2015 in review

December ended with Arctic sea ice extent tracking between one and two standard deviations below average, as it did throughout the fall. This caps a year that saw the lowest sea ice maximum in February and the fourth lowest minimum in September. In Antarctica, December sea ice extent was slightly above average but far below the exceptionally large ice extents recorded for December 2013 and 2014. A slow-down in the rate of Antarctic sea ice growth in July was followed by near-average extents in the subsequent months. The first week of 2016 has seen very slow ice growth in the Arctic.

Overview of conditions

Figure 1. Arctic sea ice extent for December 2015 was 12.3 million square kilometers (4.74 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 December 2015 was 12.3 million square kilometers (4.74 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

Sea ice extent for December 2015 averaged 12.3 million square kilometers (4.74 million square miles), the fourth lowest December extent in the satellite record. This is 780,000 square kilometers (301,000 square miles) below the 1981 to 2010 average for the month, and 260,000 square kilometers (100,000 square miles) above the record low for December recorded in the year 2010. The rate of sea ice growth slowed slightly through the month and nearly ceased advancing in the first days of the new year, perhaps related to a period of unusual warmth (see below). The ice is currently tracking near two standard deviations below the 1981 to 2010 long-term average. Sea ice extent is well below average in the Bering, Okhotsk, and Barents seas, partly balanced by slightly above average extent in Baffin Bay.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of January 5, 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|High-resolution image

Figure 2. The graph above shows Arctic sea ice extent as of January 5, 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
High-resolution image

Figure 2b. These graphs show average sea level pressure and air temperature anomalies at 925 mb (about 3,000 feet above sea level) for December 2015.||Credit: NSIDC courtesy NOAA Earth

Figure 2b. These graphs show average sea level pressure and air temperature anomalies at 925 millibars (about 3,000 feet above sea level) for December 2015.

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

Arctic sea ice growth for December averaged 65,000 square kilometers (25,000 square miles) per day compared to the long-term average of 64,000 square kilometers (24,700 square miles) per day. Cool conditions at the 925 hPa level (2 to 4 degrees Celsius or 4 to 7 degrees Fahrenheit below average) existed in Baffin Bay, the Alaskan North Slope, and parts of eastern Siberia. A broad area of Europe and western Russia, including the northern Barents Sea, saw temperatures as much as 4 to 8 degrees Celsius (7 degrees to 14 degrees Fahrenheit) above average at the 925 hPa level. Conditions were also fairly warm over the central Arctic Ocean, north of the Canadian Arctic Archipelago. Sea level pressure was below average over much of the Arctic, especially from the northern North Atlantic to the Barents Sea and central Russia, and from the Bering Sea and south along the Canadian Pacific coast (7.5 to 12 millibars below average). This is consistent with the positive phase of the Arctic Oscillation through most of the month, a pattern that has persisted since the end of October.

December 2015 compared to previous Decembers

Figure 3. Monthly December ice extent for 1979 to 2015 shows a decline of 3.4% per decade.||Credit: National Snow and Ice Data Center| High-resolution image

Figure 3. Monthly December ice extent for 1979 to 2015 shows a decline of 3.4% per decade.

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

Arctic sea ice extent averaged for December 2015 was the fourth lowest in the satellite record. Through 2015, the linear rate of decline for December extent is 3.4% per decade, or -44,200 square kilometers (-17,000 miles) per year.

 

2015 in review

The year will be remembered for three major events in sea ice extent: the lowest Arctic maximum in the satellite record, the fourth lowest Arctic minimum in the satellite record, and a return to average levels for Antarctic sea ice extent after more than two years of record and near-record highs.

The record-low Arctic maximum occurred on February 25, 2015 and was among the earliest seasonal maxima in the 37-year satellite record. It was likely a result of very warm conditions in the Sea of Okhotsk and the Barents Sea (4 degrees Celsius or 7 degrees Fahrenheit above average), and low ice extent in the Bering Sea in March (when the maximum would more typically occur). These climate conditions were related to an unusual jet stream pattern as discussed in our April 7, 2015 post.

The fourth lowest Arctic minimum occurred on September 11, 2015 and was likely a consequence of very warm conditions in July and an increasingly young and thin ice cover. The thinner ice is consistent with a tendency in recent years for large polynyas that appear in the Beaufort and Chukchi seas in late summer. Although measurements by the CryoSat-2 satellite indicated that Arctic sea ice was thicker in 2015 compared to pre-2012 thicknesses, the ice behaved as though it was still quite thin.

From February 2013 through June 2015, Antarctic sea ice was at record or near-record daily extents. Antarctic sea ice set consecutive record winter maxima in 2012, 2013 and 2014. (Contrary to 2013 and 2014, autumn and spring conditions in 2012 were near-average.) But during this year’s austral mid-winter period, Antarctic sea ice growth slowed. Since then, extent in the Southern Hemisphere has generally been slightly above average. Climate effects from the building El Niño likely caused the shift during austral mid-winter. A strong El Niño is associated with a change in the position and strength of a major low pressure pattern near West Antarctica, called the Amundsen Sea Low. Weakening of the Amundsen Sea Low, and related impacts elsewhere around the ice edge in Antarctica, tend to reduce ice extent in the Ross Sea, eastern Weddell Sea, and elsewhere around Antarctica except near the Antarctic Peninsula.

The longer view

This graph shows sea ice concentration trends in the Arctic and the Antarctic for March to September for the years 1979 to 2015. Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 4. This graph shows sea ice concentration trends in the Arctic and the Antarctic for March to September for the years 1979 to 2015. Sea Ice Index data. About the data

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

The satellite passive microwave record for sea ice now spans more than 37 years. As we have documented, clear downward trends characterize Arctic sea ice extent and concentration in all months, while somewhat less emphatic upward trends characterize Antarctic sea ice extent and concentration. A look at the geographic distribution of trends for the seasonal maximum and minimum periods provides insight into how the polar regions are changing. During the Arctic maximum, declines in extent and concentration are pronounced in the Barents Sea and Sea of Okhotsk, but ice cover has increased slightly in the Bering Sea. During the Arctic summer minimum, all areas show negative trends.

Antarctica presents a more mixed picture. During the Antarctic summer minimum, ice cover is increasing around much of the coastline from the Weddell Sea eastward to the western Ross Sea, but is declining sharply in the eastern Ross, Amundsen, and southern Bellingshausen seas. Winter ice cover in Antarctica is characterized by increases in the northern Ross Sea and the Indian Ocean sectors, and decreases in the northwestern Weddell Sea and the region south of Australia.

Ringing in the New Year with a brief polar heat wave

Figure 5. These graphs show average sea level pressure and air temperature anomaly at 925 mb (an altitude of about 3,000 feet) for 30 and 31 December, 2015.

Figure 5. These graphs show average sea level pressure and air temperature anomalies at 925 millibars (about 3,000 feet above sea level) for 30 and 31 December, 2015. The graphs are the average of two days, so the extremes in air pressure and temperature during this period are not shown.

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

An exceptional weather event during the last days of the year brought a heat wave with surface air temperatures up to 23 degrees Celsius (50 degrees Fahrenheit) above average in the far north, and a brief period when surface temperatures at the North Pole approached or perhaps even exceeded the freezing mark. A temperature of +0.7 degrees Celsius was briefly recorded by a buoy weather station near the North Pole on December 30, 2015. The event was linked to the combination of a very strong low pressure system near Iceland and a somewhat less intense low pressure system located near the North Pole. This was associated with an amplified trough at 500 hPa over the northern North Atlantic and a pronounced ridge of high pressure at 500 hPa to the east over central Europe, extending into the Kara Sea. This created a strong, deep inflow of warm, moist air into the Arctic Ocean’s high latitudes. The low near Iceland strengthened rapidly in the last days of December, reaching a minimum pressure of 935 millibars, equivalent to a hurricane. While the event was remarkable and may account for the slow ice growth during the first few days of January 2016, it was short lived and is unlikely to have any long-term effects on the sea ice cover.

Further reading

Tilling, R. L., A. Ridout, A. Shepherd, D. J. Wingham. 2015. Increased Arctic sea ice volume after anomalously low melting in 2013. Nature Geoscience 8, 643–646, doi:10.1038/ngeo2489.

Thompson, A. “What happened to the Polar Vortex?” ClimateCentral.com. http://www.climatecentral.org/news/what-happened-to-the-polar-vortex-19866?

Winter is coming to the Arctic

While Arctic sea ice extent is increasing, total ice extent remains below average, tracking almost two standard deviations below the long-term average.

Overview of conditions

Figure 1. Arctic sea ice extent for October 2015 was 7.72 million square kilometers (2.98 million square miles).

Figure 1. Arctic sea ice extent for October 2015 was 7.72 million square kilometers (2.98 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 October 2015 averaged 7.72 million square kilometers (2.98 million square miles), the sixth lowest October in the satellite record. This is 1.19 million square kilometers (460,000 square miles) below the 1981 to 2010 average extent, and 950,000 square kilometers (367,000 square miles) above the record low monthly average for October that occurred in 2007.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of November 2, 2015, along with daily ice extent data for four previous years.

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

Air temperatures at the 925 millibar level were 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) above average over the central Arctic, extending towards Fram Strait. This appears to be due to unusually low pressure over northwest Greenland and higher pressures over the Tamyr Peninsula and Scandinavia, which funneled warm air from the south into the central Arctic Ocean. Coastal regions were generally 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) higher than average.

October 2015 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2015 shows a decline of 6.9%

Figure 3. Monthly October ice extent for 1979 to 2015 shows a decline of 6.9% per decade.

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

Through 2015, the October sea ice extent has declined 6.9% per decade over the satellite record.

New sea ice thickness information back for the winter

Figure 4a. This image from CryoSat-2 shows thin ice (less than 1 meter (3.28 feet) over a wide area north of Greenland.||Credit: Center for Polar Observation and Modeling (CPOM) at University College London| High-resolution image

Figure 4a. This image from CryoSat-2 shows thin ice (less than 1 meter, or 3 feet, thick) over a wide area north of Greenland.

Credit: Center for Polar Observation and Modeling (CPOM) at University College London
High-resolution image

Figure 4b. This image from the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite shows sea ice thickness in the Arctic Ocean, including north and east of Greenland.||Credit: University of Hamburg Integrated Climate Data Center| High-resolution image

Figure 4b. This image from the European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) satellite shows sea ice thickness over the Arctic Ocean.

Credit: University of Hamburg Integrated Climate Data Center
High-resolution image

In recent years, two European Space Agency (ESA) satellites, CryoSat-2 and SMOS (Soil Moisture and Ocean Salinity), have been providing information on sea ice thickness. Thickness information is valuable for assessing the overall condition of the sea ice cover. The sensors on these satellites cannot determine thickness during the summer melt season, but now that freeze-up has begun, information is again available.

CryoSat-2, launched in 2010, is a radar altimeter, which measures the height of the ice cover above the sea surface. Used with additional information on snow cover and its density, the height information can be converted into estimates of ice thickness. The Center for Polar Observation and Modeling (CPOM) at University College London has again started providing near-real-time maps of sea ice thickness from CryoSat-2.

While these maps are valuable in providing near-real-time thickness estimates, converting the satellite measurements into thickness involves complex processing and there are many uncertainties. For example, Figure 4a depicts thin ice (less than 1 meter [3 feet]) over a wide area north of Greenland, an area where wind and ocean current patterns push the ice against the coast forming thick ridges and an extremely rough surface. This area has been shown by other studies to have some of the thickest sea ice in the Arctic, often exceeding 4 meters (13 feet). This ridging may have cause the difficulty in the current mapping.

CryoSat-2 also has difficulty retrieving thickness in very thin sea ice regions, resulting in no thickness values reported at the outer edge of the ice cover. SMOS is a microwave imaging radiometer that measures microwave brightness temperature at a range that is sensitive to thin ice (1.4 gigahertz). These data are also now available in near-real-time at the University of Hamburg Integrated Climate Data Center. SMOS cannot estimate thickness beyond 1 meter (3.28 feet) at most and often not beyond 0.5 meters (1.64 feet). While the map shows a wide region of 1 meter-thick ice, it is important to realize that this is just the maximum allowable value and in reality there is thicker ice over much of the region. However, SMOS provides valuable information on the coverage of thin ice during the winter ice growth season. Ideally, a blended CryoSat-2/SMOS product will provide more comprehensive information on thickness.

A large ozone hole over the Antarctic

Figure 5. The image above shows the ozone hole over Antarctica on October 2, 2015 when it had reached its largest single-day area for the year.

Figure 5. The image above shows the ozone hole over Antarctica on October 2, 2015 when it had reached its largest single-day area for the year, spanning 28.2 million square kilometers (10.9 million square miles). Data are from the Ozone Monitoring Instrument (OMI) on the NASA Aura satellite and the Ozone Monitoring and Profiler Suite (OMPS) on the NASA-NOAA Suomi NPP satellite.

Credit: NASA Earth Observatory, Ozone Hole Watch
High-resolution image

While sea ice in Antarctica is near average, the ozone hole over the continent grew relatively large during the austral winter. This goes against the expected trend towards a smaller ozone hole since the use of chlorofluorocarbons (CFCs) was banned in 1996. The size of the hole in a given year depends on several factors, including temperatures in the high altitude stratosphere. Temperatures in the Antarctic stratosphere were low this year, aiding chemical processes that destroy ozone. For more information on this year’s ozone hole see this NASA Earth Observatory feature.

 

Arctic sea ice reaches fourth lowest minimum

On September 11, Arctic sea ice reached its likely minimum extent for 2015. The minimum ice extent was the fourth lowest in the satellite record, and reinforces the long-term downward trend in Arctic ice extent. Sea ice extent will now begin its seasonal increase through autumn and winter. In the Antarctic, sea ice extent is average, a substantial contrast with recent years when Antarctic winter extents reached record high levels.

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 11, 2015 was 4.41 million square kilometers (1.70 million square miles). The orange line shows the 1981 to 2010 average extent for the 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

Figure 1. Arctic sea ice extent for September 11, 2015, was 4.41 million square kilometers (1.70 million square miles). The orange line shows the 1981 to 2010 average extent for the 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 11, 2015, sea ice extent dropped to 4.41 million square kilometers (1.70 million square miles), the fourth lowest minimum in the satellite record. This appears to be the lowest extent of the year. In response to the setting sun and falling temperatures, ice extent will now climb through autumn and winter. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower.

The minimum extent was reached four days earlier than the 1981 to 2010 average minimum date of September 15. The extent ranked behind 2012 (lowest), 2007 (second lowest), and 2011 (third lowest). Moreover, the nine lowest extents in the satellite era have all occurred in the last nine years.

Both the Northern Sea Route, along the coast of Russia, and Roald Amundsen’s route through the Northwest Passage are open. How long they remain open depends on weather patterns and the amount of heat still present in the ocean mixed layer (about the top 50 feet of the ocean). The deeper and wider Northwest Passage route through Parry Channel, which consists of M’Clure Strait, Barrow Strait, and Lancaster Sound, still has some ice in it.

Conditions in context

Figure 2a. The graph above shows Arctic sea ice extent as of September 14, 2015, along with daily ice extent data for last year and the three lowest ice extent years (2012, 2007, and 2011).

Figure 2a. The graph above shows Arctic sea ice extent as of September 14, 2015, along with daily ice extent data for last year and the three lowest ice extent years (2012, 2007, and 2011). 2015 is shown in blue, 2014 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. About the data

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

This year’s minimum was 1.02 million square kilometers (394,000 square miles) above the record minimum extent in the satellite era, which occurred on September 17, 2012, and 1.81 million square kilometers (699,000 square miles) below the 1981 to 2010 average minimum.

Figure 2b. This figure shows patterns of sea level pressure and air temperature at the 925 hPa level for the summers (June through August) of 2015 and for 2007, expressed as differences with respect to average conditions over the period 1981 to 2010.

Figure 2b. This figure shows patterns of sea level pressure and air temperature at the 925 hPa level for the summers (June through August) of 2015 and for 2007, expressed as differences from the 1981 to 2010 average. The patterns for 2015 contributed to low September extent, but were not as favorable for producing low extent as the patterns seen in 2007.

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

Research has shown that especially low September sea extent tends to occur in years when the summer atmospheric circulation over the central Arctic Ocean is dominated by high atmospheric pressure, or anticyclonic conditions. This is because anticyclonic conditions tend to bring relatively sunny and warm conditions, and a clockwise wind pattern promotes ice convergence, making for a more compact, and thus smaller ice cover. The best example of this pattern occurred during the summer of 2007, which had the second lowest September extent in the satellite record. Conversely, Septembers with high extent tend to occur when the atmospheric circulation over the central Arctic Ocean is more cyclonic (counterclockwise), meaning unusually low pressure at the surface. This pattern brings more clouds, lower temperatures, and winds that spread the ice over a larger area.

Viewed in this framework, the pattern of atmospheric circulation for summer 2015 as a whole (June through August) favored a low September extent. Sea level pressures were higher than average over the central Arctic Ocean, as well as over Greenland and the surrounding region. Pressures were below average over north-central Eurasia. This was associated with air temperatures at the 925 hPa level (about 3,000 feet above the surface) that were above average over much of the Arctic Ocean, especially along the coast of eastern Siberia, in the Laptev Sea, and the Canadian Arctic Archipelago extending to the pole. However, it was not nearly as favorable as the 2007 pattern, when the area of unusually high pressure was located further south and east (over the northern Beaufort Sea), and unusually low pressure extended along much of the coast of northern Eurasia. This led to a pattern of warm winds from the south over the East Siberian and Chukchi Seas, promoting strong melt and transport of ice away from the coast. For both 2015 and 2007, the summer pressure patterns led to winds directed down the Fram Strait, helping to transport ice out of the Arctic Ocean into the East Greenland Sea.

Varying distribution of ice in 2015 versus 2012

Figure 3. This image compares differences in ice-covered areas between September 11, 2015 and September 17, 2012, the record low minimum extent.

Figure 3. This image compares differences in ice-covered areas between September 11, 2015 and September 17, 2012, the record low minimum extent. Light blue shading indicates the region where ice occurred in both 2015 and 2012, while white and medium blue areas show ice cover unique to 2012 and to 2015, respectively. Sea Ice Index data. About the data

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

While minimum extent was higher this year compared to 2012, there are many similarities in the spatial pattern of the ice cover. Both years had considerable ice loss in the Beaufort, Chukchi, and East Siberian seas, though this year the ice extent did not retreat as far north as in 2012. Both also show a tongue of ice extending further southward on the Siberian side of the Arctic. In 2012, the tongue extended toward the Laptev Sea. This year, the tongue is farther east, in the western part of the East Siberian Sea, and is related to thicker, older ice that did not melt completely. North of Svalbard and in the Kara Sea, sea ice extent was slightly higher this year than in 2012.

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
2006 5.77 2.28 September 17
2007 4.15 1.60 September 18
2008 4.59 1.77 September 20
2009 5.12 1.98 September 13
2010 4.61 1.78 September 21
2011 4.34 1.67 September 11
2012 3.39 1.31 September 17
2013 5.05 1.95 September 13
2014 5.03 1.94 September 17
2015 4.41 1.70 September 11
1979 to 2000 average 6.70 2.59 September 13
1981 to 2010 average 6.22 2.40 September 15

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

Table 2.  Ten lowest minimum Arctic sea ice extents (1981 to 2010 average)
 RANK  YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
1 2012 3.39 1.31 September 17
2 2007 4.15 1.60 September 18
3 2011 4.34 1.67 September 11
4 2015 4.41 1.70 September 11
5 2008 4.59 1.77 September 20
6 2010 4.61 1.78 September 21
7 2014 5.03 1.94 September 17
8 2013 5.05 1.95 September 13
9 2009 5.12 1.98 September 13
10 2005 5.32 2.05 September 22

Note that the dates and extents of the minima have been re-calculated from what we posted in previous years. In March 2015, NSIDC made two revisions to Arctic Sea Ice Index extent values used in our analyses, to improve scientific accuracy. These changes do not significantly affect sea ice trends and year-to-year comparisons, but in some instances users may notice very small changes in values from the previous version of the data. First, calculations of ice extent near the North Pole were improved whenever a newer satellite orbited closer to the pole than older satellites in the series, by using a sensor-specific pole hole for the extent calculations. Second, the accuracy of ice detection near the ice edge was slightly improved by adopting an improved residual weather effect filter. Details on the changes are discussed in the Sea Ice Index documentation.

U.S. icebreaker reaches the North Pole

Figure 4. Scientists and the crew of U.S. Coast Guard Icebreaker Healy have their portrait taken at the North Pole on September 7, 2015.

Figure 4. Scientists and the crew of U.S. Coast Guard Icebreaker Healy have their portrait taken at the North Pole on September 7, 2015. The Healy reached the pole on September 5.

Credit: U.S. Coast Guard photo by Petty Officer 2nd Class Cory J. Mendenhall
High-resolution image

After four weeks at sea, the Coast Guard Icebreaker Healy reached the North Pole on September 5. The ship left Dutch Harbor on August 9 with about 145 people on board, including about fifty scientists. The Healy is a medium-duty icebreaker and in the years past would not have been suitable to navigate through thick ice floes to reach the pole. This is the first time that a U.S. ship has made a solo traverse of the North Pole. As clear evidence that the melt season was coming to a close, air temperatures were 21 degrees Fahrenheit (-6 degrees Celsius). The U.S. icebreaker’s capability is far behind that of Russia and other Arctic nations, and plans are ongoing for the U.S. to build a new polar-class icebreaking vessel.

Impact of sea ice convergence in 2013

Figure 5. These graphs show onshore ice drift during the summer of 2013.

Figure 5. These graphs show onshore ice drift during the summer of 2013. Due to ice convergence, an ice area in May (in red) is compressed by ~23% by the end of the summer (dashed line).

Credit: Ron Kwok, NASA Jet Propulsion Laboratory
High-resolution image

Thick, deformed ice, made up of pressure ridges with deep keels, is formed when the sea ice cover is pushed against or converges on the coast. Sea ice convergence along the coasts of Greenland and the Canadian Arctic Archipelago is a source of the thickest ice (tens of meters) in the Arctic Ocean. The thicker ice is more likely to survive the summer to form the Arctic Ocean’s perennial ice cover. A new paper by Ron Kwok at the NASA Jet Propulsion Laboratory shows that in summer of 2013, strong wind-driven onshore ice drift was forced by the relative location of high- and low- pressure centers over the Arctic Ocean (see Figure 5). A sampled ice parcel (in red) shows an area compression of 23% between May and October; the dashes indicate its area by end of summer. This is equivalent to an increase in thickness of ~30% within that area. If this thicker ice were transported to areas of high melt rates (like that in the southern Beaufort), it would have an impact on summer ice coverage. The presence of a band of sea ice that survived a large part of the summer in 2015, is likely due to the thicker ice that formed in this region.

Reference

Kwok, R. 2015. Sea ice convergence along the Arctic coasts of Greenland and the Canadian Arctic Archipelago: Variability and extremes (1992–2014). Geophysical Research Letters, (Accepted) doi:10.1002/2015GL065462.

Arctic openings

Arctic sea ice extent is now tracking below 2010, 2013, and 2014. Openings in the ice cover have continued to expand within the Beaufort and Chukchi seas. While the Northern Sea Route has opened, the Northwest Passage remains clogged with considerable ice in the channels of the Canadian Archipelago. However, some data sources indicate narrow openings in the ice where navigation may be possible.

Overview of conditions

Figure 1. Arctic sea ice extent for August 16, 2015 was 5.79 million square kilometers (2.24 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

Figure 1. Arctic sea ice extent for August 16, 2015 was 5.79 million square kilometers (2.24 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 August 16, 2015 sea ice extent stood at 5.79 million square kilometers (2.24 million square miles). This is 1.35 million square kilometers (521,200 square miles) below the 1981 to 2010 average, and 1.17 million square kilometers (451,700 square miles) above the level for the same date in 2012, the year of the record low extent.

The rate of ice retreat slowed compared to July, but remained faster than is typical for the month through the first half of August. Most of the ice in Baffin and Hudson bays has finally melted out. Large areas of open water and low concentration ice within the Beaufort and Chukchi seas continued to expand. Some of the low concentration ice depicted in the passive microwave data could be due to the presence of melt ponds on higher concentration ice. However, visible imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on the NASA Terra and Aqua satellites confirm a very loose ice pack with considerable open water in the region. Most of the remaining ice appears to be fairly thick multiyear floes interspersed by thinner first-year ice that is rapidly melting out. In the eastern Arctic, the ice pack remains more consolidated.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 16, 2015, along with daily ice extent data for 2014, 2013, 2012, and 2010. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2010 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 2. The graph above shows Arctic sea ice extent as of August 16, 2015, along with daily ice extent data for 2014, 2013, 2012, and 2010. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2010 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

Atmospheric temperatures at the 925 millibar level during the first half of August were above average over the North Pole region and the Barents and Kara seas, but below average in the Laptev, East Siberian, Beaufort and Chukchi seas. This is a notable change from July, when above-average temperatures prevailed over most of the Arctic Ocean, including much of the Beaufort and Chukchi seas. Current conditions are likely due to a shift in atmospheric circulation from the July pattern of high sea level pressure centered roughly over the pole to a pattern of high pressure centered over the Kara and Laptev seas, and low pressure centered over the eastern Beaufort Sea. This low pressure brought colder air from the north into the western Beaufort Sea and the Chukchi Sea, and generally cloudier conditions to the region.

Forecasting the seasonal minimum

Figure 3. The above graph shows a forecast of mean probabilistic Arctic sea ice extent for September 2015 (issued August 9, 2015). ||Credit: Andrew Slater, National Snow and Ice Data Center|High-resolution image

Figure 3. The above graph shows a forecast of mean probabilistic Arctic sea ice extent for September 2015 (issued August 9, 2015). The forecast value, or expected September mean Arctic sea ice extent, is 4.55+/-0.35 million square kilometers.


Credit: Andrew Slater, National Snow and Ice Data Center.
High-resolution image

Several methods have been developed to make predictions of the September minimum in Arctic sea ice extent. NSIDC research scientist Andrew Slater developed a method that uses a statistical approach to calculate the probability of ice being present at each location (i.e., at each grid cell). The method correlates ice concentration at the time the forecast is made (issue date) with concentration at a desired later time (forecast); the difference between those two times or dates is known as the lead-time. While not as sophisticated as approaches using coupled ocean-ice-atmosphere models, this statistical method has the advantage that the forecasts for all points are completely independent in both space and time; that is, the forecast at any given point is not affected by its neighbors, nor its result from the prior day. Forecast skill improves as lead-time decreases.

The model has performed well compared to forecasts submitted to the Sea Ice Outlook prediction network. For example, the years 2005, 2007, and 2012 were correctly predicted as being record breaking (at the time) 50 days in advance. September average extent at 50-days lead time has been predicted to within 100,000 square kilometers (2009, 2010, 2011), but has also been as far off as 600,000 square kilometers (2007, 2008). Forecasting at seasonal time scales is difficult, but the model does have genuine skill in September (using a metric of comparison of the forecast error variance with the historically observed [de-trended] variance as was used in Schröder et al, [2014]) at lead times as long as ninety days.

A passage to India by way of Russia

Figure 4. The image above shows Arctic sea ice extent on August 16, 2015 from the Multisensor Analyzed Sea Ice Extent (MASIE) data product.||Credit: National Snow and Ice Data Center|  High-resolution image

Figure 4. The image above shows Arctic sea ice extent on August 16, 2015 from the Multisensor Analyzed Sea Ice Extent (MASIE) data product.

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

The Northern Sea Route along the Russian coast appears to be open, both in the passive microwave imagery and in the Multisensor Analyzed Sea Ice Extent (MASIE) product that is more adept at detecting thin and deteriorating ice. MASIE still shows considerable ice north of the Taymyr Peninsula and the Severnaya Zemlya islands, but there is a narrow open water passage through the ice. On the other side of the Arctic, the Northwest Passage still contains a considerable amount of ice. According to MASIE, there is as yet no completely open route. Some passive microwave products, such as from the University of Bremen’s Advanced Microwave Scanning Radiometer 2 (AMSR2), indicate an open water route along Norwegian explorer Roald Amundsen’s historical route through the southern part of the Archipelago. The apparent discrepancy between MASIE and the Bremen product is likely due to thin, heavily melting ice not detected by passive microwave imagery.

A change in Antarctic sea ice

Figure 5a. The graph above shows Antarctic sea ice extent as of August 17, 2015, along with daily ice extent data for the record low year. 2015 is shown in blue and 2012 in green. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 5a. The graph above shows Antarctic sea ice extent as of August 17, 2015, along with daily ice extent data for the record low year. 2015 is shown in blue and 2012 in green. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

Figure 5b. The above images compare Antarctic sea ice concentration for August 1, 2015 and August 16, 2015. Data are from the Advanced Microwave Scanning Radiometer 2 (AMSR2) sensor on the Global Change Observation Mission 1st - Water (GCOM-W1) satellite.||Credit: Institute of Environmental Physics, University of Bremen| High-resolution image

Figure 5b. The above images compare Antarctic sea ice concentration for August 1, 2015 and August 16, 2015. Data are from the Advanced Microwave Scanning Radiometer 2 (AMSR2) sensor on the Global Change Observation Mission 1st – Water (GCOM-W1) satellite.

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

Growth in Antarctic sea ice extent has leveled off, increasing by just 250,000 square kilometers (96,500 square miles) between August 1 and August 17. This slow rate of growth has brought this year’s sea ice extent to below the 1981 to 2010 average for the first time in nearly four years. Figure 5b shows ice retreat around the Antarctic Peninsula, in the Ross Sea, and around the coast of Wilkes Land. These areas of retreat are offset by some ice growth in the northern Amundsen Sea and off the coast of Enderby Land.

Downwardly mobile

Arctic sea ice extent for June 2015 was the third lowest in the satellite record. June snow cover for the Northern Hemisphere was the second lowest on record. In contrast, Antarctic sea ice extent remained higher than average. The pace of sea ice loss was near average for the month of June, but persistently warm conditions and increased melting late in the month may have set the stage for rapid ice loss in the coming weeks. 

Overview of conditions

Figure 1. Arctic sea ice extent for June 2015 was 11.0 million square kilometers (4.24 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 June 2015 was 11.0 million square kilometers (4.24 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 June 2015 averaged 11.0 million square kilometers (4.24 million square miles), the third lowest June extent in the satellite record. This is 920,000 square kilometers (355,200 square miles) below the 1981 to 2010 long-term average of 11.89 million square kilometers (4.59 million square miles) and 150,000 square kilometers (58,000 square miles) above the record low for the month observed in 2010.

Ice extent remains below average in the Barents Sea as well as in the Chukchi Sea, continuing the pattern seen in May. While extent is below average in western Hudson Bay, it is above average in the eastern part of the bay and near average east of Greenland.

Ice loss typically quickens in June with the largest loss rate occurring in July, the warmest month of the year. A total of 1.61 million square kilometers (622,000 square miles) of ice was lost through the month, slightly slower than the 1981 to 2010 average rate of decline of 1.69 million square kilometers (653,000 square miles). By the end of the month, ice extent for the Arctic tracked within one standard deviation of the 1981 to 2010 average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July 5, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 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 July 5, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 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

June 2015 was fairly warm in the Arctic. Air temperatures at the 925 millibar level (about 3,000 feet above the surface) were above average over much of the Arctic Ocean, notably in the Kara Sea (2 to 5 degrees Celsius or 4 to 9 degrees Fahrenheit above average) and in the East Siberian Sea (2 to 3 degrees Celsius or 4 to 5 degrees Fahrenheit above average).

Figure 2b. The plot shows Antarctic air temperature anomalies at the 925 hPa level in degrees Celsius for June 2015. Yellows and reds indicate higher than average temperatures; blues and purples indicate lower than average temperatures.||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division|  High-resolution image

Figure 2b. The plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for June 2015. 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

The especially warm conditions in the Kara Sea, where ice extent is below average, is consistent with a wind pattern tending to bring in warm air from the south. The wind flows along the northern flank of a low-pressure area centered over the Barents Sea. Northerly winds on the western side of this low-pressure area brought cool conditions to the Norwegian Sea. Temperatures in the northern and eastern Beaufort Sea and much of the Canadian Arctic Archipelago were near or slightly below average.

June 2015 compared to previous years

Figure 3. Monthly June ice extent for 1979 to 201X shows a decline of 3.6% per decade relative to the 1981 to 2010 average.||Credit: National Snow and Ice Data Center|  High-resolution image

Figure 3. Monthly June ice extent for 1979 to 2015 shows a decline of 3.6% per decade relative to the 1981 to 2010 average.

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

Arctic sea ice extent averaged for June 2015 was the third lowest in the satellite record. Through 2015, the linear rate of decline for June extent is 3.6 % per decade.

Northern Hemisphere snow cover

Figure 4a. This snow cover anomaly map shows the difference between snow cover for June 2015, compared with average snow cover for June from 1981 to 2010. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than normal.||Credit: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab|  High-resolution image

Figure 4a. This snow cover anomaly map shows how snow cover for June 2015 differs from the average snow cover for June from 1981 to 2010. Areas in orange and red indicate lower than average 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 4b. This graphs shows snow cover extent anomalies in the Northern Hemisphere for June from 1967 to 2015. The anomaly is relative to the 1981 to 2010 average.||Credit: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab|  High-resolution image

Figure 4b. The graphs shows snow cover extent anomalies in the Northern Hemisphere for June from 1967 to 2015. The anomaly is relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab
High-resolution image

June snow cover for the Northern Hemisphere averaged 5.45 million square kilometers (2.10 million square miles), the second lowest of the 48-year record. This ranking also holds for June snow cover assessed for North America at 4.09 million square kilometers (1.58 million square miles) and Eurasia at 1.36 million square kilometers (525,000 square miles).

June snow cover was especially low over Alaska and western Canada. This is in part related to last winter’s unusual jet stream pattern, discussed in our March post. The pattern brought unusually warm conditions to the region and promoted low sea ice extent to the Bering Sea and Sea of Okhotsk. Recall that the restart of the Iditarod Race had to be moved from Anchorage to Fairbanks because of poor snow conditions in the Alaska Range. This spring has also been warm and dry in Alaska. These conditions have contributed to a large number of lightning-induced wildfires in the state.

Sea ice loss and snowfall over Eurasia

Climate models predict that Arctic precipitation will increase through the 21st century. As the climate warms, the atmosphere can hold more moisture, which means a greater poleward transport and convergence of moisture by the atmosphere. The decline in Arctic sea ice extent may also play a role, as more open water will provide a moisture source. One would expect this latter effect to be most pronounced in autumn, when there will be a strong temperature (hence moisture) contrast between the open water and overlying air, promoting strong evaporation into the atmosphere. A recent study by Wegmann et al. provides evidence that more open water in the Barents and Kara seas has indeed led to an increase in autumn snowfall over Eurasia. Their analysis is based on snow observations from over 800 Russian land stations and an analysis of atmospheric moisture transport.

Sea ice in Antarctica

Figure 5. Antarctic sea ice extent for June 2015 was 14.9 million square kilometers (5.76 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

Figure 5. Antarctic sea ice extent for June 2015 was 14.9 million square kilometers (5.76 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

Sea ice extent in Antarctica averaged 14.93 million square kilometers (5.76 million square miles), the third highest June extent in the satellite record. Extent was slightly greater than the 1981 to 2010 average almost everywhere around the continent. The high amount of sea ice in the eastern Weddell and Ross seas is consistent with the pattern observed for the past several months.

Satellite data show unusually extensive sea ice growth along the western side of the Antarctic Peninsula. This new feature in sea ice growth could be influenced by the strong atmospheric wave-3 pattern that has persisted over the past few months. In a wave-3 pattern, there are three major low-pressure areas around the continent separated by three high-pressure areas. The low-pressure areas have been centered on the Antarctic Peninsula, the northwestern Ross Sea, and the eastern Weddell Sea.

Further reading

Wegmann, M., Y. Orsolini, M. Vasquez, L. Gimeno, R. Nieto, O. Bulygina, R. Jaiser, D. Handorf, A. Rinke, K. Dethloff, A. Sterin, and S. Bronnimann. 2015. Arctic moisture source for Eurasian snow cover variations in autumn. Environmental Research Letters, 10, doi: 10.1088/1748-9326/10/054015.

Third dimension: new tools for sea ice thickness

As winter turns to spring, the seasonal decline in Arctic sea ice kicks into gear. April was marked by rapid ice loss at the beginning and end of the month. Air temperatures were higher than average over much of the Arctic Ocean. In the Antarctic, sea ice extent was the highest seen in April in the satellite record. This month we introduce data sets and online tools from new sensors that—combined with older sources—provide a more complete picture of ice thickness changes across the Arctic.

Overview of conditions

Figure 1. Arctic sea ice extent for April 2015 was 14.0 million square kilometers (5.0 million square miles).

Figure 1. Arctic sea ice extent for April 2015 was 14.0 million square kilometers (5.4 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 April 2015 averaged 14.0 million square kilometers (5.4 million square miles), the second lowest April ice extent in the satellite record. It is 810,000 square kilometers (313,000 square miles) below the 1981 to 2010 long-term average of 15.0 million square kilometers (6.0 million square miles) and 80,000 square kilometers (31,000 square miles) above the previous record low for the month observed in 2007.

Ice extent remained below average in the Barents Sea, the Sea of Okhotsk, and the Bering Sea. Sea ice was slightly more extensive than average off Newfoundland, in the Davis Strait, and in the Labrador Sea. The Labrador Sea is an important breeding area for harp and hooded seals in early spring. More extensive ice in this region favors more seal cubs being fully weaned before the ice breaks up, increasing their chance of survival.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of May 5, 2015, along with daily ice extent data for four previous years.

Figure 2. The graph above shows Arctic sea ice extent as of May 5, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 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

During April, the decline in ice extent starts to accelerate, though the total ice loss over the month is generally small. April 2015 was marked by a fairly rapid decline during the first week of the month, little change during the middle of the month, and then a steep decline over the final week. Overall, extent decreased 862,000 square kilometers (333,000 square miles).

April was marked by higher than average 925 hPa air temperatures (1 to 3 degrees Celsius or 2 to 5 degrees Fahrenheit) throughout the Arctic, except for Greenland and the Canadian Archipelago where temperatures were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) below average. Temperatures were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) higher than average in the Kara Sea, linked to unusually low sea level pressure over the North Atlantic. Associated wind patterns also resulted in strong warming over the Eurasian Arctic.

April 2015 compared to previous years

Figure 3. Monthly April ice extent for 1979 to 2015 shows a decline of 2.4% per decade relative to the 1981 to 2010 average.

Figure 3. Monthly April ice extent for 1979 to 2015 shows a decline of 2.4% per decade relative to the 1981 to 2010 average.

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

Arctic sea ice extent averaged for April 2015 was the second lowest in the satellite record for the month. Through 2015, the linear rate of decline for April extent is 2.4% per decade.

New data on sea ice thickness

Figure 4. This map shows sea ice thickness in meters in the Arctic Ocean from March 29, 2015 to April 25, 2015. ||Credit: Center for Polar Observation and Modelling, University College London|  High-resolution image

Figure 4. This map shows sea ice thickness in meters in the Arctic Ocean from March 29, 2015 to April 25, 2015.

Credit: Center for Polar Observation and Modelling, University College London
High-resolution image

Data from new sensors, combined with older sources, are providing a more complete picture of ice thickness changes across the Arctic. In a recently published paper, R. Lindsay and A. Schweiger provide a longer-term view of ice thickness, compiling a variety of subsurface, aircraft, and satellite observations. They found that ice thickness over the central Arctic Ocean has declined from an average of 3.59 meters (11.78 feet) to only 1.25 meters (4.10 feet), a reduction of 65% over the period 1975 to 2012.

In addition, near-real-time thickness data from the European Space Agency’s CryoSat-2 satellite are now available from the Centre for Polar Observation and Modelling at the University College London. The spatial pattern of ice thickness in spring is a key factor in the evolution of sea ice through the Arctic summer, and CryoSat-2 data bring the promise of regular sea ice thickness monitoring over most of the Arctic Ocean.

The data indicate that Arctic sea ice thickness in the spring of 2015 is about 25 centimeters (10 inches) thicker than in 2013. Ice more than 3.5 meters (11.5 feet) thick is found off the coast of Greenland and the Canadian Archipelago, and scattered regions of 3-meter (10 feet) thick ice extend across the Beaufort and Chukchi seas. Elsewhere, most of the ice is 1.5 to 2.0 meters (4.9 to 6.6 feet) thick, typical for first-year ice at the end of winter.

Older ice spreads out

Figure 5. These ice age maps show a change in distribution of older ice from just after the summer 2014 melt season (left) and the end of March 2015 (right). ||Credit: NSIDC courtesy J. Maslanik and M. Tschudi, University of Colorado|  High-resolution image

Figure 5. These ice age maps show a change in distribution of older ice from just after the summer 2014 melt season (left) and the end of March 2015 (right).

Credit: NSIDC courtesy J. Maslanik and M. Tschudi, University of Colorado Boulder
High-resolution image

Thickness estimates from CryoSat-2 data and the Lindsay and Schweiger analysis agree well with reconstructions based on sea ice age produced at the University of Colorado Boulder. Since ice gets thicker as it survives several melt seasons, ice age is a good proxy for thickness. For example, the ice thickness map from CryoSat-2 (Figure 4) and the ice age map (Figure 5) both show increased ice thickness in the southern Beaufort Sea where there was a transport of 5+ year old ice this winter. Interestingly, the ice age map identifies the tongue of ice extending towards the New Siberian Islands as second-year ice, yet the ice thickness map shows that its thickness is more similar to first-year ice.

Arctic sea ice age data are now publicly available from NSIDC and can be viewed interactively on the NSIDC Satellite Observations of Arctic Change Web site. Data are currently available through December 2012.

After the 2014 September minimum, first-year ice expanded through the winter growth season and older ice was redistributed around the Arctic Ocean. Figure 5 shows that winds have compressed second-year ice towards the coast of Greenland and the Canadian Archipelago. Old multi-year ice (4+ years old) drifted into the Beaufort and Chukchi seas and spread out, with first-year ice forming between parcels of the older ice. Some of the multi-year ice (both second-year and older) drifted out of the Arctic through Fram Strait on its way to melting in the warm waters of the North Atlantic.

Overall, the area of second-year ice decreased by more than a third during the winter, while ice of four years and more declined by about 10%. In recent years, the Beaufort and Chukchi seas have seen substantial loss of ice during summer, even of the thicker, older ice.

Antarctica reaches record ice extent, but temperature trends vary

Figure 6. The graph above shows Antarctic sea ice extent as of May 5, 2015, along with daily ice extent data for four previous years.

Figure 6. The graph above shows Antarctic sea ice extent as of May 5, 2015, along with daily ice extent data for four previous years. 2015 is shown in blue, 2014 in green, 2013 in orange, 2012 in brown, and 2011 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

Antarctic sea ice extent averaged 9.06 million square kilometers (3.5 million square miles) for the month and is now the highest April extent in the satellite record. April extent was 300,000 square kilometers (116,000 square miles) higher than the previous record observed in 2014, and 1.70 million square kilometers (656,000 square miles) above the 1981 to 2010 long-term average. The Antarctic April extent was also above the two standard deviations of the long-term average.

The high sea ice extent in the Antarctic was a result of above-average extent in the Weddell Sea, and slightly more expansive ice cover in the Ross Sea. Interestingly, 925 hPa air temperatures over a wide area in the Weddell Sea were 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) above average for the month of April. Lower-than-average air temperatures (1 to 4 degrees Celsius or 2 to 7 degrees Fahrenheit below average) were found in the Ross Sea, but only in the far west and not near the regions of record ice extent. While there remains considerable year-to-year variability of sea ice extent in the Antarctic, the trend in April sea ice extent for the Antarctic from 1979 to 2015 now stands at 4.1% per decade.

References

Lindsay, R. and A. Schweiger. 2015. Arctic sea ice thickness loss determined using subsurface, aircraft, and satellite observations. The Cryosphere, 9, 269-283, doi:10.5194/tc-9-269-2015, 2015.

Tschudi, M., C. Fowler, and J. Maslanik. 2014. EASE-Grid Sea Ice Age. Boulder, Colorado USA: NASA National Snow and Ice Data Center Distributed Active Archive Center, doi:10.5067/1UQJWCYPVX61.

Arctic sea ice reaches lowest maximum extent on record

On February 25, 2015, Arctic sea ice extent appeared to have reached its annual maximum extent, marking the beginning of the sea ice melt season. This year’s maximum extent not only occurred early; it is also the lowest in the satellite record. However, a late season surge in ice growth is still possible. NSIDC will post a detailed analysis of the 2014 to 2015 winter sea ice conditions in early April.

Overview of conditions

Figure 1. Arctic sea ice extent for February 25, 2015

Figure 1. Arctic sea ice extent for February 25, 2015 was 14.54 million square kilometers (5.61 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 February 25, 2015 Arctic sea ice likely reached its maximum extent for the year, at 14.54 million square kilometers (5.61 million square miles). This year’s maximum ice extent was the lowest in the satellite record, with below-average ice conditions everywhere except in the Labrador Sea and Davis Strait. The maximum extent is 1.10 million square kilometers (425,000 square miles) below the 1981 to 2010 average of 15.64 million square kilometers (6.04 million square miles) and 130,000 square kilometers (50,200 square miles) below the previous lowest maximum that occurred in 2011. This year’s maximum occurred 15 days earlier than the 1981 to 2010 average date of March 12. The date of the maximum has varied considerably over the years, occurring as early as February 24 in 1996 and as late as April 2 in 2010.

Because of the variability of ice extent at this time of year, there can be some delay in pinpointing the date of the maximum extent, as was true this year. NSIDC calculates daily ice extent as an average of the previous five days (see the Sea Ice Index documentation for more information), and we also look for a clear downward trend for a number of days.

While the downturn in extent was quite pronounced on February 25, the trend subsequently flattened. This is in part due to recent ice growth in the Bering Sea, partly balancing continued ice retreat in the Barents and Kara seas. Over the next two to three weeks, periods of increase are still possible. However, it now appears unlikely that there could be sufficient growth to surpass the extent reached on February 25.

Conditions in context

Arctic sea ice extent as of March 18, 2015

Figure 2. The graph above shows Arctic sea ice extent as of March 18, 2015, along with daily ice extent data for four previous years. 2014 to 2015 is shown in blue, 2013 to 2014 in green, 2012 to 2013 in orange, 2011 to 2012 in brown, and 2010 to 2011 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

Over the 2014 to 2015 winter season, sea ice extent grew 9.91 million square kilometers (3.83 million square miles). This was substantially less ice growth than last year, which saw record growth over the winter. Part of the explanation for the record low maximum lies with recent weather patterns. As discussed in our previous post, February was characterized by an unusual configuration of the jet stream, leading to warm conditions over the Pacific side of the Arctic that maintained low sea ice extent in the Bering Sea and the Sea of Okhotsk. Furthermore, since the last half of February through the middle of March, the Arctic Oscillation was in a strongly positive phase, with index values exceeding 5.0 for several days in the first week of March. This has been expressed as a strong Icelandic Low, a semi-permanent area of low atmospheric pressure found between Iceland and southern Greenland and extending into the Barents Sea. The strong Icelandic Low led to a pattern of surface winds over the Barents and Kara seas with an unusually strong component from the south.

Over the first two weeks of March, temperatures throughout the eastern Arctic at the 925 hPa level (approximately 3,000 feet altitude) were several degrees Celsius above average, with temperatures as much as 8 to 10 degrees Celsius (14 to 18 degrees Fahrenheit) above average in the Barents Sea between Svalbard and Franz Josef Land.

While the seven-day weather forecasts show continued warmer-than-average conditions over the eastern Arctic, colder-than-average conditions are expected over the Bering Sea and may still lead to some new ice formation. Thus, while the maximum appears to have occurred on February 25, late season ice growth may still occur.

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.

Updates to the Sea Ice Index

Recently, NSIDC made two revisions to Arctic Sea Ice Index extent values used in our analyses, to improve scientific accuracy. These changes do not significantly affect sea ice trends and year-to-year comparisons, but in some instances users may notice very small changes in values from the previous version of the data. First, calculations of ice extent near the North Pole were improved whenever a newer satellite orbited closer to the pole than older satellites in the series, by using a sensor-specific pole hole for the extent calculations. Second, the accuracy of ice detection near the ice edge was slightly improved by adopting an improved residual weather effect filter. Details on the changes are discussed in the Sea Ice Index documentation.

Possibly low maximum in the north, a high minimum in the south

Arctic sea ice extent continues to track well below average, but it is still unclear whether March will see an increase in ice, or establish a record low maximum. Regionally, Arctic ice extent is especially low in the Sea of Okhotsk and the Bering Sea. In the Antarctic, sea ice shrank to the fourth highest minimum in the satellite record.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2015

Figure 1. Arctic sea ice extent for February 2015 was 14.41 million square kilometers (5.56 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 in February averaged 14.41 million square kilometers (5.56 million square miles). This is the third lowest February ice extent in the satellite record. It is 940,000 square kilometers (362,900 square miles) below the 1981 to 2010 long-term average of 15.35 million square kilometers (5.93 million square miles). It is also 50,000 square kilometers (19,300 square miles) above the record low for the month observed in 2005.

With the Arctic Ocean completely ice covered, the remaining areas of potential new ice growth are limited to the margins of the pack in the northern Pacific and northern Atlantic. Sea ice extent is below average across the entire sea ice margin, most prominently along the Pacific sectors. A small region of above-average ice extent is located near Newfoundland and the Canadian Maritime Provinces.

The Arctic maximum is expected to occur in the next two or three weeks. Previous years have seen a surge in Arctic ice extent during March (e.g., in 2012, 2014). However, if the current pattern of below-average extent continues, Arctic sea ice extent may set a new lowest winter maximum.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 2, 2015, along with daily ice extent data for four previous years

Figure 2. The graph above shows Arctic sea ice extent as of March 2, 2015, along with daily ice extent data for four previous years. 2014 to 2015 is shown in blue, 2013 to 2014 in green, 2012 to 2013 in orange, 2011 to 2012 in brown, and 2010 to 2011 in purple. The 1981 to 2010 average is in dark gray. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

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

Arctic sea ice extent increased by 429,000 square kilometers (165,600 square miles) during the month of February. This gain was slightly less than the average for the month. While low extent for the Arctic as a whole was largely driven by conditions in the Sea of Okhotsk and the Bering Sea, extent was also slightly below average along the Barents Sea and parts of the East Greenland Sea.

February 2015 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2015 shows a decline of 2.9% per decade relative to the 1981 to 2010 average.

Figure 3. Monthly February ice extent for 1979 to 2015 shows a decline of 2.9% per decade relative to the 1981 to 2010 average.

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

The monthly average Arctic sea ice extent for February was the third lowest in the satellite record. Through 2015, the linear rate of decline for February extent is 2.9% per decade.

Hot Bering(s)

Figure 4. The plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for February 2015.

Figure 4. The plot shows Arctic air temperature anomalies at the 925 hPa level in degrees Celsius for February 2015. 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

The low ice extent in the Bering Sea and Sea of Okhotsk is linked to unusually warm conditions in the area. February air temperatures at the 925 hPa level were as much as 4 to 6 degrees Celsius (7 to 11 degrees Fahrenheit) above average in the northern Bering Sea, easternmost Siberia, and Sea of Okhotsk.

While these localized hotspots are in part driven by the low sea ice extent and the resulting large heat fluxes from the open water to the atmosphere, they are seen to be part of a broad area of unusually warm conditions extending across most of northern Eurasia, across Alaska, and into the western part of the United States. In contrast, cold and snowy conditions have persisted across the eastern half of North America. Broadly speaking, these opposing patterns of warmth and cold, along with low ice extent in the Sea of Okhotsk and Bering Sea, can be linked to an unusual jet stream pattern, with the jet lying north of its usual location over Eurasia and the North Pacific (meaning that warm air extends further north than is usual), and then plunging southwards over eastern North America.

Snow cover

Figure 5a. This snow cover anomaly map shows the difference between snow cover for February 2015, compared with average snow cover for February from 1981 to 2010.

Figure 5a. This snow cover anomaly map shows the difference between snow cover for February 2015, compared with average snow cover for February from 1981 to 2010. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than normal.

Credit: National Snow and Ice Data Center, courtesy Rutgers University Global Snow Lab
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Figure 5b. This graphs shows snow cover extent anomalies in the Northern Hemisphere for February from 1967 to 2015.

Figure 5b. This graphs shows snow cover extent anomalies in the Northern Hemisphere for February from 1967 to 2015. 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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This unusual jet stream pattern is clearly manifested in the pattern of Northern hemisphere snow cover for February. Snow extent was well above average over the northeastern U.S. However, the western U.S. and Northern Rockies saw less snow cover than average, especially along the Pacific coast where it has been particularly warm and severely dry. While the Tibetan Plateau saw a somewhat more extensive snow cover than average in December and January, extent for Tibet and Eurasia as a whole was below average in February. Higher-than-average snow cover in the eastern U.S. expanded and became more pronounced this month as well. All of these are continuations of the basic pattern seen in December and January, although the pattern of extensive snow over the northeastern U.S. became more pronounced this month. The low snow cover extent in much of Eurasia is consistent with the warmer-than-average conditions there as described above.

Seasonal Antarctic minimum reached

Figure 6a. This figure shows the concentration anomaly for February 2015 monthly average extent relative to the 1981 to 2010 average.  Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 6a. This figure shows the concentration anomaly for February 2015 monthly average extent relative to the 1981 to 2010 average. Sea Ice Index data. About the data

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

Figure 6b. Monthly Antarctic February ice extent for 1979 to 2015 shows a trend of 5.0% per decade relative to the 1981 to 2010 average.

Figure 6b. Monthly Antarctic February ice extent for 1979 to 2015 shows a trend of 5.0% per decade relative to the 1981 to 2010 average.

Credit: National Snow and Ice Data Center
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Antarctic sea ice extent reached its annual minimum, dipping to 3.58 million square kilometers (1.38 million square miles) on February 20. This is the fourth highest summer minimum extent on record, trailing behind 2008 (3.75 million square kilometers or 1.44 million square miles, highest), 2013, and 2003. The 2014 Antarctic minimum ranked the fifth highest (3.54 million square kilometers or 1.36 million square miles). For the month as a whole, February 2015 has the sixth highest ice extent (3.8 million square kilometers or 1.46 million square miles). The sea ice extent trend for February for 1979 to 2015 shows an increase of 5.0%  per decade. However, Antarctica’s sea ice extent is highly variable. As recently as 2011, Antarctic sea ice extent was at near-record low levels for the summer minimum.

Nevertheless, the recent series of high-ice-extent minima is part of a remarkable recent uptick in extent year-round for Antarctica, dominated by extensive ice in both the Weddell Sea (south of Africa) and the Ross Sea (south of New Zealand). Sea ice in the eastern Weddell Sea presently extends several hundred kilometers further north and east of its typical extent, while ice extent in the Ross Sea is presently near average. The debate continues regarding the cause of the recent Antarctic trends, but the best explanation so far involves a combination of strengthening low pressure in the eastern Ross Sea (the Amundsen Sea Low) and the eastern Weddell Sea, and a persistently positive phase of the Southern Annular Mode. The freshening of surface seawater around Antarctica may also play a role.

Global sea ice trends

Claire Parkinson of NASA recently presented the global average (Arctic plus Antarctic) trend in sea ice extent for the period 1979 to 2013. Overall, global sea ice has declined, despite the positive trend in Antarctic extent. The annual average trend is -35,000 square kilometers (-13,500 square miles) per year, or about -1.5% per decade. The strong Arctic decline in September leads to the largest magnitude monthly trend for global sea ice in that month, at -68,000 square kilometers (-26,300 square miles) per year, or -2.6% per decade. See the NSIDC FAQ on global sea ice here.

Further reading

Parkinson, C. L. 2014. Global sea ice coverage from satellite data: annual cycle and 35-year trends. Journal of Climate, doi: 10.1175/JCLI-D-14-00605.1.

December ends, 2014 in review

Arctic sea ice extent remained about a standard deviation below average for the month of December. Compared to recent years, 2014 as a whole was rather unremarkable. The bigger story was the record high extents observed in the Antarctic through more than half of the year. At year’s end, Antarctic sea ice extent was again at a record high, but poised for a rapid decline as the austral summer wears on.

Overview of conditions

Figure 1. Arctic sea ice extent for December 2014 was 12.52 million square kilometers (4.83 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 December 2014 was 12.52 million square kilometers (4.83 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

Sea ice extent in December averaged 12.52 million square kilometers (4.83 million square miles). This is 540,000 square kilometers (208,495 square miles) below the 1981 to 2010 long-term average of 13.06 million square kilometers (5.04 million square miles) and 500,000 square kilometers (193,051 square miles) above the record low for the month observed in 2010.

Both Hudson Bay and Baffin Bay are now essentially completely ice covered. On the Atlantic side, recent winters have been characterized by reduced winter ice extent in the Kara and Barents seas. This is not the case for the winter of 2014 to 2015.

The only two regions where extent is notably below average are in the Bering Sea and the Sea of Okhotsk. This contrasts with recent winters when ice extent has been greater than average in the Bering Sea.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of January 4, 2015, along with daily ice extent data for four previous years. 2014 to 2015 is shown in blue, 2013 to 2014 in green, 2012 to 2013 in orange, 2011 to 2012 in brown, and 2010 to 2011 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 2. The graph above shows Arctic sea ice extent as of January 4, 2015, along with daily ice extent data for four previous years. 2014 to 2015 is shown in blue, 2013 to 2014 in green, 2012 to 2013 in orange, 2011 to 2012 in brown, and 2010 to 2011 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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Sea ice extent grew 2.00 million square kilometers (772,000 square miles) during the month of December. This was about average for the month. Throughout the month, daily extents were about one standard deviation below 1981 to 2010 averages. This occurred despite the fairly warm conditions over the Eurasian side of the Arctic Ocean. As averaged over the month, air temperatures at the 925 hPa level in the Laptev and East Siberian seas were up to 5 degrees Celsius (9 degrees Fahrenheit) above average, linked to a region of unusually high pressure in the region that led to southerly winds.

December 2014 compared to previous years

Figure 3. Monthly December ice extent for 1979 to 2014 shows a decline of -3.4% per decade relative to the 1981 to 2010 average. The dashed line indicates a period of missing data from December 2, 1987 through January 12, 1988. ||Credit: National Snow and Ice Data Center|  High-resolution image

Figure 3. Monthly December ice extent for 1979 to 2014 shows a decline of 3.4% per decade relative to the 1981 to 2010 average. The dashed line indicates a period of missing data from December 2, 1987 through January 12, 1988.

Credit: National Snow and Ice Data Center
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Arctic sea ice extent for December was the ninth lowest in the satellite record. Through 2014, the linear rate of decline for December extent over the satellite record is 3.4% per decade.

2014 in review

Compared to recent years, sea ice conditions observed throughout 2014 were largely unremarkable. Throughout the year, extent for the Arctic as a whole remained below average, but generally within two standard deviations of the average. The maximum extent observed on March 21 of 14.91 million square kilometers (5.76 million square miles) was the fifth lowest in the satellite record, with the minimum extent observed on September 17 of 5.02 million square kilometers (1.94 million square miles) being the sixth lowest on record. One event of note was in the Laptev Sea, where during August, open water was observed to extend to about 85 degrees latitude, less than 560 kilometers (350 miles) from the North Pole.

Summer weather conditions, which are known to strongly influence September minimum ice extent, were also largely unremarkable in 2014. Compared to the long term (1981 to 2010) climatology, sea level pressure over the period June through August 2014 was higher than average over much of the central Arctic Ocean, the Atlantic sector of the Arctic, and Greenland. While air temperatures at the 925 hPa level (approximately 3,000 feet altitude) were slightly above average over part of the central Arctic Ocean, they were below average over the Kara Sea and just north of Alaska.

By sharp contrast, sea ice in Antarctica was at satellite-era record high daily levels for much of 2014. On September 22, 2014, Antarctic ice extent reached 20.11 million square kilometers (7.76 million square miles). This was the first year in the modern satellite record that Antarctic ice extent climbed above 20 million square kilometers (7.72 million square miles).

As the year drew to a close, sea ice extent again reached record high levels for the date by declining far more slowly than usual. Extent anomalies are particularly large in the Ross Sea and Amundsen Sea regions, and in the northern Weddell Sea—areas that have been anomalously high for most of the calendar year. However, sea ice concentration in both these regions is now quite low, that is, the sea ice pack is loose and open. This is characteristic of dispersal of the ice by storms, and indeed strong low pressure anomalies were present in the eastern Ross Sea and northern Weddell Sea in the second half of December. The extent of this loose sea ice pack far to the north makes it likely that a rapid decline will occur as warmer summer weather arrives.

Losing the memory of low extent

Figure 4. This graph shows future projections of September sea ice extent under various future greenhouse gas emission levels. Limiting the warming in 2100 to about 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) under the RCP2.6 emission scenario would help to stabilize ice conditions at levels seen today. The RCP8.5 emission scenario (warming by about 4 degrees Celsius 0r 7 degrees Fahrenheit by the end of this century) would result in a seasonally ice-free Arctic by the end of this century.||Credit: Julienne Stroeve|  High-resolution image

Figure 4. This graph shows future projections of September sea ice extent under various future greenhouse gas emission levels. Limiting the warming in 2100 to about 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) under the RCP2.6 emission scenario would help to stabilize ice conditions at levels seen today. The RCP8.5 emission scenario (warming by about 4 degrees Celsius 0r 7 degrees Fahrenheit by the end of this century) would result in a seasonally ice-free Arctic by the end of this century.

Credit: Julienne Stroeve
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In September of 2014, the Royal Society of London held a workshop focused on the reduction in Arctic sea ice extent. One outcome of this meeting was a greater understanding of the overall trajectory of September ice extent. In a nutshell, it appears that very large departures from the overall downward trend in September extent are unlikely to persist into the following September. If a given September has very low ice extent, strong winter heat loss results in strong ice growth, so that the “memory” of the low ice September ice extent is lost. If a given September has a high ice extent, winter heat loss is more limited, meaning less ice growth. Consequently, while there can be large departures from year to year from the downward linear trend in ice extent (e.g., September 2012 compared to 2014), the natural tendency is for the large departure to dampen out, so that, overall, ice extent stays on the long-term downward trajectory that will eventually lead to seasonally ice free conditions as the Arctic continues to warm in response to rising atmospheric concentrations of Greenhouse gases.

Almost frozen north

Arctic sea ice continued to expand throughout the month of October, remaining at near-average levels on the Atlantic side and below average on the Pacific side. In the Southern Hemisphere, Antarctic sea ice has declined after reaching its record maximum in October and is now nearly within two standard deviations of the long-term average.

Overview of conditions

Arctic sea ice extent for October 2014 was 8.06 million square kilometers (3.11 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 October 2014 was 8.06 million square kilometers (3.11 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

Sea ice extent in October averaged 8.06 million square kilometers (3.11 million square miles). This is 850,000 square kilometers (328,000 square miles) below the 1981 to 2010 long-term average of 8.91 million square kilometers (3.44 million square miles) and 1.29 million square kilometers (498,000 square miles) above the record low for the month observed in 2007.

Arctic sea ice extent continued to increase throughout the month of October. Ice extent in the Pacific side remains below average. Areas in the Beaufort Sea along the Canadian and Alaskan coasts, and in the Chukchi Sea along the coast of Siberia were still ice free at the end of October. The image of monthly average sea ice extent (Figure 1) shows a large polynya within the East Siberian Sea, but this area is now covered by ice. On the Atlantic side, extent remains at near-average levels.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of November 3, 2014, along with daily ice extent data for four previous years. 2014 is shown in blue, 2013 in green, 2012 in orange, 2011 in brown, and 2010 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 2. The graph above shows Arctic sea ice extent as of November 3, 2014, along with daily ice extent data for four previous years. 2014 is shown in blue, 2013 in green, 2012 in orange, 2011 in brown, and 2010 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

Through the month of October, the Arctic gained 3.39 million square kilometers (1.31 million square miles) of ice. This is faster than the average rate of ice gain for the month of October, but slower than the rate of ice gain seen in October 2012, after the record minimum of September 2012, and other recent Octobers.

Temperatures at the 925 hPa level show that the Arctic was 1 to 4 degrees Celsius (2 to 7 degrees Fahrenheit) higher than average everywhere, except in the Kara and Barents seas where air temperatures were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) lower than average. Lower than average temperatures in this region were also a persistent feature of summer 2014 and helped maintain a more extensive ice cover in the region than in recent summers.

Warm conditions were partly a result of the ocean releasing the heat gained during summer back to the atmosphere. In addition, sea level pressures were higher than average over the central Arctic Ocean and the Barents Sea, reflecting the negative phase of the Arctic Oscillation .

October 2014 compared to previous years

Figure 3. Monthly October ice extent for 1979 to 2014 shows a decline of -6.9% per decade relative to the 1981 to 2010 average.||Credit: National Snow and Ice Data Center|  High-resolution image

Figure 3. Monthly October ice extent for 1979 to 2014 shows a decline of 6.9% per decade relative to the 1981 to 2010 average.

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

Due to the relatively rapid ice growth during October, Arctic sea ice extent for October 2014 was the 6th lowest in the satellite record. Through 2014, the linear rate of decline for October Arctic ice extent over the satellite record is 6.9% per decade.

Amplified autumn warming

Figure 4. This figure shows Arctic air temperature anomalies for October 2014 in degrees Celsius. The Y axis shows geopotential height. ||Credit: NOAA/ESRL Physical Sciences Division|  High-resolution image

Figure 4. This figure shows average air temperature anomalies for October 2014 at each latitude from 50 North (left side of axis) to 90 North (right side of axis). The Y axis shows air pressure in millibars, indicating height above the surface.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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Projections of climate change through the rest of the century show amplified warming in the Arctic compared to the rest of the planet. While there are a number of reasons for this, sea ice loss plays a strong role. With less ice in spring and summer, the upper ocean (the top 20 meters, or 66 feet) gains more heat through absorption of solar radiation. For the ocean surface to refreeze in autumn and winter, the ocean must first lose this extra heat. This is manifested as strong surface warming over the areas of sea ice loss during autumn. While the warming is greatest near the surface, the warming can extend to a considerable height in the atmosphere.

This October shows the expected pattern of amplified warmth. Warming was greatest near the surface at high latitudes (5 degrees Celsius, or 9 degrees Fahrenheit above average) and extended upwards to the 700 hPa level, roughly 3,000 meters (9,842 feet) above the surface. This pattern is similar to that observed in October 2007 and 2009. However, in other recent years the location of the warmest surface conditions shifted further south, or did not extend as far up in the atmosphere. Such variations point to the influence of other factors, including patterns of atmospheric circulation, cloud cover, and atmospheric humidity.

Arctic sea ice and the Madden-Julian Oscillation

Variations in large-scale atmospheric circulation patterns, such as the Arctic Oscillation , are known to affect the sea ice cover. These variations alter wind patterns that affect ice motion and bring in warm or cold air that influence ice melt and growth. For example, during a positive Arctic Oscillation phase, changes in the wind field help to push ice away from the coast of Siberia, allowing new ice to form and increasing the transport of ice out of Fram Strait. In the winters of the late 1980s and early 1990s, the Arctic Oscillation was in a persistent positive phase, helping to transport a large amount of thick, multiyear ice out of the Arctic through Fram Strait and leaving behind thinner ice that more easily melted the following summers.

A new study looks at the impact of a different mode of large-scale atmospheric variability, the Madden-Julian Oscillation, which appears to impact the ice cover on a shorter 30- to 90-day time scale. The Madden-Julian Oscillation is primarily driven by convection in the tropics, but causes changes in atmospheric circulation that impact the high latitudes. The impact on sea ice was found to be stronger during the winter season than in summer. It affected both the Atlantic and Pacific sectors and was confined to the marginal ice zone. The impact on sea ice also varies regionally, often showing opposing effects, such as between the Barents and Greenland seas in winter.

Large Antarctic sea ice variability

Figure 5. This image compares Antarctic sea ice extent for September 2014 (blue line) with extent for September 1964 (red line) and August 1966 (black line). The dotted ellipse marked A shows the eastern Weddell Sea and the dotted ellipse marked B shows the eastern Ross Sea. ||Credit: National Snow and Ice Data Center|  High-resolution image

Figure 5. This image compares Antarctic sea ice extent for September 2014 (blue line) with extent for September 1964 (red line) and August 1966 (black line). The dotted ellipse marked A shows the eastern Weddell Sea and the dotted ellipse marked B shows the eastern Ross Sea.

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

After reaching a new record maximum extent this September, Antarctic sea ice extent has quickly declined, and is now back to levels seen in 2013 at this time of year. While almost the entire perimeter of Antarctica’s sea ice retreated slightly, two regions showed a larger retreat after the maximum: the eastern Weddell Sea (dotted ellipse marked A in Figure 5) and the eastern Ross Sea (dotted ellipse marked B in Figure 5). Both were areas of unusually extensive sea ice cover, and they contributed significantly to the record-setting level of ice extent in September. Weather patterns thirty days after the maximum changed markedly, with persistent warm northerly winds in these areas. Along the continent’s Pacific coast (Ross Ice Shelf and northern West Antarctic Ice Sheet) air temperatures at the 925 hPa level were 4 to 6 degrees Celsius (7 to 11 degrees Fahrenheit) above average. In the eastern Weddell Sea south of Africa, temperatures were 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) higher than average. Moreover, a series of intense storms in the first half of October dispersed an area of sea ice near the Amery Ice Shelf and the southern Indian Ocean.

We noted earlier that estimates from early satellites, such as Nimbus I and II, show some brief instances of very extensive and very reduced Antarctic sea ice. For example, in September 1964 ice extent was greater in most of the Southern Ocean than this year, the exception being the Ross Sea. Two years later, in 1966, the August extent shrank to a level smaller than any for that month in the modern satellite record. As seen in Figure 5, the largest variations between this early record and today occur around 180 degrees East in the South Pacific. This area is particularly sensitive to impacts of increased westerly winds and the Amundsen Sea Low, an atmospheric pressure pattern that tends to spread the sea ice cover northward in the Ross Sea. The change in winds and the Amundsen Sea Low over the past thirty-five years is well documented.

Reference

Henderson, G. R., B. S. Barrett, and D. M. Lafleur. Arctic sea ice and the Madden-Julian Oscillation (MJO). Climate Dynamics , October 2014, Vol. 43, Issue 7-8, pp 2185-2196.