On September 13, Arctic sea ice appears to have reached its seasonal minimum extent of 4.64 million square kilometers (1.79 million square miles), the eighth lowest in the 38-year satellite record. The overall rate of ice loss this summer was slowed by a persistent pattern of low sea level pressure focused over the central Arctic Ocean.

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 13, 2017 was 4.64 million square kilometers (1.79 million square miles), the eighth lowest in the satellite record. The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

On September 13, 2017, sea ice extent reached an annual minimum of 4.64 million square kilometers (1.79 million square miles). This was 1.58 million square kilometers (610,000 square miles) below the 1981 to 2010 median extent for the same day, and 1.25 million square kilometers (483,000 square miles) and 500,000 square kilometers (193,000 square miles) above the 2012 and 2016 extents for the same day, respectively.

During the first two weeks of September, the ice edge continued to retreat in the Chukchi, East Siberian, and Kara Seas, whereas it slightly expanded in the Beaufort and Laptev Seas. The ice edge remains far to the north of its average position in the Chukchi Sea. The Northern Sea Route is largely open; Amundsen’s Northwest Passage (the southern route) has up to 50 percent ice cover in some places, though as noted in our last post, ships have successfully navigated through the southern route with icebreaker assistance. The northern Northwest Passage route, entered from the west via McClure Strait, remains choked by consolidated, thick, multi-year ice.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 17, 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 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
High-resolution image

Figure 2b. This image shows average sea level pressure over the Arctic Ocean for the period of September 1 to 16, 2017.

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

The date of the minimum ice extent for 2017 was two days earlier than the average minimum date of September 15. The earliest annual sea ice minimum in the satellite record occurred on September 5 in the years 1980 and 1987, and the latest on September 23, 1997.

As is typical of this time of year when the solar radiation received at the surface is quickly waning, the rate of ice loss slowed during the first half of September. Ice retreat from the beginning of September until the minimum averaged 25,300 square kilometers (9,770 square miles) per day, slightly faster than the 1981 to 2010 average for the same period of 22,800 square kilometers (8,800 square miles) per day.

The pattern of low sea level pressure over the central Arctic Ocean that persisted through this summer and inhibited summer ice loss has broken down. For the first half of September, the pattern has instead been one of above-average sea level pressure centered over the Barents Sea and extending across part of the Arctic Ocean (Figure 2b). Corresponding air temperatures at the 925 hPa level (about 2,500 feet above sea level) were above average over most of the Arctic Ocean. Above average temperatures over some parts of the Arctic Ocean likely reflect heat transfer to the atmosphere from areas of open water, hence cooling the ocean.

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

Effects of seasonal ice retreat in the Beaufort and Chukchi Seas

Figure 3. This chart shows combined sea ice extent in the Chukchi and Beaufort Seas from August 15 to October 7 for the years 2006 to 2016, including the extent so far for 2017. The colored dots show the day the minimum occurred in the region during a specific year. Data are from the Multisensor Analyzed Sea Ice Extent (MASIE) product.

Credit: Courtesy R. Thoman/National Weather Service Alaska Region Environmental and Scientific Services Division
High-resolution image

According to a report by the Alaska Dispatch News, the lack of sea ice forced walruses to the shore of Alaska’s Chukchi Sea earlier than any time on record. The lack of ice also forced biologists monitoring Alaska polar bears to cut short their spring field season. In turn, the NOAA National Weather Service Climate Prediction Center states that because of the extensive open water, air temperatures over the Beaufort and Chukchi Seas and along the North Slope of Alaska will likely be far above average through this autumn.

Rick Thoman of the National Weather Service in Fairbanks, Alaska compiled an analysis of the combined Chukchi and Beaufort Seas ice extent from the Multisensor Analyzed Sea Ice Extent (MASIE) product. MASIE is based on operational ice analyses at the U.S. National Ice Center and is archived and distributed by NSIDC. It shows that 2017 tracked near record lows for the region through much of the summer, but after mid-August the pace of ice loss slowed relative to recent years. While it appears unlikely that extent in the Beaufort and Chukchi Seas will reach a record low (set in 2012), it will still be among the four or five lowest in the MASIE record (Figure 3). Note that the range in dates for the minimum extent in the region differs from those for the Arctic as a whole and tend to be later, ranging from September 10 in 2015 to September 25 in 2007 and 2008. In other words, the Chukchi and Beaufort Seas may continue to lose ice even after the overall Arctic minimum extent is reached. From the passive microwave data (not shown), the Chukchi/Beaufort minimum has occurred as early as August 14 in 1980 to as late as October 2 in 1991.

Antarctic sea ice approaching winter maximum

Figure 4a. The graph above shows Antarctic sea ice extent as of September 17, 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, 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 map shows Antarctic sea ice concentration on September 16, 2017. Note the Maud Rise polynya at the top of the image. Data are from the Advanced Microwave Scannig Radiometer 2 (AMSR2).

Credit: G. Heygster, C. Melsheimer, J. Notholt/Institute of Environmental Physics, University of Bremen
High-resolution image

Following the record low summer minimum extent in March, Antarctic sea ice extent is now nearing its winter maximum. This will likely be among the five lowest winter extents in the satellite era. As of mid-September, Antarctic ice extent was just under 18 million square kilometers (7 million square miles), which is approximately half a million square kilometers below the 1981 to 2010 median ice extent. Sea ice is below the typical extent in the Indian Ocean sector, the northern Ross Sea, and the northern Weddell Sea, and slightly above average extent in the northern Amundsen Sea region.

Between September 9 and September 17 of 2016, Antarctic sea ice lost nearly 100,000 square kilometers (38,600 square miles) of sea ice per day, and sea ice extent moved from near-average to a near-record-daily low by September 17. For the next 12 months Antarctic sea ice remained extremely low. Record low ice extents were set every day from November 5, 2016 to April 10, 2017. Extents averaged for November and December of 2016 were five standard deviations below average. No other 12-month period (September 2016 to August 2017) has had such persistently low sea ice extent. The year 1986 had near-record low extent for the winter period (June to December), but there were periods of near-average and even above-average ice extent earlier in the calendar year.

Beginning around September 2, an opening in the Antarctic sea ice pack formed north of Dronning Maud Land in the easternmost Weddell Sea (near 64°S, 5°E). By mid-September, this opening, or polynya, had grown to about 12,000 square kilometers (4,600 square miles). This feature has been observed intermittently in the Antarctic pack ice since the first satellite data became available in the 1970s. In 1974, 1975, and 1976, the polynya was much larger, averaging 250,000 square kilometers (96,500 square miles). It was absent for many years in the 1980s and 1990s. In recent years the feature has been observed sporadically and has been much smaller.

The polynya is formed when ocean currents uplift deep warm ocean water to the surface where it melts the sea ice. An oceanic plateau called the Maud Rise is responsible for forcing the vertical movement of the water. The persistence of certain atmospheric patterns, such as the southern annular mode, or SAM, is thought to play a role in driving the deep water layer against the Maud Rise.

2017 Arctic sea ice minimum animation

See the NASA animation of Arctic sea ice extent from the beginning of the melt season on March 8, 2017 to the day of the annual minimum on September 13, 2017 here.

Further reading

Gordon, A.L., Visbeck, M. and Comiso, J.C. 2007. A possible link between the Weddell Polynya and the Southern Annular Mode. Journal of Climate, 20(11), 2558-2571. doi:10.1175/JCLI4046.1

Holland, D.M. 2001. Explaining the Weddell Polynya–a large ocean eddy shed at Maud Rise. Science, 292(5522), 1697-1700. doi:10.1126/science.1059322.

Erratum

In Table 1, years 2014 and 2013 were both ranked ninth lowest. They should have been ninth and tenth respectively. This has been corrected.

Average sea ice extent for August 2017 ended up third lowest in the satellite record. Ice loss rates through August were variable, but slower overall than in recent years. Extensive areas of low concentration ice cover (40 to 70 percent) are still present across much of the Eurasian side of the Arctic Ocean.

Overview of conditions

Figure 1. Arctic sea ice extent for August 2017 was 5.51 million square kilometers (2.13 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
High-resolution image

Arctic sea ice extent for August 2017 averaged 5.51 million square kilometers (2.13 million square miles), the third lowest August in the 1979 to 2017 satellite record. This was 1.77 million square kilometers (683,000 square miles) below the 1981 to 2010 average, and 800,000 square kilometers (309,000 square miles) above the record low August set in 2012.

Ice retreat was most pronounced in the western Beaufort Sea. A large region in the Beaufort Sea and East Siberian Sea has low concentration sea ice (40 to 70 percent). Patches of low concentration sea ice and some open water northeast of the Taymyr Peninsula are also present.

While a record low minimum extent in the Arctic is unlikely this year, the ice edge in the Beaufort Sea is extremely far north. In parts of this region, the ice edge is farther north than at any time since the satellite record began in 1979. This highlights the pronounced regional variability in ice conditions from year to year. A couple of the models that contribute to the Sea Ice Prediction Network Sea Ice Outlooks forecasted significantly less ice in the Beaufort Sea in July this year compared to average conditions.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 5, 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 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
High-resolution image

Figure 2b. This image shows average sea level pressure in millibars over the Arctic for the month of August 2017.

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

Over the month, low atmospheric pressure prevailed over much of the Arctic Ocean, centered over the northern Beaufort Sea (Figure 2b). This helped to push the ice edge in that region northward. Summers dominated by low pressure, as has been the case for 2017, are generally not conducive to ice loss. Low pressure brings generally cool conditions and the cyclonic (counterclockwise) winds help spread the ice over a larger area. However, it appears that strong individual storms, such as the intense summer cyclone of 2012, may break up the ice and mix warm ocean waters into the sea ice, contributing to ice loss.

August 2017 compared to previous years

Figure 3. Monthly August ice extent for 1979 to 2017 shows a decline of 10.5 percent per decade.

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

The linear rate of decline for August 2017 is 76,300 square kilometers (29,000 square miles) per year, or 10.5 percent per decade. The daily ice loss rate was variable over the month, slowing considerably during the middle and end of the month. Overall, the loss rate during August 2017 was slower than recent years, particularly 2012, when extent decreased rapidly during the first half of the month after a the passage of a strong storm.

A report on the Northwest Passage

Figure 4a. This shows the route of the Crystal Serenity (yellow line) overlaid on a map of ice cover in the Northwest Passage region for September 5, 2017.

Credit: Canadian Ice Service Daily and Regional Ice Charts
High-resolution image

Figure 4b. This chart shows sea ice area in the Parry Channel region of the Canadian Archipelago from April 30 to November 26 for the years 2010 (magenta), 2011 (dashed green), 2014 (blue green), 2016 (purple), and 2017 (red). The black line shows the 1981 to 2010 long-term average.

Credit: Environment and Climate Change Canada
High-resolution image

Figure 4c. This photo shows sea ice conditions along the route of the Crystal Serenity.

Credit: C. Haas, York University
High-resolution image

Of particular interest each year are the ice conditions in the Northwest Passage. Our colleagues, Stephen Howell and Michael Brady of the Climate Research Division at Environment and Climate Change Canada, provided a status update based on sea ice charts produced by the Canadian Ice Service.

As of August 28, the northern route of the Northwest Passage was blocked by high concentration ice at the western (Parry Channel) entrance (Figure 4a), but overall extent in the passage is still tracking below the 1981 to 2010 average (Figure 4b). The record low seasonal extent in the northern route was in 2011. Low ice years in the northern route are typically the result of early breakup associated with above-average sea level pressure over the Beaufort Sea and Canadian Basin; this pattern tends to displace ice away from the western entrance. Conversely, low sea level pressure over the Beaufort Sea, such as seen this summer, packs ice up against the western entrance. It is unlikely the northern route will open in this year. Ice concentrations are much milder in the southern route (Amundsen’s Passage) but some ice still blocks the eastern part of that passage. This is primarily first year ice that may melt out in the coming weeks. During low ice summers, thick multi-year ice originating from the Arctic Ocean is typically advected into the channels of both the northern and southern routes, representing a significant hazard to transiting ships.

The Crystal Serenity luxury cruise ship, accompanied by an icebreaker, is attempting a repeat of last year’s cruise through the passage. Professor Christian Haas of York University in Toronto, who is providing sea ice expertise on board the ship, sent us a first-hand account of conditions:

“On August 29 and 30, we encountered some high concentration ice, up to 90 percent, just before entering Bellot Strait. The ice was mostly first-year ice, with about 30 percent multi-year ice having thicknesses greater than 2 meters (6.5 feet). Due to the relatively severe ice conditions, we were supported by the Canadian Coast Guard icebreaker Des Groseilliers, which helped clear some ice on our route into Franklin Strait. Overall, ice conditions have been much more severe than during the first transit of the Northwest Passage of the Crystal Serenity in 2016, when no ice was encountered at all.”

Figure 4c shows conditions along the route. The ship’s latest position is available at the cruise’s blog.

Also of note, the Finnish icebreaker MSV Nordica, set a new record for the earliest transit through the passage on July 29, traveling 10,000 kilometers (6,000 miles) in 24 days.

On the other side of the Arctic, the Northeast Passage (or Northern Sea Route) along the coast of Siberia appears largely open as shown by NSIDC data, though operational analysis by the U.S. National Ice Center shows some remaining ice along the coast of the Taymyr Peninsula.

A radar view of the Arctic

Figure 5. This figure shows a composite image from Sentinel-1 SAR imagery for August 29, 2017 overlaid with passive microwave sea ice concentration from the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2) sensor. Red/pink shades indicate regions of high (more than 90 percent) concentration, while green/brown shades indicate lower (~30-70 percent) concentration. Open water is in black to blue/gray shades. Open water is evident between floes of ice in the low concentration regions.

Credit: Image from Danish Technical University, courtesy Leif Pedersen and Roberto Saldo
High-resolution image

The passive microwave satellite imagery that NSIDC uses is ideal for showing long-term changes in sea ice because it provides a continuous record extending back to 1979. Its drawback is low spatial resolution. Satellite radar images, though more limited in spatial and temporal coverage, provide a more detailed picture of the ice cover. A daily composite of images from the European Space Agency’s Sentinel-1 satellite, with a synthetic aperture radar (SAR) instrument, shows substantial open water well within the ice pack, north of 80° N latitude.

A cooler than average first half of the month kept ice loss at a sluggish pace with little change in the ice edge within the eastern Arctic. Retreat was mostly confined to the western Beaufort and northern Chukchi seas. Ice extent remains above that seen in 2012 and 2007.

Overview of conditions

Figure 1. Arctic sea ice extent for August 21, 2017 was 5.27 million square kilometers (2.03 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

On August 21, 2017, ice extent stood at 5.27 million square kilometers (2.03 million square miles). This was 1.82 million square kilometers (703,000 square miles) below the 1981 to 2010 median extent for the same day, and 804,000 square kilometers (310,000 square miles) and 221,000 square kilometers (85,000 square miles) above the 2012 and 2007 extents for the same day, respectively. The ice edge remained nearly constant through the first half of the month in the Barents and Kara Seas, and retreated only slightly within the East Greenland Sea. The ice edge also remained stable in the Laptev and East Siberian Seas through the first half of the month. Ice retreat occurred primarily within the Chukchi and western Beaufort Seas as well as near the New Siberian Islands. Some ice continues to block the Northern Sea Route near Severnaya Zemlya. Both McClure Strait and the Amundsen Gulf routes within the Northwest Passage remain blocked by ice. On August 17, the Russian nuclear powered icebreaker 50 let pobedy reached the North Pole in just 79 hours, the fastest time yet.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 21, 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 as a dashed line. 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

Ice retreat from August 1 to August 21 averaged 73,000 square kilometers (28,000 square miles) per day. This was faster than the 1981 to 2010 average rates of ice loss of 57,300 square kilometers (22,000 square miles) per day, but slower than in 2012, which exhibited the fastest rate of ice loss compared to any other August in the passive microwave satellite data record. Normally the rate of ice retreat slows in August as the sun starts to dip lower in the sky. The rate of ice loss was more rapid at the beginning of August, slowing down considerably starting on August 17.

Air temperatures the first two weeks of August were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) cooler than the 1981 to 2010 average throughout the Arctic Ocean and over Greenland and the North Atlantic. The lowest air temperatures relative to the long-term average were found in coastal regions of the Kara and Barents Seas, continuing the pattern seen throughout much of this summer. Cooler than average conditions within the Central Arctic were a result of persistent cold-core cyclones. These cyclones have not been as large or as strong as the Great Arctic Cyclones of 2012 and 2016, despite the central pressure of one of these systems dropping down to 974 hPa on August 10. In addition, these cyclones are located closer towards the pole within the consolidated ice pack, where they are less likely to cause significant ice loss, as did the 2012 Great Arctic Cyclone in the Chukchi Sea.

While air temperatures start to drop in August, ice melt continues through the month as heat gained in the ocean mixed layer during summer continues to melt the ice from below and from the sides. Sea surface temperatures have been up to 5 degrees Celsius (9 degrees Fahrenheit) above average near the coastal regions, but generally near average or slightly below average along the ice edge in the Beaufort and Chukchi Seas.

NASA Operation IceBridge conducts summer flights

Figure 3. This photograph, taken during NASA Operation IceBridge on July 25, 2017, shows melt ponds on the surface of Arctic sea ice.

Credit: Eric Fraim/NASA
High-resolution image

NASA’s Operation IceBridge (OIB) airborne campaign flew several missions over the Greenland ice sheet this summer to study changes in Greenland outlet glaciers, as well as to observe sea ice. A recent mission collected laser altimeter data to investigate sea ice thickness changes resulting from the piling up of sea ice (or convergence) as ice motion pushes the ice up against the coast. Flights were completed on July 17 and July 25. High-resolution visible imagery collected on the flights also provides close-up looks of melt pond development.

Influence of warm Pacific water

Figure 4. This plot shows measurements of sea surface temperature from drifting buoys, along with satellite-derived sea surface temperature from NOAA and ice concentration from NSIDC for August 6, 2017. Buoy positions as of August 6 are indicated with circles. A gray dot indicates that the buoy is reporting a temperature value outside the range of -2 to 10 degrees Celsius. Red, orange, and yellow indicate higher temperatures, while blues and purples indicate lower temperatures. Whites indicate higher sea ice concentration, and grays indicate lower concentration.

Credit: University of Washington Polar Science Center
High-resolution image

This May, sea ice in the Chukchi Sea was at a record low for the satellite data record. The early retreat of ice in this region may partially be a result of unusually warm ocean temperatures in the region. As reported by Rebecca Woodgate of the University of Washington, Seattle, the Research Vessel Norseman II spent eight days in the Bering Strait and southern Chukchi Sea region to recover oceanographic moorings and whale acoustic instruments, in addition to deploying new instruments. The mooring data indicated early arrival of warm water in the strait, about a month earlier than the average, resulting in June ocean temperatures that were 3 degrees Celsius (5 degrees Fahrenheit) above average. Early intrusion of warm water in the Bering Strait back in May helped to melt sea ice from below, and may have been one of the factors for early development of open water in the region.

Arctic air temperatures and the Paris Climate Accord target

Figure 5. The bar graph, top, shows the Berkeley Earth evaluation of the ten warmest years since 1979 in the Arctic north of 80°N; the plot, middle, shows Arctic average temperatures for the period 1900 to 2016, relative to a 1951 to 1980 reference period; bottom, a map of Arctic temperature differences, in degrees Celsius, for the 2012 to 2016 period (5 years) relative to a 1981 to 2010 reference period.

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

Our past reports, and many other sources, have noted that the Arctic region is warming faster than the rest of the globe. This warming has accelerated in recent years, particularly since 2005. The ten warmest years on record for the Arctic are within the past twelve years, and 2016 was by far the warmest in the record since 1900. These observations are supported by both NOAA National Centers for Environmental Prediction (NCEP) reanalysis climate data, and by our colleagues at Berkeley Earth. Berkeley Earth is an independent climate fact- and analysis-checking group dedicated to an objective evaluation of the main claims and data sets used to support climate trends and forecasts.

One of the major statements of the recent Paris Climate Accord, dealing with heat-trapping ga reductions, is a target to hold the increase in the global average temperature to well below 2 degrees Celsius (3.6 degrees Fahrenheit) above the pre-industrial average. While this reference for the increase (pre-industrial average) is somewhat ambiguous, using reference average temperatures of either 1951 to 1980 or 1980 to 2010 for the Arctic shows that much of the area north of 80°N is already above this guideline over the past five years (2012 to 2016). As the Arctic will likely continue to warm above 2 degrees Celsius, other areas will need to warm less than that if the threshold is not to be exceeded. In general, land warms about 30 percent faster than oceans in the models, so in a global-average 2 degree Celsius warmer world, much of the global land area would have warmed more than 2 degrees Celsius.

The annual average air temperature for 2016 for the Arctic north of 80°N was more than 3.5 degrees Celsius (6.3 degrees Fahrenheit) above the 1951 to 1980 reference period, the warmest year yet, and most years during the past decade had annual average temperatures between 2 to  2.5 degrees Celsius (3.6 to 4.5 degrees Fahrenheit) above the reference period. Geographically, the NOAA NCEP reanalysis shows that recent warming is primarily located over the Arctic Ocean, and smaller warming trends are seen in the circum-Arctic land areas.

Further reading

Hawkins, E., Ortega, P., Suckling, E., Schurer, A., Hegerl, G., Jones, P., Joshi, M., Osborn, T.J., Masson-Delmotte, V., Mignot, J. and Thorne, P. 2017. Estimating changes in global temperature since the pre-industrial period. Bulletin of the American Meteorological Society, doi:10.1175/BAMS-D-16-0007.1.

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 8.21 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
High-resolution image

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. Sea Ice Index data.

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

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
High-resolution image

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.

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

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 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
High-resolution image

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.

Credit: SIPN/ARCUS
High-resolution image

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 extent nearly matched 2012 values through the first week of July, but the rate of decline slowed during the second week. Weather patterns were unremarkable during the first half of July.

Overview of conditions

Figure 1. Arctic sea ice extent for July 17, 2017 was 7.88 million square kilometers (3.04 million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

As of July 17, Arctic sea ice extent stood at 7.88 million square kilometers (3.04 million square miles). This is 1.69 million square kilometers (653,000 square miles) below the 1981 to 2010 average, and 714,000 square kilometers (276,000 million square miles) below the interdecile range. Extent was lower than average over most of the Arctic, except for the East Greenland Sea (Figure 1). Hudson Bay was nearly ice free by mid July, much earlier than is typical, but in line with what has been observed in recent years.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of July 17, 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 as a dotted brown line. 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 2b. This map compares sea ice extent for July 11 in 2017 and in 2012. White shows where ice occurred only in 2012, medium blue is where ice occurred only in 2017, and light blue is where ice occurred in both years.

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

Through the first week of July, extent closely tracked 2012 levels. The rate of decline then slowed, so that as of July 17, extent was 169,000 square kilometers (65,300 square miles) above 2012 for the same date (Figure 2a). The spatial pattern of ice extent differs from 2012, with less ice in the Chukchi and East Siberian Seas in 2017, but more in the Beaufort, Kara, and Barents Seas and in Baffin Bay (Figure 2b).

Visible imagery provides up close details

Figure 3a. This image from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) shows sea ice in the Canadian Archipelago on July 3, 2017. The blue hues indicate areas of widespread melt ponds on the surface of the ice.

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

Figure 3b. The Sentinel-2 satellite captured this image of large sea ice floes in Nares Strait on July 8, 2017.

Credit: European Space Agency
High-resolution image

Figure 3c. This false-color composite image of the Arctic is based on NASA MODIS imagery from July 4 to 10. Most clouds are eliminated by using several images over a week, but some clouds remain, particularly over the ocean areas.

Credit: NASA/Canadian Ice Service
High-resolution image

NSIDC primarily relies on passive microwave data because it provides complete coverage—night and day, and through clouds—and because it is consistent over its long data record. However, other types of satellite data, for example visible imagery from the NASA MODIS instrument on the Aqua and Terra satellites or from the European Space Agency Sentinel 2 satellite, can sometimes provide more detail. When skies clear, details of the ice cover can be seen, including leads, individual ice floes and melt ponds. For example, on July 3 in the Canadian Archipelago, 1-kilometer resolution MODIS imagery shows that the ice surface has a distinctive blueish hue due to the presence of melt ponds on the surface (Figure 3a). Higher resolution Sentinel-2 imagery (10 meters, Figure 3b) on the other hand provides up close detail on individual melt ponds on the ice floes.

The Arctic is a cloudy place, and generally, it is difficult to obtain a clear-sky image of the entire region. However, if images are compiled, or composited, over several days, most of the region may have at least some clear sky. This approach can yield a composite image that is mostly cloud-free. The Canadian Ice Service uses this approach to create a weekly nearly cloud-free composite image of the Arctic (Figure 3c). However, because the ice cover moves (typically several kilometers per day) and melts (during the summer), over the week-long composite period, fine details that can be seen in the daily imagery are not as evident because they have been “smeared” out over the week.

An ice-diminished Arctic

In response to diminishing ice extent, the US Navy has been holding a semi-annual symposium to bring together scientists, policy makers, and others to discuss the sea ice changes and their impacts. The seventh Symposium is taking place this week in Washington, DC, and will be attended by NSIDC scientists Mark Serreze, Walt Meier, Florence Fetterer, and Ted Scambos.

Tendency for warmer winters is increasing

A new study published this week in Geophysical Research Letters by Robert Graham at the Norwegian Polar Institute shows that warm winters in the Arctic are becoming more frequent and lasting for longer periods of time than they used to. Warm events were defined by when the air temperatures rose above -10 degrees Celsius (14 degrees  Fahrenheit). While this is still well below the freezing point, it is 20 degrees Celsius (36 degrees Fahrenheit) higher than average. The last two winters have seen temperatures near the North Pole rising to 0 degrees Celsius. While an earlier study showed that winter 2015/2016 was the warmest recorded at that time, the winter of 2016/2017 was even warmer.

Reference

Graham, R. M., L. Cohen, A. A. Petty, L. N. Boisvert, A. Rinke, S. R. Hudson, M. Nicolaus, and M. A. Granskog. 2017. Increasing frequency and duration of Arctic winter warming events, Geophys. Res. Lett., 44, doi:10.1002/2017GL073395.

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). 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
High-resolution image

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. Sea Ice Index data.

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

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.

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

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. 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
High-resolution image

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.

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

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.

After setting satellite-era record lows during winter, Arctic sea ice extent declined at a steady but somewhat sluggish pace during May. However, ice has retreated at a record rate in the Chukchi Sea, and open water extended to Barrow, Alaska. In the Southern Hemisphere, ice extent continues its seasonal expansion, but extent remains well below the long-term average for this time of year.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2017 was 12.74 million square kilometers (4.92 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
High-resolution image

Arctic sea ice extent for May 2017 averaged 12.74 million square kilometers (4.92 million square miles), the fourth lowest in the 1979 to 2017 satellite record. This contrasts strongly with the past several months, when extent tracked at satellite-era record lows. May 2017 extent was 710,000 square kilometers (274,000 square miles) below the 1981 to 2010 long-term average, and 660,000 square kilometers (255,000 square miles) above the previous record low set in 2016. Sea ice extent remained below average in the Pacific sector of the Arctic and in the Barents Sea, but was slightly above average in Baffin Bay and Davis Strait towards the Labrador Sea. Ice extent was at average levels in the Greenland Sea. In the Chukchi Sea, extent was at record low levels for May.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of June 6, 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, the record low year, as a dashed line. 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 2b. The plot shows differences from average for Arctic air temperatures from May 1 to 27, 2017 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 ESRL Physical Sciences Division
High-resolution image

For the Arctic as a whole, the rate of decline in Arctic sea ice extent through May was relatively slow. The May 2017 rate of decline was 42,800 square kilometers (16,500 square miles) per day, compared to the 1981 to 2010 average of 46,990 square kilometers (18,143 square miles) per day.

Sea ice was especially slow to retreat in the Atlantic sector of the Arctic, with little change in the ice edge in Baffin Bay and Davis Strait. The ice edge expanded in the Barents and Greenland Seas until the end of May, when the ice finally started to retreat. Most of the ice retreat in May occurred within the Pacific sector, particularly within the Sea of Okhotsk, and the Bering and Chukchi Seas.

Overall, air temperatures at the 925 hPa level were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) below average over Eurasia and extending over the Barents, Kara and Laptev Seas, and 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) above average over the East Siberian, Chukchi, and Beaufort Seas (Figure 2b).

May 2017 compared to previous years

Figure 3. Monthly May ice extent for 1979 to 2017 shows a decline of 2.5 percent per decade.

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

The linear rate of decline for May is 33,900 square kilometers (13,100 square miles) per year, or 2.5 percent per decade.

Low ice in the Chukchi Sea

Fig. 4a. This map shows sea ice concentration in percent coverage for the Alaska area on May 22, 2017.

Credit: NOAA National Weather Service Alaska Sea Ice Program
High-resolution image

Figure 4b. The plot shows daily May sea ice extent, in square kilometers, in the Chukchi Sea region for 2012 to 2017.

Credit: J. Stroeve/ NSIDC
High-resolution image

Figure 4c. The graph shows cumulative temperature departures from average for each year, in degrees Fahrenheit, for Barrow, Alaska from 1921 to May 2017.

Credit: Blake Moore, Alaska Climate Research Center
High-resolution image

Notably, sea ice within the Chukchi Sea retreated earlier than seen at any other time in the satellite data record. By the third week in May, open water extended all the way to Barrow, Alaska (Figure 4a). Figure 4b shows daily ice extent for May from 2012 onward in the Chuckchi Sea. The rapid retreat in 2017 stands out. A recent report by the National Oceanographic Atmospheric Administration (NOAA) indicates that the amount of open water north of 68^o N at this time of year is unprecedented.

Part of the explanation for earlier open water formation in the Chukchi Sea is the unusually high air temperatures in that region during the previous winter. It is instructive to look at the cumulative temperature departure from average for Barrow, Alaska (Figure 4c). From 1921 until about 1989, conditions at Barrow actually got progressively cooler. However, since that time, temperatures have markedly increased.

Consistent with warm conditions, extensive open water in the Chukchi Sea region persisted into December; the delayed ice growth potentially led to thinner ice than usual in spring. In addition, strong winds from the north occurred for a few days at the end of March and early April, pushing ice southward in the Bering Sea, breaking up the ice in the Chukchi Sea, and even flushing some ice out through the Bering Strait. At the same time further east near Barrow, winds helped to push ice away from the coast. Based on recent work by NSIDC and the University of Washington, the pattern of spring sea ice retreat also suggests a role of strong oceanic heat inflow to the Chukchi Sea via Bering Strait.

Impacts of low Chukchi Sea on Alaskan communities

The ARCUS Sea Ice for Walrus Outlook (SIWO) provides weekly reports from April to June on sea ice conditions in the northern Bering Sea and southern Chukchi Sea regions of Alaska to support subsistence hunters and coastal communities. While the reports are not intended for operational planning or navigation, they provide detailed ice and weather observations for the region, some made by local community members, others from operational forecast centers. The most recent update on June 2nd discusses the continued rapid deterioration of sea ice between Wales and Shishmaref, Alaska. Nearly ice-free conditions around Nome, Alaska reflect warmer waters from the Bering Sea moving into the region. Some sea ice remains attached to the shore along the northeast coast of St. Lawrence Island, but the Bering Sea is essentially ice free. Prime walrus hunting for these communities is typically in May. However, when the ice retreats early, the walrus go with it, reducing the number of walrus the local communities can hunt.

Sea ice data and analysis tools

NSIDC has released a new set of tools for sea ice analysis and visualization. In addition to Charctic, our interactive sea ice extent graph, the new Sea Ice Data and Analysis Tools page provides access to Arctic and Antarctic sea ice data organized in seven different data workbooks, updated daily or monthly. Animations of September Arctic and Antarctic month average sea ice and concentrations may also be accessed from this page.

Further Reading

Serreze, M.C., Crawford, A., Stroeve, J. C., Barrett, A.P. and Woodgate, R.A. 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.

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. Sea Ice Index data. About the data

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

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 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
High-resolution image

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
High-resolution image

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
High-resolution image

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.

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

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
High-resolution image

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 on April 2017. A researcher and a Twin Otter aircraft are obscured in the background.

Credit: J. Stroeve/NSIDC
High-resolution image

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).

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
High-resolution image

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 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
High-resolution image

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 extent for March 2017 was the lowest in the satellite record for the month. The decline in ice extent has been uneven since the seasonal maximum was reached on March 7, 2017, with a modest period of expansion towards the end of the month.

Overview of conditions

Figure 1. Arctic sea ice extent for March 2017 was 14.43 million square kilometers (5.57 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
High-resolution image

Arctic sea ice extent for March 2017 averaged 14.43 million square kilometers (5.57 million square miles), the lowest March extent in the 38-year satellite record. This is only 60,000 square kilometers (23,000 square miles) below March 2015, the previous lowest March extent, and 1.17 million square kilometers (452,000 square miles) below the March 1981 to 2010 long-term average. This month continues the record low conditions seen since October 2016.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of April 9, 2017, along with daily ice extent data for five previous years. 2017 to 2016 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
High-resolution image

Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius for March 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/ESRL Physical Sciences Division
High-resolution image

Figure 2c. The plot shows Arctic sea level pressure (in millibars) for March 2017 expressed as departures from average conditions. The dominant feature is a large area of below average pressure covering most of the Arctic Ocean.

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

The decline in sea ice extent following the March 2017 seasonal maximum was interrupted by a brief period of expansion from about March 11 to 15, a decline extending through about March 26, then another period of growth through the end of the month into early April. On April 4^th, the extent was greater than on the same day in 2016. This type of behavior is not unusual for this time of year when declines in extent in warmer, lower latitudes can be countered by periods of expansion in the still-cold higher latitudes. Shifts in wind patterns also lead to variability. Regions that experienced slight ice advance were at the end of the month in the Barents Sea and in the Bering Sea. Nevertheless, by early April, extent remained below average in the Barents Sea and in the Sea of Okhotsk and the western Bering Sea. Interestingly, ice extended further south than usual in the eastern Bering Sea.

March saw continued warmth over the Arctic Ocean. The warmest conditions for March 2017 as compared to average were over Siberia. While temperatures were still well above average along the Russian coastal seas (6 to 7 degrees Celsius, or 11 to 13 degrees Fahrenheit), those over the northern North Atlantic and the Canadian Arctic Archipelago were near average.

The dominant feature of the sea level pressure field for March 2017 was an area of below average pressure covering most of the Arctic Ocean. Locally, pressures were more than 15 millibars below the 1981 to 2010 average. This pattern points to a continuation of the stormy conditions that prevailed over the past winter and is broadly consistent with the positive phase of the Arctic Oscillation, a large-scale mode of climate variability. When the Arctic Oscillation is in its positive phase, sea level pressure is below average over the Arctic Ocean. The Arctic Oscillation has generally been in a positive phase since December. The unusually high Siberian temperatures for March 2017 are consistent with persistent winds from the south and east along the southern side of the low pressure.

March 2017 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2017 shows a decline of 2.74 percent per decade.

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

The linear rate of decline for March is 42,700 square kilometers (16,500 square miles) per year, or 2.74 percent per decade.

Report from the field

Figure 4. The team prepares to measure snow thickness over sea ice in Cambridge Bay, Canada on April 5, 2017, during an AltiKa field validation campaign. NSIDC researcher Andrew Barrett is in a red jacket; Julienne Stroeve holds a magna probe.

Credit: Isobel Lawrence
High-resolution image

As of the publication of this post, NSIDC scientists Julienne Stroeve and Andrew Barrett are in Cambridge Bay, Canada on a satellite validation campaign. Efforts focus on ground measurements of snow depth over sea ice, ice thickness, and snow structure in order to validate the joint French/Indian AltiKa Ka band radar altimeter. Coincident aircraft Ka band and LiDAR measurements allow researchers to connect measurements on the ground with those made by the satellite. Air temperatures have ranged from -20 to -5 degrees Celsius (-4 to 23 degrees Fahrenheit), with wind chills from -40 to -20 degrees Celsius (-40 to -4 degrees Fahrenheit). Dr. Stroeve will then join another field campaign operating out of Alert, Canada for further validation of AltiKa and CryoSat2 over the Lincoln Sea.

Arctic sea ice thickness

Figure 5. The graph shows sea ice volume from the PIOMAS model/observations for each year from 2010 through March 2017, and the 1979 to 2016 average (black line) and one (dark gray) and two (light gray) standard deviation ranges.

Credit: NSIDC courtesy University of Washington Polar Science Center
High-resolution image

A key early indicator for the upcoming melt season is the thickness of the sea ice. An assessment of available information suggests a fairly thin ice cover, not surprising given the warm temperatures over much of the Arctic Ocean during the winter.

Satellite data from the European Space Agency (ESA) CryoSat-2 radar altimeter, which is processed into sea ice thickness estimates at the University College London’s Center for Polar Observing and Modeling (CPOM) indicates ice along much of the Siberian coast with thicknesses of 1.5 to 2.0 meters (4.9 to 6.6 feet) or less. This is not atypical for seasonal ice; however this band of <2.0 meters of ice covers a much larger region and extends much farther north than it used to—well north of 80 degrees N latitude on the Atlantic side of the Arctic. NASA’s Operation IceBridge has also been collecting data over the past month. That data will not be available for a few weeks; a key focus of some flights has involved collaboration with ESA to collect coincident data with CryoSat-2 to help validate the satellite estimates.

Another way to estimate thickness and total ice volume is with a combination of observations and a model, which is done by the University of Washington Polar Science Center’s University of Washington Polar Science Center’s Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS). The model uses observed sea ice concentration fields to constrain the model and estimates thickness and total volume via physical simulations in the model. It shows that sea ice volume has been at record low levels throughout 2017 so far (Figure 5).

Sea ice loss and Atlantic layer heat

For many years, scientists have pondered how much of the sharp decline in summer sea ice extent and volume is due to “top down” forcing—a warmer atmosphere leading to more summer melt and less winter growth, versus “bottom up” forcing, in which ocean heat is brought to bear on the underside of the ice. There is a great deal of heat in the Arctic Ocean from waters that are imported from the Atlantic. As fairly warm and salty Atlantic water enters the Arctic Ocean it dives underneath the relatively fresh Arctic Ocean surface layer. Because the fresh surface layer has a fairly low density, the vertical structure of the Arctic Ocean is very stable. As such, it is hard to mix this Atlantic heat upwards to melt ice or keep it from forming in the first place. However, new work by an international team led by Igor Polyakov of the University of Alaska Fairbanks provides strong evidence that Atlantic layer heat is now playing a prominent role in reducing winter ice formation in the Eurasian Basin, which is manifested as more summer ice loss. According to their analysis, the ice loss due to the influence of Atlantic layer heat is comparable in magnitude to the top down forcing by the atmosphere.

Antarctic ice extent low, but on the rise

Figure 6. The graph above shows Antarctic sea ice extent as of April 9, 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. 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

Following the record-low seasonal sea ice minimum, Antarctic sea ice extent has sharply risen, but extent is still far below average, and set daily record low values throughout the month of March. Regionally, sea ice recovered to near average conditions in the Weddell Sea and around much of the coast of East Antarctica. The primary region of below average extent was in the Ross, Amundsen, and Bellingshausen Sea regions, as has been the case throughout the spring and summer. This appears to be related to warmer-than-average sea surface temperatures.

Additional reading

Polyakov, I., A.V. Pnyushkov, M.B. Alkire, I.M. Ashik, T.M. Baumann, E.C. Carmack and 10 others. 2017. Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean. Science, doi:10.1126/science.aai8204.

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. Sea Ice Index data. About the data

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

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 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
High-resolution image

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
High-resolution image

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 (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.