Overview of conditions

Figure 1. Arctic sea ice extent for March 2014 was 14.80 million square kilometers (5.70 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 for March 2014 averaged 14.80 million square kilometers (5.70 million square miles). This is 730,000 square kilometers (282,000 square miles) below the 1981 to 2010 average extent, and 330,000 square kilometers (127,000 square miles) above the record March monthly low, which happened in 2006. Extent remains slightly below average in the Barents Sea and the Sea of Okhotsk, but is at near-average levels elsewhere. Extent hovered around two standard deviations below the long-term average through February and early March. The middle of March by contrast saw a period of fairly rapid expansion, temporarily bringing extent to within about one standard deviation of the long-term average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of April 1, 2014, along with daily ice extent data for four previous years. 2013 to 2014 is shown in blue, 2012 to 2013 in green, 2011 to 2012 in orange, 2010 to 2011 in brown, and 2009 to 2010 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

In the Arctic, the maximum extent for the year is reached on average around March 9. However, the timing varies considerably from year to year. This winter the ice cover continued to expand until March 21, reaching 14.91 million square kilometers (5.76 million square miles), making it both the fifth lowest maximum and the fifth latest timing of the maximum since 1979. The latest timing of the maximum extent was on March 31, 2010 and the lowest maximum extent occurred in 2011 (14.63 million square kilometers or 5.65 million square miles).

The late-season surge in extent came as the Arctic Oscillation turned strongly positive the second week of March. This was associated with unusually low sea level pressure in the eastern Arctic and the northern North Atlantic. The pattern of surface winds helped to spread out the ice pack in the Barents Sea where the ice cover had been anomalously low all winter. Northeasterly winds also helped push the ice pack southwards in the Bering Sea, another site of persistently low extent earlier in the 2013 to 2014 Arctic winter. Air temperatures however remained unusually high throughout the Arctic during the second half of March, at 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) above the 1981 to 2010 average.

March 2014 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2014 shows a decline of 2.6% per decade relative to the 1981 to 2010 average.

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

Average ice extent for March 2014 was the fifth lowest for the month in the satellite record. Through 2014, the linear rate of decline for March ice extent is 2.6% per decade relative to the 1981 to 2010 average.

An increase in multiyear ice

Figure 4. Imagery from the European Advanced Scatterometer (ASCAT) show the distribution of multiyear ice compared to first year ice for March 28, 2013 (yellow line) and March 2, 2014 (blue line).

Credit: Advanced Scatterometer imagery courtesy NOAA NESDIS, analysis courtesy T. Wohlleben, Canadian Ice Service
High-resolution image

The extent of multiyear ice within the Arctic Ocean is distinctly greater than it was at the beginning of last winter. During the summer of 2013, a larger fraction of first-year ice survived compared to recent years. This ice has now become second-year ice. Additionally, the predominant recirculation of the multiyear ice pack within the Beaufort Gyre this winter and a reduced transport of multiyear ice through Fram Strait maintained the multiyear ice extent throughout the winter.

In Figure 4, Advanced Scatterometer (ASCAT) imagery reveals the distribution of multiyear ice compared to first year ice for March 28, 2013 (yellow line) and March 2, 2014 (blue line). The ASCAT sensor measures the radar–frequency reflection brightness of the sea ice at a few kilometers resolution. Sea ice radar reflectivity is sensitive to the roughness of the ice and the presence of saltwater droplets within newer ice (and, later in the season, the presence of surface melt). Thus older and more deformed multiyear ice appears white or light grey (more reflection), whereas younger, first-year ice looks dark grey and/or black.

Ice age tracking confirms large increase in multiyear ice

Figure 5. The map at top shows the ages of ice in the Arctic at the beginning of March 2014; the bottom graph shows how the percentage of ice in each age group has changed from 1983 to 2014 .

Credit: NSIDC, Courtesy M. Tschudi, University of Colorado
High-resolution image

Satellite data on ice age reveal that multiyear ice within the Arctic basin increased from 2.25 to 3.17 million square kilometers (869,000 to 1,220,000 square miles) between the end of February in 2013 and 2014. This winter the multiyear ice makes up 43% of the icepack compared to only 30% in 2013. While this is a large increase, and may portend a more extensive September ice cover this year compared to last year, the fraction of the Arctic Ocean consisting of multiyear ice remains less than that at the beginning of the 2007 melt season (46%) when a large amount of the multiyear ice melted. The percentage of the Arctic Ocean consisting of ice at least five years or older remains at only 7%, half of what it was in February 2007. Moreover, a large area of the multiyear ice has drifted to the southern Beaufort Sea and East Siberian Sea (north of Alaska and the Lena River delta), where warm conditions are likely to exist later in the year.

Summer ice extent remains hard to predict

Figure 6. Median (red) and interquartile range (gray shading) of sea ice predictions submitted to the July SEARCH SIO each year compared with September mean sea ice extent (green).

Credit: Stroeve et al.
High-resolution image

There is a growing need for reliable sea ice predictions. An effort to gather and summarize seasonal sea ice predictions made by researchers and prediction centers began in 2008. The project, known as the SEARCH Sea Ice Outlook, has collected more than 300 predictions of summer month ice extent. A new study published in Geophysical Research Letters by researchers at NSIDC, University of New Hampshire, and University of Washington reveal a large range in predictive skill. The study found that forecasts are quite accurate when sea ice conditions are close to the downward trend that has been observed in Arctic sea ice for the last 30 years. However, forecasts are not so accurate when sea ice conditions are unusually higher or lower compared to this trend. Results from the study also suggest that while ice conditions during the previous winter are an important predictor (such as the fraction of first-year versus multiyear ice), summer weather patterns also have a large impact on the amount of ice that will be left at the end of summer.

Satellite Observations of Arctic Change

NSIDC now offers a new Web site, Satellite Observations of Arctic Change (SOAC)  with interactive maps of the Arctic based on NASA satellite and related data. The site allows you to explore how conditions in the Arctic have changed over time. Data sets include air temperature, water vapor, sea ice, snow cover, NDVI, soil freezing, and exposed snow and ice. Time periods vary by data set, but range from 1979 to 2013. You can animate a time series, zoom in or out, and view a bar graph of anomalies over time. Links to the source data and documentation are also included. Additional pages provide brief scientific discussion, and overviews of the scientific importance of these data. SOAC was developed with support from NASA Earth Sciences.

Reference

Stroeve, J., L. Hamilton, C. M. Bitz, and E. Blanchard-Wrigglesworth. 2014. Predicting September Sea Ice: Ensemble Skill of the SEARCH Sea Ice Outlook 2008–2013. Geophysical Research Letters, Accepted, doi: 10.1002/2014GL059388.

Correction

In the caption for Figure 5, we described the map as showing the ages of ice in the Arctic at the end of March. A reader pointed out that this image was for the beginning of March, which is correct. We regret the error and corrected the caption on April 2, 2014 at 1:25 p.m.

While the eastern half of the United States has dealt with a cold and snowy winter, temperatures in the Arctic have been distinctly higher than average. The warm conditions have led to a slower than average expansion of the winter ice cover. Less ice also contributes to higher air temperatures by allowing transfer of heat from the relatively warmer ocean. The annual maximum in sea ice extent is expected to occur sometime this month.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2014 was 14.44 million square kilometers (5.58 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

Arctic sea ice extent in February 2014 averaged 14.44 million square kilometers (5.58 million square miles). This is the fourth lowest February ice extent in the satellite data record, and is 910,000 square kilometers (350,000 square miles) below the 1981 to 2010 average. The lowest February in the satellite record occurred in 2005.

Overall, sea ice grew slowly through the month of February. There were periods of declining ice, likely related to changes in ice motion. Bering Sea ice cover has been below average throughout winter, in contrast to the last several winters. Ice extent also remains below average in the Barents Sea and the Sea of Okhotsk, helping to keep the Arctic ice extent two standard deviations below the 1981 to 2010 average.

Conditions in context

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

Ice extent increased at an average daily rate of 14,900 square kilometers (5,750 square miles) per day through the month of February. This is about 25% slower than the 1981 to 2010 February average rate of 20,300 square kilometers (7,840 square miles) per day. As the maximum extent approaches, the daily rate of ice extent growth is expected to slow.

While the eastern half of the U.S. has suffered through a cold and sometimes snowy winter, conditions in the Arctic have been warmer than average. The Arctic in winter is still a very cold place and temperatures at the 925 mb level in the central Arctic averaged -25 to -15 degrees Celsius (-13 to 5 degrees Fahrenheit); however, this was 4 to 8 degrees Celsius (7 to 14 degrees Fahrenheit) above average for the month. The Arctic Oscillation settled into a near-neutral mode for February after swinging from a strong positive mode in December to a negative mode in January.

February 2014 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2014 shows a decline of -3.0% per decade per decade relative to the 1981 to 2010 average.

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

The sea ice extent trend through February 2014 is -3.0% per decade relative to the 1981 to 2010 average, a rate of -46,100 square kilometers (-17,800 square miles) per year. Unlike the summer, where ice loss has accelerated over the past decade, winter month trends have been fairly consistent.

The two Bs of the Arctic: Barents and Bering

Figure 4a. Barents Sea ice extent during February from the NSIDC Multisensor Analyzed Sea Ice Extent (MASIE) for the years 2010 through 2014. MASIE is produced daily by the U.S. National Ice Center based on human analysis of a variety of available satellite imagery.

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

Figure 4b. Bering Sea ice extent during February from the NSIDC Multisensor Analyzed Sea Ice Extent (MASIE) for the years 2010 through 2014. MASIE is produced daily by the U.S. National Ice Center based on human analysis of a variety of available satellite imagery.

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

The Barents Sea has experienced consistently low extents, particularly in winter, and this year has been no different. While the Barents and Kara seas normally have close to 2 million square kilometers (772,000 square miles) of ice in February, recent years have seen 500,000 square kilometers (193,000 square miles) of ice extent or lower. This year, the Kara Sea is near average, but the Barents Sea remains low (Figure 4a). Unlike other regions in the Arctic, longer records of Barents Sea ice extent exist from records of fishing, whaling, and other activities. A recent paper (Miles et al., 2013) examined these records, along with paleoproxy data, to examine extent over the past four hundred years. They found a 60- to 90-year cycle in Barents and Greenland seas ice extent related to the Atlantic Multidecadal Oscillation (AMO); the AMO is a basin-wide cycle of sea surface temperature variability similar to the El Niño and La Niña cycles in the Pacific, but varying over much longer periods. This research shows that in addition to the warming trend in the Arctic, some sea ice regions are likely also responding to natural climate variability.

In contrast to the Barents, the Bering Sea ice has had higher than average extent in recent years. However this year is different; Bering Sea ice extent has been below average through much of the winter. During mid-February, extent increased to a higher level, as seen in Multisensor Analyzed Sea Ice Extent (MASIE) data (Figure 4b), before a slight decline at the end of the month. This is in contrast with recent years in the Bering that have seen very high extents, even record levels .

The Bering Sea consists exclusively of seasonal ice with a large marginal ice zone where new, thin ice dominates. Sea ice in this region is quite sensitive to changes in temperatures and, particularly, winds. Cold winds from the north advect ice southward and aid new ice growth. Warm winds from the south impede ice growth and push the ice northward, reducing extent in the region. Recent winters have been characterized by predominantly north winds. This year represents a change with more zonal, east to west, winds in January and February. As with the Barents Sea, the Bering may be responding to climate variability, including the Pacific Decadal Oscillation, though the links are complex (Bond et al., 2003).

Winter and spring ice in the Bering Sea is of high importance to people living in the region, such as walrus hunters who go out on the ice or in boats during spring and early summer. Because ice conditions are so important, analyses and forecasts, such as those provided by the SEARCH Sea Ice for Walrus Outlook (SIWO), are particularly valuable. The SIWO program begins reporting on sea ice in late March or early April and continues through late June. The site provides sea ice imagery and analysis, reports from hunters in the field, and forecasts of future conditions. These reports are important for hunters to plan hunts and safely traverse the ice-infested waters.

References

Bond, N. A., J. E. Overland, M. Spillane, and P. Stabeno. 2003. Recent shifts in the state of the North Pacific, Geophys. Res. Lett., 30, 2183, doi:10.1029/2003GL018597, 23.

Miles, M. W., D. V. Divine, T. Furevik, E. Jansen, M. Moros, and A. E. J. Ogilvie. 2014. A signal of persistent Atlantic multidecadal variability in Arctic sea ice, Geophys. Res. Lett., 41, doi:10.1002/2013GL058084.

Overview of conditions

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 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 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

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 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 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.

Daily sea ice growth rates were variable during December. By the end of the month, ice extent remained below average in most of the far north. In Antarctica, ice extent remained above average and access to the continent by ship has been more difficult than normal.

 Overview of conditions

Figure 1. Arctic sea ice extent for December 2013 was 12.38 million square kilometers (4.78 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 for December was 12.38 million square kilometers (4.78 million square miles). This is 700,000 square kilometers or 270,300 square miles below the 1981 to 2010 average, making it the 4th lowest December extent in the 36-year satellite data record. Arctic sea ice expanded in December by 1.85 million square kilometers (714,000 square miles), slightly less than average, with some periods of very slow growth and even retreat as storms briefly pushed the sea ice edge northward.

Monthly average ice extent was less than the 1981 to 2010 average in both the far northeast Atlantic (Barents Sea) and along the entire northwest Pacific coast (Bering Sea and Sea of Okhotsk). Near-average ice extent was the rule in the Greenland Sea and Baffin Bay.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of January 6, 2014, along with daily ice extent data for five previous years. 2013 to 2014 is shown in blue, 2012 to 2013 in brown, 2011 to 2012 in green, 2010 to 2011 in pink, and 2009 to 2010 in navy. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

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

Ice grew at rates slower than average through most of December, at 59,500 square kilometers per day (23,000 square miles per day) compared to the 1981 to 2010 average of 62,400 square kilometers per day (24,100 square miles per day). At the end of the month the extent was 750,000 square kilometers (289,600 square miles) below the 1981 to 2010 average and nearly identical to the extent at the end of 2012.

Similar to November, the early part of December was dominated by a positive Arctic Oscillation pattern, but this shifted to near-neutral conditions by the end of the month. The Icelandic low, covering much of the northern North Atlantic Ocean, was stronger than average, and pressures were higher than average over the Bering Sea and Alaska. Air temperatures at the 925 hPa level (about 3,000 feet above the surface) were above average for the month over most of the Arctic Ocean; unusual warmth was most notable over far eastern Siberia (6 degrees Celsius or 11 degrees Fahrenheit above average). Over the central Arctic Ocean, temperatures at the 925 hPa level were 2 to 5 degrees Celsius or 4 to 9 degrees Fahrenheit above average. By sharp contrast, relatively cool conditions prevailed over northern North America. Temperatures in areas such as the Yukon Territory were 6 degrees Celsius (10 degrees Fahrenheit) or more below average.

December 2013 compared to previous years

Figure 3. Monthly December ice extent for 1978 to 2013 shows a decline of −3.5% per decade relative to the 1981 to 2010 average.

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

The linear trend in ice extent for December (1978 through 2013) is now −3.5% per decade, or −46,500 square kilometers per year (−18,000 square miles per year). The lowest December extent was recorded in 2010 (12.02 million square kilometers or 4.64 million square miles). The spatial pattern of ice extent in December 2013 was similar overall to what was seen in 2010, except that 2010 had much less ice cover in Hudson Bay and Baffin Bay.

2013 in review

While the most notable aspect of 2013 was the much higher September ice extent relative to the record low for 2012, extent in 2013 was nevertheless low overall. The maximum extent for 2013 of 15.13 million square kilometers (5.84 million square miles), recorded on 15 March was the sixth lowest over the period of satellite observations. The minimum of 5.10 million square kilometers (1.97 million square miles), recorded on 15 September, was also the sixth lowest.

Continuing a recent pattern, ice extent remained below average over the northern North Atlantic throughout the year. Sea ice retreat began unusually early in the northern Barents and Kara seas. By comparison, sea ice retreated from the Alaskan coast later than in recent years. This occurred despite unusually active late winter fracturing of the ice pack in the region. The fraction of the Arctic sea ice cover comprised of old ice continued to decline.

Summer weather patterns during 2013 were very different from those seen in 2007 to 2012. Overall it was considerably cooler. There was little evidence of the summer dipole pattern seen in recent years. Relatively cool conditions also characterized the Greenland Ice Sheet, and surface melt was much less extensive than for 2012. The year 2013 reminds us that natural climate variability is very strong in the Arctic.

In Antarctica, sea ice extent has been well above average, setting record extents for both the summer minimum and winter maximum. For a long period over the winter and spring months, ice extent was at a record for the modern satellite era. While remarkable, it is important to note that trends in Antarctic sea ice extent remain small (1 to 4%) and are statistically significant relative to inter-annual variation only for the late autumn, winter, and early spring months. Early satellite records (the Nimbus satellite series in 1964, 1966, and 1969) provide further evidence that Antarctic sea ice extent is highly variable; the three years covered by Nimbus show September extents that were both higher and lower than seen in the modern continuous, calibrated satellite record.

So you want to be like Mawson?

Heavy Antarctic sea ice conditions along the Wilkes Land Coast near France’s Dumont D’Urville Station and persistent onshore to easterly winds have trapped a Russian ice-hardened vessel conducting a mixed science and tourism cruise. The cruise by the Akademik Shokalskiy was attempting to re-measure some of the climate, ice, and ocean conditions made by the Aurora , Sir David Mawson’s research vessel on his 1911 to 1913 expedition to the region. The region is often swept clear of ice by this time in the summer season by strong katabatic offshore winds; Cape Denison and Commonwealth Bay (near to the stuck ship’s location) are recognized as some of the windiest places on Earth. However, December was marked by long periods of northeasterly airflow, pushing the sea ice against the coast, and piling up the thinner flows into a nearly impenetrable mass.

The ship’s entrapment, with limited supplies for the larger science and expedition group, led to a complex multi-ship rescue executed in early January. However, several of the rescue icebreakers are having trouble with the ice conditions. As this summary is written, the U.S. Coast Guard icebreaker Polar Star is planning an attempt to help free the new Chinese research icebreaker Snow Dragon. The Polar Star is among the most powerful icebreakers ever built.

Ice extent in the Arctic was below average during November. There was substantially less ice than average in the northern Barents Sea, likely due to an influx of warm ocean waters and the persistence of a strong positive Arctic Oscillation (AO). In contrast, sea ice extent in Antarctica remained unusually high.

Overview of conditions

Figure 1. Arctic sea ice extent for November 2013 was 10.24 million square kilometers (3.95 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 continued to expand during November, gaining 2.24 million square kilometers (865,000 square miles) of ice since the beginning of the month. Sea ice extent for November averaged 10.24 million square kilometers (3.95 million square miles). This is 750,000 square kilometers (290,000 square miles) below the 1981 to 2010 average extent and is the 6th lowest November extent in the 35-year satellite data record. As was the case for October 2013, sea ice extent for November 2013 remained within two standard deviations of the long-term 1981 to 2010 average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of December 2, 2013, along with daily ice extent data for the previous five 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

For the month as a whole, ice grew at near average rates throughout November at 74,800 square kilometers (28,900 square miles) per day compared to the 1981 to 2010 average of 70,500 square kilometers (27,200 square miles) per day. This was despite a period of slow ice growth during the first part of the month. At the end of the month, extent was 580,000 square kilometers (224,000 square miles) lower than average and 420,000 square kilometers (162,000 square miles) above the same time last year.

The below average ice extent in the Arctic was largely due to a lack of ice in the Barents Sea, which has shown a pattern of low autumn and winter ice extent over the recent years. This November, the overall extent in the Barents Sea was the second lowest in the satellite record, with the lowest occurring in 2012.

The low ice in the Barents Sea is due to several possible factors. First, it could reflect the influx of warm ocean currents that inhibited ice growth. The atmosphere also played some role. Sea level pressure over the Arctic Ocean was lower than normal by as much as 9 to 12 hPa. This is consistent with the persistent strongly positive phase of the AO seen through the month; a positive AO generally leads to higher than average air temperatures over Eurasia and adjacent sea ice areas. November air temperatures in the Barents Sea were on the order of 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average. The higher than average temperatures may also simply reflect the lack of sea ice in the Barents Sea. This is because under open water conditions, the ocean readily releases heat to the overlying atmosphere.

November 2013 compared to previous years.

Figure 3. Monthly November ice extent for 1978 to 2013 shows a decline of –4.9% per decade relative to the 1981 to 2010 average.

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

Including 2013, the linear trend in November ice extent is –4.9% per decade relative to the 1981 to 2010 mean, or –53,500 square kilometers per year (–20,700 square miles per year).

 Extensive ice in Antarctica

Figure 4a. Antarctic sea ice extent for November 2013 was 17.2 million square kilometers (6.63 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

While it is early winter in the Arctic, it is early summer in the Antarctic. Continuing patterns seen in recent years, Antarctic sea ice extent remains unusually high, near or above previous daily maximum values for each day in November. Sea ice is anomalously extensive across the Peninsula, the Amundsen Sea, and the Wilkes Land sectors. However, it has retreated in the northern Ross Sea  region—where it had been far to the north of the mean ice edge—to more typical extent locations. Sea ice extent averaged 17.16 million square kilometers (6.63 million square miles) for November. The long-term 1981 to 2010 average extent for this month is 16.30 million square kilometers (6.29 million square miles).

Figure 4b. The graph above shows Antarctic sea ice extent as of December 2, 2013, along with daily ice extent data for the previous year. 2013 is shown in light blue and 2012 in dark blue. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

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

Beginning in October, wind conditions in the Ross Sea shifted from a direction favoring a northward growth of sea ice to a more westerly direction. This and the coming of sunshine and warmth with spring led to a retreat from record ice extents there. However, November brought cool conditions (1 to 3 degrees Celsius, or 2 to 5 degrees Fahrenheit, below the 1981 to 2010 average) around the Peninsula and much of the western hemisphere of the Southern Ocean. Winds have also favored a northward drift along the western Peninsula. Overall, cool conditions and extensive ice around the Peninsula strongly contrast with the past few decades’ shift to a more ice free Peninsula and extensive surface melting there. Palmer Station, the U.S. Antarctic research base, was once again briefly surrounded by sea ice this winter, as it was in 2012.

Overall, the extreme sea ice extent may be linked to strong variations in the westerly wind flow, the main circulation around Antarctica. Strong westerly flow favors ice growth in autumn and early winter, and this was the case; however, as sea ice approached a maximum, the westerly wind pattern abated, allowing ice to drift even further north than usual, in some places urged on by southerly winds.

At the same time, part of the interior has seen record warm winter events, with several daily temperature records set at the South Pole . These warm events are also linked to the reduction in westerly wind strength in August to October. Weaker westerly winds allow more north-south flow into Antarctica, occasionally bringing relatively warm air masses into the interior. Between September 11 and September 15, usually a time of unimaginable cold, four daily maximum temperature records were set, in one case by more than 8.5 degrees Celsius (15.3 degrees Fahrenheit). On September 13, the temperature reached –27.7 degrees Celsius (–17.9 degrees Fahrenheit), a temperature more typical of early summer conditions.

Big berg backs out of bay

Figure 5. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite captured a true-color image of the iceberg in Pine Island Bay on November 16. The iceberg has been named B-31 by the U.S. National Ice Center and is about 35 kilometers by 20 kilometers, roughly the size of Singapore.

Credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC
High-resolution image

In Pine Island Bay, a medium-sized iceberg that had been pinned on a shoal near the front of Pine Island Glacier began to drift into the Southern Ocean. The iceberg has received significant attention because it has broken away from Antarctica’s largest glacier (as measured by amount of ice moved per year). Pine Island Glacier has accelerated significantly in recent years as increasingly warm ocean water at depth have melted and thinned the ice at the point where the glacier goes afloat. NASA scientists and other groups like the British Antarctic Survey have installed instruments and are making further measurements to determine if the glacier will accelerate further in the aftermath of the loss of the iceberg.

Increased methane emission from the Siberian sea floor

A recent paper by colleagues at the University of Alaska Fairbanks suggests that ocean bottom water temperatures are increasing as Arctic sea ice cover has decreased, leading to a recent increase in methane flux from the seabed to the atmosphere. Ship-based observations show that methane concentrations in the air above the East Siberian Sea Shelf are nearly twice as high as the global average.

The Siberian continental shelf is a vast region of shallow-water covered continental crust, comprising about 20% of the global area of the continental shelf. During the last glacial maximum, much of the shelf was exposed to the cold atmosphere and froze to a depth of about 1.5 kilometers (about 1 mile). Layers of sediment below the permafrost slowly emit methane gas, and this gas has been trapped for millennia beneath the permafrost. As sea levels rose at the end of the ice age, the shelf was once again covered by relatively warm ocean water, thawing the permafrost and releasing the trapped methane. Methane is a potent greenhouse gas but is relatively short-lived in the atmosphere (about 12 years), leading to reduced global warming potential over time. In the short-term however, methane has a global warming potential 86 times that of carbon dioxide.

Reference

Shakhova, N., I. Semiletov, I. Leifer, V. Sergienko, A. Salyuk, D. Kosmach, D. Chernykh, C. Stubbs, D. Nicolsky, V. Tumskoy, and Ö. Gustafsson. 2013. Ebullition and storm-induced methane release from the East Siberian Arctic Shelf. Nature Geoscience, http://dx.doi.org/10.1038/ngeo2007 .

Nearly frozen up by the end of October, the Arctic Ocean still showed small regions of open water within the Beaufort and Chukchi seas on its western side, and within the Kara Sea on its eastern side. These open water areas contributed to warmer than average air temperatures over the western Arctic.

Overview of conditions

Figure 1. Arctic sea ice extent for October 2013 was 8.10 million square kilometers (3.13 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 continued to expand during October as temperatures dropped and the number of daylight hours diminished, gaining 3.21 million square kilometers (1.24 million square miles) of ice since the beginning of the month. Average ice extent for October was 8.10 million square kilometers (3.13 million square miles), making it the 6th lowest October extent in the 35-year satellite data record. This was 810,000 square kilometers (313,000 square miles) below the 1981 to 2010 average extent. The October 2013 extent remains within two standard deviations of the long-term 1981 to 2010 average.

As open water areas refreeze and continue to lose the heat gained during the summer back to the atmosphere, near surface air temperatures have remained higher than average over areas that have not yet completely frozen over. As of the beginning of November, small parts of the Beaufort, Chukchi, and Kara seas remain ice free, while the East Siberian and Laptev seas have completely frozen over. Higher than average air temperatures have been observed over the ice-free regions while the rest of the Arctic is at near average to below average temperatures. This is in contrast to the first half of October 2012 when large parts of the East Siberian and Laptev seas remained ice free and the entire Arctic was warmer than average.

Conditions in context

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

Ice grew at rates faster than average throughout October, at 103,500 square kilometers (40,000 square miles) per day compared to the 1981 to 2010 average of 87,500 square kilometers per day (33,800 square miles per day). However, this rate is slower than last year, when ice extent doubled during the month of October. Nevertheless, the ice cover is more extensive than in 2012. At the end of the month the extent was 710,000 square kilometers (274,100 square miles) below average and 1.1 million square kilometers (424,700 square miles) above the same time last year.

While the sea ice extent this summer was higher than the past several summers, extent remained anomalously low compared to the long-term mean, and the larger regions of open water during summer were able to absorb the sun’s energy, leading to higher sea surface temperatures. Before the ocean can refreeze in the autumn, it releases this excess heat back to the atmosphere, resulting in higher than average air temperatures. In October, air temperatures along the coastal Beaufort Sea were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) higher than average. Air temperatures were also 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) higher than average over much of the western and central Arctic and near Greenland and the Canadian Archipelago.

October 2013 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2013 shows a decline of –7.1% per decade relative to the 1981 to 2010 average.

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

The year 2013 marks the first October with an extent above 8 million square kilometers (3.09 million square miles) since 2009 and only the second since 2006. From 1979 to 2006, average October extent was never below 8 million square kilometers, and several years had October extents above 9 million square kilometers (3.47 million square miles). The lowest October extent, less than 7 million square kilometers (2.7 million square miles), was observed in 2007. The linear trend in October ice extent is –7.1 % per decade relative to the 1981 to 2010 mean, or –63,400 square kilometers per year (–24,500 square miles per year).

Sea ice decline and the greening of Arctic tundra

Figure 4. Yellow flowers (Papaver dahlianum), typical of the high Arctic subzone A, dot the tundra on Ellef Ringnes Island in Nunuvut, Canada. Arctic tundra is the coldest of the Circumpolar Arctic Vegetation Map’s bioclimate subzones. The subzones range from mean July temperatures just above freezing in the tundra (Subzone A) to mean July temperatures of around 10 degrees Celsius in Subzone E where shrubs can reach up to heights of 2 meters.

Credit: D. A. Walker
High-resolution image

As sea ice extent declined over the past years, Arctic tundra has received an increased amount of summer warmth and has gotten greener. Arctic tundra (Figure 4) is a maritime biome, most of which can be found within 100 kilometers (62 miles) of seasonally ice-covered seas. This proximity to sea ice limits the tundra’s exposure to available warmth and vegetation growth. Over 30 years of remote sensing data show that the decline in sea ice extent corresponds to land surface warming (Figure 5, left panel) and increased vegetation cover (Figure 5, right panel, Maximum Normalized Difference Vegetation Index, or MaxNDVI). When sea ice extent is below average in coastal seas, land surfaces warm, and satellites see a stronger signal of vegetation.

Figure 5. These charts show trends in spring sea ice, land surface warmth, open water area, and vegetation from 1982 to 2012. The percent trend highlights the size of relative changes in the Arctic. Sea ice (top left) is shown as percent concentration; land surface temperature (top right) is expressed as summer warmth index (SWI); open water (bottom left) is expressed as percent of area; and vegetation (bottom right) is shown as Maximum Normalized Difference Vegetation Index (MaxNDVI). Data are derived from AVHRR.

Credit: U.S. Bhatt
High-resolution image

However, the same data offer a few puzzles. While land surface warming and vegetation cover have steadily increased in the vicinity of Greenland over the last thirty years, warming and vegetation have actually decreased in some parts of Eurasia over the last decade. This suggests that once sea ice declines or the climate warms beyond a limit, other processes begin to play a more central role in summer climate variability, such as moisture availability in the soil or cloudiness, which can lead to cooler conditions during the northern summer. Another mystery is the decline in vegetation cover over the southwest Alaskan tundra despite an increase in land surface temperature over the same period. Researchers are looking into these puzzles as they think ahead to what the tundra may look like in a future of ice-free summers.

Further reading

Bhatt, U.S., D.A. Walker, M.K. Raynolds, P.A. Bieniek, H.E. Epstein, J.C. Comiso, J.E. Pinzon, C.J. Tucker, and I.V. Polyakov. 2013. Recent Declines in Warming and Arctic Vegetation Greening Trends over Pan-Arctic Tundra. Remote Sensing (Special NDVI3g Issue), 5, 4229-4254; doi:10.3390/rs5094229.

Bhatt, U.S., D.A. Walker, M.K. Raynolds, J.C. Comiso, H.E. Epstein, G. Jia, R. Gens, J.E. Pinzon, C.J. Tucker, C.E. Tweedie, and P.J. Webber. 2010. Circumpolar Arctic tundra vegetation change is linked to sea-ice decline. Earth Interactions. August 2010, Vol. 14, No. 8: 1-20. doi: 10.1175/2010EI315.1.

Raynolds, M.K., Walker, D.A. & Maier, H.A. 2006. NDVI patterns and phytomass distribution in the circumpolar Arctic. Remote Sens. Environ. 102: 271-281.

Walker, D.A. et al. 2005. The Circumpolar Arctic Vegetation Map. J. Veg. Sci., 16, 267–282.

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

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

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 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 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 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

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 *

* 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.

On September 13, Arctic sea ice reached its likely minimum extent for 2013. The minimum ice extent was the sixth lowest* in the satellite record, and reinforces the long-term downward trend in Arctic ice extent. Sea ice extent will now begin its seasonal increase through autumn and winter. Meanwhile, in the Antarctic, sea ice extent reached a record high on September 18, tied with last year’s maximum.

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 13, 2013 was 5.10 million square kilometers (1.97 million square miles). The orange line shows the 1981 to 2010 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 13, 2013, sea ice extent dropped to 5.10 million square kilometers (1.97 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 two days earlier than the 1981 to 2010 average minimum date of September 15.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 19, 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

This year’s minimum was 1.69 million square kilometers (653,000 square miles) above the record minimum extent in the satellite era, which occurred on September 16, 2012, and 1.12 million square kilometers (432,000 square miles) below the 1981 to 2010 average minimum.

Varying distribution of ice in 2013 versus 2012

Figure 3. This image compares differences in ice-covered areas between September 13, 2013, the date of this year’s minimum, and September 16, 2012, the record low minimum extent. Light gray shading indicates the region where ice occurred in both 2013 and 2012, while white and dark gray areas show ice cover unique to 2013 and to 2012, respectively. Sea Ice Index data. About the data

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

Comparing this year’s minimum extent to 2012, while extent was higher on average this year, there were variations from region to region. There was considerably higher sea ice extent in the Beaufort, Chukchi, and East Siberian sea regions, with the ice edge several hundred kilometers farther south compared to last year. This year the Canadian Archipelago also retained much more ice, keeping the Northwest Passage closed.  The most notable area of less ice this year compared to last was off the east coast of Greenland, south of Fram Strait. Other small areas of decreased extent were found north of the Kara and Laptev seas.

See an animation of this summer’s sea ice extent produced by the NASA Scientific Visualization Studio at http://svs.gsfc.nasa.gov/goto?4104.

Previous minimum Arctic sea ice extents**

* According to near-real-time data, this year’s minimum extent is slightly lower than 2009. However, the ranking between 2009 and 2013 is close, and may change once the final version of the data are processed. See our Frequently Asked Questions: Do your data undergo quality control? for more information about near-real-time data.

** 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.

Following a relatively cool summer, sea ice extent fell to a little over 5 million square kilometers (1.93 million square miles) over the first two weeks of September and is at or near the minimum extent for the year. NSIDC will announce the final minimum extent and date once it is confirmed.

Overview of conditions

Figure 1. Arctic sea ice extent for September 16, 2013 was 5.10 million square kilometers (2.00 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

Arctic sea ice extent as of September 16, 2013 was 5.10 million square kilometers (2.00 million square miles). This is substantially more ice than observed on the same date last year, yet sea ice extent remains quite low compared to the long-term 1981 to 2010 average. As is typical for this time of year, winds or currents can compact or spread apart the ice, resulting in small daily fluctuations of the ice cover.

During the first two weeks of September, sea ice extent continued to decline in the East Siberian, Laptev, and Kara seas while staying essentially constant in the Beaufort and Chukchi seas since the beginning of September. The Northwest Passage has seen more extensive ice this summer since 2007 and is not open. On the Eurasian side of the Arctic, the Northern Sea Route appears to have opened up briefly in September.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 15, 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

Ice loss through the first two weeks of September was faster than average. Air temperatures at the 925 hPa level were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) higher than average over much of the Arctic Ocean the first part of the month, in stark contrast to most of the summer when cooler temperatures dominated. Below average temperatures were found in the Beaufort and Chukchi seas where ice growth began around the first week of the month.

Even though extent at the beginning of this summer was similar to last year, the melt season ended with considerably more ice. This is not surprising, as climate models consistently project that there will be large variations in summer ice extent from year to year. A cool summer can help to retain a thin layer of ice, increasing the overall ice extent. Conversely, a warm summer can help to remove much of the thin ice cover.

Cold summer over central Arctic and Greenland

Figure 3: These figures show air temperature anomalies averaged from June, July, and August 2013 at the 925 hPa level, relative to the 1981 to 2010 average (left) and relative to the 2007 to 2012 average (right).

Credit: NOAA/ESRL Physical Sciences Division
High-resolution image

As a whole, air temperatures this summer have been below average over most of the central Arctic Ocean and Greenland, helping to slow down ice melting. Compared to the 1981 to 2010 average, air temperatures at the 925 hPa level have been -0.5 to -2.0 degrees Celsius (-0.9 to -3.6 degrees Fahrenheit) below average over central Greenland, north of Greenland and towards the pole, and over the Canadian Archipelago. Unusually low temperatures are also noted over the East Siberian Sea, where ice cover has remained near average throughout the summer.

The cool conditions that have prevailed this summer are even more remarkable when compared to the last six years, which have seen very low September sea ice extents. Compared to the 2007 to 2012 average, air temperatures at the 925 hPa level averaged over June, July and August were lower this summer throughout most of the Arctic by -0.5 to -3.5 degrees Celsius (-0.9 to -6.3 degrees Fahrenheit). The previous six summers have been dominated by high sea level pressure over the Beaufort Sea and Greenland, paired with low sea level pressure over Eurasia—a pattern that helps to transport warm air into the Arctic. In contrast, this summer was characterized by low sea level pressure over the central Arctic and Greenland. Cooler conditions have also led to less surface melting on the Greenland Ice Sheet.

Sea surface temperature trends

Figure 4: These maps show Arctic sea surface temperatures  (top) and temperature anomalies (bottom) for August 2013, in degrees Celsius. 

Credit: Michael Steele and Wendy Ermold, Polar Science Center, Applied Physics Lab, University of Washington
High-resolution image

Colleagues Michael Steele and Wendy Ermold at the University of Washington found that sea surface temperatures (SSTs) in the Arctic Ocean were above the 1982 to 2006 average during August, as has been the case since 2007. Sea ice retreat was later and not as extreme relative to recent years in the western Arctic (i.e., the Beaufort, Chukchi, and East Siberian seas) and as a result, SSTs were near the long-term average there. SSTs were well above average in the eastern Arctic (Laptev, Kara, and Barents seas). This can be linked to early ice retreat in the Laptev Sea. However, warm conditions in the southern Barents and Kara seas are likely influenced by advection of warm water from the south in the Norwegian Sea. Overall, for the period 2007 to 2013 there is a pattern of declining SSTs in the western Arctic, and increasing SSTs in the eastern Arctic.

Antarctic sea ice extent

Figure 5. Sea ice extent data from high-resolution passive microwave data (top left and right), and climate data for the period August 15 to September 15, 2013 (bottom images). These images show Antarctic sea ice extent near the satellite-era record high set last year. The geopotential height at 850 millibars (lower left) is an indication of the relative air pressure at ~5000 feet (~1500 meters) above sea level. This shows an unusually broad area of high pressure encompassing the entire continent out to near the sea ice edge, and low pressure surrounding that outside the edge – the opposite of the general trend. This has greatly reduced the average westerly wind flow (shows as negative values in the zonal wind plot, lower right), making for light winds at the sea ice edge.

Credit: University of Bremen/AMSR2 (top images) and NOAA/ESRL Physical Sciences Division (bottom images).
High-resolution image

As ice extent approaches its summer minimum in the Arctic, the winter maximum is near for Antarctica. This year, as was the case in 2012, Antarctic sea ice extent is very high. As of September 16, the current extent is 19.45 million square kilometers (7.51 million square miles), a record for this date with respect to the 1979 to 2012 satellite era. This is about 3.9% above the average maximum extent for the 30-year comparison period 1981 to 2010. In contrast, this year’s Arctic summer minimum ice extent is approximately 30% below levels seen in the early 1980s, and the 2012 record low extent was around 60% below levels seen in the same period. This helps to highlight why scientists are more concerned by Arctic ice shrinkage than by Antarctic ice expansion.

Antarctic weather patterns in August were unusual. Contrary to a 50-year trend towards stronger westerly wind flow—a pattern associated with both ozone loss and increased heat-trapping gases in the atmosphere—August 2013 saw a period of very low westerly wind speed across the continent.

* Note: On September 19, 2013, we revised a sentence in this section for clarity. A sentence that originally read, “In contrast, this year’s Arctic summer minimum ice extent is approximately 30% below the 30-year period average, and the 2012 record low extent was nearly 60% below the average.” now reads, “In contrast, this year’s Arctic summer minimum ice extent is approximately 30% below levels seen in the early 1980s, and the 2012 record low extent was around 60% below levels seen in the same period.”

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 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

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 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 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 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.)