A better year for the cryosphere

This summer, Arctic sea ice loss was held in check by relatively cool and stormy conditions. As a result, 2013 saw substantially more ice at summer’s end, compared to last year’s record low extent. The Greenland Ice Sheet also showed less extensive surface melt than in 2012. Meanwhile, in the Antarctic, sea ice reached the highest extent recorded in the satellite record.

Overview of conditions

map of sea ice extent

Figure 1. Arctic sea ice extent for September 2013 was 5.35 million square kilometers (2.07 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 reached its annual minimum on September 13. After the minimum, extent remained largely unchanged for much of the middle of September, but increased rapidly toward the end of the month with the onset of strong autumn cooling.

Arctic sea ice extent averaged for September 2013 was 5.35 million square kilometers (2.07 million square miles). This was 1.17 million square kilometers (452,000 square miles) below the 1981 to 2010 average extent. September 2013 ice extent was 1.72 million square kilometers (664,000 square miles) higher than the previous record low for the month that occurred in 2012.

Conditions in context

graph of sea ice extent

Figure 2. The graph above shows Arctic sea ice extent as of September 30, 2013, along with daily ice extent data for the previous five years. 2013 is shown in light blue, 2012 in green, 2011 in orange, 2010 in light purple, 2009 in dark blue, and 2008 in dark purple. 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

The rate of ice loss varied through the summer. Both May 2012 and May 2013 saw near average extents and rates of decline. This year, the rate of ice loss sped up in late June and early July, then settled into a near-average rate of decline, with extent approximately 500,000 square kilometers (193,000 square miles) greater than the same time in 2012. Ice loss then slowed down in August to only a little faster than average rates of loss for that time of year. In comparison, during 2012, the rate of loss accelerated in early June and through July, then accelerated even more in August to produce a new record low extent in September 2012.

Overall, 10.03 million square kilometers (3.87 million square miles) of ice were lost between the 2013 maximum and minimum extents. This was the seventh summer that more than 10 million square kilometers of ice extent were lost; all but one of the seven (the summer of 1990) have occurred since 2007.

September 2013 compared to previous years

Figure 3. Monthly September ice extent for 1979 to 2013 shows a decline of X.X% per decade.||Credit: National Snow and Ice Data Center |High-resolution image

Figure 3. Monthly September ice extent for 1979 to 2013 shows a decline of 13.7% per decade.

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

September average sea ice extent for 2013 was the sixth lowest in the satellite record. The 2012 September extent was 32% lower than this year’s extent, while the 1981 to 2010 average was 22% higher than this year’s extent. Through 2013, the September linear rate of decline is 13.7% per decade relative to the 1981 to 2010 average.

What a difference a year makes

Figure 4. These images show June to August sea level pressures compared to the 1981 to 2010 average, for 2012 (left) and 2013 (right). In 2013, low pressures prevailed over the central Arctic Ocean and Greenland. Blues and purples indicate low pressure, while greens, yellows, and reds indicate high pressures. ||Credit: National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Division|High-resolution image

Figure 4. These images show June to August sea level pressures compared to the 1981 to 2010 average, for 2012 (left) and 2013 (right). In 2013, low pressures prevailed over the central Arctic Ocean and Greenland. Blues and purples indicate low pressures, while greens, yellows, and reds indicate high pressures.

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

Contrasting weather conditions were a significant factor in this year’s higher sea ice extent and lower Greenland Ice Sheet melt intensity, compared to last year. This summer saw air temperatures at the 925 hPa level that were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) lower than last summer. It was also a cool summer compared to recent years over much of the Arctic Ocean, and even cooler than the 1981 to 2010 average in some regions, particularly north of Greenland.

While 2012 and 2013 extents were similar through May, weather patterns from June to August helped retain more ice. Last summer was marked by lower than average pressure over the Eurasian side of the Arctic and higher than average pressure over Greenland. This resulted in a dipole-like wind pattern that favored ice transport across the ocean and the import of heat from southern latitudes along the Eurasian side of the Arctic. In contrast, this summer was characterized by unusually low pressure over much of the Arctic Ocean, which limited heat import from the south and brought more extensive cloud cover, keeping temperatures lower. In addition, the winds associated with the low pressure caused the ice cover to spread out and cover a larger area.

Over land, the cool spring resulted in greater than average March and April snow cover for the Northern Hemisphere. However, as in recent years, the snow melted rapidly, and by May, snow cover was at near record lows. Cooler weather conditions also limited surface melt on the Greenland Ice Sheet, which was still greater than the 1981 to 2010 average, but not near the record set in 2012 (see our Greenland Ice Sheet Today post for more details).

Ice thickness and age

Figure 5. These images from March 2013 (top) and September 2013 (bottom) show the changes in multiyear ice between this year's sea ice maximum and minimum extents. In contrast to 2012, the record low extent year, multiyear ice tended to stay put, rather than being circulated around, which can expose it to warmer currents and winds that increase melt. Much of the Arctic ice cover now consists of first-year ice (shown in purple), which tends to melt rapidly in summer’s warmth. ||Credit: NSIDC courtesy Jim Maslanik, University of Colorado Boulder and Walt Meier, NASA Goddard Cryospheric Sciences |High-resolution image

Figure 5. These images from March 2013 (top) and September 2013 (bottom) show the changes in multiyear ice between this year’s sea ice maximum and minimum extents. In contrast to 2012, the record low extent year, multiyear ice tended to stay put, rather than being circulated around, which can expose it to warmer currents and winds that increase melt. Much of the Arctic ice cover now consists of first-year ice (shown in purple), which tends to melt rapidly in summer’s warmth.

Credit: NSIDC courtesy Mark Tschudi, University of Colorado Boulder and Walt Meier, NASA Goddard Cryospheric Sciences
High-resolution image

The pattern of ice thickness for the summer of 2013 is similar to what has been seen in recent years. According to data from the European Space Agency CryoSat-2 radar altimeter, the spring melt season started with an Arctic ice cover thinner than in any recent year. This corroborates thickness information inferred from a calculation of ice age that showed first-year ice, which is thinner and more vulnerable to melt, over a significant part of the Arctic Ocean as the melt season started (see our earlier post). Older, thicker ice remained in a region roughly between the North Pole and the Canadian Archipelago and the Greenland coast.

In recent summers, there has been considerable transport of older ice into the Beaufort and Chukchi seas, where it has been broken up and exposed to a warm ocean and high air temperatures. This has been a major factor in the loss of multiyear ice over the last decade. This year was notably different. Because this year’s wind pattern was different than 2012, the multiyear ice largely remained in a compact area along the Canadian Archipelago and did not circulate into the Beaufort and Chukchi seas. The cooler conditions this summer also helped preserve more of the first-year ice through the summer.

The first-year ice that survived the summer, now defined as second-year ice, will thicken through autumn and winter. However, it would take several more cool years in a row to build the ice cover back to the state it was in during the 1980s, which consisted of a larger proportion of thicker, multiyear ice that was more resistant to melt. While ice in the Arctic will thicken through this autumn and winter, winds may also transport some of the thicker ice out of the Arctic Ocean and into the North Atlantic.

Another record high in the Antarctic

September Antarctic sea ice image

Figure 6. Antarctic sea ice extent for September 2013 was 19.77 million square kilometers (7.63 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

Antarctic sea ice extent reached 19.47 million square kilometers (7.52 million square miles) on September 22, a record high maximum extent relative to the satellite record, and slightly above the previous record high set last year. This year’s maximum extent was 3.6% higher than the 1981 to 2010 average Antarctic maximum, representing an ice edge that is 35 kilometers (approximately 22 miles) further north on average. Overall, Antarctic September sea ice extent is increasing at 1.1% per decade relative to the 1981 to 2010 average. This increase is likely due to a combination of factors, including winds and ocean circulation. A recent paper by our colleague Jinlun Zhang at the University of Washington concludes that changes in winds are resulting in both more compaction within the ice pack and more ridging, causing a thickening of the pack and making it more resistant to summer melt.

Table 1: Previous Arctic sea ice extents for the month of September *

Year Average Arctic Sea Ice Extent for September Trend, in % per decade (relative to 1981-2010 avg.)
in millions of square kilometers in millions of square miles
2007 4.30 1.66 -11.0
2008 4.73 1.83 -11.0
2009 5.36 2.08 -12.0
2010 4.90 1.90 -12.4
2011 4.63 1.79 -12.0
2012 3.63 1.40 -14.0
2013 5.35 2.07 -13.7
1979 to 2000 average 7.04 2.72
1981 to 2010 average 6.52 2.52

Note that the dates and extents of the minimums have been re-calculated from what we posted in previous years; see our Frequently Asked Questions for more information.

Reference

Zhang, J. In press. Modeling the impact of wind intensification on Antarctic sea ice volume. J. Climate, doi:10.1175/JCLI-D-12-00139.1.

Arctic sea ice reaches lowest extent for 2013

On September 13, Arctic sea ice reached its likely minimum extent for 2013. The minimum ice extent was the sixth 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. Meanwhile, in the Antarctic, sea ice extent reached a record high on September 18, tied with last year’s maximum.

Please note that this is a preliminary announcement. Changing winds could still push ice floes together, reducing ice extent further. NSIDC scientists will release a full analysis of the melt season in early October, once monthly data are available for September.

Overview of conditions

Figure 1. Arctic sea ice extent for September 13, 2013 was 5.10 million square kilometers (1.97 million square miles). The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

On September 13, 2013, sea ice extent dropped to 5.10 million square kilometers (1.97 million square miles). This appears to have been 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 two days earlier than the 1981 to 2010 average minimum date of September 15.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 19, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray.  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 September 19, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

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

This year’s minimum was 1.69 million square kilometers (653,000 square miles) above the record minimum extent in the satellite era, which occurred on September 16, 2012, and 1.12 million square kilometers (432,000 square miles) below the 1981 to 2010 average minimum.

Varying distribution of ice in 2013 versus 2012

Figure 3. This image compares differences in ice-covered areas between September 13, 2013, the date of this year’s minimum, and September 16, 2012, the record low minimum extent. Light gray shading indicates the region where ice occurred in both 2013 and 2012, while white and dark gray areas show ice cover unique to 2013 and to 2012, respectively.  Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 3. This image compares differences in ice-covered areas between September 13, 2013, the date of this year’s minimum, and September 16, 2012, the record low minimum extent. Light gray shading indicates the region where ice occurred in both 2013 and 2012, while white and dark gray areas show ice cover unique to 2013 and to 2012, respectively. Sea Ice Index data. About the data

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

Comparing this year’s minimum extent to 2012, while extent was higher on average this year, there were variations from region to region. There was considerably higher sea ice extent in the Beaufort, Chukchi, and East Siberian sea regions, with the ice edge several hundred kilometers farther south compared to last year. This year the Canadian Archipelago also retained much more ice, keeping the Northwest Passage closed.  The most notable area of less ice this year compared to last was off the east coast of Greenland, south of Fram Strait. Other small areas of decreased extent were found north of the Kara and Laptev seas.

See an animation of this summer’s sea ice extent produced by the NASA Scientific Visualization Studio at http://svs.gsfc.nasa.gov/goto?4104.

Previous minimum Arctic sea ice extents**

Table 1.  Previous minimum Arctic sea ice extents
 YEAR MINIMUM ICE EXTENT DATE
IN MILLIONS OF SQUARE KILOMETERS IN MILLIONS OF SQUARE MILES
2007 4.17 1.61 September 18
2008 4.59 1.77 September 20
2009 5.13 1.98 September 13
2010 4.63 1.79 September 21
2011 4.33 1.67 September 11
2012 3.41 1.32 September 16
2013 5.10 1.97 September 13
1979 to 2000 average 6.70 2.59 September 13
1981 to 2010 average 6.22 2.40 September 15

According to near-real-time data, this year’s minimum extent is slightly lower than 2009. However, the ranking between 2009 and 2013 is close, and may change once the final version of the data are processed. See our Frequently Asked Questions: Do your data undergo quality control? for more information about near-real-time data.

** Note that the dates and extents of the minimums have been re-calculated from what we posted in previous years; see our Frequently Asked Questions for more information.

Melt season ending

Following a relatively cool summer, sea ice extent fell to a little over 5 million square kilometers (1.93 million square miles) over the first two weeks of September and is at or near the minimum extent for the year. NSIDC will announce the final minimum extent and date once it is confirmed.

Overview of conditions

Figure 1. Arctic sea ice extent for September 16, 2013 was 5.10 million square kilometers (X.XX million square miles). The orange 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 September 16, 2013 was 5.10 million square kilometers (2.00 million square miles). The orange 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 as of September 16, 2013 was 5.10 million square kilometers (2.00 million square miles). This is substantially more ice than observed on the same date last year, yet sea ice extent remains quite low compared to the long-term 1981 to 2010 average. As is typical for this time of year, winds or currents can compact or spread apart the ice, resulting in small daily fluctuations of the ice cover.

During the first two weeks of September, sea ice extent continued to decline in the East Siberian, Laptev, and Kara seas while staying essentially constant in the Beaufort and Chukchi seas since the beginning of September. The Northwest Passage has seen more extensive ice this summer since 2007 and is not open. On the Eurasian side of the Arctic, the Northern Sea Route appears to have opened up briefly in September.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 16, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. 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 September 15, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

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

Ice loss through the first two weeks of September was faster than average. Air temperatures at the 925 hPa level were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) higher than average over much of the Arctic Ocean the first part of the month, in stark contrast to most of the summer when cooler temperatures dominated. Below average temperatures were found in the Beaufort and Chukchi seas where ice growth began around the first week of the month.

Even though extent at the beginning of this summer was similar to last year, the melt season ended with considerably more ice. This is not surprising, as climate models consistently project that there will be large variations in summer ice extent from year to year. A cool summer can help to retain a thin layer of ice, increasing the overall ice extent. Conversely, a warm summer can help to remove much of the thin ice cover.

Cold summer over central Arctic and Greenland

Figure 3: Figures above show the 925 hPa air temperature anomalies averaged from June, July and August 2013 relative to 1981 to 2010 (left) and relative to 2007 to 2012 (right). ||Credit: NOAA/ESRL Physical Sciences Division||High-resolution image

Figure 3: These figures show air temperature anomalies averaged from June, July, and August 2013 at the 925 hPa level, relative to the 1981 to 2010 average (left) and relative to the 2007 to 2012 average (right).

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

As a whole, air temperatures this summer have been below average over most of the central Arctic Ocean and Greenland, helping to slow down ice melting. Compared to the 1981 to 2010 average, air temperatures at the 925 hPa level have been -0.5 to -2.0 degrees Celsius (-0.9 to -3.6 degrees Fahrenheit) below average over central Greenland, north of Greenland and towards the pole, and over the Canadian Archipelago. Unusually low temperatures are also noted over the East Siberian Sea, where ice cover has remained near average throughout the summer.

The cool conditions that have prevailed this summer are even more remarkable when compared to the last six years, which have seen very low September sea ice extents. Compared to the 2007 to 2012 average, air temperatures at the 925 hPa level averaged over June, July and August were lower this summer throughout most of the Arctic by -0.5 to -3.5 degrees Celsius (-0.9 to -6.3 degrees Fahrenheit). The previous six summers have been dominated by high sea level pressure over the Beaufort Sea and Greenland, paired with low sea level pressure over Eurasia—a pattern that helps to transport warm air into the Arctic. In contrast, this summer was characterized by low sea level pressure over the central Arctic and Greenland. Cooler conditions have also led to less surface melting on the Greenland Ice Sheet.

Sea surface temperature trends

Figure 4: These maps show Arctic sea surface temperatures  (top) and temperature anomalies (bottom) for August 2013, in degrees Celsius. 

Credit: Michael Steele and Wendy Ermold, Polar Science Center, Applied Physics Lab, University of Washington
High-resolution image

Colleagues Michael Steele and Wendy Ermold at the University of Washington found that sea surface temperatures (SSTs) in the Arctic Ocean were above the 1982 to 2006 average during August, as has been the case since 2007. Sea ice retreat was later and not as extreme relative to recent years in the western Arctic (i.e., the Beaufort, Chukchi, and East Siberian seas) and as a result, SSTs were near the long-term average there. SSTs were well above average in the eastern Arctic (Laptev, Kara, and Barents seas). This can be linked to early ice retreat in the Laptev Sea. However, warm conditions in the southern Barents and Kara seas are likely influenced by advection of warm water from the south in the Norwegian Sea. Overall, for the period 2007 to 2013 there is a pattern of declining SSTs in the western Arctic, and increasing SSTs in the eastern Arctic.

Antarctic sea ice extent

Figure 5. XXXXXXInsertCaptionhereXXXXXXX.||Credit: The University of Bremen/AMSR2 for the top images and NOAA/ESRL Physical Sciences Division for the bottom images|High-resolution image

Figure 5. Sea ice extent data from high-resolution passive microwave data (top left and right), and climate data for the period August 15 to September 15, 2013 (bottom images). These images show Antarctic sea ice extent near the satellite-era record high set last year. The geopotential height at 850 millibars (lower left) is an indication of the relative air pressure at ~5000 feet (~1500 meters) above sea level. This shows an unusually broad area of high pressure encompassing the entire continent out to near the sea ice edge, and low pressure surrounding that outside the edge – the opposite of the general trend. This has greatly reduced the average westerly wind flow (shows as negative values in the zonal wind plot, lower right), making for light winds at the sea ice edge.

Credit: University of Bremen/AMSR2 (top images) and NOAA/ESRL Physical Sciences Division (bottom images).
High-resolution image

As ice extent approaches its summer minimum in the Arctic, the winter maximum is near for Antarctica. This year, as was the case in 2012, Antarctic sea ice extent is very high. As of September 16, the current extent is 19.45 million square kilometers (7.51 million square miles), a record for this date with respect to the 1979 to 2012 satellite era. This is about 3.9% above the average maximum extent for the 30-year comparison period 1981 to 2010. In contrast, this year’s Arctic summer minimum ice extent is approximately 30% below levels seen in the early 1980s, and the 2012 record low extent was around 60% below levels seen in the same period. This helps to highlight why scientists are more concerned by Arctic ice shrinkage than by Antarctic ice expansion.

Antarctic weather patterns in August were unusual. Contrary to a 50-year trend towards stronger westerly wind flow—a pattern associated with both ozone loss and increased heat-trapping gases in the atmosphere—August 2013 saw a period of very low westerly wind speed across the continent.

* Note: On September 19, 2013, we revised a sentence in this section for clarity. A sentence that originally read, “In contrast, this year’s Arctic summer minimum ice extent is approximately 30% below the 30-year period average, and the 2012 record low extent was nearly 60% below the average.” now reads, “In contrast, this year’s Arctic summer minimum ice extent is approximately 30% below levels seen in the early 1980s, and the 2012 record low extent was around 60% below levels seen in the same period.”

A real hole near the pole

Sea ice continued its late-season summer decline through August at a near-average pace. Ice extent is still well above last year’s level, but below the 1981 to 2010 average. Open water was observed in the ice cover close to the North Pole, while in the Antarctic, sea ice has been at a record high the past few days.

Overview of conditions

Figure 1. Arctic sea ice extent for August 2013 was X.xx million square kilometers (X.XX 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 August 2013 was 6.09 million square kilometers (2.35 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 August 2013 averaged 6.09 million square kilometers (2.35 million square miles). This was 1.13 million square kilometers (398,000 square miles) below the 1981 to 2010 average for August, but well above the level recorded last year, which was the lowest September extent in the satellite record. Ice extent this August was similar to the years 2008 to 2010. These contrasts in ice extent from one year to the next highlight the year-to-year variability attending the overall, long-term decline in sea ice extent.

Extent in the Beaufort and Chukchi seas has dropped below average, after near average conditions in July. The only region with average extent is the East Siberian Sea.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 4, 2013, along with daily ice extent data for the previous five years. 2013 is shown in light blue, 2012 in green, 2011 in orange, 2010 in light purple, 2009 in dark blue, and 2008 in dark purple. 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 September 4, 2013, along with daily ice extent data for the previous five years. 2013 is shown in light blue, 2012 in green, 2011 in orange, 2010 in light purple, 2009 in dark blue, and 2008 in dark purple. 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

Relatively cool conditions over the central Arctic Ocean continued, a pattern that has characterized this summer. Temperatures at the 925 hPa level in the high Arctic (north of Greenland to the North Pole) were 0.5 to 3 degrees Celsius (1 to 5 degrees Fahrenheit) below the 1981 to 2010 average. In comparison, temperatures in coastal areas of the Arctic were mostly near average, and temperatures in the Barents and Beaufort seas were about 2 degrees Celsius (4 degrees Fahrenheit) above average. The distribution of the temperature anomalies can be related to the sea level pressure pattern. Below-average sea level pressures were linked to cloudy and cool conditions near the North Pole and extending into the northern North Atlantic. In contrast, above-average pressures dominated the Eurasian coast.

August 2013 compared to previous years

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

Figure 3. Monthly August ice extent for 1979 to 2013 shows a decline of 10.6% per decade.

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

The seasonal decline of extent through the month of August was slightly above average at 56,400 square kilometers (21,800 square miles) per day, but more than a third slower than the record decline rate in August 2012. This year’s August extent was the sixth lowest in the 1979 to 2013 satellite record.

August 2013 ice extent was 1.38 million square kilometers (533,000 square miles) above the record low August extent in 2012. The monthly trend is –10.6% per decade relative to the 1981 to 2010 average.

Water near the pole

Figure 4. This image from the AMSR2 satellite instrument shows Arctic sea ice concentration for September 2, 2013. A dark blue area of apparent open water can be seen near the North Pole, surrounded by a low ice concentration area. The gray circle indicates where the instrument did not acquire data, due to its orbit.|\Credit: NSIDC/University of Bremen|High-resolution image

Figure 4. This image from the AMSR2 satellite instrument shows Arctic sea ice concentration for September 2, 2013. A dark blue area of apparent open water can be seen near the North Pole, surrounded by a low ice concentration area. The gray circle around the North Pole indicates where the instrument did not acquire data, due to its orbit.

Credit: NSIDC/University of Bremen
High-resolution image

Earlier this summer, there was considerable interest in seeing liquid water in the North Pole Environmental Observatory (NPEO) web cam. As explained in our August 7 post, that region was simply a shallow melt pond of water atop the ice and not an actual opening in the ice. Nevertheless, our August 19 post described an extensive region of low ice concentration located fairly close to the pole.

Now, a large hole (roughly 150 square kilometers or 58 square miles) of near-zero ice concentration appears to have opened up at about 87 degrees North latitude. Small areas of open water are common within the ice pack, even at the North Pole, as the ice pack shifts in response to winds and currents, resulting in cracks (called leads) in the ice. The current opening seen in our satellite imagery is much larger. In 2006, a larger polynya appeared in the Beaufort and Chukchi seas, but it was much farther south.

Melting ice from above and below

Figure 4. . Results from six ice mass balance buoys that operated throughout the summer of 2013. The red dot denotes the buoy position on 28 August 2013. The red bar indicates the total amount of summer surface melt and the yellow bar shows bottom melt. The white background is the MASIE ice extent on 28 August 2013 mapped on Google Earth.||Credit: Julienne Stroeve/National Snow and Ice Data Center |High-resolution image

Figure 5. This map of the Arctic shows results from six ice mass balance buoys that operated throughout the summer of 2013. A red dot denotes each buoy position on August 28, 2013. The red bars indicate the total amount of summer surface melt and the yellow bars show bottom melt. The white background is the MASIE ice extent on August 28, 2013 mapped on Google Earth.

Credit: NSIDC courtesy Jackie Richter-Menge and Don Perovich/CRREL
High-resolution image

It may seem contradictory for a polynya-like opening to form near the pole while temperatures are lower than average, but it highlights the complex interplay between the ice, atmosphere, and ocean. Such openings in the ice occur two ways: through winds pushing the ice apart, or through melting. Both processes likely played a role in forming the current opening, but another key factor is a significant amount of thin, first-year ice in the region. This thin ice was more likely to melt completely than surrounding thicker ice. Heat from the ocean also contributes to melting of the ice from below, even though air temperatures have been below average in the region. Buoys that measure ice mass can provide information on surface and bottom melting.

During the summer of 2013 there were six ice mass balance buoys deployed in the Arctic over a wide area (red dots in Figure 5). The buoys were deployed in undeformed, multiyear ice, with a thickness between 2.2 and 3.5 meters (7 and 11 feet) before melt began. Data from the buoys show that the amount of surface ice melting ranged from 0 in the central Arctic, to 75 centimeters (30 inches) in the Beaufort Sea. Bottom melting varied from 8 to 108 centimeters (3 to 43 inches). The largest amount of bottom melting was observed at a buoy near the ice edge in the Beaufort Sea. This buoy had the largest total amount of melt, thinning from 339 centimeters (133 inches) in early June, to 157 centimeters (62 inches) on August 28. Ice thicknesses at the other buoys on August 28 ranged from 121 to 267 centimeters (48 to 105 inches). While bottom melting is continuing in some locations, most of this year’s surface melting has occurred. Data from the ice mass balance buoys are available at http://imb.crrel.usace.army.mil. (Thanks to Jackie Richter-Menge and Don Perovich at the Cold Regions Research and Engineering Laboratory [CRREL] for this part of the discussion.)

The balding Arctic

Arctic sea ice extent maintained a steady, near-average pace of retreat through the first half of August, making it highly unlikely that a new record low minimum will be reached this year. Nevertheless, there are extensive areas of low concentration ice, even in regions close to the North Pole, atmospheric pressure and temperature patterns this summer have differed markedly from those experienced in 2012; cooler than average conditions have prevailed over much of the Arctic Ocean. By contrast, Antarctic sea ice is near a record maximum extent for mid-August.

Overview of conditions

Figure 1. Arctic sea ice extent for August 18, 2013 was XX million square kilometers (XX million square miles). The orange 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 August 18, 2013 was 5.94 million square kilometers (2.30 million square miles). The orange 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 retreat through the first half of August was near average, bringing the ice extent to 5.94 million square kilometers (2.30 million square miles). Sea ice extent continues to track well below average levels (average of 1981 to 2010), though remains within two standard deviations of the long-term mean. Retreat rates increased slightly in the western Beaufort Sea and Chukchi Sea, but ice cover remains extensive in those regions compared to 2012. Another major difference between ice extent during 2012 and this year is the much greater extent in the East Siberian Sea. Low ice extent in this region observed last year was in part attributed to the effects of the “Great Cyclone of 2012” (see previous post of August 14, 2012). On the eastern side of the Arctic near Europe and Greenland, the extent remains below average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 18, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. 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 18, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

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

The sea ice retreat rate averaged from August 1 to 18 was near average at approximately 75,000 square kilometers (29,000 square miles) per day. However, satellite data show extensive low-concentration areas within the ice cover, which appear to have developed in response to the frequent passage of storm systems. These weather patterns also result in lower-than-average air temperatures over the Arctic. Temperatures in the central Arctic at the 925 hPa level have been 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) below average since late July.

A bit thin on top

Figure 3. This composite shows an AMSR-2 sea ice concentration map (top) and a MODIS true-color composite image (bottom) of the Arctic for August 14, 2013. Clouds in the MODIS scene obscure some of the ice edges seen in the AMSR-2 data set.||Credit: University of Bremen/AMSR2; NASA/GSFC, Rapid Response|High-resolution image

Figure 3. This composite shows an AMSR-2 sea ice concentration map (top) and a MODIS true-color composite image (bottom) of the Arctic for August 14, 2013. Clouds in the MODIS scene obscure some of the ice edges seen in the AMSR-2 data set.

Credit: University of Bremen/AMSR2; NASA/GSFC, Rapid Response
High-resolution image

Satellite data from the AMSR-2 instrument and MODIS show an unusually large expanse of low-concentration sea ice (20 to 80% cover) within our extent outline (15% or greater, using the SSM/I sensor) spanning much of the Russian side of the Arctic and extending to within a few degrees of the North Pole. A small area north of the Kara Sea has concentrations below 30%. This is likely in part a result of the dispersive effect of low-pressure systems that have migrated across the central Arctic over the past month. While some of the low concentrations recorded by AMSR-2 may be due to surface melt on sea ice, the MODIS image confirms that a large region is covered by isolated floes. The tendency towards a more open pack, with large areas of open water between ice floes, has increased in the past decade as the ice cover has thinned, as well as a tendency for formation of large polynyas (see ASINA posts for September 2006) and areas of pack detached from the main Arctic ice cover (such as mid-August 2012). The University of Washington’s Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) model and other models of ice thickness continue to indicate thin ice cover this summer.

Not like last year

Figure 4. These images compare air temperatures at 925 mb (about 2500 feet above sea level) and air pressures at sea level for June through July, 2012 (left side) and June to July 2013 (right side). ||Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division|High-resolution image

Figure 4. These images compare air temperatures at 925 mb (about 2500 feet above sea level) and air pressures at sea level for June through July, 2012, (left side) and June to July 2013 (right side).

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

A comparison of average temperature and sea level pressure maps for June and July of 2012 (left diagrams) and 2013 (right diagrams) help us to understand why ice extent is higher in 2013. The pattern of unusually low pressure centered near the pole in 2013 has helped to spread the ice out and is consistent with generally cool conditions over much of the Arctic Ocean, inhibiting melt. By contrast, in the summer of 2012, a broad region of unusually high pressure centered over Greenland, in combination with below average pressure centered over the East Siberian and Chukchi seas, led to winds over the Beaufort Sea with a more southerly component than is usually the case, leading to warm conditions. That high pressure last year over Greenland also contributed to a record melt season for the Greenland ice sheet. Melt this year over the ice sheet has been more moderate, though still above rates seen in the 1990s. See our upcoming Greenland Today site post later this week.

Can’t get there from here

Figure 5. The graph above shows projections of ice extent from August 1 through September 30th based on observed retreat rates appended to the August 18, 2013 ice extent. None of the observed patterns of the past few years, or the mean loss rates, bring the ice extent below 4.0 million square kilometers (1.56 million square miles).  Sea Ice Index  data.||Credit: National Snow and Ice Data Center|  High-resolution image

Figure 5. The graph above shows projections of ice extent from August 1 through September 30 based on observed retreat rates appended to the August 18, 2013 ice extent. None of the observed patterns of the past few years, or the mean loss rates, bring the ice extent below 4.0 million square kilometers (1.56 million square miles). Sea Ice Index data.

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

Projections of the likely minimum extent this year based on retreat rates from past years argue that it is highly unlikely that sea ice will surpass the record-setting low extent seen in 2012. With retreat rates similar to those of 2007 to 2012, the minimum extent would be near 5.0 million square kilometers (2.0 million square miles) in mid-September.

Record extent in the Antarctic

Figure 6. Antarctic daily sea ice extents for 2013, 2010, 2007, and the 1981 to 2010 mean for the past few months. Sea Ice Index data.||Credit: University of Bremen/AMSR2|High-resolution image

Figure 6. Antarctic daily sea ice extents for 2013, 2010, 2007, and the 1981 to 2010 mean for the past few months. Sea Ice Index data.

Credit: University of Bremen/AMSR2
High-resolution image

Antarctic sea ice extent for August 19 is 18.70 million square kilometers (7.22 million square miles), a record or near-record high level (August 19, 2010 was similarly high), led by unusually extensive ice in the Bellingshausen, Amundsen, and Ross seas, and in the western Indian Ocean sector. Climate conditions since June have been variable, but the most recent surge in ice growth has occurred during a period of unusually high pressure over the center of the continent, resulting in a slowing of the circumpolar winds, warm winter conditions for the central ice sheet areas (Vostok Station and Amundsen-Scott South Pole Station both had periods of spring-like -30s earlier in the month), and cold conditions in the Bellingshausen, allowing ice to grow extensively there.

A month of two halves and no hole

Following rapid ice loss in the first half of July, the pace of seasonal ice retreat slowed the rest of the month partly due to the return of a stormy weather pattern over the central Arctic Ocean. The timing of melt onset for 2013 was in general unremarkable. Ice extent remains below average on the Atlantic side of the Arctic, and near average in the Beaufort and Chukchi seas, and along the Eurasian coast.

Overview of conditions

Figure 1. Arctic sea ice extent for July 2013 was 8.5 million square kilometers (3.26 million square miles). The magenta line shows the 1981 to 2010 median extent for that month. The black cross indicates the geographic North Pole.  Sea Ice Index data. About the data||Credit: National Snow and Ice Data Center|High-resolution image

Figure 1. Arctic sea ice extent for July 2013 was 8.45 million square kilometers (3.26 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 July 2013 averaged 8.45 million square kilometers (3.26 million square miles). This is 1.25 million square kilometers (483,000 square miles) below the 1981 to 2010 average for the month (Note that on July 2, 2013, NSIDC began using a new 30-year baseline for analyzing sea ice.). Ice extent remains below average on the Atlantic side of the Arctic, and is near average to locally above average in the Beaufort and Chukchi seas and along much of the Eurasian coast.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 4, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. 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 4, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

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

While sea ice extent retreated rapidly through the first two weeks of July when the weather was dominated by high pressure and clockwise winds over the central Arctic Ocean, the pace of ice loss for the last half of the month was slower. This was partly due to the return of a stormy pattern that brought more counterclockwise winds and cool conditions, and spread the ice out. This spreading of the ice, or ice divergence, can result in more dark open water areas between individual floes that enhance absorption of the sun’s energy, leading to more lateral and basal melting. However, the effects of cooler conditions and ice divergence on the overall ice extent depend in part on the thickness of the ice. Historically, stormy summers tended to end up with more ice than summers characterized by high pressure and few storms. As the ice cover has thinned, stormy conditions may actually help to remove more ice.

July 2013 compared to previous years

Figure 3. Monthly July ice extent for 1979 to 2013 shows a decline of 7.14% per decade relative to the 1981 to 2010 average.||Credit: National Snow and Ice Data Center|High-resolution image

Figure 3. Monthly July ice extent for 1979 to 2013 shows a decline of 7.4% per decade relative to the 1981 to 2010 average.

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

Overall, extent dropped an average of 105,000 square kilometers (41,000 square miles) per day through the month, the second fastest July ice loss in the satellite record after 2007, and much higher than the 1981 to 2010 average. However, this number averages the rapid ice loss during the first half of the month with the slower loss during the second half of the month. July 2013 was the fifth lowest July in the 1979 to 2013 satellite record, and 540,000 square kilometers (208,000 square miles) above the record low in 2011. The monthly trend is ‑7.4% per decade relative to the 1981 to 2010 average (also ‑7.1% per decade relative to the old 1979 to 2000 baseline).

Summer storms

Summer is the stormiest season over the central Arctic Ocean, but the situation can vary greatly within a month (as has been the case for July 2013), from month to month, and year to year. The summer storms in this region can occasionally be quite strong and there has been some discussion that, like hurricanes, strong Arctic storms should be named, perhaps drawing on the Inuit language. Last August, a cyclone in the region attained a central pressure as low as 964 hPa, with attendant strong winds. As just discussed, summers characterized by stormy conditions tend to end up with more sea ice than summers characterized by high pressure. However, the effects of an individual strong storm can be complex. It appears that the August 2012 storm was attended by a modest acceleration in the pace of summer ice loss. While the middle of July 2013 also saw a storm over the central Arctic Ocean with a central pressure of 977 hPa, this year’s event has not led to a strong ice loss.

A note on melt ponds

Figure4

Figure 4. These comparison images show the North Pole Web Cam on July 25, 2013 (top), and July 30, 2013 (bottom).

Credit: North Pole Environmental Observatory
High-resolution image

There have been confusion and misinformation on several Arctic- and climate-focused Web blogs regarding the presence of a lake at the North Pole, as viewed from the North Pole Webcam, which is part of the North Pole Environmental Observatory (NPEO). First, the webcam is not at the North Pole. Because of the drift of the ice, as of this week it is actually located at about 84 degrees North near the prime meridian. Second, the so-called lake is nothing more than a large summer melt pond atop the ice cover, and is not, as some have said, a hole or a polynya in the ice cover. While quite extensive by July 26, the pond appears to have largely disappeared by July 30, by draining off the sea perhaps through a fracture, followed by a dusting of snow. See the NPEO’s FAQ on the melt ponding this year.

*Note: A reader called our attention to details in the North Pole Web Cam images of the recent melt pond. After examining these and conferring with other researchers, we have revised the sentence that reads: “While quite extensive by July 26, the pond appears to have largely disappeared by July 30 under what is probably a thin layer of ice covered with a dusting of snow.” The updated version now reads “While quite extensive by July 26, the pond appears to have largely disappeared by July 30, by draining off the sea perhaps through a fracture, followed by a dusting of snow.”

 Onset of summer melt

Figure 5. The graph above compares melt onset dates for sectors of the Arctic Ocean. ||Credit: National Snow and Ice Data Center| High-resolution image

Figure 5. The graph above compares melt onset dates for sectors of the Arctic Ocean.

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

The same satellite passive microwave data that NSIDC uses to determine sea ice extent can also be used to determine the date of the onset of summer melt over the sea ice cover. Compared to the average over the period 1981 to 2010, the date of melt onset, as assessed for different sectors of the Arctic Ocean, was largely unremarkable. It was slightly earlier than average in some sectors but later than average in others.

Further reading

Serreze, M. C. and A. P. Barrett. 2008. The summer cyclone maximum over the central Arctic Ocean. Journal of Climate 21, doi:10.1175/2007JCLI1810.1.

Kwok, R. and N. Untersteiner. 2011. The thinning of the Arctic sea ice. Physics Today 64(4), April 2011, doi:10.1063/1.3580491.

Rosel, A., L. Kaleschke, and G. Birnbaum. 2011. Melt ponds on Arctic sea ice determined from MODIS satellite data using an artificial neural network. The Cryosphere Discussions 5, 2991–3024, doi:10.5194/tcd-5-2991-2011.

 

A change of pace

Sea ice extent retreated fairly rapidly through the first two weeks of July as a high pressure cell moved into the central Arctic, bringing warmer temperatures over much of the Arctic Ocean. Ice extent remains below average on the Atlantic side of the Arctic, and is near average to locally above average in the Beaufort and Chukchi seas and along much of the Eurasian coast.

Overview of conditions

Figure 1. Arctic sea ice extent for July 15, 2013 was 8.20 million square kilometers (3.17 million square miles). The orange 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

While the rate of Arctic sea ice loss is normally fastest during July, the warmest month of the year, ice loss was even faster than usual over the first two weeks of July 2013. As a result, on July 15 extent came within 540,000 square kilometers (208,000 square miles) of that seen in 2012 on the same date. The ice loss is dominated by retreat on the Atlantic side of the Arctic, including the East Greenland, Kara and Laptev seas, and Baffin Bay. In the Beaufort and Chukchi seas and much of the Eurasian coast, the ice cover remains fairly extensive, especially compared to recent summers. Compared to the 1981 to 2010 average, ice extent on July 15, 2013 was 1.06 million square kilometers (409,000 square miles) below average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of July 15, 2013, along with daily ice extent data for 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

During the first two weeks of July, ice extent declined at a rate of 132,000 square kilometers (51,000 square miles) per day. This was 61% faster than the average rate of decline over the period 1981 to 2010 of 82,000 square kilometers (32,000 square miles) per day. The fast pace of ice loss was dominated by retreat in the Kara and East Greenland seas, where the ice loss rate from July 1 to 12 was -16,409 and -17,678 square kilometers (-6,336 and -6,826 square miles) per day, respectively. The Laptev Sea ice retreated at about half that rate, at -8,810 square kilometers (-3,402 square miles) per day.  In contrast, on the Pacific side, sea ice has been slow to retreat. During the first part of July, the rate of ice loss in the Beaufort and Chukchi seas was only -3,375 and -6,829 square kilometers (-1,303 and -2,637 square miles), respectively.

A change in the weather

Figure 3a

Figure 3a. This image of air temperature anomalies at the 925 hPa level from July 1 to 10 July 10, 2013 shows higher than average temperatures over the Arctic, especially over the Kara Sea. Air temperature anomalies are relative to the 1981 to 2010 average.

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

Fig3b

Figure 3b. This image of average sea level pressure from July 1 to 10, 2013 shows high pressure in the central Arctic.

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

Temperatures at the 925 hPa level for the first two weeks in July were 1 to 3 degrees Celsius (2 to 5 degrees Fahrenheit) above average over much of the Arctic Ocean and as much as 5 degrees Celsius (9 degrees Fahrenheit) above average over the Kara Sea, where ice loss was pronounced. In contrast, temperatures over Alaska, Siberia and the Canadian Arctic were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) lower than average.

Warmer conditions have been paired with a shift in the atmospheric circulation, with a high pressure cell at sea level pressure moving into the central Arctic, replacing then pattern of low pressure that dominated the month of June. This has helped to bring in warm air from the south over the Arctic Ocean. This pattern has also helped to create open water areas in the Laptev Sea because offshore winds push the ice away from shore.

 

Slow ice retreat along coastal Alaska and Canada

Figure 4.

Figure 4. This graph of sea ice extent in the Beaufort and Chukchi Seas as of July 12 each year shows an increase in ice extent in the Beaufort Sea over the last seven summers.

Credit: NSIDC
High-resolution image

The slow retreat of sea ice in the Beaufort Sea has resulted in the most extensive ice cover seen there in the last seven summers (Figure 4). Ice extent also remains rather extensive in the Chukchi Sea, though other recent years have seen more ice at this same time of year, particularly in 2012, when Shell was forced to delay drilling operations and reduce the number of wells planned. Despite extensive ice cover, visible imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument shows melt is well underway.

A new normal for Arctic sea ice

Arctic sea ice continues to track below average but remains well above the levels seen last year. The relatively slow ice loss is a reflection of the prevailing temperature and wind patterns. As of July 1, NSIDC Arctic Sea Ice News and Analysis and the Sea Ice Index have transitioned to a new 30-year baseline period, 1981 to 2010.

Overview of conditions

June 2013 sea ice extent

Figure 1. Arctic sea ice extent for June 2013 was 11.58 million square kilometers (4.47 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

June is a transition period for Arctic sea ice as 24-hour daylight reigns, and melt reaches towards the North Pole. Thus it is an appropriate time for NSIDC to transition to a new 30-year baseline period, also called a “climate normal.” The satellite record is now long enough to allow NSIDC to match current National Ocean and Atmospheric Administration (NOAA) and World Meteorological Organization (WMO) standard baselines of 1981 to 2010 for weather and climate data. Full details of the changes and the implications for NSIDC sea ice statistics are described in the NSIDC Sea Ice Index.

Average sea ice extent for June 2013 was 11.58 million square kilometers (4.47 million square miles). This was 310,000 square kilometers (120,000 square miles) below the 1981 to 2010 average (the new baseline period) of 11.89 million square kilometers (4.59 million square miles). In comparison, the 1979 to 2000 period that we previously used averaged 12.16 million square kilometers (4.70 million square miles). June 2013 was 760,000 square kilometers (293,000 square miles) above the record low June extent in 2010.

Conditions in context

graph of sea ice extent

Figure 2a. The graph above shows Arctic sea ice extent as of June 30, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 in purple. The 1981 to 2010 average is in dark gray. Sea Ice Index data.

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

graph with both  baselines

Figure 2b. The graph above shows Arctic sea ice extent as of June 30, 2013, along with daily ice extent data for 2012, the record low year, and both the new and old baseline average periods. The 1981 to 2010 average is shown by a dark gray line. The gray area around this average line shows the two standard deviation range of the 1981 to 2010 average. The 1979 to 2000 average is shown by a blue line. The light purple shading around this line shows the two standard deviation range of the 1979 to 2000 average.

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

Although the rate of ice loss increased toward the end of June, overall ice has retreated more slowly this summer compared to last summer, reflecting patterns of atmospheric circulation and air temperature. Average June temperatures at the 925 mb level were average to slightly below average over most of the Arctic Ocean, contrasting with above average temperatures over most of the surrounding land. This temperature pattern is associated with unusually low sea level pressure centered near the North Pole. This type of circulation pattern is known to slow the summer retreat of ice, not just because it fosters cool conditions, but also because the pattern of cyclonic (counterclockwise) winds tends to spread the ice out. An interesting regional aspect of this pattern is that on the heels of unusually cold spring conditions, the Alaska interior experienced some days of record high temperatures during June.

 

June 2013 compared to previous years

Monthly June ice extent

Figure 3. Monthly June ice extent for 1979 to 2013 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

Sea ice extent declined steadily through most of the month, in sharp contrast to last year when June experienced a record fast pace of sea ice retreat. There was a speed-up in ice loss toward the end of the month. Overall, extent dropped an average of 70,300 square kilometers (27,000 square miles) per day through the month, slightly higher than the 1981 to 2010 average.

June 2013 was the 11th lowest June in the 1979 to 2013 satellite record, 760,000 square kilometers (293,000 square miles) above the record low in 2010. The monthly trend is -3.6% percent per decade relative to the 1981 to 2010 average (also -3.6% per decade relative to the old 1979 to 2000 baseline).

An Arctic pre-conditioned for rapid summer ice loss?

Figure 4. Data from NASA Operation IceBridge flights over the Arctic Ocean during March and April 2013 indicate

Figure 4. Data from NASA Operation IceBridge flights over the Arctic Ocean during March and April 2013 indicate thick ice along the Greenland coast (shown in reds), but thin ice north of Alaska (blues and greens).

Credit: National Snow and Ice Data Center/NASA Operation IceBridge
High-resolution image

Through most of June, we did not see the precipitous decline in ice extent that was observed in June 2012 and 2007 (the years with the lowest and second lowest September ice extent in the satellite record). However, the rate of ice loss did increase in late June. Ice cover this spring was very thin in parts of the Arctic, suggesting that large areas may soon start melting out completely. Much depends on whether the atmospheric circulation pattern seen in June persists through July.

NASA Operation IceBridge data collected during March and April indicated thick ice along the Greenland coast (5 meters, or 16 feet or more), but thin ice north of Alaska in the Beaufort and Chukchi seas, ranging from 1 to 1.5 meters (3 to 5 feet) in most areas and as low as 0.5 meters (approximately 2 feet) in others. These thin areas are quite likely refrozen leads, linked to the major fracturing events that occurred in the region during February and March. According to Andrew Shepherd at the University of Leeds, preliminary results from the European Space Agency CryoSat satellite suggest that the ice pack was 8% thinner in March 2013 compared to March 2012.

An ocean of small floes

figure5

Figure 5. High-resolution passive microwave data from AMSR2 on June 26, 2013 (left image) shows areas of low ice concentration near the North Pole, indicated in greens. Visible imagery from MODIS on June 27, 2013 (right image) of the inset area reveals a fractured ice surface with small floes.

Credit: University of Bremen/AMSR2; NASA/GSFC, Rapid Response
High-resolution image

High-resolution passive microwave concentration data from the Japan Aerospace Exploration Agency AMSR2 sensor, produced by the University of Bremen, indicate a highly unusual region of broken-up ice near the North Pole. Development of this low concentration ice may have been assisted by the cyclonic atmospheric pattern noted earlier.

While the AMSR2 image in Figure 5 suggests concentrations as low as 50%, visible imagery from the MODIS sensor on the NASA Aqua satellite indicate that AMSR2 is underestimating concentration, likely due to biases from surface melt.

Still, the MODIS data do confirm that the ice is highly fractured with numerous small floes. Such small floes are more easily melted from the sides and the bottom by ocean waters that are exposed to the 24-hour sunlight. It remains to be seen how many of these small floes will ultimately melt completely.

Updating the sea ice baseline

This July, NSIDC plans to change the baseline climatological period for Arctic Sea Ice News and Analysis and the Sea Ice Index, the data set we use for our sea ice analysis. We are making this change to match the comparison time frames used by other climate research.

Until now, we have used the 22-year period 1979 to 2000 when comparing current sea ice extent to past conditions. When NSIDC first began to monitor and analyze sea ice extent, a longer period was not available. Since the satellite record is now extended, we are choosing to move to a more standard 30-year reference period, from 1981 to 2010.

A 30-year period typically defines a climatology (comparsion period) and is the standard used by organizations such as the World Meteorological Organization (WMO) and the U.S. National Oceanic and Atmospheric Administration (NOAA). Thirty years is considered long enough to average out most variability from year to year, but short enough so that longer-term climate trends are not obscured.

These maxims about climate averages come from the world of weather and climate. Sea ice responds to changes in energy or heat differently from other systems on Earth. So the assumptions behind the use of 30-year averages for weather may not hold true for sea ice, particularly in light of the rapid decrease and repeated record low minimum extents in the Arctic during the past decade. However, matching the 1981 to 2010 period brings us in line with other climate research.

The monthly and daily sea ice extent images and data values will not change, but data and images that are based on the average or median will change. For example, the trend plot for sea ice extent will have a different scale, and the value of the slope, expressed as change in percent per decade, will change, because this value is relative to the average period. On the the monthly and daily extent images, the position of the average extent lines will change.

In our July analysis, we will provide more information to help readers put these changes into the larger context of changing climate and changing ice.

Un-baked Alaska

Arctic sea ice extent declined at a near-average rate through May, but overall it remained below average compared to the 1979 to 2000 average. The Arctic Oscillation (AO) varied through the month between modest positive and negative phases. Winds from the north and northwest and persistent snow cover over central Alaska made much of the month unusually cold there. The last part of the month saw much higher temperatures.

Overview of conditions

Figure 1. Arctic sea ice extent for May 2013 was 13.10 million square kilometers (5.05 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

Figure 1. Arctic sea ice extent for May 2013 was 13.10 million square kilometers (5.06 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

Sea ice extent in May 2013 averaged 13.10 million square kilometers (5.06 million square miles). This is 500,000 square kilometers (193,000 square miles) below the 1979 to 2000 average for the month. As has been the case for the past several years, ice extent was below average in the Barents Sea on the Atlantic side of the Arctic. Greater than average ice extent prevailed on the Pacific side of the Arctic in the Bering Sea and Sea of Okhotsk.

Conditions in context

Time series graph as of June 14, 2013

Figure 2. The graph above shows Arctic sea ice extent as of June 2, 2013, along with daily ice extent data for five previous years. 2013 is shown in blue, 2012 in green, 2011 in orange, 2010 in pink, 2009 in navy, and 2008 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. Note: 2011 was inadvertently omitted from this graph; corrected June 17. Sea Ice Index data.

Credit: National Snow and Ice Data. High resolution image

The AO varied through the month between modest positive and negative phases. However, May was characterized by a broad region of unusually low pressure covering much of the western Arctic, namely the Beaufort, Chukchi, and East Siberian seas. Earlier large-scale fracturing of the sea ice off the northeast coast of Alaska and north of the Canadian Archipelago mentioned in our past post was linked to a pattern of high pressure over the Arctic and a strongly negative phase of the AO.

There are several open water areas, or polynyas, along the Arctic coast, as is typical for this time of year. Small patches of open water are present along the Laptev Sea coast north of Russia, and at the northern end of Baffin Bay. These will expand as summer melting and warmer conditions progress in the Arctic.

May 2013 compared to previous years

Figure 3. Monthly May ice extent for 1979 to 2013 shows a decline of 2.24% per decade.||Credit: National Snow and Ice Data Center |High-resolution image

Figure 3. Monthly May ice extent for 1979 to 2013 shows a decline of -2.24 percent per decade.

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

May 2013 was the tenth lowest May in the satellite record, 390,000 square kilometers (151,000 square miles) above the record low of 12.58 million square kilometers (4.86 million square kilometers) in 2004.*

Through the month of May this year, extent declined at an average rate of 36,400 square kilometers (14,100 square miles) per day, slower than the 1979 to 2000 average of 44,100 square kilometers (17,000 square miles) per day.

*Note: We originally stated that the record low had occurred in May 2011. After reviewing the data, we corrected this statement. See the Sea Ice Index for data on past May ice extent.

Snow cover update

Figure 4. This snow cover anomaly map shows the difference between snow cover for May 2013, compared with average snow cover for May from 1971 to 2000. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than normal. |Credit: National Snow and Ice Data Center, data courtesy Rutgers University Global Snow Lab  High-resolution image

Figure 4. This snow cover anomaly map shows the difference between snow cover for May 2013, compared with average snow cover for May from 1971 to 2000. Areas in orange and red indicate lower than usual snow cover, while regions in blue had more snow than normal.

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

Monthly snow cover anomaly data from the Rutgers University Global Snow Lab  show that snow cover for the month of May was significantly low in eastern Siberia, northern Europe, and the Rocky Mountains in North America. Data also show a few greater-than-average regions in Alaska—contributing to the lower temperatures there—and on  the Tibetan Plateau.

Weekly and daily data from the Global Snow Lab show that May began with greater-than-average snow cover in Tibet and the Great Plains of Canada and the United States. By the end of the month, however, snow extent was near average to lower than average throughout the Northern Hemisphere, and much lower than average in northeastern Siberia. Overall, snow cover in May 2013 was the lowest on record in forty-seven years of data for Eurasia, and third lowest overall for the Northern Hemisphere, trailing only 2012 and 2010.

Chilly in Alaska

Figure 5. This image shows air temperature anomalies at the 925 hPa level averaged for May 2013, compared to averages over the period 1981 to 2010. Temperatures were lower than average over Alaska, while temperatures across much of Siberia were above average. ||Credit: NSIDC courtesy NOAA/ESRL PSDHigh-resolution image

Figure 5. This image shows air temperature anomalies at the 925 hPa level averaged for May 2013, compared to averages over the period 1981 to 2010. Temperatures were lower than average over Alaska, while temperatures across much of Siberia were above average.

Credit: NSIDC courtesy NOAA Earth System Research Laboratory Physical Sciences Division
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Lower than average temperatures were the rule this past month for both Greenland and Alaska, while temperatures across much of Siberia were above average. Temperatures over central Alaska at the 925 hPa level were 4 to 5 degrees Celsius (7 to 9 degrees Fahrenheit) colder than usual, making this one of the coldest springs on record for cities like Fairbanks. These low temperatures can be linked to winds from the north and northwest over central Alaska and persistent snow cover. However, the end of the month saw much higher temperatures, reaching more than 80 degrees Fahrenheit (27 degrees Celsius) in Fairbanks.

Because of the low temperatures, ice on the Tanana River, which runs through Fairbanks, Alaska, broke up on May 20 at 2:41 p.m.—the latest date and time on a record which extends for nearly a century. Ice break-up has been carefully recorded at the town of Nenana, about 70 kilometers (44 miles) downstream on the Tanana River from Fairbanks, by timing the tipping of a large tripod erected on the river ice. This is a matter of some importance for Alaskans, as there is a large statewide lottery based on picking the exact time of ice break-up. In most years, winning this lottery requires picking the time to the precise minute of tipping. Congratulations to Warren and Yvonne Snow, for your excellent climate forecasting (and on having a wonderful last name)!