The National Snow and Ice Data Center (NSIDC) reports the Arctic sea ice melt season got off to a slow start this year, but ice extent is now plummeting.

Arctic sea ice extent declined slowly through the first three weeks of April, compared to recent years. The slow decline through March and the first few weeks of April meant that by mid-April, ice extent was at near-average levels. However, much of the extensive ice cover is thin ice that will melt quickly once temperatures rise in the Arctic. Over the past week, extent has started to fall sharply.

NSIDC says the relatively high ice extent will have little influence on how much ice melts this summer, explaining that much of the ice cover is recently formed thin ice that will melt out quickly and that sea ice extent in spring does not tell us much about ice extent the following summer. More important to the summer melt is the thickness of the ice cover, and summer weather.

A new study published in Geophysical Research Letters concludes the only physically plausible link with the Arctic sea-ice retreat observed in recent years is the anthropogenic increase in greenhouse gas concentrations:

The most likely explanation for the linear trend during the satellite era from 1979 onwards is the almost linear increase in CO2 concentration during that period.

The Arctic sea ice melt season is off to an extremely slow start, with extent and area numbers approaching the long-term averages.

Will the trend lines soon start falling of a cliff? Well, the Polar Science Center at the University of Washington reports that ice volume is still at or near record lows for this time of the year. Ice volume for March 2012 was 20,800 km³, the same as last year but 35% lower than the maximum in 1979, 24% below the mean, and 1.7 standard deviations from the trend.

Most of the older, thicker ice has disappeared from the Arctic.

This March, first-year ice made up 75% of the Arctic sea ice cover. Thicker multi-year ice used to make up around a quarter of the Arctic sea ice cover. Now it constitutes only 2%. This thin, young ice is susceptible to melting. The areas in purple on the map above can be expected to disappear quickly once the melting season gets underway in earnest.

Melting sea ice is apparently initiating a previously unknown feedback effect. In a study published in Nature Geoscience, researchers report that significant amounts of methane are released from the ocean into the atmosphere through cracks in the melting sea ice.  Previously, large methane plumes have been observed emanating from the seabed in the relatively shallow sea off the northern coast of Siberia, but the latest findings come far away from land in the deep, open ocean where the surface has in the past been capped by ice. The researchers conclude:

We suggest that the surface waters of the Arctic Ocean represent a potentially important source of methane, which could prove sensitive to changes in sea ice cover. The association with sea ice makes this methane source likely to be sensitive to changing Arctic ice cover and dynamics, providing an unrecognised feedback process in the global atmosphere-climate system.

The researchers estimate open ocean emissions are comparable to emissions seen on the Siberian shelf.

Methane is about 70 times more potent as a greenhouse gas than carbon dioxide when it comes to trapping heat. Because methane is broken down rather quickly in the atmosphere, it is about 20 times more powerful averaged over a 100-year period.

A recent post noted that Arctic warming is already affecting Earth’s weather. The analysis revealed two major factors contributing to the unusual Norther Hemisphere weather events in recent winters: changes in atmospheric circulation and changes in atmospheric water vapor content. Both are linked to diminishing Arctic sea ice.

The study, titled “Impact of declining Arctic sea ice on winter snowfall”, is published in the online early edition of the journal Proceedings of the National Academy of Sciences.

A press release quotes co-author Judith Curry:

Our study demonstrates that the decrease in Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circulation. The circulation changes result in more frequent episodes of atmospheric blocking patterns, which lead to increased cold surges and snow over large parts of the northern continents.

The Georgia Tech study found that Arctic sea ice loss had in recent years caused a 20 – 60% weakening of the west-to-east belt of winds circling the pole, producing broader meanders in the jet stream that allows it to get “stuck” in place 20 – 60% more often. Co-author Jiping Liue explains:

We think the recent snowy winters could be caused by the retreating Arctic ice altering atmospheric circulation patterns by weakening westerly winds, increasing the amplitude of the jet stream and increasing the amount of moisture in the atmosphere. These pattern changes enhance blocking patterns that favor more frequent movement of cold air masses to middle and lower latitudes, leading to increased heavy snowfall in Europe and the Northeast and Midwest regions of the United States.

While the eastern parts of Canada and the U.S. experienced episodes of almost summer-like conditions this past winter, much of Europe and Asia has been blasted by unusually cold and snowy weather. The jet stream marks the boundary between cold, Arctic air to the north, and warmer subtropical air to the south, areas on both sides of the jet are subjected to extended periods of unusually warm or cold weather during a blocking episode. A blocking pattern early this year brought exceptionally cold and snowy conditions to much of Europe, which lay on the cold side of an elongated loop of the jet stream that got stuck in place. Conversely, most of North America and northern Siberia saw unusually warm temperatures during this period, since they were on the warm side of the jet stream. The cold air spilling out of the Arctic during this past winter was confined to Europe – unlike the previous two winters, which were unusually cold and snowy in the Eastern U.S.

This chart from Jeff Master’s Wunderblog shows what such a “blocking pattern” looked like in the U.S. this March, resulting in record warm temperatures in the midwest and on the east coast while the west coast was being hit with a rare late-season episode of cold and snow.

UPDATE: here’s yet another study linking Arctic amplification to extreme weather in mid-latitudes. The jet stream, the study says, is becoming “wavier,” with steeper troughs and higher ridges. Weather systems are progressing more slowly, raising the chances for long-duration extreme events, like droughts, floods, and heat waves. These effects are particularly evident in autumn and winter consistent with sea-ice loss. Key points:

• Enhanced Arctic warming reduces poleward temperature gradient
• Weaker gradient affects waves in upper-level flow in two observable ways
• Both effects slow weather patterns, favoring extreme weather

Jeff Masters at Wunderblog posts these satellite images showing the dramatic reduction in Arctic sea ice over the last three decades.

Arctic sea ice in September 2007 reached its lowest extent on record, approximately 40% lower than when satellite records began in 1979. Sea ice loss in 2011 was virtually tied with the ice loss in 2007, despite weather conditions that were not as unusual in the Arctic.

Masters points out the area of lost ice coverage is equal to about 44% of the contiguous U.S., or 71% of the non-Russian portion of Europe.

The National Snow and Ice Data Center says the Arctic sea ice melt season has finally begun:

On March 18, 2012, Arctic sea ice extent reached its annual maximum extent, marking the beginning of the melt season for Northern Hemisphere sea ice. This year’s maximum extent was the ninth lowest in the satellite record.

Sea ice appeared to have reached its maximum extent earlier in the month on March 6 – but an unexpected change in Arctic weather lead to a late-season surge.

The maximum this year was very late compared to recent years, occurring 12 days later than the 1979 to 2000 average date of March 6.

• March 6th 2005: 13.46
• March 11th 2006: 13.36
• February 26th 2007: 13.32
• March 11th 2008: 13.89
• March 2nd 2009: 13.85
• March 7th 2010: 13.81
• March 8th 2011: 13.14
• March 20th 2012: 13.70

This year’s maximum ice extent was 15.24 million square kilometers (5.88 million square miles), 614,000 square kilometers (237,000 square miles) below the 1979 to 2000 average of 15.86 million square kilometers (6.12 million square miles). This year’s maximum was the ninth lowest in the satellite record. Last year (2011) was the lowest maximum on record at 14.64 million square kilometers (5.65 million square miles). Including this year, the nine years from 2004 to 2012 are the nine lowest maximums in the satellite record.

Sea ice extent in February and March tends to be quite variable, because ice near the edge is thin and often quite dispersed. The thin ice is highly sensitive to weather, moving or melting quickly in response to changing winds and temperatures, and it often oscillates near the maximum extent for several days or weeks, as it has done this year. NSIDC’s call includes this caveat:

As of March 23, ice extent has declined for five days. However, there is still a chance that the ice extent could expand again.

Why should we care about what’s happening in the Arctic? Because the Arctic is the “canary in the coal mine”, warming faster than anyplace else on Earth.

The warming Arctic is already affecting Earth’s weather. The erratic weather and extreme weather events seen over last few years are merely a foretaste of what’s in store for the future. Jennifer A. Francis, a Rutgers University climate researcher, is quoted in the New York Times:

The question really is not whether the loss of the sea ice can be affecting the atmospheric circulation on a large scale. The question is, how can it not be, and what are the mechanisms?

Climate mechanisms in the Arctic are a major driver of weather in the northern hemisphere, including not only “über-extreme” weather events but also the weird and unpredictable weather affecting crops and livelihoods at home, like here in Oregon. What happens in the Arctic directly impacts us in our daily lives.

Ice extent usually reaches its annual maximum sometime in late February or March, but the exact date varies widely from year to year.

The National Snow and Ice Data Center (NSIDC) reports that sea ice extent in February (as in January) was low on the Atlantic side of the Arctic, but unusually high on the Pacific side of the Arctic, remaining lower than average overall. At the end of the month, ice extent rose sharply, as winds changed and started spreading out the ice cover.

The University of Washington’s Polar Science Center latest updated graph shows ice volume is now slightly lower than last year.

Neven at Arctic Sea Ice Blog reports that this year’s multi-year ice cover as of January 1 was just a bit higher than that of 2008, which was extremely low due to the preceding record melting season of 2007.

It’s unusually “not cold” in much of the Arctic . . .

. . .  with the notable exception of the Beaufort, Chukchi, and Bering Seas – which is consistent with the expanded ice extent on the Pacific side of the Arctic.

We will soon begin to see the 2012 melting season unfold, as it is about to start (if it hasn’t already). [Update 3/14: Neven at Arctic Sea Ice Blog has called the maximum as of March 6, 2012. The 2012 Arctic sea ice melt season is officially underway.]

One more thought: notice the anomalously warm temperatures around Greenland, especially on the eastern side. A new study by scientists from the Potsdam Institute for Climate Impact Research (PIK) and the Universidad Complutense de Madrid concludes the Greenland ice sheet is more vulnerable to global warming than previously thought. The best estimate of the temperature threshold for melting the ice sheet completely is 1.6 degrees above pre-industrial levels, with a range of 0.8 to 3.2 degrees Celsius. And 0.8 degrees global warming has already been observed.

Previous research estimated the threshold in global temperature increase for melting the Greenland ice sheet was 3.1 degrees, with a range of 1.9 to 5.1 degrees. The new study’s best estimate is about half that.

Team-leader Andrey Ganopolski of PIK explains that the Greenland ice sheet could hit a “tipping point” beyond which recovery would become impossible:

Our study shows that under certain conditions the melting of the Greenland ice sheet becomes irreversible. This supports the notion that the ice sheet is a tipping element in the Earth system. If the global temperature significantly overshoots the threshold for a long time, the ice will continue melting and not regrow – even if the climate would, after many thousand years, return to its preindustrial state.

The vulnerability of the Greenland ice sheet arises because of feedbacks between the climate and the ice sheet. The ice sheet is over 3000 meters thick and thus elevated into cooler altitudes. When it melts its surface comes down to lower altitudes with higher temperatures, which accelerates the melting. Also, the ice reflects a large part of solar radiation back into space. When the area covered by ice decreases, more radiation is absorbed and this adds to regional warming.

A business-as-usual scenario of greenhouse-gas emissions could lead to 8 degrees Celsius of global warming. This would result in one fifth of the ice sheet melting within 500 years and a complete loss in 2000 years. Alexander Robinson, lead-author of the study, notes:

[C]ompared to what has happened in our planet’s history, it is fast. And we might already be approaching the critical threshold.

Melting of the current Greenland ice sheet would result in a sea-level rise of about 6.5 meters.

The National Snow and Ice Data Center reports Arctic sea ice extent in January 2012 averaged 13.73 million square kilometers (5.30 million square miles) – the fourth-lowest January ice extent in the 1979 to 2012 satellite data record.

Before 2005 average January ice extent had never been lower than 14 million square kilometers (5.41 million square miles). January ice extent has now fallen below that mark six out of the last seven years.

Large areas of the Barents Sea and the adjoining Kara Sea that are normally locked in ice by now are still open. Sea ice concentration maps posted by Neven at Arctic Sea Ice Blog show how unusual 2012 is:

University of Bremen sea ice concentration maps, cropped

The University of Washington’s Polar Science Center reports Arctic sea ice volume for January 2012 was 16,200 km³ , slightly larger than last year (15,800 km³) but 41% lower than the satellite record era maximum in 1979, 28% below the mean and 1.4 standard deviations from the trend.

Total Arctic sea ice volume from PIOMAS.
Shaded areas indicate one and two standard deviations from the mean.

The melting season starts in about six weeks.

It’s not just sea ice that has been diminishing. In a new study, researchers using satellite measurements calculate that the world’s glaciers and ice caps lost about 148 billion tons, or about 39 cubic miles of ice annually from 2003 to 2010. This total does not count the mass from individual glacier and ice caps on the fringes of the Greenland and Antarctic ice sheets, which could add up to an additional 80 billion tons.  The researcher’s data shows total sea level rise from all land-based ice on Earth, including Greenland and Antarctica, was roughly 1.5 millimeters per year from 2003 to 2010, cumulatively about 12 millimeters. The sea rise amount includes the expansion of water due to warming. Thermal expansion of water is the second major contributor to sea level rise, roughly equal to melting ice.

The Greenland and Antarctic ice sheets are losing mass at an accelerating pace. A recent study sponsored by NASA concluded that, if current ice sheet melting rates continue for the next four decades, their cumulative loss could raise sea level by 15 centimeters (5.9 inches) by 2050. When this is added to the predicted sea level contribution of 8 centimeters (3.1 inches) from glacial ice caps and 9 centimeters (3.5 inches) from ocean thermal expansion, total sea level rise by 2050 could reach 32 centimeters (12.6 inches).

2011 has seen new record lows established for Arctic average sea ice extent and area; sea ice volume; and for global sea ice area.

Neven at Arctic Sea Ice Blog reports that the 12 month rolling average for Arctic sea ice extent set a new record in October 2011 at 10.66 million km². The previous record of 10.67 million km² had been set in October 2007.

The record for Arctic sea ice area has also been broken. The October 2007 was again the previous record, standing at 8.39 million km². Annual average Sea Ice Area dropped to 8.34 million km² for the 12-month period ending in October 2011.

Sea ice volumes have been decreasing far more quickly. The previous record value from PIOMAS was 15,075 km³, set in the 12-month period ending in January 2008, a record that held for just 29 months. The 12-month period ending in September 2011 set a new record, averaging 13,140 km³.

Global sea ice area (Arctic and Antarctic combined, as calculated at Cryosphere Today) has also reached its lowest maximum on record, as seen in this graph posted here.

It’s hard to see the new record in the graph above, but Neven posts this chart showing the numbers.

Earth’s cryosphere continues to wither under the assault from global warming.

Arctic sea ice is disappearing much faster and more dramatically than expected, according to new research by the Norwegian Polar Institute (NPI). Consequently, the Arctic Sea could be free of ice in the summer in ten years, rather than the 50 to 100 years previously estimated.

Here’s the abstract from “Thinning of Arctic sea ice 1990-2010 as observed by upward looking sonars – or why the Arctic Ocean could be ice free in summer in less than ten years“:

Time series of sea ice thickness observed in Fram Strait by moored sonars show a 35 percent reduction in multiyear (MY) modal ice thickness since 2005. The MY mode reflects the thickness of level ice which has survived at least one melt season, and is hence a reflection of the thermodynamic equilibrium. During the 1990s the late winter MY modal thickness was 3.4+-0.4 m. Following excessive export of MY ice during the winter of 2005, late winter MY modal ice thickness dropped to 2.2 +-0.1 m, which persisted until the end of our record in 2010. The reduced MY modal ice thickness is a result of the Arctic sea ice cover entering a new state, where dynamic and thermodynamic effects appear to have combined to shift the equilibrium towards thinner ice.

This new state includes a dramatic reduction in the fraction of ridged sea ice, compared to the 1990s. The vast fields of ridged ice thicker than 5 m, constituting 28 percent of the winter Arctic sea ice cover during the 1990s, is nearly gone. At the end of winter in 2010, ice thicker than 5 m constituted only 6 percent of the total ice mass observed. The combined effect on late winter mean ice thickness is a reduction from 4.3+-0.4 m during the 1990s to a record low value of 2.0 m in late winter 2010. We speculate that increased ocean heat flux plays an important role in the thinning of the thick ice. With the thickest ice nearly gone and the MY level ice thicknesses close to thicknesses typical for first year sea ice, we are approaching a state where favorable conditions could melt most of the Arctic sea ice cover during one summer. 

This graphic provided by the U.S. Navy shows how little older, thicker ice is left – just a thin band along the northern edge of the Arctic Archipelago and the north coast of Greenland.

The graphic here is animated – you can watch the older ice flowing out of the Arctic Sea through the Fram Strait.

Scientists at the University of Bremen are saying Arctic sea ice extent reached a new record low this year.

Alerting message from the Arctic: The extent the Arctic sea ice has reached on Sep. 8 with 4.240 million km2 a new historic minimum (Figure 1). Physicists of the University of Bremen now confirm the apprehension existing since July 2011 that the ice melt in the Arctic could further proceed and even exceed the previous historic minimum of 2007. It seems to be clear that this is a further consequence of the man-made global warming with global consequences. Directly, the livehood of small animals, algae, fishes and mammals like polar bears and seals is more and more reduced.

The University of Bremen’s ice map shows the Northwest and Northeast passages are simultaneously ice free
This happened for the first time in 2008 – it did not happen in 2007, the year that saw the record minimum ice extent.

The daily sea ice maps of the University of Bremen are based on observations of the Japanese microwave sensor AMSR-E, in orbit on board the NASA spacecraft Aqua since 2002. The institute receives the data from two servers in the US and Japan and produces the maps based on the ASI (ARTIST Sea Ice) algorithm using the 89 GHz channels of AMSR-E. Other retrieval algorithms like NASA Team or Bootstrap may find slightly different sea ice extent values.

To wit: the National Snow and Ice Data Center has just called the yearly minimum Arctic sea ice extent, finding it the second lowest in the satellite record.

Arctic sea ice appears to have reached its lowest extent for the year. The minimum ice extent was the second lowest in the satellite record, after 2007, and continues the decadal trend of rapidly decreasing summer sea ice.

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

* * *

The last five years (2007 to 2011) have been the five lowest extents in the continuous satellite record, which extends back to 1979. While the record low year of 2007 was marked by a combination of weather conditions that favored ice loss (including clearer skies, favorable wind patterns, and warm temperatures), this year has shown more typical weather patterns but continued warmth over the Arctic. This supports the idea that the Arctic sea ice cover is continuing to thin. Models and remote sensing data also indicate this is the case. A large area of low concentration ice in the East Siberian Sea, visible in NASA Moderate Resolution Imaging Spectroradiometer (MODIS) imagery, suggests that the ice cover this year is particularly thin and dispersed this year.

The Japan Aerospace Exploration Agency (JAXA) also pegs 2011 as the second lowest year for Arctic sea ice extent.

If September 9 holds up as the date of minimum ice extent, that’s the earliest date of minimum extent in years – and earlier than the average date (September 10) over the period of satellite records, which began in 1979.

While the absolute sea ice extent values might vary slightly from one method to the other – and even the day of the absolute minimum might vary slightly – all methods find consistently that all minima since 2007 have been lower than all minima before, i.e. the last four minima (2007-2011) are the four lowest on record.

And there’s little doubt that 2011 saw new record for Arctic sea ice volume . . .

. . . and area.

Global warming and climate change have already come to the Arctic. The full consequences of this new reality have yet to be seen.

The National Snow and Ice Data Center (NSIDC) reports Arctic sea ice extent averaged for August 2011 reached the second lowest level for the month in the satellite record, tracking near the record lows of 2007.

Arctic sea ice extent will likely reach its minimum extent for the year sometime in the next two weeks. If ice stopped declining in extent today, it would be the second-lowest minimum extent in the satellite record.

Both the Northwest Passage and the Northern Sea route appear to be open – for the fourth consecutive year.

Sea ice is now almost completely gone from the channels of the Northwest Passage, with the exception of a small strip of ice across a stretch of the Parry Channel. The southern route (Amunden’s Route) is ice free. According to the Canadian Ice Service, sea ice extent in the western Parry Channel is now the lowest at this time of year since record keeping began in 1966 and very little multi-year ice remains.

The fabled Northwest Passage opened for the first time in 2007. Now, it’s become routine. In 2008 the Northwest Passage and the Northern Sea Route were open simultaneously for the first time. This, too, seems now to be the new normal.

This chart from the Japan Aerospace Exploration Agency (JAXA) shows sea ice area approaching the record low set in 2007.

The area of sea-ice cover can be defined in two ways, sea ice “extent” and sea ice “area.” Sea ice “extent” is defined as the areal sum of sea ice covering the ocean (sea ice + open ocean), whereas sea ice “area”  counts only sea ice covering a fraction of the ocean (sea ice only). Thus, the sea ice extent is always larger than the sea ice area.

A new study confirms the minimum summertime volume of Arctic sea ice fell to a record low last year (2010) – but this year has already broken that record, as seen in this PIOMASS graph from the University of Washington’s Polar Science Center.

The decline in volume is even more apparent from this graph posted at Neven’s Arctic Sea Ice blog.

Sea ice volume in 2011 is already below last year’s record low. 2011 has already seen a new record minimum volume – and the melt season is not yet over.