NSIDC Artic Sea Ice News

Syndicate content
Sea ice data updated daily with one-day lag
Updated: 4 hours 51 min ago

Baked Alaska and 2017 in review

Wed, 2018-01-03 12:26

Arctic sea ice extent in December 2017 was below average in both the far northern Atlantic and the Bering Sea, and notably high temperatures prevailed over most of the Arctic, especially over Central Alaska. We look back at the year’s events, and examine Arctic sea ice trends since 1850 based on a new compilation of data from maps, ship reports, and other records.

Overview of conditions Figure 1. Arctic sea ice extent for December 2016 was 11.75 million square kilometers (4.54 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for December 2017 was 11.75 million square kilometers (4.54 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for December 2017 averaged 11.75 million square kilometers (4.54 million square miles), the second lowest in the 1979 to 2017 satellite record. This was 1.09 million square kilometers (420,900 square miles) below the 1981 to 2010 average and 280,000 square kilometers (108,100 square miles) above the record low December extent recorded in 2016. Extent at the end of the month was below average in the far northern Atlantic Ocean and Barents Sea, slightly above average in western Hudson Bay, and continued to be below average in the Bering and Chukchi Seas. Near-average conditions prevailed along the eastern coast of Greenland and in the Sea of Okhotsk.

Conditions in context Figure 2. The graph above shows Arctic sea ice extent as of January 2, 2018, along with daily ice extent data for four previous years. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2014 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2012 to 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data.

Figure 2a. The graph above shows Arctic sea ice extent as of January 2, 2018, along with daily ice extent data for five previous years. 2017 to 2018 is shown in blue, 2016 to 2017 in green, 2015 to 2014 in orange, 2014 to 2015 in brown, 2013 to 2014 in purple, and 2012 to 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

 NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division

Figure 2b. This plot shows the departure from average air temperatures at the 925 hPa level in degrees Celsius for December 2017. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Figure 2c. This plot shows the departure from average sea level pressures at the 925 hPa level in degrees Celsius for December 2018. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.|

Figure 2c. This plot shows the departure from average sea level pressures at the 925 hPa level in degrees Celsius for December 2018. Yellows and reds indicate higher than average air pressures; blues and purples indicate lower than average air pressures.

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

Ice growth during December 2017 averaged 59,800 square kilometers (23,100 square miles) per day. This was fairly close to the average rate for the month of 64,100 square kilometers (24,800 square miles) per day. Ice growth in the Chukchi Sea (very late compared to previous years), the Kara Sea, and the eastern Hudson Bay areas were the main regions of change in December. In contrast, the ice edge slightly retreated in the Barents Sea near Franz Josef Land.

December air temperatures at the 925 hPa level (about 2,500 feet above sea level) throughout the Arctic Ocean were 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) above average. Prominent warm spots were found over north Central Asia and Central Alaska (more than 10 degrees Celsius, or 18 degrees Fahrenheit above average), as well as over Svalbard and Central Siberia (nearly 6 degrees Celsius or 11 degrees Fahrenheit above average). Temperatures were 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) below average in Eastern Siberia.

The air temperature pattern in December was similar to that seen in November, driven in part by the arrangement of high and low air pressure regions surrounding the Arctic. Below-average pressure over easternmost Siberia and above-average pressure over the Gulf of Alaska drove southwesterly winds into Central Alaska and the Yukon region. Warmth in the Central Arctic and in Svalbard was consistent with southerly winds arising from low pressure over Scandinavia and higher pressure in the Laptev Sea and Central Siberia.

The Arctic Oscillation (AO) is a key climate indicator for general wind, precipitation, and temperature patterns in the Arctic. The AO index was moderately positive through most of 2017, indicating a tendency toward strong circumpolar winds at high latitude and warm conditions in the mid-latitudes. December 2017 had a mix of conditions, resulting in a near-neutral AO state (as measured by the index).

December 2017 compared to previous years Figure 3. Monthly December ice extent for 1979 to 2017 shows a decline of 3.7 percent per decade.

Figure 3. Monthly December ice extent for 1979 to 2017 shows a decline of 3.7 percent per decade.

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

The linear rate of sea ice decline for December is 47,400 square kilometers (18,300 square miles) per year or 3.7 percent per decade. Recall from our previous post that NSIDC has revised the way in which monthly average extents are computed, which has some impacts on computed trends.

2017 year in review Figure 4. These figures show trends for sea ice-over dates in the Beaufort (top) and Chukchi (bottom) Seas.

Figure 4. These figures show trends for ice-over dates in the Beaufort (top) and Chukchi (bottom) Seas. Sea Ice Index data.

Credit: R. Thoman, NOAA
High-resolution image

The winter of 2016 to 2017 saw record low winter sea ice extent and higher than average temperatures. Indeed, the first four months of 2017 set or tied record low extents for the month. However, the melt season progressed somewhat slowly from May through July, as storminess and relatively cool conditions began to prevail. As such, sea ice extent at the seasonal minimum, on September 13, ended up as eighth lowest.

Assessments of sea ice thickness modeled by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS), as well as sea ice age near the seasonal minimum extent indicate that Arctic sea ice remains very low in overall volume. As the year ended, ice extent remained especially low in the Chukchi and Bering Seas. As discussed in an earlier post, the unusually early seasonal ice retreat in the Chukchi Sea this past summer likely relates to a strong inflow of oceanic heat into the region via the Bering Strait. With more heat in the upper ocean at summer’s end, it takes longer for sea ice to form in autumn and winter. Colleague Rick Thoman of the National Oceanic and Atmospheric Administration (NOAA) National Weather Service has assembled a time series of the ice-over dates in both the Chukchi and Beaufort Seas based on the satellite passive microwave record (Figure 4). The ice-over date is defined as the first day that the ice concentration exceeds 95 percent in the region. The trends towards later freeze up in both seas is striking. This has an impact on sea ice thickness as the growth season is shortened, which may lead to thinner ice by the end of winter. On the other hand, later freeze up also means less time for snow accumulation on the sea ice. Since sea ice grows faster for a thinner snowpack, this may partially offset the impacts of late ice formation.

A longer record of Arctic sea ice extent Figure 5a. This figure shows departures from 1850 to 2013 calendar-month averages of Arctic sea ice extent as a function of year (x-axis) and calendar month (y-axis). The color bar at the right shows magnitudes of departures from the average.

Figure 5a. This figure shows departures from 1850 to 2013 calendar-month averages of Arctic sea ice extent as a function of year (x-axis) and calendar month (y-axis). The color bar at the right shows magnitudes of departures from the average.

Credit: J. E. Walsh, F. Fetterer, J. S. Stewart, W. L. Chapman. 2016. Geographical Review; after a figure by J. Stroeve, National Snow and Ice Data Center
High-resolution image

 F. Fetterer/National Snow and Ice Data Center, NOAA

Figure 5b. These sea ice concentration maps compare the lowest September minimum Arctic sea ice extents for the periods 1850 to 1900, 1901 to 1950, 1951 to 2000, and 2000 to 2013.

Credit: F. Fetterer/National Snow and Ice Data Center, NOAA
High-resolution image

Using a compilation of maps, ship reports, and other records, NOAA has published monthly estimates of Arctic sea ice extent spanning 1850 to 2013. While data in the earlier part of the record is limited, the carefully constructed time series helps to put the more recent satellite record in a longer-term context. Figure 5a shows the decline in extent over the period of satellite observations standing out prominently in comparison with the rest of the record, especially in late summer and early autumn. An earlier period of unusually low summer sea ice extent around 1937 to 1943 (as compared to the 1850 to 2013 average) did not extend to the winter season, and was followed by a few years of significantly higher-than-average summer ice extents. Early in the record (1850 to 1900), winter ice extent was not particularly elevated relative to the 1850 to 2013 average, but summer sea ice extent was quite a bit higher higher than the average. As another way to place recent conditions into a longer context using this data set, we show the years of the lowest September extent recorded within the 50-year periods 1850 to 1900, 1901 to 1950, 1951 to 2000, along with the lowest over the period 2000 to 2013 (Figure 5b). The decline in extent is apparent.

Low sea ice extent in the Antarctic Figure 6. Antarctic sea ice extent for December 2017 was 9.34 million square kilometers (3.61 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 6. Antarctic sea ice extent for December 2017 was 9.34 million square kilometers (3.61 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

In the Southern Hemisphere, sea ice for December 2017 averaged 9.34 million square kilometers (3.61 million square miles) and was the fourth lowest in the satellite record. Sea ice extent was far below average in the eastern Weddell Sea, but above average in the northwestern Weddell Sea. The East Antarctic coastline had near-average ice extent. As the Southern Hemisphere entered into the summer months, sea ice declined steeply. Temperatures at the 925 hPa level were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) higher than average in Dronning Maud Land and the northern Ross Sea, and generally lower than average over the ice sheet. Near-average temperatures have prevailed over the fringing Southern Ocean. Pressures were slightly above average over the continent and below average in the surrounding ocean. Consistent with this pattern, the Southern Annular Mode index, a measure of the strength of westerly winds, was moderately positive for December.

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.

Categories: Climate Science News

Record low extent in the Chukchi Sea

Wed, 2017-12-06 09:45

November 2017 will be remembered not for total Arctic ice extent, which was the third lowest recorded over the period of satellite observations, but for the record low extent in the Chukchi Sea. This is a key area for Arctic Ocean access, and is an indicator of oceanographic influences on sea ice extent.

Overview of conditions  National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for November 2017 was 9.46 million square kilometers (3.65 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for November 2017 averaged 9.46 million square kilometers (3.65 million square miles), the third lowest in the 1979 to 2017 satellite record. This was 1.24 million square kilometers (479,000 square miles) below the 1981 to 2010 average and 830,000 square kilometers (321,000 square miles) above the record low November extent recorded in 2016. Extent at the end of the month was below average over the Atlantic side of the Arctic, primarily in the Barents and Kara Seas, slightly above average in western Hudson Bay, but far below average in the Chukchi Sea. This continues a pattern of below-average extent in this region that has persisted for the last year.

Conditions in context timeseries graph

Figure 2. The graph above shows Arctic sea ice extent as of December 3, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted red. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Ice growth during November 2017 averaged 80,100 square kilometers (30,900 square miles) per day. This was stronger than the average rate for the month of 69,600 square kilometers (26,900 square miles) per day. Ice growth was particularly rapid within Hudson Bay, Baffin Bay, and the Kara Sea.

November air temperatures at 925 hPa (about 3,000 feet above sea level) were above average over essentially all of the Arctic Ocean, with prominent warm spots (more than 6 degrees Celsius, or 11 degrees Fahrenheit above the 1981 to 2010 average) over the Chukchi Sea and north of Svalbard. The unusual warmth in the Chukchi Sea at least in part manifests the extensive open water in this region, but a pattern of winds blowing in from the southwest also appears to have had an influence. The warmth north of Svalbard is more clearly related to the average pattern of atmospheric circulation over the month, with an area of low pressure centered over the Norwegian Sea and an area of high pressure centered north of the Taymyr Peninsula combining to transport warm air into the region.

November 2017 compared to previous years ice extent trend

Figure 3. Monthly November ice extent for 1979 to 2017 shows a decline of 5.14 percent per decade.

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

The linear rate of sea ice decline for November is 55,000 square kilometers (21,200 square miles) per year, or 5.14 percent per decade. Recall from our previous post that NSIDC recently revised the way in which monthly average extents are computed, which has minor impacts on computed trends.

Open water in the Chukchi Sea sea ice concentration

Figure 4. The map at top shows an analysis of sea ice concentration on November 30, 2017 in the area of the Bering and Chukchi Seas. The graph at bottom shows the combined sea ice concentration from 1978 to 2017, based on Sea Ice Index data.

Credit: Rick Thoman of the NOAA National Weather Service Alaska Region
High-resolution image

Based on an analysis by Rick Thoman of the NOAA National Weather Service, as of 19 November, ice extent in the combined Beaufort and Chukchi Seas sector was the lowest ever observed in the sea ice record (Figure 4). This was largely driven by the lack of sea ice within the Chukchi Sea. By the end of November, the Beaufort Sea was completely ice-covered. The NOAA analysis makes use of the NSIDC Sea Ice Index data set. As discussed in our June 7 post, the current state of the ice cover in this region likely has its origin as far back as last year, when warm conditions favored the persistence of open water in the Chukchi Sea into December of 2016.

Strong winds from the north occurred for a few days at the end of March and early April, pushing ice southward in the Bering Sea, breaking up the ice in the Chukchi Sea, and even flushing some ice out through the Bering Strait. We also suggested a possible role of a strong oceanic heat inflow to the Chukchi Sea via Bering Strait. In support of this view, in the summer of 2017, Rebecca Woodgate of the University of Washington, Seattle, sailing on the research vessel Norseman II, recovered mooring data that indicated an early arrival of warm ocean water in the strait, about a month earlier than the average. This resulted in June ocean temperatures that were 3 degrees Celsius (5 degrees Fahrenheit) above average. Higher ocean temperatures in summer plays a large role in the timing of when the ice will form again in winter. There is likely a considerable amount of heat remaining in the top layer of the ocean, which will need to be lost to the atmosphere and outer space before the region becomes fully ice covered.

Low Antarctic sea ice extent

Figure 5a. Antarctic sea ice concentration from AMSR2, in percent, for November 28, 2017. The Maud Rise polynya is seen at top.

Credit: University of Bremen
High-resolution image

Figure 5b. Small tabular icebergs are seen in the marginal ice zone of the northern Weddell Sea on November 22, 2017 during a NASA Operation IceBridge flight.

Credit: NASA/John Sonntag
High-resolution image

In the Southern Hemisphere, where it is late spring, sea ice declined at a faster-than-average pace after the very late-season October 12 maximum extent. This led to the third-lowest November average monthly extent in the satellite record, behind 1986 and 2016. Sea ice extent was near-average in all regions except the Weddell Sea, where extent is at a satellite-era record low.

The atmospheric circulation for November exhibited a very strong wave-3 pattern. In a wave-3 pattern, there are three major low-pressure areas around the continent separated by three high-pressure areas. Air temperatures for the month were near-average in most regions except for the eastern Weddell Sea, consistent with the reduced sea ice extent there.

The Maud Rise Polynya (Figure 5a) continued to grow through November, as increased sunshine and air temperatures allowed the upwelling warm water to expand the opening in the floating sea ice cover. At the beginning of December,  retreat of the sea ice edge converted the polynya to a large embayment in the sea ice cover.

Categories: Climate Science News

Freezing in the dark

Thu, 2017-11-02 14:30

Rapid expansion of the Arctic sea ice cover is the norm for October as solar input dwindles and the remaining heat in the upper ocean is released upwards, warming the lower atmosphere and escaping to space. Because of late season growth, the seasonal Antarctic maximum we previously reported as occurring on September 15 was exceeded, with a new maximum set on October 11 and 12. This is the second-lowest and second-latest seasonal maximum extent in the satellite record.

Overview of conditions Figure 1. Arctic sea ice extent for October 2017 was6.71 million square kilometers (2.60 million square miles). The magenta line shows the 1981 to 2010 average extent for that month.

Figure 1. Arctic sea ice extent for October 2017 was 6.71 million square kilometers (2.60 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for October 2017 averaged 6.71 million square kilometers (2.60 million square miles), the fifth lowest in the 1979 to 2017 satellite record. This was 1.64 million square kilometers (633,000 square miles) below the 1981 to 2010 average and 820,000 square kilometers (317,000 square miles) above the record low October extent recorded in 2012. By the end of October, extent remained below average throughout most of the Arctic except within the Laptev Sea, which is fully ice covered. Ice growth over the month was most prominent within the Beaufort, East Siberian, and Laptev Seas and within Baffin Bay. In the Chukchi, Kara, and Barents Seas, the rate of ice growth was slower. Ice extent also remains far below average in the East Greenland Sea.

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

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

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

Figure 2b. This plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for October 2017. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Figure 2b. This plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for October 2017. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Figure 2c. This plot shows Arctic air temperatures as a function of both height and latitudes. Above average air temperatures for the Arctic as a whole extend up to approximately 9,200 meters (30,000 feet) high in the atmosphere. Colors indicate temperatures in degrees Celsius. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

Figure 2c. This plot shows Arctic air temperatures as a function of height and latitudes. Above average air temperatures for the Arctic as a whole extend up to approximately 9,200 meters (30,000 feet) altitude. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.

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

Ice growth during October 2017 averaged 94,200 square kilometers (36,000 square miles) per day. This was 5,100 square kilometers (2,000 square miles) per day faster than the average rate of ice growth for the month. Total ice extent for the month remains more than 2 standard deviations below the 1981 to 2010 average.

October air temperatures at 925 hPa (about 3,000 feet above sea level) were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) above average over most of the Arctic Ocean and up to 7 degrees Celsius (13 degrees Fahrenheit) above average over the East Greenland Sea. Unusually high temperatures over the East Greenland Sea appear to largely reflect the transport of warm air from Eurasia, driven by the combination of above average sea level pressure over the Kara and Barents Seas, and below average pressure over the North Atlantic and Greenland. Elsewhere, above average near surface air temperatures reflect in part the exchange of heat from the ocean to the atmosphere as the ocean cools and sea ice forms, such as within the Chukchi Sea. A plot of temperatures as a function of both height and latitudes shows that the above average air temperatures for the Arctic as a whole extend up to approximately 9,200 meters (30,000 feet) high in the atmosphere.

October 2017 compared to previous years Figure 3. Monthly October ice extent for 1979 to 2017 shows a decline of 9.3 percent per decade.

Figure 3. Monthly October ice extent for 1979 to 2017 shows a decline of 9.3 percent per decade.

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

The linear rate of sea ice decline for October is 77,600 square kilometers (30,000 square miles) per year, or 9.3 percent per decade relative to the 1981 to 2010 average. While this appears as an increase in the rate of October ice retreat compared to the trend reported last year, it is not a climate signal but is rather largely a result of using a different averaging method to derive the monthly average sea ice extent values (see below).

Effects of snow salinity on CryoSat-2 ice freeboard estimates Figure 4. This schematic illustrates how salinity shifts the source of the radar signature in the icepack.

Figure 4. This schematic illustrates how salinity shifts the source of the radar signature in the icepack. Ice thickness can be over-estimated by radar satellites (CryoSat-2) when snow conditions are more saline.

Credit: V. Nandan
High-resolution image

After the end of sea ice melt season, the ocean cools and new sea ice forms. The ice crystals that form expel salt into the water. Some of this salt, or brine, is also expelled upwards to the surface of the ice or into snow that has fallen since the ice formed. The brine is then wicked upwards into the snowpack, leading to a slightly saline snowpack, ranging from 1 to 20 parts per thousand (standard seawater is about 35 parts per thousand). This saline snow is a strong reflector of radar energy.

A recent study led by the Cryosphere Climate Research Group at the University of Calgary investigated the impact of snow salinity on retrieving sea ice thickness from radar altimeters, such as CryoSat-2. The study shows that the snow layers observed over much of the Arctic’s first-year ice are salty enough to reflect the radar pulse from CryoSat-2, a radar altimeter used to measure sea ice thickness and ice sheet elevation. They calculate that a correction factor could compensate for this effect, and improve sea ice thickness measurements. While snow salinity is important, other factors, such as surface roughness and ice density also contribute to uncertainties in ice thickness, and they can potentially cancel each other out. Continued comparisons to observed thickness data is crucial to better quantify these uncertainties.

Antarctica’s double-humped sea ice maximum Figure 5. This graph shows the first and second peaks in extent during the 2017 Antarctic sea ice freeze up.

Figure 5a. This graph shows the first and second peaks in extent during the 2017 Antarctic sea ice freeze up. The extent line for the year 2002 is also shown and has a similar pattern to 2017. Sea Ice Index data. About the data

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

 Institute of Environmental Physics, University of Bremen|High-resolution image

Figure 5b. This map shows Antarctic sea ice concentration on October 31, 2017. Note the Maud Rise polynya at the top of the image. Data are from the Advanced Microwave Scanning Radiometer 2 (AMSR2).

Credit: Institute of Environmental Physics, University of Bremen
High-resolution image

In our last post, we noted that Antarctic sea ice may have reached its maximum extent for the year on September 15, at 17.98 million square kilometers (6.94 million square miles). However, after two weeks of decline, extent increased again reaching a second and final maximum of 18.03 million square kilometers (6.96 million square miles) on October 11 and 12. This is tied with 2002 for the latest maximum on record and is the second lowest Antarctic maximum extent in the satellite data record, slightly higher than 1986. Interestingly, 2002 had a similar Bactrian maximum pattern.

The Maud Rise polynya (or Weddell Sea polynya) continues to be a significant feature of the sea ice cover near 5°E longitude and 65°S. The feature appeared around September 13 and grew to its approximate current extent by September 17. Its current size remains about 30,000 square kilometers (12,000 square miles).

Winds and ocean temperatures continue to drive Antarctic sea ice variability. Since there is no land boundary to the north of the Antarctic continent, sea ice in the Southern Hemisphere is free to expand toward the equator until it reaches water temperatures that are high enough to melt sea ice. As a result, changes in winds or ocean temperatures can have a large influence on the amount of sea ice year to year. Changes in winds related to the positive phase of the Southern Annular Mode (SAM) appear to explain the positive trend in total Antarctic sea ice extent. When the SAM is in a positive phase during austral summer, stronger than average westerly winds blow around the Antarctic continent, and sea ice is pushed both westward and slightly northward due to the Coriolis effect. In addition, below average sea surface temperatures persist through the summer and lead to increased sea ice growth the following autumn, while the negative phase precedes higher sea surface temperatures and reduced sea ice growth. A new study suggests the negative SAM mode during 2016/2017 austral summer largely explained the record minimum Antarctic sea ice extent observed in March 2017.

Revised computation of the monthly mean extent Figure 6. This chart compares the monthly October Arctic sea ice extents generated from the old (black dashed line) and the new (solid black line) averaging method.

Figure 6. This chart compares the monthly October Arctic sea ice extents generated from the old (black dashed line) and the new (solid black line) averaging method. Sea Ice Index data. About the data

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

We have updated the way the monthly average sea ice extent is calculated in the NSIDC Sea Ice Index, the source for our sea ice extent estimates. The monthly average total extent (and area) are now computed as an average of the daily values over the month. Historically, the monthly mean sea ice extent has been calculated based on the monthly mean averaged sea ice concentration field. While there is a rationale for both approaches, the new method is more intuitive and eliminates unusual and unexpected results in months when there is rapid ice growth and retreat. Most of the new monthly mean extents are smaller than the previous values with a mean extent difference between -0.45+0.24 and -0.23+0.16 million square kilometers for the Arctic and Antarctic, respectively. The largest differences for the Arctic occur during the month of October due to the rapid ice growth rates typical at that time of year, with the largest difference of -1.20 million square kilometers in October 2012. Changes in rankings and trends were much smaller because the new method tends to affect all years of a given month in a similar manner. October is also the month with the largest trend difference, increasing in magnitude from -7.4 percent per decade to -9.3 percent per decade. Changes in Arctic trends for other months are much smaller.

Similarly, in the Antarctic, differences in averaging methods results in the largest changes during the month of December when the ice cover is rapidly receding. The largest difference of -1.27 million square kilometers occurs in December 1981. The largest changes in the trends are for January and December with a change in value from +2.7 to +3.5 and +1.2 to +1.9 percent per decade, respectively. For more detailed information on the impacts of the revised averaging methods on trends and rankings, please see NSIDC Special Report 19.

Further reading

Nandan, V., T. Geldsetzer, J. Yackel, M. Mahmud, R. Scharien, S. Howell, J. King, R. Ricker, and B. Else. 2017. Effect of snow salinity on CryoSat-2 Arctic first-year sea ice freeboard measurements: Sea ice brine-snow effect on CryoSat-2. Geophysical Research Lettersdoi:10.1002/2017GL074506.

Doddridge, E. W. and J. Marshall. 2017. Modulation of the seasonal cycle of Antarctic sea ice extent related to the Southern Annular Mode. Geophysical Research Letters, 44, 9761–9768. doi: 10.1002/2017GL074319.

Windnagel, A., M. Brandt, F. Fetterer, and W. Meier. 2017. Sea Ice Index Version 3 Analysis. NSIDC Special Report 19. https://nsidc.org/sites/nsidc.org/files/files/NSIDC-special-report-19.pdf.

Categories: Climate Science News

Arctic sea ice 2017: Tapping the brakes in September

Thu, 2017-10-05 10:49

After setting a record low seasonal maximum in early March, Arctic sea ice extent continued to track low through July. However, the rate of ice loss slowed in August and September. The daily minimum extent, reached on September 13, was the eighth lowest on record, while the monthly average extent was seventh lowest. In Antarctica, sea ice extent may have reached its annual winter maximum.

Overview of conditions ice extent image

Figure 1. Arctic sea ice extent for September 2017 was 4.87 million square kilometers (1.88 million square miles). The magenta line shows the 1981 to 2010 average extent for that month. Sea Ice Index data. About the data

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

Arctic sea ice extent for September 2017 averaged 4.87 million square kilometers (1.88 million square miles), the seventh lowest in the 1979 to 2017 satellite record. This was 1.67 million square kilometers (645,000 square miles) below the 1981 to 2010 average, and 1.24 million square kilometers (479,000 square miles) above the record low September set in 2012.

After reaching the minimum on September 13 (eighth lowest on record), extent initially increased slowly (about 20,000 square kilometers, or 8,000 square miles, per day). However, starting September 26 and persisting through the end of the month, ice growth rates increased to about 60,000 square kilometers (23,000 square miles) per day. During the second half of the month, extent increased in all sectors except in the Beaufort Sea, where some local ice retreat persisted. The most rapid growth occurred along the Siberian side of the Arctic Ocean, where the ice edge advanced as much as 150 kilometers (90 miles) over the latter half of September. At the end of September, the ice edge in the Beaufort and Chukchi Seas remained considerably further north than is typical.

Conditions in context extent timeseries

Figure 2a. The graph above shows Arctic sea ice extent as of October 4, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

pressure anomaly

Figure 2b. This image shows the departure from average sea level pressure in millibars over the Arctic for June, July, and August in 2017. Yellows and reds indicate higher than average pressures; blues and purples indicate lower than average pressures.

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

September air temperatures at the 925 hPa level (approximately 2,500 feet above sea level) were above average over much of the Arctic Ocean. Temperatures ranged from 5 degrees Celsius (9 degrees Fahrenheit) above the 1981 to 2010 long term average in the far northern Atlantic east of Greenland, to 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) above the reference period in the western Arctic. Cooler conditions (1 degree Celsius or 2 degrees Fahrenheit below average) were present in Baffin Bay. Part of the above average temperatures over the coastal areas of the Arctic Ocean and in the northern North Atlantic likely results from heat fluxes from open water.

Looking back at this past summer (June through August), air temperatures at the 925 hPa level averaged for June through August were near or below the 1981 to 2010 average over much of the Arctic Ocean, notably along the Siberian side centered over the Laptev Sea (1 degree Celsius or 1.8 degrees Fahrenheit below the 1981 to 2010 average). By contrast, temperatures were slightly above average over much of the East Siberian, Chukchi and Beaufort Seas (1 degree Celsius, or 1.8 degrees Fahrenheit above average).

Like 2016, the summer of 2017 was characterized by persistently stormy patterns over the central Arctic Ocean, reflected in the summer average sea level pressure field (Figure 2b) as an area of low pressure centered just south of the North Pole in the Siberian sector of the Arctic. As has been shown in past studies, low pressure systems found over the central Arctic Ocean in summer are typically “cold cored.” This helps to explain the cool summer temperatures noted above. The cyclonic (counterclockwise) winds associated with the stormy pattern also tend to spread out the sea ice. Both processes likely helped to slow sea ice loss this summer.

September 2017 compared to previous years ice trend

Figure 3. Monthly September ice extent for 1979 to 2017 shows a decline of 13.2 percent per decade.

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

The linear rate of sea ice decline for September is 86,100 square kilometers (33,200 square miles) per year, or 13.2 percent per decade relative to the 1981 to 2010 average. For comparison, the decline rate was calculated at 13.7 percent after the 2013 minimum, and 13.4 percent in 2016. Although sea ice shows significant year-to-year variability, the overall trend of decline remains strong.

Thickness and age trends in Arctic sea ice from models and data

Figure 4a. This image from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) shows Arctic sea ice thickness departures from average (anomaly) in meters for September 2017, relative to the 2000 to 2015 average. Reds indicate thicker than average ice; blues indicate thinner than average ice.

Credit: NSIDC courtesy University of Washington Polar Science Center
High-resolution image

ice age

Figure 4b. Sea ice age distribution at the annual minimum extent for 1985 (upper left) and 2017 (upper right). Time series (bottom) of different age categories the minimum extent for 1985 to 2017. Note that the ice age product does not include ice in the Canadian Archipelago. Data from Tschudi et al., EASE-Grid Sea Ice Age, Version 3

Credit: W. Meier/National Snow and Ice Data Center, M. Tschudi et al.
High-resolution image

According to estimates from the University of Washington Polar Science Center’s PIOMAS, which assimilates observational data into a coupled ice-ocean model, sea ice volume was at record low levels from January through June of 2017. However, the generally cool summer conditions slowed the rate of ice melt, and the ice volume for September ended up fourth lowest in the PIOMAS record, above 2010, 2011, and 2012.

Another way to assess the volume of the ice, at least in a qualitative sense, is through tracking sea ice age (Figure 4b). Older ice is generally thicker ice. Over the satellite record, there has been a significant decline in coverage of the oldest, thickest ice. While this year’s minimum sea ice extent is higher than in 2016, the marginal gain can be largely attributed to younger ice types: first-year ice (0 to 1 years old) and second-year ice (1 to 2 years old). The oldest ice, that which is over 4 years old, is only slightly higher than last year and remains almost non-existent within the Arctic. At the minimum this year, ice older than 4 years constituted only ~150,000 square kilometers (~58,000 square miles), compared to over 2 million square kilometers (~770,000 square miles) during the mid-1980s.

Antarctic maximum extent antarctic sea ice

Figure 5. The graph above shows Antarctic sea ice extent as of October 4, 2017, along with daily ice extent data for 2017 (aqua), 2016 (red), 2013 (dotted green), and 1986 (yellow). The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Antarctic sea ice may have reached its maximum extent on September 15, at 17.98 million square kilometers (6.94 million square miles), among the earliest maxima on record. If this date and extent hold, it will be the second-lowest daily maximum in the satellite record, 20,000 square kilometers (7,700 square miles) above 1986. Antarctic sea ice extent has been at record or near-record lows since September 2016. A series of recent studies have explored causes of the sudden decline in extent that occurred in austral late winter and spring of 2016. Most studies conclude that an unusual period of strong meridional winds—consistent with a very pronounced negative phase of the Southern Annular Mode index, coupled with a significant ‘wave-3 pattern’ in the atmospheric circulation—were the cause. A ‘wave-3 pattern’ refers to a tendency for circulation around the southern continent to resemble a three-leaf clover, rather than the more typical near-zonal (along lines of latitude) pattern.

The Maud Rise polynya, discussed in our last post, continues to grow and is now at about 35,000 square kilometers (14,000 square miles). A recent study (see Further reading, below) discusses how its formation is related to climate patterns and natural variability, and that the recent reappearance supports a forecast by an updated climate model.

Driftwood and long-term changes in Arctic ice movement circulation

Figure 6. The maps show two modes of wintertime Arctic sea ice circulation patterns. (a) shows the Low Arctic Oscillation (AO) index has a strong Beaufort Gyre which supports ice re-circulation within the Arctic. (b) shows the High AO index in which the Beaufort Gyre is weak and the Transpolar Drift expands, leading to Arctic ice exported in a shorter time interval. Bold numbers show the average time in years for ice starting from various locations to be exported through Fram Strait under the illustrated patterns. The red dashed lines encircle the region of ice recirculation and persistence (Rigor et al., 2002). Over continents, light blue lines show watersheds with named major rivers (shown as bold blue lines) that export driftwood into the Arctic Ocean. Green letters indicate driftwood sample regions: CAA, Canadian Arctic Archipelago; EG, East Greenland; JM, Jan Mayen; NG, North Greenland; FJL, Franz Josef Land; NZ, Novaya Zemlya; SB, Svalbard. Circulation patterns compiled and modified from Rigor et al. (2002).

Credit: G. Hole and M. Macias-Fauria, The Cryosphere Discuss.
High-resolution image

While the satellite record has been key in documenting large declines in the Arctic sea ice cover during the past four decades, the data record is still relatively short. To provide a longer record, scientists turn to the geologic record and proxy data. One approach is to analyze the age, transport, and deposition of driftwood. Driftwood distribution depends strongly on past sea ice conditions and ocean currents. New research using 913 driftwood samples collected across the western Arctic (Figure 6) has shed new insight on sea ice changes during the Holocene, between 12,000 years ago to present. During the early Holocene (12,000 to 8,000 years ago), the analysis suggests that the clockwise Beaufort Gyre dominated Arctic Ocean circulation, allowing more sea ice to stay within the Arctic Ocean. In the mid-Holocene (8,000 to 4,000 years ago), temperatures were higher and the Transpolar Drift dominated, leading to more ice export out of the Arctic Ocean through Fram Strait and less sea ice in the Arctic Ocean. In the late Holocene (4,000 years ago to present), the Beaufort Gyre once again strengthened as temperatures slowly cooled until the most recent several decades.

Further reading

Hole, G. M. and M. Macias-Fauria. 2017. Out of the woods: Driftwood insights into Holocene pan-Arctic sea ice dynamic., J. Geophys. Res. Oceans, 122, doi:10.1002/2017JC013126.

Reintges, A., T. Martin, M. Latif, and W. Park. 2017. Physical controls of Southern Ocean deep-convection variability in CMIP5 models and the Kiel Climate Model. Geophys. Res. Lett., 44 (13), 6951-6958, doi:10.1002/2017GL074087.

Rigor, I.G., Wallace, J.M. and Colony, R.L. 2002. Response of sea ice to the Arctic Oscillation. Journal of Climate,15 (18), 2648-2663, doi:10.1175/1520-0442(2002)015<2648:ROSITT>2.0.CO;2.

Schlosser, E., Haumann, F. A., and Raphael, M. N. Atmospheric influences on the anomalous 2016 Antarctic sea ice decay. The Cryosphere Discuss., doi:10.5194/tc-2017-192, in review, 2017.

Categories: Climate Science News

Arctic sea ice at minimum extent

Tue, 2017-09-19 12:00

On September 13, Arctic sea ice appears to have reached its seasonal minimum extent of 4.64 million square kilometers (1.79 million square miles), the eighth lowest in the 38-year satellite record. The overall rate of ice loss this summer was slowed by a persistent pattern of low sea level pressure focused over the central Arctic Ocean.

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 13, 2017 was 4.64 million square kilometers (1.79 million square miles), the eighth lowest in the satellite record. The orange line shows the 1981 to 2010 average extent for that day.

Figure 1. Arctic sea ice extent for September 13, 2017 was 4.64 million square kilometers (1.79 million square miles), the eighth lowest in the satellite record. The orange line shows the 1981 to 2010 average extent for that day. Sea Ice Index data. About the data

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

On September 13, 2017, sea ice extent reached an annual minimum of 4.64 million square kilometers (1.79 million square miles). This was 1.58 million square kilometers (610,000 square miles) below the 1981 to 2010 median extent for the same day, and 1.25 million square kilometers (483,000 square miles) and 500,000 square kilometers (193,000 square miles) above the 2012 and 2016 extents for the same day, respectively.

During the first two weeks of September, the ice edge continued to retreat in the Chukchi, East Siberian, and Kara Seas, whereas it slightly expanded in the Beaufort and Laptev Seas. The ice edge remains far to the north of its average position in the Chukchi Sea. The Northern Sea Route is largely open; Amundsen’s Northwest Passage (the southern route) has up to 50 percent ice cover in some places, though as noted in our last post, ships have successfully navigated through the southern route with icebreaker assistance. The northern Northwest Passage route, entered from the west via McClure Strait, remains choked by consolidated, thick, multi-year ice.

Conditions in context  National Snow and Ice Data Center|High-resolution image

Figure 2a. The graph above shows Arctic sea ice extent as of September 17, 2017, along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dashed brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.

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

Figure 2b. This image shows average sea level pressure over the Arctic Ocean for the period of September 1 to 16, 2017.

Figure 2b. This image shows average sea level pressure over the Arctic Ocean for the period of September 1 to 16, 2017.

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

The date of the minimum ice extent for 2017 was two days earlier than the average minimum date of September 15. The earliest annual sea ice minimum in the satellite record occurred on September 5 in the years 1980 and 1987, and the latest on September 23, 1997.

As is typical of this time of year when the solar radiation received at the surface is quickly waning, the rate of ice loss slowed during the first half of September. Ice retreat from the beginning of September until the minimum averaged 25,300 square kilometers (9,770 square miles) per day, slightly faster than the 1981 to 2010 average for the same period of 22,800 square kilometers (8,800 square miles) per day.

The pattern of low sea level pressure over the central Arctic Ocean that persisted through this summer and inhibited summer ice loss has broken down. For the first half of September, the pattern has instead been one of above-average sea level pressure centered over the Barents Sea and extending across part of the Arctic Ocean (Figure 2b). Corresponding air temperatures at the 925 hPa level (about 2,500 feet above sea level) were above average over most of the Arctic Ocean. Above average temperatures over some parts of the Arctic Ocean likely reflect heat transfer to the atmosphere from areas of open water, hence cooling the ocean.

Ten lowest minimum Arctic sea ice extents (satellite record, 1979 to present) Table 1.  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 4 2011 4.34 1.67 Sept. 11 5 2015 4.43 1.71 Sept. 9 6 2008 4.59 1.77 Sept. 19 7 2010 4.62 1.78 Sept. 21 8 2017 4.64 1.79 Sept. 13 9 2014 5.03 1.94 Sept. 17 10 2013 5.05 1.94 Sept. 13 Effects of seasonal ice retreat in the Beaufort and Chukchi Seas  Courtesy R. Thoman/National Weather Service Alaska Region Environmental and Scientific Services Division| High-resolution image

Figure 3. This chart shows combined sea ice extent in the Chukchi and Beaufort Seas from August 15 to October 7 for the years 2006 to 2016, including the extent so far for 2017. The colored dots show the day the minimum occurred in the region during a specific year. Data are from the Multisensor Analyzed Sea Ice Extent (MASIE) product.

Credit: Courtesy R. Thoman/National Weather Service Alaska Region Environmental and Scientific Services Division
High-resolution image

According to a report by the Alaska Dispatch News, the lack of sea ice forced walruses to the shore of Alaska’s Chukchi Sea earlier than any time on record. The lack of ice also forced biologists monitoring Alaska polar bears to cut short their spring field season. In turn, the NOAA National Weather Service Climate Prediction Center states that because of the extensive open water, air temperatures over the Beaufort and Chukchi Seas and along the North Slope of Alaska will likely be far above average through this autumn.

Rick Thoman of the National Weather Service in Fairbanks, Alaska compiled an analysis of the combined Chukchi and Beaufort Seas ice extent from the Multisensor Analyzed Sea Ice Extent (MASIE) product. MASIE is based on operational ice analyses at the U.S. National Ice Center and is archived and distributed by NSIDC. It shows that 2017 tracked near record lows for the region through much of the summer, but after mid-August the pace of ice loss slowed relative to recent years. While it appears unlikely that extent in the Beaufort and Chukchi Seas will reach a record low (set in 2012), it will still be among the four or five lowest in the MASIE record (Figure 3). Note that the range in dates for the minimum extent in the region differs from those for the Arctic as a whole and tend to be later, ranging from September 10 in 2015 to September 25 in 2007 and 2008. In other words, the Chukchi and Beaufort Seas may continue to lose ice even after the overall Arctic minimum extent is reached. From the passive microwave data (not shown), the Chukchi/Beaufort minimum has occurred as early as August 14 in 1980 to as late as October 2 in 1991.

Antarctic sea ice approaching winter maximum Figure 4a. The graph above shows Antarctic sea ice extent as of September 17, 2017, along with daily ice extent data for four previous years.

Figure 4a. The graph above shows Antarctic sea ice extent as of September 17, 2017, along with daily ice extent data for four previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in dashed brown, 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

 This map shows Antarctic sea ice concentration on September 16, 2017. Note the Maud Rise polynya at the top of the image. Data are from the Advanced Microwave Scannig Radiometer 2 (AMSR2).

Figure 4b: This map shows Antarctic sea ice concentration on September 16, 2017. Note the Maud Rise polynya at the top of the image. Data are from the Advanced Microwave Scannig Radiometer 2 (AMSR2).

Credit: G. Heygster, C. Melsheimer, J. Notholt/Institute of Environmental Physics, University of Bremen
High-resolution image

Following the record low summer minimum extent in March, Antarctic sea ice extent is now nearing its winter maximum. This will likely be among the five lowest winter extents in the satellite era. As of mid-September, Antarctic ice extent was just under 18 million square kilometers (7 million square miles), which is approximately half a million square kilometers below the 1981 to 2010 median ice extent. Sea ice is below the typical extent in the Indian Ocean sector, the northern Ross Sea, and the northern Weddell Sea, and slightly above average extent in the northern Amundsen Sea region.

Between September 9 and September 17 of 2016, Antarctic sea ice lost nearly 100,000 square kilometers (38,600 square miles) of sea ice per day, and sea ice extent moved from near-average to a near-record-daily low by September 17. For the next 12 months Antarctic sea ice remained extremely low. Record low ice extents were set every day from November 5, 2016 to April 10, 2017. Extents averaged for November and December of 2016 were five standard deviations below average. No other 12-month period (September 2016 to August 2017) has had such persistently low sea ice extent. The year 1986 had near-record low extent for the winter period (June to December), but there were periods of near-average and even above-average ice extent earlier in the calendar year.

Beginning around September 2, an opening in the Antarctic sea ice pack formed north of Dronning Maud Land in the easternmost Weddell Sea (near 64°S, 5°E). By mid-September, this opening, or polynya, had grown to about 12,000 square kilometers (4,600 square miles). This feature has been observed intermittently in the Antarctic pack ice since the first satellite data became available in the 1970s. In 1974, 1975, and 1976, the polynya was much larger, averaging 250,000 square kilometers (96,500 square miles). It was absent for many years in the 1980s and 1990s. In recent years the feature has been observed sporadically and has been much smaller.

The polynya is formed when ocean currents uplift deep warm ocean water to the surface where it melts the sea ice. An oceanic plateau called the Maud Rise is responsible for forcing the vertical movement of the water. The persistence of certain atmospheric patterns, such as the southern annular mode, or SAM, is thought to play a role in driving the deep water layer against the Maud Rise.

2017 Arctic sea ice minimum animation

See the NASA animation of Arctic sea ice extent from the beginning of the melt season on March 8, 2017 to the day of the annual minimum on September 13, 2017 here.

Further reading

Gordon, A.L., Visbeck, M. and Comiso, J.C. 2007. A possible link between the Weddell Polynya and the Southern Annular Mode. Journal of Climate20(11), 2558-2571. doi:10.1175/JCLI4046.1

Holland, D.M. 2001. Explaining the Weddell Polynya–a large ocean eddy shed at Maud Rise. Science, 292(5522), 1697-1700. doi:10.1126/science.1059322.

Erratum

In Table 1, years 2014 and 2013 were both ranked ninth lowest. They should have been ninth and tenth respectively. This has been corrected.

 

 

Categories: Climate Science News