Arctic sea ice maximum at record low for third straight year

Arctic sea ice appears to have reached its annual maximum extent on March 7. This is the lowest maximum in the 38-year satellite record. NSIDC will post a detailed analysis of the 2016 to 2017 winter sea ice conditions in our regular monthly post in early April.

Overview of conditions

Figure 1. Arctic sea ice extent for March 7, 2017 was 14.42 million square kilometers (5.57 million square miles). The orange line shows the 1981 to 2010 median extent for that day.

Figure 1. Arctic sea ice extent for March 7, 2017 was 14.42 million square kilometers (5.57 million square miles). The orange line shows the 1981 to 2010 median extent for that day. Sea Ice Index data. About the data

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

On March 7, 2017, Arctic sea ice likely reached its maximum extent for the year, at 14.42 million square kilometers (5.57 million square miles), the lowest in the 38-year satellite record. This year’s maximum extent is 1.22 million square kilometers (471,000 square miles) below the 1981 to 2010 average maximum of 15.64 million square kilometers (6.04 million square miles) and 97,000 square kilometers (37,000 square miles) below the previous lowest maximum that occurred on February 25, 2015. This year’s maximum is 100,000 square kilometers (39,000 square miles) below the 2016 maximum, which is now third lowest. (In 2016, we reported that year’s maximum as the lowest and 2015 the second lowest. An update to the Sea Ice Index last summer has changed our numbers slightly.)

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of March 20, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data.

Figure 2a. The graph above shows Arctic sea ice extent as of March 20, 2017, along with daily ice extent data for five previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, 2012 to 2013 in purple, and 2011 to 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level in degrees Celsius from October 1, 2016 to February 28, 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average.

Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level (about 2,500 feet above sea level) in degrees Celsius from October 1, 2016 to February 28, 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average.

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

It was a very warm autumn and winter. Air temperatures at the 925 hPa level (about 2,500 feet above sea level) over the five months spanning October 2016 through February 2017 were more than 2.5 degrees Celsius (4.5 degrees Fahrenheit) above average over the entire Arctic Ocean, and greater than 5 degrees Celsius (9 degrees Fahrenheit) above average over large parts of the northern Chukchi and Barents Seas. These overall warm conditions were punctuated by a series of extreme heat waves over the Arctic Ocean.

Data from the European Space Agency’s CryoSat-2 satellite indicate that this winter’s ice cover may be only slightly thinner than that observed at this time of year for the past four years. However, an ice-ocean model at the University of Washington (PIOMAS) that incorporates observed weather conditions suggests the volume of ice in the Arctic is unusually low.

The Antarctic minimum

Figure 3. Antarctic sea ice extent for March 3, 2017 was 2.11 million square kilometers (813,000 million square miles). The orange line shows the 1981 to 2010 average extent for that day.

Figure 3. Antarctic sea ice extent for March 3, 2017 was 2.11 million square kilometers (815,000 square miles). The orange line shows the 1981 to 2010 median extent for that day. Sea Ice Index data. About the data

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

In the Southern Hemisphere, sea ice likely reached its minimum extent for the year on March 3, at 2.11 million square kilometers (815,000 square miles). This year’s minimum extent was the lowest in the satellite record, continuing a period of satellite-era record low daily extents that began in early November. However, the Antarctic system has been highly variable. As recently as 2015, Antarctic sea ice set record high daily extents, and in September 2014 reached a record high winter maximum.

The Antarctic minimum extent is 740,000 square kilometers (286,000 square miles) below the 1981 to 2010 average minimum of 2.85 million square kilometers (1.10 million square miles) and 184,000 square kilometers (71,000 square miles) below the previous lowest minimum that occurred on February 27, 1997.

Antarctic air temperatures during the autumn and winter were above average, but less so than in the Arctic. Air temperatures at the 925 hPa level (about 2,500 feet above sea level) near the sea ice edge have been about 1 to 2.5 degrees Celsius (2 to 4.5 degrees Fahrenheit) above the 1981 to 2010 average.

Final analysis pending

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

Correction

On March 27, 2017, we made corrections to clarify the second paragraph under Conditions in context. The paragraph originally read:

Data from the European Space Agency’s CryoSat-2 satellite indicate that this winter’s ice cover is slightly thinner compared to the past four years. An ice-ocean model at the University of Washington that incorporates observed weather conditions suggests the volume of ice in the Arctic is unusually low for this time of year.

Another warm month in the Arctic

High air temperatures observed over the Barents and Kara Seas for much of this past winter moderated in February. Overall, the Arctic remained warmer than average and sea ice extent remained at record low levels.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2017 was 14.28 million square kilometers (5.51 million square miles). The magenta line shows the 1981 to 2010 median 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 February 2017 was 14.28 million square kilometers (5.51 million square miles). The magenta line shows the 1981 to 2010 median extent for the month. Sea Ice Index data. About the data

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

Arctic sea ice extent for February 2017 averaged 14.28 million square kilometers (5.51 million square miles), the lowest February extent in the 38-year satellite record. This is 40,000 square kilometers (15,400 square miles) below February 2016, the previous lowest extent for the month, and 1.18 million square kilometers (455,600 square miles) below the February 1981 to 2010 long term average.

Ice extent increased at varying rates, with faster growth during the first and third weeks, and slower growth during the second and fourth weeks. Most of the ice growth in February occurred in the Bering Sea, though extent in the Bering remained below average by the end of the month. Sea ice extent in the Sea of Okhotsk substantially decreased mid-month before rebounding to almost typical levels at the end of the month. Overall, however, the ice retreated in this region. Extent in the Barents and Kara Seas remained low through the month as is has all season, with little change in the ice edge location.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of March 5, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of March 5, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data. About the data

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

Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level in degrees Celsius for February 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division| High-resolution image

Figure 2b. The plot shows Arctic air temperature differences at the 925 hPa level in degrees Celsius for February 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average.

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

Air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) remained 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) above average over the Arctic Ocean. The high air temperatures observed over the Barents and Kara Seas for much of this past winter moderated in February. February air temperatures over the Barents Sea ranged between 4 to 5 degrees Celsius (8 to 9 degrees Fahrenheit) above average, compared to 7 degrees Celsius (13 degrees Fahrenheit) above average in January. Recall that these January temperature extremes were associated with a series of strong cyclones entering the Arctic Ocean from the North Atlantic, drawing in warm air. Sea level pressure in February was nevertheless lower than average over much of the Arctic Ocean. Sea level pressure was higher than average over the Bering Sea and just north of Scandinavia.

February 2017 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2017 shows a decline of 3 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

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

Credit: National Snow and Ice Data Center
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The linear rate of decline for February is 46,900 square kilometers (18,100 square miles) per year, or 3 percent per decade.

Antarctic minimum extent

Figure 4a. The graph above shows Antarctic sea ice extent as of March 5, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 4a. The graph above shows Antarctic sea ice extent as of March 5, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 in purple. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 4b. This graph shows monthly ice extent for February plotted as a time series of percent differences with respect to the average over the period 1981 through 2010. The dotted gray line shows the linear trend. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 4b. This graph shows monthly ice extent for February, plotted as a time series of percent differences from the 1981 to 2010 average. The dotted gray line shows the linear trend. Sea Ice Index data. About the data

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

Antarctic sea ice is nearing its annual minimum extent and continues to track at record low levels for this time of year. On February 13, Antarctic sea ice extent dropped to 2.29 million square kilometers (884,000 square miles), setting a record lowest extent in the satellite era. The previous lowest extent occurred on February 27, 1997. By the end of February, extent had dropped even further to 2.13 million square kilometers (822,400 square miles). The record lows are not surprising, given Antarctic sea ice extent’s high variability. Just a few years back, extent in the region set record highs (Figure 4b).

Sea ice extent was particularly low in the Amundsen Sea, which remained nearly ice-free throughout February. Typically, sea ice in February extends at least a couple hundred kilometers along the entire coastline of the Amundsen. Near-average ice extent persisted in the Weddell Sea and in several sectors along the East Antarctic coast.

Continuity of the sea ice record

Figure 5. This chart shows the lifespans of current and future orbiting passive microwave sensors. ||Credit: Walt Meier, NASA| High-resolution image

Figure 5. This chart shows the lifespans of current and expected future orbiting passive microwave sensors.

Credit: W. Meier, NASA Goddard Space Flight Center Cryospheric Sciences Laboratory
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As noted last year, the sensor that NSIDC had been using for sea ice extent, the Special Sensor Microwave Imager and Sounder (SSMIS) on the Defense Meteorological Satellite Program (DMSP) F17 satellite, started to malfunction. In response, NSIDC switched to the SSMIS on the newer F18 satellite. Later, F17 recovered to normal function, though it recently started to malfunction again.

The DMSP series of sensors have been a stalwart of the sea ice extent time series, providing a continuous record since 1987. Connecting this to data from the earlier Scanning Multichannel Microwave Radiometer (SMMR) results in a continuous record starting in 1979 of high quality and consistency. However, with the issues of F17 and last year’s loss of the newest sensor, F19, grave concerns have arisen about the long-term continuity of the passive microwave sea ice record. Only two DMSP sensors are currently fully capable for sea ice observations: F18 and the older F16; these two sensors have been operating for over 7 and 13 years respectively, well beyond their nominal 5-year lifetimes.

The only other similar sensor currently operating is the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2), which is approaching its 5-year design lifetime in May 2017. NSIDC is now evaluating AMSR2 data for integration into the sea ice data record if needed. Future satellite missions with passive microwave sensors are either planned or proposed by the U.S., JAXA, and ESA, but it is unlikely that a successor to the DMSP series and AMSR2 will be operational before 2022. This presents a growing risk of a gap in the sea ice extent record. Should such a gap occur, NSIDC and NASA would seek to fill the gap as much as possible with other types of sensors (e.g., visible or infrared sensors).

Low sea ice extent continues in both poles

Sea ice in the Arctic and the Antarctic set record low extents every day in December, continuing the pattern that began in November. Warm atmospheric conditions persisted over the Arctic Ocean, notably in the far northern Atlantic and the northern Bering Sea. Air temperatures near the Antarctic sea ice edge were near average. For the year 2016, sea ice extent in both polar regions was at levels well below what is typical of the past several decades.

Overview of conditions

Figure 1. Arctic sea ice extent for December 2016 was 12.10 million square kilometers (4.67 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole.

Figure 1. Arctic sea ice extent for December 2016 was 12.10 million square kilometers (4.67 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 December 2016 averaged 12.10 million square kilometers (4.67 million square miles), the second lowest December extent in the satellite record. This is 20,000 square kilometers (7,700 square miles) above December 2010, the lowest December extent, and 1.03 million square kilometers (397,700 square miles) below the December 1981 to 2010 long-term average.

The rate of ice growth for December was 90,000 square kilometers (34,700 square miles) per day. This is faster than the long-term average of 64,100 square kilometers (24,700 square miles) per day. As a result, extent for December was not as far below average as was the case in November. Ice growth for December occurred primarily within the Chukchi Sea, Kara Sea, and Hudson Bay—areas that experienced a late seasonal freeze-up. Compared to the record low for the month set in 2010, sea ice for December 2016 was less extensive in the Kara, Barents, and East Greenland Seas, and more extensive in Baffin and Hudson Bays.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of January 2, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 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.

Figure 2a. The graph above shows Arctic sea ice extent as of January 2, 2017, along with daily ice extent data for four previous years. 2016 to 2017 is shown in blue, 2015 to 2016 in green, 2014 to 2015 in orange, 2013 to 2014 in brown, and 2012 to 2013 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 air temperature difference from average for December 2016. Air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) were more than 3 degrees Celsius (5 degrees Fahrenheit) above the 1981 to 2010 average over the central Arctic Ocean and northern Barents Sea, and as much as 5 degrees Celsius (9 degrees Fahrenheit) above average over the Chukchi Sea.

Figure 2b. This plot shows air temperature difference from average for December 2016. Air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) were more than 3 degrees Celsius (5 degrees Fahrenheit) above the 1981 to 2010 average over the central Arctic Ocean and northern Barents Sea, and as much as 5 degrees Celsius (9 degrees Fahrenheit) above average over the Chukchi Sea.

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

Air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) were more than 3 degrees Celsius (5 degrees Fahrenheit) above the 1981 to 2010 average over the central Arctic Ocean and northern Barents Sea, and as much as 5 degrees Celsius (9 degrees Fahrenheit) above average over the Chukchi Sea. Repeated warm air intrusions occurred over the Chukchi and Barents Seas, continuing the pattern seen in November.

In contrast, central Russia and northern British Columbia experienced temperatures 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) below average (Figure 2b). Atmospheric circulation over the Arctic in December was characterized by a broad area of lower-than-average pressure over Greenland and the North Pole, extending across the Arctic Ocean to eastern Siberia, and another region of low pressure over the Ural Mountains. Higher-than-average pressure dominated Europe and the Gulf of Alaska. This set up the very warm southerly winds from both the northern North Atlantic and the Bering Strait areas, pushing Arctic air temperatures to unusually high levels for brief periods in early December and near Christmas.

December 2016 compared to previous years

Figure 3. Monthly December ice extent for 1979 to 2016 shows a decline of 3.4 percent per decade.

Figure 3. Monthly December ice extent for 1979 to 2016 shows a decline of 3.4 percent per decade.

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

Through 2016, the linear rate of decline for December is 44,500 square kilometers (17,200 square miles) per year, or 3.4 percent per decade.

While daily extents for December 2016 were at record lows, based on the method employed by NSIDC, the monthly average extent for December 2016 was slightly higher than that recorded for December 2010, the record low December in the satellite record. The monthly average extent for the month of December is higher than the month’s average of daily extents because of the way in which the Sea Ice Index algorithm calculates the monthly extent. The algorithm calculates the monthly average total extent from the monthly average gridded concentration field. Thus, when sea ice is retreating or advancing at a high rate over the course of the month, as was the case for December 2016, the Sea Ice Index monthly average can yield a larger extent than from simply averaging daily extent values. See the Sea Ice Index documentation for further information.

2016 year in review

Figure 4. Arctic temperatures at the 925 hPa level (about 2,500 feet above sea level) over the period January to December of 2016 were above average over nearly the entire Arctic region and especially over the Arctic Ocean. By contrast, air temperatures over the Antarctic region for the same period were above average in some areas, such as the Antarctic Peninsula and near the pole, but below average in others.

Figure 4. Arctic temperatures at the 925 hPa level (about 2,500 feet above sea level) over the period January to December of 2016 were above average over nearly the entire Arctic region and especially over the Arctic Ocean. By contrast, air temperatures over the Antarctic region for the same period were above average in some areas, such as the Antarctic Peninsula and near the pole, but below average in others.

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

Average annual sea ice extent in both polar regions was low in 2016. Throughout the year, a wave of new record lows were set for both daily and monthly extent. Record low monthly extents were set in the Arctic in January, February, April, May, June, October, and November; and in the Antarctic in November and December.

For the Arctic, the year opened with daily sea ice extent at near record low levels. Sea ice extent in March tied with 2015 for the lowest maximum in the 37-year satellite period. Ice extent was as much as 500,000 square kilometers (193,000 square miles) below any previous year in the record through most of mid-May to early June. However, the pace of decline returned to near-average rates by July, and the end-of-summer minimum sea ice extent, recorded on September 10, eventually tied for second lowest with 2007 (2012 remains the lowest in the satellite time series by more than 600,000 square kilometers or 232,000 square miles).

That September 2016 did not see a new record low is likely due to the unusually stormy atmospheric pattern that set up over the Arctic Ocean in the summer. Storm after storm moved into the central Arctic Ocean, including a pair of very deep low pressure systems in late August. While a stormy pattern will tend to chew up the ice cover, it also spreads the ice out to cover a larger area and typically brings cloudy and, in summer, relatively cool conditions, inhibiting melt. Sometimes these deep lows act to reduce extent by mixing warm ocean waters upwards, but at present there is no compelling evidence that this occurred in 2016.

In October, a pattern of warm air intrusions from the North Atlantic began. This pattern combined with unusually high sea surface temperatures over the Barents and Kara Seas and helped to keep Arctic sea ice extent at low levels for November and December. In the middle of November there was even a several-day period when Arctic sea ice extent decreased. Unusually warm conditions and record low daily sea ice extent levels continued through the end of the year. The unusually high sea ice surface temperatures reflect a shift in ocean circulation, enhancing the import of warm, Atlantic-derived waters into the Arctic Ocean.

In the Southern Hemisphere, overall sea ice extent shifted from near-average over the first half of the year to sharply below average in mid-August. This initiated a period of near-record, and then extreme record low extents that persisted until late in the year. While the Antarctic seasonal sea ice minimum was unremarkable (slightly earlier, and slightly lower, than the 37-year average), the sea ice maximum occurred early (August 31), followed by a period of rapid ice extent decline. By November, extent was more than 2 million square kilometers (772,000 square miles) below the 1981 to 2010 average extent. In combination with the low Arctic sea ice extent for November, this produced a remarkably low global sea ice total.

The cause of the rapid drop in Antarctic sea ice in the second half of 2016 remains elusive. Significant changes in Southern Ocean wind patterns were observed in August, September, and November, but air temperatures and ocean conditions were not highly unusual.

Sea ice cover in Chukchi Sea depends on Bering Strait inflow

Figure 5. This figure shows time series of the Julian dates of seasonal retreat and advance of sea ice in the Chukchi Sea. The trends in retreat and advance (show by the thin solid lines) are related to climate warming. The variations about the trends line are strongly related to variability in the Bering Strait heat inflow. ||Credit: Serreze, M. C., et al. 2016. Journal of Geophysical Research | High-resolution image

Figure 5. This figure shows time series of the Julian dates of seasonal retreat and advance of sea ice in the Chukchi Sea. The trends in retreat and advance (show by the thin solid lines) are related to climate warming. The variations about the trends line are strongly related to variability in the Bering Strait heat inflow.

Credit: Serreze, M. C., et al. 2016. Journal of Geophysical Research

High-resolution image

A recent study by NSIDC scientists Mark Serreze, Julienne Stroeve, and Alexander Crawford, along with University of Washington scientist Rebecca Woodgate, demonstrates strong links between seasonal sea ice retreat and advance in the Chukchi Sea and the inflow of ocean heat into the region through the Bering Strait. The Chukchi Sea region is important as a focus for resource exploration, and vessels transiting the Arctic Ocean must inevitably pass through it. The Chukchi Sea is also part of the seasonal migration route for Bowhead whales that supports subsistence hunting by local indigenous communities.

Serreze and colleagues looked at time series of the date of retreat and advance in which linear trends related to general warming were removed. They found that 68 percent of the variance in the date that ice retreats from the continental shelf break in the Chukchi Sea in spring can be explained by fluctuations in the April through June Bering Strait oceanic heat inflow. The Bering Strait heat inflow data comes from a mooring located within the strait maintained by the University of Washington. They also found that 67 percent of the variance for the date at which ice advances back to the shelf break in autumn and winter can be related to the combined effects of the July through September Bering Strait inflow and the date of ice retreat. When seasonal ice retreat occurs early, low-albedo open water areas are exposed early, which gain a lot of energy from the sun. With more heat in the upper ocean, autumn ice growth is delayed. These relationships with the Bering Strait inflow and ocean heat uptake are superimposed upon the overall trends due to a warming climate. While these relationships lay a path forward to improving seasonal predictions of ice conditions in the region, developing an operational prediction scheme would require more timely acquisition of Bering Strait heat inflow data than is presently possible.

Global sea ice tracking far below average

Figure 6. This time series of daily global sea ice extent (Arctic plus Antarctic) shows global extent tracking below the 1981 to 2010 average. The lower axis of the graph shows month of the year, ticked at the first day of the month

Figure 6a. This time series of daily global sea ice extent (Arctic plus Antarctic) shows global extent tracking below the 1981 to 2010 average. The X axis shows the month of the year, aligned with the first day of the month. Sea Ice Index data.

Credit: NSIDC
High-resolution image

Figure 6b. Waiting for caption. Lorem ipsum. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 6b. This graph shows daily global sea ice difference from average, relative to the 1981 to 2010 reference period in square kilometers for the satellite record from 1979 through 2016

Credit: National Snow and Ice Data Center
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Figure 6c. Waiting for caption. Lorem ipsum. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 6c. This graph shows daily sea ice difference from average in units of the standard deviation (based on 1981-2010 variation from the average) for this period.

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

Global sea ice (Arctic plus Antarctic) continues to track at record low levels in the satellite record, but the deviation from average has moderated compared to what was observed in November. This reflects a December pattern of faster-than-average growth in the Arctic, and slightly slower-than average sea ice extent decline in the Southern Ocean. The gap between the 1981 to 2010 average and the 2016 combined ice extent for December now stands at about 3.0 million square kilometers (1.16 million square miles), down from a peak difference of just over 4 million square kilometers (1.50 million square miles) in mid-November. This globally combined low ice extent is a result of largely separate processes in the two hemispheres.

Changes to our graphics for 2017

 Figure 7. This comparison shows the changes that will be made to NSIDC time series graphs.

Figure 7. This comparison shows the changes that will be made to NSIDC time series graphs.

Credit: NSIDC
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NSIDC is transitioning the sea ice extent time series graphs to show interquartile and interdecile ranges, with the median extent value, in place of standard deviations and the average values. Standard deviations are most useful with data that are clustered towards the average, or “normally distributed” like a bell curve, with few outliers. Sea ice extent data, however, has become skewed due to the strong downward trend in ice extent, with a wider spread of values and more values falling at the low end of the range. Interquartile and interdecile ranges, along with the median value, are better for presenting data with these characteristics. The interquartile and interdecile ranges more clearly show how the data are distributed and can better distinguish outliers, and so provide a better view of the variability of the data.

Further reading

Serreze, M. C., A. Crawford, J. C. Stroeve, A. P. Barrett, and R. A. Woodgate. 2016. Variability, trends and predictability of seasonal sea ice retreat and advance in the Chukchi Sea. Journal of Geophysical Research, 121, doi:10.1002/2016JC011977.

Sluggish ice growth in the Arctic

After a quick initial freeze-up during the second half of September, ice growth slowed substantially during early October. On October 20, 2016, Arctic sea ice extent began to set new daily record lows for this time of year. After mid-October, ice growth returned to near-average rates, but extent remained at record low levels through late October. High sea surface temperatures in open water areas were important in limiting ice growth. October air temperatures were also unusually high, and this warmth extended from the surface through a considerable depth of the atmosphere.

Overview of conditions

Figure 1. Arctic sea ice extent for October 2016 was 6.40 million square kilometers (2.5 million square miles). The magenta line shows the 1981 to 2010 median extent for that month.

Figure 1. Arctic sea ice extent for October 2016 was 6.40 million square kilometers (2.5 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

In October 2016, Arctic sea ice extent averaged 6.40 million square kilometers (2.5 million square miles), the lowest October in the satellite record. This is 400,000 square kilometers (154,400 square miles) lower than October 2007, the second lowest October extent, and 690,000 square kilometers (266,400 square miles) lower than October 2012, the third lowest. The average extent was 2.55 million square kilometers (980,000 square miles) below the October 1981 to 2010 long-term average.

As of early November, extent remains especially low within the Beaufort, Chukchi, East Siberian, and Kara Seas. Since the beginning of October, ice growth occurred primarily in the Laptev Sea, stretching from the New Siberian Islands towards the coast. Little ice growth occurred in the Kara and Barents Seas, while ice extent increased in the Chukchi and Beaufort Seas.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of November 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

Figure 2a. The graph above shows Arctic sea ice extent as of November 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. Sea surface temperatures were unusually high over the Chukchi and Beaufort seas, as well as the Barents and Kara seas along the Eurasian coast, helping to limit ice growth. This figure shows conditions on October 25, 2016.

Figure 2b. Sea surface temperatures (SSTs) in October were unusually high over the Chukchi and Beaufort Seas, as well as the Barents and Kara Seas along the Eurasian coast, helping to limit ice growth. This figure shows SSTs on October 25, 2016.

Credit: Climate Change Institute/University of Maine
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Figure 2c. Air temperatures at the 925 hPa level were usually high over the Beaufort and Chukchi seas and the East Greenland Sea (up to 8 degrees Celsius or 14 degrees Fahrenheit above average).

Figure 2c. Air temperatures at the 925 hPa level were usually high over the Beaufort and Chukchi Seas and the East Greenland Sea (up to 8 degrees Celsius or 14 degrees Fahrenheit above average).

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

Figure 2d. This latitude by height cross section shows that for the Arctic as a whole, air temperatures were above average not just at or near the surface but through a deep later of the atmosphere. This manifest the combined effects of high sea surface temperatures in open water areas and the effects of atmospheric circulation drawing warm air into the region.

Figure 2d. This latitude by height cross section shows that for the Arctic as a whole, air temperatures were above average not just at and near the surface but through a deep layer of the atmosphere. This resulted from the combined effects of high sea surface temperatures in open water areas and the effects of atmospheric circulation drawing warm air into the region.

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

After an early rapid freeze-up in late September, the rate of ice growth slowed in the first half of October. From October 1 to 15, ice extent increased only 378,000 square kilometers (146,000 square miles), less than a third of the 1981 to 2010 average gain for that period. By October 31, Arctic sea ice extent stood at 7.07 million square kilometers (2.73 million square miles), the lowest extent in the satellite record for that date.

A primary culprit behind the slow growth is that sea surface temperatures in the Beaufort and Chukchi Seas, the Barents and Kara Seas along the Eurasian coast, as well as the East Siberian Sea, were above average. The open water areas in the highest latitudes at the date of the minimum in September had only recently formed and there was little input of solar radiation so far north. So those waters were just above the freezing point. When the atmosphere cooled in September, ice formed rapidly. However, further south, the sea ice had retreated far earlier in the season and a lot of solar energy was absorbed through the summer. This ocean heat inhibited the growth of ice in these regions. Finally toward the end of October, the surface ocean heat began to dissipate, triggering ice formation. However, even by October 25, sea surface temperatures were above average in these areas (Figure 2b).

The atmospheric circulation also played a role. October air temperatures at the 925 hPa level (about 2,500 feet above sea level) were unusually high over most of the Arctic Ocean (Figure 2c), especially over the Beaufort and Chukchi Seas and over the East Greenland Sea (up to 8 degrees Celsius or 14 degrees Fahrenheit above the 1981 to 2010 average). In part, these high temperatures resulted from high sea surface temperatures over the open water areas. However, unusually high sea level pressure centered over northern Scandinavia brought southerly winds from the East Siberian and Barents Seas, contributing to high air temperatures in these regions. In turn, unusually low pressure on the Pacific side centered roughly over the western Bering Sea brought southerly winds over the Beaufort and Chukchi Seas, contributing to unusually high air temperature there. The combined effects of the high sea surface temperatures and atmospheric circulation led to a pattern in which for the Arctic, unusual warmth in October extended from the surface through a deep layer of the atmosphere (Figure 2d).

As noted in our post last month, the Arctic is losing it’s oldest and thickest ice. A new animation from NASA Goddard’s Scientific Visualization Studio shows this loss over the past 30 years. 

October 2016 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2016 shows a decline of 7.4 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly October ice extent for 1979 to 2016 shows a decline of 7.4 percent per decade.

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

Through 2016, the linear rate of decline for October is 66,400 square kilometers or (25,600 square miles) per year, or 7.4 percent per decade.

Antarctic sea ice dropping

Figure 4. Antarctic sea ice extent for October 2016 was 17.6 million square kilometers (6.8 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole.

Figure 4. Antarctic sea ice extent for October 2016 was 17.6 million square kilometers (6.8 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic South Pole. Sea Ice Index data. About the data

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

After a reaching its maximum extent unusually early and then following a period of relatively unchanging overall extent, Antarctic sea ice extent started to decline in earnest. Daily sea ice extent levels have been at second lowest in the satellite record since October 20 and below the two standard deviation range. Only the 1986 austral spring extent is lower. Ice extent is particularly low on both sides of the Antarctic Peninsula. The rapid early reduction in sea ice cover in this region may create favorable conditions for the break up of the eastern Peninsula ice shelves at the end of austral summer. Similar sea ice trends and weather conditions were present during the spring seasons preceding past ice shelf retreats (e.g., 2001 to 2002). Extensive open water, created by the downsloping fosters warmer air and surface melting, and allows longer-period ocean waves to reach the ice front of the ice shelves. Other areas of reduced sea ice cover are the Southern Ocean north of Dronning Maud Land, and the area west of the Ross Sea and north of Wilkes Land.

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 (satellite record, 1979 to present)

Table 2.  Ten lowest minimum Arctic sea ice extents (satellite record, 1979 to present)
 RANK  YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
1 2012 3.39 1.31 Sept. 17
2

 

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.

October 19, 2016: We revised the title for Table 2 from “Ten lowest minimum Arctic sea ice extents (1981 to 2010 average)” to “Ten lowest minimum Arctic sea ice extents (satellite record, 1979 to present)”

 

 

 

 

 

 

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.

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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.

 

March ends a most interesting winter

Low Arctic sea ice extent for March caps a highly unusual winter in the Arctic, characterized by persistent warmth in the atmosphere that helped to limit ice growth. Above-average influx of ocean heat from the Atlantic and southerly winds helped to keep ice extent especially low in the Barents and Kara seas. Northern Hemisphere snow cover for both February and March was also unusually low

Overview of conditions

Figure 1. Arctic sea ice extent for March 2016 was 14.43 million square kilometers (5.57 million square miles). The magenta line shows the 1981 to 2010 median extent for that month.

Figure 1. Arctic sea ice extent for March 2016 was 14.43 million square kilometers (5.57 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
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Sea ice extent reached its seasonal maximum on March 24 of 14.52 million square kilometers (5.607 million square miles), barely beating out February 25, 2015 for the lowest seasonal maximum in the satellite record. Arctic sea ice extent averaged for the entire month of March 2016 was 14.43 million square kilometers (5.57 million square miles), the second lowest in the satellite record. This is 1.09 million square kilometers (421,000 square miles) below the 1981 to 2010 average extent, and 40,000 square kilometers (15,000 square miles) above the record low monthly average for March that occurred in 2015. At the end of the month, extent remained well below average everywhere except in the Labrador Sea, Baffin Bay, and Hudson Bay. Ice extent was especially low in the Barents and Kara seas.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of April 3, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 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.

Figure 2. The graph above shows Arctic sea ice extent as of April 3, 2016, along with daily ice extent data for four previous years. 2015 to 2016 is shown in blue, 2014 to 2015 in green, 2013 to 2014 in orange, 2012 to 2013 in brown, and 2011 to 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
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Because ice extent typically climbs through the first part of March until it reaches its seasonal maximum and then declines, the daily average ice growth rate for the month is typically quite small and is not a particularly meaningful number. This year’s seasonal maximum, while quite low, also occurred rather late in the month. Very early in the month, extent declined, raising anticipation that an early maximum had been reached. However, after a period of little change, extent slowly rose again, reaching the seasonal maximum on March 24.

March of 2016 saw unusually warm conditions over nearly all of the Arctic Ocean. Air temperatures at the 925 hPa level (about 3,000 feet above the surface) were typically 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average over the Arctic coastal seas, with larger positive departures compared to average nearer the Pole (4 to 8 degrees Celsius or 7 to 14 degrees Fahrenheit). This was associated with a pattern of above-average sea level pressures centered over the northern Beaufort Sea north of Alaska, and below-average pressures over the Atlantic side of the Arctic, especially pronounced over Baffin Bay and Davis Strait. Through March, the Arctic Oscillation Index bounced between moderate positive and negative values.

March 2016 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2016 shows a decline of 2.7 percent per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly March ice extent for 1979 to 2016 shows a decline of 2.7 percent per decade.

Credit: National Snow and Ice Data Center
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Arctic sea ice extent averaged for March 2016 was the second lowest in the satellite record. Through 2016, the linear rate of decline for March extent is 2.7 percent per decade, or a decline of 42,100 square kilometers (16,200 square miles) per year.

The winter in review

Figure 4. This graph shows differences in Arctic sea ice from December 28, 2015 to January 4, 2016, estimated from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).

Figure 4. This graph shows differences in Arctic sea ice thickness from December 28, 2015 to January 4, 2016, estimated from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS).

Credit: National Snow and Ice Data Center, courtesy PIOMAS
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Figure 5. This figure shows observed (blue columns) and predicted (cyan) winter sea ice area in the Barents Sea. The prediction is based on observed Atlantic heat entering the Barents Sea and the sea ice area the previous year. The predicted sea ice area for this winter (2016) is well below average, and less than that observed for 2015. Anomalously strong southerly winds have also contributed to the very small sea ice area this winter (not shown).

Figure 5. This figure shows observed (blue columns) and predicted (cyan) winter sea ice area in the Barents Sea. The prediction is based on observed Atlantic heat entering the Barents Sea and the sea ice area the previous year. The predicted sea ice area for this winter (2016) is well below average, and less than that observed for 2015. Anomalously strong southerly winds have also contributed to the very small sea ice area this winter (not shown).

Credit: Ingrid Onarheim/Bjerknes Centre for Climate Research
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Figure 6. This snow cover anomaly map shows the difference between snow cover for March 2016, compared with average snow cover for March 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: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab| High-resolution image

Figure 6. This snow cover anomaly map shows the percent difference between snow cover for March 2016, compared with average snow cover for March 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: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab
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Figure 7. This graph shows snow cover extent anomalies in the Northern Hemisphere for March from 1967 to 2016. The anomaly is relative to the 1981 to 2010 average.

Figure 7. This graph shows snow cover extent anomalies in the Northern Hemisphere for March from 1967 to 2016. The anomaly is relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab
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The unusual warmth for March of 2016 continues a pattern of above-average temperatures for most of the Arctic and much of the Northern Hemisphere that has characterized the entire winter. As an exclamation point on the unusual warmth, there was a brief weather event at the very end of December 2015 when air temperatures near the Pole nearly reached the melting point. As we noted in our January post, the event was related to a pulse of warm air moving almost due south to north from the sub-tropical Atlantic to the regions north of Svalbard, an atmospheric river set between broad high and low pressure areas in Europe and the north Atlantic.

The December event also led to higher than average air temperatures over the Kara and Barents seas, reducing the sea ice concentration and causing thinning of the ice that was there. While sea ice normally grows and thickens over winter, the difference in thickness estimated from Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) shows that between December 28, 2015 and January 4, 2016, sea ice within the Kara and Barents seas thinned by more than 30 centimeters (Figure 4). Thinning also occurred north of Greenland and off the coast of Siberia, while the ice thickened over most of the Arctic Ocean. Higher than average temperatures remained in the region after the weather event had passed, which may have further prevented the ice from growing back. The reasons for the persistent warmth over the entire Arctic this past winter are currently under investigation; a link with the strong El Niño pattern of this winter may be involved.

While the warm atmospheric conditions played a role in the low ice extent for March 2016, the especially low extent that has persisted in the Barents and Kara seas appears to be linked with another heat source—an influx of warm Atlantic waters, entering between Bear Island and Norway (the Barents Sea opening). Ingrid Onarheim from the Bjerknes Centre for Climate Research in Bergen, Norway has been studying this issue and predicted a small sea ice cover in the Barents Sea this winter based on observed Atlantic heat transport to the Barents Sea through April 2015 (Figure 5). In addition to the above-average ocean heat transport, prevailing southerly winds have pushed the sea ice northward since November 2015, bringing in warm air that damps the normally high ocean-air heat loss and favoring ice formation. This likely contributed to the below-average ice conditions in the Arctic this winter. Atlantic heat transport due to near-surface ocean currents reached a long-term maximum in the mid-2000s. Several studies have suggested a more moderate inflow of Atlantic waters may characterize the years ahead, leading to increases in the Barents Sea ice cover in the coming years.

Along with low sea ice extent and above-average temperatures, March of 2016 also saw a very low monthly snow cover extent for the Northern Hemisphere (Figures 6 and 7). Snow cover was low across northern Eurasia, with only minor areas of above-average snow cover in western Turkey, northern Kazakhstan and Mongolia, and easternmost High-Mountain Asia. In North America, snow cover was low across nearly all of the coterminous 48 states in the U.S., despite a series of storms late in the month in the central Rockies and Great Plains. Overall, March 2016 had 37.16 million square kilometers (14.35 million square miles) of snow cover extent, 2.97 million square kilometers (1.15 million square miles) below the 1981 to 2010 average of 40.13 million square kilometers (15.50 million square miles). This makes March 2016 the 49th lowest out of 50 years on record in snow cover extent for the Northern Hemisphere. While April and May could still bring snow to the higher latitudes, we note that low snow cover, similar to low sea ice cover, leads to greater heat absorption by the surface in the Arctic and further warming as we move toward summer.

A younger ice cover

Figure 8. These graphs show Arctic sea ice age from March 4 to 10, 2016. The top graph shows ice age distribution for that week alone and the bottom graph shows ice age distribution for that week from 1985 to 2016.||Credit: NSIDC courtesy University of Colorado Boulder, M. Tschudi, C. Fowler, J. Maslanik, R. Stewart, W. Meier.

Figure 8. These graphs show Arctic sea ice age from March 4 to 10, 2016. The top graph shows ice age distribution for that week alone and the bottom graph shows ice age distribution for that week from 1985 to 2016.

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

Ice age data for mid-March shows that 70 percent of the sea ice within the Arctic basin consists of first-year ice and only 30 percent is multiyear ice. First-year ice is generally only 1.5 to 2 meters (5 to 6.5 feet) thick. This implies a thinner ice pack as the melt season gets underway. In addition, the oldest ice, or ice at least 5 years or older, is at its smallest level in the satellite record, representing only 3 percent of the total ice cover. Some of this very old ice is found in the western Beaufort Sea and extending towards the Chukchi Sea regions where we have seen large summer ice losses in recent years. Typically this old ice is concentrated north of Greenland and within the Canadian Arctic Archipelago.

Not only is the oldest ice at record low levels, but it it is not recovering. Beginning 2007, we see a strong decline that lasts until 2012 and has not changed much since. If anything it has gone down. In that time we have seen some recovery in younger multiyear ice types: e.g., 2-year ice jumped back up after a one-year minimum, 3-year ice recovered to a lesser degree, and 4-year ice to an even lesser degree. It is not surprising to see some recovery and that first-year ice recovery propagates through time. However, that recovery happens less as the ice gets older, and for 5-year ice and older there is essentially no recovery. The bottom line is that ice no longer survives in the Arctic for very long. It is lasting three to four years tops before melting or advecting out through Fram Strait. This is a big change from the past when much of the ice cover would survive upwards of a decade.

Southern view

Antarctic sea ice grew rapidly in March, rising from below-average daily extents to above-average extents during the month, and increasing by nearly 90,000 square kilometers (35,000 square miles) per day. Sea ice growth was particularly fast in the eastern Ross Sea. Winter temperatures on the continent through the month were near-average overall, but 4 to 6 degrees Celsius (7 to 11 degrees Fahrenheit) below average over the eastern Ross Sea and West Antarctic Ice Sheet.