On September 15, Arctic sea ice likely reached its annual minimum extent of 3.74 million square kilometers (1.44 million square miles). The minimum ice extent is the second lowest in the 42-year-old satellite record, reinforcing the long-term downward trend in Arctic ice extent. Sea ice extent will now begin its seasonal increase through autumn and winter. In the Antarctic, sea ice extent is now well above average and within the range of the ten largest ice extents on record, underscoring its high year-to-year variability. The annual maximum for Antarctic sea ice typically occurs in late September or early October.

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 1a. Arctic sea ice extent for September 15, 2020 was 3.74 million square kilometers (1.44 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
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Figure 1b. The map above compares the 2012 Arctic sea ice minimum, reached on September 17, with the 2020 Arctic sea ice minimum, reached on September 15. Light blue shading indicates the region where ice occurred in both 2012 and 2020, while white and medium blue areas show ice cover unique to 2012 and to 2020, respectively. Sea Ice Index data. About the data

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

A sharp decline of Arctic sea ice at the beginning of September dropped the extent below 4.0 million square kilometers (1.54 million square miles) for only the second time since the beginning of the satellite record in 1979. After September 8, daily melt began leveling out, reaching its seasonal minimum extent of 3.74 million square kilometers (1.44 million square miles) on September 15 (Figure 1a). This appears to be the lowest extent of the year. In response to the setting sun and falling temperatures, ice extent will begin increasing through autumn and winter. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower.

Compared to 2012, the minimum extent this year has more ice in the Beaufort Sea, but somewhat less ice in the Laptev and East Greenland Sea regions (Figure 1b). The minimum extent was reached one day later than the 1981 to 2010 median minimum date of September 14. The interquartile range of minimum dates is September 11 to September 19.

The 14 lowest extents in the satellite era have all occurred in the last 14 years.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent on September 15, 2020, along with several other recent years and the record minimum set in 2012. 2019 is shown in green, 2018 in orange, 2017 in brown, 2016 in magenta, 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. This graph shows linear trends of Arctic sea ice extent for three 14-year periods for the day of the annual minimum. Trend percent values are relative to the 1981 to 2010 average minimum extent. On the right, the average (square) and range of highest and lowest extents at the minimum for each period are given.

Credit: W. Meier, NSIDC
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This year’s minimum set on September 15 was 350,000 square kilometers (135,000 square miles) above the record minimum extent in the satellite era, which occurred on September 17, 2012 (Figure 2a). It is also 2.51 million square kilometers (969,000 square miles) below the 1981 to 2010 average minimum extent, which is equivalent in size to roughly the states of Alaska, Texas, and Montana combined, or Greenland and Finland combined.

The 42-minimum-extent values in the satellite record can be broken down into three 14-year periods. Most notably, minimum extents in the last 14 years of the time series are the lowest 14 in the 42-year record (Figure 2b). All three periods show a downward trend. The middle period, 1993 to 2006, shows the steepest downward trend of 13.3 percent per decade, relative to the 1981 to 2010 average. The earliest period, 1979 to 1992, has a downward trend of 6.4 percent per decade, while the most recent period of low extents, 2007 to 2020, has a downward trend of 4.0 percent per decade.

The overall, downward trend in the minimum extent from 1979 to 2020 is 13.4 percent per decade relative to the 1981 to 2010 average.

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

Values within 40,000 square kilometers (15,000 square miles) are considered tied. The 2019 value has changed from 4.15 to 4.19 million square kilometers (1.62 million square miles) when final analysis data updated from near-real-time data.

In the first week of September, sea ice extent took a sharp downward turn, exceeding the pace of decline for any previous year during that period, and placing the 2020 sea ice minimum firmly as second lowest—after 2012—in the 42-year continuous satellite record. Pulses of warm air from north-central Siberia are responsible for the late downward trend. Sea ice decline has slowed in the past few days, and the annual minimum is imminent.

Overview of conditions

Figure 1a. Arctic sea ice extent for September 15, 2020 was 3.74 million square kilometers (1.44 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

Figure 1b. The graph above shows Arctic sea ice extent as of September 15, 2020, along with daily extent data for several low sea ice extent years and the record low year. 2020 is shown in blue, 2019 in dark green, 2018 in purple, 2007 in light green, 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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Figure 1c. This map shows sea ice concentration for Arctic sea ice on September 12, 2020, using data collected from the Japanese Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2).

Credit: University of Bremen
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Figure 1d. This figure compares Arctic sea ice extent on September 1, 2020 (in white), and September 14, 2020 (in blue), showing recent areas of retreat.

Credit: National Snow and Ice Data Center
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Sea ice extent stood at 3.74 million square kilometers (1.44 million square miles) on September 15, already well below 2007, 2016, and 2019 and within 400,000 square kilometers (154,400 square miles) of the record low extent set in 2012 (Figure 1a). Sea ice extent has dropped below 4 million square kilometers (1.54 million square miles) only once before, in 2012 (Figure 1b). Between August 31 and September 5, 2020, sea ice extent decreased by an average of 79,800 square kilometers (30,800 square miles) per day. This is a greater loss rate than any other year for these six days in the sea ice record. Ice retreat during this period was along the ice front in the northern Barents, Kara, and Laptev seas. A remaining tail of multiyear ice extends into the southern Beaufort Sea north of the Mackenzie River Delta and the Alaskan North Slope. North of Scandinavia and Russia, a very broad sea-ice-free area exists with the ice edge lying near 85 degrees N, far to the north of Svalbard, Franz Josef Land, and Severnaya Zemlya (Northern Land) (Figure 1c). The sharply defined ice edge in this area, between about 0 degrees and 100 degrees longitude, indicates strong compaction of the ice by winds coming from the south and is the furthest north the ice edge has been in this location over the satellite data record (Figure 1d).

Conditions in context

Figure 2a. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, from September 1 to 14, 2020. 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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Figure 2b. This plot shows average sea level pressure in the Arctic in millibars (hPa) from September 1 to 14, 2020. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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As assessed over the first two weeks of September, air temperatures at the 925 mb level (about 2,500 feet above sea level) were above average over much of the Eurasian side of the Arctic Ocean. Air temperatures were up to 6 degrees Celsius (11 degrees Fahrenheit) above the 1981 to 2010 average near the Taymyr Peninsula of north-central Siberia. Temperatures were 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) below average in easternmost Siberia and western Alaska, 4 degrees Celsius (7 degrees Fahrenheit) below average in central Canada, and 5 degrees Celsius (9 degrees Fahrenheit) below average in northern Greenland (Figure 2a). The atmospheric circulation over the first two weeks of the month was characterized by generally high pressure in eastern Siberia and low pressure over the Atlantic side of the Arctic, driving winds from the south over much of the Eurasian side of the Arctic Ocean (Figure 2b). The Arctic Oscillation index has cycled between slightly negative and moderately positive values. Pulses of warm air have been observed to migrate across the Arctic Ocean and then break down over a scale of several days.

Late summer sea ice drift and sea surface temperature

Figure 3a. This figure shows sea ice motion determined from National Snow and Ice Data Center EASE-Grid passive microwave data from August 26 to September 1, 2020.

Credit: National Snow and Ice Data Center
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Figure 3b. This map shows sea surface temperature (SST) in degrees Celsius and ice concentration for September 13, 2020. SST data are from the University of Washington Polar Science Center Upper layer Temperature of the Polar Oceans (UptempO) buoys and satellite-derived values from the National Oceanic and Atmospheric Administration (NOAA), and ice concentration is from the NSIDC Sea Ice Index.

Credit: University of Washington
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Ice motion in late August drifted northward along the Eurasian side of the Arctic Ocean, while the multiyear sea ice region north of western Canada and Alaska drifted rapidly westward toward the Chukchi Sea (Figure 3a). Ice motion was determined by tracking patterns in the sea ice using passive microwave and other data. Both the motion and the compaction of the loose sea ice pack are responsible for the strong decline in ice extent seen in this period and the following week. Warm waters in the Chukchi Sea may induce some late melting of the multiyear ice from the heat in the ocean, but much of the water in the region is already near freezing from more recent ice loss (Figure 3b).

Sailing across the top of the world in a “new Arctic” soon

Figure 4. This map shows the potential transpolar shipping route discussed in Bennett et al., 2020. The orange line shows the approximate September 2020 ice edge overlaid on the September 2019 Arctic sea ice extent.

Credit: Bennett et al., 2020
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A recent paper by an international group led by political geographer Mia Bennett at the University of Hong Kong discusses the potential impacts of the near-future emergence of a transpolar shipping route as sea ice retreat continues to open a very wide shipping lane along the Eurasian side of the Arctic Ocean (as it has this year). The route would pass over the North Pole as a way of avoiding an extensive Russian exclusive economic zone (EEZ) and still-contended continental shelf claim.

This emerging transpolar route reflects a fundamentally changed Arctic environment. Another recent paper by researchers Laura Landrum and Marika Holland at the National Center for Atmospheric Research found that the Arctic has indeed entered into a “new Arctic climate” state. This new climate is one characterized by warmer temperatures, more open water, less sea ice, more rain, and less snow. In the Arctic, weather that used to be considered extreme is becoming the norm. The summer of 2020 is clearly representative of this new Arctic.

Further reading

Bennett, M. M. et al. 2020. The opening of the Transpolar Sea Route: Logistical, geopolitical, environmental, and socioeconomic impacts. Marine Policy. doi.10.1016/j.marpol.2020.104178.

Landrum, L., and Holland, M. M. 2020. Extremes become routine in an emerging new Arctic. Nature Climate Change. doi.10.1038/s41558-020-0892-z.

After a period of rapid sea ice loss extending into the last week of August, the rate has slowed with the onset of autumn in the Arctic. A region of low concentration ice persists in the Beaufort Sea. How much of this ice melts over in the next two weeks will strongly determine where the September sea ice minimum will stand in the record books. The Northwest Passage (Amundsen’s route) is largely open but some ice remains. The Northern Sea Route, along the Siberian coast, remains open.

Overview of conditions

Figure 1. Arctic sea ice extent for August 2020 was 5.08 million square kilometers (1.96 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

August 2020 sea ice extent averaged 5.08 million square kilometers (1.96 million square miles), placing it at third lowest in the satellite record for the month. This was 360,000 square kilometers (139,000 square miles) above the record low set in 2012. As of September 1, Arctic sea ice extent stood at 4.26 million square kilometers (1.64 million square miles), the second lowest extent for that date in the satellite passive microwave record that started in 1979.

In our previous post, we noted the development of substantial openings of the sea ice north of Alaska within the Beaufort and Chukchi Seas, possibly related to the mid-July storm that spread out the ice cover. Since then, further melt has occurred in the area. Some of this ice appears to be multiyear, which tends to be resistant to melting away. Total sea ice extent at the September minimum will depend strongly on how much of the ice in this area melts from the remaining heat in the ocean, and on wind compaction or expansion of the overall ice edge (the line of 15 percent concentration). The Northwest Passage is largely open, but some ice remains. The Northern Sea route remains open.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 01, 2020, along with daily ice extent data for four previous years and the record low year. 2020 is shown in blue, 2019 in green, 2018 in orange, 2017 in brown, 2016 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. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, from August 15 to 31, 2020. 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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Figure 2c. This plot shows average sea level pressure in the Arctic in millibars (hPa) from August 15 to 31, 2020. Yellows and reds indicate high air pressure; blues and purples indicate low pressure.

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

Following a period of slow August ice loss, the pace quickened during the middle of the month as areas of low ice concentration melted away, only to slow again towards the end of the month with the onset of autumn in the Arctic. Overall, from August 15 through September 1, 2020, extent declined by 1.1 million square kilometers (425,000 square miles), more than the average 1981 to 2020 extent loss of 800,000 square kilometers (309,000 square miles) during the same period (Figure 2a).

As assessed from August 15 to August 31, air temperatures at the 925 mb level (about 2,500 feet above sea level) were above average over much of the Arctic Ocean, continuing the basic pattern of warmth that prevailed through the first half of the month, most notably in the Kara Sea. Temperatures were below average over central Siberia (Figure 2b). The atmospheric circulation pattern shifted relative to the first half of the month to feature high pressure centered over the Laptev Sea and extending across the Beaufort and Chukchi Seas (Figure 2c). Low pressure has been the dominant feature of the Norwegian Sea region.

August 2020 compared to previous years

Figure 3. Monthly August ice extent for 1979 to 2020 shows a decline of 10.7 percent per decade.

Credit: National Snow and Ice Data Center
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The average sea ice extent for August 2020 as a whole is 5.08 million square kilometers (1.96 million square miles), placing it third lowest in the 42-year satellite record. Including 2020, the linear rate of decline for August sea ice extent is 10.7 percent per decade. This corresponds to a trend of 76,800 square kilometers (29,700 square miles) per year, or about the size of New Hampshire, Vermont, and Massachusetts combined. Over the satellite record, the Arctic Ocean has lost about 3.15 million square kilometers (1.22 million square miles) of ice in August, based on the difference in linear trend values in 2020 and 1979. This is comparable in size to about twice the size of the state of Alaska.

Atlantification continues

As discussed in a recent paper in the Journal of Climate led by colleague Igor Polyakov of the University of Alaska, the process of “Atlantification” of the Arctic Ocean, first noted in the Barents Sea, is continuing, with significant effects on the sea ice cover during the winter season in the Eastern Eurasian Basin. The relatively fresh surface layer of the Arctic Ocean is underlain by warm, salty water that is imported from the northern Atlantic Ocean. The cold fresh surface layer, because of its lower density, largely prevents the warm, salty Atlantic waters from mixing upwards. However, the underlying Atlantic water appears to have moved closer to the surface in recent years, reducing the density contrast with the water above it. Recent observations show this warm water “blob,” usually found at about 150 meters (492 feet) below the surface, has shifted within 80 meters (263 feet) of the surface. This has resulted in an increase in the upward winter ocean heat flow to the underside of the ice from typical values of 3 to 4 watts per square meter in 2007 to 2008 to greater than 10 watts per square meter from 2016 to 2018. Polyakov estimates that this is equivalent to a two-fold reduction in winter ice growth.

Other recent news

The RV Polarstern, which has been supporting the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, conducted an impromptu detour to the North Pole, taking advantage of fairly light ice conditions. Large openings in the sea ice were present north of Greenland, an area that would normally be very difficult to traverse. The United States’ medium-duty icebreaker Healy did not fare as well—a fire broke out in the engine compartment, and although it was quickly extinguished, the damage is extensive, and with the ship temporarily out of commission, a planned expedition to the Chukchi and Beaufort Seas has been cancelled.

Antarctic sea ice: looking up down below

Figure 4. The graph above shows Antarctic sea ice extent as of September 01, 2020, along with daily ice extent data for four previous years and the record maximum extent year. 2020 is shown in blue, 2019 in green, 2018 in orange, 2017 in brown, 2016 in purple, and 2014 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

Antarctic sea ice growth in late winter has brought the ice extent substantially above average in late August for the first time in four years. Ice extent exceeded the 1981 to 2010 average over much of the Weddell Sea and off the Wilkes Land coast. A few areas of below-average extent persisted in the Davis Sea (south of Perth, Australia) and the northeastern Ross Sea. The cause appears to be persistent high air pressure in the western Weddell Sea and the Davis Sea that generate offshore cold winds on the eastern sides of the high-pressure areas. While Antarctica often has a trio of high pressure and low pressure areas surrounding it, for the second half of August there were just two such pairs.

Further reading

Polyakov, I. V., et al. 2020. Weakening of Cold Halocline Layer Exposes Sea Ice to Oceanic Heat in the Eastern Arctic Ocean. Journal of Climate, 33, 8107–8123, doi:10.1175/JCLI-D-19-0976.1.