2016 ties with 2007 for second lowest Arctic sea ice minimum

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

Please note that this is a preliminary announcement. Changing winds or late-season melt could still reduce the Arctic ice extent, as happened in 2005 and 2010. NSIDC scientists will release a full analysis of the Arctic melt season, and discuss the Antarctic winter sea ice growth, in early October.

Overview of conditions

Figure 1. Arctic sea ice extent for September 10, 2016 was 4.14 million square kilometers (1.60 million square miles). The orange line shows the 1981 to 2010 median extent for that day.

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

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

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

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

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

Conditions in context

Figure 2a. The graph shows Arctic sea ice extent as of September 12, 2016, along with daily ice extent data for four other record low years. 2016 is shown in blue, 2015 in green, 2012 in orange, 2011 in brown, and 2007 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph shows Arctic sea ice extent as of September 12, 2016, along with daily ice extent data for four other record low years. 2016 is shown in blue, 2015 in green, 2012 in orange, 2011 in brown, and 2007 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

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

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

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

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

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

Ice loss primarily in the northern Chukchi Sea

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

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

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

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

 

Second opinion

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

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

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

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

Previous minimum Arctic sea ice extents

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

Ten lowest minimum Arctic sea ice extents (1981 to 2010 average)

Table 2.  Ten lowest minimum Arctic sea ice extents (1981 to 2010 average)
 RANK  YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
1 2012 3.39 1.31 Sept. 17
2

 

2016

2007

4.14

4.15

1.60

1.60

Sept. 10

Sept. 18

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

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

 

 

 

 

 

 

Arctic sea ice nears its minimum extent for the year

Throughout August, Arctic sea ice extent continued to track two or more standard deviations below the long-term average. The month saw two very strong storms enter the central Arctic Ocean from along the Siberian coast. In the Antarctic, ice extent remained near average.

Overview of conditions

sea ice extent map

Figure 1. Arctic sea ice extent for August 2016 was 5.60 million square kilometers (2.16 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

Average sea ice extent for August 2016 was 5.60 million square kilometers (2.16 million square miles), the fourth lowest August extent in the satellite record. This is 1.03 million square kilometers below the 1981 to 2010 average for the month and 890,000 square kilometers (344,000 square miles) above the record low for August set in 2012. As of September 5, sea ice extent remains below average everywhere except for a small area within the Laptev Sea. Ice extent is especially low in the Beaufort Sea and in the East Siberian Sea. With about two weeks of seasonal melt yet to go, it is unlikely that a new record low will be reached. However, since August 26, total sea ice extent is already lower than at the same time in 2007 and is currently tracking as the second lowest daily extent on record. In addition, during the first five days of September the ice cover has retreated an additional 288,000 square kilometers (111,000 square miles) as the tongue of sea ice in the Chukchi Sea has started to disintegrate.

Conditions in context

sea ice extent graph

Figure 2a. The graph above shows Arctic sea ice extent as of September 5, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

ice concentration map

Figure 2b. The map shows Arctic sea ice concentration from the AMSR2 satellite instrument for September 5, 2016. Light blues and greens in ocean areas indicate areas of low ice concentration. The grey circle at the North Pole indicates where the satellite does not collect data, due to its orbit.

Credit: National Snow and Ice Data Center/University of Bremen
High-resolution image

The average ice loss rate through August was 75,000 square kilometers per day (29,000 square miles), compared to the long-term 1981 to 2010 average of 57,300 square kilometers per day (22,100 square miles per day), and a rate of 89,500 square kilometers per day for 2012 (34,500 square miles per day). Total ice extent loss in August was 2.34 million square kilometers (904,000 square miles).

Air temperatures at the 925 hPa level were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below average for a large area stretching from the northern Kara Sea, through the Laptev Sea, and into north-central Eurasia. Temperatures elsewhere over the Arctic Ocean were near average. Reflecting the generally stormy pattern through the month, sea level pressures were well below average (as much as 10 hPa) over the central and eastern Arctic Ocean. Two very strong cyclones entered the central Arctic Ocean in August from along the Siberian coast, bringing strong winds. On August 16, the central pressure of the first cyclone dropped to 968 hPa, nearly rivaling the storm in early August 2012 that attained a minimum central pressure of 966 hPa. On 22 August, the second storm started moving to the central Arctic Ocean along a similar track, and on August 23, attained a central pressure of 970 hPa.

Past studies have shown that stormy summers tend to end up with more sea ice at the end of the melt season than summers with high pressure over the central Arctic Ocean, primarily because stormy summers are both fairly cool and the wind pattern tends to spread the ice out. However, the impact of strong individual storms may be different—the 2012 event appears to have temporarily boosted ice loss by breaking up the ice cover, with the wave action tending to mix warmer waters from below to hasten melt. It may also be that, as the ice cover thins, its response to storms is changing.

It indeed appears that the August 2016 storms helped to break up the ice and spread it out, contributing to the development of several large embayments and polynyas. Some of this ice divergence likely led to fragmented ice being transported into warmer ocean waters, hastening melt. Whether warmer waters from below were mixed upwards to hasten melt remains to be determined, but as discussed below, these storms were associated with very high wave heights.

August 2016 compared to previous years

sea ice trend graph

Figure 3. Monthly August ice extent for 1979 to 2016 shows a decline of 10.4 percent per decade.

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

Arctic sea ice extent averaged for August 2016 was the fourth lowest in the satellite data record. Through 2016, the linear rate of decline for August is 10.4 percent per decade.

Cyclones, ocean wave heights, and ice retreat

wave height maps

Figure 4. This series of plots shows significant wave height (in meters, indicated by color scale) in the western Arctic Ocean during the 2016 Arctic cyclone, from August 14 to August 16, 2016, as predicted by a numerical wave model (WAVEWATCH III), run at the Naval Research Laboratory (NRL). The solid red lines correspond to the analysis ice concentrations (25 percent, 50 percent and 75 percent) used as input for the wave model. White arrows indicate wave direction. This hindcast uses two time-varying inputs: 10-meter wind vectors from the atmospheric model NAVGEM (Navy Global Environmental Model, Hogan et al. 2014) run at the Fleet Numerical Meteorology and Oceanography Center (FNMOC), and analyses of ice concentrations (also produced at FNMOC) from passive microwave radiometer data (SSM/I). The wave model is run on a polar stereographic grid with a resolution of approximately 18 kilometers.

Credit: Erick Rogers, Naval Research Laboratory
High-resolution image

Large waves are common at high latitudes; 10-meter wave heights (33 feet) are not unusual for the Nordic Seas, and 15-meter wave heights (49 feet) can occur in the high latitudes of the Southern Ocean. However, large waves are a relatively new feature of the western Arctic Ocean. The height of waves is in part determined by surface wind speed, as well as the fetch (distance over open water that the wind can travel) and the duration of a wind event. A moderate sea ice cover damps ocean waves by absorbing and dispersing the wave energy through jostling of the ice floes against one another. A dense ice pack cover acts as a shield between the ocean and the surface wind, preventing wave formation.

In the latter half of the twentieth century, 4 to 6 meter waves (13 to 20 feet) rarely occurred in the western Arctic Ocean, but with more open water they have become more frequent, especially when strong storms enter the Arctic Ocean in late summer or early autumn. During the first of the two August cyclones discussed above, waves up to 5.9 meters (19 feet) were predicted. This occurred during the early part of the cyclone’s lifecycle (1800 UTC August 14), in the eastern Kara Sea. Further east, north of the New Siberian Islands, wave heights were estimated as high as 4.3 meters (14 feet) late on August 15. In this region, the waves were directly incident on the ice edge. In response, the ice edge retreated following the 4.3 meter waves on August 15.

Northwest Passage update

Figure 5. The time series shows total sea ice area for selected years and the 1981-2010 average within the northern route of the Northwest Passage. The cyan line shows 2016 and other colors show ice conditions in different years. Data are from the Canadian Ice Service.

Credit: Stephen Howell, Environment and Climate Change Canada
High-resolution image

The Northwest Passage refers to the fabled shortcut between the Atlantic and Pacific through the Canadian Archipelago. However, it is not one route. There is a northern, deep-water route through the Parry Channel, entered from the west through the M’Clure Strait and a shallower southern route, known as Amundsen’s route. Sea ice in the Parry Channel route has shown a sharp decline since the middle of July, but the channel is still not entirely ice free. Considerable ice remains in the western (M’Clure Strait) region and there are lesser amounts in the eastern regions. This is mostly (~80 percent) multiyear ice. Low ice years in the Parry Channel are typically the result of early summer breakup associated with high sea level pressure over the Beaufort Sea and Canada Basin that displace the Arctic Ocean pack ice away from the western entrance. Conversely, low sea level pressure anomalies over the Beaufort Sea and Canada Basin keep the Arctic Ocean pack ice up against the western entrance. This has been the case for much of the 2016 melt season. The southern (Amundsen’s) route is open but it is still uncertain whether the northern route will open in the coming weeks.

Even during mild ice years, thick multiyear ice is typically advected into these routes during the summer months. Multiyear ice is a significant obstacle for ships. Nevertheless, taking advantage of mild sea ice conditions, the 68,000-ton Crystal Serenity set sail from Anchorage, Alaska on August 16 for its 32-day journey through the Northwest Passage via Amundsen’s route. This is the largest ship thus far to navigate the Northwest Passage and is accompanied by an icebreaker ship and two helicopters. The ship sailed through the Northwest Passage in less than three weeks—52 times faster than Amundsen’s nearly three-year voyage.

On the other side of the Arctic, the Northern Sea Route appears mostly ice free.

Further reading

Collins, C. O., W. E. Rogers, A. Marchenko and A. V. Babanin. 2015. In situ measurements of an energetic wave event in the Arctic marginal ice zone. Geophysical Research Letters, 42, doi:10.1002/2015GL063063.

Haas, C., and S. E. L. Howell. 2015. Ice thickness in the Northwest Passage. Geophysical Research Letters, 42, 7673–7680, doi:10.1002/2015GL065704.

Hogan, T., et al. 2014. The Navy Global Environmental Model, Oceanography, 27(3), 116-125.

Howell, S. E. L., T. Wohlleben, M. Dabboor, C. Derksen, A. Komarov and L. Pizzolato. 2013. Recent changes in the exchange of sea ice between the Arctic Ocean and the Canadian Arctic Archipelago. Journal of Geophysical Research, 118, 3595–3607, doi:10.1002/jgrc.20265.

Thomson, J., and W. E. Rogers. 2014. Swell and sea in the emerging Arctic Ocean, Geophysical Research Letters 41, doi:10.1002/2014GL059983.

Thomson, J. et al. 2016. Emerging trends in the sea state of the Beaufort and Chukchi seas, Ocean Modelling 105, doi:10.1016/j.ocemod.2016.02.009.

Late summer in the Arctic, sea ice melt continues

As of August 14, Arctic sea ice extent is tracking third lowest in the satellite record. The southern route through the Northwest Passage appears to be largely free of ice. Despite a rather diffuse ice cover in the Chukchi Sea, it is unlikely that Arctic sea ice extent this September will fall below the record minimum set in 2012.

Overview of conditions

Figure 1. Arctic sea ice extent for August 14, 2016 was 5.61 million square kilometers (2.17 million square miles). The orange line shows the 1981 to 2010 median extent for that day

Figure 1. Arctic sea ice extent for August 14, 2016 was 5.61 million square kilometers (2.17 million square miles). The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

As of August 14, Arctic sea ice extent was 5.61 million square kilometers (2.17 million square miles). This is the third lowest extent in the satellite record for this date and slightly below the two standard deviation range. So far this month the rate of loss has been faster than average and has declined at a rate similar to that observed for 2012.

Ice loss has progressed quite rapidly in the Beaufort and Chukchi seas, where broken up ice floes are starting to melt away. However, large, thick multiyear ice floes persist in several areas; it remains to be seen if they will survive the melt season. A wedge of open water has also penetrated northward from the East Siberian Sea, yet ice remains extensive in the Laptev Sea, blocking the Northern Sea Route. Ice extent continues to be low in the Kara, Barents, and East Greenland seas. The southern (Amundsen’s) route through the Northwest Passage appears open in Advanced Scanning Microwave Radiometer 2 (AMSR2) data. However, data in visible wavelengths from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) instrument still show some ice.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 14, 2016, along with daily ice extent data for four previous years.

Figure 2. The graph above shows Arctic sea ice extent as of August 14, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

Ice loss from August 1 to 14 was faster than average, at 87,400 square kilometers (33,800 square miles) per day, and near the rates observed in 2012. Nevertheless, as has been the pattern this summer, atmospheric conditions through the first half of August have been generally cloudy and cool. Air temperatures at the 925 hPa level were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below the 1981 to 2010 long-term average over the eastern part of the Arctic Ocean and near average elsewhere. The cool and cloudy conditions reflect a pattern of low atmospheric pressure over the Laptev and Kara seas.

As of August 16, a strong storm (central pressure of 968 hPa) was located over the Central Arctic Ocean at about 85 degrees North, near the dateline. The extent to which this strong storm will affect sea ice conditions remains to be seen.

Ocean heat continues ice melt

Figure 3. The map shows average ocean sea surface temperature (SST) and sea ice concentration for August 7, 2016. SST is measured by satellites using thermal emission sensors, which produce a global data adjusted by comparison with ship and buoy data. Sea ice concentration is derived from the NSIDC sea ice concentration near-real-time data. Also shown are drifting buoy temperatures at the ocean surface (colored circles); gray circles indicate that temperature data from the buoys are not available. ||Credit: M. Steele, Polar Science Center/University of Washington| High-resolution image

Figure 3. The map shows average ocean sea surface temperature (SST) and sea ice concentration for August 7, 2016. SST is measured by satellites using thermal emission sensors, which produce global data adjusted after comparison with ship and buoy data. Sea ice concentration is derived from NSIDC sea ice concentration near-real-time data. Also shown are drifting buoy temperatures at the ocean surface (colored circles); gray circles indicate that temperature data from the buoys are not available.

Credit: M. Steele, Polar Science Center/University of Washington
High-resolution image

The Arctic atmosphere is cooling now as the sun dips lower in the sky. However, sea ice loss will continue throughout August due primarily to melt from the ocean heat that has accumulated over the summer. Early ice retreat has allowed the ocean to warm, both from absorption of the sun’s energy and from northward-flowing warm water in the Chukchi Sea to the west of Alaska and in the Barents Sea to the north of Norway. Unusually strong ocean warming occurred in northern Baffin Bay (between northern Canada and Greenland), the Beaufort Sea (north of northwestern Canada and Alaska), the East Siberian Sea (north of far eastern Siberia), and the Barents and Kara seas (north of western Eurasia).

What is quite unusual this year is the early ice retreat and resulting ocean warming in the western Beaufort Sea and in the western East Siberian Sea. The extent of warming to the north of these two seas is also unusual, as well as the extent of this warming to the north. These two areas typically melt out later in the season, when atmospheric heating rates have declined from their mid-summer peak. Thus the exposed ocean warms, but not all that much. This pattern was true during the record-setting year of 2012, when by the end of summer, these areas were substantially cooler than surrounding seas that had melted out earlier.

This year, however, the melt out was early and extensive enough that the ocean has already warmed substantially in these two areas. More sea ice retreat is probable in the western Beaufort and East Siberian seas as well as areas in the coming weeks. But what about the ocean’s response? Some warm water might move northward via ocean currents and contribute to ice melt. However, further dramatic ocean surface warming is unlikely, given that the atmosphere is already cooling, especially in far northern latitudes.

Ice loss rates indicate little chance for a record low this year

Figure 4. The graph above shows projections of ice extent from August 14 through September 30 based on previous years’ observed retreat rates appended to the August 14, 2016 ice extent.

Figure 4. The graph above shows projections of ice extent from August 14 through September 30 based on previous years’ observed retreat rates appended to the August 14, 2016 ice extent.

Credit: W. Meier/NASA GSFC
High-resolution image

While there are still three to four weeks to go in the melt season, a new record low this September is highly unlikely. A simple projection method developed by Walt Meier at the NASA Goddard Space Flight Center uses daily ice loss rates from previous years to estimate possible trajectories of ice extent through the rest of the melt season.

This approach yields a range of minimum values based on how sea ice loss progressed in previous years. By selecting from an average of multiple years, or using loss rates from a specific previous year, the method yields an estimate of the likely range of the minimum sea ice extent. As of August 14, using daily ice loss rates based on the 2006 to 2015 average yields an average projected 2016 minimum extent of 4.33 million square kilometers (1.67 million square miles). Using the slowest (recent) August to September decline, which occurred in 2006, yields a 2016 minimum of 4.76 million square kilometers (1.84 million square miles). Using the fastest rate of decline, from 2012, yields a 2016 minimum extent of 4.06 million square kilometers (1.57 million square miles). These two years bracket a reasonable range of expected 2016 minima. It is possible that this year will have decline rates that fall outside the range of previous years. However, this approach indicates that it is very unlikely that 2016 will have a minimum below 2012’s value of 3.39 million square kilometers (1.31 million square miles). A projection from August 1 was submitted to the Sea Ice Outlook.

Further reading

Lindsay, R.W. 1998. Temporal variability of the energy balance of thick Arctic pack ice, Journal of Climate, doi:10.1175/15200442(1998)011<0313:TVOTEB>2.0.CO;2.

Steele, M. and W. Ermold. 2015. Loitering of the retreating sea ice edge in the Arctic seas, Journal of Geophysical Research, doi:10.1002/2015JC011182.

Steele, M., J. Zhang, and W. Ermold. 2010. Mechanisms of summertime upper Arctic Ocean warming and the effect on sea ice melt, Journal of Geophysical Research, doi:10.1029/2009JC005849.

A cool and stormy Arctic in July

An extensive area of lower than average temperatures in the Central Arctic and the Siberian coast, attended by persistent low pressure systems in the same region, led to slightly slower than average sea ice decline through the month. The stormy pattern contributed to a dispersed and ragged western Arctic ice pack for July, with several polynyas beginning to form late in the month. A new record low September ice extent now appears to be unlikely.

Overview of conditions

Figure 1. Arctic sea ice extent for July 2016 was 8.13 million square kilometers (3.14 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for July 2016 averaged 8.13 million square kilometers (3.14 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

Arctic sea ice extent for July averaged 8.13 million square kilometers (3.14 million square miles), the third lowest July extent in the satellite record. This makes July only the second month so far this year that did not have a record low extent. July’s extent is 190,000 square kilometers (73,000 square miles) above the previous record low set in 2011, and 1.65 million square kilometers (637,000 square miles) below the 1981 to 2010 long-term average.

Ice extent continues to be far below average in the Kara and Barents seas, as it has been throughout the winter and spring. Extent also remains well below average in the Beaufort Sea, but in the Laptev and East Siberian seas, sea ice extent is near average.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of August 1, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of August 1, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

Figure 2b. The plot above shows July 2016 Arctic air temperature anomalies at the 925 hPa level in degrees Celsius and sea level pressure anomalies. Yellows and reds indicate higher than average temperatures and pressure; blues and purples indicate lower than average temperatures and pressure.

Figure 2b. The plot above shows July 2016 Arctic air temperature anomalies at the 925 hPa level in degrees Celsius and sea level pressure anomalies. Yellows and reds indicate higher than average temperatures and pressure; blues and purples indicate lower than average temperatures and pressure.

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

The rate of ice loss during July 2016 was slightly below average at 83,800 square kilometers (32,400 square miles) per day. The 1981 to 2010 average rate of ice loss for July is 86,800 square kilometers (33,500 square miles) per day.

Warm conditions with temperatures at the 925 hPa level of 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) above average graced the northernmost coasts of Alaska, Canada, and Greenland, but the thick sea ice that is typical of this region is unlikely to melt out. Very warm conditions continued in the Kara and Barents seas, with temperatures as much as 3 to 6 degrees Celsius (5 to 11 degrees Fahrenheit) above average, consistent with the retreat of the ice cover to the northern edge of the Svalbard, Franz Josef, and New Siberian Islands. However, the main feature of the climate conditions for the month was a large area of below-average pressure centered over the Laptev Sea, and associated cooler than average conditions in the same area (1 to 4 degrees Celsius or 2 to 7 degrees Fahrenheit). This continues the pattern seen in June, with conditions unfavorable to pronounced sea ice retreat: cloudy and cool, with winds that tend to disperse the ice and increase its extent, rather than compact it.

July 2016 compared to previous years

Figure 3. Monthly July ice extent for 1979 to 2016 shows a decline of 7.3 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly July ice extent for 1979 to 2016 shows a decline of 7.3 percent per decade.

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

Through 2016, the rate of decline for the month of July is 72,700 square kilometers 28,070 square miles) per year, or 7.3 percent per decade. July extent remained above 2011 and 2012 levels throughout the month, but it was below the 2007 extent for the first half of the month.

A shift in pressure

Figure 4. These graphs show sea level pressure anomalies or differences from average sea level pressure in the Northern Hemisphere for April, May, June, and July 2016.

Figure 4. These graphs show sea level pressure anomalies or differences from average sea level pressure in the Northern Hemisphere for April, May, June, and July 2016.

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

Beginning in June there was a significant change in the atmospheric circulation over the Arctic. May was characterized by high pressure over the Arctic Ocean which had persisted since the beginning of the year. However, in June the pattern shifted to lower than average pressure. This brought clouds and fairly low temperatures to the region, slowing ice loss. The change in circulation also shifted the pattern of ice motion, slowing the earlier movement of ice away from the coast in the Beaufort Sea (as depicted in our May 3rd post).

This pattern shift is associated with the development of a large and persistent area of moderate high pressure over the northeastern Pacific (south of Alaska) that formed beginning in mid-May. This may be related to an ongoing shift in the Pacific Decadal Oscillation over spring and early summer this year.

Sea ice dances to the changing wind

Figure 5a. These graphs Arctic sea ice motion for May 2 to 8, 2016 (top) and July 25 to 31, 2016 (bottom).

Figure 5a. These graphs show Arctic sea ice motion for May 2 to 8, 2016 (top) and July 25 to 31, 2016 (bottom).

Credit: NSIDC/University of Colorado, M. Tschudi, C. Fowler, J. Maslanik, W. Meier
High-resolution image

Figure 5b. This sea ice concentration image from the Advanced Microwave Scanning Radiometer 2 (AMSR2) shows dispersed sea ice and small polynyas in the Beaufort and East Siberian season July 27, 2016.

Figure 5b. This sea ice concentration image from the Advanced Microwave Scanning Radiometer 2 (AMSR2) shows dispersed sea ice and small polynyas in the Beaufort and East Siberian seas on July 27, 2016.

Credit: University of Bremen
High-resolution image

The shift in air pressure pattern also resulted in a change in sea ice drift directions in the Arctic. Early in the year, sea ice drift had a strong clockwise pattern (Figure 5a, top). However, July conditions greatly reduced sea ice drift speed in the Beaufort Sea and produced a counterclockwise drift pattern in the Laptev Sea (Figure 5a, bottom).

Persistent low pressure and repeated cyclonic storms in the Siberian side of the Arctic tended to disperse the pack and move it away from the coast. By late July, several regions of thin pack and small polynyas were beginning to open in these areas (Figure 5b).

The ice of our forefathers

Figure 6. These graphs show a best estimate of ice extent and sea ice departure from average for the period 1850 to 2013. The top figure shows winter and summer.

Figure 6. These graphs show a best estimate of ice extent and sea ice departure from average for the period 1850 to 2013. The top figure shows winter and summer.

Credit: NOAA at NSIDC
High-resolution image

Earlier this month, NOAA at NSIDC published a new compilation of Arctic sea ice extent using a variety of historical sources, including whaling ship reports and several historical ice chart series from Alaska, the Russian Arctic, Canada, and Denmark. The compilation provides a synthesized mid-monthly estimate extending back to 1850. The study concludes that the current downward trend in sea ice has no precedent in duration or scale of ice loss since 1850. With the exception of the Bering Sea, none of the areas have seen sea ice extents as low as in the past decade. Historical periods that show a decrease in summertime sea ice extent in the Arctic, such as the late 1930’s and 1940’s, are smaller in magnitude than the current downward-trending period.

Further reading

Walsh, J. E., F. Fetterer, J. S. Stewart, and W. L. Chapman. 2016. A database for depicting Arctic sea ice variations back to 1850. Geographical Review. doi: 10.1111/j.1931-0846.2016.12195.x.

Despite a stormy Arctic, low ice continues

Through the first half of July, Arctic sea ice extent continued tracking close to levels in 2012, the summer that ended with the lowest September extent in the satellite record. The stormy weather pattern that characterized June has persisted into July. Nevertheless, sea ice melt began earlier than average over most of the Arctic Ocean.

Overview of conditions

sea ice extent map

Figure 1. Arctic sea ice extent for July 18, 2016 was 7.82 million square kilometers (3.02 million square miles). The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

As of July 18, Arctic sea ice extent was 7.82 million square kilometers (3.02 million square miles). This is just below the two standard deviation value for the date, and just above the level observed on the same date in 2012, the year that ended up having the lowest September extent in the satellite record. Throughout the month, extent has closely tracked both the two standard deviation and 2012 levels.

Ice extent in the first half of July was well below average in the Kara and Barents seas, as it has been throughout the winter and spring. Extent is also below average in the Beaufort and Chukchi seas, between the East Siberian and Laptev seas by the New Siberian Islands, and along the southeast coast of Greenland. In the last several days, polynyas have formed in the northern Beaufort Sea. Compared to 2012 at this time of year, there is more ice in the southern Beaufort Sea, Baffin Bay, the Laptev Sea, and north of the New Siberian islands in the East Siberian Sea. There is less ice this year in the East Greenland Sea, extending through the Barents and Kara seas, and in the western Beaufort and Chukchi seas.

Conditions in context

extent trend graph

Figure 2. The graph above shows Arctic sea ice extent as of July 18, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

Arctic surface weather map

Figure 3. This surface weather map from the Canadian Meteorological Center for 0600Z, July 6, 2016, shows a strong low pressure system (extratropical cyclone) over the Eurasian side of the central Arctic Ocean. The central pressure of the cyclone dropped to as low as 979 hPa, a very strong storm for this part of the Arctic.

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

air temperature plot

Figure 4. Arctic air temperatures at the 925 hPa level, as compared to the long-term (1981 to 2010) average. The area of below average temperatures centered over the East Siberian Sea contrasts sharply with unusually warm conditions over the Barents and Kara seas, the Canadian Arctic Archipelago and northern Alaska.

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

The average rate of ice loss through July 18 was 89,500 square kilometers (34,600 square miles) per day, which is close to the long-term average (1981 through 2010) rate of 86,800 square kilometers (33,500 square miles) per day. Recall from our last post that the month of June was characterized by a stormy pattern over the central Arctic Ocean, which likely acted to slow the rate of ice loss. This pattern has persisted into July. However, the rate of decline increased in the first two weeks of the month as very warm conditions spread around the Arctic coasts. Ice loss has slowed in the last few days. A number of low pressure systems, primarily generated over northern Eurasia, have migrated into the central Arctic Ocean, north of the East Siberian Sea. One of these was quite strong, with a central pressure dropping to as low as 979 hPa (Figure 3).

Cyclones found over the central Arctic Ocean in summer tend to be what is termed “cold cored.” Because of these cold-cored systems and their associated pattern of winds, air temperatures at the 925 hPa level for the first half of July have been well below average along and north of the East Siberian Sea. By sharp contrast, strongly above average temperatures have been the rule over the Barents and Kara seas, the Canadian Arctic Archipelago and northern Alaska (Figure 4). Local conditions can be quite variable, and not well captured by conditions at the 925 hPa level. On July 14, Deadhorse, on the North Slope of Alaska on the shores of the Beaufort Sea, saw a record high temperature. The reading of 85° Fahrenheit (through 7 p.m.) broke the record of 83° Fahrenheit set in 1991. It is also also the highest reading on record for any Alaska station within 50 miles of the Arctic Ocean coast north of the Brooks Range.

Early melt onset

melt onset plot

Figure 5. The onset of surface melt, as determined from satellite passive microwave data, was early over most of the Arctic Ocean. An early melt implies an early drop in the surface albedo, which furthers the melt process.

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

Seasonal onset of surface melt was early over most of the Arctic Ocean (Figure 5). This occurred under the high-pressure-dominated weather pattern that was present earlier in the spring. The onset of surface melt can be determined with the same passive microwave data used to determine sea ice extent and concentration. Melt began in late April/early May in the southern Beaufort Sea, which was about 6 weeks (more than 40 days) earlier than average. Melt also began a month earlier than average in the Barents Sea and northern Baffin Bay.

Early onset of melt is important because melt drops the surface albedo, allowing the sea ice and its overlying snow cover to absorb more solar radiation, which accelerates the melt process. Data from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument show many very large, multiyear ice floes in the Beaufort Sea, one of them about 50 miles across. It will be interesting to see if these large multiyear floes melt out this summer. NSIDC will be closely monitoring the situation.

New insights into Antarctic sea ice conditions

Gerald Meehl of the National Center for Atmospheric Research led a new study shedding light on the upward trend in total Antarctic sea ice extent over the period of satellite observations. The overall view from climate models is that Antarctic sea ice extent should have decreased in response to the general warming of climate. This has led some scientists to suggest that the climate models are fundamentally flawed. However, an explanation for the expanding Antarctic sea ice appears to lie in the Interdecadal Pacific Oscillation (IPO), a natural mode of climate variability. The IPO transitioned from a positive to a negative phase in the late 1990s at the same time that the increase in total Antarctic sea ice extent accelerated. The negative IPO brought a cooling of tropical Pacific sea surface temperatures, and deepening of the Amundsen Sea Low near Antarctica. This has contributed to regional circulation changes in the Ross Sea region favoring expansion of the sea ice cover. Meehl’s study also shows that the negative phase of the IPO in coupled global climate models is characterized by patterns similar to the sea-level pressure and 850 hPa wind changes observed in all seasons near Antarctica since 2000, particularly in the Ross Sea region. Additional model experiments show that these atmospheric circulation changes are mainly driven by precipitation and convective heating anomalies related to the IPO in the equatorial eastern Pacific. They conclude that the models are not wrong, but instead can simulate the processes involved with natural climate variability that results in increased Antarctic sea ice, even when global temperatures are rising.

Reference

Meehl, G.A., J.M. Arblaster, C. Bitz, C.T.Y. Chung, and H. Teng. 2016. Antarctic sea ice expansion between 2000-2014 driven by tropical Pacific decadal climate variability. Nature Geoscience, doi:10.1038/NGEO2751.

Extent loss slows, then merges back into fast lane

June set another satellite-era record low for average sea ice extent, despite slower than average rates of ice loss. The slow rate of ice loss reflects the prevailing atmospheric pattern, with low pressure centered over the central Arctic Ocean and lower than average temperatures over the Beaufort Sea.

Overview of conditions

Figure 1. Arctic sea ice extent for June 2016 was 10.60 million square kilometers (4.09 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

Arctic sea ice extent during June 2016 averaged 10.60 million square kilometers (4.09 million square miles), the lowest in the satellite record for the month. So far, March is the only month in 2016 that has not set a new record low for Arctic-wide sea ice extent (March 2016 was second lowest, just above 2015). June extent was 260,000 square kilometers (100,000 square miles) below the previous record set in 2010, and 1.36 million square kilometers (525,000 square miles) below the 1981 to 2010 long-term average.

Sea ice extent remains below average in the Kara and Barents seas, as it has throughout the winter and spring. Despite lower than average temperatures over the Beaufort Sea, sea ice extent there remains below average, and was the second lowest extent for the month of June during the satellite data record.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of July 5, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

Figure 2b. The map of sea level pressure averaged for the month of June 2016 (left) shows low pressure over the central Arctic Ocean. The map of air temperatures at 925 hPa for June 2016 compared to the 1981 to 2010 long-term average (right) shows cool conditions over the Beaufort Sea.

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

The average rate of ice loss during June 2016 was 56,900 square kilometers (22,000 square miles) per day, but was marked by two distinct regimes. First, there was a period of slow loss during June 4 to 14 of only 37,000 square kilometers (14,000 square miles) per day. This was followed by above average rates (74,000 square kilometers, or 29,000 square miles) for the rest of the month. For the month as a whole, the rate of loss was close to average (53,600 square kilometers per day). The slow ice loss during early June was a result of a significant change in the atmospheric circulation. May was characterized by high surface pressure over the Arctic Ocean, a basic pattern that has held since the beginning of the year. However, June saw a marked shift to low pressure over the central Arctic Ocean. This type of pattern is known to inhibit ice loss. A low pressure pattern is associated with more cloud cover, limiting the input of solar energy to the surface, as well as generally below average air temperatures. However, in June 2016, it was only in the Beaufort Sea where air temperatures at the 925 hPa level were distinctly below average (about 2 degrees Celsius below average, or 4 degrees Fahrenheit). The change in circulation also shifted the pattern of ice motion. In general, winds associated with such a low pressure pattern will tend to spread the ice out (that is, cause the ice to diverge).

June 2016 compared to previous years

ice extent trend graph

Figure 3. Monthly June ice extent for 1979 to 2016 shows a decline of 3.7% per decade.

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

Through 2016, the rate of decline for the month of June is 44,600 square kilometers (17,200 square miles) per year, or 3.7 percent per decade. June extent remained below 2012 levels throughout the month, but it was above the 2010 extent for several days. 2010 had the lowest extent for several days during June.

View from above

arctic images

Figure 4. MODIS composite images for June 9, 2016 (top) and June 28, 2016 (bottom) show the seasonal progression of surface melting and darkening of the ice surface.

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

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the NASA Aqua and Terra satellites provide multiple views each day of the Arctic, and in summer the entire region is sunlit. Two mosaics for June 9 and June 28 show the seasonal progression in surface melting and darkening of the sea ice; the blue-green areas where surface ponding is present; and the movement of large sea ice floes in the Beaufort Sea. On June 9, the ponds are most evident in the Laptev Sea off the coast of Siberia; on June 28, the ponds are most evident in the Canadian Archipelago.

 

A quick look at sea ice thickness fields

sea ice thickness plot

Figure 5. Sea ice thickness from April and May 2016 from Operation IceBridge. Image courtesy Nathan Kurtz, NASA Goddard.

Credit: N. Kurtz, NASA Goddard Space Flight Center
High-resolution image

Results from NASA’s Operation IceBridge aircraft missions conducted during late April and early May indicate that ice thicknesses from the Alaskan coast of the Beaufort Sea up to the North Pole were generally in the 2 to 3 meter range (7 to 10 feet), indicative of multiyear ice. However, substantial variations were found along the flight transects with several locations showing an ice thickness of 1.5 meters (5 feet) or less, indicative of first-year ice, while in other locations thicknesses were over 5 meters (16 feet), corresponding to either fairly thick multiyear ice or ridged first-year ice. This substantial variation is representative of a broken up and variegated ice pack with thick multiyear floes interspersed with thinner first-year ice.

The first-year thicknesses were found to be generally thinner than is typical at the end of winter, which is consistent with the usually high temperatures characterizing last winter. Very thin ice (less than 0.5 meters, or 1.6 feet) was found in places near the Alaskan coast, where leads opened up fairly late in the ice growth season. The IceBridge results are generally in agreement with the ice thickness surveys conducted in early April by researchers from York University, and with CryoSat-2 thickness maps discussed in our previous post.

Sea Ice Outlook

Each summer the Sea Ice Prediction Network (SIPN) requests forecasts of the September average sea ice extent. Requests are made in June July and August. This year, thirty contributions to the June Sea Ice Outlook were received, employing a variety of methods, including statistical models, dynamical models, and informal polls. The median prediction for this year’s September sea ice extent is 4.28 million square kilometers (1.65 million square miles), similar to the extent observed in 2007. Dynamical models predict 4.58 million square kilometers (1.77 million square miles), compared to the slightly lower overall median extent prediction of 4.28 million square kilometers (1.65 million square miles) from statistical models. The lowest median extent comes from the heuristic contributions (4.0 million square kilometers, or 1.5 million square miles). Only one forecast points towards a new record low for 2016.

Antarctic sea ice

ice trend plots

Figure 6. Circumpolar Antarctic trends from 1979 to 2014 in the consolidated pack ice (blue), the marginal ice zone (red) and coastal polynyas (green) from the NASA Team sea ice algorithm (left) and the Bootstrap algorithm (right).

Credit: National Snow and Ice Data Center, Stroeve et al.
High-resolution image

Antarctic sea ice extent continues to track at near average levels, in sharp contrast to the previous two winters, which were above average. While the total ice extent in the Antarctic shows a small positive trend, particularly during the cold season, whether or not the total mass of the ice has changed depends on how much of the pack ice consists of consolidated ice, the extent of the marginal ice zone (the outer edge of the ice pack, which is lower in ice concentration), and coastal polynyas (open water areas near the coast). The marginal sea ice zone and the coastal polynyas have important biological implications. These are key regions for phytoplankton productivity and krill abundance that in turn feed Antarctic sea birds and nektonic fauna (things that swim).

A new study looks at how these regions are changing using two sea ice concentration algorithms distributed by NSIDC. While the algorithms give similar trends in the overall sea ice extent, they differ in terms of whether or not the sea ice cover is becoming more compacted (i.e., the consolidated ice pack is increasing in extent) or if the marginal ice zone is expanding (Figure 6). When sea ice is is growing seasonally, both algorithms indicate that it is due to an expansion of the consolidated ice pack, whereas during winter and spring, one measurement method (the NASA Team algorithm) finds the marginal ice zone is also expanding as well, and the other measurement (Bootstrap algorithm) shows no significant trend in the marginal ice. The algorithms also differ in how much of the total ice pack consists of pack ice or the marginal ice, with the NASA Team algorithm having on average twice as large of a marginal ice zone as the Bootstrap algorithm. As well, the NASA Team algorithm is known to underestimate ice concentration in the Antarctic. This highlights the need for further validation of sea ice concentrations derived from passive microwave satellite data.

New Sea Ice Index version

As part of our quality control process, the Sea Ice Index, which supplies sea ice extent and concentration values, has been updated to Version 2. Changes include using the most recently available version of the Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data that provide final sea ice concentration data. The version update also adjusted three procedures in the Sea Ice Index processing routine that affected both the near-real-time data and the final data. These four updates affect different portions of the Sea Ice Index time series. Because of these updates, minor changes in some of the ice extent and area numbers will be seen. However, these changes are almost all quite small and do not alter current conclusions about Arctic or Antarctic sea ice conditions. More information on Version 2 is available in the Sea Ice Index documentation.

Reference

Stroeve, J. C., Jenouvrier, S., Campbell, G. G., Barbraud, C., and Delord, K. 2016, in review. Mapping and assessing variability in the Antarctic Marginal Ice Zone, the pack ice and coastal polynyas. The Cryosphere Discuss., doi:10.5194/tc-2016-26.

 

Satellite data transition complete

As of June 14, 2016, NSIDC has completed the transition to the Defense Meteorological Satellite Program (DMSP) F-18 satellite for sea ice data. Sea Ice Index updates have also resumed.

Sea ice data in Arctic Sea Ice News and Analysis are now based on the F-18 satellite beginning April 1, 2016. Data before April 1 are still from the F-17 satellite or earlier satellites in the series.

For more information on the F-17 satellite issues, see our April 12, 2016 post. On May 6, updates resumed with provisional F-18 data. These data are no longer considered provisional. However, these are near-real-time data and numbers may change when final data are obtained.

For more information on the satellite transition, see the documentation for the Near-Real-Time DMSP SSMIS Daily Polar Gridded Sea Ice Concentrations data set.

Low ice, low snow, both poles

Daily Arctic sea ice extents for May 2016 tracked two to four weeks ahead of levels seen in 2012, which had the lowest September extent in the satellite record. Current sea ice extent numbers are tentative due to the preliminary nature of the DMSP F-18 satellite data, but are supported by other data sources. An unusually early retreat of sea ice in the Beaufort Sea and pulses of warm air entering the Arctic from eastern Siberia and northernmost Europe are in part driving below-average ice conditions. Snow cover in the Northern Hemisphere was the lowest in fifty years for April and the fourth lowest for May. Antarctic sea ice extent grew slowly during the austral autumn and was below average for most of May.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2016 was 12.0 million square kilometers (4.63 million square miles).

Figure 1. Arctic sea ice extent for May 2016 was 12.0 million square kilometers (4.63 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole. Provisional data. Not a Sea Ice Index product.

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

May 2016 set a new record low for the month for the period of satellite observations, at 12.0 million square kilometers (4.63 million square miles), following on previous record lows this year in January, February, and April. May’s average ice extent is 580,000 square kilometers (224,000 square miles) below the previous record low for the month set in 2004, and 1.39 million square kilometers (537,000 square miles) below the 1981 to 2010 long-term average.

During the month, daily sea ice extents tracked about 600,000 square kilometers (232,000 square miles) below any previous year in the 38-year satellite record. Daily extents in May were also two to four weeks ahead of levels seen in 2012, which had the lowest September extent in the satellite record. The monthly average extent for May 2016 is more than one million square kilometers (386,000 square miles) below that observed in May 2012.

Sea ice extent remains below average in the Kara and Barents seas, continuing the pattern seen throughout winter 2015 and 2016. Sea ice also remains below average in the Bering Sea and the East Greenland Sea. In the Beaufort Sea, large open water areas have formed near the coast and ice to the north is strongly fragmented due to wind-driven divergence. The opening began in February, continued through March, and greatly expanded in April.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of May 31, 2016, along with daily ice extent data for four previous years.

Figure 2. The graph above shows Arctic sea ice extent as of May 31, 2016, along with daily ice extent data for four previous years. 2016 is shown in blue, 2015 in green, 2014 in orange, 2013 in brown, and 2012 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Provisional data. Not a Sea Ice Index product.

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

The average ice loss during May 2016 was 61,000 square kilometers (23,600 square miles) per day. This was faster than the 1981 to 2010 long-term average rate of decline of 46,600 square kilometers (18,000 square miles) per day. May air temperatures at the 925 hPa level were 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) above the 1981 to 2010 average across most of the Arctic Ocean, with localized higher temperatures in the Chukchi Sea (4 to 5 degrees Celsius or 7 to 9 degrees Fahrenheit) and in the Barents Sea (4 degrees Celsius or 7 degrees Fahrenheit). Air pressure patterns were not particularly unusual, but two areas of southerly winds in northern Europe and Alaska pushed higher than average temperatures into the Arctic Ocean, producing hot spots noted above and generally above-average temperatures across the Arctic. Only over central Siberia were temperatures lower than the 1981 to 2010 average.

May 2016 compared to previous years

Figure 3. Monthly May Arctic sea ice extent for 1979 to 2016 shows a decline of 2.6% per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly May Arctic sea ice extent for 1979 to 2016 shows a decline of 2.6 percent per decade. Provisional data. Not a Sea Ice Index product.

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

Through 2016, the rate of decline for the month of May is 34,000 square kilometers (13,000 square miles) per year, or 2.6 percent per decade.

Thickness in the Beaufort Sea

Figure 4. The image above shows ice thickness measurements in the Beaufort Sea on April 9 and 10, 2016, superimposed on concurrent imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra and Aqua satellites.

Figure 4a. The image above shows ice thickness measurements in the Beaufort Sea on April 9 and 10, 2016, superimposed on concurrent imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra and Aqua satellites. Short black lines demarcate the boundary between first-year (south) and multiyear (north) regimes.

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

Figure 4b. This figure shows the difference between March ice thickness and the average of March 2011 to 2016. Data are from the European Space Agency's Cryosat-2 satellite.

Figure 4b. This figure shows the difference between March ice thickness and the average of March 2011 to 2016. Data are from the European Space Agency’s CryoSat-2 satellite.

Credit: R. Ricker, Helmholtz Centre for Polar and Marine Research, ESA
High-resolution image

Satellite and survey data show that ice thicknesses in parts of the Arctic are similar to those observed in 2015, but that ice thickness over the whole region is thinner compared to the last five years. Ice thickness surveys carried out by York University in early April 2016 show that thicknesses in the Northwest Passage are similar to that in 2015, though there is less multiyear ice in 2016. In the southern Beaufort Sea, the thickness of multiyear ice is also similar to the previous year, but because of strong divergence and export, first-year sea ice is considerably thinner than in 2015, giving rise to expectations of earlier melt out of this thin ice and formation of open water in 2016. Data from the European Space Agency’s CryoSat-2 satellite show that first-year ice in March 2016 is thinner compared to the March 2011 to 2016 average, especially in the Beaufort Sea (20 to 40 centimeters thinner) and the Barents and Kara seas (10 to 30 centimeters thinner). Multiyear ice north of Canada and Greenland is also thinner.

The thinner first year ice may partly explain the early development of open water in the southern Beaufort Sea for this month. The multiyear ice on the other hand may survive and slow down the overall retreat of the ice edge, as it did in 2015 when a band of multiyear ice survived throughout most of the summer. However, the multiyear ice regime this year seems more fragmented and interspersed with thinner first-year ice. When this thinner ice melts, dark open water areas may grow rapidly as energy is absorbed which in turn melts more ice and can accelerate multiyear ice decay.

Fragmented ice in the Beaufort Sea

Figure 5. The image above shows a May 21 view of Arctic sea ice in the Beaufort Sea from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. |

Figure 5. The image above shows a May 21, 2016 view of Arctic sea ice in the Beaufort Sea from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor.

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

As discussed in last month’s post, a large area in the Beaufort Sea shows a very fragmented ice cover as a result of strong wind-driven divergence throughout the late winter and spring. Figure 5 shows a MODIS visible-band image from May 21, 2016 for the southern Beaufort Sea, illustrating how the fragmentation has led to large multiyear ice floes surrounded by first-year ice and open water. The area of fragmented ice now nearly reaches the pole. While thick, multiyear ice can better survive the summer melt season, the early development of open water allows temperatures in the ocean mixed layer (top 20 meters) to rise, which may enhance lateral ice melt in that region. In summer 2007, early retreat of sea ice from the coasts of Siberia and Alaska, combined with unusual clear skies, led to enhanced melt of thick multiyear ice floes, some recording nearly 3 meters (10 feet) of bottom melt. If atmospheric conditions this summer are as favorable as they were in 2007, some of this multiyear ice may not survive the summer.

Report from the field: Barrow, Alaska

Figure 6a. Researchers use an auger to drill into the sea ice off Barrow, Alaska.

Figure 6a. Researchers use an auger to drill into the sea ice off Barrow, Alaska. After drilling a hole, they would then use a tape measure to record ice thickness.

Credit: W. Meier, NASA
High-resolution image

Figure 6b. NASA researcher Walt Meier stands in a melt pond on the sea ice off Barrow, Alaska.

Figure 6b. NASA researcher Walt Meier stands in a melt pond on the sea ice off Barrow, Alaska.

Credit: W. Meier, NASA
High-resolution image

NASA research scientist and NSIDC Arctic Sea Ice Analysis contributor Walt Meier spent the last week in Barrow, Alaska taking part in a National Science Foundation-funded sea ice camp and workshop. The goal was to bring together modelers, remote sensing scientists, and field researchers to understand each other’s work and to develop new ways to collaborate and combine knowledge about the Arctic sea ice system. As part of the camp, groups trudged onto the ice daily to take measurements. They found the ice to be quite thin at 80 to 100 centimeters (31 to 39 inches), compared to an average year when thicknesses would be 140 to 150 centimeters (55 to 59 inches). Melt ponds had already formed, though during cooler days, there was some refreezing as well. The residents of Barrow conveyed that it has been a very unusual winter. Normally, there is quite a bit of onshore wind from the west. This pushes the ice together and grounds pieces to the shallow shelf offshore, which helps stabilize the ice cover. However, this year the winds have been almost always from the east. This keeps the ice near the shore flat and undeformed (which the group observed during the camp) and opens up leads, or areas of open water, at the edge of the fast ice, which is clear in satellite imagery. This westward flow is a part of the larger Beaufort Gyre flow that has dominated the entire Beaufort and Chukchi sea region for much of the winter.

Record low snow

Figure 7. This snow cover anomaly map shows the percent difference between snow cover for May 2016 compared with average snow cover for May from 1971 to 2000. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than average.

Figure 7. This snow cover anomaly map shows the percent difference between snow cover for May 2016 compared with average snow cover for May from 1981 to 2010. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than average.

Credit: D. Robinson and T. Estilow, Rutgers University Global Snow Lab
High-resolution image

The Northern Hemisphere had exceptionally low snow coverage for both April and May of 2016 and a record low spring (March, April, and May), as reported from 50 years of mapping by Rutgers University’s Global Snow Lab. April’s snow cover was the lowest at 27.91 million square kilometers (10.78 million square miles), and May was the fourth lowest at 16.34 million square kilometers (6.3 million square miles).

The National Oceanic and Atmospheric Administration announced on May 20 that Barrow, Alaska recorded the earliest snowmelt (snow-off date) in 78 years of recorded climate history. Typically snow retreats in late June or early July, but this year the snowmelt began on May 13, ten days earlier than the previous record for that location set in 2002.

Below average sea ice in the Antarctic

Figure 8a. Antarctic sea ice extent for May 2016 was 10.6 million square kilometers (4.13 million square miles).

Figure 8a. Antarctic sea ice extent for May 2016 was 10.6 million square kilometers (4.13 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole. Provisional data. Not a Sea Ice Index product.

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

Figure 8b. The graph above shows Antarctic sea ice extent as of June 2, 2016, along with daily ice extent data for 2015. 2016 is shown in blue and 2015 in green. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data.

Figure 8b. The graph above shows Antarctic sea ice extent as of June 2, 2016, along with daily ice extent data for 2015. 2016 is shown in blue and 2015 in green. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

Sea ice extent in the Southern Hemisphere grew fairly slowly in May compared to the average, causing it to dip below the long-term average by the second half of the month. Antarctic sea ice extent for May 2016 averaged 10.70 million square kilometers (4.13 million square miles). This is 90,000 square kilometers (35,000 square miles) below the 1981 to 2010 long-term average of 10.79 million square kilometers (4.17 million square miles). Antarctic sea ice has been trending at near-average to below-average levels since June of 2015. In May 2016, extent was particularly low in the Bellingshausen Sea, Fimbul Ice Shelf area, and Wilkes Land Coast, but well above average in the northwestern Weddell Sea near the Antarctic Peninsula.

References

Haas, C. 2012. Airborne observations of the distribution, thickness, and drift of different sea ice types and extreme ice features in the Canadian Beaufort Sea, Proceedings of the Arctic Technology Conference ATC, Houston, Texas, December 3?5, 2012, Paper No. OTC 23812, 8 pp.

Haas, C., and S. E. L. Howell. 2015. Ice thickness in the Northwest Passage, Geophysical Research Letters, 42, doi:10.1002/2015GL065704.

Perovich, D. K., J. A. Richter-Menge, K. F. Jones and B. Light. 2008. Sunlight, water and ice: Extreme Arctic sea ice melt during the summer of 2007, Geophysical Research Letters, 35, L11501, doi:10.1029/2008GL034007.

 

Daily sea ice extent updates resume with provisional data

NSIDC has obtained data from the DMSP F-18 satellite and is in the process of intercalibrating the F-18 data with F-17 data. Intercalibration addresses differences between the series of sensors, in order to provide a long-term, consistent sea ice record. While this work continues, we are displaying the uncalibrated F-18 data in the daily extent image. The daily time series graph shows F-17 data through March 31, and F-18 data from April 1 forward. Initial evaluation of the uncalibrated F-18 data indicates reasonable agreement with F-17, but the data should be considered provisional and quantitative comparisons with other data should not be done at this time.

Because these are provisional data, the Sea Ice Index has not been updated and continues to display only F-17 data through March 31. We expect to make the F-18 data available in Charctic soon.

For general information on the intercalibration of sensors, see the documentation for Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data. This documentation will be updated when the intercalibration to F-18 is complete.

For more information on the F-17 satellite sensor issues, see our previous post.

Extended outage of NSIDC’s sea ice data source; April sea ice extent very low

The Defense Meteorological Satellite Program (DMSP) F17 satellite is experiencing continuing issues with its passive microwave sensor. Data from the 37V channel, used to observe sea ice, have been unusable since early April, although the 37H channel used for the Greenland Ice Sheet Today melt area mapping is unaffected. NSIDC is working to bring the DMSP F18 satellite online for its near-real-time source of data for sea ice monitoring. Based on other data sources, sea ice extent remains far below average for the satellite record period, and likely setting record daily lows. The April sea ice decline rate appears to have been slightly faster than average.

Overview of conditions

sea ice concentration map

Figure 1a. Arctic sea ice concentration, in percent concentration, for May 1, 2016 from the Japan Aerospace Exploration Agency (JAXA) satellite Shizuku (GCOM-W1) AMSR2 instrument. Areas of ocean with at least 15% ice concentration are considered ice-covered, when calculating sea ice extent.

Credit: Japan Aerospace Exploration Agency, courtesy University of Bremen
High-resolution image

sea ice extent graphs

Figure 1b. The graphs show Arctic sea ice extent as of April 29, 2016, along with ice extent data for previous years. Top, sea ice extent for 2016 from the Japan Aerospace Exploration Agency (JAXA) satellite Shizuku (GCOM-W1) AMSR2 instrument. Bottom, similar plot using the same sensor but a different method and channel, from University of Bremen.

Credit: National Snow and Ice Data Center/JAXA/University of Bremen
High-resolution image

The Arctic Sea Ice News and Analysis reference sea ice product, the Sea Ice Index, will be suspended until a new calibration can be completed for the F18 satellite, which is underway. The Advanced Microwave Scanning Radiometer 2 (AMSR2) instrument flying on Shizuku (GCOM-W1), a satellite operated by the Japan Aerospace Exploration Agency (JAXA), provides data on sea ice extent and rates of change, but because it uses a different sensor and processing algorithm, the extent numbers cannot be directly compared with those from the SMMR-SSM/I-SSMIS instruments record; the AMSR2 algorithm gives extents that differ by several tens of thousands of square kilometers, or a fraction of a percent to a few percent of total sea ice extent.

A look at the Arctic Data archive system at the National Institute of Polar Research in Japan reveals that sea ice since mid-April has remained at record low daily levels as assessed over their archive of sea ice extent, and is approximately 400,000 square kilometers (154,400 square miles) below the previous daily record extents at this time. This is supported by another analysis of sea ice extent produced by the University of Bremen using the same satellite but a different sensor channel. Both assessments of sea ice extent indicate that the April rate of decline for 2016 is slightly faster than the long-term average of their respective archives. Another sea ice monitoring site, The Cryosphere Today, continues to use the DMSP F17 data, and their graphics show evidence of the sensor issues. This site reports sea ice area in its graphical trend, not extent (area of ocean with at least 15% sea ice coverage) as do the other sites and NSIDC. However, the trend and record low daily extents for the second half of April may be interpreted from these data as well.

Conditions in context

temperature and pressure anomaly plots

Figure 2. Left, sea level pressure for April 2016 relative to average conditions for the same month, 1981 to 2010. Right, air temperature departure from average for April 2016 at the 925 hPa level (approximately 2,500 feet altitude) relative to the same reference period.

Credit: National Snow and Ice Data Center/NOAA ESRL Physical Sciences Division
High-resolution image

April 2016 was quite warm over nearly all of the Arctic Ocean. Air temperatures at the 925 hPa level (about 2,500 feet above the surface) were typically 3 to 5 degrees Celsius (6 to 9 degrees Fahrenheit) above average over the central Arctic Ocean, with larger positive departures compared to average over central Siberia (6 to 8 degrees Celsius, or 11 to 18 degrees Fahrenheit). The sea level pressure pattern featured above average pressures over the Beaufort Sea north of Alaska, and below average pressures over the Aleutians, western Baffin Bay, and Scandinavia. The April 2016 Arctic Oscillation Index transitioned from positive to negative through the month, consistent with the varied patterns of pressure over the Arctic. See our previous discussion of the Arctic Oscillation.

Twist and shout

MODIS animation

Figure 3. This series of images from April 1 to 24, 2016 shows recent fracturing and rotation of sea ice near Alaska and the western Canadian Arctic archipelago. Click on the image to see the animation. Images are from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument via NASA Worldview.

Credit: National Snow and Ice Data Center/NASA Worldview
Play the animation

Using a series of images from the Moderate Resolution Imaging Spectrometer (MODIS) from NASA Worldview, we created a short video showing sea ice drift north of Alaska in the Beaufort Sea. The strong anti-cyclonic (high air pressure) pattern produced surface winds that fractured the ice, twisting it in a clockwise direction and opening the pack ice significantly. Dramatic, similar fracturing of sea ice in the Beaufort Sea has been noted in earlier posts (see March 6, 2013).

 

Motion in the ocean

ice age maps

Figure 4a. Sea ice age mappings for 2015, Week 36 (at the summer sea ice minimum extent) showing the differences between the old (left) and new (right) processing. The improvements in the new processing have resulted in changes in the ice age mapping.

Credit: National Snow and Ice Data Center, courtesy M. Tschudi, C. Fowler, J. Maslanik, R. Stewart/University of Colorado Boulder; W. Meier/NASA Cryospheric Sciences
High-resolution image
View comparison images for 2011 to 2015

age extent plot

Figure 4b. The graph compares the extent of ice in each age category (in years) for 2015 Week 36, at the time of the sea ice minima, from versions 2 (Old NRT) and 3 (New NRT) of the near-real-time ice age algorithm.

Credit: National Snow and Ice Data Center, courtesy W. Meier/NASA Cryospheric Sciences
High-resolution image

The NSIDC sea ice motion and sea ice age products have recently been updated via a release of Version 3. This version was created by re-running the previous algorithms, and incorporating a few improvements. First, a number of unrealistic AVHRR and buoy velocities that had been noted were removed. Also, a more accurate sea ice mask, based on the same sea ice concentration product used in our sea ice extent analysis, was implemented. Finally, the Version 3 updates include buoy-derived motions in the Arctic through the entire time series (1979 to 2015). Near-real-time processing of provisional ice age data, which are frequently shown here as a first look at ice conditions, has also been updated to include some of the improvements of Version 3, including the incorporation of near-real-time buoy data and NSIDC’s near-real-time sea ice concentration product as the basis for the sea ice mask. As with any near-real-time product, the fields should be considered provisional and are subject to change. Full details of the product changes and the new processing methods are included in the product documentation for Polar Pathfinder Daily 25 km EASE-Grid Sea Ice Motion Vectors, Version 3 and EASE-Grid Sea Ice Age, Version 3.