellite record. Since 2004, the February average extent has remained below 15 million square kilometers (5.79 million square miles) every year except 2008. Prior to 2004, February average extent had never been less than 15 million square kilometers. Ice extent remains slightly below average everywhere except the Bering Sea.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 3, 2013, along with daily ice extent data for the 2012, the record low year. 2013 is shown in blue, and 2012 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

Through the month of February, the Arctic gained 766,000 square kilometers of ice (296,000 square miles), which is 38% higher than the 1979 to 2000 average for the month. Air temperatures at the 925 hPa level were 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) higher than average across the Atlantic sector of the Arctic, especially near Iceland and in Baffin Bay. Temperatures were lower than average by 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) north of Greenland and the Canadian Archipelago, and in the Beaufort, Chukchi and East Siberian seas, linked to anomalously low sea level pressure over Alaska and Canada. The dominant feature of Arctic sea level pressure for February 2013 was unusually high pressure over the East Greenland and Barents seas, consistent with a predominantly negative phase of the Arctic Oscillation.

February 2013 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2012 shows a decline of -2.9% per decade.

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

Average Arctic sea ice extent for February 2013 was the seventh lowest for the month in the satellite record. Through 2013, the linear rate of decline for February ice extent is -2.9% per decade relative to the 1979 to 2000 average. Although the relative reduction in winter sea ice extent remains small compared to reductions in summer, the linear trend represents an overall reduction of more than 1.57 million square kilometers (606,000 square miles) from 1979 to 2013.

Persistence of the negative phase of the Arctic Oscillation

Figure 4. These ice motion images for November 2012 (left) and December 2012 (right) show strong export of ice through the Fram Strait in November, while in December ice export through the Fram was about average.

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

As discussed in the January and February posts, sea level pressure in the Arctic has remained higher than average, resulting in persistence of the negative phase of the Arctic Oscillation (AO). During the negative phase of the Arctic Oscillation, enhanced poleward transport of warm air tends to keep temperatures in the Arctic above average. At the same time, the negative phase of the Arctic Oscillation allows for more cold Arctic air to intrude or mix with air at lower latitudes. These cold air outbreaks can result in low temperatures and increased storminess in mid latitudes.

The Arctic Oscillation also impacts sea ice movement in the Arctic. The negative phase of the Arctic Oscillation is linked to an increase in the strength of the Beaufort Gyre and reduced outflow of ice through Fram Strait. A negative AO used to help promote ice survival through summer by strengthening the Beaufort Gyre and thereby increasing the distribution of old, thick ice along coastal Alaska and Siberia. However, the location and strength of positive sea level pressure anomalies has varied throughout winter, with varied impacts on ice motion.

For example, during November (weak AO index of -0.111) positive sea level pressure anomalies were centered over the Bering Sea and Alaska, resulting in strong ice motion from the central Arctic towards coastal Canada and north of Greenland outwards towards Fram Strait. In December, the strong negative AO index of -1.749 was reflected in positive sea level pressure anomalies centered over the Kara and Barents seas, enhancing ice motion from the southern Beaufort into the Chukchi sea and out towards the Bering Sea. Export of ice out of Fram Strait was about average. Similar variations in positive sea level pressure anomalies have continued, with the largest positive anomalies over the central Arctic in January, and over the Barents Sea in February.

This pattern is similar to that observed during the extreme negative Arctic Oscillation year of 2009/2010, when old ice was transported into the southern Beaufort and Chukchi seas where it then melted out during summer 2010, further depleting the Arctic of its store of old, thick ice.

Ice fracture

Figure 5. In this series of images from February 13 to March 2, from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS), a large crack expands in the sea ice near the coasts of Canada and Alaska. Black areas indicate where the satellite instrument did not collect data due to lack of sunlight. The dark area decreases as the sun rises in the Arctic. Rapid Response imagery was obtained from the NASA Land Atmosphere Near-real time Capability for EOS (LANCE) system.

Credit: NASA LANCE/National Snow and Ice Data Center
View the image series

During the last couple of weeks of February, a broad area of sea ice has fractured off the coast of Alaska and Canada, extending from Ellesmere Island in the Canadian Arctic to Barrow, Alaska. This fracturing event appears to be related to a series of storms that moved across central Alaska starting on February 10, 2013, causing intense easterly winds along the coast and strong off-shore ice motion.* The large area of fractured ice is located in predominantly first-year ice, which is thinner and easier to fracture than thick, multiyear ice. Similar patterns were observed in early 2011 and 2008, but the 2013 fracturing is quite extensive.  The animation (Figure 5) shows the progress of the fracturing, and the general strong rotation of the Beaufort Gyre ice motion pattern during late February. (See also this animation of the fracture from the AVHRR instrument, posted on the Arctic Sea Ice Blog.)

* Note: We originally attributed the fracturing event to a storm that passed over the North Pole, and stated “This fracturing event appears to be related to a storm that passed over the North Pole on February 8, 2013, creating strong off-shore ice motion.” We corrected this sentence after reexamining weather charts. The updated version now reads, “This fracturing event appears to be related to a series of storms that moved across central Alaska starting on February 10, 2013, causing intense easterly winds along the coast and strong off-shore ice motion.”

Antarctic sea ice extent continues above average

Figure 6. Antarctic sea ice extent for February 2013 was 3.83 million square kilometers (1.48 million square miles). The magenta line shows the 1979 to 2000 median extent for that month. The black cross indicates the geographic South Pole. Sea Ice Index data. About the data

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

The Antarctic sea ice minimum extent appears to have passed, on February 20. Ice was quite extensive throughout the austral summer period. Monthly average sea ice extent for February 2013 was 3.83 million square kilometers (1.48 million square miles) and minimum daily sea ice extent for the Antarctic region was 3.68 million square kilometers (1.42 million square miles) on February 20. Unusual circulation patterns, likely resulting from higher-than-average pressure in the Bellingshausen Sea, pushed sea ice in the northwestern Weddell Sea far to the north, as we mentioned in our February post. NASA’s Earth Observatory posted this image of ice in the Weddell Sea as Image of the Day for March 1st, 2013. Extent was also well above average for the Ross Sea region relative to the entire 1979 to 2013 satellite record.

The Odden

Figure 7. This image shows sea ice cover in early May, 2012 in the east Greenland Sea. Sea ice extent is provided at 4 kilometer resolution by the NSIDC/NIC multi-sensor MASIE product and sea ice concentration (varying from 0 to 1) at 25 kilometer resolution by NSIDC’s Near-Real Time Passive Microwave product. The red dot shows the estimated position of an ARGO profiling float deployed as part of a NASA-sponsored project led by Michael Steele  and Patricia Matrai. This float is capable of storing ocean data while under the ice pack, which are then received via satellite when the ice recedes. Ongoing analysis of these data indicates that cold, fresh surface water lies just under the ice extension along the Jan Mayen Ridge, a signature of Arctic waters.

Credit: M. Steele, University of Washington and P. Matrai, Bigelow Lab/National Snow and Ice Data Center
High-resolution image

Within the East Greenland Sea, an ice tongue about 1,300 kilometers (807 miles) in length, referred to as “The Odden” (Norwegian word for headland), would regularly form during winter months eastwards from the main East Greenland ice edge. The Odden would form in winter because of an eastward flow of very cold ocean waters in the Jan Mayen current and may have played an important role in winter ocean convection as new ice would form. It would form as early as December and as late as April and was present during the 1980s, a few times in the 1990s, and very rarely since 2000. While the Odden rarely formed in last two decades, there is frequently a small extension of ice along the Jan Mayen Ridge, which may indicate that eastward flow of cold ocean water is still occurring.

Winds and warmth influence freeze up

For the Arctic as a whole, ice growth for November was faster than average. However, the Kara and Barents seas remained largely ice free, contributing to above-average air temperatures in these regions.

Overview of conditions

Figure 1. Arctic sea ice extent for November 2012 was 9.9 million square kilometers (3.8 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

November average sea ice extent was 9.93 million square kilometers (3.83 million square miles). This is 1.38 million square kilometers (533,000 square miles) below the 1979 to 2000 average for the month and is the third lowest November extent in the satellite record.

By the end of the month, the central Arctic Ocean had almost completely frozen over. However, the Barents and Kara seas remained largely ice free. Extent remained below normal in the Baffin Bay and Hudson Bay, but ice extent in the Bering Sea by the end of the month was greater than average, continuing a pattern seen in recent years. Extent in the Bering Sea was at record high levels last winter.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of December 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 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

Extent can increase quickly during November because there is little solar energy and the ocean is rapidly losing the heat that it gained in summer. For the Arctic as a whole, ice growth for November 2012 was faster than average, increasing at an average rate of 98,600 square kilometers (38,100 square miles) per day. After remaining lower than levels observed in 2007 for most of the month, by November 30 ice extent matched or exceeded extent seen in 2007, 2006, and 2010.

November 2012 compared to previous years

Figure 3. Monthly November ice extent for 1979 to 2012 shows a decline of -4.8% per decade.

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

Average sea ice extent for November 2012 was the third lowest in the satellite record. This marks only the third year in the satellite record that November extent was below 10 million square kilometers (3.86 million square miles). Through 2012, the linear rate of decline for November Arctic ice extent is -4.8% per decade relative to the 1979 to 2000 average.

Air temperatures remain high over ice-free areas

Figure 4. This image shows air temperature anomalies at the 925 hPa level averaged for November 2012, compared to averages over the period 1981 to 2010. Temperatures were above average over the East Siberian, Barents, and Kara seas.

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

November air temperatures at the 925 hPa level (approximately 3,000 feet) were above average over most of the Arctic Ocean. Notably, temperatures in the Barents and Kara seas were up to 6 degrees Celsius (11 degrees Fahrenheit) higher than average. This reflects in part the lingering open water in the regions, allowing strong upward transfers of heat from the ocean to the atmosphere. Unusually strong winds from the south contributed to the warmth and also helped keep the region ice free.

More striking were the unusually warm conditions over the ice-covered East Siberian Sea, where temperatures were 6 degrees Celsius (11 degrees Fahrenheit) above average. This appears to be due to persistent high pressure over the Bering Strait. Southerly winds on the west side of the high-pressure zone brought warm air into the East Siberian region. Colder, northerly winds on the east side of the high-pressure zone help explain the higher-than-average extent in the Bering Sea.

Arctic rapidly gaining winter ice

Ice extent doubled in October. The rate of increase since the 2012 minimum was near record, resulting in an October monthly extent 230,000 square kilometers (88,800 square miles) greater than the previous low for the month, which occurred in 2007. Despite this rapid growth, ice extent remains far below normal as we begin November.

Overview of conditions

Figure 1. Arctic sea ice extent for October 2012 was 7.0 million square kilometers (2.7 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

Average ice extent for October was 7.00 million square kilometers (2.70 million square miles). This is the second lowest in the satellite record, 230,000 square kilometers (88,800 square miles) above the 2007 record for the month. However, it is 2.29 million square kilometers (884,000 square miles) below the 1979 to 2000 average. The East Siberian, Chukchi, and Laptev seas have substantially frozen up. Large areas of the southern Beaufort, Barents and Kara seas remain ice free.

As of November 4, sea ice extent stood at 8.22 million square kilometers (3.17 million square miles). This is 520,000 square kilometers (201,000 square miles) below the extent observed in 2007 on the same date, and ice extent remains 2.04 million square kilometers (788,000 million square miles) below the 1979 to 2000 average for this date.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of October 31, 2012, along with daily ice extent data for 2011 and for the previous record year, 2007. 2012 is in blue, 2011 is orange, and 2007 is shown 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

After the record minimum ice extent on September 16 and through October 31, the Arctic gained 4.19 million square kilometers (1.62 million square miles) of ice. Ice extent doubled during the month of October. The average rate of ice growth for October was 121,000 square kilometers (46,700 square miles) per day, causing the extent to temporarily climb above the extent observed during October 2007 for a period. This led to a monthly average extent slightly above levels in 2007, the previous record low October. Slower ice growth during the last few days of the month then brought extent below 2007 levels.

On October 20, ice extent went above 6.0 million square kilometers (2.3 million square miles) for the first time since August 6.

October 2012 compared to previous years

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

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

Due to the rapid ice growth during October, Arctic sea ice extent for October 2012 was the second lowest in the satellite record, above 2007. Through 2012, the linear rate of decline for October Arctic ice extent over the satellite record is -7.1% per decade.

Asymmetric ice growth and temperatures

Figure 4. This graph shows rates of ice growth in the Arctic since the September 16, 2012 minimum extent and through October 31. Growth has been particularly rapid in the East Siberian and Laptev seas.

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

While overall the Arctic rapidly gained ice throughout October, the rate of ice growth was not the same everywhere. Ice growth in the Beaufort and Chukchi seas averaged about 8,500 square kilometers (3,300 square miles) per day and large areas still remain ice free. In the eastern Arctic there was rapid ice growth in the East Siberian and Laptev seas exceeding, respectively, 28,000 and 18,000 square kilometers per day (11,000 and 7,000 square miles per day). As a result, most of the region is now completely frozen over. The slowest rates of ice growth have occurred in the Kara Sea (less than 3,000 square kilometers, or 1,000 square miles per day). In large part because of extensive open water in the Kara and Barents seas, air temperatures for October in this area at the 925 hPa level (about 3,000 feet above the surface) were 3 to 4 degrees Celsius (5 to 7 degrees Fahrenheit) above average, with unusual warmth becoming more pronounced near the surface. October air temperatures over the ice-free southern Beaufort Sea were also far above average.

Ice extent and bathymetry: The floor’s the limit

Figure 5. This image provides a snapshot of how ocean depth in the Arctic influences sea ice extent. Sea ice cover for August 28, 2012 is shown in semi-transparent white; ocean depths are indicated in blues, with deeper blues indicating greater depth. Sea ice data are from the Multisensor Analyzed Sea Ice Extent (MASIE), which provides more accurate ice edge position.

Credit: National Snow and Ice Data Center courtesy Jamie Morison/Applied Physics Laboratory, University of Washington
High-resolution image

Research by our colleagues Jamie Morison at the University of Washington Seattle and NASA scientist Son Nghiem suggests that bathymetry (sea floor topography) plays an important role in Arctic sea ice formation and extent by controlling the distribution and mixing of warm and cold waters. At its seasonal minimum extent, the ice edge mainly corresponds to the deep-water/shallow-water boundary (approximately 500-meter depth), suggesting that the ocean floor exerts a dominant control on the ice edge position. However, in some cases, ice survives in the shallower continental shelf regions due to water circulation patterns. For example, the shelf area of the East Greenland Sea is almost always covered with sea ice because the southward-flowing cold Arctic surface water helps to limit melt.

In contrast, ice disappears in shallow areas like the Barents and Chukchi seas that are subject to warm ocean waters and river runoff. River runoff and ice melting have also contributed to changes in the amount and distribution of fresh water in the Arctic.

Further reading

Morison, J., R. Kwok, C. Peralta-Ferriz, M. Alkire, I. Rigor, R. Andersen, and M. Steele. 2012. Changing Arctic Ocean freshwater pathways. Nature 481, 66–70 (05 January 2012), doi:10.1038/nature10705.

Nghiem, S.V., P. Clemente-Colón, I.G. Rigor, D.K. Hall, and G. Neumann. 2012. Seafloor control on sea ice. Deep Sea Research Part II: Topical Studies in Oceanography, Volumes 77–80, 15 November 2012, pp. 52-61, ISSN 0967-0645, doi:10.1016/j.dsr2.2012.04.004.

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.