Late summer in the Arctic, sea ice melt continues

As of August 14, Arctic sea ice extent is tracking third lowest in the satellite record. The southern route through the Northwest Passage appears to be largely free of ice. Despite a rather diffuse ice cover in the Chukchi Sea, it is unlikely that Arctic sea ice extent this September will fall below the record minimum set in 2012.

Overview of conditions

Figure 1. Arctic sea ice extent for August 14, 2016 was 5.61 million square kilometers (2.17 million square miles). The orange line shows the 1981 to 2010 median extent for that day

Figure 1. Arctic sea ice extent for August 14, 2016 was 5.61 million square kilometers (2.17 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

As of August 14, Arctic sea ice extent was 5.61 million square kilometers (2.17 million square miles). This is the third lowest extent in the satellite record for this date and slightly below the two standard deviation range. So far this month the rate of loss has been faster than average and has declined at a rate similar to that observed for 2012.

Ice loss has progressed quite rapidly in the Beaufort and Chukchi seas, where broken up ice floes are starting to melt away. However, large, thick multiyear ice floes persist in several areas; it remains to be seen if they will survive the melt season. A wedge of open water has also penetrated northward from the East Siberian Sea, yet ice remains extensive in the Laptev Sea, blocking the Northern Sea Route. Ice extent continues to be low in the Kara, Barents, and East Greenland seas. The southern (Amundsen’s) route through the Northwest Passage appears open in Advanced Scanning Microwave Radiometer 2 (AMSR2) data. However, data in visible wavelengths from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) instrument still show some ice.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 14, 2016, along with daily ice extent data for four previous years.

Figure 2. The graph above shows Arctic sea ice extent as of August 14, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 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
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Ice loss from August 1 to 14 was faster than average, at 87,400 square kilometers (33,800 square miles) per day, and near the rates observed in 2012. Nevertheless, as has been the pattern this summer, atmospheric conditions through the first half of August have been generally cloudy and cool. Air temperatures at the 925 hPa level were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below the 1981 to 2010 long-term average over the eastern part of the Arctic Ocean and near average elsewhere. The cool and cloudy conditions reflect a pattern of low atmospheric pressure over the Laptev and Kara seas.

As of August 16, a strong storm (central pressure of 968 hPa) was located over the Central Arctic Ocean at about 85 degrees North, near the dateline. The extent to which this strong storm will affect sea ice conditions remains to be seen.

Ocean heat continues ice melt

Figure 3. The map shows average ocean sea surface temperature (SST) and sea ice concentration for August 7, 2016. SST is measured by satellites using thermal emission sensors, which produce a global data adjusted by comparison with ship and buoy data. Sea ice concentration is derived from the NSIDC sea ice concentration near-real-time data. Also shown are drifting buoy temperatures at the ocean surface (colored circles); gray circles indicate that temperature data from the buoys are not available. ||Credit: M. Steele, Polar Science Center/University of Washington| High-resolution image

Figure 3. The map shows average ocean sea surface temperature (SST) and sea ice concentration for August 7, 2016. SST is measured by satellites using thermal emission sensors, which produce global data adjusted after comparison with ship and buoy data. Sea ice concentration is derived from NSIDC sea ice concentration near-real-time data. Also shown are drifting buoy temperatures at the ocean surface (colored circles); gray circles indicate that temperature data from the buoys are not available.

Credit: M. Steele, Polar Science Center/University of Washington
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The Arctic atmosphere is cooling now as the sun dips lower in the sky. However, sea ice loss will continue throughout August due primarily to melt from the ocean heat that has accumulated over the summer. Early ice retreat has allowed the ocean to warm, both from absorption of the sun’s energy and from northward-flowing warm water in the Chukchi Sea to the west of Alaska and in the Barents Sea to the north of Norway. Unusually strong ocean warming occurred in northern Baffin Bay (between northern Canada and Greenland), the Beaufort Sea (north of northwestern Canada and Alaska), the East Siberian Sea (north of far eastern Siberia), and the Barents and Kara seas (north of western Eurasia).

What is quite unusual this year is the early ice retreat and resulting ocean warming in the western Beaufort Sea and in the western East Siberian Sea. The extent of warming to the north of these two seas is also unusual, as well as the extent of this warming to the north. These two areas typically melt out later in the season, when atmospheric heating rates have declined from their mid-summer peak. Thus the exposed ocean warms, but not all that much. This pattern was true during the record-setting year of 2012, when by the end of summer, these areas were substantially cooler than surrounding seas that had melted out earlier.

This year, however, the melt out was early and extensive enough that the ocean has already warmed substantially in these two areas. More sea ice retreat is probable in the western Beaufort and East Siberian seas as well as areas in the coming weeks. But what about the ocean’s response? Some warm water might move northward via ocean currents and contribute to ice melt. However, further dramatic ocean surface warming is unlikely, given that the atmosphere is already cooling, especially in far northern latitudes.

Ice loss rates indicate little chance for a record low this year

Figure 4. The graph above shows projections of ice extent from August 14 through September 30 based on previous years’ observed retreat rates appended to the August 14, 2016 ice extent.

Figure 4. The graph above shows projections of ice extent from August 14 through September 30 based on previous years’ observed retreat rates appended to the August 14, 2016 ice extent.

Credit: W. Meier/NASA GSFC
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While there are still three to four weeks to go in the melt season, a new record low this September is highly unlikely. A simple projection method developed by Walt Meier at the NASA Goddard Space Flight Center uses daily ice loss rates from previous years to estimate possible trajectories of ice extent through the rest of the melt season.

This approach yields a range of minimum values based on how sea ice loss progressed in previous years. By selecting from an average of multiple years, or using loss rates from a specific previous year, the method yields an estimate of the likely range of the minimum sea ice extent. As of August 14, using daily ice loss rates based on the 2006 to 2015 average yields an average projected 2016 minimum extent of 4.33 million square kilometers (1.67 million square miles). Using the slowest (recent) August to September decline, which occurred in 2006, yields a 2016 minimum of 4.76 million square kilometers (1.84 million square miles). Using the fastest rate of decline, from 2012, yields a 2016 minimum extent of 4.06 million square kilometers (1.57 million square miles). These two years bracket a reasonable range of expected 2016 minima. It is possible that this year will have decline rates that fall outside the range of previous years. However, this approach indicates that it is very unlikely that 2016 will have a minimum below 2012’s value of 3.39 million square kilometers (1.31 million square miles). A projection from August 1 was submitted to the Sea Ice Outlook.

Further reading

Lindsay, R.W. 1998. Temporal variability of the energy balance of thick Arctic pack ice, Journal of Climate, doi:10.1175/15200442(1998)011<0313:TVOTEB>2.0.CO;2.

Steele, M. and W. Ermold. 2015. Loitering of the retreating sea ice edge in the Arctic seas, Journal of Geophysical Research, doi:10.1002/2015JC011182.

Steele, M., J. Zhang, and W. Ermold. 2010. Mechanisms of summertime upper Arctic Ocean warming and the effect on sea ice melt, Journal of Geophysical Research, doi:10.1029/2009JC005849.

A cool and stormy Arctic in July

An extensive area of lower than average temperatures in the Central Arctic and the Siberian coast, attended by persistent low pressure systems in the same region, led to slightly slower than average sea ice decline through the month. The stormy pattern contributed to a dispersed and ragged western Arctic ice pack for July, with several polynyas beginning to form late in the month. A new record low September ice extent now appears to be unlikely.

Overview of conditions

Figure 1. Arctic sea ice extent for July 2016 was 8.13 million square kilometers (3.14 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 July 2016 averaged 8.13 million square kilometers (3.14 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 July averaged 8.13 million square kilometers (3.14 million square miles), the third lowest July extent in the satellite record. This makes July only the second month so far this year that did not have a record low extent. July’s extent is 190,000 square kilometers (73,000 square miles) above the previous record low set in 2011, and 1.65 million square kilometers (637,000 square miles) below the 1981 to 2010 long-term average.

Ice extent continues to be far below average in the Kara and Barents seas, as it has been throughout the winter and spring. Extent also remains well below average in the Beaufort Sea, but in the Laptev and East Siberian seas, sea ice extent is near average.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of August 1, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 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 2a. The graph above shows Arctic sea ice extent as of August 1, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 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
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Figure 2b. The plot above shows July 2016 Arctic air temperature anomalies at the 925 hPa level in degrees Celsius and sea level pressure anomalies. Yellows and reds indicate higher than average temperatures and pressure; blues and purples indicate lower than average temperatures and pressure.

Figure 2b. The plot above shows July 2016 Arctic air temperature anomalies at the 925 hPa level in degrees Celsius and sea level pressure anomalies. Yellows and reds indicate higher than average temperatures and pressure; blues and purples indicate lower than average temperatures and pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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The rate of ice loss during July 2016 was slightly below average at 83,800 square kilometers (32,400 square miles) per day. The 1981 to 2010 average rate of ice loss for July is 86,800 square kilometers (33,500 square miles) per day.

Warm conditions with temperatures at the 925 hPa level of 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) above average graced the northernmost coasts of Alaska, Canada, and Greenland, but the thick sea ice that is typical of this region is unlikely to melt out. Very warm conditions continued in the Kara and Barents seas, with temperatures as much as 3 to 6 degrees Celsius (5 to 11 degrees Fahrenheit) above average, consistent with the retreat of the ice cover to the northern edge of the Svalbard, Franz Josef, and New Siberian Islands. However, the main feature of the climate conditions for the month was a large area of below-average pressure centered over the Laptev Sea, and associated cooler than average conditions in the same area (1 to 4 degrees Celsius or 2 to 7 degrees Fahrenheit). This continues the pattern seen in June, with conditions unfavorable to pronounced sea ice retreat: cloudy and cool, with winds that tend to disperse the ice and increase its extent, rather than compact it.

July 2016 compared to previous years

Figure 3. Monthly July ice extent for 1979 to 2016 shows a decline of 7.3 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly July ice extent for 1979 to 2016 shows a decline of 7.3 percent per decade.

Credit: National Snow and Ice Data Center
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Through 2016, the rate of decline for the month of July is 72,700 square kilometers 28,070 square miles) per year, or 7.3 percent per decade. July extent remained above 2011 and 2012 levels throughout the month, but it was below the 2007 extent for the first half of the month.

A shift in pressure

Figure 4. These graphs show sea level pressure anomalies or differences from average sea level pressure in the Northern Hemisphere for April, May, June, and July 2016.

Figure 4. These graphs show sea level pressure anomalies or differences from average sea level pressure in the Northern Hemisphere for April, May, June, and July 2016.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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Beginning in June there was a significant change in the atmospheric circulation over the Arctic. May was characterized by high pressure over the Arctic Ocean which had persisted since the beginning of the year. However, in June the pattern shifted to lower than average pressure. This brought clouds and fairly low temperatures to the region, slowing ice loss. The change in circulation also shifted the pattern of ice motion, slowing the earlier movement of ice away from the coast in the Beaufort Sea (as depicted in our May 3rd post).

This pattern shift is associated with the development of a large and persistent area of moderate high pressure over the northeastern Pacific (south of Alaska) that formed beginning in mid-May. This may be related to an ongoing shift in the Pacific Decadal Oscillation over spring and early summer this year.

Sea ice dances to the changing wind

Figure 5a. These graphs Arctic sea ice motion for May 2 to 8, 2016 (top) and July 25 to 31, 2016 (bottom).

Figure 5a. These graphs show Arctic sea ice motion for May 2 to 8, 2016 (top) and July 25 to 31, 2016 (bottom).

Credit: NSIDC/University of Colorado, M. Tschudi, C. Fowler, J. Maslanik, W. Meier
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Figure 5b. This sea ice concentration image from the Advanced Microwave Scanning Radiometer 2 (AMSR2) shows dispersed sea ice and small polynyas in the Beaufort and East Siberian season July 27, 2016.

Figure 5b. This sea ice concentration image from the Advanced Microwave Scanning Radiometer 2 (AMSR2) shows dispersed sea ice and small polynyas in the Beaufort and East Siberian seas on July 27, 2016.

Credit: University of Bremen
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The shift in air pressure pattern also resulted in a change in sea ice drift directions in the Arctic. Early in the year, sea ice drift had a strong clockwise pattern (Figure 5a, top). However, July conditions greatly reduced sea ice drift speed in the Beaufort Sea and produced a counterclockwise drift pattern in the Laptev Sea (Figure 5a, bottom).

Persistent low pressure and repeated cyclonic storms in the Siberian side of the Arctic tended to disperse the pack and move it away from the coast. By late July, several regions of thin pack and small polynyas were beginning to open in these areas (Figure 5b).

The ice of our forefathers

Figure 6. These graphs show a best estimate of ice extent and sea ice departure from average for the period 1850 to 2013. The top figure shows winter and summer.

Figure 6. These graphs show a best estimate of ice extent and sea ice departure from average for the period 1850 to 2013. The top figure shows winter and summer.

Credit: NOAA at NSIDC
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Earlier this month, NOAA at NSIDC published a new compilation of Arctic sea ice extent using a variety of historical sources, including whaling ship reports and several historical ice chart series from Alaska, the Russian Arctic, Canada, and Denmark. The compilation provides a synthesized mid-monthly estimate extending back to 1850. The study concludes that the current downward trend in sea ice has no precedent in duration or scale of ice loss since 1850. With the exception of the Bering Sea, none of the areas have seen sea ice extents as low as in the past decade. Historical periods that show a decrease in summertime sea ice extent in the Arctic, such as the late 1930’s and 1940’s, are smaller in magnitude than the current downward-trending period.

Further reading

Walsh, J. E., F. Fetterer, J. S. Stewart, and W. L. Chapman. 2016. A database for depicting Arctic sea ice variations back to 1850. Geographical Review. doi: 10.1111/j.1931-0846.2016.12195.x.

Low ice, low snow, both poles

Daily Arctic sea ice extents for May 2016 tracked two to four weeks ahead of levels seen in 2012, which had the lowest September extent in the satellite record. Current sea ice extent numbers are tentative due to the preliminary nature of the DMSP F-18 satellite data, but are supported by other data sources. An unusually early retreat of sea ice in the Beaufort Sea and pulses of warm air entering the Arctic from eastern Siberia and northernmost Europe are in part driving below-average ice conditions. Snow cover in the Northern Hemisphere was the lowest in fifty years for April and the fourth lowest for May. Antarctic sea ice extent grew slowly during the austral autumn and was below average for most of May.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2016 was 12.0 million square kilometers (4.63 million square miles).

Figure 1. Arctic sea ice extent for May 2016 was 12.0 million square kilometers (4.63 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Provisional data. Not a Sea Ice Index product.

Credit: National Snow and Ice Data Center
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May 2016 set a new record low for the month for the period of satellite observations, at 12.0 million square kilometers (4.63 million square miles), following on previous record lows this year in January, February, and April. May’s average ice extent is 580,000 square kilometers (224,000 square miles) below the previous record low for the month set in 2004, and 1.39 million square kilometers (537,000 square miles) below the 1981 to 2010 long-term average.

During the month, daily sea ice extents tracked about 600,000 square kilometers (232,000 square miles) below any previous year in the 38-year satellite record. Daily extents in May were also two to four weeks ahead of levels seen in 2012, which had the lowest September extent in the satellite record. The monthly average extent for May 2016 is more than one million square kilometers (386,000 square miles) below that observed in May 2012.

Sea ice extent remains below average in the Kara and Barents seas, continuing the pattern seen throughout winter 2015 and 2016. Sea ice also remains below average in the Bering Sea and the East Greenland Sea. In the Beaufort Sea, large open water areas have formed near the coast and ice to the north is strongly fragmented due to wind-driven divergence. The opening began in February, continued through March, and greatly expanded in April.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of May 31, 2016, along with daily ice extent data for four previous years.

Figure 2. The graph above shows Arctic sea ice extent as of May 31, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Provisional data. Not a Sea Ice Index product.

Credit: National Snow and Ice Data Center
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The average ice loss during May 2016 was 61,000 square kilometers (23,600 square miles) per day. This was faster than the 1981 to 2010 long-term average rate of decline of 46,600 square kilometers (18,000 square miles) per day. May air temperatures at the 925 hPa level were 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) above the 1981 to 2010 average across most of the Arctic Ocean, with localized higher temperatures in the Chukchi Sea (4 to 5 degrees Celsius or 7 to 9 degrees Fahrenheit) and in the Barents Sea (4 degrees Celsius or 7 degrees Fahrenheit). Air pressure patterns were not particularly unusual, but two areas of southerly winds in northern Europe and Alaska pushed higher than average temperatures into the Arctic Ocean, producing hot spots noted above and generally above-average temperatures across the Arctic. Only over central Siberia were temperatures lower than the 1981 to 2010 average.

May 2016 compared to previous years

Figure 3. Monthly May Arctic sea ice extent for 1979 to 2016 shows a decline of 2.6% per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly May Arctic sea ice extent for 1979 to 2016 shows a decline of 2.6 percent per decade. Provisional data. Not a Sea Ice Index product.

Credit: National Snow and Ice Data Center
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Through 2016, the rate of decline for the month of May is 34,000 square kilometers (13,000 square miles) per year, or 2.6 percent per decade.

Thickness in the Beaufort Sea

Figure 4. The image above shows ice thickness measurements in the Beaufort Sea on April 9 and 10, 2016, superimposed on concurrent imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra and Aqua satellites.

Figure 4a. The image above shows ice thickness measurements in the Beaufort Sea on April 9 and 10, 2016, superimposed on concurrent imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra and Aqua satellites. Short black lines demarcate the boundary between first-year (south) and multiyear (north) regimes.

Credit: C. Haas, York University
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Figure 4b. This figure shows the difference between March ice thickness and the average of March 2011 to 2016. Data are from the European Space Agency's Cryosat-2 satellite.

Figure 4b. This figure shows the difference between March ice thickness and the average of March 2011 to 2016. Data are from the European Space Agency’s CryoSat-2 satellite.

Credit: R. Ricker, Helmholtz Centre for Polar and Marine Research, ESA
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Satellite and survey data show that ice thicknesses in parts of the Arctic are similar to those observed in 2015, but that ice thickness over the whole region is thinner compared to the last five years. Ice thickness surveys carried out by York University in early April 2016 show that thicknesses in the Northwest Passage are similar to that in 2015, though there is less multiyear ice in 2016. In the southern Beaufort Sea, the thickness of multiyear ice is also similar to the previous year, but because of strong divergence and export, first-year sea ice is considerably thinner than in 2015, giving rise to expectations of earlier melt out of this thin ice and formation of open water in 2016. Data from the European Space Agency’s CryoSat-2 satellite show that first-year ice in March 2016 is thinner compared to the March 2011 to 2016 average, especially in the Beaufort Sea (20 to 40 centimeters thinner) and the Barents and Kara seas (10 to 30 centimeters thinner). Multiyear ice north of Canada and Greenland is also thinner.

The thinner first year ice may partly explain the early development of open water in the southern Beaufort Sea for this month. The multiyear ice on the other hand may survive and slow down the overall retreat of the ice edge, as it did in 2015 when a band of multiyear ice survived throughout most of the summer. However, the multiyear ice regime this year seems more fragmented and interspersed with thinner first-year ice. When this thinner ice melts, dark open water areas may grow rapidly as energy is absorbed which in turn melts more ice and can accelerate multiyear ice decay.

Fragmented ice in the Beaufort Sea

Figure 5. The image above shows a May 21 view of Arctic sea ice in the Beaufort Sea from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. |

Figure 5. The image above shows a May 21, 2016 view of Arctic sea ice in the Beaufort Sea from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor.

Credit: Land Atmosphere Near-Real Time Capability for EOS (LANCE) System, NASA/GSFC
High-resolution image

As discussed in last month’s post, a large area in the Beaufort Sea shows a very fragmented ice cover as a result of strong wind-driven divergence throughout the late winter and spring. Figure 5 shows a MODIS visible-band image from May 21, 2016 for the southern Beaufort Sea, illustrating how the fragmentation has led to large multiyear ice floes surrounded by first-year ice and open water. The area of fragmented ice now nearly reaches the pole. While thick, multiyear ice can better survive the summer melt season, the early development of open water allows temperatures in the ocean mixed layer (top 20 meters) to rise, which may enhance lateral ice melt in that region. In summer 2007, early retreat of sea ice from the coasts of Siberia and Alaska, combined with unusual clear skies, led to enhanced melt of thick multiyear ice floes, some recording nearly 3 meters (10 feet) of bottom melt. If atmospheric conditions this summer are as favorable as they were in 2007, some of this multiyear ice may not survive the summer.

Report from the field: Barrow, Alaska

Figure 6a. Researchers use an auger to drill into the sea ice off Barrow, Alaska.

Figure 6a. Researchers use an auger to drill into the sea ice off Barrow, Alaska. After drilling a hole, they would then use a tape measure to record ice thickness.

Credit: W. Meier, NASA
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Figure 6b. NASA researcher Walt Meier stands in a melt pond on the sea ice off Barrow, Alaska.

Figure 6b. NASA researcher Walt Meier stands in a melt pond on the sea ice off Barrow, Alaska.

Credit: W. Meier, NASA
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NASA research scientist and NSIDC Arctic Sea Ice Analysis contributor Walt Meier spent the last week in Barrow, Alaska taking part in a National Science Foundation-funded sea ice camp and workshop. The goal was to bring together modelers, remote sensing scientists, and field researchers to understand each other’s work and to develop new ways to collaborate and combine knowledge about the Arctic sea ice system. As part of the camp, groups trudged onto the ice daily to take measurements. They found the ice to be quite thin at 80 to 100 centimeters (31 to 39 inches), compared to an average year when thicknesses would be 140 to 150 centimeters (55 to 59 inches). Melt ponds had already formed, though during cooler days, there was some refreezing as well. The residents of Barrow conveyed that it has been a very unusual winter. Normally, there is quite a bit of onshore wind from the west. This pushes the ice together and grounds pieces to the shallow shelf offshore, which helps stabilize the ice cover. However, this year the winds have been almost always from the east. This keeps the ice near the shore flat and undeformed (which the group observed during the camp) and opens up leads, or areas of open water, at the edge of the fast ice, which is clear in satellite imagery. This westward flow is a part of the larger Beaufort Gyre flow that has dominated the entire Beaufort and Chukchi sea region for much of the winter.

Record low snow

Figure 7. This snow cover anomaly map shows the percent difference between snow cover for May 2016 compared with average snow cover for May from 1971 to 2000. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than average.

Figure 7. This snow cover anomaly map shows the percent difference between snow cover for May 2016 compared with average snow cover for May from 1981 to 2010. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than average.

Credit: D. Robinson and T. Estilow, Rutgers University Global Snow Lab
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The Northern Hemisphere had exceptionally low snow coverage for both April and May of 2016 and a record low spring (March, April, and May), as reported from 50 years of mapping by Rutgers University’s Global Snow Lab. April’s snow cover was the lowest at 27.91 million square kilometers (10.78 million square miles), and May was the fourth lowest at 16.34 million square kilometers (6.3 million square miles).

The National Oceanic and Atmospheric Administration announced on May 20 that Barrow, Alaska recorded the earliest snowmelt (snow-off date) in 78 years of recorded climate history. Typically snow retreats in late June or early July, but this year the snowmelt began on May 13, ten days earlier than the previous record for that location set in 2002.

Below average sea ice in the Antarctic

Figure 8a. Antarctic sea ice extent for May 2016 was 10.6 million square kilometers (4.13 million square miles).

Figure 8a. Antarctic sea ice extent for May 2016 was 10.6 million square kilometers (4.13 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole. Provisional data. Not a Sea Ice Index product.

Credit: National Snow and Ice Data Center
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Figure 8b. The graph above shows Antarctic sea ice extent as of June 2, 2016, along with daily ice extent data for 2015. 2016 is shown in blue and 2015 in green. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data.

Figure 8b. The graph above shows Antarctic sea ice extent as of June 2, 2016, along with daily ice extent data for 2015. 2016 is shown in blue and 2015 in green. The 1981 to 2010 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

Sea ice extent in the Southern Hemisphere grew fairly slowly in May compared to the average, causing it to dip below the long-term average by the second half of the month. Antarctic sea ice extent for May 2016 averaged 10.70 million square kilometers (4.13 million square miles). This is 90,000 square kilometers (35,000 square miles) below the 1981 to 2010 long-term average of 10.79 million square kilometers (4.17 million square miles). Antarctic sea ice has been trending at near-average to below-average levels since June of 2015. In May 2016, extent was particularly low in the Bellingshausen Sea, Fimbul Ice Shelf area, and Wilkes Land Coast, but well above average in the northwestern Weddell Sea near the Antarctic Peninsula.

References

Haas, C. 2012. Airborne observations of the distribution, thickness, and drift of different sea ice types and extreme ice features in the Canadian Beaufort Sea, Proceedings of the Arctic Technology Conference ATC, Houston, Texas, December 3?5, 2012, Paper No. OTC 23812, 8 pp.

Haas, C., and S. E. L. Howell. 2015. Ice thickness in the Northwest Passage, Geophysical Research Letters, 42, doi:10.1002/2015GL065704.

Perovich, D. K., J. A. Richter-Menge, K. F. Jones and B. Light. 2008. Sunlight, water and ice: Extreme Arctic sea ice melt during the summer of 2007, Geophysical Research Letters, 35, L11501, doi:10.1029/2008GL034007.

 

March ends a most interesting winter

Low Arctic sea ice extent for March caps a highly unusual winter in the Arctic, characterized by persistent warmth in the atmosphere that helped to limit ice growth. Above-average influx of ocean heat from the Atlantic and southerly winds helped to keep ice extent especially low in the Barents and Kara seas. Northern Hemisphere snow cover for both February and March was also unusually low

Overview of conditions

Figure 1. Arctic sea ice extent for March 2016 was 14.43 million square kilometers (5.57 million square miles). The magenta line shows the 1981 to 2010 median extent for that month.

Figure 1. Arctic sea ice extent for March 2016 was 14.43 million square kilometers (5.57 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 reached its seasonal maximum on March 24 of 14.52 million square kilometers (5.607 million square miles), barely beating out February 25, 2015 for the lowest seasonal maximum in the satellite record. Arctic sea ice extent averaged for the entire month of March 2016 was 14.43 million square kilometers (5.57 million square miles), the second lowest in the satellite record. This is 1.09 million square kilometers (421,000 square miles) below the 1981 to 2010 average extent, and 40,000 square kilometers (15,000 square miles) above the record low monthly average for March that occurred in 2015. At the end of the month, extent remained well below average everywhere except in the Labrador Sea, Baffin Bay, and Hudson Bay. Ice extent was especially low in the Barents and Kara seas.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of April 3, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data.

Figure 2. The graph above shows Arctic sea ice extent as of April 3, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 2012 in purple. The 1981 to 2010 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

Because ice extent typically climbs through the first part of March until it reaches its seasonal maximum and then declines, the daily average ice growth rate for the month is typically quite small and is not a particularly meaningful number. This year’s seasonal maximum, while quite low, also occurred rather late in the month. Very early in the month, extent declined, raising anticipation that an early maximum had been reached. However, after a period of little change, extent slowly rose again, reaching the seasonal maximum on March 24.

March of 2016 saw unusually warm conditions over nearly all of the Arctic Ocean. Air temperatures at the 925 hPa level (about 3,000 feet above the surface) were typically 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average over the Arctic coastal seas, with larger positive departures compared to average nearer the Pole (4 to 8 degrees Celsius or 7 to 14 degrees Fahrenheit). This was associated with a pattern of above-average sea level pressures centered over the northern Beaufort Sea north of Alaska, and below-average pressures over the Atlantic side of the Arctic, especially pronounced over Baffin Bay and Davis Strait. Through March, the Arctic Oscillation Index bounced between moderate positive and negative values.

March 2016 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2016 shows a decline of 2.7 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly March ice extent for 1979 to 2016 shows a decline of 2.7 percent per decade.

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

Arctic sea ice extent averaged for March 2016 was the second lowest in the satellite record. Through 2016, the linear rate of decline for March extent is 2.7 percent per decade, or a decline of 42,100 square kilometers (16,200 square miles) per year.

The winter in review

Figure 4. This graph shows differences in Arctic sea ice from December 28, 2015 to January 4, 2016, estimated from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).

Figure 4. This graph shows differences in Arctic sea ice thickness from December 28, 2015 to January 4, 2016, estimated from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).

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

Figure 5. This figure shows observed (blue columns) and predicted (cyan) winter sea ice area in the Barents Sea. The prediction is based on observed Atlantic heat entering the Barents Sea and the sea ice area the previous year. The predicted sea ice area for this winter (2016) is well below average, and less than that observed for 2015. Anomalously strong southerly winds have also contributed to the very small sea ice area this winter (not shown).

Figure 5. This figure shows observed (blue columns) and predicted (cyan) winter sea ice area in the Barents Sea. The prediction is based on observed Atlantic heat entering the Barents Sea and the sea ice area the previous year. The predicted sea ice area for this winter (2016) is well below average, and less than that observed for 2015. Anomalously strong southerly winds have also contributed to the very small sea ice area this winter (not shown).

Credit: Ingrid Onarheim/Bjerknes Centre for Climate Research
High-resolution image

Figure 6. This snow cover anomaly map shows the difference between snow cover for March 2016, compared with average snow cover for March from 1981 to 2010. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than average.||Credit: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab| High-resolution image

Figure 6. This snow cover anomaly map shows the percent difference between snow cover for March 2016, compared with average snow cover for March from 1981 to 2010. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than average.

Credit: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab
High-resolution image

Figure 7. This graph shows snow cover extent anomalies in the Northern Hemisphere for March from 1967 to 2016. The anomaly is relative to the 1981 to 2010 average.

Figure 7. This graph shows snow cover extent anomalies in the Northern Hemisphere for March from 1967 to 2016. The anomaly is relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab
High-resolution image

The unusual warmth for March of 2016 continues a pattern of above-average temperatures for most of the Arctic and much of the Northern Hemisphere that has characterized the entire winter. As an exclamation point on the unusual warmth, there was a brief weather event at the very end of December 2015 when air temperatures near the Pole nearly reached the melting point. As we noted in our January post, the event was related to a pulse of warm air moving almost due south to north from the sub-tropical Atlantic to the regions north of Svalbard, an atmospheric river set between broad high and low pressure areas in Europe and the north Atlantic.

The December event also led to higher than average air temperatures over the Kara and Barents seas, reducing the sea ice concentration and causing thinning of the ice that was there. While sea ice normally grows and thickens over winter, the difference in thickness estimated from Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) shows that between December 28, 2015 and January 4, 2016, sea ice within the Kara and Barents seas thinned by more than 30 centimeters (Figure 4). Thinning also occurred north of Greenland and off the coast of Siberia, while the ice thickened over most of the Arctic Ocean. Higher than average temperatures remained in the region after the weather event had passed, which may have further prevented the ice from growing back. The reasons for the persistent warmth over the entire Arctic this past winter are currently under investigation; a link with the strong El Niño pattern of this winter may be involved.

While the warm atmospheric conditions played a role in the low ice extent for March 2016, the especially low extent that has persisted in the Barents and Kara seas appears to be linked with another heat source—an influx of warm Atlantic waters, entering between Bear Island and Norway (the Barents Sea opening). Ingrid Onarheim from the Bjerknes Centre for Climate Research in Bergen, Norway has been studying this issue and predicted a small sea ice cover in the Barents Sea this winter based on observed Atlantic heat transport to the Barents Sea through April 2015 (Figure 5). In addition to the above-average ocean heat transport, prevailing southerly winds have pushed the sea ice northward since November 2015, bringing in warm air that damps the normally high ocean-air heat loss and favoring ice formation. This likely contributed to the below-average ice conditions in the Arctic this winter. Atlantic heat transport due to near-surface ocean currents reached a long-term maximum in the mid-2000s. Several studies have suggested a more moderate inflow of Atlantic waters may characterize the years ahead, leading to increases in the Barents Sea ice cover in the coming years.

Along with low sea ice extent and above-average temperatures, March of 2016 also saw a very low monthly snow cover extent for the Northern Hemisphere (Figures 6 and 7). Snow cover was low across northern Eurasia, with only minor areas of above-average snow cover in western Turkey, northern Kazakhstan and Mongolia, and easternmost High-Mountain Asia. In North America, snow cover was low across nearly all of the coterminous 48 states in the U.S., despite a series of storms late in the month in the central Rockies and Great Plains. Overall, March 2016 had 37.16 million square kilometers (14.35 million square miles) of snow cover extent, 2.97 million square kilometers (1.15 million square miles) below the 1981 to 2010 average of 40.13 million square kilometers (15.50 million square miles). This makes March 2016 the 49th lowest out of 50 years on record in snow cover extent for the Northern Hemisphere. While April and May could still bring snow to the higher latitudes, we note that low snow cover, similar to low sea ice cover, leads to greater heat absorption by the surface in the Arctic and further warming as we move toward summer.

A younger ice cover

Figure 8. These graphs show Arctic sea ice age from March 4 to 10, 2016. The top graph shows ice age distribution for that week alone and the bottom graph shows ice age distribution for that week from 1985 to 2016.||Credit: NSIDC courtesy University of Colorado Boulder, M. Tschudi, C. Fowler, J. Maslanik, R. Stewart, W. Meier.

Figure 8. These graphs show Arctic sea ice age from March 4 to 10, 2016. The top graph shows ice age distribution for that week alone and the bottom graph shows ice age distribution for that week from 1985 to 2016.

Credit: NSIDC courtesy University of Colorado Boulder, M. Tschudi, C. Fowler, J. Maslanik, R. Stewart, W. Meier.
High-resolution image

Ice age data for mid-March shows that 70 percent of the sea ice within the Arctic basin consists of first-year ice and only 30 percent is multiyear ice. First-year ice is generally only 1.5 to 2 meters (5 to 6.5 feet) thick. This implies a thinner ice pack as the melt season gets underway. In addition, the oldest ice, or ice at least 5 years or older, is at its smallest level in the satellite record, representing only 3 percent of the total ice cover. Some of this very old ice is found in the western Beaufort Sea and extending towards the Chukchi Sea regions where we have seen large summer ice losses in recent years. Typically this old ice is concentrated north of Greenland and within the Canadian Arctic Archipelago.

Not only is the oldest ice at record low levels, but it it is not recovering. Beginning 2007, we see a strong decline that lasts until 2012 and has not changed much since. If anything it has gone down. In that time we have seen some recovery in younger multiyear ice types: e.g., 2-year ice jumped back up after a one-year minimum, 3-year ice recovered to a lesser degree, and 4-year ice to an even lesser degree. It is not surprising to see some recovery and that first-year ice recovery propagates through time. However, that recovery happens less as the ice gets older, and for 5-year ice and older there is essentially no recovery. The bottom line is that ice no longer survives in the Arctic for very long. It is lasting three to four years tops before melting or advecting out through Fram Strait. This is a big change from the past when much of the ice cover would survive upwards of a decade.

Southern view

Antarctic sea ice grew rapidly in March, rising from below-average daily extents to above-average extents during the month, and increasing by nearly 90,000 square kilometers (35,000 square miles) per day. Sea ice growth was particularly fast in the eastern Ross Sea. Winter temperatures on the continent through the month were near-average overall, but 4 to 6 degrees Celsius (7 to 11 degrees Fahrenheit) below average over the eastern Ross Sea and West Antarctic Ice Sheet.

 

Another record low for Arctic sea ice maximum winter extent

Arctic sea ice appears to have reached its annual maximum extent on March 24, and is now the lowest maximum in the satellite record, replacing last year’s record low. This year’s maximum extent occurred later than average. A late season surge in ice growth is still possible. NSIDC will post a detailed analysis of the 2015 to 2016 winter sea ice conditions in early April.

Overview of conditions

Figure 1. Arctic sea ice extent for March 24, 2016 was 14.52 million square kilometers (5.607 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 March 24, 2016, Arctic sea ice likely reached its maximum extent for the year, at 14.52 million square kilometers (5.607 million square miles). This year’s maximum ice extent was the lowest in the satellite record, with below-average ice conditions everywhere except in the Labrador Sea, Baffin Bay, and Hudson Bay. The maximum extent is 1.12 million square kilometers (431,000 square miles) below the 1981 to 2010 average of 15.64 million square kilometers (6.04 million square miles) and 13,000 square kilometers (5,000 square miles) below the previous lowest maximum that occurred last year. This year’s maximum occurred twelve days later than the 1981 to 2010 average date of March 12. The date of the maximum has varied considerably over the years, occurring as early as February 24 in 1996 and as late as April 2 in 2010.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 27, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 2012 in purple. The 1981 to 2010 average is in dark gray.

Figure 2. The graph above shows Arctic sea ice extent as of March 27, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 2012 in purple. The 1981 to 2010 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

Sea ice extent was below average throughout the Arctic, except in the Labrador Sea, Baffin Bay, and Hudson Bay. However, it was especially low in the Barents Sea. Below average winter ice conditions in the Kara and Barents seas have been a persistent feature in the last several years, while the Bering Sea has overall seen slightly positive trends towards more sea ice during winter.

Below average sea ice extent is in part a result of higher than average temperatures that have plagued the Arctic all winter. Air temperatures at the 925 hPa level from December 2015 through February 2016 were above average everywhere in the Arctic, with hotspots near the Pole and from the Kara Sea towards Svalbard exceeding 6 Celsius degrees (11 degrees Fahrenheit) above average. These higher than average temperatures continued into March, with air temperatures during the first two weeks reaching 6 degrees Celsius (11 degrees Fahrenheit) above average in a region stretching across the North Pole toward northern Greenland, and up to 12 degrees Celsius (22 degrees Fahrenheit) above average north of Svalbard.

These unusually warm conditions have no doubt played a role in the record low ice extent this winter. Another contributing factor has been a predominance of southerly winds in the Kara and Barents seas that have helped to keep the ice edge northward of its typical position. This area has also seen an influx of warm Atlantic waters from the Norwegian Sea.

There is little correlation between the maximum winter extent and the minimum summer extent—this low maximum does not ensure that this summer will see record low ice conditions. A key factor is the timing of widespread surface melting in the high Arctic. An earlier melt onset is important to the amount of energy absorbed by the ice cover during the summer. If surface melting starts earlier than average, the snow darkens and exposes the ice below earlier, which in turn increases the solar heat input, allowing more ice to melt. With the likelihood that much of the Arctic cover is somewhat thinner due to the warm winter, early surface melting would favor reduced summer ice cover.

Final analysis pending

At the beginning of April, NSIDC scientists will release a full analysis of winter conditions, along with monthly data for March. For more information about the maximum extent and what it means, see the NSIDC Icelights post, the Arctic sea ice maximum.

 

February continues streak of record low Arctic sea ice extent

Arctic sea ice was at a satellite-record low for the second month in a row. The first three weeks of February saw little ice growth, but extent rose during the last week of the month. Arctic sea ice typically reaches its maximum extent for the year in mid to late March.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2016 was 14.2 million square kilometers (5.48 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 February 2016 was 14.22 million square kilometers (5.48 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 February averaged 14.22 million square kilometers (5.48 million square miles), the lowest February extent in the satellite record. It is 1.16 million square kilometers (448,000 square miles) below the 1981 to 2010 long-term average of 15.4 million square kilometers (5.94 million square miles) and is 200,000 square kilometers (77,000 square miles) below the previous record low for the month recorded in 2005.

The first three weeks of February saw little ice growth, but extent rose during the last week of the month primarily due to growth in the Sea of Okhotsk (180,000 square kilometers or 70,000 square miles) and to a lesser extent in Baffin Bay (35,000 square kilometers or 13,500 square miles). Extent is presently below average in the Barents and Kara seas, as well as the Bering Sea and the East Greenland Sea. Extent decreased in the Barents and East Greenland seas during the month of February. In other regions, such as the Sea of Okhotsk, Baffin Bay, and the Labrador Sea, ice conditions are near average to slightly above average for this time of year. An exception is the Gulf of St. Lawrence, which remains largely ice free.

In the Antarctic, sea ice reached its minimum extent for the year on February 19, averaging 2.6 million square kilometers (1 million square miles). It is the ninth lowest Antarctic sea ice minimum extent in the satellite record.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of March 1, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 2012 in purple.

Figure 2a. The graph above shows Arctic sea ice extent as of March 1, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 2012 in purple. The 1981 to 2010 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 2b. These three images show two-week average Arctic sea ice drift data from January through mid-February derived from the Advanced Microwave Scanning Radiometer 2 (AMSR-2). The image on the left shows the period January 1 to 15, the middle image shows January 14 to 31, and the image on the right shows February 1 to 16. ||Images courtesy Alek Petty/NASA Goddard Space Flight Center/University of Maryland, data from Centre ERS d'Archivage et de Traitement (CERSAT)/French Institute for Exploration (Ifremer)| High-resolution image

Figure 2b. These three images show two-week average Arctic sea ice drift data from January through mid-February derived from the Advanced Microwave Scanning Radiometer 2 (AMSR-2). The image on the left shows the period January 1 to 15, the middle image shows January 14 to 31, and the image on the right shows February 1 to 16.

Credit: Alek Petty/NASA Goddard Space Flight Center/University of Maryland, data from Centre ERS d’Archivage et de Traitement (CERSAT)/French Institute for Exploration (Ifremer)
High-resolution image

NASA and NOAA announced that January 2016 was the ninth straight month of record-breaking high surface temperatures for the globe. In terms of regional patterns, the Arctic stands out, with surface temperatures more than 4 degrees Celsius (7.2 degrees Fahrenheit) above the 1951 to 1980 average. These high temperatures were in part responsible for the record low sea ice extent observed for January. Persistent warmth has continued into February; air temperatures at the 925 hPa level were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) above the 1981 to 2010 average over the central Arctic Ocean near the pole. The rate of ice growth for February was near average at 19,700 square kilometers (7,600 square miles) per day, compared to 20,200 square kilometers (7,800 square miles) per day for the 1981 to 2010 average.

Atmospheric circulation patterns have also favored low sea ice extent, particularly in the Barents and Kara seas. Ice motion drift data derived from the Advanced Microwave Scanning Radiometer 2 (AMSR2) satellite and provided by the Centre ERS d’Archivage et de Traitement (CERSAT) show that since January 1, there has been cyclonic, or counterclockwise, sea ice motion in the Barents Sea helping to keep sea ice from advancing south. During the second half of January, an anti-cyclonic, or clockwise, circulation pattern developed in the Beaufort Sea, which subsequently strengthened and expanded to include most of the Arctic Ocean. This, combined with high pressure over Greenland and low pressure over Spitsbergen, has favored enhanced ice export out of Fram Strait, helping to flush old, thick ice out of the Arctic Ocean, leaving behind thinner ice that is more apt to melt away in summer. Whether this circulation pattern will continue and set the stage for very low September sea ice extent remains to be seen.

February 2016 compared to previous years

Figure 3. Monthly February sea ice extent for 1979 to 2016 shows a decline of 3.04% per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly February sea ice extent for 1979 to 2016 shows a decline of 3.0 percent per decade.

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

February 2016 sea ice extent was the lowest in the satellite record at 14.22 million square kilometers (5.48 million square miles). The linear rate of decline for February is now 3.0 percent per decade.

Record warmth revealed by the AIRS instrument

Figure 4. These two images show February 2016 departures from the 2003 to 2015 average for 925 hPa air temperature (left) and precipitable water (right) as derived from the NASA AIRS instrument.||Images courtesy Linette Boisvert/NASA Goddard Space Flight Center.| High-resolution image

Figure 4. These two images show February 2016 departures from the 2003 to 2015 average for 925 hPa air temperature (left) and precipitable water (right) as derived from the NASA AIRS instrument.

Credit: Linette Boisvert/NASA Goddard Space Flight Center
High-resolution image

Since 2003, the Atmospheric Infrared Sounder (AIRS) onboard the NASA Aqua satellite has collected daily temperature and humidity profiles globally. Although the record is fairly short, AIRS data can provide insight into recent changes in Arctic climate. February average air temperatures, measured by AIRS at 925 hPa, are around 5 degrees Celsius (9 degrees Fahrenheit) above the 2003 to 2015 average over the Beaufort and Chukchi seas and the central Arctic Ocean. Above-average temperatures are also the rule over the Kara Sea and Northern Siberia (6 degrees Celsius or 11 degrees Fahrenheit above average). Regions with especially higher than average temperatures correspond to regions of low sea ice, demonstrating the role played by heat fluxes from open water areas. For example, the Sea of Okhotsk experienced below-average air temperatures, and also had above-average sea ice extents, whereas the Kara, Barents, and Bering seas and the Gulf of St. Lawrence had higher air temperatures compared to average, which coincides with lower than average sea ice extent.

A similar relationship is seen in the total precipitable water for February 2016. Precipitable water is the amount of water vapor in the atmospheric column totaled from the surface to the top of the troposphere, expressed as kilograms of water per square meter (one kilogram per square meter equals 1 millimeter of water depth). In February, areas with precipitable water between 12 percent (Bering Sea) to 70 percent (Kara Sea) above the 2003 to 2015 February average corresponded to regions with below-average sea ice extent. Water vapor is a greenhouse gas, and with more water vapor in the air, there is a stronger emission of longwave radiation to the surface. Conversely, the observation that above-average amounts of water vapor are found over areas of reduced sea ice extent points to a role of local evaporation, and evaporation is a cooling process that by itself will favor ice growth.

A late freeze-up

Figure 5. This images shows freeze-up anomalies in the Arctic for 2015. Reds indicate areas where freeze-up began later than average and blues indicate freeze-up beginning earlier than average.||Credit: National Snow and Ice Data Center, data provided by J. Miller/T. Markus, NASA Goddard Space Flight Center I High-resolution image

Figure 5. This images shows freeze-up anomalies in the Arctic for 2015. Reds indicate areas where freeze-up began later than average and blues indicate freeze-up beginning earlier than average.

Credit: National Snow and Ice Data Center, data provided by J. Miller/T. Markus, NASA Goddard Space Flight Center
High-resolution image

Sea ice reformed or refroze later than average throughout most of the Arctic, especially in the Kara and Barents seas where the freeze-up happened about two months later than average. Ice was also late to form in the Beaufort, Chukchi, East Siberian, and Laptev seas, between ten and forty days later than average. In contrast, the timing of freeze-up over the central Arctic Ocean near the pole was near average, as was also the case in Baffin Bay and parts of Hudson Bay. When freeze-up happens late, the ice has less time to thicken before the melt season starts, leading to a thinner ice cover that is more prone to melting out in summer.

References

NASA Goddard Institute for Space Studies. Global Land-Ocean Temperature Index in 0.01 degrees Celsius. http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt.

NASA Goddard Institute for Space Studies. NASA, NOAA Analyses Reveal Record-Shattering Global Warm Temperatures in 2015. http://www.giss.nasa.gov/research/news/20160120.

National Oceanic and Atmospheric Administration. Global Analysis – January 2016. https://www.ncdc.noaa.gov/sotc/global/201601.

 

2015 in review

December ended with Arctic sea ice extent tracking between one and two standard deviations below average, as it did throughout the fall. This caps a year that saw the lowest sea ice maximum in February and the fourth lowest minimum in September. In Antarctica, December sea ice extent was slightly above average but far below the exceptionally large ice extents recorded for December 2013 and 2014. A slow-down in the rate of Antarctic sea ice growth in July was followed by near-average extents in the subsequent months. The first week of 2016 has seen very slow ice growth in the Arctic.

Overview of conditions

Figure 1. Arctic sea ice extent for December 2015 was 12.3 million square kilometers (4.74 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 December 2015 was 12.3 million square kilometers (4.74 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 December 2015 averaged 12.3 million square kilometers (4.74 million square miles), the fourth lowest December extent in the satellite record. This is 780,000 square kilometers (301,000 square miles) below the 1981 to 2010 average for the month, and 260,000 square kilometers (100,000 square miles) above the record low for December recorded in the year 2010. The rate of sea ice growth slowed slightly through the month and nearly ceased advancing in the first days of the new year, perhaps related to a period of unusual warmth (see below). The ice is currently tracking near two standard deviations below the 1981 to 2010 long-term average. Sea ice extent is well below average in the Bering, Okhotsk, and Barents seas, partly balanced by slightly above average extent in Baffin Bay.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of January 5, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 2012 in purple. The 1981 to 2010 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 January 5, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 2012 in purple. The 1981 to 2010 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 2b. These graphs show average sea level pressure and air temperature anomalies at 925 mb (about 3,000 feet above sea level) for December 2015.||Credit: NSIDC courtesy NOAA Earth

Figure 2b. These graphs show average sea level pressure and air temperature anomalies at 925 millibars (about 3,000 feet above sea level) for December 2015.

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

Arctic sea ice growth for December averaged 65,000 square kilometers (25,000 square miles) per day compared to the long-term average of 64,000 square kilometers (24,700 square miles) per day. Cool conditions at the 925 hPa level (2 to 4 degrees Celsius or 4 to 7 degrees Fahrenheit below average) existed in Baffin Bay, the Alaskan North Slope, and parts of eastern Siberia. A broad area of Europe and western Russia, including the northern Barents Sea, saw temperatures as much as 4 to 8 degrees Celsius (7 degrees to 14 degrees Fahrenheit) above average at the 925 hPa level. Conditions were also fairly warm over the central Arctic Ocean, north of the Canadian Arctic Archipelago. Sea level pressure was below average over much of the Arctic, especially from the northern North Atlantic to the Barents Sea and central Russia, and from the Bering Sea and south along the Canadian Pacific coast (7.5 to 12 millibars below average). This is consistent with the positive phase of the Arctic Oscillation through most of the month, a pattern that has persisted since the end of October.

December 2015 compared to previous Decembers

Figure 3. Monthly December ice extent for 1979 to 2015 shows a decline of 3.4% per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly December ice extent for 1979 to 2015 shows a decline of 3.4% per decade.

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

Arctic sea ice extent averaged for December 2015 was the fourth lowest in the satellite record. Through 2015, the linear rate of decline for December extent is 3.4% per decade, or -44,200 square kilometers (-17,000 miles) per year.

 

2015 in review

The year will be remembered for three major events in sea ice extent: the lowest Arctic maximum in the satellite record, the fourth lowest Arctic minimum in the satellite record, and a return to average levels for Antarctic sea ice extent after more than two years of record and near-record highs.

The record-low Arctic maximum occurred on February 25, 2015 and was among the earliest seasonal maxima in the 37-year satellite record. It was likely a result of very warm conditions in the Sea of Okhotsk and the Barents Sea (4 degrees Celsius or 7 degrees Fahrenheit above average), and low ice extent in the Bering Sea in March (when the maximum would more typically occur). These climate conditions were related to an unusual jet stream pattern as discussed in our April 7, 2015 post.

The fourth lowest Arctic minimum occurred on September 11, 2015 and was likely a consequence of very warm conditions in July and an increasingly young and thin ice cover. The thinner ice is consistent with a tendency in recent years for large polynyas that appear in the Beaufort and Chukchi seas in late summer. Although measurements by the CryoSat-2 satellite indicated that Arctic sea ice was thicker in 2015 compared to pre-2012 thicknesses, the ice behaved as though it was still quite thin.

From February 2013 through June 2015, Antarctic sea ice was at record or near-record daily extents. Antarctic sea ice set consecutive record winter maxima in 2012, 2013 and 2014. (Contrary to 2013 and 2014, autumn and spring conditions in 2012 were near-average.) But during this year’s austral mid-winter period, Antarctic sea ice growth slowed. Since then, extent in the Southern Hemisphere has generally been slightly above average. Climate effects from the building El Niño likely caused the shift during austral mid-winter. A strong El Niño is associated with a change in the position and strength of a major low pressure pattern near West Antarctica, called the Amundsen Sea Low. Weakening of the Amundsen Sea Low, and related impacts elsewhere around the ice edge in Antarctica, tend to reduce ice extent in the Ross Sea, eastern Weddell Sea, and elsewhere around Antarctica except near the Antarctic Peninsula.

The longer view

This graph shows sea ice concentration trends in the Arctic and the Antarctic for March to September for the years 1979 to 2015. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 4. This graph shows sea ice concentration trends in the Arctic and the Antarctic for March to September for the years 1979 to 2015. Sea Ice Index data. About the data

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

The satellite passive microwave record for sea ice now spans more than 37 years. As we have documented, clear downward trends characterize Arctic sea ice extent and concentration in all months, while somewhat less emphatic upward trends characterize Antarctic sea ice extent and concentration. A look at the geographic distribution of trends for the seasonal maximum and minimum periods provides insight into how the polar regions are changing. During the Arctic maximum, declines in extent and concentration are pronounced in the Barents Sea and Sea of Okhotsk, but ice cover has increased slightly in the Bering Sea. During the Arctic summer minimum, all areas show negative trends.

Antarctica presents a more mixed picture. During the Antarctic summer minimum, ice cover is increasing around much of the coastline from the Weddell Sea eastward to the western Ross Sea, but is declining sharply in the eastern Ross, Amundsen, and southern Bellingshausen seas. Winter ice cover in Antarctica is characterized by increases in the northern Ross Sea and the Indian Ocean sectors, and decreases in the northwestern Weddell Sea and the region south of Australia.

Ringing in the New Year with a brief polar heat wave

Figure 5. These graphs show average sea level pressure and air temperature anomaly at 925 mb (an altitude of about 3,000 feet) for 30 and 31 December, 2015.

Figure 5. These graphs show average sea level pressure and air temperature anomalies at 925 millibars (about 3,000 feet above sea level) for 30 and 31 December, 2015. The graphs are the average of two days, so the extremes in air pressure and temperature during this period are not shown.

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

An exceptional weather event during the last days of the year brought a heat wave with surface air temperatures up to 23 degrees Celsius (50 degrees Fahrenheit) above average in the far north, and a brief period when surface temperatures at the North Pole approached or perhaps even exceeded the freezing mark. A temperature of +0.7 degrees Celsius was briefly recorded by a buoy weather station near the North Pole on December 30, 2015. The event was linked to the combination of a very strong low pressure system near Iceland and a somewhat less intense low pressure system located near the North Pole. This was associated with an amplified trough at 500 hPa over the northern North Atlantic and a pronounced ridge of high pressure at 500 hPa to the east over central Europe, extending into the Kara Sea. This created a strong, deep inflow of warm, moist air into the Arctic Ocean’s high latitudes. The low near Iceland strengthened rapidly in the last days of December, reaching a minimum pressure of 935 millibars, equivalent to a hurricane. While the event was remarkable and may account for the slow ice growth during the first few days of January 2016, it was short lived and is unlikely to have any long-term effects on the sea ice cover.

Further reading

Tilling, R. L., A. Ridout, A. Shepherd, D. J. Wingham. 2015. Increased Arctic sea ice volume after anomalously low melting in 2013. Nature Geoscience 8, 643–646, doi:10.1038/ngeo2489.

Thompson, A. “What happened to the Polar Vortex?” ClimateCentral.com. http://www.climatecentral.org/news/what-happened-to-the-polar-vortex-19866?

Winter is coming to the Arctic

While Arctic sea ice extent is increasing, total ice extent remains below average, tracking almost two standard deviations below the long-term average.

Overview of conditions

Figure 1. Arctic sea ice extent for October 2015 was 7.72 million square kilometers (2.98 million square miles).

Figure 1. Arctic sea ice extent for October 2015 was 7.72 million square kilometers (2.98 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 October 2015 averaged 7.72 million square kilometers (2.98 million square miles), the sixth lowest October in the satellite record. This is 1.19 million square kilometers (460,000 square miles) below the 1981 to 2010 average extent, and 950,000 square kilometers (367,000 square miles) above the record low monthly average for October that occurred in 2007.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of November 2, 2015, along with daily ice extent data for four previous years.

Figure 2. The graph above shows Arctic sea ice extent as of November 2, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 in purple. The 1981 to 2010 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

Air temperatures at the 925 millibar level were 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) above average over the central Arctic, extending towards Fram Strait. This appears to be due to unusually low pressure over northwest Greenland and higher pressures over the Tamyr Peninsula and Scandinavia, which funneled warm air from the south into the central Arctic Ocean. Coastal regions were generally 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) higher than average.

October 2015 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2015 shows a decline of 6.9%

Figure 3. Monthly October ice extent for 1979 to 2015 shows a decline of 6.9% per decade.

Credit: National Snow and Ice Data Center
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Through 2015, the October sea ice extent has declined 6.9% per decade over the satellite record.

New sea ice thickness information back for the winter

Figure 4a. This image from CryoSat-2 shows thin ice (less than 1 meter (3.28 feet) over a wide area north of Greenland.||Credit: Center for Polar Observation and Modeling (CPOM) at University College London| High-resolution image

Figure 4a. This image from CryoSat-2 shows thin ice (less than 1 meter, or 3 feet, thick) over a wide area north of Greenland.

Credit: Center for Polar Observation and Modeling (CPOM) at University College London
High-resolution image

Figure 4b. This image from the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite shows sea ice thickness in the Arctic Ocean, including north and east of Greenland.||Credit: University of Hamburg Integrated Climate Data Center| High-resolution image

Figure 4b. This image from the European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) satellite shows sea ice thickness over the Arctic Ocean.

Credit: University of Hamburg Integrated Climate Data Center
High-resolution image

In recent years, two European Space Agency (ESA) satellites, CryoSat-2 and SMOS (Soil Moisture and Ocean Salinity), have been providing information on sea ice thickness. Thickness information is valuable for assessing the overall condition of the sea ice cover. The sensors on these satellites cannot determine thickness during the summer melt season, but now that freeze-up has begun, information is again available.

CryoSat-2, launched in 2010, is a radar altimeter, which measures the height of the ice cover above the sea surface. Used with additional information on snow cover and its density, the height information can be converted into estimates of ice thickness. The Center for Polar Observation and Modeling (CPOM) at University College London has again started providing near-real-time maps of sea ice thickness from CryoSat-2.

While these maps are valuable in providing near-real-time thickness estimates, converting the satellite measurements into thickness involves complex processing and there are many uncertainties. For example, Figure 4a depicts thin ice (less than 1 meter [3 feet]) over a wide area north of Greenland, an area where wind and ocean current patterns push the ice against the coast forming thick ridges and an extremely rough surface. This area has been shown by other studies to have some of the thickest sea ice in the Arctic, often exceeding 4 meters (13 feet). This ridging may have cause the difficulty in the current mapping.

CryoSat-2 also has difficulty retrieving thickness in very thin sea ice regions, resulting in no thickness values reported at the outer edge of the ice cover. SMOS is a microwave imaging radiometer that measures microwave brightness temperature at a range that is sensitive to thin ice (1.4 gigahertz). These data are also now available in near-real-time at the University of Hamburg Integrated Climate Data Center. SMOS cannot estimate thickness beyond 1 meter (3.28 feet) at most and often not beyond 0.5 meters (1.64 feet). While the map shows a wide region of 1 meter-thick ice, it is important to realize that this is just the maximum allowable value and in reality there is thicker ice over much of the region. However, SMOS provides valuable information on the coverage of thin ice during the winter ice growth season. Ideally, a blended CryoSat-2/SMOS product will provide more comprehensive information on thickness.

A large ozone hole over the Antarctic

Figure 5. The image above shows the ozone hole over Antarctica on October 2, 2015 when it had reached its largest single-day area for the year.

Figure 5. The image above shows the ozone hole over Antarctica on October 2, 2015 when it had reached its largest single-day area for the year, spanning 28.2 million square kilometers (10.9 million square miles). Data are from the Ozone Monitoring Instrument (OMI) on the NASA Aura satellite and the Ozone Monitoring and Profiler Suite (OMPS) on the NASA-NOAA Suomi NPP satellite.

Credit: NASA Earth Observatory, Ozone Hole Watch
High-resolution image

While sea ice in Antarctica is near average, the ozone hole over the continent grew relatively large during the austral winter. This goes against the expected trend towards a smaller ozone hole since the use of chlorofluorocarbons (CFCs) was banned in 1996. The size of the hole in a given year depends on several factors, including temperatures in the high altitude stratosphere. Temperatures in the Antarctic stratosphere were low this year, aiding chemical processes that destroy ozone. For more information on this year’s ozone hole see this NASA Earth Observatory feature.

 

Arctic sea ice reaches fourth lowest minimum

On September 11, Arctic sea ice reached its likely minimum extent for 2015. The minimum ice extent was the fourth 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. In the Antarctic, sea ice extent is average, a substantial contrast with recent years when Antarctic winter extents reached record high levels.

Please note that this is a preliminary announcement. Changing winds or late-season melt could still reduce the Arctic ice extent, as happened in 2005 and 2010. NSIDC scientists will release a full analysis of the Arctic melt season, and discuss the Antarctic winter sea ice growth, in early October.

Overview of conditions

Figure 1. Arctic sea ice extent for September 11, 2015 was 4.41 million square kilometers (1.70 million square miles). The orange line shows the 1981 to 2010 average extent for the 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

Figure 1. Arctic sea ice extent for September 11, 2015, was 4.41 million square kilometers (1.70 million square miles). The orange line shows the 1981 to 2010 average extent for the 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 11, 2015, sea ice extent dropped to 4.41 million square kilometers (1.70 million square miles), the fourth lowest minimum in the satellite record. This appears to be 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 four days earlier than the 1981 to 2010 average minimum date of September 15. The extent ranked behind 2012 (lowest), 2007 (second lowest), and 2011 (third lowest). Moreover, the nine lowest extents in the satellite era have all occurred in the last nine years.

Both the Northern Sea Route, along the coast of Russia, and Roald Amundsen’s route through the Northwest Passage are open. How long they remain open depends on weather patterns and the amount of heat still present in the ocean mixed layer (about the top 50 feet of the ocean). The deeper and wider Northwest Passage route through Parry Channel, which consists of M’Clure Strait, Barrow Strait, and Lancaster Sound, still has some ice in it.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 14, 2015, along with daily ice extent data for last year and the three lowest ice extent years (2012, 2007, and 2011).

Figure 2a. The graph above shows Arctic sea ice extent as of September 14, 2015, along with daily ice extent data for last year and the three lowest ice extent years (2012, 2007, and 2011). 2015 is shown in blue, 2014 in green, 2012 in orange, 2011 in brown, and 2007 in purple. The 1981 to 2010 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. About the data

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

This year’s minimum was 1.02 million square kilometers (394,000 square miles) above the record minimum extent in the satellite era, which occurred on September 17, 2012, and 1.81 million square kilometers (699,000 square miles) below the 1981 to 2010 average minimum.

Figure 2b. This figure shows patterns of sea level pressure and air temperature at the 925 hPa level for the summers (June through August) of 2015 and for 2007, expressed as differences with respect to average conditions over the period 1981 to 2010.

Figure 2b. This figure shows patterns of sea level pressure and air temperature at the 925 hPa level for the summers (June through August) of 2015 and for 2007, expressed as differences from the 1981 to 2010 average. The patterns for 2015 contributed to low September extent, but were not as favorable for producing low extent as the patterns seen in 2007.

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

Research has shown that especially low September sea extent tends to occur in years when the summer atmospheric circulation over the central Arctic Ocean is dominated by high atmospheric pressure, or anticyclonic conditions. This is because anticyclonic conditions tend to bring relatively sunny and warm conditions, and a clockwise wind pattern promotes ice convergence, making for a more compact, and thus smaller ice cover. The best example of this pattern occurred during the summer of 2007, which had the second lowest September extent in the satellite record. Conversely, Septembers with high extent tend to occur when the atmospheric circulation over the central Arctic Ocean is more cyclonic (counterclockwise), meaning unusually low pressure at the surface. This pattern brings more clouds, lower temperatures, and winds that spread the ice over a larger area.

Viewed in this framework, the pattern of atmospheric circulation for summer 2015 as a whole (June through August) favored a low September extent. Sea level pressures were higher than average over the central Arctic Ocean, as well as over Greenland and the surrounding region. Pressures were below average over north-central Eurasia. This was associated with air temperatures at the 925 hPa level (about 3,000 feet above the surface) that were above average over much of the Arctic Ocean, especially along the coast of eastern Siberia, in the Laptev Sea, and the Canadian Arctic Archipelago extending to the pole. However, it was not nearly as favorable as the 2007 pattern, when the area of unusually high pressure was located further south and east (over the northern Beaufort Sea), and unusually low pressure extended along much of the coast of northern Eurasia. This led to a pattern of warm winds from the south over the East Siberian and Chukchi Seas, promoting strong melt and transport of ice away from the coast. For both 2015 and 2007, the summer pressure patterns led to winds directed down the Fram Strait, helping to transport ice out of the Arctic Ocean into the East Greenland Sea.

Varying distribution of ice in 2015 versus 2012

Figure 3. This image compares differences in ice-covered areas between September 11, 2015 and September 17, 2012, the record low minimum extent.

Figure 3. This image compares differences in ice-covered areas between September 11, 2015 and September 17, 2012, the record low minimum extent. Light blue shading indicates the region where ice occurred in both 2015 and 2012, while white and medium blue areas show ice cover unique to 2012 and to 2015, respectively. Sea Ice Index data. About the data

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

While minimum extent was higher this year compared to 2012, there are many similarities in the spatial pattern of the ice cover. Both years had considerable ice loss in the Beaufort, Chukchi, and East Siberian seas, though this year the ice extent did not retreat as far north as in 2012. Both also show a tongue of ice extending further southward on the Siberian side of the Arctic. In 2012, the tongue extended toward the Laptev Sea. This year, the tongue is farther east, in the western part of the East Siberian Sea, and is related to thicker, older ice that did not melt completely. North of Svalbard and in the Kara Sea, sea ice extent was slightly higher this year than in 2012.

Previous minimum Arctic sea ice extents

Table 1.   Previous minimum Arctic sea ice extents
 YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
2006 5.77 2.28 September 17
2007 4.15 1.60 September 18
2008 4.59 1.77 September 20
2009 5.12 1.98 September 13
2010 4.61 1.78 September 21
2011 4.34 1.67 September 11
2012 3.39 1.31 September 17
2013 5.05 1.95 September 13
2014 5.03 1.94 September 17
2015 4.41 1.70 September 11
1979 to 2000 average 6.70 2.59 September 13
1981 to 2010 average 6.22 2.40 September 15

Ten lowest minimum Arctic sea ice extents (1981 to 2010 average)

Table 2.  Ten lowest minimum Arctic sea ice extents (1981 to 2010 average)
 RANK  YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
1 2012 3.39 1.31 September 17
2 2007 4.15 1.60 September 18
3 2011 4.34 1.67 September 11
4 2015 4.41 1.70 September 11
5 2008 4.59 1.77 September 20
6 2010 4.61 1.78 September 21
7 2014 5.03 1.94 September 17
8 2013 5.05 1.95 September 13
9 2009 5.12 1.98 September 13
10 2005 5.32 2.05 September 22

Note that the dates and extents of the minima have been re-calculated from what we posted in previous years. In March 2015, NSIDC made two revisions to Arctic Sea Ice Index extent values used in our analyses, to improve scientific accuracy. These changes do not significantly affect sea ice trends and year-to-year comparisons, but in some instances users may notice very small changes in values from the previous version of the data. First, calculations of ice extent near the North Pole were improved whenever a newer satellite orbited closer to the pole than older satellites in the series, by using a sensor-specific pole hole for the extent calculations. Second, the accuracy of ice detection near the ice edge was slightly improved by adopting an improved residual weather effect filter. Details on the changes are discussed in the Sea Ice Index documentation.

U.S. icebreaker reaches the North Pole

Figure 4. Scientists and the crew of U.S. Coast Guard Icebreaker Healy have their portrait taken at the North Pole on September 7, 2015.

Figure 4. Scientists and the crew of U.S. Coast Guard Icebreaker Healy have their portrait taken at the North Pole on September 7, 2015. The Healy reached the pole on September 5.

Credit: U.S. Coast Guard photo by Petty Officer 2nd Class Cory J. Mendenhall
High-resolution image

After four weeks at sea, the Coast Guard Icebreaker Healy reached the North Pole on September 5. The ship left Dutch Harbor on August 9 with about 145 people on board, including about fifty scientists. The Healy is a medium-duty icebreaker and in the years past would not have been suitable to navigate through thick ice floes to reach the pole. This is the first time that a U.S. ship has made a solo traverse of the North Pole. As clear evidence that the melt season was coming to a close, air temperatures were 21 degrees Fahrenheit (-6 degrees Celsius). The U.S. icebreaker’s capability is far behind that of Russia and other Arctic nations, and plans are ongoing for the U.S. to build a new polar-class icebreaking vessel.

Impact of sea ice convergence in 2013

Figure 5. These graphs show onshore ice drift during the summer of 2013.

Figure 5. These graphs show onshore ice drift during the summer of 2013. Due to ice convergence, an ice area in May (in red) is compressed by ~23% by the end of the summer (dashed line).

Credit: Ron Kwok, NASA Jet Propulsion Laboratory
High-resolution image

Thick, deformed ice, made up of pressure ridges with deep keels, is formed when the sea ice cover is pushed against or converges on the coast. Sea ice convergence along the coasts of Greenland and the Canadian Arctic Archipelago is a source of the thickest ice (tens of meters) in the Arctic Ocean. The thicker ice is more likely to survive the summer to form the Arctic Ocean’s perennial ice cover. A new paper by Ron Kwok at the NASA Jet Propulsion Laboratory shows that in summer of 2013, strong wind-driven onshore ice drift was forced by the relative location of high- and low- pressure centers over the Arctic Ocean (see Figure 5). A sampled ice parcel (in red) shows an area compression of 23% between May and October; the dashes indicate its area by end of summer. This is equivalent to an increase in thickness of ~30% within that area. If this thicker ice were transported to areas of high melt rates (like that in the southern Beaufort), it would have an impact on summer ice coverage. The presence of a band of sea ice that survived a large part of the summer in 2015, is likely due to the thicker ice that formed in this region.

Reference

Kwok, R. 2015. Sea ice convergence along the Arctic coasts of Greenland and the Canadian Arctic Archipelago: Variability and extremes (1992–2014). Geophysical Research Letters, (Accepted) doi:10.1002/2015GL065462.