Author Archives: Natasha Vizcarra

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.

 

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
High-resolution image

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)!

 

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 .

Annual maximum extent reached

On March 15, 2013, Arctic sea ice extent appears to have reached its annual maximum extent, marking the beginning of the sea ice melt season. This year’s maximum extent was the sixth lowest in the satellite record. NSIDC will release a detailed analysis of the 2012 to 2013 winter sea ice conditions in early April.

Overview of conditions

Figure 1. Arctic sea ice extent on March 15 was 15.13 million square kilometers (5.84 million square miles). The orange line shows the 1979 to 2000 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 March 15, 2013 Arctic sea ice likely reached its maximum extent for the year, at 15.13 million square kilometers (5.84 million square miles). The maximum extent was 733,000 square kilometers (283,000 square miles) below the 1979 to 2000 average of 15.86 million square kilometers (6.12 million square miles). The maximum occurred five days later than the 1979 to 2000 average date of March 10. The date of the maximum has varied considerably over the years, with the earliest maximum in the satellite record occurring as early as February 24 in 1996 and as late as April 2 in 2010.

This year’s maximum ice extent was the sixth lowest in the satellite record. The lowest maximum extent occurred in 2011. The ten lowest maximums in the satellite record have occurred in the last ten years, 2004 to 2013.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of March 24, 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

Over the 2012 to 2013 winter season, sea ice extent grew a record 11.72 million square kilometers (4.53 million square miles). The record growth was primarily a result of the record low minimum last September, leaving a greater extent of ocean surface uncovered in ice to re-freeze this winter. This seasonal ice gain is 645,000 square kilometers (249,000 square miles) higher than the previous record (2007 to 2008) and 2.63 million square kilometer (1.02 million square miles) higher than the 1979 to 2000 average. Last autumn’s record low and this winter’s record ice growth indicate a more pronounced seasonal cycle in Arctic sea ice and the increasing dominance of first-year ice in the Arctic.

Final analysis pending

At the beginning of April, NSIDC scientists will release a full analysis of winter conditions, along with monthly data for March. For more information about the maximum extent and what it means, see the NSIDC Icelights post, the Arctic sea ice maximum. For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

A wintry mix from a dynamic cryosphere

Arctic sea ice extent for January 2013 was well below average, largely due to extensive open water in the Barents Sea and near Svalbard. The Arctic Oscillation also remained in a primarily negative phase. Antarctic sea ice remained extensive due to an unusual northward excursion of ice in the Weddell Sea. December of 2012 saw Northern Hemisphere snow cover at a record high extent, while January 2013 is the sixth-highest snow cover extent on record since 1967.

Overview of conditions

Figure 1. Arctic sea ice extent for January 2013 was 13.78 million square kilometers (5.32 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

The average sea ice extent for January 2013 was 13.78 million square kilometers (5.32 million square miles). This is 1.06 million square kilometers (409,000 square miles) below the 1979 to 2000 average for the month, and is the sixth-lowest January extent in the satellite record. The last ten years (2004 to 2013) have seen the ten lowest January extents in the satellite record.

As has been the case throughout this winter, ice extent in the Atlantic sector of the Arctic Ocean remained far below average. While the Kara Sea was completely iced over, nearly all of the Barents Sea remained ice free, and open water was present north of the Svalbard Archipelago. The lack of winter ice in the Barents Sea and the vicinity of Svalbard has been a common feature of recent years. Recent work by Vladimir Alexeev and colleagues at the University of Alaska Fairbanks provides further evidence that this is related to a stronger inflow of warm waters from the Atlantic as compared to past decades. On the Pacific side, the ice edge in the Bering Sea continued to extend slightly further to the south than usual.

Also, a new paper by Jinlin Zhang and colleagues at the University of Washington analyzed the effect of the strong August 2012 cyclone on last year’s record sea ice minimum. While they found a large effect in the immediate wake of the storm, the effect declined quickly and overall it had only a small effect on the final September minimum extent.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of February 4, 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

Through the month of January, the Arctic gained 1.36 million square kilometers of ice (525,000 square miles), which is slightly higher than 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 much of the Arctic Ocean. Conditions were especially warmer than average near Svalbard where ice-free conditions persist. Below average temperatures characterized parts of northern Eurasia and northwestern Canada. The dominant feature of the Arctic sea level pressure field for January 2013 was unusually high pressure over the central Arctic Ocean, consistent with a predominantly negative phase of the Arctic Oscillation.

January 2013 compared to previous years

Figure 3. Monthly January ice extent for 1979 to 2013 shows a decline of -3.2% per decade.

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

Average Arctic sea ice extent for January 2013 was the sixth lowest for the month in the satellite record. Through 2013, the linear rate of decline for January ice extent is -3.2 percent per decade relative to the 1979 to 2000 average.

Looking at Northern Hemisphere snow

Figure 4. This graphs shows snow cover extent anomaly in the Northern Hemisphere for January from 1967 to 2013. January 2013 is the sixth-highest snow cover extent on record since 1967. The anomaly is relative to the 1971 to 2000 average.

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

As noted in a previous post, Northern Hemisphere snow cover extent for June 2012 set a record low, continuing a downward trend in springtime snow extent. Satellite data from the Rutgers University Global Snow Lab show that after Northern Hemisphere snow cover extent for December 2012 reached a record high for the month of 46.27 million square kilometers (17.86 million square miles), extent during January increased to a monthly average of 48.64 million square kilometers (18.78 million square miles). This was the sixth-highest January extent in the record, dating back to 1967. Snow cover was higher than average throughout much of the western United States as well as northern Europe and eastern China. Snow cover was lower than normal over the central U.S., and much of southern Asia, including the Tibetan Plateau.

A visit to Antarctica

Figure 5. The pattern of Antarctic sea ice extent for January 2013 features an unusual northwards (towards the equator) excursion of sea ice in the northern Weddell Sea. Antarctic sea ice extent as a whole was more than two standard deviations above average for the month. The magenta line shows the 1979 to 2000 median extent for that month. The black cross indicates the South Pole. Sea Ice Index data. About the data

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

Turning to Antarctica, we note that January 2013 saw an unusual northward (towards the equator) excursion of sea ice in the Weddell Sea. The ice edge was found approximately 200 to 300 kilometers (124 to 186 miles) beyond its typical location. Overall, sea ice extent in the Antarctic was nearly two standard deviations above the mean for most of the month.

The cause of this is very unusual sea ice pattern appears to be persistent high pressure in the region west of the Weddell Sea, across the Antarctic Peninsula to the Bellingshausen Sea. This pressure pattern means that winds are tending to blow to the north on the east side of the Peninsula, both moving the ice northward and bringing in cold air from southern latitudes to reduce surface melting of the ice as it moves north.

Intense Greenland surface melting inspires new Web site

In recent years, the surface of the Greenland Ice Sheet has experienced strong melting, but the 2012 melt season far exceeded all previous years of satellite monitoring, and led to significant amounts of ice loss for the year. NSIDC’s new Web site, Greenland Ice Sheet Today presents images of the widespread surface melt on Greenland during 2012 and scientific commentary on the year’s record-breaking melt extent.

Throughout the coming year, the site will offer daily satellite images of surface melting and periodic analysis by the NSIDC science team. NSIDC scientists at the University of Colorado Boulder developed Greenland Ice Sheet Today with data from Thomas Mote of the University of Georgia, and additional collaboration from Marco Tedesco of the City University of New York.

The Greenland Ice Sheet contains a massive amount of fresh water, which if added to the ocean could raise sea levels enough to flood many coastal areas where people live around the world. The ice sheet normally gains snow during winter and melts some during the summer, but in recent decades its mass has been dwindling.

Further reading

Alexeev, V.A., Ivanov, V.V., Kwok, K., and Smedsrud, L.H. 2013. North Atlantic warming and declining volume of arctic sea ice. The Cryosphere Discussions 7, 245-265, doi: 10.519/tcd-7-245-2013.

Zhang, J., R. Lindsay, A. Schweiger, and M. Steele. 2013. The impact of an intense summer cyclone on 2012 Arctic sea ice retreat. Geophysical Research Letters, In press, doi: 10.1002/grl.50190.

Arctic Oscillation switches to negative phase

Arctic sea ice extent for December 2012 remained far below average, driven by anomalously low ice conditions in the Kara, Barents, and Labrador seas. Thus far, the winter has been dominated by the negative phase of the Arctic Oscillation, bringing colder than average conditions to Scandinavia, Siberia, Alaska, and Canada.

Overview of conditions

Figure 1. Arctic sea ice extent for December 2012 was 12.20 million square kilometers (4.71 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

The average sea ice extent for December 2012 was 12.20 million square kilometers (4.71 million square miles). This is 1.16 million square kilometers (448,000 square miles) below the 1979 to 2000 average for the month, and is the second-lowest December extent in the satellite record.

At the end of December, ice extent in the Atlantic sector remained far below normal, as parts of the Kara and Barents seas remained ice-free. Ice has also been slow to form in the Labrador Sea, while Hudson Bay is now completely iced over. On the Pacific side, ice extent is slightly above normal, with the ice edge in the Bering Sea extending further to the south than usual. The Bering Sea has seen above-average winter ice extent in recent years and is the only region of the Arctic that has exhibited a slightly positive trend in ice extent during the winter months.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of January 7, 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

Although the Arctic gained 2.33 million square kilometers of ice (900,000 square miles) through the month, ice extent in the region remained far below average. Ice growth remained slow in the Kara and Barents seas where air temperatures were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) higher than normal. Air temperatures over Greenland and the Canadian Archipelago were also slightly above average, while temperatures over Alaska were 2 to 7 degrees Celsius (4 to 13 degrees Fahrenheit) lower than average.

Winter sea ice variability is largely confined to the peripheral seas surrounding the Arctic Ocean. In the past, the dominant pattern of winter sea ice variability showed a distinct out-of-phase relationship between the Labrador and Greenland-Barents seas, with a less prominent seesaw pattern in the Pacific sector, between the Bering Sea and the Sea of Okhotsk. In recent winters however, this out-of-phase relationship no longer appears to hold in the Atlantic sector. Ice extent has remained below average in both the Labrador and the Barents seas.

Successive winters with anomalously low sea ice in the North Atlantic have led to higher mortality rates for seals in the region. The United States government recently added the bearded and ringed seals to the list of creatures threatened under the Endangered Species Act.

December 2012 compared to previous years

Figure 3. Monthly December ice extent for 1979 to 2012 shows a decline of -3.5(+/-0.6)% per decade.

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

Average Arctic sea ice extent for December 2012 was the second lowest for the month in the satellite record. Through 2012, the linear rate of decline for December ice extent is -3.5 percent per decade relative to the 1979 to 2000 average. While the winter ice extent for the Arctic as a whole shows only modest declines, large negative trends are now found in nearly all of the peripheral seas, with the exception of the Bering Sea.

Negative Arctic Oscillation

Figure 4. This image shows sea level pressure anomalies averaged for December 2012, compared to averages over the period 1981 to 2010. Sea level pressure was above average over Eurasia, extending into the Kara and Barents seas, and across Greenland and the Canadian Archipelago.

Credit: NSIDC courtesy NOAA/ESRL PSD
High-resolution image

The most important mode of variation in the Arctic’s winter atmospheric circulation is the Arctic Oscillation. When the Arctic Oscillation is in a negative mode or phase, sea level pressure is higher than normal over the central Arctic and lower than normal over middle latitudes. This pattern tends to keep the high Arctic relatively warm. It brings colder weather to Europe and North America because air masses can cross into and out of the high Arctic more easily. This pattern tends to favor the retention of thick ice in the Arctic basin by reducing the outflow of ice through the Fram Strait and strengthening the Beaufort Gyre, a clockwise circular pattern of ice drift in the central Arctic. The opposite conditions generally hold for a positive Arctic Oscillation pattern.

The specific influence of this winter’s negative Arctic Oscillation will depend not only on the strength of the sea level pressure anomaly, but also on the location of the sea level pressure center of action. While a negative Arctic Oscillation pattern tends to favor more ice in summer, this was not the case during the extreme negative Arctic Oscillation winter of 2009 to 2010.

The overall effect on the ice cover remains to be seen. Recent studies have argued that that strong warming of the atmosphere in autumn from summer sea ice loss favor the negative Arctic Oscillation phase.

2012 Year in Review

Figure 5. The graph above shows January to December Arctic sea ice extent for the two lowest extent years in the satellite record. Year 2012 is shown in blue and 2007 is shown in green. The 1981 to 2010 average is shown in light blue while the 1979 to 2000 average is in dark gray. Sea Ice Index data. About the data

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

While the year began with lower than average extent for the Arctic as a whole, extent in the Bering Sea was at record high levels for much of the winter. The seasonal decline of ice extent began slowly, such that in mid-April, extent for the Arctic as a whole was briefly near average levels.

Extent began dropping rapidly beginning in May, and by the end of the melt season on September 16, extent was at the lowest level recorded in the satellite record of 3.41 million square kilometers (1.32 million square miles). While summer weather conditions were not as favorable for ice loss as during 2007, the year of the previous record low, an unusually strong cyclone in August helped to quickly break up the already thin and fragmented ice cover in the Chukchi Sea. This cyclone—remarkable in its intensity and its duration—lasted for thirteen days, of which ten days were spent in the Arctic basin.

While it appears that a record low extent would have been reached even without the cyclone, thinning over the last several decades has made the ice more vulnerable to such storms, compared to earlier decades when the Arctic Ocean was dominated by thick, multiyear ice.

The annual average extent is now declining at a rate of -4.5 percent per decade relative to the 1979 to 2000 average and -4.6 percent per decade relative to the 1981 to 2010 average. The 1981 to 2010 period is the 30-year climatology used by the National Oceanic and Atmospheric Administration (NOAA) for their climate normals. Thirty years is a commonly-used period to define average or normal climate conditions. It is long enough to capture much climate variability, such as the different modes of the Arctic Oscillation, and short enough to be relevant for human timescales, such as agricultural cycles. NOAA updates its climate normals every ten years. For Arctic sea ice, use of the 1981 to 2010 period results in a lower extent than the 1979 to 2000 period, as seen in Figure 5, because the low extents of the last decade are included.

Record low ice extent was not the only remarkable event in the north. In June, Northern Hemisphere land snow cover set a new record for the least amount of snow cover in the 45-year record. A month later, the Greenland ice sheet experienced melt over more than 90 percent of its surface area, the largest melt extent recorded during the satellite data record.

Further reading

Simmonds, I. and I. Rudeva.  2012. The great Arctic cyclone of August 2012. Geophysical Research Letters 39, L23709, doi:10.1029/2012GL054259.

Jaiser, R., K. Dethloff, D. Handorf, A. Rinke, and J. Cohen. 2011. Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation. Tellus A, 64, 11595, doi:10.3402/tellusa.v64i0.11595.

Stroeve, J. C., J. Maslanik, M. C. Serreze, I. Rigor, W. Meier, and C. Fowler. 2011. Sea ice response to an extreme negative phase of the Arctic Oscillation during winter 2009/2010, Geophysical Research Letters 38, L02502, doi:10.1029/2010GL045662.

 

 

Open water means a warm Arctic

Autumn over the Arctic Ocean is a season of falling temperatures and rapid growth of sea ice. However, as in recent years, low sea ice extent at the beginning of autumn means large transfers of heat to the atmosphere from open water areas, keeping the Arctic warmer than usual. Despite this warmth, freeze up is in high gear.

Overview of conditions

Figure 1. Arctic sea ice extent for October 15, 2012 was 5.18 million square kilometers (2.00 million square miles). The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

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

As of October 15, sea ice extent stood at 5.18 million square kilometers (2.00 million square miles). This is 3.49 million square kilometers (1.35 million square miles) below the 1979 to 2000 mean for this time of year and 70,000 square kilometers (27,000 square miles) below the same date in 2007. Although it is still at record low levels, extent is climbing fast.

Large areas of the Kara, Laptev, East Siberian, Chukchi, and Beaufort seas remain open for hundreds of kilometers offshore. East of Greenland, ice extent is near average.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of October 15, 2012, along with daily ice extent data for the previous five years. 2012 is shown in blue, 2011 in orange, 2010 in pink, 2009 in navy, 2008 in purple, and 2007 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

Arctic sea ice extent is increasing rapidly, at about 100,000 square kilometers (38,600 square miles) per day, expanding southward at the ice edge, as well as northward from the Arctic continental coasts. However, sea ice extent is still at record low levels for the date, compared to the satellite measurement period (1979 to 2012). On October 6, daily sea ice extent climbed above the 2007 record daily minimum (4.17 million square kilometers or 1.61 million square miles), having spent forty days below that level. On October 14, extent went above 5.0 million square kilometers (1.93 million square miles) for the first time since mid-August.

Open water warms the lower atmosphere

Figure 3. This figure shows air temperatures as a function of height and longitude at 75 degrees north latitude. Temperatures are for the period September 20 to October 10, 2012 compared to averages for the years 1981 to 2010. Between longitudes 120 degrees west to 150 degrees west, temperatures more than 4 degrees Celsius (7 degrees Fahrenheit) above normal are found up to the 850 hPa level (roughly 4500 feet above the surface), with temperatures near the surface, in closer proximity to the warming effects of the ocean, more than 6 degrees Celsius (11 degrees Fahrenheit) above normal.

Credit: NSIDC courtesy NOAA/ESRL PSD
High-resolution image

The past decade has seen much stronger increases in air temperature in the Arctic compared to the globe as a whole. While this strong warming, known as Arctic amplification, has a number of causes, a primary one is declining summer sea ice extent. Through summer, solar energy is readily absorbed within expanding areas of dark, open water. When the sun sets, this heat stored in the uppermost layers of the Arctic Ocean is released upwards, keeping the overlying atmosphere unusually warm.

This warming effect has been especially pronounced during the early autumn of 2012. Air temperatures averaged over the most recent thirty days of data are above average over nearly all of the Arctic Ocean. The warmest conditions compared to average are over northwestern Canada and extending into the Beaufort Sea. Here, the effect of heat released from the ocean is augmented by warm, southerly winds, and is linked to a pattern of unusually high pressure centered over the Gulf of Alaska.

Arctic wind patterns support melting, ice export

Figure 4. Sea level pressure for June 2007 to 2012 compared to averages over the period 1981 to 2010. The Arctic dipole anomaly refers to the combination of unusually high pressure over the northern Beaufort Sea and Greenland and unusually low pressure over northern Eurasia.

Credit: NSIDC courtesy NOAA/ESRL PSD
High-resolution image

Recent research led by James Overland of the National Oceanic and Atmospheric Administration (NOAA) and Jennifer Francis of Rutgers University shows that the Arctic dipole anomaly, featuring unusually high pressure over the northern Beaufort Sea and Greenland and unusually low pressure over northeastern Eurasia, has become more common in the early summer of recent years.

As discussed in previous posts, this pattern brings in warm southerly winds along the shores of the East Siberian and Chukchi seas. It favors strong ice melt in these sectors and pushes the ice away from the coast, leaving open water. The pressure pattern also favors the transport of ice out of the Arctic Ocean and into the North Atlantic through Fram Strait.

The Arctic dipole anomaly was very well developed throughout the summer of 2007 and was in part responsible for the very low September ice extent recorded that year (the second lowest in the satellite record). According to Overland and colleagues, no other six-year period matches the intensity and persistence of the June pattern for 2007 to 2012 in the past sixty-three years. The pattern is linked to the general weakening of the circumpolar jet stream and the greater meandering of this wind flow.

Recall from our previous post that the summer of 2012 as a whole saw a somewhat different pattern. Unusually low pressure was present along the Eurasian coastal seas and extended eastward into the Beaufort Sea, most prominently over the East Siberian Sea, with unusually high pressure centered over Greenland and the northern North Atlantic.

Antarctic sea ice extent remains above average

Figure 5. This graph shows the highest extent years for Antarctic sea ice. The blue line shows 2012, the orange line shows 2011, the green line shows 2007, and the pink line shows 2006. 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

Antarctic sea ice extent dropped below record levels seen for the date but remains well above average. Journalists inquired about the cause of gradual growth in wintertime Antarctic sea ice and the record high Antarctic sea ice extent in mid-September despite general climate warming and the dramatic sea ice losses in the Arctic. As we noted in the previous post, researchers cite stronger westerly winds surrounding Antarctica, in contrast to the Arctic. See also the following news stories on Antarctic sea ice, to which NSIDC scientists contributed, under “Further reading” below.

Further reading

Peter Aldhous, “Why sea ice records are poles apart,” New Scientist, October 8, 2012.

Justin Gillis, “Running the numbers on Antarctic sea ice,” New York Times Green blog, October 3, 2012.

Richard Harris, “Scientists watch Antarctica, Arctic sea ice levels,” National Public Radio Morning Edition, October 8, 2012.

Reference

Overland, J. E., J. A. Francis, E. Hanna, and M. Wang. 2012. The recent shift in early summer Arctic atmospheric circulation. Geophysical Research Letters 39, L19804, doi: 10.1029/2012GL053268.

 

Arctic sea ice extent near the minimum

On September 17, Arctic sea ice extent was 3.41 million square kilometers. Within the next couple of days, we expect to announce that the minimum extent has been reached for the year.

Overview of conditions

Figure 1. Arctic sea ice extent for September 17, 2012 was 3.41 million square kilometers (1.32 million square miles). The orange line shows the 1979 to 2000 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

Sea ice extent for September 17 was 3.41 million square kilometers (1.32 million square miles). Weather conditions near the ice edge heavily influence the timing of the minimum, which has occurred as late as September 23. We are now five days past the 1979 to 2000 average minimum date of September 13. The decline has slowed in recent days and the minimum will likely be confirmed any day now.

The current extent is 760,000 square kilometers (293,000 square miles) below the previous record minimum extent in the satellite record (4.17 million square kilometers or 1.61 million square miles) which occurred on September 18, 2007. This difference is larger than the size of the state of Texas. The ice extent currently tracks nearly 50% below the 1979 to 2000 average minimum extent.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of September 17, 2012, along with daily ice extent data for 2007. 2012 is shown in blue and 2007 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

Since September 1, extent declined 316,000 square kilometers (122,000 square miles), or 19,800 square kilometers (7,600 square miles) per day. Freeze up has begun over the high latitude Arctic areas, such as the North Pole, and extent has started to increase in the Beaufort Sea region. However, extent is still decreasing on the Atlantic side of the Arctic, leading to the continued overall decline in recent days. The Northern Sea Route along the coast of Siberia has been largely free of ice since mid August. This is in contrast with 2007, when a persistent tongue of ice reaching the coast of the Laptev Sea clogged the Northern Sea Route.

The Northwest Passage

Figure 3. This time series shows total sea ice area (top) and multiyear ice area (bottom) for selected years within the Western Parry Channel route of the Northwest Passage. The black line with red dots shows 2012, and other colors show ice conditions in different years.

Credit: NSIDC courtesy Stephen Howell, Environment Canada, from Canadian Ice Service data
High-resolution image

The situation in the Northwest Passage this year also contrasts with 2007. Both the narrow and shallow southern route used by the late polar explorer Roald Amundsen and the wide and deep northern route through the Parry Channel opened in 2007. This year only the southern route has opened. According to Stephen Howell of the Canadian Ice Service, rapid ice loss occurred in the Parry Channel in July. However, due in part to the August storm, a subsequent influx of multiyear ice from the north has kept at least some of the channel blocked.

These different patterns of ice loss in the sea routes between 2007 and 2012 highlight how a focus on overall total extent can overshadow regional aspects that have important implications. That 2007 was a record low extent at the time meant nothing to a ship trying to traverse the Northern Sea Route; likewise, the new record this year was meaningless to a ship trying to navigate through the Parry Channel.

Conditions in the Chukchi Sea, where Shell has started to drill for oil, provide another example. Shell’s operations were delayed in part because of greater than expected ice cover in the early summer. In the late summer, although passive microwave data showed that the Chukchi Sea was nearly ice-free, small floes of ice threatened Shell’s drilling platform, forcing the company to temporarily cease operations in the Arctic.

A report from the field

Figure 4. Above are photos of varying sea ice conditions north of Svalbard. The top photo shows shows denser ice cover, around 90% concentration, with a mixture of small floes and brash ice (i.e., slushy ice remnants of melt). The bottom photo shows lower concentrations of small ice floes with considerable open water.

Credit: National Snow and Ice Data Center, Julienne Stroeve

NSIDC scientist Julienne Stroeve has been traveling in the Arctic by ship, taking sea ice and temperature measurements on the Atlantic side of the Arctic Ocean. Her reports also show the regional variability of the ice cover. She reached the ice edge on September 10 at roughly 82 degrees North latitude, 15 degrees East longitude (essentially due north of Svalbard). Concentrations were quite high (around 90%) at the ice edge, but as the ship cruised north, concentration dropped to about 40% with considerable regions of open water.

Since entering the ice, Stroeve has encountered an average of up to 65% ice concentration primarily consisting of small floes (20 to 50 meters, or 66 to 164 feet) of mostly first-year ice. These floes are too small and thin to safely embark on to take measurements. However, the ship eventually found larger floes and Stroeve took ice thickness measurements indicating thicknessess of around 2 meters (6.5 feet). So far, air temperatures have remained above freezing and Stroeve has not observed any ice formation. The surface measurements taken by Stroeve and other scientists on board the ship are useful for validating satellite data and will provide more detail on the state of the sea ice cover. Stroeve sighted several polar bears, including a mother and her cub.

Arctic sea ice extent breaks 2007 record low

Arctic sea ice appears to have broken the 2007 record daily extent and is now the lowest in the satellite era. With two to three more weeks left in the melt season, sea ice continues to track below 2007 daily extents.

Please note that this is not an announcement of the sea ice minimum extent for 2012. NSIDC will release numbers for the 2012 daily minimum extent when it occurs. A full analysis of the melt season will be published in early October, once monthly data are available for September.

Overview of conditions

Figure 1. Arctic sea ice extent for August 26, 2012 (right) was 4.10 million square kilometers (1.58 million square miles), which was 70,000 square kilometers (27,000 square miles) below the September 18, 2007 daily extent of 4.17 million square kilometers (1.61 million square miles, left). The orange line shows the 1979 to 2000 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 images: Figure 1a , Figure 1b

Arctic sea ice extent fell to 4.10 million square kilometers (1.58 million square miles) on August 26, 2012. This was 70,000 square kilometers (27,000 square miles) below the September 18, 2007 daily extent of 4.17 million square kilometers (1.61 million square miles).

Including this year, the six lowest ice extents in the satellite record have occurred in the last six years (2007 to 2012).

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 26, 2012, along with daily ice extent data for 2007, the previous record low year, and 1980, the record high year. 2012 is shown in blue, 2007 in green, and 1980 in orange. 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. The 1981 to 2010 average is in sky blue. Sea Ice Index data.

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

 

 

After tracking near 2007 levels through July, the extent declined rapidly in early August. Since then, the loss rate has slowed some, averaging about 75,000 square kilometers (29,000 square miles) per day—equivalent to the size of the state of South Carolina. However, this is still much faster than the normal rate at this time of year of about 40,000 square kilometers per day (15,000 square miles).

Note that the date and extent of the 2007 minimum have changed since we originally posted in 2007; see our Frequently Asked Questions for more information.

 

 

 

 

 

 

A summer storm in the Arctic

Arctic sea ice extent during the first two weeks of August continued to track below 2007 record low daily ice extents. As of August 13, ice extent was already among the four lowest summer minimum extents in the satellite record, with about five weeks still remaining in the melt season. Sea ice extent dropped rapidly between August 4 and August 8. While this drop coincided with an intense storm over the central Arctic Ocean, it is unclear if the storm prompted the rapid ice loss. Overall, weather patterns in the Arctic Ocean through the summer of 2012 have been a mixed bag, with no consistent pattern.

Overview of conditions

Figure 1. Arctic sea ice extent for August 13, 2012 was 5.09 million square kilometers (1.97 million square miles), 483,000 square kilometers (186,000 square miles) below the same day in 2007. The orange line shows the 1979 to 2000 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

Arctic sea ice extent on August 13 was 5.09 million square kilometers (1.97 million square miles). This is 2.69 million square kilometers (1.04 million square miles) below the 1979 to 2000 average extent for the date, and is 483,000 square kilometers (186,000 square miles) below the previous record low for the date, which occurred in 2007. ( Note: The sea ice extent originally published on August 14, 2012 was the actual one-day value for August 13. We normally report the five-day trailing mean, so to be consistent we have updated the post with these numbers instead of the one-day value. See the Sea Ice Index Documentation for more information about the five-day trailing mean.) Low extent for the Arctic as a whole is driven by extensive open water on the Atlantic side of the Arctic, the Beaufort Sea, and—due to rapid ice loss over the past two weeks—the East Siberian Sea. Ice is near its normal (1979 to 2000) extent only off the northeastern Greenland coast. Ice near the coast in eastern Siberia continues to block sections of the Northern Sea Route. The western entrance to the Northwest Passage via McClure Strait remains blocked.

Conditions in context

Figure 2. The graph above shows Arctic sea ice extent as of August 13, 2012, along with daily ice extent data for the previous five years. 2012 is shown in blue, 2011 in orange, 2010 in pink, 2009 in navy, 2008 in purple, and 2007 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

The average pace of ice loss since late June has been rapid at just over 100,000 square kilometers (38,000 square miles) per day. However, this pace nearly doubled for a few days in early August during a major Arctic cyclonic storm, discussed below. Unlike the summer of 2007 when a persistent pattern of high pressure was present over the central Arctic Ocean and a pattern of low pressure was over the northern Eurasian coast, the summer of 2012 has been characterized by variable conditions. Air tempertures at the 925 hPa level (about 3000 feet above the ocean surface) of 1 to 3 degrees Celsius (1.8 to 5.4 degrees Fahrenheit) above the 1981 to 2012 average have been the rule from central Greenland, northern Canada, and Alaska northward into the central Arctic Ocean. Cooler than average conditions (1 to 2 degrees Celsius or 1.8 to 3.6 degrees Fahrenheit) were observed in a small region of eastern Siberia extending into the East Siberian Sea, helping explain the persistence of low concentration ice in this region through early August.

The Great Arctic Cyclone of 2012

Figure 3. This subsection of the surface weather analysis from the Canadian Meteorological Centre for August 6, 2012 (at 0600 Greenwich Mean Time) shows a very strong cyclone over the central Arctic Ocean north of Alaska. The isobars (lines of equal pressure) are very tightly packed around the low pressure system, indicating strong winds. Greenland is on the right side of the figure while Canada is at the bottom.

Credit: Canadian Meteorological Centre
High-resolution image

A low pressure system entered the Arctic Ocean from the eastern Siberian coast on August 4 and then strengthened rapidly over the central Arctic Ocean. On August 6 the central pressure of the cyclone reached 964 hPa, an extremely low value for this region. It persisted over the central Arctic Ocean over the next several days, and slowly dissipated. The storm initially brought warm and very windy conditions to the Chukchi and East Siberian seas (August 5), but low temperatures prevailed later.

Figure 4. These maps of sea ice concentration from the Special Sensor Microwave Imager/Sounder (SSMIS) passive microwave sensor highlight the very rapid loss of ice in the western Arctic (northwest of Alaska) during the strong Arctic storm. Magenta and purple colors indicate ice concentration near 100%; yellow, green, and pale blue indicate 60% to 20% ice concentration.

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

Low pressure systems over the Arctic Ocean tend to cause the ice to diverge or spread out and cover a larger area. These storms often bring cool conditions and even snowfall. In contrast, high pressure systems over the Arctic cause the sea ice to converge. Summers dominated by low pressure systems over the central Arctic Ocean tend to end up with greater ice extent than summers dominated by high pressure systems.

However, the effects of an individual strong storm, like that observed in early August, can be complex. While much of the region influenced by the August cyclone experienced a sudden drop in temperature, areas influenced by winds from the south experienced a rise in temperature. Coincident with the storm, a large area of low concentration ice in the East Siberian Sea (concentrations typically below 50%) rapidly melted out. On three consecutive days (August 7, 8, and 9), sea ice extent dropped by nearly 200,000 square kilometers (77,220 square miles). This could be due to mechanical break up of the ice and increased melting by strong winds and wave action during the storm. However, it may be simply a coincidence of timing, given that the low concentration ice in the region was already poised to rapidly melt out.

Further Reading

Long, Z. and W. Perrie. 2012. Air-sea interactions during an Arctic storm. Journal of Geophysical Research, 117, D15103, doi:10.1029/2011JD016985.

Screen, J. A., I. Simmonds, and K. Keay. 2011. Dramatic interannual changes of perennial Arctic sea ice linked to abnormal summer storm activity. Journal of Geophysical Research, 116, D15105, doi:10.1029/2011JD015847.

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.