Arctic summer 2018: September extent ties for sixth lowest

After starting the year with record lows in January and February, Arctic sea ice extent ended tied with 2008 for the sixth lowest average September extent in the satellite record. The 2018 minimum extent was reached on both September 19 and 23. September 23 is among the latest dates for the seasonal minimum in the nearly 40-year satellite record. In the Antarctic, the annual maximum extent appears to have been reached on October 2.

Overview of conditions

Figure 1. Arctic sea ice extent for September 2018 was 4.71 million square kilometers (1.82 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 1. Arctic sea ice extent for September 2018 was 4.71 million square kilometers (1.82 million square miles). The magenta line shows the 1981 to 2010 average extent for the month. Sea Ice Index data. About the data

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

Arctic sea ice extent for September 2018 averaged 4.71 million square kilometers (1.82 million square miles), tying with 2008 for the sixth lowest September in the 1979 to 2018 satellite record. This was 1.70 million square kilometers (656,000 square miles) below the 1981 to 2010 average, and 1.14 million square kilometers (440,000 square miles) above the record low recorded for September 2012. Prior to September 19, sea ice extent declined at a relatively rapid 14,440 square kilometers (5,580 square miles) per day, significantly faster than in most years. The near-zero loss rate between September 19 and 23, and the very late onset of significant seasonal ice growth after September 23, were atypical of the satellite record.

Sea ice loss during the first half of September primarily occurred within the East Siberian, northern Laptev, and northern Chukchi Seas, in part because winds from the south brought warm air into the region and inhibited ice from drifting or growing southward. Retreat in these areas was partially offset by ice expansion in the eastern Beaufort Sea and the northern Kara and Barents Seas. The old ice that had been persisting in the Beaufort Sea near Prudhoe Bay mostly melted out by the end of September. While the Northern Sea Route opened again this year, as it has every year since 2008, ice lingered in the central section of the southern route of the Northwest Passage between Bellot Strait and Gjoa Haven.

Since the seasonal minimum extent, reached on September 19 and again on September 23 at 4.59 million square kilometers (1.77 million square miles), ice cover has expanded in the Canadian Archipelago, the northern Chukchi and Beaufort Seas, and the East Greenland Sea, while retreating slightly within the Kara Sea.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of October 07, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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 plot shows the difference from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for September 2018. 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

September air temperatures at the 925 hPa level (about 2,500 feet above the surface) were from 3 to 8 degrees Celsius (5 to 14 degrees Fahrenheit) above average over the western Beaufort, Chukchi, and East Siberian Seas. As noted above, this delayed the seasonal onset of ice growth in these areas, seen in the late timing of the seasonal sea ice minimum for the Arctic as a whole, and the near-zero change in ice extent over the period September 19 to 23.

A very pronounced high pressure ridge contributed to this unusual warmth. The Capital Weather Gang reports that the high pressure ridge, which formed over the Bering Sea in early September, drifted eastward, became especially pronounced late in the month, and then expanded into the Beaufort and Chukchi Seas. This contributed to the slow freeze up after the minimum. Sunny, warm, and dry conditions spread across much of Alaska. Anchorage, Alaska experienced its warmest September on record. Air motion under a pressure ridge tends to be downwards, inhibiting the formation of clouds, rainfall, or snowfall.

 

September 2018 compared to previous years

Figure 3. Monthly September ice extent for 1979 to 2018 shows a decline of 12.8 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly September ice extent for 1979 to 2018 shows a decline of 12.8 percent per decade.

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

Sea ice extent for September 2018 fell just above the long-term linear trend line. The linear rate of sea ice decline for September is 82,300 square kilometers (32,000 square miles) per year, or 12.8 percent per decade relative to the 1981 to 2010 average.

A look back at the summer melt season

Arctic air temperature ranking at 925 hPa based on NCEP/NCAR reanalysis for all areas north of 70oN. Credit: Zachary Labe/affiliation?

Figure 4a. This graphic ranks months based on their Arctic air temperature from 1979 to 2018 at 925 hPa from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis for all areas north of 70 degrees N. Dark reds indicate warmest months; dark blues indicate coldest months.

Credit: Z. Labe, University of California, Irvine
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Figure 4b. This true color composite shows the patch of sea ice off Point Barrow, north of Utqiaġvik, Alaska, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite on September 19, 2018.

Credit: NASA Worldview
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Total sea ice extent reached record lows in January and February, and stayed at second lowest from March through May, largely due to extremely low extent in the Bering Sea. However, the September extent tied for sixth lowest in the record, slightly above the long-term trend line.

Melt began slowly over most of the western Arctic Ocean and the East Siberian Sea. As a result, despite June temperatures that were slightly above average (Figure 4a), the rate of ice loss in June of 52,800 square kilometers (20,000 square miles) per day was slightly below the 1981 to 2010 average of 56,300 square kilometers (22,000 square miles) per day. A cloudy and cool July followed, especially over the East Siberian Sea and stretching westward towards the Kara Sea. In response, ice was particularly slow to retreat in the East Siberian Sea. Indeed, July ranked as the ninth coldest July since 1979.

Puzzling in this regard is that the July ice decline rate of 105,400 square kilometers (41,000 square miles) per day, was considerably faster than the 1981 to 2010 average decline of 86,800 square kilometers (34,000 square miles) per day. Only in 2007 and 2009 did July have faster rates of ice loss. This is counter intuitive, and likely illustrates the importance of atmospheric processes in transporting ice northwards, and the role of ocean warmth in melting ice.

While July is usually the warmest month of the year, air temperatures this August exceeded those in July. This has only happened once before in the last 70 years, according to analysis of data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalyses. August air temperatures at the 925 hPa level were up to 5 degrees Celsius (9 degrees Fahrenheit) above average in the Laptev Sea. Still, the August ice loss of 57,500 square kilometers (22,000 square miles) per day was nearly identical to the 1981 to 2010 average decline. The large tongue of ice that had been persisting within the East Siberian Sea started to melt out. Above average air temperatures continued through early September, especially in the East Siberian Sea, which helped to further melt sea ice that had persisted all summer. By the end of the melt season, about 267,000 square kilometers (103,000 square miles) of ice remained in this sector. The least amount of sea ice within the East Siberian Sea was recorded in 2007 (2,980 square kilometers or 1,150 square miles). As discussed above, the late date of the sea ice minimum and the near-zero change in ice extent from September 19 to 23 reflects the influence of the very warm conditions associated with the high pressure ridge.

A patch of sea ice remained through the summer in the Beaufort Sea, northeast of Point Barrow, consisting of first-year ice interspersed with floes of more resistant multiyear ice. This patch was no longer detected in the passive microwave imagery once it became too sparse. However, ice was still evident through the end of the melt season in visible imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) (Figure 4b) and was charted in operational analyses from the Multisensor Analyzed Sea Ice Extent (MASIE).

In short, the reasons why September sea ice extent for 2018 ended up as sixth lowest, well above 2007 and 2012, remains to be fully determined. Melt onset was somewhat late, but despite cool conditions the July ice loss was rather rapid. The ice loss rate in August was near average. Further research is warranted.

The importance of ice age

Figure 5a. (a) Sea ice age during Week X and Week Y, showing the origin of patch of ice in the Beaufort Sea and the last remnant.||Credit: M. Tschudi, S. Stewart, University of Colorado, Boulder, and W. Meier, J. Stroeve, NSIDC

Figure 5a. This map shows sea ice age category during week 38 in 2018, showing the origin of the patch of ice in the Beaufort Sea and the last remnant. The age category value designates the maximum age of that ice. Click here for the full animation.

Credit: M. Tschudi, S. Stewart, University of Colorado, Boulder, and W. Meier, J. Stroeve, NSIDC
High-resolution image

Figure 5b. This time series shows multiyear ice at the end of each summer melt season since 1985. Note that these images are based on an updated soon-to-be-released version of the current sea ice age product and a near-real-time version for 2018.

Credit: M. Tschudi, S. Stewart, University of Colorado, Boulder, and W. Meier, J. Stroeve, NSIDC
High-resolution image

Over a winter season, first-year ice can grow up to 1.5 to 2 meters (4.9 to 6.6 feet) thick. Ice that survives the summer season can grow through the next winter by ridging and rafting and additional thermodynamic ice growth to well over 3 meters (9.8 feet) thick. Multiyear ice has a better chance of surviving the following melt season. Multiyear ice moved into the Beaufort Sea from the northwest through the spring and summer as part of the Beaufort Gyre—a clockwise circulation of ice centered over the northern Beaufort Sea (Figure 5a). By contrast, the tongue of ice in the East Siberian Sea largely consisted of first-year ice. Overall, the amount of multiyear ice remaining at the end of summer (Figure 5b) is considerably lower than it used to be during the 1980s and 1990s. Now multiyear ice covers 2 million square kilometers (772,000 square miles) or less of the Arctic Ocean. The oldest ice, which has survived at least four melt seasons, used to cover nearly 1.5 million square kilometers (579,000 square miles). In 2018, this old ice covered only 94,000 square kilometers (36,0000 square miles) at the September minimum.

Antarctica’s wandering path to its seasonal maximum

Figure 6. The graph above shows Antarctic sea ice extent as of October 7, 2018, along with daily ice extent data for four previous years. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, and 2014 in dotted 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 may have reached its maximum extent on October 2, 2018, at 18.15 million square kilometers (7.01 million square miles). If the downward trend continues, it will be the fourth lowest maximum in the satellite record—higher than the 1986, 2002, and 2017 maxima. It is 180,000 square kilometers (70,000 square miles) above the record low Antarctic maximum set in 1986, at 17.97 million square kilometers (6.94 million square miles). It is also 560,000 square kilometers (216,000 square miles) below the 1981 to 2010 average maximum extent of 18.71 million square kilometers (7.22 million square miles). This year’s maximum date of October 2 is about nine days later than the 1981 to 2010 median date and ten days later than the 1981 to 2010 average date. With spring sunshine and warmth increasing daily, the likelihood of a major sea ice expansion is small. However, some years, as in 2002, the maximum was reached on October 12, the latest in the satellite record. There are also brief increases in ice extent as late as October 22 that do not result in new maxima.

In 2018, the Southern Ocean has been true to form. Overall, September sea ice extent has been at near-record lows over the period of satellite observations. A peak in ice extent early in September was followed by a steep decline through mid-month. By the third week of September, extent increased steadily. After a few days of minimal decline, extent reached its maximum on October 2.

Recent ice growth has occurred in the northernmost Ross Sea, partially offsetting ice losses in the area north of Dronning Maud Land and the Drake Passage. Temperatures from August 21 to September 20 at the 925 hPa level were 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) above average over much of the ice edge in the Weddell and western Ross Seas. Cool conditions, with temperatures of 4 to 8 degrees Celsius (7 to 14 degrees Fahrenheit) below average, characterized the northern Bellingshausen Sea. Sea surface temperatures near the ice edge were near average except in the northern Bellingshausen Sea, where they have been 0.5 to 1.5 degrees Celsius (0.9 to 2.7 degrees Fahrenheit) lower than average.

Arctic sea ice extent arrives at its minimum

On September 19 and 23, Arctic sea ice appeared to have reached its seasonal minimum extent for the year, at 4.59 million square kilometers (1.77 million square miles). This ties 2018 with 2008 and 2010 for the sixth lowest minimum extent in the nearly 40-year satellite record. 

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 23, 2018 was 4.59 million square kilometers (1.77 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 map above compares Arctic sea ice extent on September 19, 2018 and September 23, 2018, when Arctic sea ice reached its minimum extent for the year. Sea Ice Index data. About the data Credit: National Snow and Ice Data Center High-resolution image

Figure 1b. The map above compares Arctic sea ice extent on September 19, 2018 and September 23, 2018, when Arctic sea ice reached its minimum extent for the year. Sea Ice Index data. About the data

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

On September 19 and 23, 2018, sea ice extent dropped to 4.59 million square kilometers (1.77 million square miles), tying for the sixth lowest minimum in the satellite record along with 2008 and 2010. This appears to be the lowest extent of the year. In response to the setting sun and falling temperatures, ice extent will begin expanding through autumn and winter. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower.

The minimum extent was reached 5 and 9 days later than the 1981 to 2010 median minimum date of September 14. The interquartile range of minimum dates is September 11 to September 19. This year’s minimum date of September 23 is one of the latest dates to reach the minimum in the satellite record, tying with 1997. The lateness of the minimum appears to be at least partially caused by southerly winds from the East Siberian Sea, which brought warm air into the region and prevented ice from drifting or growing southward.

This year’s minimum extent ranked behind 2015 (fifth lowest), 2011 (fourth lowest), 2007 and 2016 (tied for second lowest), and 2012 (lowest). Moreover, the twelve lowest extents in the satellite era have all occurred in the last twelve years.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent on September 23, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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

This year’s minimum set on September 23 was 1.20 million square kilometers (463,000 square miles) above the record minimum extent in the satellite era, which occurred on September 17, 2012, and 1.63 million square kilometers (629,000 square miles) below the 1981 to 2010 average minimum extent.

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

Table 1. Twelve lowest minimum Arctic sea ice extents (satellite record, 1979 to present)
RANK YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
1 2012 3.39 1.31 Sept. 17
2 2007
2016
4.16
4.17
1.61
1.61
Sept. 18
Sept. 10
4 2011 4.34 1.68 Sept. 11
5 2015 4.43 1.71 Sept. 9
6 2008
2018
2010
4.59
4.59
4.62
1.77
1.77
1.78
Sept. 19
Sept. 19 & 23
Sept. 21
9 2017 4.67 1.80 Sept. 13
10 2014
2013
5.03
5.05
1.94
1.95
Sept. 17
Sept. 13
12 2009 5.12 1.98 Sept. 13

Values within 40,000 square kilometers (15,000 square miles) are considered tied. The 2017 value has changed from 4.64 to 4.67 million square kilometers (1.80 million square miles) when final analysis data updated near-real time data.

Nearing the Arctic’s seasonal minimum

The seasonal minimum of Arctic sea ice extent is imminent; extent at the minimum is likely to be the sixth lowest in the satellite record, tied with 2008.

Overview of conditions

Figure 1. Arctic sea ice extent for September 17, 2018 was 4.60 million square kilometers (1.78 million square miles). The orange line shows the 1981 to 2010 average extent for that day.

Figure 1. Arctic sea ice extent for September 17, 2018 was 4.60 million square kilometers (1.78 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 September 17, Arctic sea ice extent stood at 4.60 million square kilometers (1.78 million square miles). This was 1.69 million square kilometers (653,000 square miles) below the 1981 to 2010 long-term average extent for this day of year, but 1.21 million square kilometers (467,000 square miles) above the record low for this day of year set in 2012. With the onset of autumn, air temperatures are dropping across the Arctic. The seasonal minimum extent is imminent. The Arctic’s minimum sea ice extent is likely to be the 6th lowest in the 39-year satellite record. Cool conditions in July played a large role in slowing the rate of summer ice loss. The Northern Sea Route nevertheless appears to be navigable. The Northwest Passage, including both the Northern and Southern routes, will not open this year. A remnant island of sea ice north of Alaska—well separated from the main area of pack ice and discussed in our previous post—is almost certain to survive the melt season.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 17, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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.

Figure 2a. The graph above shows Arctic sea ice extent as of September 17, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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 plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for September 1 to 16, 2018. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Figure 2b. This plot shows the difference from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for September 1 to 16, 2018. 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

Figure 2c. This plot shows the departure from average sea level pressure in the Arctic, in degrees Celsius, for September 1 to 16, 2018. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division| High-resolution image

Figure 2c. This plot shows the average sea level pressure in the Arctic, in degrees Celsius, for September 1 to 16, 2018. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.

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

The average rate of ice loss from September 1 through September 17 was 25,000 square kilometers per day (10,000 square miles per day), similar to average rate of loss for the first half of September over the period 1981 to 2010. Sea ice retreat primarily occurred in the northern Chukchi, East Siberian, and Laptev Seas. The ice edge retreated slightly in the Kara and Barents Seas. Air temperatures at the 925 hPa level (about 2,500 feet above the surface) were near average over much of the Arctic Ocean, the obvious exception being in the East Siberian Sea, where temperatures were as much as 7 to 9 degrees Celsius (13 to 16 degrees Fahrenheit) above average. These high temperatures helped to reduce the sea ice extent in this region. The sea level pressure pattern for this same period is dominated by an area of low pressure extending from central Siberia, across the pole, and into the Canadian Arctic, and is most pronounced north of the Laptev Sea. The feature north of the Laptev Sea, in conjunction with the area of high pressure centered over the Bering Sea, has acted to transport warm air from the south over the East Siberian Sea, helping to explain the high temperatures there.

No endless summer in the Arctic

With the waning of Arctic summer, the seasonal decrease in sea ice extent has slowed. At this time of the year, the extent is the highest it has been since 2014. Nevertheless, sea ice extent remains well below the interdecile range (lowest 10 percent for ice extent years). The minimum is expected to be one of the ten lowest in the satellite record.

Overview of conditions

Figure 1. Arctic sea ice extent for XXXX 20XX was X.XX million square kilometers (X.XX 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

Figure 1. Arctic sea ice extent for August 2018 was 5.61 million square kilometers (2.17 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 August 2018 averaged 5.61 million square kilometers (2.17 million square miles). This was 1.59 million square kilometers (614,000 square miles) below the 1981 to 2010 long-term average sea ice extent, and 890,000 square kilometers (344,000 square miles) above the record low for the month set in August 2012. August 2018 was the seventh lowest August extent in the satellite record, but the highest August extent since 2014.

At the end of the month, sea ice extent stood at 4.97 million square kilometers (1.92 million square miles). Sea ice extent remained low along the coastal seas of the Arctic Ocean with the exception of the East Siberian Sea. The Northern Sea Route nevertheless appears to be navigable. Low sea ice concentrations persist in the northern Beaufort and Laptev Seas; these areas may still retreat further north before the melt season ends. The Northwest Passage is still choked with ice and is likely to remain so.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September, 4, 2018, along with daily ice extent data for four previous years and 2012, the year with record low minimum extent. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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

This plot shows departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for August 1 to 14, 2018. Yellows and reds indicate higher than average temperature; blues and purples indicate lower than average temperature. Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division High-resolution image

Figure 2b. This plot shows departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for August 2018. Yellows and reds indicate higher than average temperature; blues and purples indicate lower than average temperature.

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

This plot shows average sea level pressure in the Arctic, in millibars, for August 1 to 14, 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure. Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division High-resolution image

Figure 2c. This plot shows average sea level pressure in the Arctic, in millibars, for August 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure.

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

The average ice loss rate for August was 57,500 square kilometers (22,200 square miles) per day. This was slightly faster than the 1981 to 2010 average, but substantially slower than August loss rates in recent years, particularly 2008, 2012, 2015, and 2016.

Air temperatures at the 925 hPa level (about 2,500 feet above sea level) were up to 4 degrees Celsius (7 degrees Fahrenheit) above average over much of the Arctic Ocean and the Laptev Sea, but up to 4 degrees Celsius (7 degrees Fahrenheit) below average over the Canadian Archipelago (Figure 2b). Higher temperatures over the ocean were related to high sea level pressure east of the Laptev Sea and low pressure over the Barents and Kara Seas, funneling in warm air from Eurasia (Figure 2c).

August 2018 compared to previous years

Figure 3. Monthly XXXXX ice extent for 1979 to 201X shows a decline of X.X percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly August ice extent for 1979 to 2018 shows a decline of 10.4 percent per decade.

Credit: National Snow and Ice Data Center
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The linear rate of decline for August sea ice extent is 75,000 square kilometers (29,000 square miles) per year, or 10.4 percent per decade relative to the 1981 to 2010 average. Ice loss during the month was 1.78 million square kilometers (687,000 square miles), which is nearly the same as the 1981 to 2010 average August decrease.

Sea ice off the Alaskan coast

Figure 4. This map of the Arctic Ocean shows sea surface temperatures (SST) from the University of Washington Polar Science Center UpTempO project. The image shows SSTs from the National Oceanic and Atmospheric Administration (NOAA) and sea ice concentrations from the National Snow and Ice Data Center (NSIDC). The numbered circles denote the location of UpTempO buoys, which are measuring the temperature in the near-surface ocean layer. Data from the buoys is available from the UpTempO website.

Credit: University of Washington
High-resolution image

Ice that has persisted along the Alaskan coast is starting to rapidly disintegrate. However, some remnants consist of thick floes. Sea surface temperatures obtained from the University of Washington’s UpTempO website indicate that waters in the area are near the freezing point. As such, some ice in this region may survive the melt season. These temperatures are consistent with those collected during the cruise of the South Korean icebreaker Aaron (see From the field, a wrap up below). Sea surface temperatures ranged between -1 and +1 degrees Celsius (30 and 34 degrees Fahrenheit) when the ship was traveling through the ice, and more than 4 degrees Celsius (39 degrees Fahrenheit) within the open waters of the Chukchi and Bering Seas.

Opening north of Greenland, closed Northwest Passage

Figure 5a. This map shows sea ice conditions in the western part of the Canadian Archipelago. The colors in the color bar correspond to sea ice concentration in tenths. Dark blue is low concentration (less than 10 percent), white is high concentration (100 percent).

Credit: Canadian Ice Service
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Figure 5b. This chart shows total sea ice area for selected years and the 1981 to 2010 average within the northern route of the Northwest Passage. The dotted red line shows 2018 and the other colors show ice conditions in different years.

Credit: Canadian Ice Service
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As noted in our previous post, an unusual area of open water formed off the northern coast of Greenland. It reached a maximum size of about 23,000 square kilometers (about 8,900 square miles) in mid-August—about the size of the state of New Jersey or the country of Wales. The opening has closed somewhat since then, but an ice-free region remains east of Cape Morris Jesup.

In contrast to northern Greenland, substantial amounts of ice remain in the channels of the Canadian Archipelago, thus the Northwest Passage is not open (Figure 5a). As of the end of August, sea ice area in the northern route of the Northwest Passage is currently tracking just above the 1981 to 2010 average (Figure 5b). The region is far from being free of sea ice; high ice concentrations are still present, about half of which is multiyear ice. Below average air temperature over the western Canadian Arctic Archipelago has limited ice melt. Low sea level pressures over the Beaufort Sea and Canadian Basin have packed ice against the western entrance of the Northwest Passage. The southern route of the Northwest Passage also contains relatively high ice concentrations, although mainly first-year ice. In the unlikely event that the southern route does open in the coming weeks it will be short-lived since multi-year ice from the northern regions would quickly move southward to fill the open water gaps.

From the field, a wrap up

Figure 6. Snow depth from August 20 to August 30, 2018 as recorded from two MetOcean snow buoys deployed by NSIDC researcher Julienne Stroeve.

Figure 6a. These graphs show the evolution of snow depth, in meters, from August 20 to August 30, 2018 as recorded by two MetOcean snow buoys, which NSIDC scientist Julienne Stroeve deployed.

Credit: J. Stroeve, NSIDC
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Figure 6b. This photograph shows the MetOcean Snow Buoy set up on Arctic sea ice in the Chukchi Sea.

Figure 6b. This photograph shows the MetOcean Snow Buoy set up on sea ice in the Chukchi Sea.

Credit: J. Stroeve, NSIDC
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Figure 6c. NSIDC researcher Alia Khan collects snow samples for black carbon analysis, snow grain size, and snow depth. These measurements were collected in conjunction with spectral albedo measurements.

Figure 6c. NSIDC scientist Alia Khan collects snow samples for black carbon analysis, and measures snow grain size, snow depth, and spectral albedo.

Credit: A. Khan, NSIDC
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NSIDC scientists Julienne Stroeve and Alia Khan have returned from their Arctic expedition on the South Korean icebreaker Aaron. Both successfully deployed their instruments and collected scientific measurements. Now the work of data analysis begins. Since the buoy deployment by Stroeve and others, two of the melt pond buoy systems have already shown 20 centimeters (7.9 inches) of ice melt. Both snow buoys deployed by Stroeve (Figure 6b) are sending back good data (Figure 6a), with a mean snow depth for the last ten days in August of around 9.5±3.3 centimeters (3.74±1.3 inches for buoy #1 and 8.6±1.8 centimeters (3.4±0.7 inches) for buoy #2. While snow depth at the second buoy remained relatively constant, buoy #1 shows the effect of a snowfall event that likely occurred on August 30. Both buoys have drifted considerably eastwards since deployment, with buoy #1 drifting 104 kilometers (65 miles) in ten days (from 79.0 degrees N, longitude 164.5 degrees W to 79.0 degrees N, longitude 159.6 degrees W), and buoy #2 drifting 132 kilometers (82 miles) in nine days (from 78.4 degrees N, longitude 167.9 degrees W to 78.5 degrees N, longitude 162.0 degrees W).

Khan collected snow and ice samples (Figure 6c) for the analysis of black carbon (BC), which comes from the incomplete combustion of biomass and fossil fuels. When the dark particles are deposited on snow and ice surfaces, they absorb more solar radiation than the surrounding surface, reducing the albedo and enhancing melt. Over the course of the five-day ice camp, her team collected 133 snow samples. The team is interested in exploring local BC signals from shipping traffic, transport and deposition from regional Arctic wildfires, and background concentrations of long-range atmospheric transport of BC. They will compare BC concentrations in snow and sea ice with spectral albedo measurements, as well as results from a global aerosol atmospheric transport model to look at potential source regions of the aerosols.

Antarctic Report

Figure 7. Daily Antarctic sea ice extent for the austral winter season from the past seven years (2012-2018) and the 1981-2010 median, and interquartile and interdecile ranges.

Figure 7. This graph shows daily Antarctic sea ice extent for the austral winter season from the past seven years, 2012 to 2018. 2012 is shown in red, 2013 in a dashed green line, 2014 in solid green, 2015 in yellow, 2016 in magenta, 2017 in purple, and 2018 in orange. 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.

Credit: NSIDC
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Antarctic sea ice has increased at a faster-than-average pace in the later part of August. The sea ice maximum is typically reached in late September. Overall sea ice extent is still in the bottom quartile (the lowest 25 percent of years) of the satellite record (Figure 7). Ice extent is below the median of the past 40 years in several regions, including the northern Weddell, far northeastern Weddell, and southern Indian Ocean.

The past seven austral winter seasons for Antarctic sea ice extent have been remarkably variable. In 2012, 2013, and 2014, Antarctic sea ice extent set consecutive satellite-era record highs for the annual maximum. However, 2015 had a near-average seasonally maximum ice extent, while 2016 saw ice extent plunge in late August to reach unprecedented low levels by austral spring in November. Since 2016, ice has remained below the 1981 to 2010 average extent, setting the second-lowest winter maximum extent in October 2017.

Approaching autumn, pace slows

After declining rapidly through July, sea ice extent decline slowed during the first two weeks of August. A new record September minimum is highly unlikely. Our 2018 projection for the sea ice minimum extent falls between the fourth and ninth lowest in the 39-year satellite record. Two NSIDC scientists are studying ice and ocean conditions in the western Arctic aboard an icebreaker.

Overview of conditions

Figure 1. Arctic sea ice extent for August 15, 2018 was 5.7 million square kilometers (2.2 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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As of August 15, Arctic sea ice extent was 5.7 million square kilometers (2.2 million square miles). This is 1.58 million square kilometers (610,000 square miles) below the 1981 to 2010 average, but 868,000 square kilometers (335,000 square miles) above the record low at this time of year recorded in 2012. Ice retreated recently in the Kara, Laptev, and Beaufort Seas. The ice edge was relatively unchanged near Greenland and Svalbard, and in the East Siberian Sea. Much of the Northwest Passage through Canada remains choked with ice. The Northern Sea Route appears open, according to the Multisensor Analyzed Sea Ice Extent (MASIE) analysis, though ice is lingering near the coast in the East Siberian Sea. Scattered ice floes are likely present along the route. A large patch of sea ice, separated from the main pack, persists in the southern Beaufort Sea. Such patterns of ragged patchiness or large polynyas have been a more frequent feature of Arctic summers since 2006.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of August 15, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 in purple, and 2012 in dotted red. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
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Figure 2b. This plot shows average sea level pressure in the Arctic, in millibars, for July 1 to 15, 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure. Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division High-resolution image

Figure 2b. This plot shows average sea level pressure in the Arctic, in millibars, for August 1 to 14, 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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Figure 2c. This plot shows departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for June 2018. Yellows and reds indicate higher than average temperature; blues and purples indicate lower than average temperature. Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division High-resolution image

Figure 2c. This plot shows departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for August 1 to 14, 2018. Yellows and reds indicate higher than average temperature; blues and purples indicate lower than average temperature.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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This a true-color composite from MODIS on the NASA Terra satellite. August 13, 2018.

Figure 2d. This shows a true color composite image of Cape Morris Jesup off of northern Greenland, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite on August 13, 2018.

Credit: W. Meier, NSIDC/NASA
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Through the first two weeks of August, ice extent declined at approximately 65,000 square kilometers (25,100 square miles) per day, slightly faster than the 1981 to 2010 average of 57,000 square kilometers (22,000 square miles) per day. Sea level pressure was above average over the central Arctic Ocean, a change from last month, flanked by areas of below-average pressure in the Kara Sea and northern Canada (Figure 2b). Temperatures at 925 hPa (about 2,500 feet altitude) were generally 1 to 5 degrees Celsius (2 to 9 degrees Fahrenheit) above average over much of the Arctic Ocean for this period, with the area just north of Greenland reaching 5 to 7 degrees Celsius (9 to 13 degrees Fahrenheit) above average (Figure 2c). Below average air temperatures persisted over the Kara Sea, 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit), and the Beaufort Sea, 1 to 5 degrees Celsius (2 to 9 degrees Fahrenheit). Another feature of note is the region of open water (Figure 2d) along the north coast of Greenland, around Cape Morris Jesup, which is visible on August 13 in Moderate Resolution Imaging Spectroradiometer (MODIS) Terra true color imagery from NASA WorldView. The region normally consists of thick, consolidated ice from a general pattern of on-shore ice motion. Even when winds blow offshore, the strength of the thick ice would hold in place along the coast. However, current ice conditions appear more broken up and likely thinner, and over the past couple of weeks, offshore winds have succeeded in pushing ice off of the coast.

Estimating the September minimum extent

Figure 3. This graph shows potential sea ice minimum extents for 2018 based on ice loss rates from previous years. 2018, through August 15, is shown in blue. Projections based on 2008 rates are shown in purple dots, and 2006 rates are shown in blue dots.

Credit: W. Meier, NSIDC
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A simple way to project the upcoming annual minimum extent involves using the daily rates of change from previous years and applying them to the current sea ice extent. Following the 2005 to 2017 average rate of change between August 15 and the minimum, the extent is projected to drop to an annual low of 4.55 million square kilometers (1.76 million square miles), with a standard deviation range of 4.32 to 4.78 million square kilometers (1.67 to 1.85 million square miles). If sea ice extent continues at the rate of ice loss seen in 2008, the fastest recorded, the minimum at the end of summer would be 4.20 million square kilometers (1.62 million square miles), or the fourth lowest minimum in the satellite record. If sea ice extent continues with the rate for ice loss from 2006, the slowest recorded, the minimum would be 4.90 million square kilometers (1.89 million square miles), or the ninth lowest in the satellite record. It is possible that the rate of change through the remaining summer will be unprecedented in the satellite record (either faster or slower), yielding a final minimum extent outside of this range, but our estimates provide a window of the most likely minimum extent this year. Another possibility is that winds will consolidate the ice and reduce the overall extent. This was a factor contributing to the record low recorded in 2012.

Sea ice up close and personal

Figure 5a. This photograph, off the starboard side of the Araon on 9 August 2018 (21:00 UTC) at 76N/179W, shows dirty ice amidst bright white ice. Photo credit: J. Stroeve

Figure 4a. This photograph, off the starboard side of the RV Araon on August 9, 2018 (21:00 UTC) at 76 degrees N and 179 degrees W, shows dirty ice amidst bright white ice.

Credit: J. Stroeve, NSIDC
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Figure 5b. The team has spotted their first sighting of a polar bear. |Credit: A. Khan ||

Figure 4b. The team’s first sighting of a polar bear.

Credit: A. Khan, NSIDC
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Two NSIDC scientists are currently aboard the Korean icebreaker Araon as it travels through the Chukchi Sea. NSIDC scientist Julienne Stroeve wants to better understand how changes in the sea ice regime (e.g. ice thickness, snow depth, date of melt onset) influence the availability of sunlight under the ice, which plays a key role in phytoplankton blooms and grazing habits of zooplankton. Another objective is to quantify how layering of salty and fresh water in melt ponds evolves over time. To meet these objectives, the researchers will deploy several instrumented to measure seasonal snow accumulation, salinity, and temperature within selected salty and fresh melt ponds. A bio-optical buoy will measure the light and oxygen below the ice, and other buoys will measure the ice growth and melting on different types of ice floes.

As the icebreaker travels through the Arctic Ocean, NSIDC scientist Alia Khan is measuring the amount of sunlight that reaches the ice surface to assess the accuracy of incoming solar energy from weather models. Additionally, she is collecting atmospheric aerosol particles, such as smoke and dust, to measure their size distribution. On the ice, she will collect spectral reflectance measurements (reflectance of the surface in different solar energy wavelengths) of different ice types, such as thin first-year versus thick multiyear ice, snow-covered versus bare ice, and melt ponds. Lastly, she will collect snow and ice samples for analysis of black carbon and algal biomass. Black carbon comes from the incomplete combustion of biomass and fossil fuels. When the dark particles are deposited on snow and ice surfaces, the darker surface absorbs more solar radiation than the surrounding, lighter surface, reducing reflectance of solar energy and enhancing melt. The pigment of ice algae has a similar impact. Collecting these data will help scientists better understand the effects of ship traffic and long-range atmospheric transport that deposit black carbon on the sea ice.

The team left Nome, Alaska, on August 4, and is currently traveling eastwards between 74 and 75 degrees N and 167 degrees W. Before reaching the ice camp where the instruments will be deployed, the ship is retrieving and installing moorings. Ice conditions have been varied since the first sightings of sea ice occurred at 72 degrees 58 minutes N/168 degrees 18.2 minutes W. The first ice sighted mostly consisted of small multiyear ice remnants about 1 meter thick (3.3 feet) and less than 20 meters (66 feet) in size. Now the majority of the ice floes are thin, first-year ice floes between 50 to 200 meters (164 to 656 feet) in size, and 50 to 100 centimeters (1.6 to 3.3 feet) thick. While most of the ice is level ice, some large ridging has been observed. Almost all the ice floes have melt ponds, some discrete and some linked, especially on the thinner first-year ice. Most melt ponds have thaw holes. So far, the majority of melt ponds have a thin top ice layer as air temperatures are hovering around -3 degrees Celsius (27 degrees Fahrenheit). However, once the ship reached 179 degrees W, air temperatures approached 0 degrees Celsius (32 degrees Fahrenheit) and the melt ponds thawed. The most interesting feature thus far has been dirty ice in the midst of bright white ice (see Figure 4a). It is unclear if these dirty ice floes are a result of ice algae, dust, or soot deposits from this summer’s forest fires. The team has also been rewarded with sightings of polar bears (see Figure 4b).

Erratum

Readers alerted us to an error. On August 16, we reported the August 15 sea ice extent as 7.3 million square kilometers (2.82 million square miles) below the 1981 to 2010 average. Instead, it is 1.58 million square kilometers (610,000 square miles) below the 1981 to 2010 average. On August 17, 2018, we corrected the number.

Ice loss speeds up during second half of July

Arctic sea ice extent declined rapidly the latter half of July, despite the persistence of low sea level pressure over the Arctic Ocean and generally cool conditions. At the same time, unusually high sea level pressure persisted over the United Kingdom and Scandinavia, where several new record high temperatures were reached, fostering extensive wildfires.

Overview of conditions

Figure 1. Arctic sea ice extent for July 2018 was 8.22 million square kilometers (3.2 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for July 2018 was 8.22 million square kilometers (3.20 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center
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Arctic sea ice extent for July 2018 averaged 8.22 million square kilometers (3.20 million square miles). This was 1.25 million square kilometers (483,000 square miles) below the 1981 to 2010 long-term average sea ice extent, and 550,000 square kilometers (212,000 square miles) above the record low for the month set in July 2012. July 2018 was the ninth lowest July extent in the satellite record.

Despite finishing ninth lowest in the monthly average, ice loss was rapid during the month. As a result, by July 31 daily extent tracked fourth lowest in the satellite record, just below the extent seen last year at this time, and also just above that seen in 2007, 2011, and 2012. Extent remained unusually low in the Atlantic sector of the Arctic, including the Barents, Kara, Laptev, and East Greenland Seas, whereas the ice edge in the Beaufort and East Siberian Seas remained near average. By the end of July, the ice within Hudson Bay had all melted out and the ice edge in the Chukchi Sea had also retreated far north of its average position for this time of year. This pattern is in stark contrast to last year when by July’s end, the ice edge was located far north of its usual position in the Beaufort and East Siberian Seas while with ice on the Atlantic side, extent was near average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July 31, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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.

Figure 2. The graph above shows Arctic sea ice extent as of July 31, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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
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Total ice loss during July was 3.27 million square kilometers (1.26 million square miles), or a rate of -105,400 square kilometers (-41,000 square miles) per day. This was faster than the 1981 to 2010 long-term average rate of retreat for the month of -86,800 square kilometers (-34,000 square miles) per day. Ice retreat occurred primarily within Hudson Bay and the Kara, Laptev, and Chukchi Seas, and to a lesser extent within Baffin Bay, the East Greenland Sea and the East Siberian coastal regions. In contrast, ice expanded slightly in parts of the Beaufort Sea. While there was little overall change in ice extent in the Beaufort Sea, ice concentration remained low over much of the region, with large areas of open water developing between ice floes. Open water areas between floes readily absorb the sun’s energy and help to enhance lateral (from the side) and basal (from the bottom) melting. However, by the end of July the sun is lower in the sky as compared to June, so this effect is diminishing.

Continuing the pattern of the last two summers, low sea level pressure persisted over the central Arctic Ocean during July, a pattern that historically has tended to slow summer ice loss. Low sea level pressure also persisted over Greenland, paired with high sea level pressure over northern Europe and Siberia to the east, and high sea level pressure over Alaska and Canada to the west. This led to air temperatures at the 925 hPa level (approximately 2,500 feet above the surface) ranging from -0.5 to -4.0 degrees Celsius (-0.9 to -7.0 degrees Fahrenheit) below average over the Kara and Laptev, and from -0.5 to -2.0 degrees Celsius (-0.9 to -4.0 degrees Fahrenheit) over the Beaufort Sea. Near the pole, air temperatures were near average or slightly above average (+0.5 to +1.0 degrees Celsius or +0.9 to +2.0 degrees Fahrenheit). Air temperatures -0.5 to -3 degrees Celsius (-0.9 to +5.0 degrees Fahrenheit) below average also persisted over central and northern Greenland.

Meanwhile, over in Scandinavia several new record high temperatures were observed during the month. In Turku, Finland, temperatures soared to 33.3 degrees Celsius (91.9 degrees Fahrenheit) on July 17, the highest temperature recorded since 1914. In central Norway, the Trondheim airport reported a temperature of 32.4 degrees Celsius (90.3 degrees Fahrenheit) on July 16, the highest on record, while Bardufoss, just south of Tromsø within the Arctic circle, saw a new record of 33.5 degrees Celsius (92.3 degrees Fahrenheit) on July 18. In Sweden, more than forty forest fires raged across the country during the unprecedented heatwave in mid-July. Fires were also burning within Lapland and Latvia. However, it was not only Scandinavia experiencing hot and dry conditions. Western Europe continued to experience prolonged heatwaves. Wildfires in Greece have already killed nearly ninety people, while Japan declared their extreme heatwave as a natural disaster, as more than sixty-five people have died and 22,000 have been treated in hospitals.

July 2018 compared to previous years

Figure 3. Monthly July ice extent for 1979 to 2018 shows a decline of 7.2 percent per decade.

Figure 3. Monthly July ice extent for 1979 to 2018 shows a decline of 7.2 percent per decade.

Credit: National Snow and Ice Data Center
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The linear rate of decline for July sea ice extent is 68,700 square kilometers per year (27,000 square miles per year) or 7.2 percent per decade relative to the 1981 to 2010 average.

Beaufort on the brink?

Figure 4a. This shows a true color composite image of the Beaufort Sea in the Arctic, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite.

Figure 4a. This shows a true color composite image of the Beaufort Sea in the Arctic, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite.

Credit: W. Meier, NSIDC/NASA
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Figure 4b. This image shows sea ice concentration in the Arctic, based on data from the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2).

Figure 4b. This image shows sea ice concentration in the Arctic, based on data from the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2).

Credit: University of Bremen
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Ice concentration over much of the Beaufort Sea has rapidly declined over the past couple of weeks. July 27 imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite showed a large off-shore region with broken-up ice and small ice floes vulnerable to rapid melt by the surrounding ocean (Figure 4a). Sea ice concentration data provided by the University of Bremen from the higher resolution Japan Aerospace Exploration Agency (JAXA) Advance Microwave Scanning Radiometer 2 (AMSR2) showed an expanding open water area within the ice pack between mid-July and August 1 (Figure 4b). By August 1, substantial open water was found throughout the Beaufort. On the other hand, near the coast to the east of Utqiaġvik (formerly Barrow), more compact and likely thicker ice remains, which is less likely to rapidly melt away. How much of the Beaufort ice cover survives the summer and how much more melts away will depend considerably on the weather conditions over the next four to six weeks.

Melt onset a mixed bag

Figure 5. These maps show preliminary melt onset (left) and melt onset anomaly (right) in the Arctic relative to the 1981 to 2010 average. White areas are open ocean or areas with no melt detected.

Figure 5. These maps show preliminary melt onset (left) and melt onset difference from average (right) in the Arctic relative to the 1981 to 2010 average. White areas are open ocean or areas with no melt detected.

Data courtesy Jeffrey Miller, NASA GSFC.
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This summer the ice retreated quite early in the Bering Sea in late April and early May, leading to record low extent in the region. This is partly because the melt started nearly two months earlier than average in certain parts of the Bering Sea, while the regional average melt onset date was 38 days earlier. Melt also began several weeks earlier than average in the Barents Sea, stretching up through the Kara Sea and the southern Laptev Sea. In contrast, melt was later than average in most of the Chukchi and East Siberian Seas as well as parts of the Beaufort Sea. While melt onset generally happens earlier in the southern parts of the Arctic and later as one moves further north, exceptions do occur. For example, already in March some melt onset was detected over the central Arctic Ocean, but it did not continuously melt since that date.

Reconstructing sea ice extent in the Kara and Barents Seas

Figure 6. This graph shows reconstructions of sea ice extent in the Barents and Kara Seas from 1289 to 1993 (red line). The gray line shows the 30-year average, the blue line shows observed sea ice extent, and the green line shows the trend.

Figure 6. This graph shows reconstructions of sea ice extent in the Kara and Barents Seas from 1289 to 1993 (red line). The gray line shows the 30-year average, the blue line shows observed sea ice extent, and the green line shows the trend.

Credit: Qi Zhang (Institute of Polar Meteorology, Chinese Academy of Meteorological Sciences, Bejing, China) and Cunde Xiao (Stake Key Laboratory of Earth Surface and Resources Ecology, Beijing Normal University, Bejing, China)
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While we now have forty years of consistent sea ice observations from satellite, this data record is still relatively short, especially for trying to better understand drivers of current sea ice loss and issues such as potential impacts on mid-latitude weather. A new study from a team of Chinese researchers relied on climate proxies from ice cores and tree ring data from coastal forests to provide estimates of autumn sea ice within the Kara and Barents Seas back to 1289. This new data record suggests that between the 13th and 18th centuries, sea ice extent in the Kara and Barents Seas was more extensive than today and was increasing slightly. This period coincides with the Little Ice Age. After the end of the 18th century, sea ice in this region began to decline and the downward trend became significant during the second half of the 19th century until about the 1930s to 1940s. The sea ice then expanded until the 1970s, after which it has continually declined. Based on this reconstruction, current ice loss in the Kara and Barents Seas is viewed as unprecedented, both in duration and rate of change. While the study is only regional and does not indicate overall Arctic-wide sea ice changes, it provides useful context for the recent decline relative to the long-term variability.

Antarctic sea ice update

Sea ice in the Southern Hemisphere grew at a slightly faster-than-average pace from June through mid-July, but then slowed through the second half of July. At mid-July, ice extent was near average in all sectors except the region north of Dronning Maud Land. In the last two weeks of July, an area of below-average ice extent developed north of Wilkes Land in response to warm winds from the northeast, reducing the overall ice growth and bringing the Southern Hemisphere ice extent down relative to the 1981 to 2010 average (below the range of 90 percent of the past observational years). Above average temperatures at the 925 hPa level (about 2,500 feet above sea level) of 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) occurred over the northern West Antarctic coast and the southern Peninsula, where the Peninsula high pressure ridge brought winds from the north. Temperatures 3 to 6 degrees Celsius (5 to 11 degrees Fahrenheit) above average also occurred along the Wilkes Land coast.

References

Divine, D. V. and C. Dick. 2007. March through August ice edge positions in the Nordic Seas, 1750-2002, Version 1. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: https://doi.org/10.7265/N59884X1.

Zhang, Q., C. Xiao, M. Ding, and T. Dou. 2018. Reconstruction of autumn sea ice extent changes since AD1289 in the Barents-Kara Sea, Arctic. Science China Earth Sciences, doi:10.1007.s11430-017-9196.4.

Smoke on the frozen water

Sea ice declined at a near average rate through the first half of July as low sea level pressure dominated the Arctic Ocean. Wind patterns caused smoke from Siberian forest fires to sweep over the ice.

Overview of conditions

Figure 1. Arctic sea ice extent for July 15, 2018 was 3.3 million square kilometers (3.8 million square miles). The orange line shows the 1981 to 2010 average extent for that day.

Figure 1. Arctic sea ice extent for July 15, 2018 was 8.5 million square kilometers (3.3 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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As of July 15, Arctic sea ice extent was 8.5 million square kilometers (3.3 million square miles). This is 1.24 million square kilometers (479,000 square miles) below the 1981 to 2010 average, but 670,000 square kilometers (259,000 square miles) above the record low for this day in 2011. While total Arctic sea ice extent was tracking at record low levels during winter, the rate of summer ice loss has been unremarkable thus far. Thus far in July, ice retreat has been most pronounced in the Kara Sea, whereas in the Beaufort Sea, the ice edge expanded slightly southwards. The ice edge has changed little within the Barents and East Greenland Seas on the Atlantic side, and retreat has been sluggish in the Chukchi Sea on the Pacific side of the Arctic Ocean.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July 15 , 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2015 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.

Figure 2a. The graph above shows Arctic sea ice extent as of July 15, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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
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Figure 2b. This plot shows average sea level pressure in the Arctic, in millibars, for July 1 to 15, 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure.

Figure 2b. This plot shows average sea level pressure in the Arctic, in millibars, for July 1 to 15, 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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Through the first two weeks of July, ice extent declined at a rate of 134,000 square kilometers (52,000 square miles) per day, which is near the 1981 to 2010 average. The spatial pattern of ice loss has not changed much since the end of June, with minimal ice loss around the entire ice edge. The Beaufort Sea saw some increase in extent due to the transport of ice from the north. Low sea level pressure dominated the central Arctic Ocean and Greenland. Typically, this pattern, associated with counterclockwise (cyclonic) winds is associated with cool conditions and also causes ice divergence, helping to spread the ice cover over a larger area. However, air temperatures over the pole and the East Siberian and Chukchi Seas at the 925 hPa level (approximately 2,500 feet above the surface) ranged 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) above average for the first part of July. Regions with below average air temperatures were found in the Kara, Laptev, and Beaufort Seas (-1 to -3 degrees Celsius or -2 to -5 degrees Fahrenheit below average).

The passive microwave data show a decrease in ice concentration in several areas of the Arctic Ocean, particularly in northern areas of the Beaufort and Chukchi Seas. This is not necessarily a real decrease—it manifests as surface melt and the development of melt ponds on the ice surface. Microwave emission is sensitive to the freeze-thaw state of water. Liquid water atop the ice surface changes the returned signal, mimicking a reduced sea ice concentration. Because the calculation of ice extent does not consider concentration (except for the 15 percent concentration threshold), extent values are much less sensitive to this melt effect. During the melt season, ice extent provides a more consistent and reliable measure of total ice cover.

Siberian smoke over the Arctic Ocean

Figure 3. These images from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor show the Arctic Ocean and surrounding land from July 3 to 6, 2018. Blue arrows indicate smoke that had drifted from fires in Siberia. ||Credit: NASA| High-resolution image

Figure 3. These images from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor show the Arctic Ocean and surrounding land from July 3 to 6, 2018. Blue arrows indicate smoke that had drifted from fires in Siberia.

Credit: NASA
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Fires in the western United States have been much in the news lately. Less noted are significant fires in Siberia. Over several days at the beginning of July, smoke from these fires was brought into the Arctic Ocean by winds associated with the pattern of low pressure in the region. The smoke streamed over the East Siberian, Chukchi, and Beaufort Seas and eventually across Alaska into northern Canada.

The smoke has two potential effects on sea ice. First, as it drifts over the ice, the smoke particles scatter solar radiation and reduce how much is received at the surface. This has a cooling effect that will tend to reduce the rate of ice loss. However, smoke particles that settle onto the ice will darken the surface, thus decreasing the reflectivity of the surface, or albedo. This increases the amount of solar energy absorbed by the ice and enhances melt. The atmospheric scattering effect of the smoke is short term and dissipates after the smoke drifts away. The surface albedo effect has a longer-term impact and could serve to enhance melt rates through the summer. The magnitude of the effect will depend on how many smoke particles are deposited on the surface, the albedo of the surface that the particles fall on, and the amount of cloud cover which reduces the incoming sunlight. The biggest effect would be on bright, snow-covered ice. It would be smaller on darker melting ice and melt ponds, and there would be no effect in open water areas.

 

 

 

A sluggish June

Arctic sea ice extent declined at a slightly slower-than average pace in June. Despite the slow loss, warm conditions and winds from the south developed a large area of open water in the Laptev Sea.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2018 was 12.2 million square kilometers (4.7 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

Figure 1. Arctic sea ice extent for June 2018 was 10.7 million square kilometers (4.1 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 2018 averaged 10.7 million square kilometers (4.1 million square miles). This was 1.05 million square kilometers (405,000 square miles) below the 1981 to 2010 average and 360,000 square kilometers (139,000 square miles) above the record low June extent set in 2016. This was the fourth lowest June average extent in the satellite record.

Extent at the end of June remained below average in the Chukchi Sea, but because of slow retreat through June in the region, extent in the Chukchi is now closer to average than was the case at the end of May. The Barents Sea and East Siberian Sea also have extents well below average at the end of June. Most of the ice in the Sea of Okhotsk has melted. Ice has been retreating in the west side of Hudson Bay where extent is below average. However, this is countered by above average extent in the eastern side of the bay. Notably, a large area of open water has developed in the Laptev Sea, leading to record low extents in that region during the first half of June.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July, 4, 2018, along with daily ice extent data for four previous years and 2012, the year with record low minimum extent. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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 3

Figure 3a. This plot shows the average sea level pressure in the Arctic at the 925 hPa level, in millibars, for June 2018. Yellows and reds indicate higher than average air pressure; blues and purples indicate lower than average air pressure.

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

Figure 3b

Figure 3b. This plot shows departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for June 2018. Yellows and reds indicate higher than average temperature; blues and purples indicate lower than average temperature.

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

The salient features of the atmospheric pattern for June include a region of low sea level pressure centered over the northern Barents Sea, and a high pressure cell centered over the Laptev Sea. A ridge of high pressure also extends eastward into northern Canada (Figure 3a). Winds from the south between the low pressure area in the Barents Sea and the high pressure area in the Laptev Sea gave rise to a pronounced region of above-average temperatures centered over Central Siberia and extending over the Laptev and East Siberian Seas (Figure 3b). However, elsewhere over the Arctic Ocean, temperatures were near average or slightly below average.

The temperature pattern is consistent with the early development of open water in the Laptev Sea. Extents in this area oscillated between slightly above and below the record low extent set in June 2014. Parts of the Laptev Sea opened as early as mid-April, likely due to winds transporting ice away from the fast ice zone (ice that is locked to the shoreline). While new ice formed in these open water areas, this ice was thin and prone to melting out once the summer melt season started.

Also of note was the passage of a strong cyclone in early June. This system moved into the Kara Sea on June 6, and reached a minimum central pressure of less than 970 hPa on June 7. By June 10, it had migrated into the Beaufort Sea. It dissipated on June 13.

June 2018 compared to previous years

Figure 4. Monthly May ice extent for 1979 to 2018 shows a decline of 2.6 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 4. Monthly June ice extent for 1979 to 2018 shows a decline of 4.1 percent per decade.

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

The linear rate of decline for June sea ice extent is 48,000 square kilometers (18,500 square miles) per year, or 4.1 percent per decade relative to the 1981 to 2010 average. Ice loss during the month was 1.6 million square kilometers (618,000 square miles), somewhat slower than the 1981 to 2010 average loss of 1.7 million square kilometers (656,000 square miles) for the month. Clearly the early ice losses in the Laptev Sea, associated with warm conditions over the region, could not make up for slower retreats elsewhere.

New insights into warming in the northern Barents Sea

An interesting feature of recent years is a region of unusually high winter air temperatures, or a winter hotspot, over the northern Barents Sea. Previous studies have provided evidence linking the hotspot to a halocline retreat, which is a retreat or weakening of the cold, fresh waters at the ocean surface that prevent ocean heat imported from the Atlantic from mixing upwards. A new paper by Lind et al. (2018) argues that the hotspot is driven by the lack of sea ice transport. Sea ice is mostly fresh water (low salinity) and less is being transported into that region. Hence the ocean surface becomes less fresh over the northern Barents Sea, allowing the warm Atlantic water to mix upwards.

Antarctica in June

Figure 5

Figure 5. This plot shows departure from average air temperature in Antarctica at the 925 hPa level, in degrees Celsius, for June 2018. Yellows and reds indicate higher than average temperature; blues and purples indicate lower than average temperature.

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

Sea ice expanded at a faster-than-average pace in June in the Southern Hemisphere, bringing Antarctic sea ice extent closer to typical ice extents for this time of year. This follows on the heels of a period of below-average ice extent since austral winter in 2016. Sea ice extent is near average in all sectors except the northeastern Weddell Sea, and a small area in the northern Davis Sea. Higher-than-average air temperatures prevailed in these regions, and cool conditions prevailed over the northern Ross Sea.

Antarctica’s sea ice and ice shelf disintegration

A new study in the Journal Nature found that reduced sea ice in the northwestern Weddell Sea and southern Bellingshausen Sea likely contributed to the weakening of major ice shelves prior to their disintegration in the 1990s and early 2000s. Loss of the sea ice buffer near Antarctica’s coast allows long-period ocean swell to flex ice shelves. Under ordinary conditions, this flexing has little effect. However, if the ice shelves have been pre-conditioned by seasonal melt-water flooding, the flexing by wave action in late summer can have a devastating effect. Minor flexure of the ice shelf plate allows water to infiltrate existing cracks and initiate fracturing of the ice.

Four major ice shelf break-up events in 1995 (Larsen A), 2002 (Larsen B), and 2008 and 2009 (Wilkins) all occurred after multiple weeks where no sea ice was present near the ice shelf fronts to dampen ocean swell. In the case of the Larsen A and B events, the loss of the ice shelves initiated a significant acceleration of the tributary glaciers. The study demonstrates that sea ice—a component of the cryosphere that is very sensitive to changing climate and ocean—has an important protective effect on the Antarctic ice sheet.

Further Reading

Lind, S., R. B. Ingvaldsen, and T. Furevik. 2018. Arctic warming hotspot in the Northern Barents Sea linked to declining sea-ice import. Nature Climate Changedoi:10.1038/s41558-018-0205-y.

Massom, R., T. A. Scambos, L. G. Benetts, P. Reid, V. A. Squire, and S. Stammerjohn. 2018. Antarctic ice shelf disintegration triggered by sea ice loss and ocean swell. Nature, 558, 383-389, doi:10.1038/s41586-018-0212-1.

DMSP F18 to undergo testing late June, early July

The Defense Meteorological Satellite Program (DMSP) F18 satellite will be undergoing testing from June 25 to 29 and from July 9 to 12. During this time, data from the Special Sensor Microwave Imager/Sounder (SSMIS) sensor on F18 may have degraded quality or may not be collected. DMSP F18 is the primary sensor that provides NSIDC with near-real-time data for sea ice monitoring (nsidc-0081, the Sea Ice Index, and the Arctic Sea Ice News and Analysis web page). If the data quality does not meet operational standards, NSIDC will remove the resulting sea ice fields or NSIDC may not distribute data from the F18 SSMIS during the test periods.

Springtime for the Arctic

Arctic sea ice extent for May 2018 was the second lowest in the satellite record. Above average temperatures and high sea level pressure prevailed over most of the Arctic Ocean, while some surrounding continental regions were colder than usual.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2018 was 12.2 million square kilometers (4.7 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for May 2018 was 12.2 million square kilometers (4.7 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 2018 was 12.2 million square kilometers (4.7 million square miles). This was the second lowest May extent in the 39-year satellite record, and is 310,000 square kilometers (120,000 square miles) above May 2016, the record low for the month. Compared to May 2016, the ice cover remained slightly more extensive in the Barents and Kara Seas, within Baffin Bay, Davis Strait, and the southern Beaufort Sea, but less extensive in the Chukchi and East Greenland Seas.

In Svalbard, the average temperature for May 2018 was 6 degrees Celsius (11 degrees Fahrenheit) above average. By the end of the month, the north and west coasts of Svalbard were largely ice-free and a tongue of open water east of the islands extended northeast to Franz Joseph Land. According to NSIDC data, open water stretched as far north as ~82 degrees N at the end of May.

In the Chukchi Sea, open water developed to the west of Point Barrow, Alaska throughout the month. This may be in part a result of the inflow of warm waters from the Pacific, where sea surface temperatures were higher than average. It may also be due to the general lack of sea ice in the region that allows the ocean to readily absorb the sun’s energy. Ice retreat was also substantial within the Sea of Okhotsk, and little ice remains in the region. Hudson Bay began to open up, with a significant area of open water in the northwest sector of the bay.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of June 3, 2018, along with daily ice extent data for four previous years and the record low year. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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.

Figure 2a. The graph above shows Arctic sea ice extent as of June 3, 2018, along with daily ice extent data for four previous years and 2012, the year with record low minimum extent. 2018 is shown in blue, 2017 in green, 2016 in orange, 2015 in brown, 2014 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 plot shows departure from average sea level pressure in the Arctic, in millibars, for May 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure. ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division

Figure 2b. This plot shows departure from average sea level pressure in the Arctic, in millibars, for May 2018. Yellows and reds indicate higher than average sea level pressure; blues and purples indicate lower than average sea level pressure.

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

Figure 2c. This plot shows air temperatures at the 925 mb level averaged over the Arctic Ocean region. This region covers only oceans areas in the Arctic, bounded by the Bering Strait on the Pacific side, and Fram Strait and roughly the 20 degree E meridian between Svalbard and Norway.||Credit: A. P. Barrett, NSIDC

Figure 2c. This plot shows air temperatures at the 925 mb level averaged over the Arctic Ocean region. This region covers only ocean areas in the Arctic, bounded by the Bering Strait on the Pacific side, and Fram Strait and roughly the 20 degree E meridian between Svalbard and Norway.

Credit: A. P. Barrett, NSIDC
High-resolution image

The atmospheric pattern (Figure 2b) for May was characterized by a region of above average sea level pressure centered over the Fenno-Scandinavian Peninsula and below average pressure centered over Greenland. This pattern helped to funnel warm winds from the south into the Barents Sea sector favoring retreat of ice. Air temperatures at the 925 hPa level (about 2,500 feet above sea level) in the Barents Sea were up to 5 degrees Celsius (9 degrees Fahrenheit) above average (not shown). On the Pacific side, departures from average sea level pressure were small and a fairly typical Beaufort Sea High and Aleutian Low pattern reigned for much of the month. Overall it was warm across the Arctic Ocean with temperatures at the 925 hPa level ranging between 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) above average for the month. By contrast, conditions over land regions surrounding the Arctic were relatively cool. Parts of Central Siberia and Nunavut in northern Quebec saw temperatures more than 5 degrees Celsius (9 degrees Fahrenheit) below average. However, Europe, eastern Asia and western North America were warmer than usual.

Air temperatures at the 925 mb level (about 2,500 feet above sea level) over the Arctic Ocean have been above average through most this year (Figure 2c). Temperatures were extremely high compared to typical conditions from January through early March. After a brief cold period in March, temperatures returned to near average and increased at typical rates through most of May.

While it is still relatively early in the melt season, images from the Moderate Resolution Imaging Spectroradiometer (MODIS) show considerable fracturing of multiyear ice floes in the Beaufort Sea. The early development of open water around these large ice floes can help accelerate melt through absorption of solar energy. Some of these ice floes appear already partially covered by melt ponds.

May 2018 compared to previous years

Figure 3. Monthly May ice extent for 1979 to 2018 shows a decline of 2.6 percent per decade.

Figure 3. Monthly May ice extent for 1979 to 2018 shows a decline of 2.6 percent per decade.

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

The linear rate of decline for May sea ice extent is 36,000 square kilometers (14,000 square miles) per year, or 2.6 percent per decade relative to the 1981 to 2010 average. Ice loss during the month was 1.7 million square kilometers (656,000 square miles), which was faster than the 1981 to 2010 average loss of 1.5 million square kilometers (579,000 square miles) for the month.

Another season for the Sea Ice Outlook

The Sea Ice Prediction Network is once again soliciting contributions to the Sea Ice Outlook predicting the September 2018 sea ice extent. This effort is coordinated by the Arctic Research Consortium of the United States (ARCUS). This is the second phase of the Sea Ice Prediction Network, and is currently funded by the National Science Foundation, the Office of Naval Research, and the United Kingdom’s National Environment Research Council. While all prediction methods are welcome, a new focus of the project is to assess the economic value of seasonal ice forecasts. To make the forecasts more useful to stakeholders, there is an increased emphasis on predicting the spatial pattern of the ice cover for September, not just the total extent. The Sea Ice Outlook will summarize contributions and assess the seasonal evolution of conditions each month through summer and in post-season reports at https://www.arcus.org/sipn.

Autumn in Antarctica

Figure 4a. Arctic sea ice extent for June 1, 2018 was 11.0 million square kilometers (4.2 million square miles). The orange line shows the 1981 to 2010 average extent for that day.

Figure 4a. Arctic sea ice extent for June 1, 2018 was 11.0 million square kilometers (4.2 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

Sea ice extent in the Southern Ocean grew steadily in May at the rate of 123,000 square kilometers (47,000 square miles) per day, somewhat faster than the 1981 to 2010 average growth rate of 108,000 square kilometers (42,000 square miles) per day. This pushed Antarctic ice extent from third lowest at the start of the month to sixth lowest by June 1. Ice extent was near average for all regions except for a broad section of the far eastern Weddell Sea, where ice extent was less than the 1981 to 2010 average. The eastern Ross, Amundsen, and Bellingshausen Seas began the month with less ice cover than average, but rapid growth in these regions brought ice extent to near average by the end of the month.

Reference

Nilsen, T. “Warmest May ever on Arctic Islands,” The Barents Observer, June 3, 2018, 11:00 a.m., MST, https://thebarentsobserver.com/en/ecology/2018/06/warmest-may-ever-arctic-islands.