Tag Archives: Arctic

Spring has sprung in the Arctic

Arctic sea ice has passed its annual maximum extent and is beginning its seasonal decline through the spring and summer. While total extent was not at record low, it remained well below average through March. Ice fracturing continued north of Alaska, and the Arctic Oscillation was in a strongly negative phase during the second half of the month, with unusually high sea level pressure over almost all of the Arctic Ocean. Levels of multiyear ice remain extremely low. The ice is thinner, and satellite data suggests that first-year ice may now cover the North Pole area for the first time since winter 2008.

Overview of conditions

Figure 1. Arctic sea ice extent for March 2013 was 15.04 million square kilometers (5.81 million square miles). The magenta line shows the 1979 to 2000 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 March 2013 averaged 15.04 million square kilometers (5.81 million square miles). This is 710,000 kilometers (274,000 square miles) below the 1979 to 2000 average extent, and 610,000 square kilometers (236,000 square miles) above the record low for the month, which happened in 2006. Continuing a trend in recent winters, ice extent was near or below average levels throughout most of the Arctic, with the exception of higher extent in the Bering Sea.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of April 1, 2013, along with daily ice extent data for the previous five years. 2012 to 2013 is shown in blue, 2011 to 2012 in green, 2010 to 2011 in pink, 2009 to 2010 in navy, and 2008 to 2009 in purple. The 1979 to 2000 average is in dark gray. The gray area around this 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

As Arctic sea ice reaches its maximum extent in March, the net gain or loss through the month tends to be small. This year, extent decreased 5,400 square kilometers (2,100 square miles) between the beginning and end of the month, with the decline in the second half of the month slightly outweighing the increase over the first half. Air temperatures (at the 925 mb level, or about 3,000 feet) were 3 to 6 degrees Celsius (5 to 11 degrees Fahrenheit) higher than average over the central Arctic Ocean, with cooler conditions compared to average (3 to 6 degrees Celsius, or 5 to 11 degrees Fahrenheit) over the Kara and Barents seas.

The circulation pattern known as the Arctic Oscillation (AO) reached an extreme negative phase in the second half of the month, associated with unusually high sea level pressure covering nearly the entire Arctic Ocean. The AO index , a measure of the state of the atmosphere over the Arctic, fell to as low as -5 sigma in mid March. This caps several months of a persistently negative AO. In the past, a negative AO in winter has been associated with the retention of thick ice in the Arctic Ocean and reduced export by drift into the Atlantic, favoring more extensive sea ice at the end of the summer melt season. However, in recent years, this relationship has not held and low summer extents have followed winters with strong negative AO. The month was also notable for continued fracturing of the ice cover in the Beaufort and Chukchi seas north of Alaska, as seen in a new animation by the NASA Earth Observatory . This is consistent with wind patterns associated with the strong negative pattern of the AO.

March 2013 compared to previous years

Figure 3. Monthly March ice extent for 1979 to 2013 shows a decline of 2.5% per decade.

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

Average ice extent for March 2013 was the fifth lowest for the month in the satellite record. Through 2013, the linear rate of decline for March ice extent is 2.5% per decade relative to the 1979 to 2000 average. While the percentage trend is lower than in the summer, the average rate of decrease is 39,800 square kilometers (15,300 square miles) per year, roughly the size of Maryland and Delaware combined.

A record extent of first-year ice in the Arctic

Figure 4. Imagery from the European Advanced Scatterometer (ASCAT) for December 2, 2012 (top) and March 28, 2013 (bottom) show the change in multiyear ice coverage over the winter season, as outlined by the colored lines. In winter, multiyear ice changes are due to the motion of the ice, either export through Fram Strait or redistribution within the Arctic Ocean.

Credit: Advanced Scatterometer imagery courtesy NOAA NESDIS, analysis courtesy T. Wohlleben, Canadian Ice Service
High-resolution image

Between the 2012 summer minimum and the 2013 winter maximum, sea ice extent increased 11.72 million square kilometers (4.53 million square miles), the largest increase in the satellite record. This was primarily due to the extreme record low ice extent in September 2012, which resulted in a near-record high first-year ice extent. This is evident in imagery from the Advanced Scatterometer (ASCAT) sensor on the European METOP-A satellite provided by National Oceanic and Atmospheric Administration’s National Environmental Satellite, Data, and Information Service (NOAA NESDIS). Analysis by Trudy Wohlleben at Environment Canada indicates that multiyear ice is relegated to areas far from the Alaskan and Eurasian coasts. Over the winter, some multiyear ice recirculated into the Beaufort Sea where significant melt of multiyear ice has occurred in recent summers. Also, some multiyear ice has been lost, as it moved out of the Arctic through Fram Strait. The boundary between primarily first-year ice and multiyear ice is now near the North Pole (indicated by the small black circle near the center of the image), marking the first time since the winter of 2008 that a substantial amount of first-year ice may be covering the pole as we enter the melt season.

Oldest ice continues to decline

Figure 5. The map at top shows the ages of ice in the Arctic at the end of March 2013; the bottom graph shows how the percentage of ice in each age group has changed from 1983 to 2013.

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

While multiyear ice used to cover up to 60% of the Arctic Ocean, it now covers only 30%. There is a slight rebound in the oldest ice (4+ years old), a remnant of the large amount of first-year ice that formed during the winter after the 2007 record minimum. However, most of that new ice has not survived through the subsequent years. The oldest ice now comprises only 5% of the ice in the Arctic Ocean. This is a slight uptick from last winter’s record low of 3%, but still far less than during the 1980s when old ice covered roughly 25% of the region.

 Satellite estimates show continued thinning

Figure 6. Estimates of February/March average sea ice thickness for 2004 to 2008 from NASA’s ICESat (left) and February/March 2012 from CryoSat-2 (right). Colors indicate ice thickness in meters, with blue indicating 1-meter thick sea ice and red indicating 5-meter thick sea ice. The black and gray lines in the CryoSat-2 image are tracks of airborne data collected for validation. The triangle, circle, and square are locations of upward-looking sonar (ULS) moorings, also used for validation of the CryoSat-2 estimates.

Credit: American Geophysical Union
High-resolution image

The ASCAT data and ice age data both suggest a continued thinning of the ice pack, and overall decline in its volume, but they do not provide direct information on ice thickness. However, the European Space Agency’s CryoSat-2 satellite, launched in April 2010, now provides estimates of sea ice thickness distribution across the Arctic Ocean. A new paper by Laxon et al. (2013) shows the first published results from CryoSat-2 and compares them with thickness estimates from NASA’s ICESat satellite, which operated from 2003 to 2009. The CryoSat-2 results indicate continued thinning since 2008. Significantly, ice along the north coast of Greenland appears to have thinned—in the past this has been the site of some of the thickest sea ice in the Arctic. The paper also shows that total volume estimates from CryoSat-2 agree well with University of Washington’s Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS)  estimates.

In memoriam

We dedicate this post to Seymour Laxon, who tragically passed away in early January. Laxon was a driving force behind the CryoSat-2 mission, a leading innovator in the development of sea ice altimetry, an outstanding scientist, and a great friend to the sea ice community, including the contributors to Arctic Sea Ice & News Analysis.

Further reading

Laxon S. W. , K. A. Giles , A. L. Ridout , D. J. Wingham , R. Willatt , R. Cullen , R. Kwok , A. Schweiger , J. Zhang , C. Haas , S. Hendricks , R. Krishfield , N. Kurtz , S. Farrell, and M. Davidson. 2013. CryoSat-2 estimates of Arctic sea ice thickness and volume , Geophysical Research Letters ,  40, doi: 10.1002/grl.50193 .

A fractured winter

Arctic sea ice is nearing its winter maximum and will soon begin its seasonal decline. Ice extent remains below average, in part a result of the persistence of the negative phase of the Arctic Oscillation that has kept winter temperatures warmer than average. The Antarctic passed its summer minimum ice extent, reaching the second highest level in the satellite record at this time of year, primarily due to continued higher-than-average ice in the Weddell Sea.

Overview of conditions

Figure 1. Arctic sea ice extent for February 2013 was 14.66 million square kilometers (5.66 million square miles). The magenta line shows the 1979 to 2000 median extent for that month. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

Average sea ice extent for February 2013 was 14.66 million square kilometers (5.66 million square miles). This is 980,000 square kilometers (378,000 square miles) below the 1979 to 2000 average for the month, and is the seventh-lowest February extent in the satellite record. Since 2004, the February average extent has remained below 15 million square kilometers (5.79 million square miles) every year except 2008. Prior to 2004, February average extent had never been less than 15 million square kilometers. Ice extent remains slightly below average everywhere except the Bering Sea.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 3, 2013, along with daily ice extent data for the 2012, the record low year. 2013 is shown in blue, and 2012 in green. 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 February, the Arctic gained 766,000 square kilometers of ice (296,000 square miles), which is 38% higher than the 1979 to 2000 average for the month. Air temperatures at the 925 hPa level were 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) higher than average across the Atlantic sector of the Arctic, especially near Iceland and in Baffin Bay. Temperatures were lower than average by 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) north of Greenland and the Canadian Archipelago, and in the Beaufort, Chukchi and East Siberian seas, linked to anomalously low sea level pressure over Alaska and Canada. The dominant feature of Arctic sea level pressure for February 2013 was unusually high pressure over the East Greenland and Barents seas, consistent with a predominantly negative phase of the Arctic Oscillation.

February 2013 compared to previous years

Figure 3. Monthly February ice extent for 1979 to 2012 shows a decline of -2.9% per decade.

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

Average Arctic sea ice extent for February 2013 was the seventh lowest for the month in the satellite record. Through 2013, the linear rate of decline for February ice extent is -2.9% per decade relative to the 1979 to 2000 average. Although the relative reduction in winter sea ice extent remains small compared to reductions in summer, the linear trend represents an overall reduction of more than 1.57 million square kilometers (606,000 square miles) from 1979 to 2013.

Persistence of the negative phase of the Arctic Oscillation

Figure 4. These ice motion images for November 2012 (left) and December 2012 (right) show strong export of ice through the Fram Strait in November, while in December ice export through the Fram was about average.

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

As discussed in the January and February posts, sea level pressure in the Arctic has remained higher than average, resulting in persistence of the negative phase of the Arctic Oscillation (AO). During the negative phase of the Arctic Oscillation, enhanced poleward transport of warm air tends to keep temperatures in the Arctic above average. At the same time, the negative phase of the Arctic Oscillation allows for more cold Arctic air to intrude or mix with air at lower latitudes. These cold air outbreaks can result in low temperatures and increased storminess in mid latitudes.

The Arctic Oscillation also impacts sea ice movement in the Arctic. The negative phase of the Arctic Oscillation is linked to an increase in the strength of the Beaufort Gyre and reduced outflow of ice through Fram Strait. A negative AO used to help promote ice survival through summer by strengthening the Beaufort Gyre and thereby increasing the distribution of old, thick ice along coastal Alaska and Siberia. However, the location and strength of positive sea level pressure anomalies has varied throughout winter, with varied impacts on ice motion.

For example, during November (weak AO index of -0.111) positive sea level pressure anomalies were centered over the Bering Sea and Alaska, resulting in strong ice motion from the central Arctic towards coastal Canada and north of Greenland outwards towards Fram Strait. In December, the strong negative AO index of -1.749 was reflected in positive sea level pressure anomalies centered over the Kara and Barents seas, enhancing ice motion from the southern Beaufort into the Chukchi sea and out towards the Bering Sea. Export of ice out of Fram Strait was about average. Similar variations in positive sea level pressure anomalies have continued, with the largest positive anomalies over the central Arctic in January, and over the Barents Sea in February.

This pattern is similar to that observed during the extreme negative Arctic Oscillation year of 2009/2010, when old ice was transported into the southern Beaufort and Chukchi seas where it then melted out during summer 2010, further depleting the Arctic of its store of old, thick ice.

Ice fracture

Figure 5. In this series of images from February 13 to March 2, from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS), a large crack expands in the sea ice near the coasts of Canada and Alaska. Black areas indicate where the satellite instrument did not collect data due to lack of sunlight. The dark area decreases as the sun rises in the Arctic. Rapid Response imagery was obtained from the NASA Land Atmosphere Near-real time Capability for EOS (LANCE) system.

Credit: NASA LANCE/National Snow and Ice Data Center
View the image series

During the last couple of weeks of February, a broad area of sea ice has fractured off the coast of Alaska and Canada, extending from Ellesmere Island in the Canadian Arctic to Barrow, Alaska. This fracturing event appears to be related to a series of storms that moved across central Alaska starting on February 10, 2013, causing intense easterly winds along the coast and strong off-shore ice motion.* The large area of fractured ice is located in predominantly first-year ice, which is thinner and easier to fracture than thick, multiyear ice. Similar patterns were observed in early 2011 and 2008, but the 2013 fracturing is quite extensive.  The animation (Figure 5) shows the progress of the fracturing, and the general strong rotation of the Beaufort Gyre ice motion pattern during late February. (See also this animation of the fracture from the AVHRR instrument, posted on the Arctic Sea Ice Blog.)

* Note: We originally attributed the fracturing event to a storm that passed over the North Pole, and stated “This fracturing event appears to be related to a storm that passed over the North Pole on February 8, 2013, creating strong off-shore ice motion.” We corrected this sentence after reexamining weather charts. The updated version now reads, “This fracturing event appears to be related to a series of storms that moved across central Alaska starting on February 10, 2013, causing intense easterly winds along the coast and strong off-shore ice motion.”

Antarctic sea ice extent continues above average

Figure 6. Antarctic sea ice extent for February 2013 was 3.83 million square kilometers (1.48 million square miles). The magenta line shows the 1979 to 2000 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

The Antarctic sea ice minimum extent appears to have passed, on February 20. Ice was quite extensive throughout the austral summer period. Monthly average sea ice extent for February 2013 was 3.83 million square kilometers (1.48 million square miles) and minimum daily sea ice extent for the Antarctic region was 3.68 million square kilometers (1.42 million square miles) on February 20. Unusual circulation patterns, likely resulting from higher-than-average pressure in the Bellingshausen Sea, pushed sea ice in the northwestern Weddell Sea far to the north, as we mentioned in our February post. NASA’s Earth Observatory posted this image of ice in the Weddell Sea as Image of the Day for March 1st, 2013. Extent was also well above average for the Ross Sea region relative to the entire 1979 to 2013 satellite record.

The Odden

Figure 7. This image shows sea ice cover in early May, 2012 in the east Greenland Sea. Sea ice extent is provided at 4 kilometer resolution by the NSIDC/NIC multi-sensor MASIE product and sea ice concentration (varying from 0 to 1) at 25 kilometer resolution by NSIDC’s Near-Real Time Passive Microwave product. The red dot shows the estimated position of an ARGO profiling float deployed as part of a NASA-sponsored project led by Michael Steele  and Patricia Matrai. This float is capable of storing ocean data while under the ice pack, which are then received via satellite when the ice recedes. Ongoing analysis of these data indicates that cold, fresh surface water lies just under the ice extension along the Jan Mayen Ridge, a signature of Arctic waters.

Credit: M. Steele, University of Washington and P. Matrai, Bigelow Lab/National Snow and Ice Data Center
High-resolution image

Within the East Greenland Sea, an ice tongue about 1,300 kilometers (807 miles) in length, referred to as “The Odden” (Norwegian word for headland), would regularly form during winter months eastwards from the main East Greenland ice edge. The Odden would form in winter because of an eastward flow of very cold ocean waters in the Jan Mayen current and may have played an important role in winter ocean convection as new ice would form. It would form as early as December and as late as April and was present during the 1980s, a few times in the 1990s, and very rarely since 2000. While the Odden rarely formed in last two decades, there is frequently a small extension of ice along the Jan Mayen Ridge, which may indicate that eastward flow of cold ocean water is still occurring.