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Sea ice extent continues to decline, and is now at 4.24 million square kilometers (1.63 million square miles), falling yet further below the previous record absolute minimum of 5.32 million square kilometers (2.05 million square miles) that occurred on September 20–21, 2005.

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The image below shows the current (Sept 10, 2007) extent of the Arctic Ice Cap. The magenta line indicates the normal extent of the icecap at it's summer minimum for the last 30 years. As you can see the current icecap area is far below the normal area. And it's still shrinking!



The graph shows the current area of the Arctic icecap compared to previous years. The 2007 icecap is reduced by 40% from it's normal area!




View the historical data using Google Earth
Check it out in Google Earth. The attached .kml file includes an time based animation of the icecap's extent. Use the time slider to see the normal Arctic summers from 1978 to 2006. This animation was obtained from the NSIDC Google Earth page. Check it out to see this and much other data about the state of the c cryosphere .

Real time View of the Arctic
You can also see the extent of the Arctic ice cap in real time directly in Google Earth. The attached overlay is being updated everyday.



Opening of the Northwest Passage
The retreat of the icecap has opened up the fabled Northwest Passage for the first time!

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On August 21, 2007 the Northwest Passage became open to ships without the need of an icebreaker. According to Nalan Koc of the Norwegian Polar Institute this is the first time since they began keeping records in 1972.

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Northwest Passage opens for business
This has fueled speculation this the shift from global warming will open up the Arctic for business . From the Canadian National Post

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Just a week after Canada and the U.S. agreed to disagree over the ownership of the Northwest Passage, this summer's record melt of Arctic sea ice has unlocked the fabled polar shipping route more completely than ever before, the U.S. National Snow and Ice Data Center has announced.

"It's open," Mark Serreze, a senior scientist with research institute based in Boulder, Colo., said in an interview Tuesday. "It's unprecedented. Theoretically you could take a ship from Tokyo through the Northwest Passage to Boston. Not an easy sail, not a Sunday cruise, but it has started to happen."

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"The namesake glaciers for Glacier National Park are disappearing rapidly," he said. "Especially in the last several decades. These glaciers that numbered 150 when the park was first formed are now less than 27." More than 7,000 years ago, glaciers 900 to 1,500 meters thick covered this landscape. The constant ice flow carved out these jagged peaks and deep valleys. Now, Dan Fagre says the remaining glaciers are melting at an alarming rate. He blames global warming. "One glacier by itself can not invoke climate change. But, when you have all the glaciers in almost all of the mountain ranges of the entire globe responding the same way, then you know you have global phenomena. And in this case, the glaciers are responding to warming."

Fagre says if the current melting trend continues all of the glaciers will be gone within 20 years.

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Unbelievable is probably an understatement - I don't think anyone was predicting this. Also troubling is the asymmetry of the icecap, as if something unique is happening this year in the western half of the Arctic.




The temp anomalies have been stronger in the west, but I suspect something may also be going on with the ocean currents. To quote from the NSIDC web page

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Impacts of ocean circulation

In the August 22 report, we explained that another part of the 2007 story is "memory" of the sea ice to changes that have been unfolding over the past few decades. Our focus there was on the apparent transition to younger, thinner ice since the late 1970. As discussed, factors contributing to this thinning involve a general rise in air temperatures, and changing winds that have transported fairly thick ice out of the Arctic Ocean into the North Atlantic. An issue that we haven't addressed, yet, is changes in ocean circulation.

One prominent researcher, Igor Polyakov at the University of Fairbanks, Alaska, points out that pulses of unusually warm water have been entering the Arctic Ocean from the Atlantic, which several years later are seen in the ocean north of Siberia. These pulses of water are helping to heat the upper Arctic Ocean, contributing to summer ice melt and helping to reduce winter ice growth. Another scientist, Koji Shimada of the Japan Agency for Marine–Earth Science and Technology, reports evidence of changes in ocean circulation in the Pacific side of the Arctic Ocean. Through a complex interaction with declining sea ice, warm water entering the Arctic Ocean through Bering Strait in summer is being shunted from the Alaskan coast into the Arctic Ocean, where it fosters further ice loss.

Many questions still remain to be answered, but these changes in ocean circulation may be important keys for understanding the observed loss of Arctic sea ice.

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Here is another fascinating graphic from the NSDIC.


The animated gif shows the age composition of the Arctic ice between 1982 and 2007. You can see both the activity of the ice currents, and the age of the ice. Importantly the ice is becoming younger. It also as if like much of the oldest ice melted this year.

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Changes in ice age and thickness

Another aspect of the story for 2007 is the "memory" of the sea ice to changes over the past few decades. Specifically, there seems to have been a transition to younger, thinner ice beginning in the late 1970s. This reflects not only trends towards more summer melt and less winter ice growth, but changing winds that have transported fairly thick ice out of the Arctic Ocean into the North Atlantic, and decreased the length of time that ice is "sequestered" in the Arctic Ocean where it might have a chance to grow thicker.

Ice that has survived through one summer, called second-year ice, is typically thicker than first-year ice, and ice that has survived several summers is assumed to be thicker than second-year ice. To estimate ice age, our colleagues Chuck Fowler and Jim Maslanik at the University of Colorado used drifting buoy data along with information from satellites to assess the formation, transport, and melt of the ice, which they in turn used to estimate ice age. Results from this study reveal the area of oldest ice (i.e., ice older than four years) is decreasing in the Arctic Ocean, and being replaced by younger, and therefore, thinner ice. The region of the oldest (and thus thickest) ice is now confined to a relatively small area north of the Canadian Archipelago. Replenishment of old, thick ice is essential to the maintenance and stability of the Arctic summer ice cover, since thinner ice requires less energy to completely melt out in summer than thicker ice.

Figure 4 shows an animation of ice age in the Arctic from 1981 through 2007. The colors indicate the age of the sea ice in years; light blue is open water (OW). Areas in red are locations where the ice is five years or older, whereas the dark blue areas are first-year ice. The overall reduction in ice age over the past twenty-six years becomes evident as the animation runs through the years. The animation also shows seasonal variations in the ice cover as the first-year ice melts in the summer and regrows in the winter.

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Hi Hill:
The overlays in the attachment were generated on lat-lon grid by the folks at NSIDC, so they do overlay 'around' the pole. As far as I know, you still can't place an overlay 'across' the pole. Too bad since we now have some good images of the pole that would make a good overlay. These are from the European Space Agency and they show the current (Sept 2007) Arctic ice extent

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Envisat ASAR mosaic of the Arctic Ocean for early September 2007, clearly showing the most direct route of the Northwest Pssage open (orange line) and the Northeast passage only partially blocked (blue line). The dark gray colour represents the ice-free areas, while green represents areas with sea ice.

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Here is a link to the high res image High res Arctic

And here is a useful animation showing the extent of the Sept ice for the last 3 years. (2005 was a record low at the time):



Edited by blt (09/16/07 09:24 AM)

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The distribution and size of the [data] suggest that Arctic Ocean circulation changed from the counterclockwise pattern it exhibited in the 1990s to the clockwise pattern that was dominant prior to 1990. Reporting in Geophysical Research Letters, the authors attribute the reversal to a weakened Arctic Oscillation, a major atmospheric circulation pattern in the northern hemisphere. The weakening reduced the salinity of the upper ocean near the North Pole, decreasing its weight and changing its circulation. "Our study confirms many changes seen in upper Arctic Ocean circulation in the 1990s were mostly decadal in nature, rather than trends caused by global warming," said Morison.

"While some 1990s climate trends, such as declines in Arctic sea ice extent, have continued, these results suggest at least for the 'wet' part of the Arctic -- the Arctic Ocean -- circulation reverted to conditions like those prevalent before the 1990s," he added.

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Fortunately 2007 is international Polar Year: 2007 - 2008 and significant data has been collected which may document the causes of the sea ice decline more concretely.

The chart below shows contours of the trend in ocean bottom pressure from 2002 to 2006. Apparently this may signal a shift to colder conditions in future.

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Scientists in the US have presented one of the most dramatic forecasts yet for the disappearance of Arctic sea ice. Their latest modelling studies indicate northern polar waters could be ice-free in summers within just 5-6 years. Professor Wieslaw Maslowski told an American Geophysical Union meeting that previous projections had underestimated the processes now driving ice loss. Summer melting this year reduced the ice cover to 4.13 million sq km, the smallest ever extent in modern times.

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Professor Maslowski's group, which includes co-workers at Nasa and the Institute of Oceanology, Polish Academy of Sciences (PAS), is well known for producing modelled dates that are in advance of other teams.These other teams have variously produced dates for an open summer ocean that, broadly speaking, go out from about 2040 to 2100. But the Monterey researcher believes these models have seriously underestimated some key melting processes. In particular, Professor Maslowski is adamant that models need to incorporate more realistic representations of the way warm water is moving into the Arctic basin from the Pacific and Atlantic oceans.


"My claim is that the global climate models underestimate the amount of heat delivered to the sea ice by oceanic advection," Professor Maslowski said."The reason is that their low spatial resolution actually limits them from seeing important detailed factors."We use a high-resolution regional model for the Arctic Ocean and sea ice forced with realistic atmospheric data. This way, we get much more realistic forcing, from above by the atmosphere and from the bottom by the ocean."

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Cold Winter in 2008?
The winter of2007/8 has spawned news stories about it's severe cold and has been touted as proof that 'global warming' movement has been fabricated for political gain. However the science indicates that while this last winter has been colder than usual (in parts of N America and over the Pacific), it's still quite a bit warmer than the historic means.



Winter 2008
One indication of this is the latest assessment of the extent of the Arctic sea ice from NASA .

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Arctic sea ice grows and declines seasonally, ranging from an average minimum extent in September of 2.5 million square miles to an average winter maximum extent of 5.9 million square miles in March. This March, instruments on NASA’s Aqua satellite and NOAA and U.S. Defense Department satellites showed the maximum sea ice extent slightly increased by 3.9 percent over that of the previous three years, but it is still below the long-term average by 2.2 percent. Increases in ice extent occurred in areas where surface temperatures were colder than the historical averages. At the same time, as a result of the export of ice from the Arctic, the area of perennial ice decreased to an all-time minimum.

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While this was the fifth least February sea ice extent on record, the story is more interesting when the age of the ice is plotted

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The ice in the Arctic is much younger than normal, with vast regions now covered by first-year ice and much less area covered by multiyear ice. Left: February distribution of ice by its age during normal Arctic conditions (1985-2000 average). Right: February 2008 Arctic ice age distribution

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El Nina
The current drop in temp is in line a the effects expected from an El Nina event. Here is a rollup of the 2008 winter temperatures from NYT article. The El Nina : Nino oscillation is manifested by a decade long oscillation of sea-surface temperatures in the Pacific


Edited by blt (03/22/08 03:36 PM)

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This season, the Arctic sea ice appears to be headed to another record low. The NSIDC continues to monitor the sea ice and has an excellent summary web page on the current state of the Arctic and scientific commentary on the current retreat. Most interesting is the real time chart showing the extent of the sea ice compared to 2007's record low

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As you can see we are on track for another record low. Last year the Arctic sea ice broke up at a record rate during the last few weeks of June and July. This year, the sea ice is exceptionally new and thin and if the same percentage of one year old ice melts as previous years, we can expect another historical low.

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This bar plot shows estimates of sea ice extent at the 2008 September minimum based on known ice survival rates. The blue dotted line indicates the record-breaking minimum extent of 2007; the red dotted line shows the mean estimate based on all years between 1983 and 2007.

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