Sloshing Around in the Polar Twilight

The end of the Arctic sea ice melt season is nigh. The last couple of weeks have seen small rises and falls in ice extent, primarily due to changes in wind patterns. However, falling temperatures will soon accelerate the pace of ice growth.

Overview of conditions

Figure 1. Arctic sea ice extent for XXXX XX, 20XX was X.XX million square kilometers (X.XX 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 16, 2019, was 4.21 million square kilometers (1.62 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

Arctic sea ice extent was 4.21 million square kilometers (1.62 million square miles) on September 16, which is likely near the seasonal minimum extent that is expected within the next week. The last two weeks have seen periods of declining extent along with periods of little change or even gains in extent. From August 30 through September 5, there was a total loss of about 320,000 square kilometers (123,600 square miles). The ice cover then experienced an increase in extent from September 7 through 10. From September 10 through 16, the decline resumed, dropping 118,000 square kilometers (45,600 square miles).

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of XXXXX XX, 20XX, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 in brown, 20XX in purple, and 20XX 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 2a. The graph above shows Arctic sea ice extent as of September 16, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. Sea Ice Index data.

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

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars (hPa) for September 5 to 10, 2019. 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

Figure 2b. This plot shows average sea level pressure in the Arctic in millibars (hPa) for September 5 to 10, 2019. 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

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars (hPa) for September 10 to 14, 2019. 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

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars (hPa) for September 10 to 14, 2019. 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

Rises and falls in extent are not unusual when nearing the sea ice minimum; the sea ice edge is in near-equilibrium with ocean and atmospheric temperatures. However, variable winds can either push the edge outward to increase ice extent or compact areas of lower-concentration ice to decrease ice extent. From August 26 to August 30, the overall change in extent was near zero; surface winds as depicted in the NCEP Reanalysis during this period pushed ice southward in Beaufort, Chukchi, and East Siberian Seas sectors, while winds from the south led to declines in extent in the East Greenland and Barents Seas.

From August 30 through September 5, strong winds from the south in the Beaufort, Chukchi, and East Siberian Seas pushed the ice edge northward. Essentially, the expansion at the end of August was reversed. Ice loss in the East Greenland Sea and the Canadian Archipelago also contributed to the overall extent decline during this period.

Conditions changed once again from September 5 through September 10. Extent declined only slightly until September 7 and then increased. Again, variable winds played a leading role. Winds from the north persisted on the Pacific side of the Arctic Ocean, but strong winds from the west in the Barents, Kara, and East Greenland Seas, as indicated by strong low pressure centered near the North Pole (Figure 2b), led to an increase in extent there. The Canadian Archipelago region also gained ice, reflecting low temperatures and the onset of freeze-up.

After September 10, the decline in ice extent resumed, with losses particularly north of Svalbard and between Svalbard and Franz Josef Land. This was related to northward winds as a low pressure center moved south to the east of Greenland. To a lesser degree, the ice also retreated northward on the Pacific side, also related to northward winds in the Chukchi and East Siberian Sea sectors. Southward winds prevailed in the Beaufort Sea, but these did not extend the ice edge southward, possibly because of warm waters that melted ice. Ice growth continued in the Canadian Archipelago.

Sea ice hanging on in the Beaufort Sea

Figure 3. This shows a true-color composite image of a tongue of ice that has persisted in the eastern Beaufort Sea. This tongue mostly consists of thin, small floes of ice close to melting completely, interspersed by thicker, large floes and (likely) multi-year ice. Image taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite on September 9, 2019. ||Credit: Land Atmosphere Near-Real Time Capability for EOS (LANCE) System, NASA/GSFC. |High-resolution image

Figure 3. This shows a true-color composite image of a tongue of ice that has persisted in the eastern Beaufort Sea. This tongue mostly consists of thin, small floes of ice close to melting completely, interspersed by thicker, large floes and (likely) multi-year ice. Image taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite on September 9, 2019.

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

While most of the ice in the Beaufort Sea has melted out well beyond the Alaskan and Canadian coasts, a tongue of ice has persisted in the eastern Beaufort, just off the western coast of Banks Island. MODIS imagery from NASA Worldview shows that this tongue mostly consists of thin, small floes of ice close to melting completely, interspersed by thicker, large floes and (likely) multi-year ice. Most of this ice will likely survive the melt season.

 

Shipping passages and the MOSAiC expedition

The southern (Amundsen) route of the Northwest Passage appears to be open, but only via the narrow Bellot Strait between Somerset Island and the Boothia Peninsula; the wider passage through Peel Sound on the west side of Somerset Island still has ice in the mouth of the sound. The Northern Sea Route is open with the largest constriction just east of Severnaya Zemlya.

The German icebreaker Polarstern will leave port from Tromso, Norway, on September 20 and head north into the ice. It will be frozen into Arctic sea ice for the next year as part of the MOSAiC expedition, and scientists aboard will conduct numerous experiments—collecting data on ocean, ice, and atmospheric conditions. The U.S. lead scientist for the project, Matthew Shupe, is at the Cooperative Institute for Research in Environmental Sciences (CIRES), of which NSIDC is a part. NSIDC senior research scientist Julienne Stroeve will be on the ship for several weeks this coming winter. Readers can expect much more information on MOSAiC from CIRES in the coming months.

Summer’s not over until bottom melt ends

While Arctic sea ice extent was tracking at record low levels in July and August, the pace of ice loss slowed considerably after the middle of August, despite above-average air temperatures over much of the Arctic Ocean. By August 14, extent started tracking above levels observed in 2012, resulting in the second lowest August extent in the satellite record. Although Arctic air temperatures are now falling below freezing, sea ice loss will likely continue for several weeks as heat stored in the ocean melts the underside of sea ice. Winds can also compress the pack further reducing sea ice extent. As of this post, the rate of sea ice loss has sped up again.

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 2019 was 5.03 million square kilometers (1.94 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

On August 14, Arctic sea ice extent began tracking above 2012 levels, and continued to do so for the remainder of the month, resulting in a monthly average extent of 5.03 million square kilometers (1.94 million square miles). This is 310,000 square kilometers (120,000 square miles) above the 2012 average extent, the lowest in the satellite record, and 2.17 million square kilometers (838,000 square miles) below the 1981 to 2010 average for August. On August 13, ice extent dropped below 5 million square kilometers (1.9 million square miles). This never occurred prior to 2007, but has occurred every subsequent year apart from 2009 and 2013. Overall sea ice retreat during the second half of August was modest, taking place along the periphery of the ice edge within the Arctic Ocean. Sea ice concentrations remain low over many areas, especially along the ice edge in the Beaufort Sea and within the Laptev Sea.

For the month as a whole, sea ice loss was most pronounced in the East Siberian Sea as the ice that had persisted in that region finally melted out. The ice edge is presently far north of its climatological average position everywhere except for a tongue of ice in the eastern part of the Beaufort Sea west of Banks Island, and around the island of Svalbard, where the ice edge remains near or slightly south of its average location for this time of year. While sea ice concentrations from the passive microwave record suggest that the Northwest Passage southerly route, or Amundsen’s route, is free of ice, operational ice analyses, which employ higher resolution visible band and radar satellite data, show some remaining ice around the Prince of Wales Island. The more northerly route through the Parry Channel and M’Clure Strait still has significant amounts of ice and will likely not open this year.

On August 31, sea ice extent dropped to 4.62 million square kilometers (1.78 million square miles), the third lowest extent for this date in the satellite record.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of XXXXX XX, 20XX, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 in brown, 20XX in purple, and 20XX 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 2a. The graph above shows Arctic sea ice extent as of September 4, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. Sea Ice Index data.

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

Figure 2X. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for XXXmonthXX 20XX. 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 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, 2019. 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

During the second half of August, air temperatures at the 925 hPa level (about 2,500 feet above the surface) were above average over most of the Arctic Ocean. Temperatures over the East Siberian through the Laptev and Kara Seas were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) above the 1981 to 2010 average. Air temperatures over the Canadian Arctic Archipelago were up to 3 degrees Celsius (5 degrees Fahrenheit) above average. By contrast, air temperatures around Svalbard were around 1 degree Celsius (2 degrees Fahrenheit) below average (Figure 2b). Cold conditions were also present in the southern Beaufort Sea and in the Yukon and MacKenzie districts of Canada’s Northwest Territories.

During the third week of August, a cyclone developed over the Northwest Territories and entered the Beaufort Sea on August 23. It then moved east over the Canadian Arctic Archipelago. This cyclone began pulling warm air from the south over northwestern Greenland and the Canadian Arctic Archipelago and into the Lincoln Sea. While this cyclone was short-lived, air temperatures during the cyclone passage within the Lincoln Sea were up to 10 degrees Celsius (18 degrees Fahrenheit) above the 1981 to 2010 average. While a notable event, the storm does not appear to have had much of an effect on ice extent.

August 2019 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 2019 shows a decline of 10.59 percent per decade.

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

Overall, the pace of ice loss in August 2019 was 54,900 square kilometers (21,200 square miles) per day. This was considerably slower than the 2012 rate of decline of 89,500 square kilometers (34,600 square miles) per day, but only slightly slower than the 1981 to 2010 climatological rate of decline of 57,300 square kilometers (22,100 square miles) per day. In total, 1.70 million square kilometers (656,000 square miles) of ice were lost during August 2019. The linear rate of sea ice decline for August from 1979 to 2019 is 76,200 square kilometers (29,400 square miles) per year, or 10.59 percent per decade relative to the 1981 to 2010 average.

The melt season is not over until bottom melt ends

Time series from the Beaufort Sea in 2005 – 2006 of ice thickness (red line), growth rate (blue bars with negative values), bottom melt (blue bars with positive values), and surface melt (dark blue line with points). Both surface and bottom melt started on 10 June. Surface melt peaked on 1 August and peak bottom melt was two weeks later on 15 August. Surface melting ended on 24 August, while bottom melting continued until 24 October. Image from Don Perovich.

Figure 4a. This 2005 to 2006 time series from the Beaufort Sea shows ice thickness (red line), growth rate (blue bars with negative values), bottom melt (blue bars with positive values), and surface melt (dark blue line with points). Both surface and bottom melt started on June 10. Surface melt peaked on August 1, and peak bottom melt was two weeks later on August 15. Surface melting ended on August 24, while bottom melting continued until October 24.

Credit: Don Perovich
High-resolution image

Figure 4b. Sea surface temperature (from NOAA dOISST) and ice concentration (NSIDC Sea Ice Index) for 25 August 2019. The locations of 3 UpTempO drifting buoys are marked as 1, 2 and 7. Data from UptempO drifting buoy locations is available for downloading here.

Figure 4b. This map shows sea surface temperature and ice concentration for August 25, 2019. The locations of three Upper layer Temperature of the Polar Oceans (UpTempO) drifting buoys are marked as 1, 2, and 7. Sea surface temperature data are from the National Oceanic and Atmospheric Administration daily Optimum Interpolation Sea Surface Temperature (OISST), and ice concentration from the NSIDC Sea Ice Index. Download data from UptempO drifting buoy locations.

Credit: University of Washington
High-resolution image

By August, the sun hangs low on the horizon in the Arctic, air temperatures drop below the freezing, melt ponds begin to freeze, and the first snows fall. It seems as though summer is over, but it is not. Even though surface melting has largely ended, there still is ample heat remaining in the ocean and the bottom of the ice is still melting. Colleague Don Perovich discussed these issues at the International Glaciological Society: Sea Ice at the Interface meeting, held August 18 to 23, 2019 in Winnipeg, Canada. Surface melting peaks in July and usually ends in mid-August. By contrast, bottom melting peaks in August and often continues into September or October (Figure 4a). This is supported by observations in regions with early sea ice retreat like the Chukchi, Bering, Laptev, and Kara Seas, where sea surface temperatures were 5 degrees Celsius (41 degrees Fahrenheit) or higher on August 25 (Figure 4b).

Update on ice conditions in the Northwest Passage

Figure 5a. The time series shows total sea ice area for 2019, 2011 and the 1981-2010 median within the northern route of the Northwest Passage. Data is from the Canadian Ice Service.

Figure 5a. This time series shows total sea ice area for 2019, 2011, and the 1981 to 2010 median within the northern route of the Northwest Passage.

Credit: Canadian Ice Service
High-resolution image

Figure 5b. The time series shows total sea ice area for 2019, 2011 and the 1981-2010 median within the southern route of the Northwest Passage. Data is from the Canadian Ice Service.

Figure 5b. The time series shows total sea ice area for 2019, 2011, and the 1981 to2010 median within the southern route of the Northwest Passage.

Credit: Canadian Ice Service
High-resolution image

As of August 26, sea ice area in the northern (deep water) route of the Northwest Passage is currently tracking just below the 1981 to 2010 average (Figure 5a). Concentrations are well above the record low for this area recorded in 2011, with 83 percent of the ice cover consisting of multiyear ice. It is unlikely the northern route will open this year. By sharp contrast, the southern route of the Northwest Passage, Amundsen’s route, is tracking well below the 1981 to 2010 average and just above 2011 (Figure 5b). Areas of low ice concentration are still present to the east and south of Prince of Wales Island but it is likely the southern route will completely clear in the coming weeks. The Northern Sea Route along the Siberian coast has been essentially open for several weeks.

Another year of sea ice loss in the Beaufort Sea

Figure 6a. MODIS Imagery over the Beaufort Sea from April 4 and May 30, 2019. Showing the transition from an ice-covered Sea to the vast areas of open water that were dynamically created. ||Credit: NASA Worldview|High-resolution image

Figure 6a. This NASA Worldview image taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite shows the Beaufort Sea on April 4 and May 30, 2019. The two images show a transition in sea ice extent where the April 4 image depicts an ice-covered sea while the May 30 image contains large areas of open water.

Credit: NASA Worldview
High-resolution image

Figure 6b. Mean fields of ice drift and sea level pressure in the Arctic from April 1 to May 31, 2019. Ice Drift data is from OSI SAF Low Resolution Sea Ice Drift product (http://osisaf.met.no/p/ice/index.html#lrdrift) and SLP fields are from NCEP reanalysis.

Figure 6b. This map of the Arctic shows average fields of ice drift and sea level pressure (SLP) from April 1 to May 31, 2019. Ice Drift data is from Ocean and Sea Ice (OSI) Satellite Application Facilities (SAF) Low Resolution Sea Ice Drift product and SLP fields are from National Centers for Environmental Prediction (NCEP) reanalysis.

Credit: Meteorologisk Institutt and NCEP
High-resolution image

Sea ice loss during 2019 has been particularly pronounced in the Beaufort Sea, where only a dispersed tongue of multiyear sea ice remains. On August 31, sea ice extent fell to its sixth lowest in the 40-year satellite record and continues the long-term trend towards the Beaufort becoming seasonally ice free, meaning that no ice survives the melt season. Recent work by David Babb and colleagues at the University of Manitoba has focused on the dynamic and thermodynamic processes influencing summer sea ice loss in the Beaufort Sea, and connected summer ice loss back to the timing of sea ice breakup.

In early April 2019, a consolidated mix of first year and multiyear sea ice covered the Beaufort Sea (Figure 6a). However, high sea level pressure over the western Arctic during April and May increased ice export out of the Beaufort Sea (Figure 6b), dynamically opening up the region and dropping its sea ice area by 50 percent in May. (Sea ice area represents the area of a grid cell multiplied by the ice concentration.) The transition from a snow-covered icescape to vast areas of open water occurred between one to two months earlier than usual, initiating a cycle of increased open water—increased solar energy absorption—and therefore accelerated ice melt (ice-albedo feedback). Subsequently, regional sea ice area in June fell to one of its lowest values in the satellite record, indicating that the Beaufort was bound to once again become ice free in September like it had in 2012 and 2016. However, ice import during June and July generated a tongue of multiyear ice in the eastern Beaufort Sea that led to positive thickness anomalies in July and persisted through summer. Low sea ice once again characterizes the Beaufort Sea, where nine of the ten lowest sea ice areas occurred within the last 13 years. Sea ice extent has a significant negative trend in this region, losing 5,006 square kilometers (1,933 square miles) per year at the end of August. While it will be interesting to see if this multiyear ice tongue persists through September, it will also be instructive to see how the warm surface waters affect fall freeze up, which may then impact the 2019 to 2020 ice growth season.

Antarctic sea ice note

Sea ice surrounding Antarctica has grown at a faster-than-average pace since late July, climbing from a record low level on July 25 to about tenth lowest at the end of August. Most of the increase in extent was along the sea ice edge of the Weddell and Cosmonaut Seas, and north of Wilkes Land, while the northern Ross Sea and Amundsen Sea saw significant ice retreat. The annual sea ice maximum for Antarctic sea ice is usually around October 1.

Further reading

Babb, D. G., J. C. Landy, D. G. Barber, and R. J. Galley. 2019. Winter sea ice export from the Beaufort Sea as a preconditioning mechanism for enhanced summer melt: A case study of 2016. Journal of Geophysical Research: Oceans, 124, doi:10.1029/2019JC015053.

Galley, R. J., D. Babb, M. Ogi, B. G. T. Else, N.-X. Geilfus, O. Crabeck, D. G. Barber, and S. Rysgaard. 2016. Replacement of multiyear sea ice and changes in the open water season duration in the Beaufort Sea since 2004, Journal of Geophysical Research: Oceans, 121, doi:10.1002/2015JC011583.

 

Dead heat

At mid-month, Arctic sea ice extent is tracking close to 2012, the year with the lowest minimum in the satellite record. Sea ice volume is also tracking at low levels. Smoke from Siberian wildfires continues to cover much of the Pacific side of the Arctic Ocean, but as solar input declines this late in the melt season, it is unlikely to impact sea ice loss.

Overview of conditions

Figure 1a. Arctic sea ice extent for XXXX XX, 20XX was X.XX million square kilometers (X.XX 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 1a. Arctic sea ice extent for August 14, 2019 was 5.04 million square kilometers (1.95 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

Comparison map

Figure 1b. This map compares Arctic sea ice extents between August 14, 2012 and August 14, 2019 from the NSIDC comparison tool.

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

From August 1 to 14, sea ice extent declined at a daily rate of 91,000 square kilometers (35,000 square miles), still above the 1981 to 2010 rate of decline of 71,000 square kilometers (27,400 square kilometers) during this period. However, this is still below the decline of 112,000 square kilometers (43,000 square miles) per day observed in 2012. At the beginning of the month, the 2019 ice extent was well below 2012. Because the decline through August was slower, the 2019 and 2012 sea ice extents are now close to each other. Because 2012 is a leap year, and our tracking follows the day of the year, August 13 in 2012 is August 14 in non-leap years. The ice extent for August 14, 2019 is 5.04 million square kilometers (1.95 million square miles), approximately 100,000 square kilometers (38,600 square miles) higher than for August 14, 2012 (Figure 1a).

Sea ice retreat in the first half of August 2019 was mainly in an area of patchy sea ice in the East Siberian Sea and along the ice edge in the northern Beaufort and Chukchi Seas. The Northern Sea Route appears to be open in our satellite-based mapping, but ice may remain in some areas. The Northwest Passage is still closed. There was little change in the ice edge in the Svalbard region and northern Barents and Laptev Seas. However, areas of low sea ice concentration are present along much of the remaining ice edge.

A comparison of 2019 and 2012 ice extent for August 14 shows remarkable similarities. In 2012, some patchy ice remained in the east Siberian Sea; however, the ice edge in the northeastern Beaufort and northern Chukchi Seas was further north, and some larger channels in the Canadian Archipelago were open (Figure 1b).

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of XXXXX XX, 20XX, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 in brown, 20XX in purple, and 20XX 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 2a. The graph above shows Arctic sea ice extent as of August 14, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. 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 July 1 - 14, 2019. 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 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for August 1 to 13, 2019. 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

Over the first half of the month, air temperatures along the Siberian coast at the 925 hPa level (about 2,500 feet above the surface) were generally 2 to 7 degrees Celsius (4 to 13 degrees Fahrenheit) above the 1981 to 2010 average, and 1 to 6 degrees Celsius (2 to 11 degrees Fahrenheit) above average over the Canadian Archipelago (Figure 2b). This was partly balanced by below-average temperatures in northern Scandinavia and the Kola Peninsula by 4 to 6 degrees Celsius (7 to 11 degrees Fahrenheit), a sharp counterpoint to the near-record heat of the late July European heat wave. Near-average temperatures prevailed over the central Arctic Ocean and slightly lower-than-average temperatures were present along the North Slope of Alaska and northwestern Canada. The atmospheric circulation was characterized by high pressure over the Northern Pacific, the Aleutians, and Greenland, and by a center of lower air pressure over northern European Russia. This combination drove cool Arctic air into Scandinavia and easternmost Russia.

Smoke gets in your ice

Figure 3. This NASA Worldview MODIS mosaic image from August 10, 2019, shows the locations of wildfires in the Arctic as detected by thermal images (not shown). Red areas indicate wildfires. Huge areas of burning forests in Siberia have filled the air with smoke over much of the Pacific side of the Arctic Ocean.||Credit: NASA Worldview| High-resolution image

Figure 3. This NASA Worldview image from August 10, 2019, shows the locations of wildfires in the Arctic as detected by thermal images (not shown). Red areas indicate wildfires. Huge areas of burning forests in Siberia have filled the air with smoke over much of the Pacific side of the Arctic Ocean. This image was taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite.

Credit: NASA Worldview
High-resolution image

Huge areas of burning forests in Siberia have filled the air with smoke over much of the Pacific side of the Arctic Ocean. However, at this late stage in the melt season, with rapidly declining solar input, it is unlikely to have much impact on sea ice loss. The fires are a result of the very warm and dry spring and summer conditions over the eastern Siberian Arctic.

There is such a thing as too thin

Figure 4a. This figure shows average Arctic sea ice thickness by month for several recent years as determined by PIOMAS.||Credit: Axel Schweiger, University of Washington| High-resolution image

Figure 4a. This figure shows average Arctic sea ice thickness by month from 1980 t0 2019 as determined by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).

Credit: Axel Schweiger, University of Washington
High-resolution image

Figure 4b. This map shows Arctic sea ice thickness difference from average, relative to 2011 to 2018, from PIOMAS. ||Credit: Axel Schwieger/University of Washington| High-resolution image

Figure 4b. This map shows Arctic sea ice thickness in July 2019 as a difference from average (in meters), relative to 2011 to 2018, from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).

Credit: Axel Schweiger, University of Washington
High-resolution image

Arctic sea ice volume, as estimated by a well-validated model produced by our colleagues at the University of Washington, is tracking at low levels as seen from satellite observations (Figure 4a). Arctic sea ice cover is thus very thin in addition to being very low in extent. Average Arctic sea ice thickness is estimated to be less than half of what it was at this time of year in 1980.

Sea ice thickness follows the change in the seasons. Early in the year, cold conditions and snowfall steadily thicken the sea ice. At the start of the melt season, typically in March, the thinner southern edges of sea ice cover melt first. Hence, the average thickness of the remaining sea ice increases, even though spring ice retreat has begun. By June, when much of the Arctic Ocean surface has reached the melting point, rapid thinning of the ice pack begins. Thickness and extent both reach a minimum in September. However, even though ice extent continues to decline through August, average sea ice thickness begins to increase slightly as the thinner ice at the edge melts away. Then, after the minimum extent, typically reached in mid-September, a rapid increase of sea ice extent begins, with thin sea ice covering large areas of the Arctic Ocean in a few weeks. This rapid increase of very thin ice reduces the average ice thickness, even though sea ice extent is increasing rapidly.

Is a new record minimum possible?

Figure 5. Comparison of several possible sea ice decline paths for 2019 with the 2012 minimum.

Figure 5. This figure compares 2019 projections of sea ice minimum extents based on rates of decline from previous years. The red line uses the rate of decline from the 1981 to 2010 reference period. The green line uses the rate of decline from 2007 to 2018 average. The dotted purple line uses the 2012 rate of decline and the dotted turquoise line uses the 2006 rate of decline.

Credit: Walt Meier, NSIDC
High-resolution image

The ASINA team conducted a revised analysis of the likely course of the 2019 Arctic summer sea ice minimum, using rates of loss from several recent years. While sea ice extent is now above extent for the same date in 2012, overall our projection for the minimum is lower than estimated in our previous post. Using the average decline rate of the past 12 years, from 2007 to 2018, the 2019 minimum is estimated to be 3.75 million square kilometers (1.45 million square miles). If the 2012 decline pattern is applied from August 14 forward, sea ice reaches 3.44 million square kilometers (1.33 million square miles). This is still above the 2012 summer minimum extent of 3.39 million square kilometers (1.31 million square miles). However, nearly all of the recent rates of sea ice loss lead to 2019 being second lowest in ice extent, surpassing 2007 and 2016.

Erratum

Readers alerted us to an error. On August 15, 2019, we reported that “Because 2012 is a leap year, and our tracking follows the day of the year, August 15 in 2012 is August 14 in non-leap years.” On August 26, 2019, we corrected this to say “August 13 in 2012 is August 14 in non-leap years.”

Europe’s heat wave moves north

Arctic sea ice extent in July tracked at record low levels for multiple individual days and for the month as a whole. During the second half of the month, air temperatures over the Arctic Ocean returned to average, while Europe experienced another record-breaking heat wave. By the end of the month, the European heat wave had moved north, enhancing melt over the Greenland ice sheet.

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 July 2019 was 7.59 million square kilometers (2.93 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for July 2019 set a new record low of 7.59 million square kilometers (2.93 million square miles). The monthly average extent was 80,000 square kilometers (30,900 square miles) below the previous record low set in 2012 and 1.88 million square kilometers (726,000 square miles) below the 1981 to 2010 average. On a daily basis, ice tracked at record low levels from July 10 through July 14 and July 20 through the end of the month. Ice retreated over most regions of the Arctic Ocean, especially over the Laptev Sea, northern Chukchi and Beaufort Seas, and Hudson Bay, where no ice remained at the end of the month. There was little retreat in the Barents Sea where the ice edge had already pulled back to its average northward position for this time of year. Ice also continued to linger along the coast in the East Siberian Sea near the Russian port town of Pevek and Wrangel Island. However, the sea ice concentrations in the region are now low, with many open water areas between ice floes. By the end of the month, the Northern Sea Route that links Europe and Asia through the East Siberian and Laptev Seas appeared to be essentially open, whereas the Northwest Passage (both the southern and northern routes) remained blocked by ice.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of XXXXX XX, 20XX, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 in brown, 20XX in purple, and 20XX 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 2a. The graph above shows Arctic sea ice extent as of July 31, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. Sea Ice Index data.

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

Figure 2b. The graph above shows Arctic sea ice extent decline per decade since satellite observations began in 1979. 1979 to 1989 is shown in light pink, the 1990s in dark pink, the 2000s in magenta, and the 201os in purple. 2019 is shown in a thick purple line ending on July 31, 2019, while the 2012 record low is also marked. ||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2b. The graph above shows Arctic sea ice extent decline per decade since satellite observations began in 1979. 1979 to 1989 is shown in light pink, the 1990s in dark pink, the 2000s in magenta, and the 201os in purple. 2019 is shown in a thick purple line ending on July 31, 2019, while the 2012 record low is also marked. Sea Ice Index data.

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

Figure 2c. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for July 2019. 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 air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for July 2019. 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

July is typically the warmest month of the year, with the largest rate of ice loss. Sea ice extent this July declined at an average rate of 105,700 square kilometers (40,800 square miles) per day, exceeding the 1981 to 2010 average of 86,800 square kilometers (33,500 square miles) per day. Only seven previous years—1990, 1991, 2007, 2009, 2013, 2015, and 2018—experienced daily rates of ice loss exceeding 100,000 square kilometers (38,600 square miles) per day, with 2007 holding the record low of 114,200 square kilometers (44,100 square miles) per day.

Rapid ice loss for July 2019 was in part driven by warm conditions during the first half of the month. The latter half of the month, in contrast, was relatively cool over the East Siberian and Laptev Seas, as well as near Svalbard and the Canadian Arctic Archipelago, where temperatures at the 925 hPa level (about 2,500 feet above the surface) were 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) below the 1981 to 2010 average. These relatively cool conditions were the result of below average sea level pressure centered over the East Siberian Sea, coupled with above average sea level pressure over the west Siberian Plain, which brought cold air southwards and helped to push the ice towards the coast. However, by July 30, the heat wave that had been plaguing Europe moved north, baking Greenland with temperatures at the 925 hPa level 10 degrees Celsius (18 degrees Fahrenheit) above average while parts of the Arctic Ocean saw temperatures 1 to 7 degrees Celsius (2 to 13 degrees Fahrenheit) above average. During this heat wave, about 60 percent of the Greenland ice sheet experienced melt. Despite the fluctuations during the month, the average monthly temperature was above average over most of the Arctic Ocean (Figure 2c).

By the beginning of August, the pace of ice loss tends to drop rapidly. 2012 was an exception, when the average August ice loss rate remained quite rapid at 89,500 square kilometers per day (34,600 square miles per day), leading to a new record low for the September minimum that year. As of August 5, 2019, the total sea ice extent has dropped below 6 million square kilometers, something which has not occurred prior to 1999. Sea ice extent in September of 2019 is likely to be among the five lowest minimums recorded.

July 2019 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 July ice extent for 1979 to 2019 shows a decline of 7.32 percent per decade.

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

In total, sea ice extent during July 2019 decreased by 3.28 million square kilometers (1.27 million square miles). This was larger than the 1981 to 2010 average loss for the month. The linear rate of sea ice decline for July from 1979 to 2019 is 693,000 square kilometers (268,000 square miles) per year, or 7.32 percent per decade relative to the 1981 to 2010 average.

Early melt brings early ice break-up and warmer ocean temperatures to the Beaufort Sea

Figure 4. Melt onset for 2019 expressed as differences (in days) with respect to 1981 to 2010 averages based on the passive microwave satellite data record. ||Credit: Data courtesy of Jeff Miller at NASA GSFC. | High-resolution image

Figure 4a. This map shows the 2019 melt onset expressed as differences (in days) with respect to 1981 to 2010 averages. Values are based on the passive microwave satellite data record.

Credit: Data courtesy of Jeff Miller at NASA Goddard Space Flight Center.
High-resolution image

Figure 4b. Sea surface temperature in degrees Celsius for July 31, 2019 from the University of Washington Polar Science Center UpTempO buoys and satellite-derived values from NOAA. ||Credit: National Oceanic and Atmospheric Organization| High-resolution image

Figure 4b. This map of the Arctic Ocean shows sea surface temperature in degrees Celsius for July 31, 2019. Data are from the University of Washington Polar Science Center UpTempO buoys and satellite-derived values from the National Oceanic and Atmospheric Association (NOAA).

Credit: National Oceanic and Atmospheric Association (NOAA)
High-resolution image

As mentioned in our July mid-month post, numerous ice floes have broken away from the main pack ice in the southern Beaufort Sea. This was in part fueled by early melt onset; ice began to melt nearly a month earlier than average (Figure 4a). Melt also started earlier than average within the northern Bering and southern Chukchi Seas and also within Baffin Bay along the west coast of Greenland. Melt onset over the central Arctic Ocean near the longitudes of the Laptev Sea, the Lincoln Sea, and parts of Hudson Bay was up to 20 days earlier than average. The timing of melt onset plays an important role in melt pond development and ice breakup, both of which allow for more solar radiation to be absorbed in the upper ocean, promoting more ice melt. The timing of melt pond development has been shown to be a useful predictor of how much ice will be left at the end of summer. The impact of this year’s early melt onset is evident in sea surface temperatures along the coast of Alaska and the Chukchi Sea, which are at least 5 degrees Celsius (9 degrees Fahrenheit) above average (Figure 4b).

Wildfires continue to rage across Arctic region

Figure 6a. MODIS image from July 24, 2019. Red dots show locations of fires. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 5a. This image from July 24, 2019 from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor shows the locations of fires (red dots) in the Arctic. Since the beginning of June, more than 100 large wildfires have been observed

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

Figure 6b. Fire radiative power from the Copernicus Atmosphere Monitoring Service (CAMS). Fire radiative power is a measure of heat output from wildfires as shown for June 2019 (red) and the 2003-2018 average (grey). ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 5b. This figure shows the Total Fire Radiative Power (TFRP) in the Arctic Circle detected by the Copernicus Atmosphere Monitoring Service (CAMS). Fire radiative power is a measure of heat output from wildfires as shown for June 2019 (red) and the 2003 to 2018 average (grey).

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

Figure 6c. Caption Needed||Credit: NASA Worldview|High-resolution image

Figure 5c. In this photo taken during a NOAA flight north of Utqiagvik, Alaska, sea ice appears to be highly decayed with deep melt ponds.

Credit: Kevin Woods, NOAA Pacific Marine Environmental Laboratory
High-resolution image

Another factor that plays a role in ice melt is deposition of dark soot from wildfires on the highly reflective snow and ice surfaces, allowing more of the sun’s energy to be absorbed. Since the beginning of June, more than 100 large wildfires have been observed over Arctic lands, including Alaska, Greenland, and Siberia (Figure 5a). Smoke from these fires has been observed to blow across Greenland and over sea ice areas. Wildfires do not only deposit soot, they also pose a health hazard to local communities. According to the European Union Copernicus Atmospheric Monitoring Service (CAMS), the fires this year are far more intense than normal, with a Total Fire Radiative Power (TFRP) up to about 10 times higher than average for a given date (Figure 5b). TFRP is derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data and incorporates the thermal radiation (intensity of buring) and the amount of smoke produced. Further, the fires release a substantial amount of carbon dioxide. The report notes that these fires have released as much carbon dioxide into the atmosphere as the annual total emissions of Sweden, or more than 50 megatons of this greenhouse gas; this is more than all fires within the same month between 2010 and 2018.

The National Oceanic and Atmospheric Administration (NOAA) has been tracking the melt season with aircraft flights over the ice north of Utqiagvik, Alaska, as part of its Arctic Heat program. While onboard some of these flights in mid-July, Kevin Woods of the NOAA Pacific Marine Environmental Lab in Seattle, Washington took several photos of the sea ice (Figure 5c). The ice appeared to be highly decayed with deep melt ponds, many melted completely through the ice. In other areas, the ice was sparse with isolated floes surrounded by open water. Much of this is likely to melt out completely by the end of the summer.

Open water again north of Greenland

Figure 7. Sea ice as seen from an aircraft over Utqiagvik, Alaska. The ice appeared to be highly decayed with deep melt ponds, many melted completely through the ice. ||Credit: Kevin Woods, NOAA Pacific Marine Environmental Lab | High-resolution image | High-resolution image

Figure 6. This true-color composite image taken by the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor shows sea ice as seen from an aircraft over Peary Land, Northeast Greenland. Areas of open water have appeared on the north coast of Greenland where two large floes that were fast ice broke away last week.

Credit: NASA
High-resolution image

Once again, areas of open water have appeared on the north coast of Greenland. A similar situation was observed during two periods in 2018, including one in mid-winter and one in late summer. Two large floes that were fast ice (attached to the coast) broke away last week (Figure 6). The largest floe is roughly 110 kilometers by 65 kilometers (70 miles by 40 miles), about 50 percent larger than the state of Rhode Island.

Antarctic update

Figure 8. Antarctic sea ice extent for May 2019 was 8.80 million square kilometers (3.40 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 7. Antarctic sea ice extent for May 2019 was 15.30 million square kilometers (5.91 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

Antarctic sea ice growth has been slightly slower than average since the end of the austral summer in March, pushing an already-low sea ice extent lower. By July, Antarctic sea ice extent was tracking among the lowest in the continuous satellite record. The other near-record years were widely dispersed (1983, 1986, 2002, and 2017), underscoring the high variability of Antarctic sea ice. While an overall positive linear trend is still evident in the 40-year Antarctic sea ice extent record, variability dominates, with 2014 being a record high maximum and 2017 a record low maximum extent.

Our site has from time to time noted the comings and goings of the Maud Rise Polynya, an opening within the pack ice thought to form when deeper warm water is forced to the surface. In late July, a similar feature formed in the Cosmonaut Sea, the name for the area of the Southern Ocean along the western coast of Enderby Land (40 degrees to 55 degrees E longitude). The Cosmonaut Sea Polynya has been identified and studied for many years, first in 1987. It can appear in July or August as the sea ice edge expands northward over a region near 66 degrees S, 43 degrees E, occurring in about a third of the winter sea ice seasons. The polynya is formed by a combination of ocean currents and winds that create an upward dome shape in warmer, or a few degrees above freezing, deep ocean layers. If this warmer water mixes upward, it prevents the formation of sea ice even as cold winter weather freezes adjacent areas.

References

Comiso, J. C. and Gordon, A. L. 1987. Recurring polynyas over the Cosmonaut Sea and the Maud Rise. Journal of Geophysical Research: Oceans. doi: 10.1029/JC092iC03p02819.

Schröder, D., D. L. Feltham, D. Flocco, and M. Tsamados. 2014. September Arctic sea-ice minimum predicted by spring melt-pond fraction. Nature: Climate Change. doi:10.1038/NCLIMATE2203.

Markus, T., J. C. Stroeve, and J. Miller. 2009. Recent changes in Arctic sea ice melt onset, freezeup, and melt season length. Journal of Geophysical Researchdoi:10.1029/2009JC005436.

Stroeve, J. C., T. Markus, L. Boisvert, J. Miller, and A. Barrett. 2014. Changes in Arctic melt season and implications for sea ice loss. Geophysical Research Letters. doi.org/10.1002/2013GL058951.

Beware the Ides of July

Loss of ice extent through the first half of July matched loss rates observed in 2012, the year which had the lowest September sea ice extent in the satellite record. Surface melt has become widespread and there is low concentration ice in the Beaufort Sea. However, projections suggest that a new record low extent is unlikely this year.

Overview of conditions

Figure 1. Arctic sea ice extent for July 15, 2019 was 7.91 million square kilometers (3.05 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 July 15, 2019 was 7.84 million square kilometers (3.03  million square miles). The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

As of July 15, Arctic sea ice extent was 7.84 million square kilometers (3.03 million square miles). This is 1.91 million square kilometers (737,000 square miles) below the 1981 to 2010 average and nearly the same as the July 14, 2012 extent. Since the beginning of the month, the ice edge has receded in most coastal areas and the open water region in the Laptev Sea has expanded.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of July 14, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of July 15, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. 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 July 1 - 14, 2019. 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 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for July 1 – 14, 2019. 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 average sea level pressure in the Arctic in millibars (hPa) for July 1 - 14, 2019. 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

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars (hPa) for July 1 – 14, 2019. 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

The first half of July is generally the period of most rapid ice loss. As averaged over the 1981 to 2010 period, extent drops 80,000 square kilometers (30,900 square miles) per day in the 1981 to 2010 climatology over this period. In recent years, daily loss rates have been higher. This year, most days during the first half of July had rates exceeding 100,000 square kilometers (38,600 square miles) per day, which is similar to what has been observed over the past several years.

It has been warm through mid-July, with air temperatures at the 925 hPa level (about 2,500 feet above the surface) averaging at least 3 degrees C (5 degrees F) above the 1981 to 2010 average over much of the Arctic Ocean and some areas, such as the Chukchi and East Siberian Seas, experiencing temperatures 5 degrees C (9 degrees F) above average. Alaska was subjected to especially warm conditions compared to average, with record highs being set throughout the state early in the month.

High pressure at sea level has persisted into July over the Arctic Ocean, resulting in fairly clear skies that are associated with enhanced surface melt.

Breakup in the Beaufort

Ice floes in the Beaufort Sea

Figure 3a. This shows a true-color composite image of broken up sea ice in the Beaufort Sea, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra satellite on July 8, 2019.

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

Melt ponds form in the Canadian Archipelago

Figure 3b. This image from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) shows sea ice in the Canadian Archipelago on July 7, 2019. The blue hues indicate areas of widespread surface melt and melt ponds on the surface of the ice.

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

In the southwestern Beaufort Sea, numerous floes have broken away from the main pack ice and have been drifting southward. These will be encountering warm water and will be prone to rapid melt. Nearby in the Canadian Archipelago, the ice has turned a bluish tint in visible imagery, indicating significant surface melt and melt ponds. There is evidence of melt ponds elsewhere over the Arctic Ocean, particularly in the Laptev and East Siberian Seas.

Is a new record low in the offing?

Figure 4. This figure compares 2019 projections of sea ice minimum extents based on rates of decline from previous years. The 2012 minimum extent of 3.39 million square kilometers (1.31 million square miles) is marked with a dashed black line. The red line uses the rate of decline from the 1981 to 2010 reference period. The green line uses the rate of decline from 2007 to 2018 average. The dotted purple line uses the 2012 rate of decline, and the dotted turquoise line uses the 2006 rate of decline.

Credit: W. Meier, NSIDC
High-resolution image

With extent tracking near 2012 levels and atmospheric conditions conducive to rapid ice loss, it is tempting to speculate whether September extent will drop below the record low observed in 2012. A simple way to investigate this possibility is to project forward from this year’s current extent using ice loss rates from other years to estimate extents through the remainder of the summer. Based on this approach, prospects of a new record low appear slim; a new record low would only occur if loss rates followed those observed in 2012, which were very rapid because of persistent warm conditions through the melt season, with ice loss potentially enhanced by the passage of a strong cyclone in August.

Sea ice age update

Figure5a

Figure 5. Sea ice age for (a) January 1-7, 2019 and (b) June 25 - July 1, 2019. The short tongue of ice in the eastern Beaufort Sea in January has been stretched and deformed into the “Z” shaped feature seen in the late June image. NSIDC DAAC Quicklook data.||Credit: National Snow and Ice Data Center|High-resolution image

Figures 5a and b. The top map shows sea ice age for January 1 to 7, 2019, and the bottom map shows June 25 to July 1, 2019. The short tongue of ice in the eastern Beaufort Sea in January has been stretched and deformed into the “Z” shaped feature seen in the late June image. Quicklook data.

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

As of the beginning of July, large swaths of first-year ice covered the Arctic Ocean. Thicker, older ice is primarily found in a band between the North Pole, the Canadian Archipelago, and the northern Greenland coast. A narrow strip of second-year ice extends across the Pole into the East Siberian Sea. Another distinctive feature is a “Z” pattern of older ice in the Beaufort Sea induced by the clockwise Beaufort Gyre high pressure pattern, that transported ice eastward and northward over the course of the winter and spring. Some ice got “snagged” on Point Barrow, causing the pattern of old ice to deform into the “Z” shape. With so much first-year ice in the Arctic Ocean and roughly two months left of the melt season, there are many remaining areas of potential ice loss. But how much and where ice is lost will depend significantly on the weather patterns over the next eight weeks.

Melt season shifts into high gear

After a period of slow ice loss in the middle of June, Arctic sea ice loss ramped up, and extent at the end of the month fell below 2012, the year which ended up with the lowest September ice extent in the satellite record. A pattern of atmospheric circulation favored ice loss this June, which was also characterized by above average temperatures over most of the Arctic Ocean, and especially in the Laptev and East Siberian Seas.

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 June 2019 was 10.53 million square kilometers (4.07 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 averaged 10.53 million square kilometers (4.07 million square miles). This is 1.23 million square kilometers (475,000 square miles) below the 1981 to 2010 average and 120,000 square kilometers (46,300 square miles) above the previous June record low set in 2016. Extent at the end of the month remained well below average on the Pacific side of the Arctic, with open water extending from the Bering Strait, and along the coasts of the Chukchi and Beaufort Seas all the way to Melville Island in the Canadian Arctic Archipelago. Sea surface temperatures (SSTs) in the open waters have been unusually high, up to 5 degrees Celsius (9 degrees Fahrenheit) above average in the Chukchi Sea, as indicated by the National Oceanic and Atmospheric Administration (NOAA) SST data provided on the University of Washington Polar Science Center UpTempO website. Large areas of open water are now apparent in the Laptev and Kara Seas with extent below average in Baffin Bay and along the southeast coast of Greenland.

Extent over the first 10 days of the month dropped quickly but then the loss rate suddenly slowed. From June 12 through June 16, extent remained almost constant at 10.8 million square kilometers (4.17 million square miles). Following this hiatus, extent then dropped fairly quickly through the remainder of the month. Overall, sea ice retreated almost everywhere in the Arctic in June. Exceptions included the northern East Greenland Sea, southeast of Svalbard, near Franz Joseph Land, and in the southeastern part of the Beaufort Sea, where the ice edge expanded slightly.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July 1, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of July 1, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. Sea Ice Index data.

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

Figure 2X. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for June 2019. 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 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for June 2019. 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 2X. This plot shows average sea level pressure in the Arctic in millibars (hPa) for June 2019. 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

Figure 2c. This plot shows average sea level pressure in the Arctic in millibars (hPa) for June 2019. 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 May’s theme, air temperatures at the 925 hPa level (about 2,500 feet above the surface) in June were above the 1981 to 2010 average over most of the Arctic Ocean. However, the spatial patterns between the two months were different. While in May, it was particularly warm compared to average over Baffin Bay and a broad area north of Greenland, in June the maximum warmth of more than 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) shifted to the Laptev and East Siberian Seas (Figure 2b). It was slightly cooler than average over the northern Barents and Kara Seas and over central Greenland and the western Canadian Arctic.

The atmospheric circulation at sea level featured high pressure over the north American side of the Arctic, with pressure maxima over Greenland and in the Beaufort Sea, paired with low pressure over the Eurasian side of the Arctic, with the lowest pressures over the Kara Sea (Figure 2c). This pattern drew in warm air from the south over the Laptev Sea where temperatures were especially high relative to average. This circulation pattern bears some resemblance to the Arctic Dipole pattern that is known to favor summer sea ice loss, which was particularly well developed through the summer of 2007. So far, the pattern for the 2019 melt season is very different than the past three years, which featured low pressure over the central Arctic Ocean.

June 2019 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 June ice extent for 1979 to 2019 shows a decline of 4.08 percent per decade.

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

The average extent for June 2019 of 10.53 million square kilometers (4.07 million square miles) ended up as the second lowest in the satellite record. The current record low of 10.41 million square kilometers (4.02 million square miles) was set in June 2016. Overall, sea ice extent during June 2019 decreased by 2.03 million square kilometers (784,00 square miles). Because of the fairly slow loss rate near the middle of the month, the overall loss rate for June ended up being fairly close to the 1981 to 2010 average. The linear rate of sea ice decline for June from 1979 to 2019 is 48,000 square kilometers (19,00 square miles) per year, or 4.08 percent per decade relative to the 1981 to 2010 average.

Sea Ice Outlook posted for June

Projections of total Arctic sea ice extent based on conditions in May. https://www.arcus.org/sipn/sea-ice-outlook/2019/june

Figure 4. This chart shows the projections of total Arctic sea ice extent based on conditions in May from 31 contributors.

Credit: Sea Ice Prediction Network
High-resolution image

The Sea Ice Prediction Network–Phase 2 recently posted the 2019 Sea Ice Outlook June report. This report focuses on projections of September sea ice extent based on conditions in May. The projections come variously from complex numerical models to statistical models to qualitative perspectives from citizen scientists. There were 31 contributions for projected total Arctic sea ice extent and of these 31, nine also provided projections for extent in Alaska waters, and six provided projections of total Antarctic extent (Figure 4). There were also seven predictions of September extent for Hudson Bay.

The median of the projections for the monthly mean September 2019 total Arctic sea ice sea-ice extent is 4.40 million square kilometers (1.70 million square miles) with quartiles (including 75 percent of the 31 projections) of 4.2 and 4.8 million square kilometers (1.62 and 1.85 million square miles). The observed record low September extent of 3.6 million square kilometers (1.39 million square miles) was set 2012. Only three of the projections are for a September 2019 extent below 4.0 million square kilometers (1.54 million square miles) and only one is for a new record at 3.06 million square kilometers (1.18 million square miles).

Thicker clouds accelerate sea decline

Figure 5. These plots show linear trends of satellite-retrieved cloud cover, percent per year, for March through June over the Arctic (70 to 90 degrees North) from 2000 to 2015. Blues depict declines in cloud cover while reds depict increases. Cloud observations are derived from CERES-MODIS SYN1 Ed3.0 product. || Credit: Huang, Y. et al., 2019, Geophysical Research Letters | High-resolution image

Figure 5. These plots show linear trends of satellite-retrieved cloud cover, percent per year, for March through June over the Arctic (70 to 90 degrees North) from 2000 to 2015. Blues depict declines in cloud cover while reds depict increases. Cloud observations are derived from CERES-MODIS SYN1 Ed3.0 product.

Credit: Huang, Y. et al., 2019, Geophysical Research Letters
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A new study led by Yiyi Huang of the University of Arizona presents evidence of a link between springtime cloud cover (Figure 5) over the Arctic Ocean and the observed decline in sea ice extent. Based on a combination of observations and model experiments, there may be a reinforcing feedback loop. As sea ice melts, there is more open water which promotes more evaporation from the surface and hence more water vapor in the atmosphere. More water vapor in the air then promotes the development of more clouds. This increases the emission of longwave radiation to the surface, further fostering melt. The process appears to be effective from April through June. But since the atmosphere influences the sea ice and the sea ice influences the atmosphere, separating cause and effect remains unclear.

Antarctic sea ice at record low for June

Figure 5.

Figure 6a. This plot shows the evolution of linear trends in annual average sea ice extent for the Arctic, in blue, and Antarctic, in red. The trend was first computed from 1979 through 1990, then from 1979 through 1991, then 1979 through 1992, and so on. Even with the recent declines in Antarctic sea ice extent, the linear trend is still slightly positive. The reason for starting the trend calculation from 1979 through 1990 is that it provides a sufficient number of years to compute a trend.

Credit: W. Meier, NSIDC
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Annual mean sea ice extent from 1979 through 2018 in the Arctic and Antarctic from the Sea Ice Index using the NASA Team sea ice algorithm.

Figure 6b. This plot shows the average annual sea ice extent from 1979 through 2018 in the Arctic, in blue, and Antarctic, in red, from the Sea Ice Index using the NASA Team sea ice algorithm.

Credit: J. Stroeve, NSIDC
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Sea ice surrounding Antarctica was at the lowest mean monthly extent for June, surpassing 2002 and 2017. At the month’s end, sea ice averaged approximately 160,000 square kilometers (62,000 square miles) below the previous record low set in 2002, and over 1.1 million square kilometers (425,000 square miles) below the 1981 to 2010 average. Ice extent was particularly low in the eastern Weddell Sea and the region north of Enderby Land (south of the western Indian Ocean), and north of eastern Wilkes Land. No region had substantially above average sea ice extent in June.

A new paper published by our colleague Claire Parkinson at NASA Goddard Space Flight Center (GSFC) discusses the large drop in Antarctic sea ice extent between 2014 and 2017. The winter maximum for 2014 was unusually high, setting the 40-year record maximum extent. Our earlier posts noted the dramatic recent decline, particularly in the austral spring of 2016. Sea ice has remained below the 1981 to 2010 reference period extent since late 2016.

While the recent decline is noteworthy, trends in Antarctic sea ice extent over the continuous satellite record since late 1978 remain slightly positive (Figure 6a). Antarctica experiences large inter-annual variability because of its unconfined geography—open to the Southern Ocean on all sides—and strong influences of the varying Southern Annular Mode pattern of atmospheric circulation. Sparse satellite data from the 1960s indicate large swings in that decade as well. Previous studies have attributed the onset of the recent decline as a response to a series of intense storms. Unlike Arctic sea ice extent, which evinces a longterm downward trend, Antarctic sea ice extent displays enormous variability that is natural for the southern sea ice system (Figure 6b). Thus, a clear climate-related signal cannot yet be discerned for sea ice in the southern hemisphere.

Reference

Gallaher, D. W., G. G. Campbell and W. N. Meier. 2013. Anomalous variability in Antarctic sea ice extents during the 1960s with the use of Nimbus data. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 7(3), pp. 881-887. doi:10.1109/JSTARS.2013.2264391.

Huang, Y., X. Dong, D. A. Bailey, M. M. Holland, B. Xi, A. K. DuVivier, et al. 2019. Thicker clouds and accelerated Arctic sea ice decline: The atmosphere‐sea ice interactions in spring. Geophysical Research Letters, 46. doi:10.1029/2019GL082791.

Parkinson, C. L. 2019. A 40-year record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic. Proceeding of the National Academy of Sciences (PNAS), July, pp. 1-10. doi:10.1073/pnas.1906556116.

Turner, J., T. Phillips, G. J. Marshall, J. S. Hosking, J. O. Pope, T. J. Bracegirdle, and P. Deb. 2017. Unprecedented springtime retreat of Antarctic sea ice in 2016. Geophysical Research Letters, 44(13), pp. 6868-6875. doi:10.1002/2017GL073656.

Warm May in the Arctic sets the stage

May saw above average temperatures over nearly all of the Arctic Ocean, Baffin Bay, and Greenland. Early sea ice retreat in the Bering Sea extended into the southern Chukchi Sea. Northern Baffin Bay and the Nares Strait have low ice cover. By month’s end, open water extended along the northeastern Alaskan and northwestern Canadian coasts, all well ahead of schedule. However, this was partly balanced by slower-than-average ice loss in the Barents Sea. At the end of May, Arctic sea ice daily extent stood at second lowest in the 40-year 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 May 2019 was 12.16 million square kilometers (4.70 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 averaged for May was 12.16 million square kilometers (4.70 million square miles). This is 1.13 million square kilometers (436,000 square miles) below the 1981 to 2010 average and 240,000 square kilometers (93,000 square miles) above the previous record low for the month set in May 2016. The month saw rapid ice loss in the Bering Sea and southern Chukchi Sea. During the second half of the month, an extended coastal polynya opened along the northwestern coast of the Beaufort Sea extending into the Mackenzie River Delta area. Visible MODIS imagery shows many large ice floes interspersed with open water along the ice edge and fracturing of ice further within the pack.

Although ice loss in the Barents Sea was rapid in early May, it subsequently slowed and extent slightly increased late in the month. There was nevertheless an overall ice retreat for May as a whole. Around mid-month, a polynya began to open at the north end of Baffin Bay, near the Nares Strait. At about this time, an ice arch that restrains southward ice drift in the Lincoln Sea began to fail, allowing transport of ice through the strait and creating a small polynya northwest of Greenland (discussed below). By the end of May, other polynyas started to form around the New Siberian Islands as well as Severnaya Zemlya, and open water began to develop along coastal regions in the Kara Sea and in northern Hudson Bay.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of June 3, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of June 3, 2019, along with daily ice extent data for four previous years and the record low year. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. 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, for May 2019. 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 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for May 2019. 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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Broadly following the pattern for April, air temperatures at the 925 hPa level (approximately 2,500 feet above the surface) for May were again well above average over nearly all of the Arctic Ocean. Along the western Greenland coast, a broad area north of Greenland, and westward north of the Canadian Archipelago, temperatures were as much as 7 degrees Celsius (13 degrees Fahrenheit) above the 1981 to 2010 reference average for the month. Over much of the remainder of the Arctic Ocean, temperatures were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average. By contrast, over the Barents Sea as well as along the Laptev Sea coast, temperatures were near average or up to 2 degrees (4 degrees Fahrenheit) below average. As averaged for May, there was an area of high sea level pressure, an anticyclone, centered near the pole. This pattern drew warm air from the south into Baffin Bay and into the Arctic Ocean. Also, air under an anticyclone descends and warms. Both factors help to explain the unusually high temperatures over much of the Arctic Ocean.

May 2019 compared to previous years

Figure 3. Monthly May ice extent for 1979 to 2019 shows a decline of X.X percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly May ice extent for 1979 to 2019 shows a decline of 2.74 percent per decade.

Credit: National Snow and Ice Data Center
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Overall, sea ice extent during May 2019 decreased by 1.49 million square kilometers (575,300 square miles). This was fairly close to the 1981 to 2010 average loss for the month. The linear rate of sea ice decline for May from 1979 to 2019 is 36,400 square kilometers (14,100 square miles) per year, or 2.74 percent per decade relative to the 1981 to 2010 average.

Ice arch break up in the Lincoln Sea

Figure 4. Animation from Aqua MODIS true color composite images from NASA Worldview. The animation was created using the new Worldview animation function.||Credit: NASA| High-resolution image

Figure 4. This NASA Worldview (download to view animation) image shows sea ice in the Nares Strait from April 19 to May 11. A new Worldview functions creates an animation using Aqua Moderate Imaging Spectroradiometer (MODIS) true color composite images.

Credit: NASA
High-resolution image

In most years (2007 being a notable exception), an ice arch forms during late autumn and winter at the north end of Nares Strait, the narrow passage that separates Greenland from Ellesmere Island. This arch acts as a barrier, preventing ice from the Arctic Ocean from drifting through the strait and into Baffin Bay. The arch typically breaks up in June or July, allowing ice to drift through the narrow channel. This year, the arch broke up by late March, much earlier than is typical. Since then, there has been a steady flow of ice through Nares Strait (download animation to view). Since 2000, only four other years appear to have had similar early breakups of the arch: 2007 (when no arch formed at all), 2008, 2010, and 2017 (Moore et al., 2018). Typically, strong wind events trigger the break up, but warm temperatures and thinner ice can also contribute.

Arctic sea ice variability linked to atmospheric temperature fluctuations

Figure 5. Top, this figure shows how the year-to-year sea ice area co-varies with mid-atmosphere temperatures (average of temperatures between 850 HPa to 400 HPa, or about 5000 to 25000 feet above sea level). Below, a bar graph provides the contributions of other suggested mechanisms – combined, they account for about 25 percent of the sea ice variations. The direct influence of mid-atmosphere temperature fluctuations remains as the primary cause of year-to-year sea-ice variations. ||Credit: NSIDC Sea Ice index and ERA-Interim Reanalysis | High-resolution image

Figure 5. The top figure shows how the year-to-year sea ice area co-varies with mid-atmosphere temperatures (average of temperatures between 850 HPa to 400 HPa, or about 5,000 to 25,000 feet above sea level). The below bar graph provides the contributions of other suggested mechanisms. Combined, they account for about 25 percent of the sea ice variations. The direct influence of mid-atmosphere temperature fluctuations remains as the primary cause of year-to-year sea-ice variations.

Credit: NSIDC Sea Ice Index and ERA-Interim Reanalysis
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While Arctic sea ice extent is declining sharply, it is also highly variable from one year to the next. Scientists from the Max Planck Institute for Meteorology (MPI-M) and the University of Stockholm have proposed that this strong variability is closely related to fluctuations in the air temperature above the Arctic Ocean driven by atmospheric heat transport into the Arctic from lower latitudes. In contrast to previous assumptions, they argue that other factors, such as the ice-albedo feedback, cloud and water vapor feedbacks, and oceanic heat transported into the Arctic together explain only 25 percent of the year-to-year sea ice extent variations. Most of the sea ice variations are thus directly caused by mid-atmospheric temperature conditions; this is evident in both observational data and climate models. Their study implies that year-to-year fluctuations in sea ice extent are easier to understand than previously thought. However, their study also suggests that it may be more difficult to predict the summer extent of Arctic sea ice from one year to the next, because the problem of predicting atmospheric heat transport is closely related to the challenges of long-term weather forecasting.

Antarctic sea ice extent exceptionally low in the Weddell and Amundsen Seas

Figure 6. Antarctic sea ice extent for May 2019 was 12.16 million square kilometers (4.69 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 6. Antarctic sea ice extent for May 2019 was 8.80 million square kilometers (3.40 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

Antarctic sea ice extent continues to climb toward its seasonal maximum, which is expected in late September or early October. At the end of May, Antarctic sea ice extent was very close to record daily lows over the period of satellite observations, previously set for the month in 1980. Unusually low ice extent in the eastern Weddell Sea and northern Amundsen Sea are responsible for the low overall total extent, with smaller areas of open water in the eastern Wilkes Land coastal region and southwestern Indian Ocean (Cosmonaut Sea). Slightly above average sea ice extent is present in the north-central Ross Sea and northwestern Weddell Sea.

References

Kwok, R., L. Toudal Pedersen, P. Gudmandsen, and S. S. Pang. 2010. Large sea ice outflow into the Nares Strait in 2007. Geophysical Research Letters. doi: 10.1029/2009GL041872.

Moore, G. W. K. and K. McNeil. 2018. The early collapse of the 2017 Lincoln Sea ice arch in response to anomalous sea ice and wind forcing. Geophysical Research Lettersdoi:10.1029/2018GL078428.

Olonscheck, D., T. Mauritsen, and D. Notz. 2019. Arctic sea-ice variability is primarily driven by atmospheric temperature fluctuations. Nature Geoscience. doi:10.1038/s41561-019-0363-1.

Rapid ice loss in early April leads to new record low

April reached a new record Arctic low sea ice extent. Sea ice loss was rapid in the beginning of the month because of declines in the Sea of Okhotsk. The rate of ice loss slowed after early April, due in part to gains in extent in the Bering and Barents Seas. However, daily ice extent remained at record low levels throughout the month.

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 April 2019 was 13.45 million square kilometers (5.19 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for April 2019 averaged 13.45 million square kilometers (5.19 million square miles). This was 1.24 million square kilometers (479,000 square miles) below the 1981 to 2010 long-term average extent and 230,000 square kilometers (89,000 square miles) below the previous record low set in April 2016.

Rapid ice loss occurred in the Sea of Okhotsk during the first half of April; the region lost almost 50 percent of its ice by April 18. Although sea ice was tracking at record low levels in the Bering Sea from April 1 to 12, the ice cover expanded later in the month. Elsewhere, there was little change except for small losses in the Gulf of St. Lawrence, the southern part of the East Greenland Sea, and southeast of Svalbard. In addition, open water areas developed along coastal regions of the Barents Sea. The ice edge expanded slightly east of Novaya Zemlya.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of May 1, 2019, along with daily ice extent data for four previous years and 2012. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of May 1, 2019, along with daily ice extent data for four previous years and 2012. 2019 is shown in blue, 2018 in green, 2017 in orange, 2016 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. 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 April 2019. 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 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for April 2019. 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

Air temperatures at the 925 hPa level (approximately 2,500 feet above the surface) were above average across the Arctic during the first two weeks of April, especially over the East Siberian Sea and the Greenland Ice Sheet where air temperatures were as much as 9 degrees Celsius (16 degrees Fahrenheit) above average (Figure 2b). Elsewhere, 925 hPa temperatures were between 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) above average, including the Sea of Okhotsk where ice loss early in the month was especially prominent. These relatively warm conditions were linked to a pattern of high sea level pressure over the Beaufort Sea paired with low sea level pressure over Alaska, Siberia, and the Kara and Barents Seas. This drove warm air from the south over the East Siberian Sea. Similarly, high pressure over Greenland and the North Atlantic, coupled with low sea level pressure within Baffin Bay, helped usher in warm air over southern Greenland from the southeast.

During the second half of the month, temperatures remained above average over most of the Arctic Ocean, and up to 8 degrees Celsius (14 degrees Fahrenheit) above average over the East Greenland Sea. However, temperatures were 1 to 5 degrees Celsius (2 to 9 degrees Fahrenheit) below average over the Bering Sea, and up to 8 degrees Celsius (14 degrees Fahrenheit) below average over the Canadian Arctic Archipelago. Air temperatures were slightly below average in the Kara Sea.

April 2019 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 April ice extent for 1979 to 2019 shows a decline of 2.64 percent per decade.

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

The 1979 to 2019 linear rate of decline for April ice extent is 38,800 square kilometers (15,000 square miles) per year, or 2.64 percent per decade relative to the 1981 to 2010 average.

Sea ice age update

Figure 4. Maps (a) and (b) compare Arctic sea ice age between two date ranges: April 8 to 14, 1984, and April 9 to 15, 2019. Graph (c) shows sea ice age as a percentage of Arctic Ocean coverage from 1984 to 2019 in mid-April. ||Credit: W. Meier, NSIDC|High-resolution image

Figure 4. The top maps compare Arctic sea ice age for (a) April 8 to 14, 1984, and (b) April 9 to 15, 2019. The time series (c) of mid-April sea ice age as a percentage of Arctic Ocean coverage from 1984 to 2019 shows the nearly complete loss of 4+ year old ice; note the that age time series is for ice within the Arctic Ocean and does not include peripheral regions where only first-year (0 to 1 year old) ice occurs, such as the Bering Sea, Baffin Bay, Hudson Bay, and the Sea of Okhotsk.

Credit: W. Meier, NSIDC
High-resolution image

Younger sea ice tends to be thinner than older ice. Therefore, sea ice age provides an early assessment of the areas most susceptible to melting out during the coming summer. The Arctic sea ice cover continues to become younger (Figure 4), and therefore, on average, thinner. Nearly all of the oldest ice (4+ year old), which once made up around 30 percent of the sea ice within the Arctic Ocean, is gone. As of mid-April 2019, the 4+ year-old ice made up only 1.2 percent of the ice cover (Figure 4c). However, 3 to 4-year-old ice increased slightly, jumping from 1.1 percent in 2018 to 6.1 percent this year. If that ice survives the summer melt season, it will somewhat replenish the 4+ year old category going into the 2019 to 2020 winter. However, there has been little such replenishment in recent years.

The sea ice age data products were recently updated through 2018 (Version 4, Tschudi et al., 2019). Data is available here. In addition, an interim QuickLook product that will provide preliminary updates every month is in development.

Changing ice and sediment transport

Figure 5. This figure shows three different aspects of ice formation in the Arctic Ocean. |Figure 5a. This map shows the Transpolar Drift and pack ice carried from the Siberian shelf seas towards Fram Strait.|Figure 5b. This illustration shows the process of ice formation. |Figure 5c. This graph shows the probability that newly formed ice in the winter will survive the summer. ||Credit: T. Krumpen|High-resolution image

Figure 5a. This map shows the main sea ice drift patterns.
Figure 5b. This illustration shows how sediments can be ingrained into the newly forming sea ice.
Figure 5c. This graph shows the probability that newly formed ice in the winter will survive the summer.

Credit: T. Krumpen
High-resolution image

Figure 5. This image shows sediment-rich sea ice in the Transpolar Drift. Two researchers were lowered by crane from the decks of the icebreaker RV Polarstern to the surface of the ice to collect samples. Photo Credit: R. Stein, AWI, 2014.

Figure 5d. This image shows sediment-rich sea ice in the Transpolar Drift Stream. A crane lowers two researchers from the decks of the icebreaker RV Polarstern to the surface of the ice to collect samples.

Photo Credit: R. Stein, Alfred Wegener Institut
High-resolution image

Scientists from the Alfred Wegener Institut (AWI) monitored and analyzed sea ice motion using satellite data from 1998 to 2017 and concluded that only 20 percent of the sea ice that forms in the shallow Russian seas of the Arctic Ocean now reaches the central Arctic Ocean to join the Transpolar Drift Stream (Figures 5a and b). The Russian seas, including the Kara, Laptev, and East Siberian Seas, are considered the ice nursery of the Arctic. The remaining 80 percent of this first-year ice melts before it has a chance to leave this nursery. Prior to the year 2000, that number was about 50 percent (Figure 5c).

These conclusions find support from sea ice thickness observations in Fram Strait, which is fed by the Transpolar Drift Stream. AWI scientists regularly gather ice thickness data in Fram Strait as part of their IceBird program. The ice now leaving the Arctic Ocean through the Fram Strait is, on average, 30 percent thinner than it was 15 years ago. There are two reasons for this. First, winters are warmer and the melt season now begins much earlier than it used to. Second, much of this ice no longer forms in the shallow seas, but much farther north. As a result, it has less time to thicken from winter growth and/or ridging as it drifts across the Arctic Ocean.

These changes in transport and melt affect biogeochemical fluxes and ecological processes in the central Arctic Ocean. For example, in the past, the sea ice that formed along the shallow Russian seas transported mineral material, including dust from the tundra and steppe, to the Fram Strait (Figure 5d). Today, the melting floes release this material en route to the central Arctic Ocean. Far less material now reaches the Fram Strait and it is different in composition. This finding is based on two decades of data sourced from sediment traps maintained in the Fram Strait by AWI biologists. Instead of Siberian minerals, sediment traps now contain remains of dead algae and microorganisms that grew within the ice as it drifted.

Putting current changes into longer-term perspective

Figure6updated

Figure 6. This map shows Arctic regions used in the Walsh et al. study and how much each area’s September extent contributes to the total September sea ice extent. The top number gives the percentage (as squares of correlations, or R2) when the raw 1953 to 2013 ice extent time series is used. The bottom number (bold) gives what the percentage drops to after the time series data have been detrended. For example, about 70 percent of the September Arctic-wide extent number is explained by the September extent in the seas north of Alaska, but that drops to about 20 percent once the trends have been removed.

Credit: Walsh et al., 2019, The Cryosphere
High-resolution image

While changes in sea ice extent over the past several decades are usually shown as linear trends, they can mask important variations and changes. A recent study led by John Walsh at University Alaska Fairbanks compared various trend-line fits to sea ice extent time series back to 1953, for the Arctic as a whole and various sub-regions. This data set extends the satellite record by using operational ice charts and other historical sources (Walsh et al., 2016). They found that a two-piece linear fit with a break point in the 1990s provides a more meaningful basis for calculations of sea ice departures from average conditions and their persistence, rather than a single trend line computed over the period 1953 to the present. Persistence of sea ice departures from average conditions represents the memory of the system, which can be used to forecast sea ice conditions a few months in advance. September Arctic-wide ice extent can also be predicted with some limited skill when the data include the trend. However, this apparent skill largely vanishes when the trend is removed from the data using the two-piece linear fit. This finding is consistent with the notion of a springtime predictability barrier, such that springtime sea ice conditions are usually not a strong predictor of the summer ice cover because atmospheric circulation patterns in summer erode this memory in the system. For example, despite the extensive coverage of fairly young—and hence thin—ice this spring, cool summer weather conditions may limit melt, leading to a higher September ice extent than might otherwise be expected.

April snow melt in Greenland—notable but not unusual

Temperatures were well above average over Greenland for much of April but were still below freezing except near the coast. Satellite data indicate that there was a small area surface melt on the southeastern coastal part of the ice sheet early in the month. In the last week of April, melt became more extensive, spreading further north on the east coast and starting on the west coast. While interesting, this is not especially unusual. Most years of the past decade have some surface melt in April. In 2012 and 2016, strong melt events occurred in April that covered a much larger area than in 2019. NSIDC is now tracking Greenland surface melt for 2019 on a daily basis.

Further reading

Krumpen, T., H. J. Belter, A. Boetius, E. Damm, C. Haas, S. Hendricks, M. Nicolaus, E.-M. Nöthig, S. Paul, I. Peeken, R. Ricker, and R. Stein. 2019. Arctic warming interrupts the Transpolar Drift and affects long range transport of sea ice and ice-rafted matter. Scientific Reports. doi:10.1038/s41598-019-41456-y.

Tschudi, M. A., W. N. Meier, and J. S. Stewart. 2019. An enhancement to sea ice motion and age products. The Cryosphere Discussion, in review. doi:10.5194/tc-2019-40.

Walsh, J. E., W. L. Chapman, and F. Fetterer. 2015, updated 2016. Gridded Monthly Sea Ice Extent and Concentration, 1850 Onward, Version 1. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi:10.7265/N5833PZ5.

Walsh, J. E., J. S. Stewart, and F. Fetterer. 2019. Benchmark seasonal prediction skill estimates based on regional indices. The Cryosphere. doi:10.5194/tc-13-1073-2019.

The Alfred Wegener Institute (AWI) IceBird Program

Spring arrives in the Arctic

Arctic sea ice extent appears to have reached its maximum extent on March 13, marking the beginning of the sea ice melt season. Since the maximum, sea ice extent has been tracking at record low levels. In the Bering Sea, extent increased through the middle of March after setting record lows—only to drop sharply again.

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 March 2019 was 14.55 million square kilometers (5.62 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for March averaged 14.55 million square kilometers (5.62 million square miles), tying with 2011 for the seventh lowest extent in the 40-year satellite record. This is 880,000 square kilometers (340,000 square miles) below the 1981 to 2010 average and 260,000 square kilometers (100,400 square miles) above the lowest March average, which occurred in 2017.

The Bering Sea, which had been nearly ice free at the beginning of March, saw gains in extent through the middle of the month. However, those gains were short lived as extent dropped sharply during the last week of March. The Bering Sea typically reaches its maximum ice extent in late March or early April. This year, the maximum occurred in late January and was 34.5 percent below the 1981 to 2010 average maximum. These late-March sea ice extent losses in the Bering Sea accelerated the decline of total Arctic sea ice extent. By April 1, Arctic extent was at a record low for that date.

Other signs of spring are emerging. A substantial amount of ice retreated in the Gulf of St. Lawrence and the Sea of Okhotsk, as well as in the Barents Sea. Late in the month, small areas of open water were observed in sea ice fields from the University of Bremen, particularly near the shores of the Laptev and Kara Seas, the Sea of Okhotsk, and off of northwestern Alaska.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of April 2, 2019, along with daily ice extent data for four previous years and the record low year. 2018 to 2019 is shown in blue, 2017 to 2018 in green, 2016 to 2017 in orange, 2015 to 2016 in brown, 2014 to 2015 in purple, and 2011 to 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 2a. The graph above shows Arctic sea ice extent as of April 2, 2019, along with daily ice extent data for four previous years and the record low year. 2018 to 2019 is shown in blue, 2017 to 2018 in green, 2016 to 2017 in orange, 2015 to 2016 in brown, 2014 to 2015 in purple, and 2011 to 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 XXXmonthXX 20XX. 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 2b. This plot shows the departure from average air temperature in the Arctic at the 925 hPa level, in degrees Celsius, for March 2019. 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

Overall, Arctic weather in March featured low pressure and above average temperatures. Two low pressure centers at sea level, one over the Bering Sea and the other over the Barents Sea, dominated the atmospheric circulation pattern. Low pressure over the Barents Sea brought cloudy and cool conditions to the immediate region, but also funneled warm air into the central Arctic Ocean. Air temperatures at the 925 mb level (about 2500 feet above sea level) were above average over most of the Arctic region, with the exception in the Atlantic sector of the Arctic Ocean. Temperatures were far above average, locally exceeding 10  degrees Celsius (18 degrees Fahrenheit), over the Beaufort Sea, northeast Alaska, and northwest Canada.

The pattern of overall low pressure across the Arctic in March was manifested as a persistent positive phase of the Arctic Oscillation (AO), a pattern that started during the second week of February. A positive AO in winter has in the past favored low September ice extent. This is in part due to a wind pattern tending to advect older, thicker ice out of the Arctic through the Fram Strait. The wind pattern associated with the positive AO also tends to pull ice away from the Siberian coast, resulting in thinner ice in the region that readily melts out during summer. However, with the overall thinning of the Arctic ice cover, the relationship between winter AO phase and September sea ice extent is not as clear as it used to be.

March 2019 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 March ice extent for 1979 to 2019 shows a decline of 2.7 percent per decade.

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

The net change in sea ice extent between the beginning and end of March was small, which is typical for the month. Sea ice extent increased during the first part of the month to the annual maximum on March 13 and then declined through the remainder of the month.

The 1979 to 2019 linear rate of decline for March ice extent is 41,700 square kilometers (16,100 square miles) per year, or 2.7 percent per decade relative to the 1981 to 2010 average.

Winter recap

Figure 4. This plot shows average sea level pressure in the Arctic in millibars (hPa) from December 1, 2018 to March 31, 2019. 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

Figure 4. This plot shows average sea level pressure in the Arctic in millibars (hPa) from December 1, 2018 to March 31, 2019. 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

Moderation marked the 2018 to 2019 winter. Air temperatures at the 925 mb level were average to slightly above average over most of the Arctic Ocean, with only the southern Beaufort Sea being especially warm with temperatures 5 degrees Celsius (9 degrees Fahrenheit) higher than average.

Below average pressures at sea level dominated over the Bering Sea and much of the Eurasian side of the Arctic Ocean (Figure 4). Circulation patterns, however, were not especially unusual and there were no pronounced short-term heat waves of the type observed in recent winters. For much of the Arctic, sea ice extent was near average through most of the winter. As noted in a previous post, the most compelling feature of the winter was the substantial ice loss during February and early March in the Bering Sea, leading to nearly ice-free conditions.

Snow on sea ice

This graph shows the annual volume of snow on sea ice from 1981 to 2016 based on reanalysis fields from NASA Modern-Era Retrospective analysis for Research and Applications (MERRA-2) (blue) and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-1 (green).

Figure 5a. This graph shows the annual volume of snow on sea ice from 1981 to 2016 based on reanalysis fields from NASA Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2) in blue and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Intermin (ERA-I) in green.

Credit: J. Stroeve, NSIDC
High-resolution image

Figure 5b. The top map of the Arctic shows April trends in snow depth (in centimeters/year) from 1981 to 2016 based on NASA Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2). The bottom map of the Arctic shows April trends in snow depth (in centimeters/year) from 1981 to 2016 based on the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim (ERA-I). The total volume of accumulation is measured from August through July, starting in the 1980 to 1981 winter. ||Credit: Stroeve et al., 2019 Journal of Geophysical Research-Oceans| High-resolution image

Figure 5b. The top map of the Arctic shows April trends in snow depth (in centimeters/year) from 1981 to 2016 based on NASA Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2). The bottom map of the Arctic shows April trends in snow depth (in centimeters/year) from 1981 to 2016 based on the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim (ERA-I). The total volume of accumulation is measured from August through July, starting in the 1980 to 1981 winter.

Credit: Stroeve et al., 2019, Journal of Geophysical Research-Oceans
High-resolution image

With a general trend toward later sea ice formation in autumn and winter and earlier melt in spring and summer, the time period for snow accumulation on the sea ice is changing. However, snow on sea ice is something that satellites do not measure well. As a result, several different approaches have been used to assess snow on sea ice, ranging from using atmospheric reanalysis precipitation forecasts and applying simple temperature thresholds to simulating physical processes impacting snow on sea ice (e.g., wind redistribution, melt, snow compaction) using sophisticated models. A new model (SnowModel) was recently developed for sea ice applications by colleagues at Colorado State University, and is now providing daily snow depth and density estimates from 1980 onwards. A key challenge is that different atmospheric reanalyses, which are used as input to the model, depict different amounts of precipitation. However, regardless of which reanalysis is used, from newer systems such as the NASA Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2) to older systems, such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim (ERA-I), the increasing open water season has reduced the amount of annual snow being accumulated on the sea ice (Figure 5a and 5b). However, there is a lot of spatial variability in trends. There are trends toward shallower April snow depth over the coastal seas and trends toward deeper snow  over the central Arctic Ocean. Snow on sea ice plays several important roles such as influencing rates of thermodynamic ice growth each winter, melt pond development in summer, and melt water input to the upper ocean. Snow on sea ice also has important biological consequences by changing the amount of sunlight able to penetrate the ice.

Antarctic autumn—slow rise

As noted in last month’s post, Antarctica’s annual minimum extent occurred on March 1, the seventh lowest in the satellite record. Since the minimum, ice extent has increased at a slower-than-average pace, remaining well below the inter-decile (10 to 90 percent) range of past early autumn extents. Sea ice growth during March 2019 has been greatest in the central Ross Sea and northeastern Weddell Seas, with significant ice retreat continuing in the southern Bellingshausen Sea. In keeping with the relatively slow ice growth, air temperatures at the 925 mb level have been 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above the 1981 to 2010 average along much of the Antarctica coast from Wilkes Land eastward to the Ross, Amundsen, Bellingshausen, and Peninsula regions. Temperatures along the Dronning Maud Land coast have been 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) below average. The atmospheric circulation at sea level has been characterized by three regions of higher than average pressure interspersed with areas of lower than average pressure, termed a wave-3 pattern by climate scientists. In particular, low pressure in the Amundsen Sea area and high pressure in the Drake Passage (between South American and the Antarctic Peninsula) produced strong winds from the northwest along the southern Peninsula, driving sea ice retreat there while other regions generally saw growth in sea ice extent.

Further reading

Stroeve, J., G. E. Liston, S. Buzzard, A. Barrett, M. Tschudi, M. Tsamados and J. S. Stewart. 2019. A lagrangian snow-evolution system for sea ice applications. Journal Geophysical Research-Oceans, submitted.

Liston, G. E., C. Polashenski, A. Roesel, P. Itkin, J. King, I. Merkouriadi and J. Haapala. 2018. A distributed snow-evolution model for sea-ice applications (SnowModel). Journal Geophysical Research-Oceans. doi.org/10.1002/2017JC013706.

Arctic sea ice maximum ties for seventh lowest in satellite record

Arctic sea ice appears to have reached its annual maximum extent on March 13, tying with 2007 for seventh lowest in the 40-year satellite record. The 2019 maximum sea ice extent is the highest since 2014. NSIDC will post a detailed analysis of the 2018 to 2019 winter sea ice conditions in our regular monthly post in early April.

Overview of conditions

Figure 1. Arctic sea ice extent for March 13, 2019 was 14.78 million square kilometers (5.71 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 March 13, 2019 was 14.78 million square kilometers (5.71 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 March 13, 2019, Arctic sea ice likely reached its maximum extent for the year, at 14.78 million square kilometers (5.71 million square miles), the seventh lowest in the 40-year satellite record, tying with 2007. This year’s maximum extent is 860,000 square kilometers (332,000 square miles) below the 1981 to 2010 average maximum of 15.64 million square kilometers (6.04 million square miles) and 370,000 square kilometers (143,000 square miles) above the lowest maximum of 14.41 million square kilometers (5.56 million square miles) set on March 7, 2017. Prior to 2019, the four lowest maximum extents occurred from 2015 to 2018.

The date of the maximum this year, March 13, was very close to the 1981 to 2010 median date of March 12.

Table 1. Ten lowest maximum Arctic sea ice extents (satellite record, 1979 to present)

Rank Year In millions of square kilometers In millions of square miles Date
1 2017 14.41 5.56 March 7
2 2018 14.48 5.59 March 17
3 2016
2015
14.51
14.52
5.60
5.61
March 23
February 25
5 2011
2006
14.67
14.68
5.66
5.67
March 9
March 12
7 2007
2019
14.77
14.78
5.70
5.71
March 12
March 13
9 2005
2014
14.95
14.96
5.77
5.78
March 12
March 21

A recent paper (Meier and Stewart, 2019) describes the level of accuracy in NSIDC ice extent estimates, with the aim of improving annual minimum and maximum ranking of extents and to determine which years are close enough to be considered tied. For the Arctic maximum, which typically occurs in March, the uncertainty range is ~34,000 square kilometers (13,000 square miles), meaning that extents within this range must be considered effectively equal. The 2019 maximum extent is only 10,000 square kilometers (3,900 square miles) higher than the 2007 maximum, which is within this uncertainty range. Thus, we designate the 2007 and 2019 maximum extents as equal. As is shown in Table 1, other years have also been ascribed tied rankings. NSIDC scientists will rank future maximums and minimums using these criteria.

Final analysis pending

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

Further reading

Meier, W. N., and J. S. Stewart. 2019. Assessing uncertainties in sea ice extent climate indicators. Environmental Research Letters, 14, 035005. doi:10.1088/1748-9326/aaf52c.