Which August will we get?

Average sea ice extent for July 2017 ended up fifth lowest in the satellite record. This reflects weather conditions that were not favorable for ice loss. It will be important to monitor August 2017, as weather conditions and storm events during this month have been closely related to the seasonal minimum sea ice extent in the recent years.

Overview of conditions

Figure 1. Arctic sea ice extent for July 2017 was 8.2 million square kilometers (3.2 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for July 2017 was 8.21 million square kilometers (3.17 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Arctic sea ice extent for July 2017 averaged 8.21 million square kilometers (3.17 million square miles), the fifth lowest July in the 1979 to 2017 satellite record. The average July extent was 1.58 million square kilometers (610,000 square miles) below the 1981 to 2010 long-term average, and 270,000 square kilometers (104,000 square miles) above the previous record low July set in 2011. July 2017 tracked 250,000 square kilometers (97,000 square miles) above the July 2012 extent and 20,000 square kilometers (7,700 square miles) above the July 2007 extent.

Ice extent was lower than average over most of the Arctic, particularly on the Pacific side where the ice retreated throughout July in the Beaufort, Chukchi, and East Siberian Seas. In the eastern Beaufort Sea on the other hand, extent slightly expanded during July. This may relate to the cyclonic (counterclockwise) pattern of winds favoring the drift of sea ice into the region.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of August 1, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted red. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data

Figure 2a. The graph above shows Arctic sea ice extent as of August 1, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted red. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 2b. The plot shows differences from average for Arctic air temperatures at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Figure 2b. The plot shows Arctic air temperature differences relative to the 1981 to 2010 long-term average at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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The air temperature pattern over the Arctic was rather complex in July. Temperatures were above average over Alaska, extending into the Beaufort Sea (1 to 2 degrees Celsius or 2 to 4 degrees Fahrenheit) and the Kara and Barents Seas (2 to 4 degrees Celsius or 4 to 7 degrees Fahrenheit). By contrast, temperatures were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) lower than average over Greenland, East Central Siberia, and the Laptev Sea. The air pressure pattern at sea level was dominated by a broad area of low pressure covering most of the Arctic Ocean, with the lowest pressures centered just south of the Pole and west of the date line. Another locus of low pressure was centered over the southern Canadian Arctic Archipelago.

A cyclonic circulation over the central Arctic Ocean is generally viewed as unfavorable for rapid summer ice loss. Ice loss rates tend to be higher when the central Arctic Ocean is dominated by high pressure during summer.

July 2017 compared to previous years

Figure 3. Monthly July ice extent for 1979 to 2017 shows a decline of 7.4 percent per decade.

Figure 3. Monthly July ice extent for 1979 to 2017 shows a decline of 7.4 percent per decade.

Credit: National Snow and Ice Data Center
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The linear rate of decline for July 2017 was 72,500 square kilometers (28,000 square miles) per year, or 7.4 percent per decade.

Onset of surface melt

Figure 4. The plot on the left shows melt onset dates in day of the year (left). Warm colors indicate early melt onset and cooler colors indicate a later melt onset. The plot on the right shows departures from the average melt onset dates in number of days. Warmer colors indicate later than average melt onset and cooler colors indicate later than average melt onset.

Figure 4. The plot on the left shows the average melt onset dates in day of the year. Warm colors indicate early melt onset and cooler colors indicate a later melt onset. The plot on the right shows departures from the average melt onset dates in number of days. Warmer colors indicate later than average melt onset and cooler colors indicate earlier than average melt onset.

Credit: National Snow and Ice Data Center
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One important influence on the pace of summer sea ice retreat is the timing of the onset of surface melt. Surface melt drops the albedo, allowing more solar radiation to be absorbed at the surface. The onset of surface melt in 2017 was quite early in the Chukchi and Eastern Beaufort Seas—as much as 35 days earlier than the 1981 to 2010 average. Early melt was also seen in the Kara Sea, Baffin Bay, and Canadian Arctic Archipelago (10 to 20 days earlier than average). However, over a large portion of the Arctic Ocean’s central ice pack, melt onset was a few days later than average. Melt onset was up to ten days later than average in the polar areas at the northern extents of the Beaufort and East Siberian Seas. The spatial pattern in the timing of melt onset reflects the combination of the warm winter and early spring conditions along the edge of the pack on the Pacific side, very warm winter conditions in the Barents and Kara Sea areas, and relatively cool late spring to early summer conditions over the central Arctic Ocean.

Sea ice predictions for the 2017 minimum

Figure 5. This chart summarizes the 2017 summer September minimum forecasts from 36 different models and approaches to predicting the evolution of the Arctic pack.

Figure 5. This chart summarizes the 2017 summer September minimum forecasts from 36 different models and approaches to predicting the evolution of the Arctic pack.

Credit: SIPN/ARCUS
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A report released by the Sea Ice Prediction Network (SIPN), an activity of the Arctic Research Council of the United States (ARCUS), compiled 36 forecasts of September average sea ice extent that were submitted during July. Additionally, SIPN produces estimates for sea ice extent in the Alaska region and, new this year, for the Antarctic sea ice maximum (not shown). The September Arctic extent forecasts range from a new record low of 3.1 million square kilometers (1.2 million square miles) to an eleventh lowest extent of 5.5 million square kilometers (2.1 million square miles). The median of the estimates is slightly below the September 2016 value, currently the fifth lowest. A variety of methods are used to make these forecasts, ranging from coupled ice-ocean-atmospheric models to statistical approaches and heuristic guesses. NSIDC scientists Julienne Stroeve, Walt Meier, Andrew Barrett, Mark Serreze, and the late Drew Slater have regularly contributed to several separate estimations for the SIPN.

Sea ice retreat may be changing the AMOC

In the far northern Atlantic, warm water flowing northward from the tropics is cooled by the atmosphere, becomes denser, and eventually sinks to great depths. The descending water is key in driving a sub-surface and surface ocean circulation system called the Atlantic Meridional Overturning Circulation (AMOC), which is part of the global ocean conveyor belt of heat and salinity. Where the Atlantic water sinks has a very important effect on the climate of Northern Europe; the heat that the ocean loses to the atmosphere is what keeps Northern Europe quite warm relative to its latitude. For example, Amsterdam is at the same latitude as Winnipeg, Canada, but experiences much warmer winters.

Based on a recent modeling study, Florian Sévellec and colleagues propose that the ongoing loss of Arctic sea ice may disrupt the AMOC. The sea ice loss leads to a freshening of the northern North Atlantic and stronger heat absorption at the surface. This means that waters in the northern North Atlantic are less dense than they used to be, which has the effect of providing a cap, or lid, that may inhibit the northward flow of warm waters at the surface and the eventual sinking of these waters. The authors suggest that the Arctic sea ice decline may help to explain observations suggesting that the AMOC may be slowing down, and why there is a regional minimum in warming (sometimes called the Warming Hole) over the subpolar North Atlantic.

Further reading

Sea Ice Prediction Network. “2017: July Report.” Arctic Research Council of the United States. https://www.arcus.org/sipn/sea-ice-outlook/2017/july.

Sévellec, F., A. V. Fedorov, and W. Liu. 2017. Arctic sea-ice decline weakens the Atlantic Meridional Overturning Circulation. Nature Climate Change, doi:10.1038/nclimate3353.

Arctic ice extent near levels recorded in 2012

Contrasting with the fairly slow start to the melt season in May, June saw the ice retreat at a faster than average rate. On July 2, Arctic sea ice extent was at the same level recorded in 2012 and 2016. In 2012, September sea ice extent reached the lowest in the satellite record. As a new feature to Arctic Sea Ice News and Analysis, NSIDC now provides a daily updated map of ice concentration in addition to the daily map of ice extent.

Overview of conditions

Figure 1. Arctic sea ice extent for June 2017 averaged 11.06 million square kilometers (4.27 million square miles).

Figure 1. Arctic sea ice extent for June 2017 averaged 11.06 million square kilometers (4.27 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Arctic sea ice extent for June 2017 averaged 11.06 million square kilometers (4.27 million square miles), the sixth lowest in the 1979 to 2017 satellite record. The average June 2017 extent was 900,000 square kilometers (348,000 square miles) below the 1981 to 2010 long-term average, and 460,000 square kilometers (178,000 square miles) above the previous record low set in 2016.

Continuing the pattern seen in May, sea ice extent at the end of the month remained below average in the Chukchi Sea and in the Barents Sea. Ice extent was at average levels in the Greenland Sea. Areas of low concentration ice have developed along the ice edge and coastal seas.

Based on imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the NASA Terra and Aqua satellites, summer melt ponds atop the ice cover were somewhat slow to develop. However, there is now widespread melt pond coverage in the Canadian Archipelago and the Laptev and East Siberian Seas. Data from the Advanced Microwave Scanning Radiometer 2 (AMSR-2) instrument analyzed by the University of Bremen, as well as MODIS imagery, indicate that melt ponds have also developed over the Central Arctic Ocean. Researchers in Dease Strait in Northern Canada have observed melt ponds forming about two weeks earlier than average. Melt ponds are important as they decrease the albedo or reflectivity of the ice surface, which hastens further melt.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July 4, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dashed red. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data.

Figure 2. The graph above shows Arctic sea ice extent as of July 4, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dashed red. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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The rate of decline in ice extent was fairly steady through the month, and the average rate of decline of 81,800 square kilometers (31,600 square miles) per day was slightly faster than the 1981 to 2010 long-term average of 56,300 square kilometers (21,700 square miles) per day. On July 2, extent was the same as that recorded in 2012 and 2016. The year 2012 ended up with the lowest September extent in the satellite record.

June air temperatures were modestly above average (1 to 3 degrees Celsius or 2 to 5 degrees Fahrenheit) in a band spanning the Arctic Ocean roughly centered along the date line and the prime meridian. This contrasts with below-average temperatures over the eastern Beaufort Sea and Canadian Arctic Archipelago and the Barents and Laptev Seas (1 to 3 degrees Celsius, 2 to 5 degrees Fahrenheit). Atmospheric pressures at sea level were below-average over the Kara Sea and extending north of the Laptev Sea.

June 2017 compared to previous years

Figure 3. Monthly June ice extent for 1979 to 2017 shows a decline of 3.7 percent per decade.

Figure 3. Monthly June ice extent for 1979 to 2017 shows a decline of 3.7 percent per decade.

Credit: National Snow and Ice Data Center
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The linear rate of decline for June is 44,300 square kilometers (17,100 square miles) per year, or 3.7 percent per decade.

Ice thickness

Figure 4. Figure 4. This figure shows that sea ice thicknesses for May 2017 were below the 2000 to 2015 average over most of the Arctic Ocean (areas in blue) except for the region north and west of the Svalbard archipelago (areas in red). ||Credit: University of Washington Pan-Arctic Ice Ocean Modeling and Assimilation System

Figure 4. This figure shows that sea ice thicknesses for May 2017 were below the 2000 to 2015 average over most of the Arctic Ocean (areas in blue) except for the region north and west of the Svalbard archipelago (areas in red).

Credit: University of Washington Pan-Arctic Ice Ocean Modeling and Assimilation System
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The University of Washington Seattle Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) regularly produces maps of ice thickness anomalies (departures from the long-term average). PIOMAS is based on a coupled ice-ocean model that is driven by data from an atmospheric reanalysis, and also assimilates data on observed ocean conditions and ice thickness (e.g., from NASA IceBridge). The PIOMAS analysis suggests that, relative to the average over the period 2000 to 2015, ice thickness for May 2017 (when the melt season was just beginning) was below average over most of the Arctic Ocean, especially in the Chukchi Sea and north of the Canadian Arctic Archipelago. A small region with above-average ice thickness is depicted over the Atlantic side of the Arctic north and west of the Svalbard Archipelago, and in the Greenland Sea. Starting the melt season with below-average ice thickness raises the likelihood of having especially low September ice extent.

Freezing degree days and ice thickness

Figure 5. The figure shows departures from average in cumulate freezing degree days, extending from July 1 for a given year through July 1 of the next year, along with the range, 15th through 85th percentile and 30th to 70th percentile values over the base period 1981 through 2010.

Figure 5. The figure shows departures from average in cumulate freezing degree days, extending from July 1 for a given year through July 1 of the next year, along with the range, 15th through 85th percentile and 30th to 70th percentile values over the base period 1981 through 2010.

Credit: National Snow and Ice Data Center
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Cumulative Freezing Degree Days (FDD) is a simple measure of how cold it has been and for how long. Cumulative FDD is the sum of daily mean temperatures below zero from some start date. Here we start on July 1. Cumulative FDD is related to ice thickness because, on average, years with longer periods of temperatures below freezing will have more ice growth. A simple empirical model that has been used by scientists relates ice thickness to the square root of cumulative FDD.

Anomalies (departures from the average) in cumulative FDD illustrate the coldness of a given period relative to the long-term average (1981 to 2010). Figure 5 shows that most of the period from July 2016 to July 2017 was extremely mild and was milder (less cold) than both 2006 to 2007 and 2011 to 2012. September of both 2007 and 2012 ended up with very low September sea ice extent. This is consistent with below-average ice thickness seen in the PIOMAS data. Although conditions cooled in May and June, this likely had little impact on ice thickness. This is because ice in the Arctic reaches its maximum thickness earlier in the season during March or April. As noted earlier, ice retreated at a fast rate throughout June. This is likely linked to a thinner than average ice cover as seen in the PIOMAS analysis.

Sudden Antarctic sea ice decline in late 2016

A slight decrease in the rate of sea ice growth at the end of June brought Antarctic sea ice extent back to daily record lows. Sea ice extent in the Bellingshausen, eastern Amundsen, and western Ross Seas was below average.

Our post on December 2016 ice conditions highlighted a precipitous drop in Antarctic sea ice extent in the Weddell and Ross Sea sectors during September, October, and November of 2016. A recent study by John Turner and colleagues links this pattern of sea ice decline to a series of strong storms, marked by long periods of warm winds from the north. These changing weather conditions are associated with large shifts in the Southern Annual Mode index (SAM index).

Further reading

Turner, J., T. Phillips, G. J. Marshall, J. S. Hosking, J. O. Pope, T. J. Bracegirdle, and P. Deb. 2017. Unprecedented springtime retreat of Antarctic sea ice in 2016, Geophysical Research Letters, 44, doi:10.1002/2017GL073656.

Warm Arctic, cool continents

Arctic sea ice extent for April 2017 tied with April 2016 for the lowest in the satellite record for the month. Warm weather conditions and lower-than-average sea ice extent prevailed over the Pacific side of the Arctic, while relatively cool conditions were the rule in northern Europe and eastern North America. In the Southern Hemisphere, Antarctic sea ice extent remained lower than average.

Overview of conditions

Figure 1. Arctic sea ice extent for April 2017 was 13.83 million square kilometers (5.34 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for April 2017 was 13.83 million square kilometers (5.34 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Arctic sea ice extent for April 2017 averaged 13.83 million square kilometers (5.34 million square miles), and tied with April 2016 for the lowest April extent in the 38-year satellite record. The April 2017 extent is 1.02 million square kilometers (394,000 square miles) below the April 1981 to 2010 long-term average. The largest reductions in ice extent through the month occurred on the Pacific side of the Arctic, within the Bering Sea and the Sea of Okhotsk. Little change in extent occurred in the Atlantic sector of the Arctic.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of May 2, 2017, along with daily ice extent data for four previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, and 2013 in purple, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data.

Figure 2a. The graph above shows Arctic sea ice extent as of May 2, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, and 2013 in purple, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 2b. These figures show April 2017 Arctic air temperature difference at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius (left) and sea level pressure (right). Yellows and reds indicate higher than average temperatures and pressure; blues and purples indicate lower than average temperatures and pressure.

Figure 2b. These figures show April 2017 differences from average for Arctic air temperatures at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius (left) and for sea level pressure (right). 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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Figure 2c. These maps show Arctic sea ice motion for April 13 to 15, 2017, which is representative of the general pattern seen throughout the month. Black arrows represent sea ice drift. The purple arrows represent "filled" values, data gaps that have been interpolated from surrounding data.

Figure 2c. These maps show Arctic sea ice motion for April 13 to 15, 2017, which is representative of the general pattern seen throughout the month. Black arrows represent sea ice drift. The purple arrows represent “filled” values, data gaps that have been interpolated from surrounding data.

Credit: EUMETSAT
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The decline in ice extent through the month was fairly steady, at a rate similar to what was observed over the previous two Aprils (2016 and 2015). Throughout the month, sea ice extent was either at daily record lows for the period of satellite observations, or within 100,000 square kilometers (~38,600 square miles) of record low values. At the end of the month, extent was below average in the Barents Sea, the Sea of Okhotsk, and the western Bering Sea, similar to the pattern seen in March. Despite fairly warm conditions, sea ice extent was slightly above average in Baffin Bay.

Unusually warm conditions were observed across the Pacific side of the Arctic Ocean, with temperatures at the 925 hPa level (about 2,500 feet above sea level) north of the Bering Strait ranging from 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) above the 1981 to 2010 average. Western Alaska and easternmost Siberia also saw warm conditions. However, below average temperatures ruled across a broad swath of northern Canada. Of particular note, cooler-than-average conditions also prevailed over Greenland, leading to relatively little surface melting on the ice sheet in April (unlike the preceding two years).

The overall temperature pattern is consistent with the average sea level pressure pattern for the month, which had large areas of low and higher-than-average pressure in the Eastern and Western Hemispheres, respectively. This pattern produces a cross-Arctic airflow, with southerly winds from the Bering Sea blowing into the Chukchi Sea and central Arctic, and cool winds blowing from the north over Scandinavia and other areas of northern Europe. This cross-Arctic wind pattern is also evident in the sea ice motion field for April 2017. Sea ice motion is determined by tracking patterns in the sea ice in both visible imagery and in passive microwave data from satellites.

April 2017 compared to previous years

Figure 3a. Monthly April ice extent for 1979 to 2017 shows a decline of 2.6 percent per decade.

Figure 3a. Monthly April ice extent for 1979 to 2017 shows a decline of 2.6 percent per decade.

Credit: National Snow and Ice Data Center
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Figure 3b. This shows April 2017 Arctic sea ice concentration anomalies (left) and Arctic sea ice concentration trends (right).

Figure 3b. These images show April 2017 Arctic sea ice concentration anomalies (left) and Arctic sea ice concentration trends (right). Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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The linear rate of decline for April is 38,000 square kilometers (15,000 square miles) per year, or 2.6 percent per decade.

Declining ice extent in the Barents Sea, Sea of Okhotsk, and off the coast of southeastern Greenland is a part of the long-term pattern of sea ice decline. Below-average ice extent in the western Bering Sea has to date not been a part of the long-term trend for April.

A report from the field

Figure 4. This photo shows broken up sea ice and some multi-year floes at Alert, on the northern tip of Ellesmere Island, Canada. A researcher and a Twin Otter aircraft are obscured in the background.

Figure 4. This photo shows broken up sea ice and some multi-year floes at Alert, on the northern tip of Ellesmere Island, Canada on April 2017. A researcher and a Twin Otter aircraft are obscured in the background.

Credit: J. Stroeve/NSIDC
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NSIDC scientist Julienne Stroeve continued her Arctic field work into early April, moving from Cambridge Bay, Canada to Alert in Ellesmere Island. In Alert, Stroeve focused on sampling ice thickness and snow pack characteristics along a CryoSat-2 flight track within the Lincoln Sea. This is an area between northernmost Greenland and Ellesmere Island where thick, old ice remains. The scientists flew by Twin Otter each day, out onto the sea ice between latitudes 83°N and 87.1°N. The field campaign was also supported by an aircraft from the British Antarctic Survey carrying a Ka band radar, LiDAR, and a broadband radiometer. A NASA Operation IceBridge flight also flew over the same track.

The group noted that the ice was unusually broken up and reduced to rubble, with few large multi-year floes, forcing the pilots to land on refrozen leads that at times were only 70 centimeters (28 inches) thick. Pilots remarked that they had never seen the ice look like this. Preliminary estimates suggest mean thicknesses ranging from 2 to 3.4 meters (6.6 to 11 feet), with the thickest ice found between an ice bridge in the Lincoln Sea and mobile pack ice to the north. Modal thickness, a representation of thermodynamically-grown level ice, ranged between 1.8 and 2.9 meters (6 and 10 feet), including 0.25 to 0.4 meters (10 to 16 inches) of snow. Second- and first-year modal ice thicknesses ranged between 1.8 and 1.9 meters (6 and 6.2 feet), about 0.2 meters (8 inches) thinner than previous airborne measurements indicated. More details can be found at the European Space Agency’s Campaigns at Work blog.

Arctic sea ice age

Figure 5. These maps shows 2016 (top left) and 2017 (top right) Arctic sea ice age for the end of March and the time series of percent coverage for the Arctic Ocean (bottom).

Figure 5. These maps shows 2016 (top left) and 2017 (top right) Arctic sea ice age for the end of March and the time series of percent coverage for the Arctic Ocean (bottom).

Credit: National Snow and Ice Data Center, courtesy M. Tschudi, C. Fowler, J. Maslanik, R. Stewart/University of Colorado Boulder; W. Meier/NASA Cryospheric Sciences
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Sea ice age is a proxy for ice thickness, with older ice generally meaning thicker ice. Though ice can pile up into rubble fields when the motion of the ice pushes up against the coast or thicker ice, level ice generally increases in thickness as it ages through more winter freeze cycles. Thus, ice age is a reasonable indicator of the sea ice thickness.

At the end of March, ice age data show only a small remaining coverage of old (5+ years) ice. Since 2011, the oldest ice has comprised less than 5 percent of the total ice cover. During the mid-1980s, such ice made up nearly a third of the ice.

The next oldest ice category, four-year-old ice has also dropped from about 8 to 10 percent to less than 5 percent. The coverage of intermediate age ice categories (2- and 3-year-old ice) has stayed fairly consistent through time. The oldest ice has essentially been replaced by first-year ice (ice that has formed since the previous September). First-year-ice has risen from 35 to 40 percent of the Arctic Ocean’s ice cover during the mid-1980s to about 70 percent now.

Comparison of March 2016 conditions to this year shows a similar percentage coverage for the different ice ages. However, the spatial distribution is different. In March 2016, bands of the oldest ice extended through the Beaufort Sea and into the Chukchi, with scattered patches north of the Canadian Archipelago and Greenland. This year, the oldest ice is consolidated against the coast of Greenland and the archipelago except for a short arm extending north to the region around the pole. Most of the third year ice is between Fram Strait and the pole, which means it is likely to exit the Arctic Ocean during the coming months.

Antarctic ice extent low, but not lowest

Figure 6. The graph above shows Antarctic sea ice extent as of May 2, 2017, along with daily ice extent data for four previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, and 2013 in purple, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data.

Figure 6. The graph above shows Antarctic sea ice extent as of May 2, 2017, along with daily ice extent data for four previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in dashed brown, and 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Antarctic sea ice grew at a slightly faster-than average pace in April, but was still setting daily record lows until about April 10, after which extent rose above the 1980 ice extent. The April 2017 sea ice extent is lower than average in the Amundsen Sea and slightly lower than average in the Ross Sea and easternmost Weddell Sea. However, an area of above average extent is present in the north-central Weddell. Temperatures on the continent were above average over West Antarctica and western Wilkes Land, and considerably below average over the central Weddell sea.

Arctic sea ice maximum at record low for third straight year

Arctic sea ice appears to have reached its annual maximum extent on March 7. This is the lowest maximum in the 38-year satellite record. NSIDC will post a detailed analysis of the 2016 to 2017 winter sea ice conditions in our regular monthly post in early April.

Overview of conditions

Figure 1. Arctic sea ice extent for March 7, 2017 was 14.42 million square kilometers (5.57 million square miles). The orange line shows the 1981 to 2010 median extent for that day.

Figure 1. Arctic sea ice extent for March 7, 2017 was 14.42 million square kilometers (5.57 million square miles). The orange line shows the 1981 to 2010 median extent for that day. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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On March 7, 2017, Arctic sea ice likely reached its maximum extent for the year, at 14.42 million square kilometers (5.57 million square miles), the lowest in the 38-year satellite record. This year’s maximum extent is 1.22 million square kilometers (471,000 square miles) below the 1981 to 2010 average maximum of 15.64 million square kilometers (6.04 million square miles) and 97,000 square kilometers (37,000 square miles) below the previous lowest maximum that occurred on February 25, 2015. This year’s maximum is 100,000 square kilometers (39,000 square miles) below the 2016 maximum, which is now third lowest. (In 2016, we reported that year’s maximum as the lowest and 2015 the second lowest. An update to the Sea Ice Index last summer has changed our numbers slightly.)

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of March 20, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data.

Figure 2a. The graph above shows Arctic sea ice extent as of March 20, 2017, along with daily ice extent data for five previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, 2012 to 2013 in purple, and 2011 to 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level in degrees Celsius from October 1, 2016 to February 28, 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average.

Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius from October 1, 2016 to February 28, 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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It was a very warm autumn and winter. Air temperatures at the 925 hPa level (about 2,500 feet above sea level) over the five months spanning October 2016 through February 2017 were more than 2.5 degrees Celsius (4.5 degrees Fahrenheit) above average over the entire Arctic Ocean, and greater than 5 degrees Celsius (9 degrees Fahrenheit) above average over large parts of the northern Chukchi and Barents Seas. These overall warm conditions were punctuated by a series of extreme heat waves over the Arctic Ocean.

Data from the European Space Agency’s CryoSat-2 satellite indicate that this winter’s ice cover may be only slightly thinner than that observed at this time of year for the past four years. However, an ice-ocean model at the University of Washington (PIOMAS) that incorporates observed weather conditions suggests the volume of ice in the Arctic is unusually low.

The Antarctic minimum

Figure 3. Antarctic sea ice extent for March 3, 2017 was 2.11 million square kilometers (813,000 million square miles). The orange line shows the 1981 to 2010 average extent for that day.

Figure 3. Antarctic sea ice extent for March 3, 2017 was 2.11 million square kilometers (815,000 square miles). The orange line shows the 1981 to 2010 median extent for that day. Sea Ice Index data. About the data

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

In the Southern Hemisphere, sea ice likely reached its minimum extent for the year on March 3, at 2.11 million square kilometers (815,000 square miles). This year’s minimum extent was the lowest in the satellite record, continuing a period of satellite-era record low daily extents that began in early November. However, the Antarctic system has been highly variable. As recently as 2015, Antarctic sea ice set record high daily extents, and in September 2014 reached a record high winter maximum.

The Antarctic minimum extent is 740,000 square kilometers (286,000 square miles) below the 1981 to 2010 average minimum of 2.85 million square kilometers (1.10 million square miles) and 184,000 square kilometers (71,000 square miles) below the previous lowest minimum that occurred on February 27, 1997.

Antarctic air temperatures during the autumn and winter were above average, but less so than in the Arctic. Air temperatures at the 925 hPa level (about 2,500 feet above sea level) near the sea ice edge have been about 1 to 2.5 degrees Celsius (2 to 4.5 degrees Fahrenheit) above the 1981 to 2010 average.

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.

Correction

On March 27, 2017, we made corrections to clarify the second paragraph under Conditions in context. The paragraph originally read:

Data from the European Space Agency’s CryoSat-2 satellite indicate that this winter’s ice cover is slightly thinner compared to the past four years. An ice-ocean model at the University of Washington that incorporates observed weather conditions suggests the volume of ice in the Arctic is unusually low for this time of year.

Another warm month in the Arctic

High air temperatures observed over the Barents and Kara Seas for much of this past winter moderated in February. Overall, the Arctic remained warmer than average and sea ice extent remained at record low levels.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2017 was 14.28 million square kilometers (5.51 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. 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 2017 was 14.28 million square kilometers (5.51 million square miles). The magenta line shows the 1981 to 2010 median extent for the month. Sea Ice Index data. About the data

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

Arctic sea ice extent for February 2017 averaged 14.28 million square kilometers (5.51 million square miles), the lowest February extent in the 38-year satellite record. This is 40,000 square kilometers (15,400 square miles) below February 2016, the previous lowest extent for the month, and 1.18 million square kilometers (455,600 square miles) below the February 1981 to 2010 long term average.

Ice extent increased at varying rates, with faster growth during the first and third weeks, and slower growth during the second and fourth weeks. Most of the ice growth in February occurred in the Bering Sea, though extent in the Bering remained below average by the end of the month. Sea ice extent in the Sea of Okhotsk substantially decreased mid-month before rebounding to almost typical levels at the end of the month. Overall, however, the ice retreated in this region. Extent in the Barents and Kara Seas remained low through the month as is has all season, with little change in the ice edge location.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of March 5, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of March 5, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data. About the data

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

Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level in degrees Celsius for February 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division| High-resolution image

Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level in degrees Celsius for February 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average.

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

Air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) remained 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) above average over the Arctic Ocean. The high air temperatures observed over the Barents and Kara Seas for much of this past winter moderated in February. February air temperatures over the Barents Sea ranged between 4 to 5 degrees Celsius (8 to 9 degrees Fahrenheit) above average, compared to 7 degrees Celsius (13 degrees Fahrenheit) above average in January. Recall that these January temperature extremes were associated with a series of strong cyclones entering the Arctic Ocean from the North Atlantic, drawing in warm air. Sea level pressure in February was nevertheless lower than average over much of the Arctic Ocean. Sea level pressure was higher than average over the Bering Sea and just north of Scandinavia.

February 2017 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2017 shows a decline of 3 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly February ice extent for 1979 to 2017 shows a decline of 3 percent per decade.

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

The linear rate of decline for February is 46,900 square kilometers (18,100 square miles) per year, or 3 percent per decade.

Antarctic minimum extent

Figure 4a. The graph above shows Antarctic sea ice extent as of March 5, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 4a. The graph above shows Antarctic sea ice extent as of March 5, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 4b. This graph shows monthly ice extent for February plotted as a time series of percent differences with respect to the average over the period 1981 through 2010. The dotted gray line shows the linear trend. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 4b. This graph shows monthly ice extent for February, plotted as a time series of percent differences from the 1981 to 2010 average. The dotted gray line shows the linear trend. Sea Ice Index data. About the data

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

Antarctic sea ice is nearing its annual minimum extent and continues to track at record low levels for this time of year. On February 13, Antarctic sea ice extent dropped to 2.29 million square kilometers (884,000 square miles), setting a record lowest extent in the satellite era. The previous lowest extent occurred on February 27, 1997. By the end of February, extent had dropped even further to 2.13 million square kilometers (822,400 square miles). The record lows are not surprising, given Antarctic sea ice extent’s high variability. Just a few years back, extent in the region set record highs (Figure 4b).

Sea ice extent was particularly low in the Amundsen Sea, which remained nearly ice-free throughout February. Typically, sea ice in February extends at least a couple hundred kilometers along the entire coastline of the Amundsen. Near-average ice extent persisted in the Weddell Sea and in several sectors along the East Antarctic coast.

Continuity of the sea ice record

Figure 5. This chart shows the lifespans of current and future orbiting passive microwave sensors. ||Credit: Walt Meier, NASA| High-resolution image

Figure 5. This chart shows the lifespans of current and expected future orbiting passive microwave sensors.

Credit: W. Meier, NASA Goddard Space Flight Center Cryospheric Sciences Laboratory
High-resolution image

As noted last year, the sensor that NSIDC had been using for sea ice extent, the Special Sensor Microwave Imager and Sounder (SSMIS) on the Defense Meteorological Satellite Program (DMSP) F17 satellite, started to malfunction. In response, NSIDC switched to the SSMIS on the newer F18 satellite. Later, F17 recovered to normal function, though it recently started to malfunction again.

The DMSP series of sensors have been a stalwart of the sea ice extent time series, providing a continuous record since 1987. Connecting this to data from the earlier Scanning Multichannel Microwave Radiometer (SMMR) results in a continuous record starting in 1979 of high quality and consistency. However, with the issues of F17 and last year’s loss of the newest sensor, F19, grave concerns have arisen about the long-term continuity of the passive microwave sea ice record. Only two DMSP sensors are currently fully capable for sea ice observations: F18 and the older F16; these two sensors have been operating for over 7 and 13 years respectively, well beyond their nominal 5-year lifetimes.

The only other similar sensor currently operating is the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2), which is approaching its 5-year design lifetime in May 2017. NSIDC is now evaluating AMSR2 data for integration into the sea ice data record if needed. Future satellite missions with passive microwave sensors are either planned or proposed by the U.S., JAXA, and ESA, but it is unlikely that a successor to the DMSP series and AMSR2 will be operational before 2022. This presents a growing risk of a gap in the sea ice extent record. Should such a gap occur, NSIDC and NASA would seek to fill the gap as much as possible with other types of sensors (e.g., visible or infrared sensors).

Low sea ice extent continues in both poles

Sea ice in the Arctic and the Antarctic set record low extents every day in December, continuing the pattern that began in November. Warm atmospheric conditions persisted over the Arctic Ocean, notably in the far northern Atlantic and the northern Bering Sea. Air temperatures near the Antarctic sea ice edge were near average. For the year 2016, sea ice extent in both polar regions was at levels well below what is typical of the past several decades.

Overview of conditions

Figure 1. Arctic sea ice extent for December 2016 was 12.10 million square kilometers (4.67 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole.

Figure 1. Arctic sea ice extent for December 2016 was 12.10 million square kilometers (4.67 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

Arctic sea ice extent for December 2016 averaged 12.10 million square kilometers (4.67 million square miles), the second lowest December extent in the satellite record. This is 20,000 square kilometers (7,700 square miles) above December 2010, the lowest December extent, and 1.03 million square kilometers (397,700 square miles) below the December 1981 to 2010 long-term average.

The rate of ice growth for December was 90,000 square kilometers (34,700 square miles) per day. This is faster than the long-term average of 64,100 square kilometers (24,700 square miles) per day. As a result, extent for December was not as far below average as was the case in November. Ice growth for December occurred primarily within the Chukchi Sea, Kara Sea, and Hudson Bay—areas that experienced a late seasonal freeze-up. Compared to the record low for the month set in 2010, sea ice for December 2016 was less extensive in the Kara, Barents, and East Greenland Seas, and more extensive in Baffin and Hudson Bays.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of January 2, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 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 2a. The graph above shows Arctic sea ice extent as of January 2, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 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. This plot shows air temperature difference from average for December 2016. Air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) were more than 3 degrees Celsius (5 degrees Fahrenheit) above the 1981 to 2010 average over the central Arctic Ocean and northern Barents Sea, and as much as 5 degrees Celsius (9 degrees Fahrenheit) above average over the Chukchi Sea.

Figure 2b. This plot shows air temperature difference from average for December 2016. Air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) were more than 3 degrees Celsius (5 degrees Fahrenheit) above the 1981 to 2010 average over the central Arctic Ocean and northern Barents Sea, and as much as 5 degrees Celsius (9 degrees Fahrenheit) above average over the Chukchi Sea.

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

Air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) were more than 3 degrees Celsius (5 degrees Fahrenheit) above the 1981 to 2010 average over the central Arctic Ocean and northern Barents Sea, and as much as 5 degrees Celsius (9 degrees Fahrenheit) above average over the Chukchi Sea. Repeated warm air intrusions occurred over the Chukchi and Barents Seas, continuing the pattern seen in November.

In contrast, central Russia and northern British Columbia experienced temperatures 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) below average (Figure 2b). Atmospheric circulation over the Arctic in December was characterized by a broad area of lower-than-average pressure over Greenland and the North Pole, extending across the Arctic Ocean to eastern Siberia, and another region of low pressure over the Ural Mountains. Higher-than-average pressure dominated Europe and the Gulf of Alaska. This set up the very warm southerly winds from both the northern North Atlantic and the Bering Strait areas, pushing Arctic air temperatures to unusually high levels for brief periods in early December and near Christmas.

December 2016 compared to previous years

Figure 3. Monthly December ice extent for 1979 to 2016 shows a decline of 3.4 percent per decade.

Figure 3. Monthly December ice extent for 1979 to 2016 shows a decline of 3.4 percent per decade.

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

Through 2016, the linear rate of decline for December is 44,500 square kilometers (17,200 square miles) per year, or 3.4 percent per decade.

While daily extents for December 2016 were at record lows, based on the method employed by NSIDC, the monthly average extent for December 2016 was slightly higher than that recorded for December 2010, the record low December in the satellite record. The monthly average extent for the month of December is higher than the month’s average of daily extents because of the way in which the Sea Ice Index algorithm calculates the monthly extent. The algorithm calculates the monthly average total extent from the monthly average gridded concentration field. Thus, when sea ice is retreating or advancing at a high rate over the course of the month, as was the case for December 2016, the Sea Ice Index monthly average can yield a larger extent than from simply averaging daily extent values. See the Sea Ice Index documentation for further information.

2016 year in review

Figure 4. Arctic temperatures at the 925 hPa level (about 2,500 feet above sea level) over the period January to December of 2016 were above average over nearly the entire Arctic region and especially over the Arctic Ocean. By contrast, air temperatures over the Antarctic region for the same period were above average in some areas, such as the Antarctic Peninsula and near the pole, but below average in others.

Figure 4. Arctic temperatures at the 925 hPa level (about 2,500 feet above sea level) over the period January to December of 2016 were above average over nearly the entire Arctic region and especially over the Arctic Ocean. By contrast, air temperatures over the Antarctic region for the same period were above average in some areas, such as the Antarctic Peninsula and near the pole, but below average in others.

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

Average annual sea ice extent in both polar regions was low in 2016. Throughout the year, a wave of new record lows were set for both daily and monthly extent. Record low monthly extents were set in the Arctic in January, February, April, May, June, October, and November; and in the Antarctic in November and December.

For the Arctic, the year opened with daily sea ice extent at near record low levels. Sea ice extent in March tied with 2015 for the lowest maximum in the 37-year satellite period. Ice extent was as much as 500,000 square kilometers (193,000 square miles) below any previous year in the record through most of mid-May to early June. However, the pace of decline returned to near-average rates by July, and the end-of-summer minimum sea ice extent, recorded on September 10, eventually tied for second lowest with 2007 (2012 remains the lowest in the satellite time series by more than 600,000 square kilometers or 232,000 square miles).

That September 2016 did not see a new record low is likely due to the unusually stormy atmospheric pattern that set up over the Arctic Ocean in the summer. Storm after storm moved into the central Arctic Ocean, including a pair of very deep low pressure systems in late August. While a stormy pattern will tend to chew up the ice cover, it also spreads the ice out to cover a larger area and typically brings cloudy and, in summer, relatively cool conditions, inhibiting melt. Sometimes these deep lows act to reduce extent by mixing warm ocean waters upwards, but at present there is no compelling evidence that this occurred in 2016.

In October, a pattern of warm air intrusions from the North Atlantic began. This pattern combined with unusually high sea surface temperatures over the Barents and Kara Seas and helped to keep Arctic sea ice extent at low levels for November and December. In the middle of November there was even a several-day period when Arctic sea ice extent decreased. Unusually warm conditions and record low daily sea ice extent levels continued through the end of the year. The unusually high sea ice surface temperatures reflect a shift in ocean circulation, enhancing the import of warm, Atlantic-derived waters into the Arctic Ocean.

In the Southern Hemisphere, overall sea ice extent shifted from near-average over the first half of the year to sharply below average in mid-August. This initiated a period of near-record, and then extreme record low extents that persisted until late in the year. While the Antarctic seasonal sea ice minimum was unremarkable (slightly earlier, and slightly lower, than the 37-year average), the sea ice maximum occurred early (August 31), followed by a period of rapid ice extent decline. By November, extent was more than 2 million square kilometers (772,000 square miles) below the 1981 to 2010 average extent. In combination with the low Arctic sea ice extent for November, this produced a remarkably low global sea ice total.

The cause of the rapid drop in Antarctic sea ice in the second half of 2016 remains elusive. Significant changes in Southern Ocean wind patterns were observed in August, September, and November, but air temperatures and ocean conditions were not highly unusual.

Sea ice cover in Chukchi Sea depends on Bering Strait inflow

Figure 5. This figure shows time series of the Julian dates of seasonal retreat and advance of sea ice in the Chukchi Sea. The trends in retreat and advance (show by the thin solid lines) are related to climate warming. The variations about the trends line are strongly related to variability in the Bering Strait heat inflow. ||Credit: Serreze, M. C., et al. 2016. Journal of Geophysical Research | High-resolution image

Figure 5. This figure shows time series of the Julian dates of seasonal retreat and advance of sea ice in the Chukchi Sea. The trends in retreat and advance (show by the thin solid lines) are related to climate warming. The variations about the trends line are strongly related to variability in the Bering Strait heat inflow.

Credit: Serreze, M. C., et al. 2016. Journal of Geophysical Research

High-resolution image

A recent study by NSIDC scientists Mark Serreze, Julienne Stroeve, and Alexander Crawford, along with University of Washington scientist Rebecca Woodgate, demonstrates strong links between seasonal sea ice retreat and advance in the Chukchi Sea and the inflow of ocean heat into the region through the Bering Strait. The Chukchi Sea region is important as a focus for resource exploration, and vessels transiting the Arctic Ocean must inevitably pass through it. The Chukchi Sea is also part of the seasonal migration route for Bowhead whales that supports subsistence hunting by local indigenous communities.

Serreze and colleagues looked at time series of the date of retreat and advance in which linear trends related to general warming were removed. They found that 68 percent of the variance in the date that ice retreats from the continental shelf break in the Chukchi Sea in spring can be explained by fluctuations in the April through June Bering Strait oceanic heat inflow. The Bering Strait heat inflow data comes from a mooring located within the strait maintained by the University of Washington. They also found that 67 percent of the variance for the date at which ice advances back to the shelf break in autumn and winter can be related to the combined effects of the July through September Bering Strait inflow and the date of ice retreat. When seasonal ice retreat occurs early, low-albedo open water areas are exposed early, which gain a lot of energy from the sun. With more heat in the upper ocean, autumn ice growth is delayed. These relationships with the Bering Strait inflow and ocean heat uptake are superimposed upon the overall trends due to a warming climate. While these relationships lay a path forward to improving seasonal predictions of ice conditions in the region, developing an operational prediction scheme would require more timely acquisition of Bering Strait heat inflow data than is presently possible.

Global sea ice tracking far below average

Figure 6. This time series of daily global sea ice extent (Arctic plus Antarctic) shows global extent tracking below the 1981 to 2010 average. The lower axis of the graph shows month of the year, ticked at the first day of the month

Figure 6a. This time series of daily global sea ice extent (Arctic plus Antarctic) shows global extent tracking below the 1981 to 2010 average. The X axis shows the month of the year, aligned with the first day of the month. Sea Ice Index data.

Credit: NSIDC
High-resolution image

Figure 6b. Waiting for caption. Lorem ipsum. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 6b. This graph shows daily global sea ice difference from average, relative to the 1981 to 2010 reference period in square kilometers for the satellite record from 1979 through 2016

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

Figure 6c. Waiting for caption. Lorem ipsum. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 6c. This graph shows daily sea ice difference from average in units of the standard deviation (based on 1981-2010 variation from the average) for this period.

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

Global sea ice (Arctic plus Antarctic) continues to track at record low levels in the satellite record, but the deviation from average has moderated compared to what was observed in November. This reflects a December pattern of faster-than-average growth in the Arctic, and slightly slower-than average sea ice extent decline in the Southern Ocean. The gap between the 1981 to 2010 average and the 2016 combined ice extent for December now stands at about 3.0 million square kilometers (1.16 million square miles), down from a peak difference of just over 4 million square kilometers (1.50 million square miles) in mid-November. This globally combined low ice extent is a result of largely separate processes in the two hemispheres.

Changes to our graphics for 2017

 Figure 7. This comparison shows the changes that will be made to NSIDC time series graphs.

Figure 7. This comparison shows the changes that will be made to NSIDC time series graphs.

Credit: NSIDC
High-resolution image

NSIDC is transitioning the sea ice extent time series graphs to show interquartile and interdecile ranges, with the median extent value, in place of standard deviations and the average values. Standard deviations are most useful with data that are clustered towards the average, or “normally distributed” like a bell curve, with few outliers. Sea ice extent data, however, has become skewed due to the strong downward trend in ice extent, with a wider spread of values and more values falling at the low end of the range. Interquartile and interdecile ranges, along with the median value, are better for presenting data with these characteristics. The interquartile and interdecile ranges more clearly show how the data are distributed and can better distinguish outliers, and so provide a better view of the variability of the data.

Further reading

Serreze, M. C., A. Crawford, J. C. Stroeve, A. P. Barrett, and R. A. Woodgate. 2016. Variability, trends and predictability of seasonal sea ice retreat and advance in the Chukchi Sea. Journal of Geophysical Research, 121, doi:10.1002/2016JC011977.

Sluggish ice growth in the Arctic

After a quick initial freeze-up during the second half of September, ice growth slowed substantially during early October. On October 20, 2016, Arctic sea ice extent began to set new daily record lows for this time of year. After mid-October, ice growth returned to near-average rates, but extent remained at record low levels through late October. High sea surface temperatures in open water areas were important in limiting ice growth. October air temperatures were also unusually high, and this warmth extended from the surface through a considerable depth of the atmosphere.

Overview of conditions

Figure 1. Arctic sea ice extent for October 2016 was 6.40 million square kilometers (2.5 million square miles). The magenta line shows the 1981 to 2010 median extent for that month.

Figure 1. Arctic sea ice extent for October 2016 was 6.40 million square kilometers (2.5 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

In October 2016, Arctic sea ice extent averaged 6.40 million square kilometers (2.5 million square miles), the lowest October in the satellite record. This is 400,000 square kilometers (154,400 square miles) lower than October 2007, the second lowest October extent, and 690,000 square kilometers (266,400 square miles) lower than October 2012, the third lowest. The average extent was 2.55 million square kilometers (980,000 square miles) below the October 1981 to 2010 long-term average.

As of early November, extent remains especially low within the Beaufort, Chukchi, East Siberian, and Kara Seas. Since the beginning of October, ice growth occurred primarily in the Laptev Sea, stretching from the New Siberian Islands towards the coast. Little ice growth occurred in the Kara and Barents Seas, while ice extent increased in the Chukchi and Beaufort Seas.

Conditions in context

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

Figure 2a. The graph above shows Arctic sea ice extent as of November 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 2b. Sea surface temperatures were unusually high over the Chukchi and Beaufort seas, as well as the Barents and Kara seas along the Eurasian coast, helping to limit ice growth. This figure shows conditions on October 25, 2016.

Figure 2b. Sea surface temperatures (SSTs) in October were unusually high over the Chukchi and Beaufort Seas, as well as the Barents and Kara Seas along the Eurasian coast, helping to limit ice growth. This figure shows SSTs on October 25, 2016.

Credit: Climate Change Institute/University of Maine
High-resolution image

Figure 2c. Air temperatures at the 925 hPa level were usually high over the Beaufort and Chukchi seas and the East Greenland Sea (up to 8 degrees Celsius or 14 degrees Fahrenheit above average).

Figure 2c. Air temperatures at the 925 hPa level were usually high over the Beaufort and Chukchi Seas and the East Greenland Sea (up to 8 degrees Celsius or 14 degrees Fahrenheit above average).

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

Figure 2d. This latitude by height cross section shows that for the Arctic as a whole, air temperatures were above average not just at or near the surface but through a deep later of the atmosphere. This manifest the combined effects of high sea surface temperatures in open water areas and the effects of atmospheric circulation drawing warm air into the region.

Figure 2d. This latitude by height cross section shows that for the Arctic as a whole, air temperatures were above average not just at and near the surface but through a deep layer of the atmosphere. This resulted from the combined effects of high sea surface temperatures in open water areas and the effects of atmospheric circulation drawing warm air into the region.

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

After an early rapid freeze-up in late September, the rate of ice growth slowed in the first half of October. From October 1 to 15, ice extent increased only 378,000 square kilometers (146,000 square miles), less than a third of the 1981 to 2010 average gain for that period. By October 31, Arctic sea ice extent stood at 7.07 million square kilometers (2.73 million square miles), the lowest extent in the satellite record for that date.

A primary culprit behind the slow growth is that sea surface temperatures in the Beaufort and Chukchi Seas, the Barents and Kara Seas along the Eurasian coast, as well as the East Siberian Sea, were above average. The open water areas in the highest latitudes at the date of the minimum in September had only recently formed and there was little input of solar radiation so far north. So those waters were just above the freezing point. When the atmosphere cooled in September, ice formed rapidly. However, further south, the sea ice had retreated far earlier in the season and a lot of solar energy was absorbed through the summer. This ocean heat inhibited the growth of ice in these regions. Finally toward the end of October, the surface ocean heat began to dissipate, triggering ice formation. However, even by October 25, sea surface temperatures were above average in these areas (Figure 2b).

The atmospheric circulation also played a role. October air temperatures at the 925 hPa level (about 2,500 feet above sea level) were unusually high over most of the Arctic Ocean (Figure 2c), especially over the Beaufort and Chukchi Seas and over the East Greenland Sea (up to 8 degrees Celsius or 14 degrees Fahrenheit above the 1981 to 2010 average). In part, these high temperatures resulted from high sea surface temperatures over the open water areas. However, unusually high sea level pressure centered over northern Scandinavia brought southerly winds from the East Siberian and Barents Seas, contributing to high air temperatures in these regions. In turn, unusually low pressure on the Pacific side centered roughly over the western Bering Sea brought southerly winds over the Beaufort and Chukchi Seas, contributing to unusually high air temperature there. The combined effects of the high sea surface temperatures and atmospheric circulation led to a pattern in which for the Arctic, unusual warmth in October extended from the surface through a deep layer of the atmosphere (Figure 2d).

As noted in our post last month, the Arctic is losing it’s oldest and thickest ice. A new animation from NASA Goddard’s Scientific Visualization Studio shows this loss over the past 30 years. 

October 2016 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2016 shows a decline of 7.4 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly October ice extent for 1979 to 2016 shows a decline of 7.4 percent per decade.

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

Through 2016, the linear rate of decline for October is 66,400 square kilometers or (25,600 square miles) per year, or 7.4 percent per decade.

Antarctic sea ice dropping

Figure 4. Antarctic sea ice extent for October 2016 was 17.6 million square kilometers (6.8 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole.

Figure 4. Antarctic sea ice extent for October 2016 was 17.6 million square kilometers (6.8 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole. Sea Ice Index data. About the data

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

After a reaching its maximum extent unusually early and then following a period of relatively unchanging overall extent, Antarctic sea ice extent started to decline in earnest. Daily sea ice extent levels have been at second lowest in the satellite record since October 20 and below the two standard deviation range. Only the 1986 austral spring extent is lower. Ice extent is particularly low on both sides of the Antarctic Peninsula. The rapid early reduction in sea ice cover in this region may create favorable conditions for the break up of the eastern Peninsula ice shelves at the end of austral summer. Similar sea ice trends and weather conditions were present during the spring seasons preceding past ice shelf retreats (e.g., 2001 to 2002). Extensive open water, created by the downsloping fosters warmer air and surface melting, and allows longer-period ocean waves to reach the ice front of the ice shelves. Other areas of reduced sea ice cover are the Southern Ocean north of Dronning Maud Land, and the area west of the Ross Sea and north of Wilkes Land.

2016 ties with 2007 for second lowest Arctic sea ice minimum

Arctic sea ice appears to have reached its seasonal minimum extent for 2016 on September 10. A relatively rapid loss of sea ice in the first ten days of September has pushed the ice extent to a statistical tie with 2007 for the second lowest in the satellite record. September’s low extent followed a summer characterized by conditions generally unfavorable for sea ice loss.

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 10, 2016 was 4.14 million square kilometers (1.60 million square miles). The orange line shows the 1981 to 2010 median extent for that day.

Figure 1. Arctic sea ice extent for September 10, 2016 was 4.14 million square kilometers (1.60 million square miles). The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

On September 10, Arctic sea ice extent stood at 4.14 million square kilometers (1.60 million square miles). This appears to have been the lowest extent of the year and is tied with 2007 as the second lowest extent on record. This year’s minimum extent is 750,000 square kilometers (290,000 square miles) above the record low set in 2012 and is well below the two standard deviation range for the 37-year satellite record. Satellite data show extensive areas of open water in the Beaufort and Chukchi seas, and in the Laptev and East Siberian seas.

During the first ten days of September, the Arctic lost ice at a faster than average rate. Ice extent lost 34,100 square kilometers (13,200 square miles) per day compared to the 1981 to 2010 long-term average of 21,000 square kilometers (8,100 square miles) per day. The early September rate of decline also greatly exceeded the rate observed for the same period in 2012 (19,000 square kilometers, or 7,340 square miles, per day). Recent ice loss has been most pronounced in the Chukchi Sea. This may relate to the impact of two strong cyclones that passed through the region during August.

Satellite passive microwave data and images from the Moderate Resolution Imaging Spectroradiometer (MODIS) suggest that the southern Northwest Passage routes are still open. While the passive microwave data show that the Northern Sea route is open, MODIS data reveal a narrow band of scattered sea ice blocking the passage near the Taymyr Peninsula.

Conditions in context

Figure 2a. The graph shows Arctic sea ice extent as of September 12, 2016, along with daily ice extent data for four other record low years. 2016 is shown in blue, 2015 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.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph shows Arctic sea ice extent as of September 12, 2016, along with daily ice extent data for four other record low years. 2016 is shown in blue, 2015 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.

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

Figure 2b. This plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius and sea level pressure anomalies for two periods: July 1 to August 31, and September 1 through September 11. Yellows and reds indicate higher than average temperatures and pressure; blues and purples indicate lower than average temperatures and pressure.

Figure 2b. This plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius and sea level pressure anomalies for two periods: July 1 to August 31, and September 1 through September 11. 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
High-resolution image

Weather in early September was warm along the Siberian coast (up to 9 degrees Celsius or 16 degrees Fahrenheit above average), with high pressure over the same region and strong winds across the central Arctic. However, as discussed in previous posts, weather over the Arctic Ocean this past summer has been generally stormy, cool, and cloudy—conditions that previous studies have shown to generally limit the rate of summer ice loss. That September ice extent nevertheless fell to second lowest in the satellite record is hence surprising. Averaged for July through August, air temperatures at the 925 hPa level (about 2,500 feet above sea level) were 0.5 to 2 degrees Celsius (1 to 4 degrees Fahrenheit) below the 1981 to 2010 long-term average over much of the central Arctic Ocean, and near average to slightly higher than average near the North American and easternmost Siberian coasts. Reflecting the stormy conditions, sea level pressures were much lower than average in the central Arctic during these months.

Why did extent fall to a tie for second lowest with 2007? The 2016 Arctic melt season started with a record low maximum extent in March, and sea ice was measured at record low monthly extents well into June. Computer models of ice thickness, and maps of sea ice age both indicated a much thinner ice pack at the end of winter. Statistically, there is little relationship between May and September sea ice extents after removing the long-term trend, indicating the strong role of summer weather patterns in controlling sea ice loss. However, the initial ice thickness may play a significant role. As noted in our mid-August post, the upper ocean was quite warm this summer and ocean-driven melting is important during late summer. The science community will be examining these issues in more detail in coming months.

Ice loss primarily in the northern Chukchi Sea

Figure 4. This figure compares Arctic sea ice extent for September 1 (orange) and September 10 (blue), with overlap areas in purple.

Figure 4. This figure compares Arctic sea ice extent for September 1 (orange) and September 10 (blue), with overlap areas in purple.

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

The late season ice loss appears to have been greatest in an extended area of patchy ice reaching from the eastern Beaufort Sea to the northern Chukchi Sea. This is in the area influenced by the two strong cyclones discussed in our August posts—the strong winds appear to have compacted the ice cover and may have led to an upward mixing of warm ocean water.

 

Second opinion

Figure 5. This graph compares Arctic sea ice extent trends from August 15 to September 10 for the years 2007 (F-17), 2012 (F-17), and 2016 (F-17 and F-18). The NSIDC Sea Ice Index currently uses data from the F-18 satellite.

Figure 5. This graph compares Arctic sea ice extent trends from August 15 to September 10 for the years 2007 (F-17), 2012 (F-17), and 2016 (F-17 and F-18). The NSIDC Sea Ice Index currently uses data from the F-18 satellite.

Credit: W. Meier, NASA GSFC, NSIDC
High-resolution image

The Defense Meteorological Satellite Program (DMSP) F-17 satellite, which NSIDC ceased to use in May as its primary source for sea ice extent due to erratic data, has since re-stabilized and is providing more consistent day-to-day readings. While NSIDC will continue to use the DMSP F-18 satellite for data processing, it is instructive to examine the F-17 record. Early September extent from the F-17 record is slightly higher than from F-18. Both sensors indicate that the minimum extent for 2016 is slightly lower than the 2007 minimum, which was 4.15 million square kilometers (1.60 million square miles) and reached on September 18. However, the measurement accuracy is about ±25,000 square kilometers (±9,600 square miles) for a five-day trailing average daily extent measurement. This means that at the present levels, 2016 is a statistical tie for second lowest sea ice extent.

Previous minimum Arctic sea ice extents

Table 1.   Previous minimum Arctic sea ice extents
 YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
2007 4.15 1.60 Sept. 18
2008 4.59 1.77 Sept. 20
2009 5.12 1.98 Sept. 13
2010 4.62 1.78 Sept. 21
2011 4.34 1.67 Sept. 11
2012 3.39 1.31 Sept. 17
2013 5.06 1.95 Sept. 13
2014 5.03 1.94 Sept. 17
2015 4.43 1.71 Sept. 9
2016 4.14 1.60 Sept. 10
1979 to 2000 average 6.70 2.59 Sept. 13
1981 to 2010 average 6.22 2.40 Sept. 15

Ten lowest minimum Arctic sea ice extents (satellite record, 1979 to present)

Table 2.  Ten lowest minimum Arctic sea ice extents (satellite record, 1979 to present)
 RANK  YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
1 2012 3.39 1.31 Sept. 17
2

 

2016

2007

4.14

4.15

1.60

1.60

Sept. 10

Sept. 18

3 2011 4.34 1.67 Sept. 11
4 2015 4.43 1.71 Sept. 9
5 2008 4.59 1.77 Sept. 20
6 2010 4.62 1.78 Sept. 21
7 2014 5.03 1.94 Sept. 17
8 2013 5.06 1.95 Sept. 13
9 2009 5.12 1.98 Sept. 13
10 2005 5.32 2.05 Sept. 22

Note that the dates and extents of the minima have been re-calculated from what we posted in previous years. In June 2016, NSIDC transitioned to using data from the DMSP F-18 satellite, due to issues with the F-17 satellite. Data beginning April 1, 2016 are from F-18. In July 2016, Sea Ice Index data were updated to Version 2. These changes do not significantly affect sea ice trends and year-to-year comparisons, but in some instances users may notice small changes in values from the previous version of the data. Details on the changes are discussed in the Sea Ice Index documentation.

October 19, 2016: We revised the title for Table 2 from “Ten lowest minimum Arctic sea ice extents (1981 to 2010 average)” to “Ten lowest minimum Arctic sea ice extents (satellite record, 1979 to present)”

 

 

 

 

 

 

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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
High-resolution image

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.