Thicker on top, more down under

Arctic sea ice extent remained lower than average in January, and just within two standard deviations of the long-term average. Arctic temperatures remained above average, even as cold winter air embraced North America. The retention of more sea ice in September 2013 has increased the overall thickness and volume of the ice pack compared to recent years. Antarctic sea ice remains significantly more extensive than average.

Overview of conditions

sea ice extent image

Figure 1. Arctic sea ice extent for January 2014 was 13.73 million square kilometers (5.30 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

Arctic sea ice extent continued to track below average during January, remaining just within two standard deviations of the long-term average. The average extent for January was 13.73 million square kilometers (5.30 million square miles). This is 800,000 square kilometers (309,000 square miles) less than the 1981 to 2010 average, and 160,000 square kilometers (61,800 square miles) above the previous record low for the month of January set in 2011. Sea ice extent remains below average in the Barents Sea, the Sea of Okhotsk, and the Bering Sea. While recent winters have seen more extensive sea ice in the Bering Sea, this is the first January since 2005 for which below average conditions have been observed there. Extent is close to average in Baffin Bay, the Labrador Sea, and the Gulf of St. Lawrence.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of February 3, 2014, along with daily ice extent data for the previous four years. 2013-2014 is shown in blue, 2012-2013 in brown, and 2011-2012 in green, 2010-2011 in light purple, and 2009-2010 in dark blue. 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 February 3, 2014, along with daily ice extent data for the previous four years. 2013-2014 is shown in blue, 2012-2013 in brown, and 2011-2012 in green, 2010-2011 in orange, and 2009-2010 in light 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

Air temperatures for January were higher than average over most of the Arctic Ocean, helping to keep daily ice growth rates at near average values. Air temperatures at the 925 hPa level were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average over the central Arctic Ocean and 7 to 8 degrees Celsius (13 to 14 degrees Fahrenheit) higher than average over the North Atlantic region, Greenland, Baffin Bay, and Alaska. Cooler than average conditions prevailed over Siberia (−4 to −8 degrees Celsius, or −7 to −14 degrees Fahrenheit) and the southern Beaufort Sea (−2 to −4 degrees Celsius, or −4 to −7 degrees Fahrenheit). This temperature pattern is consistent with a negative Arctic Oscillation pattern, which dominated the month of January. This is in contrast to the positive Arctic Oscillation pattern, which dominated December 2013, leading to anomalously warm conditions over Siberia and Eurasia and colder than average conditions over Greenland, Alaska, and Canada.

January 2014 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 January ice extent for 1979 to 2014 shows a decline of 3.2% per decade.

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

Including 2014, sea ice extent for January is declining at a rate of 3.2% per decade relative to the 1981 to 2012 average, or at a rate of 47,800 square kilometers (18,500 square miles) per year. January 2014 is the fourth lowest extent in the satellite record, behind 2005, 2006, and the record low January 2011.

CryoSat suggests thicker ice than in recent years

ice thickness comparison

Figure 4. This series of images from the European Space Agency CryoSat satellite compares Arctic sea ice thickness for the last four Octobers. Thinner ice is indicated in blues and greens; thicker ice is show in yellows and reds.

Credit: National Snow and Ice Data Center/CryoSat, courtesy Rachel Tilling/University College London.
High-resolution image

While satellite observations have shown a decline in Arctic Ocean sea ice extent since the late 1970s, sea ice is highly mobile, and a decrease in extent does not necessarily imply a corresponding decrease in ice volume. Observations of thickness (which allows  calculation of volume) have been limited, making it difficult to estimate sea ice volume trends. The European Space Agency (ESA) CryoSat satellite was launched in October 2010 and has enabled estimates of sea ice thickness and volume for the last three years.

Preliminary measurements from CryoSat show that the volume of Arctic sea ice in autumn 2013 was about 50% higher than in the autumn of 2012. In October 2013, CryoSat measured approximately 9,000 cubic kilometers (approximately 2,200 cubic miles) of sea ice compared to 6,000 cubic kilometers (approximately 1,400 cubic miles) in October 2012. About 90% of the increase in volume between the two years is due to the retention of thick, multiyear ice around Northern Greenland and the Canadian Archipelago. However, this apparent recovery in ice volume should be considered in a long-term context. It is estimated that in the early 1980s, October ice volume was around 20,000 cubic kilometers (approximately 4,800 cubic miles), meaning that ice volume in October 2013 still ranks among the lowest of the past 30 years. CryoSat will continue to monitor sea ice through the current growth season, and the data will reveal the effect of this past autumn’s increase on ice volume at the end of winter.

New insight on the expanding Antarctic sea ice extent

Figure 5. This image of Antarctic sea ice concentration trends shows... Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5b. This image of Antarctic sea ice concentration anomaly trends for January 2014 suggests increases in sea ice in the western Ross and Weddell Seas (oranges and reds), and declines in the Amundsen and Bellingshausen Seas (blues). Sea Ice Index data. About the data

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

Figure 5a. The graph above shows Antarctic sea ice extent as of February 3, 2014, along with daily ice extent data for the previous four years. 2013-2014 is shown in light blue, 2012-2013 in brown, and 2011-2012 in orange, 2010-2011 in light purple, and 2009-2010 in dark blue. 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 5a. The graph above shows Antarctic sea ice extent as of February 3, 2014, along with daily ice extent data for the previous four years. 2013-2014 is shown in light blue, 2012-2013 in brown, and 2011-2012 in green, 2010-2011 in orange, and 2009-2010 in light 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

Antarctic sea ice extent continues to track very high in January, reaching the second-highest monthly extent in the 36-year satellite monitoring record. New monthly extent records were set for each month between August and November, and December was tied for the record (within the limits of the precision). Trend maps of sea ice concentration (Figure 5b), however, reveal that the increase is not uniform around the Antarctic continent, nor is the strength of the monthly trends (in percent increase per decade) as great as those for the Arctic, in either winter or summer. While sea ice has increased in the western Ross Sea and the Weddell Sea, it has declined in the Amundsen and Bellingshausen seas.

Most efforts to explain these regional patterns of sea ice variability and trends have focused on variations in patterns of atmospheric circulation around the Antarctic continent, and how these patterns are driven by variations in sea surface temperature in the tropical Pacific Ocean (such as those associated with El Niño and La Niña). While these patterns show large variations seasonally and year-to-year, the longer-term trend in Pacific sea surface temperature is small, and does not appear to explain the long-term overall sea ice increases that have been observed. A new study published in Nature by Li and colleagues may provide the missing link. They argue that changes in the north Atlantic and tropical Atlantic sea surface temperatures may be driving long-term, subtle trends in Southern Ocean winds that would explain the regional trends in sea ice cover. Their results link higher Atlantic sea surface temperatures since 1979 to reduced sea level pressure in the Amundsen Sea, contributing to the resulting dipole-like sea ice pattern between the northern Ross Sea (where sea ice is increasing) and the northern Bellingshausen Seas (where it is decreasing).

 

Further reading

Laxon, S. and others, 2013. CryoSat-2 estimates of Arctic sea ice thickness and volume, Geophys. Res. Lett., doi:10.1002/grl.50193.

Li, X., D.M. Holland, E.P. Gerber and C. Yoo, 2014. Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice, Nature, 505, doi:10.1038/nature12945.

A better year for the cryosphere

This summer, Arctic sea ice loss was held in check by relatively cool and stormy conditions. As a result, 2013 saw substantially more ice at summer’s end, compared to last year’s record low extent. The Greenland Ice Sheet also showed less extensive surface melt than in 2012. Meanwhile, in the Antarctic, sea ice reached the highest extent recorded in the satellite record.

Overview of conditions

map of sea ice extent

Figure 1. Arctic sea ice extent for September 2013 was 5.35 million square kilometers (2.07 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

Arctic sea ice extent reached its annual minimum on September 13. After the minimum, extent remained largely unchanged for much of the middle of September, but increased rapidly toward the end of the month with the onset of strong autumn cooling.

Arctic sea ice extent averaged for September 2013 was 5.35 million square kilometers (2.07 million square miles). This was 1.17 million square kilometers (452,000 square miles) below the 1981 to 2010 average extent. September 2013 ice extent was 1.72 million square kilometers (664,000 square miles) higher than the previous record low for the month that occurred in 2012.

Conditions in context

graph of sea ice extent

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

The rate of ice loss varied through the summer. Both May 2012 and May 2013 saw near average extents and rates of decline. This year, the rate of ice loss sped up in late June and early July, then settled into a near-average rate of decline, with extent approximately 500,000 square kilometers (193,000 square miles) greater than the same time in 2012. Ice loss then slowed down in August to only a little faster than average rates of loss for that time of year. In comparison, during 2012, the rate of loss accelerated in early June and through July, then accelerated even more in August to produce a new record low extent in September 2012.

Overall, 10.03 million square kilometers (3.87 million square miles) of ice were lost between the 2013 maximum and minimum extents. This was the seventh summer that more than 10 million square kilometers of ice extent were lost; all but one of the seven (the summer of 1990) have occurred since 2007.

September 2013 compared to previous years

Figure 3. Monthly September ice extent for 1979 to 2013 shows a decline of X.X% per decade.||Credit: National Snow and Ice Data Center |High-resolution image

Figure 3. Monthly September ice extent for 1979 to 2013 shows a decline of 13.7% per decade.

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

September average sea ice extent for 2013 was the sixth lowest in the satellite record. The 2012 September extent was 32% lower than this year’s extent, while the 1981 to 2010 average was 22% higher than this year’s extent. Through 2013, the September linear rate of decline is 13.7% per decade relative to the 1981 to 2010 average.

What a difference a year makes

Figure 4. These images show June to August sea level pressures compared to the 1981 to 2010 average, for 2012 (left) and 2013 (right). In 2013, low pressures prevailed over the central Arctic Ocean and Greenland. Blues and purples indicate low pressure, while greens, yellows, and reds indicate high pressures. ||Credit: National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Division|High-resolution image

Figure 4. These images show June to August sea level pressures compared to the 1981 to 2010 average, for 2012 (left) and 2013 (right). In 2013, low pressures prevailed over the central Arctic Ocean and Greenland. Blues and purples indicate low pressures, while greens, yellows, and reds indicate high pressures.

Credit: National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Division
High-resolution image

Contrasting weather conditions were a significant factor in this year’s higher sea ice extent and lower Greenland Ice Sheet melt intensity, compared to last year. This summer saw air temperatures at the 925 hPa level that were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) lower than last summer. It was also a cool summer compared to recent years over much of the Arctic Ocean, and even cooler than the 1981 to 2010 average in some regions, particularly north of Greenland.

While 2012 and 2013 extents were similar through May, weather patterns from June to August helped retain more ice. Last summer was marked by lower than average pressure over the Eurasian side of the Arctic and higher than average pressure over Greenland. This resulted in a dipole-like wind pattern that favored ice transport across the ocean and the import of heat from southern latitudes along the Eurasian side of the Arctic. In contrast, this summer was characterized by unusually low pressure over much of the Arctic Ocean, which limited heat import from the south and brought more extensive cloud cover, keeping temperatures lower. In addition, the winds associated with the low pressure caused the ice cover to spread out and cover a larger area.

Over land, the cool spring resulted in greater than average March and April snow cover for the Northern Hemisphere. However, as in recent years, the snow melted rapidly, and by May, snow cover was at near record lows. Cooler weather conditions also limited surface melt on the Greenland Ice Sheet, which was still greater than the 1981 to 2010 average, but not near the record set in 2012 (see our Greenland Ice Sheet Today post for more details).

Ice thickness and age

Figure 5. These images from March 2013 (top) and September 2013 (bottom) show the changes in multiyear ice between this year's sea ice maximum and minimum extents. In contrast to 2012, the record low extent year, multiyear ice tended to stay put, rather than being circulated around, which can expose it to warmer currents and winds that increase melt. 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: NSIDC courtesy Jim Maslanik, University of Colorado Boulder and Walt Meier, NASA Goddard Cryospheric Sciences |High-resolution image

Figure 5. These images from March 2013 (top) and September 2013 (bottom) show the changes in multiyear ice between this year’s sea ice maximum and minimum extents. In contrast to 2012, the record low extent year, multiyear ice tended to stay put, rather than being circulated around, which can expose it to warmer currents and winds that increase melt. 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: NSIDC courtesy Mark Tschudi, University of Colorado Boulder and Walt Meier, NASA Goddard Cryospheric Sciences
High-resolution image

The pattern of ice thickness for the summer of 2013 is similar to what has been seen in recent years. According to data from the European Space Agency CryoSat-2 radar altimeter, the spring melt season started with an Arctic ice cover thinner than in any recent year. This corroborates thickness information inferred from a calculation of ice age that showed first-year ice, which is thinner and more vulnerable to melt, over a significant part of the Arctic Ocean as the melt season started (see our earlier post). Older, thicker ice remained in a region roughly between the North Pole and the Canadian Archipelago and the Greenland coast.

In recent summers, there has been considerable transport of older ice into the Beaufort and Chukchi seas, where it has been broken up and exposed to a warm ocean and high air temperatures. This has been a major factor in the loss of multiyear ice over the last decade. This year was notably different. Because this year’s wind pattern was different than 2012, the multiyear ice largely remained in a compact area along the Canadian Archipelago and did not circulate into the Beaufort and Chukchi seas. The cooler conditions this summer also helped preserve more of the first-year ice through the summer.

The first-year ice that survived the summer, now defined as second-year ice, will thicken through autumn and winter. However, it would take several more cool years in a row to build the ice cover back to the state it was in during the 1980s, which consisted of a larger proportion of thicker, multiyear ice that was more resistant to melt. While ice in the Arctic will thicken through this autumn and winter, winds may also transport some of the thicker ice out of the Arctic Ocean and into the North Atlantic.

Another record high in the Antarctic

September Antarctic sea ice image

Figure 6. Antarctic sea ice extent for September 2013 was 19.77 million square kilometers (7.63 million square miles). The magenta line shows the 1981 to 2010 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

Antarctic sea ice extent reached 19.47 million square kilometers (7.52 million square miles) on September 22, a record high maximum extent relative to the satellite record, and slightly above the previous record high set last year. This year’s maximum extent was 3.6% higher than the 1981 to 2010 average Antarctic maximum, representing an ice edge that is 35 kilometers (approximately 22 miles) further north on average. Overall, Antarctic September sea ice extent is increasing at 1.1% per decade relative to the 1981 to 2010 average. This increase is likely due to a combination of factors, including winds and ocean circulation. A recent paper by our colleague Jinlun Zhang at the University of Washington concludes that changes in winds are resulting in both more compaction within the ice pack and more ridging, causing a thickening of the pack and making it more resistant to summer melt.

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 1981-2010 avg.)
in millions of square kilometers in millions of square miles
2007 4.30 1.66 -11.0
2008 4.73 1.83 -11.0
2009 5.36 2.08 -12.0
2010 4.90 1.90 -12.4
2011 4.63 1.79 -12.0
2012 3.63 1.40 -14.0
2013 5.35 2.07 -13.7
1979 to 2000 average 7.04 2.72
1981 to 2010 average 6.52 2.52

Note that the dates and extents of the minimums have been re-calculated from what we posted in previous years; see our Frequently Asked Questions for more information.

Reference

Zhang, J. In press. Modeling the impact of wind intensification on Antarctic sea ice volume. J. Climate, doi:10.1175/JCLI-D-12-00139.1.

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
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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.