Arctic Sea Ice

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http://www.agu.org/pubs/crossref/1998/98GL00251.shtml

Recent increase in the length of the melt season of perennial Arctic sea ice
Douglas M. Smith

Analysis presented here of the dates of spring melt and autumn freeze‐up observed over a large fraction of perennial Arctic sea ice using passive microwave data from the SMMR and SSM/I from 1979 to 1996 reveals an increase of 5.3 days (8%) per decade in the number of melt days per summer.

The above 1998 paper shows the melt period growth as 5.3 days per decade

A recent NASA article
http://www.nasa.gov/topics/earth/fea...lt-season.html

New NASA-led research shows that the melt season for Arctic sea ice has lengthened by an average of 20 days over the span of 28 years, or 6.4 days per decade. The finding stems from scientists' work to compile the first comprehensive record of melt onset and freeze-up dates -- the "melt season" -- for the entire Arctic.

So not only is the melt period increasing, that rate of increase is slowly accelerating.

Just to confuse the issue a little more a 2004 article.
http://ams.allenpress.com/perlserv/?...I%3E2.0.CO%3B2

Despite recent declines in the winter AO index, recent melt distributions did not show evidence of reestablishing spatial patterns similar to those observed during the 1979–88 low-index AO period. Recent freeze distributions have become increasingly similar to those observed during 1979–88, suggesting a recurrent spatial pattern of freeze chronology under low-index AO conditions.

Knowing the pattern is non linear does not mean we can yet use a quadratic best fit. The noise to signal is still noisy.

[sinimod]

And deniers cannot explain this away with wind piling up sea ice along one end of the Arctic Basin, or warmer waters from the positive phase of the PDO, or shifting ocean circulation patterns.

The PDO is now decidedly negative:

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http://nsidc.org/arcticseaicenews/index.html
February 3, 2010
Despite cool temperatures, ice extent remains low

Despite cool temperatures over most of the Arctic Ocean in January, Arctic sea ice extent continued to track below normal. By the end of January, ice extent dropped below the extent observed in January 2007. Ice extent was unusually low in the Atlantic sector of the Arctic, the one major area of the Arctic where temperatures remained warmer than normal.

Looking over the entire season, this winter continues the recent trend of slower Arctic ice growth. During the 1980s, the average rate of ice growth for January was approximately 90,000 square kilometers (35,000 square miles) per day. In comparison, during the 1990s, the average rate of January growth fell to about 40,000 square kilometers (15,000 square miles) per day. Including 2010, the average for the 2000s is 39,000 square kilometers (15,000 square miles) per day.

Analysis of data from the last three decades shows that the summer Arctic sea ice melt season now lasts nearly a month longer than it did in the 1980s. A later start of freeze-up and an earlier start to the melt season both contribute to the change. A recent paper by Thorsten Markus at NASA Goddard Space Flight Center suggests that the later freeze-up is the dominant factor lengthening the melt season. The analysis shows that, on average, autumn freeze-up starts nearly four days later each decade.

The linear rate of decline for January is now 3.2% per decade. So at the end of the century we will have a third less sea ice in January. But extrapolating the freeze up movement has no freeze up period in forty years. Linear decline of summer sea ice are shows no summer ice in 20 years, but linear decline of sea ice volume shows no summer ice before the end of the decade.

Unfortunately I do not know which is correct.

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Arctic Sea Ice Thinning
http://www.agu.org/pubs/crossref/200...JC005312.shtml

Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008
R. Kwok and others

We present our best estimate of the thickness and volume of the Arctic Ocean ice cover from 10 Ice, Cloud, and land Elevation Satellite (ICESat) campaigns that span a 5-year period between 2003 and 2008. Derived ice drafts are consistently within 0.5 m of those from a submarine cruise in mid-November of 2005 and 4 years of ice draft profiles from moorings in the Chukchi and Beaufort seas. Along with a more than 42% decrease in multiyear (MY) ice coverage since 2005, there was a remarkable thinning of ∼0.6 m in MY ice thickness over 4 years. In contrast, the average thickness of the seasonal ice in midwinter (∼2 m), which covered more than two-thirds of the Arctic Ocean in 2007, exhibited a negligible trend. Average winter sea ice volume over the period, weighted by a loss of ∼3000 km3 between 2007 and 2008, was ∼14,000 km3. The total MY ice volume in the winter has experienced a net loss of 6300 km3 (>40%) in the 4 years since 2005, while the first-year ice cover gained volume owing to increased overall area coverage. The overall decline in volume and thickness are explained almost entirely by changes in the MY ice cover. Combined with a large decline in MY ice coverage over this short record, there is a reversal in the volumetric and areal contributions of the two ice types to the total volume and area of the Arctic Ocean ice cover. Seasonal ice, having surpassed that of MY ice in winter area coverage and volume, became the dominant ice type. It seems that the near-zero replenishment of the MY ice cover after the summers of 2005 and 2007, an imbalance in the cycle of replenishment and ice export, has played a significant role in the loss of Arctic sea ice volume over the ICESat record.

http://www.jpl.nasa.gov/news/news.cfm?release=2009-107
New NASA Satellite Survey Reveals Dramatic Arctic Sea Ice Thinning

PASADENA, Calif. - Arctic sea ice thinned dramatically between the winters of 2004 and 2008, with thin seasonal ice replacing thick older ice as the dominant type for the first time on record. The new results, based on data from a NASA Earth-orbiting spacecraft, provide further evidence for the rapid, ongoing transformation of the Arctic's ice cover.

http://www.guardian.co.uk/environmen...ctic-ice-ocean

The Earth is going thin on top. A new study has revealed that the Arctic Ocean's permanent blanket of ice around the North Pole has thinned by more than 40% since 2004.

Scientists said the rapid loss was "remarkable" and could force experts to reassess how quickly the Arctic ice in the summer may disappear completely. They blame the loss on global warming, which has driven temperatures in the Arctic to record highs and summer ice extent to recent lows.

Unfortunately, the Icesat's data gathering days are nearly over. Two of its three lasers, used to judge the sea ice height, have already failed and the third is on its last legs. Icesat2, the satellite's replacement, is not planned for launch until 2014.

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Sea Ice Minimum 2010,
What is your guess for the sea ice minimum. No prize just bragging rights.

Unless anyone has a better ides lets use the September average as published by NSDIC.

I'll start the ball rolling: 4 million sq kms (ie record low)

References not required but appreciated.

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http://www.newscientist.com/article/...ce-exodus.html
Arctic arch failure leads to sea-ice exodus
26 February 2010 by Kate Ravilious

EVERY winter the Arctic ice cap is penned in by curved barriers of ice spanning the straits that lead out of the Arctic Ocean. Now it seems that some of these ice arches are failing to form. The resulting exodus of sea ice into the Atlantic and Pacific could affect ocean circulation and marine life.

During most years, large blocks of sea ice clump together in mid-January to build one or two arches across the strait. The arches usually persist for around six months, acting as dams to prevent the ice from floating away.

Then in 2007, the warmest year on record in the Arctic, no arches formed and vast quantities of sea ice were lost. "Around 1 per cent of Arctic ice by area went down the Nares Strait that year; more than double the usual amount," says Kwok. The next year wasn't much better - only one weak arch formed and broke down after two months (Geophysical Research Letters, DOI: 10.1029/2009GL041872). Last year provided a brief respite, but so far in 2010 there is no sign of any arches in the strait.

Peter Wadhams from the University of Cambridge agrees that the arches have become less stable, but isn't convinced that this will have much effect on overall ice flow. "The Nares Strait is a lesser outflow - the main one is the Fram Strait," he says. Fram is too wide to form arches.

[sinimod]

Originally Posted by 776281

Sea Ice Minimum 2010,
What is your guess for the sea ice minimum. No prize just bragging rights.

Unless anyone has a better ides lets use the September average as published by NSDIC.

I'll start the ball rolling: 4 million sq kms (ie record low)

References not required but appreciated.

The volume of multiyear sea ice in the Arctic has decreased by 42% from 2005 to 2008, with a thinning of approximately 0.6 m in multiyear ice over that period (Kwok, etal, 2009; http://www.agu.org/pubs/crossref/200...JC005312.shtml). The overall mean winter thickness of Arctic ice has decreased from 3.64 m in 1980 to 1.89 m in 2008 (Kwok and Rothrock, 2009; found here http://rkwok.jpl.nasa.gov/publications/index.html). This remarkable reduction of multiyear ice leaves a substantially increased seasonal ice cover that is highly susceptible to the increased melt period of the Arctic. It should be noted however, that there was a negligible trend in seasonal ice during this time period.


During the 1980s, the average rate of ice growth for January was approximately 90,000 square kilometers (35,000 square miles) per day. Including 2010, the average for the 2000s is 39,000 square kilometers (15,000 square miles) per day. (http://nsidc.org/arcticseaicenews/). During January 2010, ice extent grew at an average of 34,000 square kilometers (13,000 square miles) per day.

As Tony has pointed out, the summer melt season is lengthening. If this year continues the trend (and there is no reason to believe otherwise), then the chances for a record low summer minimum is greater. And with the low rate of ice growth this year, it appears it is possible that the minimum summer sea ice extent in 2010 could actually be lower than 2007. Coupling the longer melt season with the higher sea surface temperatures in the Arctic (http://data.giss.nasa.gov/gistemp/graphs/ ) indicates a longer season of more intense daily melting.

In addition, Kwok et al. (2010; http://www.agu.org/pubs/crossref/201...GL041872.shtml) points out that:

Sea ice flux through the Nares Strait is most active during the fall and early winter, ceases in mid- to late-winter after the formation of ice arches along the strait, and re-commences after breakup in summer. In 2007, ice arches failed to form. This resulted in the highest outflow of Arctic sea ice in the 13-year record between 1997 and 2009. The 2007 area and volume outflows of 87 × 103 km2 and 254 km3 are more than twice their 13-year means. This contributes to the recent loss of the thick, multiyear Arctic sea ice and represents ~10% of our estimates of the mean ice export at Fram Strait. Clearly, the ice arches control Arctic sea ice outflow.

Apparently, this year the arches are not forming, increasing the odds that there will be a larger than average outflow of ice from the Arctic Ocean. However, Wadhams of the University of Cambridge, is not convinced that the Nares Strait has much effect on the overall ice flow by indicating that the main ice outflow is through the Fram Strait, which is too wide to form arches. (http://www.newscientist.com/article/...climate-change) At this point, I am giving Kwok the benefit of the doubt and I believe that the lack of arch formation in the Nares strait will increase ice outflow and decrease the minimum sea ice extent this year.

The record low for January was actually in 2006. We all know that 2007 had the record low summer sea ice extent on September 18, 2007 at 4.13 million km2. The sea ice extent for 2009-2010 has been tacking the 2006-2007 sea ice extent thus far, at times behind the 06-07 line, and at times ahead of that line. So, just based on that, it appears 2010 will be very close to the record of 2007.

So, given the trend in decreasing multiyear ice, the decreasing rate of winter ice growth, the lengthening melt period, the higher sea surface temperatures in the Arctic, the failure of arch growth in the Nares Strait, and the tacking of ice extent of this year with the record of 2007, at this point, it appears there is a good chance that this year will reach a record low summer sea ice extent. Therefore, I agree with Tony that the minimum sea ice extent this year will be below the 4.13 million sq kms. I don't mean to cop out on making a different guess, but his guess of about 4 million sq kms seems reasonable to me, given the situation as I described above.

[wibble]

My bid, based on pure pessimism alone, is 3.8 million square kilometres.

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After all that talk I've decided to go a little conservative and say 4.05 million sq km. That's my final answer.

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In March of this year the Arctic went through a cold spike and the sea ice extent reached near the average extent established for 1979 through 2000. However, the rate of sea ice melting accelerated significantly in May, so that as of now the Arctic sea ice extent is actually below that experienced during May of 2007.

[sinimod]

But as Stoat reminds us,

2006 was well below 2007 at this point, and turned out to be uninteresting.

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Yes but the sea ice volumes are still screaming downwards.

Climate Progress's take.
http://climateprogress.org/2010/05/2...steve-goddard/

The loss of multi year ice is significant.

And the Rabett has an opinion.
http://rabett.blogspot.com/2010/05/w...cold-snap.html
Also points to ice volumes.

Accuweather did not see a problem on May 10.
http://www.accuweather.com/blogs/cli...-arctic-se.asp

http://nsidc.org/arcticseaicenews/index.html
on 6 May

April 2010 compared to past years
Average ice extent for April 2010 was 820,000 square kilometers (317,000 square miles) greater than the record low for April, observed in 2007, and 310,000 square kilometers (120,000 square miles) below the average extent for the month. The linear rate of decline for April over the 1979 to 2010 period is now 2.6% per decade.

So depite a very late start to the melt season, it has gained considerable momentum.

Record low still looks a good prediction. But we all predicted a record low.

[sinimod]

Originally Posted by 776281

Yes but the sea ice volumes are still screaming downwards.

Climate Progress's take.
http://climateprogress.org/2010/05/2...steve-goddard/

The loss of multi year ice is significant.

And the Rabett has an opinion.
http://rabett.blogspot.com/2010/05/w...cold-snap.html
Also points to ice volumes.

Accuweather did not see a problem on May 10.
http://www.accuweather.com/blogs/cli...-arctic-se.asp

http://nsidc.org/arcticseaicenews/index.html
on 6 May


So depite a very late start to the melt season, it has gained considerable momentum.

Record low still looks a good prediction. But we all predicted a record low.

Very true and definitely a very important point!! I just mentioned the last point because it is possible that there could be a cooler summer than 2007, and therefore, possibly less sea ice melting than 2007.

The low volume and thinner ice cover is conducive to rapid changes in sea ice extent. Due to a cooler than average March, Arctic sea ice extent rapidly increased to near the average for the 1979 to 2000 period. However, that ice was extremely thin and extremely vulnerable to even a relatively short warm period, as evidenced by the rapid decline in sea ice extent beginning near the end of April and extending to the present. Clearly, young thin ice is far more vulnerable to large changes in extent.

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http://nsidc.org/arcticseaicenews/index.html
The May update is in.

Arctic sea ice extent declines rapidly in May
In May, Arctic air temperatures remained above average, and sea ice extent declined at a rapid pace. At the end of the month, extent fell near the level recorded in 2006, the lowest in the satellite record for the end of May. Analysis from scientists at the University of Washington suggests that ice volume has continued to decline compared to recent years. However, it is too soon to say whether Arctic ice extent will reach another record low this summer—that will depend on the weather and wind conditions over the next few months.

The May average looks better than the end of May figure.

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http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

Sea ice extent
The latest value : 9,578,281 sq km (June 22, 2010)

Or if you prefer sea ice area 7.884 million sq km
http://arctic.atmos.uiuc.edu/cryosphere/

Sea ice extent does not take out the holes inside the ice areas.

And the multi year ice? Rotten
http://umanitoba.ca/news/blogs/blog/...-goes-missing/

In September 2009 Barber and others went to various points in the southern Beaufort Sea aboard the research vessel (NGCC) Amundsen. They discovered the multiyear sea icescape was not as ubiquitous as it appeared in satellite remote sensing data. And much of the multiyear ice, which is integral to maintaining the ecosystem and its inhabitants, was so heavily decayed the Amundsen easily broke through floes six to eight meters thick. Indeed, through most of the journey the Amundsen sailed at an average speed of 24km/h; its open water cruising speed is about 25km/h.

The Amundsen is a 1200 class ice breaker, should be able to chug through 4 foot ice and back up and ram about eight foot.

I have just realise that I did not specify ice area or ice extent, but NSDIC is ice extent.

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http://www.scientificblogging.com/ch..._ice_june_2010

An interesting analysis of ice quality and extent. Another who thinks this year is very different, there are disturbing signs of considerably increased ice mobility.

It would not take much for our estimates of a record low to be way off the mark. The record low could easily be much worse.

Now all we need is an update of
http://www.springerlink.com/content/t662290qju75j657/
Examples of ice pack rigidity and mobility characteristics determined from ice motion
James K. Lewis1, Ronald E. Englebretson2 and Warren W. Denner2

Abstract A method has been developed to determine ice pack rigidity and mobility using observed ice motion. Using this method, one may determine how solidly the ice pack is frozen in near real-time. In addition, spatial and temporal variations in the freezing and thawing of the ice pack can be studied. Various degrees of ice rigidity were considered using remotely-sensed ice motion off the N coast of Alaska during 1975 and 1979. Summer-time ice rigidities were detected first in late June 1975 and lasted through September 1975. However, in 1979 considerably higher rigidities were found in August while summer-like rigidities were detected into late November. Analyses of atmospheric pressure distributions suggest that less mechanical breakup occurred in the summer of 1979, resulting in the greater rigidities during August of that year. In addition, minimum ice coverage was 21% less in the Beaufort Sea in 1979 than in 1975. The result was a relatively large percent of thinner ice for November of 1979 than for 1975, the likely cause of the less rigid conditions detected during the fall of 1979.

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http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm
The latest value : 9,123,594 km2 (June 27, 2010)

http://climateprogress.org/2010/06/2...comment-282675

Most attention gets focused on the more visible but less important metric of sea ice extent, which collapsed last month faster than any May in the satellite record. As a result, at least one group in the highly touted suite of forecasts is looking to sharply lower their September sea ice extent estimate.

http://arctic.atmos.uiuc.edu/cryosph....color.000.png

http://www.scientificblogging.com/ch...arctic_recover
http://www.scientificblogging.com/ch...olstice_update

The rapid ice melt this year began at the end of March, accelerated in late April and continues at about the same rate. The melt extent is already ahead of 2007. Considering that melt in 2007 didn't really begin to take off until the 4th week in June, we must expect that by the last day of June the ice extent will be dramatically below 2007 levels.

A lot of the sea ice concentration in the Arctic Basin is well below 100%


I had thought the late increase in sea ice extent surprising but a good thing. Surprising yes good no, the increase in extent appears to be a very early export of ice from the Arctic Basin.

Ladies and gentlemen we are witnessing history, maybe not the end of summer sea ice yet, but is is going to be very very low. Just look at the difference in sea ice concentrations today compared to Patrick Lockerby's blog (Chatterbox) just a few days ago.

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The loss of Arctic sea ice has only been noticed over the last few decades right?

How about this then; "A decrease in ice, due to the heating of the Arctic region is also noticable in the East Spitzbergen area."

Arctic Sea Ice, published by the National Academy of Sciences and the National Research Council in 1958

Some intersting stuff, might go back if I can find it.

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From JAXA
The latest value : 8,983,125 km2 (June 28, 2010)
one day loss 140,469 sq km and over 70 days until the melt season ends.

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The latest value : 8,907,656 km2 (June 29, 2010) JAXA ice extent
Phew not as bad. Figures are subject to review, so I suppose single day changes are not really relevant. But I am going to anyway

Cyrosphere has the ice area at 6.784 milllion sq km and they don't put the date on that figure. Is the ice extent - ice area difference bigger than ususal?