Arctic sea ice minimum press release

Please see the NSIDC press release, Arctic sea ice extent remains low; 2009 sees third-lowest mark, for a detailed analysis of this year’s Arctic sea ice minimum and a synopsis of the 2009 melt season. Note that analysis will continue to be posted on the Arctic Sea Ice News & Analysis Web site approximately once a month throughout the year, or more often as conditions warrant.

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

Arctic sea ice reaches annual minimum extent

Arctic sea ice appears to have reached its minimum extent for the year, the third-lowest extent since the start of satellite measurements in 1979. While this year’s minimum extent is above the record and near-record minimums of the last two years, it further reinforces the strong negative trend in summertime ice extent observed over the past thirty years.

map from space showing sea ice extent, continentsFigure 1. Daily Arctic sea ice extent on September 12 was 5.10 million square kilometers (1.97 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

Overview of conditions

On September 12, 2009 sea ice extent dropped to 5.10 million square kilometers (1.97 million square miles). This appears to have been the lowest point of the year, as sea ice has now begun its annual cycle of growth in response to autumn cooling. The 2009 minimum is the third-lowest recorded since 1979, 580,000 square kilometers (220,000 square miles) above 2008 and 970,000 square kilometers (370,000 square miles) above the record low in 2007.

The 2009 minimum is 1.61 million square kilometers (620,000 square miles) below the 1979 to 2000 average minimum and 1.28 million square kilometers (490,000 square miles) below the thirty-year 1979 to 2008 average minimum.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of September 15, 2009. The solid light blue line indicates 2009; dark blue shows 2008, dashed green indicates 2007; light green shows 2005, and solid gray indicates average extent from 1979 to 2000. 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

Conditions in context

This year, the minimum extent did not fall as low as the minimums of the last two years, because temperatures through the summer were relatively cooler. The Chukchi and Beaufort seas were especially cool compared to 2007. Winds also tended to disperse the ice pack over a larger region.

While the ice extent this year is higher than the last two years, scientists do not consider this to be a recovery. Despite conditions less favorable to ice loss, the 2009 minimum extent is still 24% below the 1979-2000 average, and 20% below the thirty-year 1979-2008 average minimum. In addition, the Arctic is still dominated by younger, thinner ice, which is more vulnerable to seasonal melt. The long-term decline in summer extent is expected to continue in future years.

average monthly data from 1979-2009 for July Figure 3. This image compares differences in ice-covered areas between September 12, 2009, the date of this year’s minimum, and September 16, 2007, the record low minimum extent. Light gray shading indicates the region where ice occurred in both 2007 and 2009, while white and dark gray areas show ice cover unique to 2009 and to 2007, respectively. Sea Ice Index data. About the data. —Credit: National Snow and Ice Data Center
High-resolution image

Comparison of the 2009 and 2007 September minima

The spatial pattern of the 2009 minimum extent was different than that of 2007, partly because of differing wind patterns. Compared to this year, 2007 had substantially more ice loss in the central Arctic, north of the Chukchi and East Siberian Seas because winds pushed ice in these regions northward. However, this year the Arctic lost more ice in the Beaufort Sea than 2007 because of southwesterly winds pushing the ice edge toward the northeast. Overall, the pattern of ice loss is similar to 2008 (not shown), although it resulted from different atmospheric circulation patterns.

Once again this year, the Northern Sea Route through the Arctic Ocean along the coast of Siberia opened. Although some ice remained in certain regions, two German ships managed to navigate the passage with Russian icebreaker escorts. Russian vessels have traversed the passage many times over the years, but as ice extent drops there is more interest from other nations. As in 2008, the shallow Amundsen’s Northwest Passage briefly opened, but the deeper Parry’s Channel of the Northwest Passage did not. In 2007, both channels were open.

A word of caution on calling the minimum

Because of the variability of sea ice at this time of year, the National Snow and Ice Data Center determines the minimum using a five-day running mean value. We have now seen four days of gains in extent. It is still possible that ice extent could fall slightly, because of either further melting or a contraction in the area of the pack due to the motion of the ice.

For example, in 2005, the time series began to level out in early September, prompting speculation that we had reached the minimum. However, the sea ice contracted later in the season, again reducing sea ice extent and causing a further drop in the absolute minimum. When all the data for September are in, we will confirm the minimum ice extent for the season.

Final analysis pending

In the beginning of October, NSIDC will issue a formal press release with full analysis of the melt season, and graphics comparing this year to the long-term record. We will also announce the monthly average September sea ice extent, the measure scientists rely on for accurate analysis and comparison over the long term. We will continue to post analysis of sea ice conditions throughout the year, with frequency determined by sea ice conditions. The near-real-time daily image update will continue each day

Do you have questions about Arctic sea ice? Read NSIDC’s Frequently Asked Questions to find the answers.

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

Winds cause sea ice to spread in August


Sign up for the RSS logo Arctic Sea Ice News RSS feed for automatic notification of analysis updates. Updates are also available via Twitter.
Atmospheric circulation patterns in August helped spread out sea ice, slowing ice loss in most regions of the Arctic. NSIDC scientists expect to see the minimum ice extent for the year in the next few weeks. While this year’s minimum ice extent will probably not reach the record low of 2007, it remains well below normal: average ice extent for August 2009 was the third-lowest in the satellite record. Ice extent has now fallen below the 2005 minimum, previously the third-lowest extent in the satellite record.

map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent for August 2009 was 6.26 million square kilometers (2.42 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

Overview of conditions

Sea ice extent averaged over the month of August 2009 was 6.26 million square kilometers (2.42 million square miles). This is 900,000 square kilometers (350,000 square miles) above the record low for the month, which occurred in August 2007, 200,000 square kilometers (77,000 square miles) above August 2008, and just below the August 2005 value of 6.30 million square kilometers (2.43 million square miles). Arctic sea ice extent for August 2009 was 1.41 million square kilometers (540,000 square miles) below the 1979 to 2000 average.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of September 7, 2009. The solid light blue line indicates 2009; dark blue shows 2008, dashed green indicates 2007; light green shows 2005, and solid gray indicates average extent from 1979 to 2000. 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

Conditions in context

In the beginning of August, the rate of ice loss was fairly slow. In the middle of the month, the loss rate sped up, and then slowed again. On average, the decline rate was close to the 1978 to 2000 average for past Augusts. Ice extent declined by 55,000 square kilometers (21,000 square miles) per day during August, compared to 66,000 square kilometers (25,000 square miles) per day in August 2007 and 79,000 square kilometers (31,000 square miles) per day in August 2008. But because of the higher-than-average rate of ice loss in July, average ice extent for August 2009 was still far below the 1978 to 2000 average extent for the month.

On September 2, Arctic sea ice extent dropped below the minimum extent for 2005. This year is now the third-lowest ice extent in the satellite record, with one to two weeks left in the melt season.

The minimum ice extent for the year will probably occur in the next two weeks. NSIDC scientists are closely monitoring conditions and will report the minimum when it occurs.

average monthly data from 1979-2009 for July
Figure 3. Monthly August ice extent for 1979 to 2009 shows a decline of 8.7% per decade. —Credit: National Snow and Ice Data Center
High-resolution image

August 2009 compared to past years

Arctic sea ice extent for August 2009 was the third lowest August since 1978, continuing the downward trend observed over the last three decades. Only 2007 and 2008 had lower ice extent during August. The long-term trend indicates a decline of 8.7% per decade in August ice extent since 1979.

map of arctic showing sea level pressure and atmospheric circulation patterns
Figure 4. Regional ice loss rates in August of this year were similar to August 2007, but slower than August 2008. Year-to-year variations in the ice loss rates show the impact of wind and temperature patterns on regional ice loss.—Credit: National Snow and Ice Data Center
High-resolution image

High ice loss in the Beaufort Sea and Siberian Arctic

This August, the Beaufort Sea lost more ice than in either 2007 or 2008. In other regions of the Arctic, ice loss rates were about the same as in August 2007, except in the central Arctic, where more ice was lost in 2007. These year-to-year differences in regional ice loss rates reflect variations in surface wind and temperature patterns that affect the ice motion and melt.

Overall, ice loss rates this year were slower than than in August 2008, when ice declined at record rates. But because the July 2008 rate of decline was slower, the minimum ice extent in September 2008 did not reach the 2007 record low.

MODIS map and cloudsat fields showing clear skies over the Arctic this summer
Figure 5. The map of sea level pressure (in millibars) for August 2009 shows a low pressure system over the Beaufort and Chuckchi seas, and high pressure over Greenland, which led to faster ice loss in the Beaufort Sea and a slower decline in the Kara and Laptev seas and the central Arctic.—Credits: From National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Division
High-resolution image

 

Winds spread ice, enhance melt

The pattern of high pressure over the Beaufort Sea that had characterized much of the summer broke down in early August. The August atmospheric pattern was dominated by low pressure over the Beaufort and Chukchi seas, and high pressure over Greenland and the Atlantic side of the Arctic. This pattern led to winds blowing from the south and southwest into the Beaufort Sea, contributing to melt and poleward ice motion in this area. By contrast, winds from the north favored a drift of ice towards the Siberian coast.

Studies by Mark Serreze, Masayo Ogi, and other researchers have shown that low-pressure patterns promote spreading of the ice pack, a process known as divergence. While ice divergence increases extent, it can also accelerate melt because there are more dark, open-water areas between the floes to absorb the sun’s energy, promoting melt on all sides of the floes.

MODIS satellite image of Northwest passage
Figure 6. Images from the Moderate Resolution Imaging Spectroradiometer (MODIS) image, acquired by the NASA Terra satellite on August 27 and September 4, show recent ice conditions in the Northwest Passage and Northern Sea Route. Open water and patches of ice are visible through the thin cloud cover.—Credit: From National Snow and Ice Data Center courtesy. Jesse Allen, NASA Earth Observatory (left), and NASA MODIS Rapid Response (right)
High-resolution image

Sea routes in the Arctic

The Northwest Passage is not a single passage, but rather a number of possible routes through the channels of the Canadian Arctic Archipelago. Satellite images show that the shallow and narrow southern route, which Amundsen navigated in 1905, appeared to open briefly this August. This route was also open in 2007 and 2008. The deeper northern route, of great interest for potential commercial transport, was open in 2007 but is still blocked by ice this year.

On the other side of the Arctic, the Northern Sea Route is open along most of the route, except for a narrow band of ice between the islands of Severnaya Zemlya and the Siberian mainland. Ice tends to persist in this area because of winds that push ice into the constrained region. Even during the record low extent year of 2007, the area around Severnaya Zemlya remained clogged with ice.

Evidence based on satellite data should not be taken as proof of safe conditions for shipping—hazardous areas of ice may remain.

Further reading

Three papers published in the past month have added important insight to our understanding of Arctic warming and sea ice decline. Elizabeth Hunke and Cecilia Bitz show that improved models can now reproduce the changes in sea ice extent and sea ice age that have occurred in the last 30 years. Ron Kwok and Drew Rothrock combine satellite data and submarine measurements to show an astonishing decline in sea ice thickness over the last 50 years. And Darrell Kaufman and colleagues show that recent warming has reversed a 2,000-year cooling trend in the Arctic, and that this cooling was what would be expected from slow changes in Earth’s orbit. The recent changes cannot be explained by these natural factors.

Hunke, E. C., and C. M. Bitz. 2009. Age characteristics in a multidecadal Arctic sea ice simulation. J. Geophys. Res., Vol. 114, No. C8, C08013 doi:10.1029/2008JC005186 22,

Kwok, R., and D. A. Rothrock. 2009. Decline in Arctic sea ice thickness from submarine and ICESat records: 1958-2008. Geophys. Res. Lett., Vol. 36, No. 15, L15501 doi:10.1029/2009GL039035.

Kaufman, D. S., D. P. Schneider, N. P. McKay, et al. 2009. Recent warming reverses long-term Arctic cooling. Science, p. 1236-1239. doi:10.1126/science.1173983.

References

Ogi, M., and J. Wallace. 2007. Summer minimum Arctic sea ice extent and the associated summer atmospheric circulation. Geophys. Res. Lett., 34, L12705, doi:10.1029/2007GL029897.

Serreze, M. C., R. G. Barry, and A. S. McLaren. 1989. Seasonal variations in sea ice motion and effects on sea ice concentration in the Canada Basin. Journal of Geophysical Research, 94(C8), 10955-10970. doi:10.1007/BF01030491.

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

A change in ice motion slows seasonal decline


Sign up for the RSS logo Arctic Sea Ice News RSS feed for automatic notification of analysis updates. Updates are also available via Twitter.

During the first half of August, Arctic ice extent declined more slowly than during the same period in 2007 and 2008. The slower decline is primarily due to a recent atmospheric circulation pattern, which transported ice toward the Siberian coast and discouraged export of ice out of the Arctic Ocean. It is now unlikely that 2009 will see a record low extent, but the minimum summer ice extent will still be much lower than the 1979 to 2000 average.

Note: This mid-monthly analysis update shows a single-day extent value for Figure 1, rather than the usual monthly average. While monthly average extent images are more accurate in understanding long-term changes, the daily images are helpful in monitoring sea ice conditions in near-real time.

map from space showing sea ice extent, continentsFigure 1. Daily Arctic sea ice extent on August 17 was 6.26 million square kilometers (2.42 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

Overview of conditions

On August 17, Arctic sea ice extent was 6.26 million square kilometers (2.42 million square miles). This is 960,000 square kilometers (370,000 square miles) more ice than for the same day in 2007, and 1.37 million square kilometers (530,000 square miles) below the 1979 to 2000 average. On August 8, the 2009 extent decreased below the 1979 to 2000 average minimum annual extent, with a month of melt still remaining.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of August 17, 2009. The solid light blue line indicates 2009; the solid dark blue line shows 2008; the dashed green line shows 2007; and the solid gray line indicates average extent from 1979 to 2000. 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

Conditions in context

From August 1 to 17, Arctic sea ice extent declined at an average rate of 54,000 square kilometers (21,000 square miles) per day. This decline was slower than the same period in 2008, when it was 91,000 square kilometers (35,000 square miles) per day, and for the same period in 2007, when ice extent declined at a rate of 84,000 square kilometers (32,000 square miles) per day. The recent rate of ice loss has slowed considerably compared to most of July. Arctic sea ice extent is now greater than the same day in 2008.

average monthly data from 1979-2009 for July Figure 3. Sea ice motion, derived from AMSR-E data and averaged for June, July, and the first week of August 2009 (the most recent data available), shows a recent change, with ice motion towards the eastern Siberian coast and little export of ice out of the Arctic Ocean via Fram Strait. —Credit: National Snow and Ice Data Center
High-resolution image

Ice motion changes in August

A recent atmospheric circulation pattern, which led to a change in ice motion, caused the ice loss rate to slow down significantly in the first two weeks of August. As discussed in the August 4 post, during much of June and July, a strong Beaufort Sea high-pressure pattern promoted winds that helped push ice out of the Siberian coastal seas, and also brought clear skies and warm temperatures that helped induce melt.

Toward the end of July, the atmospheric pattern changed. Averaged over the past two weeks, a high-pressure system has been centered over the Barents Sea, with low pressure centered over the Laptev Sea. In accordance with Buys Ballot’s Law, this pattern led to winds that redirected the motion of the ice cover, pushing the ice edge outward toward the Siberian coast and discouraging ice from exiting the Arctic Ocean through Fram Strait.

map of arctic showing sea level pressure and atmospheric circulation patterns Figure 4. The map of sea ice concentration from AMSR-E from August 16, 2009 shows ice clogging many of the channels of the Canadian Archipelago. The Northern Sea Route may be clear in the next few weeks. NASA AMSR-E data.—Credit: From National Snow and Ice Data Center, courtesy IUP, University of Bremen, Germany
High-resolution image


The Northwest Passage and Northern Sea Route

So far this year, neither the Northwest Passage nor the Northern Sea Route has opened. The Northern Sea Route appears likely to open soon, but ice still clogs many of the channels in the Northwest Passage.

Whether or not the navigational passages through the Arctic Ocean will open in a given summer depends on atmospheric circulation and ice thickness. For example, although 2007 was a record low extent in the Arctic and the Northwest Passage was nearly completely open, the Northern Sea Route was still choked with ice because of a circulation pattern that pushed a tongue of ice against the Siberian coast. Recent research by Stephen Howell at the University of Waterloo in Canada shows that whether the Northwest Passage clears depends less on how much melt occurs, and more on whether multi-year sea ice is pushed into the channels. Counterintuitively, as the ice cover thins, ice may flow more easily into the channels, preventing the Northwest Passage from regularly opening in coming decades.

ice thickness from submarinesFigure 4. The map of sea level pressure (in millibars) from June and July, 2009 shows a strong high-pressure cell over the Beaufort Sea, similar to the pattern in 2007. In the past, such patterns were rare. —Credit: From National Snow and Ice Data Center, courtesy NOAA/ESRL Physical Sciences Division
High-resolution image

Comment on atmospheric circulation patterns

James Overland of the NOAA Pacific Marine Environmental Laboratory in Seattle, Washington has taken a close look at patterns of atmospheric circulation in recent summers. Overland notes that the periods June through August 2007 and June and July 2009 both saw an unusual atmospheric pattern of sea level pressure, with higher pressure on the Alaskan side of the Arctic and lower pressure on the Eurasian side. This pressure difference brought warm air into the central Arctic and transported sea ice towards the Atlantic. Historically, such a pattern is a rare event—before 2007, it only occurred twice in 30 years. Normally there is little difference in pressure across the Arctic during summer, and winds are slack.

This rare condition may result from the convergence of the three main patterns of climate variability: the Arctic Oscillation (AO) climate pattern, which features either high or low pressure over most of the Arctic; the positive phase of the Pacific North American (PNA) pattern, which is characterized by low pressure over the Bering Sea and high pressure over the Canadian Rockies; and the Arctic dipole pattern, which features high pressure on one side of the Arctic and low pressure on the other. In 2007 and 2009 all three patterns have been in play. A clue to the cause of these unusual conditions comes from the wind flow in the middle atmosphere. Normally winds flow in a counter-clockwise direction around the central Arctic Ocean, a flow known as the polar vortex. In the summers of 2007 and 2009 the polar vortex shifted to mostly to the Eurasian side of the Arctic, allowing higher pressures to develop on the Alaskan side. Scientists are now studying whether this dipole pattern will become more common in the future and whether the loss of summer sea ice itself is helping to make this pattern more frequent.

ReferencesHowell, S. E. L., C. R. Duguay, and T. Markus. 2009. Sea ice conditions and melt season duration variability within the Canadian Arctic Archipelago: 1979–2008, Geophys. Res. Lett., 36, L10502, doi:10.1029/2009GL037681.

Overland, J. E., and M. Wang. 2005. The third Arctic climate pattern: 1930s and early 2000s. Geophys. Res. Lett., 32(23), L23808, doi:10.1029/2005GL024254.

Wang, M., N. A. Bond, and J. E. Overland. 2007. Comparison of atmospheric forcing in four sub-arctic seas. Deep-Sea Research II. 54, 2543-2559. doi:10.1016/j.dsr2.2007.08.014

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

Arctic ice melts quickly through July


Sign up for the RSS logo Arctic Sea Ice News RSS feed for automatic notification of analysis updates. Updates are also available via Twitter.
Arctic sea ice extent for the month of July was the third lowest for that month in the satellite record, after 2007 and 2006. The average rate of melt in July 2009 was nearly identical to that of July 2007. A strong high-pressure system, similar to the atmospheric pattern that dominated the summer of 2007, brought warm winds and clear skies to the western Arctic, promoting ice melt.

map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent for July 2009 was 8.81 million square kilometers (3.40 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

Overview of conditions

Sea ice extent averaged over the month of July 2009 was 8.81 million square kilometers (3.40 million square miles). This was 680,000 square kilometers (263,000 square miles) above the record low that occurred in July 2007, 250,000 square kilometers (97,000 square miles) below July 2008, and 1.29 million square kilometers (498,000 square miles) below the 1979 to 2000 average.  Sea ice extent is unusually low in the Kara Sea, Baffin Bay, and along the Russian coast. The only area with significant above-average ice extent is southern Hudson Bay.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of August 2, 2009. The solid blue line indicates 2009; the dashed green line shows 2007; and the solid gray line indicates average extent from 1979 to 2000. 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

Conditions in context

The average pace of ice loss during July 2009 was nearly identical to that of July 2007. Ice loss sped up during the third week of July, and slowed again during the last few days of the month.

Averaged for the month, July 2009 saw a decline rate in ice extent of 106,000 square kilometers (41,000 square miles) per day. For comparison, the rate of decline for July 2007 was 107,000 square kilometers (41,000 square miles) per day and the July 2008 rate of decline was 94,000 square kilometers (36,000 square miles) per day. The Arctic Ocean lost a total of 3.19 million square kilometers (1.23 million square miles) of ice during July 2009, and dropped below ice extent at this time in 2008.

average monthly data from 1979-2009 for July
Figure 3. Monthly July ice extent for 1979 to 2009 shows a decline of 6.1% per decade. —Credit: National Snow and Ice Data Center
High-resolution image

July 2009 compared to past years

Ice extent averaged for July 2009 was the third lowest in the satellite record for the month of July. The long-term trend indicates a decline of 6.1% per decade in July ice extent since 1979, relative to the 1979 to 2000 average, an average of 62,000 square kilometers (24,000 square miles) of ice per year.

map of arctic showing sea level pressure and atmospheric circulation patterns
Figure 4. The map of sea level pressure (in millibars) from July 1 to 31, 2009 shows a strong high-pressure cell over the Beaufort Sea. In 2007, a similar high-pressure cell, combined with unusually low pressure over eastern Siberia, contributed to the record melt.—Credit: From National Snow and Ice Data Center, courtesy NOAA/ESRL Physical Sciences Division
High-resolution image

Weather patterns bring clear skies, warmth

The atmospheric circulation pattern for summer 2009 has been similar to the pattern in summer 2007. As in 2007, an unusually strong high-pressure cell (an anticyclone) settled over the Beaufort Sea, bringing warm air into the Chukchi Sea. This year, the Beaufort Sea anticyclone, averaged for June and July 2009, was even stronger than the anticyclone in 2007. However, unlike 2007, this year the Beaufort Sea high-pressure cell is not paired with unusually low pressure over eastern Siberia, the “dipole” pattern that in 2007 promoted strong surface winds and extreme melt.

The strong Beaufort Sea high-pressure cell that occurred both this summer and in 2007 is part of a larger scale atmospheric pattern known as the Pacific North American (PNA) “teleconnection.” The airflow in the western hemisphere is usually characterized by a low pressure trough over the North Pacific, a ridge over western North America, and a trough over eastern North America. The PNA describes the strength of this pattern. When the PNA is positive, the normal pattern is amplified and the airflow becomes more “wavy” than usual. While the expressions of the PNA vary by season, the strong western North American ridge during the positive PNA favors a strong Beaufort Sea high pressure system. The stronger than usual trough over eastern North America also helps to explain the cool and rainy weather that has gripped this area much of the summer.

MODIS map and cloudsat fields showing clear skies over the Arctic this summer
Figure 5. The Moderate Resolution Imaging Spectroradiometer (MODIS) image (top), acquired by the NASA Terra satellite on on July 26, 2009, shows unusually clear skies over much of the Arctic, in particular over the Beaufort Sea. Dark gray areas over the sea ice correspond to areas of high surface melt. Maps derived from CloudSat satellite data (bottom) compare total cloud fraction averaged for May 20 to July 20, in 2007, 2008 and 2009.—Credits: From National Snow and Ice Data Center courtesy A. NASA MODIS Rapid Response Arctic Mosaic and B. CloudSat Image courtesy Jennifer Kay, NCAR
High-resolution image

Clear skies favor melt in the Beaufort Sea

In 2007, unusually sunny skies throughout the summer melt season were one of the factors that helped lead to the record low ice extent. The clear skies allowed more of the sun’s energy to reach the surface, melting the ice and warming the ocean. This year, cloud fields provided by Jennifer Kay at the National Center for Atmospheric Research show fewer clouds over the Beaufort Sea than in 2007, leading to strong melt in that region. However, over the Chukchi and East Siberian Seas, the Arctic sky has been cloudier than 2007.

ReferencesKay, J. E., and A. Gettelman. 2009. Cloud influence on and response to seasonal Arctic sea ice loss. Journal of Geophysical Research, In press, doi:10.1029/2009JD011773.

L’Heureux, M. L., A. Kumar, G. Bell, M. Halpert, and R. Higgins. 2008. Role of the Pacific-North American (PNA) pattern in the 2007 Arctic sea ice decline. Geophys. Res. Lett., 45, L20701, doi:10.1029/2008GL035205.

Wang, J., J. Zhang, E. Watanabe, M. Ikeda, K. Mizobatu, J. E. Walsh, X. Bai, and B. Wu. 2009. Is the dipole anomaly a major driver to record lows in Arctic summer sea ice extent?  Geophys. Res. Lett., 36, L05706, doi:10.1029/2008GL036706.

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

Arctic sea ice extent tracking below 2008


Sign up for the RSS logo Arctic Sea Ice News RSS feed for automatic notification of analysis updates. Updates are also available via Twitter.

During the first half of July, Arctic sea ice extent declined more quickly than in 2008, but not as fast as in 2007. As in recent years, melt onset was earlier than the 1979 to 2000 average. International sea ice researchers expect another low September minimum ice extent, but they do not yet know if it will fall below the 2007 record.

Note: This mid-monthly analysis update shows a single-day extent value for Figure 1, rather than the usual monthly average. While monthly average extent images are more accurate in understanding long-term changes, the daily images are helpful in monitoring sea ice conditions in near-real time.

map from space showing sea ice extent, continentsFigure 1. Daily Arctic sea ice extent on July 21 was 8.28 million square kilometers (3.20 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

Overview of conditions

On July 21, Arctic sea ice extent was 8.28 million square kilometers (3.20 million square miles). This is 617,000 square kilometers (238,000 square miles) more ice than for the same day in 2007 and 1.36 million square kilometers (523,000 square miles) below the 1979 to 2000 average. Ice extent on July 21, 2009 remained 8.06% higher than the same day in 2007, yet was 2.44% below the same day in 2008 and 14.06% below the 1979-2000 average for that day.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of July 21, 2009. The solid blue line indicates 2009; the dashed green line shows 2007; the purple line shows 2008; and the solid gray line indicates average extent from 1979 to 2000. Sea Ice Index data.—Credit: National Snow and Ice Data Center
High-resolution image

Conditions in context

During the first two weeks of July (July 1 to 16), Arctic sea ice extent declined at an average rate of 97,000 square kilometers (37,000 square miles) per day. This decline was faster than in 2008, when it was 87,000 square kilometers (34,000 square miles) per day, but slower than in 2007, when ice extent declined at a rate of 111,000 square kilometers (43,000 square miles) per day .

map showing melt onset date in Arctic for 2007, 2008, 2009, and 1979-2000 average
Figure 3. In recent years, sea ice melt in the Arctic Ocean has begun earlier than in the past. Colors in the map above indicate the date of melt onset; gray regions indicate areas where data is not available or not retrievable. Variations in ice type may result in some errors. Data are from the Defense Meteorological Satellite Program (DMSP) F-series satellite SSM/I and SSMIS sensors. —Credit: National Snow and Ice Data Center: Algorithm provided by Thorsten Markus, Goddard Space Flight Center
High-resolution image

Early melt onset

Early or extended melt in response to rising atmospheric temperatures appears to be one of the factors contributing to the sharp decline of summer Arctic sea ice extent. When ice melts earlier, it leads to a lower albedo surface that absorbs more of the sun’s energy and promotes further melt.

The same satellite instruments that are used to measure ice extent also provide information on when ice begins to melt each year. In recent years, Arctic sea ice melt onset has begun earlier than in the past, and 2009 continues this pattern. Compared to average conditions over the period 1979 to 2000, melt this year started a week early in the Beaufort, Chukchi and Kara seas. In some regions such as the East Greenland and the Barents seas, melt began more than two weeks earlier than usual.

chart of sea ice minimum projections from Sea Ice Outlook
Figure 4. Scientists who contributed to the July Sea Ice Outlook report expect another low Arctic sea ice extent in September. Most of their projections fall near or between the 2007 record low and the second-lowest extent, which occurred in 2008.—Credit: From National Snow and Ice Data Center, courtesy SEARCH Sea Ice Outlook.
High-resolution image

Outlook for September

As interest in Arctic sea ice builds, national and international scientific organizations are working together to make projections of the September 2009 sea ice minimum. Their assessments are summarized in the Study of Environmental Arctic Change Sea Ice Outlook.

The researchers make projections using a variety of techniques, ranging from sophisticated sea ice models to simpler statistical analyses. Their most recent report points to another extreme September sea ice minimum in 2009, with projections for the September monthly average ranging from 4.0 to 5.2 million square kilometers (1.5 to 2.0 million square miles). However, sea ice forecasting efforts are still in their infancy, and the resulting projections should not be taken as a true forecast, but rather as a way to gain insights into the changing Arctic climate. Whether or not 2009 will break the 2007 record still depends largely on atmospheric conditions during the rest of the summer.

ReferencesPerovich, D. K., J. A. Richter-Menge, K. F. Jones, and B. Light (2008), Sunlight, water, and ice: Extreme Arctic sea ice melt during the summer of 2007, Geophys. Res. Lett., 35, L11501, doi:10.1029/2008GL034007.

Smith, D. M., Observation of perennial Arctic sea ice melt and freeze-up using passive microwave data. J. Geophys. Res., 103, 27,753-27,769, 1998.

Stroeve, J. C., T. Markus and W. N. Meier (2006), Recent changes in the Arctic melt season, Annals of Glaciology, 44, 367-374

For previous analysis, please see the drop-down menu under Archives in the right navigation at the top of this page.

Melt season in high gear

The Arctic is now in the midst of the summer melt season. Through most of June, ice extent tracked below the 1979 to 2000 average, and slightly above the levels recorded during June 2007. Warm temperatures and southerly winds led to quickly declining ice concentration in some regions, such as the Laptev Sea.
map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent for June 2009 was 11.48 million square kilometers (4.43 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


Overview of conditions

Sea ice extent averaged over the month of June 2009 was 11.48 million square kilometers (4.43 million square miles). This was 420,000 square kilometers (162,000 square miles) above the record low for that month, which occurred in June 2006, and 700,000 square kilometers (270,000 square miles) below the 1979 to 2000 average.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of July 6, 2009. The solid blue line indicates 2009; the dashed green line shows 2007; and the solid gray line indicates average extent from 1979 to 2000. 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

Conditions in context

Through most of June, ice extent tracked close to two standard deviations below the long-term mean and just above the levels observed in 2007. By the end of June 2009, ice extent was 337,000 square kilometers (130,000 square miles) higher than extent at the end of June 2007.

During June, the Arctic Ocean lost a total of 2.05 million square kilometers (792,000 square miles) of ice, an average decline of 68,300 square kilometers (26,400 square miles) per day.

monthly extent plot
Figure 3. Monthly June ice extent for 1979 to 2009 shows a decline of 3.3% per decade. —Credit: National Snow and Ice Data Center
High-resolution image

June 2009 compared to past Junes

Compared to previous Junes, ice extent in June 2009 was extremely close to the last two years, falling within 30,000 square kilometers (12,000 square miles) of the June extent in 2007 and 2008. The long-term trend indicates a decline of 3.3% per decade, an average of 40,100 square kilometers (15,500 square miles) of ice per year.

map of sea ice concentration, July 5, 2009
Figure 4. The map of sea ice concentration from AMSR-E from July 5, 2009 shows low ice concentrations in the Laptev Sea, where atmospheric temperatures have been particularly warm in the month of June. NASA AMSR-E data.—Credit: From National Snow and Ice Data Center courtesy IUP, University of Bremen, Germany
High-resolution image

Warm conditions speed regional melt

In June, the Arctic saw warm temperatures over the Laptev Sea and the northern Beaufort Sea, while the Atlantic sector of the Arctic was slightly cooler than normal. The warm temperatures in the Laptev Sea corresponded to quickly declining ice concentrations in the area. The decline can be seen in sea ice concentration analyses produced at the University of Bremen using NASA Advanced Microwave Sounding Radiometer-Earth Observing System (AMSR-E) data. We expect this region to become largely ice-free in the next few weeks.

July Fig 5
Figure 5. The map of sea level pressure (in millibars) from June 1 to 30, 2009 shows high pressure (red) over the northern Beaufort Sea and a weak low (purple) centered over Novaya Zemlya. —Credit: From National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Division
High-resolution image

Southerly winds promote warmth

The warmth in the Laptev Sea is consistent with a pattern of southerly winds in these areas, which can be linked to the area of low atmospheric pressure centered just north of Novaya Zemlya Island. Note also the strong high-pressure cell (an anticyclone) over the northern Beaufort Sea.

This contrast between high and low pressure is broadly similar to the atmospheric circulation pattern that set up in 2007. In 2007, that pattern contributed to a significantly accelerated decline in ice extent during July, and a record minimum low in September. Will the same acceleration in ice melt occur this year? If so, a new record low minimum extent becomes more likely. So far, an acceleration has not been observed. As July progresses, the Arctic sun gets lower on the horizon, incoming solar energy decreases, and the chances of such a rapid decline become less likely.

For previous analysis, please see the drop-down menu under Archives in the right navigation at the top of this page.

Melt season gains momentum

Sign up for the RSS logo Arctic Sea Ice News RSS feed for automatic notification of analysis updates. Updates are also available via Twitter.After a slow start to the melt season, ice extent declined quickly in May. Scientists are monitoring the ice pack for signs of what will come this summer. The thinness of the ice pack makes it likely that the minimum ice extent will again fall below normal, but how far below normal will depend on atmospheric conditions through the summer.

map from space showing sea ice extent, continents
Figure 1. Arctic sea ice extent for May 2009, was 13.39 million square kilometers (5.17 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

Overview of conditions

Sea ice extent averaged over the month of May 2009 was 13.39 million square kilometers (5.17 million square miles). This was 81,000 square kilometers (31,000 square miles) above the record low for that month, which occurred in May 2004, and 21,000 square kilometers (8,100 square miles) below the 1979 to 2000 average.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of June 2, 2009. The solid blue line indicates 2009; the dashed green line shows 2007;and the solid gray line indicates average extent from 1979 to 2000. The gray area around 1979-2000 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

Conditions in context

Although the 2009 melt season started slowly, the pace of ice loss quickened through May. During May, the Arctic Ocean lost 1.67 million square kilometers (645,000 square miles) of ice, an average decline of 54,000 square kilometers (21,000 square miles) per day. This is similar to the rate of decline observed last year. For comparison, the long-term average (1979-2000) rate of decline for May is 47,000 kilometers per day (18,000 square miles per day). By the end of May 2009, ice extent was 84,000 square kilometers (32,000 square miles) higher than extent at the end of May 2007.

monthly extent plot
Figure 3. Monthly May ice extent for 1979 to 2009 shows a decline of 2.5% per decade. —Credit: National Snow and Ice Data Center
High-resolution image

May 2009 compared to past Mays

Compared to previous Mays, ice extent in May 2009 is about average. Over the last four years, May ice extent has increased. The long-term trend nevertheless indicates a decline of 2.5% per decade, an average of 34,000 square kilometers (13,000 square miles) of ice per year.

map with air temp anomalies in colors
Figure 4. The map of air temperature anomalies for May, 2009, at the 925 millibar level (roughly 1,000 meters [3,000 feet] above the surface), shows warmer than usual temperatures between Greenland and Svalbard and in the East Siberian and Laptev seas. Yellow areas correspond to strong positive (warm) anomalies. Areas in blue and purple correspond to negative (cool) anomalies.—Credit: National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Laboratory
High-resolution image

Winds and temperature

The Arctic saw warmer than usual temperatures between Greenland and Svalbard and in the East Siberian and Laptev seas. This is consistent with the atmospheric circulation pattern for May. Two high pressure cells, one centered over the Barents and Laptev seas and the other extending along the northern coast of Alaska into northwestern Canada, produced southerly wind patterns that promote high temperatures. The area around the Canadian Arctic Islands was cooler than normal.

MODIS image of Arctic ocean
Figure 5. This satellite image of the Arctic ocean was taken on May 25, 2009 by the MODIS sensor on the NASA Terra Satellite. It shows sea ice beginning to break up in the Barents
Sea and north of Novaya Zemlya. Open water areas have also begun to form at the northern end of Baffin Bay (formation of the North Water Polynya) and in the Beaufort Sea off the coast of Alaska and Canada.
—Credit: From National Snow and Ice Data Center courtesy NASA/GSFC MODIS Rapid Response
High-resolution image

Looking towards summer

Because the 2009 melt season started out with a thin ice pack, September ice extent will likely be below average yet again. The thinning ice pack, discussed in our April post, has played a major role in the strong decline of September ice extent. Thinner ice requires less energy to melt. It also tends to be fractured, with more areas of open water. Since water absorbs more solar energy than ice, heat from the sun warms up areas of open ocean and promotes even more melt.

September extent in a given year also depends on summertime patterns of atmospheric circulation. The record low ice extent in September, 2007 was caused by a combination of a thin spring ice cover and an unusual summer atmospheric circulation pattern. High pressure over the central Arctic Ocean and low pressure over Siberia blew warm air over the Arctic Ocean and compressed the ice pack into a smaller area. Whether or not Arctic sea ice reaches a new record low this summer will depend on the circulation patterns that set up over the next few months.

Sea Ice Outlook reportSea ice scientists around the world are actively monitoring the state of Arctic sea ice cover. The Study of Environmental Arctic Change will issue their first Sea Ice Outlook report later this month.

For previous analysis, please see the drop-down menu under Archives in the right navigation at the top of this page.

Satellite update: daily images now available

NSIDC has transitioned from the Defense Meteorological Satellite Program (DMSP) F13 satellite, to the DMSP F17 satellite. Switching to the new satellite will allow us to continue our consistent long-term record of sea ice extent.

map from space showing sea ice extent, continentsFigure 1. NSIDC now has more than a year of data from the Special Sensor Microwave Imager/Sounder (SSMIS) sensor on the DMSP F17 satellite, which has been intercalibrated with data from the F13 satellite. Note the close correspondence between the two data records. The average absolute daily difference was approximately 28,000 square kilometers (11,000 square miles). Sea Ice Index data. About the data. —Credit: National Snow and Ice Data Center
High-resolution image

Continuing a long-term data series

The DMSP F13 satellite that has been central to our Arctic sea ice analysis for the past several years is nearing the end of its mission and is no longer a reliable resource for our sea ice products. As is standard data practice, we have transitioned to a newer sensor.

NSIDC now has more than a year of data from F17, obtained from the NOAA Comprehensive Large Array-data Stewardship System (CLASS). While the sensors on the two satellites are slightly different, they use the same microwave frequencies to collect sea ice data; by comparing a year of F17 data with a year of F13 data, we have been able to calibrate F17 to ensure its measurements are consistent with the prior F13 record. F13, in turn, had been similarly calibrated with prior generations of sensors, resulting in a consistent, long-term record of sea ice extent since 1979. The average absolute daily difference between data from F13 and F17 was approximately 28,000 square kilometers (11,000 square miles).

For more information on the satellite sensors that NSIDC uses for sea ice data, see our February 26 update. For detailed information on the near-real-time sea ice data, please read the data set documentation.

For previous analysis, please see the drop-down menu under Archives in the right navigation at the top of this page.

A slow start to the spring melt season

Arctic sea ice extent declined quite slowly in April; as a result, total ice extent is now close to the mean extent for the reference period (1979 to 2000). The thin spring ice cover nevertheless remains vulnerable to summer melt.

map from space showing sea ice extent, continents Figure 1. Arctic sea ice extent for April, 2009, was 14.58 million square kilometers (5.63 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

Overview of conditions

Sea ice extent averaged over the month of April 2009 was 14.58 million square kilometers (5.63 million square miles). This was 710,000 square kilometers (274,000 square miles) above the record low for April in 2007, and 420,000 square kilometers (162,000 square miles) below the 1979 to 2000 average.

graph with months on x axis and extent on y axis Figure 2. The graph above shows daily sea ice extent as of May 3, 2009. The solid blue line indicates 2009; the dashed green line shows 2007;and the solid gray line indicates average extent from 1979 to 2000. The gray area around 1979-2000 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

Conditions in context

The decline rate for the month of April was the third slowest on record. The Arctic lost sea ice cover at a rate of 27,300 square kilometers per day (10,500 square miles), compared to an average of 41,600 square kilometers (16,000 square miles) per day for 1979 to 2000. Ice extent was well above normal in the Bering Sea, but below normal in the Barents Sea and the Sea of Okhotsk.

For the past few years, Arctic sea ice extent for most months has been more than two standard deviations below the 1979 to 2000 mean, particularly in summer. Two standard deviations provide an estimate of the expected range of natural variability. Because of cooler than average temperatures, Arctic sea ice extent at the end of April 2009 was within the expected range of natural variability.

map with air temp anomalies in colors Figure 3. Monthly April ice extent for 1979 to 2009 shows a decline of 2.8% per decade. —Credit: National Snow and Ice Data Center
High-resolution image

April 2009 compared to past Aprils

Compared to previous Aprils, April 2009 is near the middle of the distribution (10th lowest of 31 years). The linear trend indicates that for the month of April, ice extent is declining by 2.8% per decade, an average of 42,400 square kilometers (16,400 square miles) of ice per year.

map with air temp anomalies in colors Figure 4. The map of air temperature anomalies for April 1 to 15, 2009, at the 925 millibar level (roughly 1,000 meters [3,000 feet] above the surface), shows cooler-than-usual conditions over much of the Arctic Ocean. Areas in blue correspond to negative (cool) anomalies. Areas in orange and red correspond to strong positive (warm) anomalies.—Credit: National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Laboratory
High-resolution image

Causes of the slow April decline

Cool conditions over the Bering Sea, noted in the April 2009 update, persisted through mid-April. Cool weather also slowed ice loss in the Barents Sea. The cool temperatures resulted from the movement of cold air from eastern Siberia across the central Arctic. After mid-April, the pattern shifted to relatively warmer conditions in the Bering Sea and melt progressed, resulting in the faster decline in the total extent during the second half of the month.

It is difficult to assess how the slow decline through April will affect the summer minimum ice extent. Persistence of cool conditions through the summer could lead to a greater September ice extent compared to that of recent years. However, as discussed in our last post, the spring ice cover is thin and hence quite vulnerable to summer melt. However this summer unfolds, scientists expect to see high year-to-year variability in ice extent embedded within the long-term decline.

map showing areas of above and below-average precipitation following low sea ice years Figure 5. This map shows regions of above- and below-average precipitation observed in winter, following summers with very low Arctic sea ice extent.—Credit: From the National Snow and Ice Data Center, courtesy J. Francis, Rutgers University
High-resolution image

Can summer ice extent affect winter weather?

A new study suggests that Arctic ice extent at the end of summer can affect precipitation at lower latitudes the following winter. Jennifer Francis from Rutgers University and colleagues compared winter weather following summers with below-average ice extent, to weather following summers with above-average ice. The researchers found that low summer sea ice extent is linked to drier winters over much of the U.S., Scandinavia, and Alaska, and wetter winters in the northern Mediterranean, Japan, and the Pacific Northwest.

The study showed that extensive ice loss in summer warmed the Arctic atmosphere during autumn. This warmth weakened the storm track that encircles the northern hemisphere, affecting weather patterns far away from the Arctic. As sea ice continues to decline in summer, these influences will become more prominent.

References:

Francis, J. A., W. Chan, D. J. Leathers, J. R. Miller, and D. E. Veron. 2009. Winter Northern Hemisphere weather patterns remember summer Arctic sea-ice extent. Geophysical Research Letters, 36, L07503, doi:10.1029/2009GL037274.

For previous analysis, please see the drop-down menu under Archives in the right navigation at the top of this page.