One of the interesting things about being a scientist is seeing how unexpected observations can galvanize the community into looking at a problem in a different way than before. A good example of this is the unexpectedly low Arctic sea ice minimum in 2007 and the near-repeat in 2008. What was unexpected was not the long term decline of summer ice (this has long been a robust prediction), but the size of 2007 and 2008 decreases which were much larger than any model had hinted at. This model-data mismatch raises a number of obvious questions – were the data reliable? are the models missing some key physics? is the comparison being done appropriately? – and some less obvious ones – to what extent is the summer sea ice minimum even predictable? what is the role of pre-conditioning from the previous year vs. the stochastic nature of the weather patterns in any particular summer?
The concentration of polar expertise on the last couple of questions has increased enormously in the last couple of years, and the summer minimum of 2009 will be a good test of some of the ideas that are being discussed. The point is that whether 2009 is or is not a record-setting or near-record setting minimum, the science behind what happens is going to be a lot more interesting than the September headline.
In the wake of the 2007 minimum, a lot of energy went in to discussing what this meant for 2008. Had the Arctic moved into a different regime where such minima would become normal or was this an outlier caused by exceptional weather patterns? Actually this is a bit of false dichotomy since they aren’t exclusive. Exceptional patterns of winds are always going to be the proximate cause of any extreme ice extent, but the regime provides a background upon which those patterns act. For instance, in the paper by Nghiem et al, they showed the influence of wind patterns in moving a lot of thick ice out of the Arctic in early 2007, but also showed that similar patterns had not had the same impact in other years with higher background amounts of ice.
This ‘background’ influence implies that there might indeed be the possibility of forecasting the sea ice minimum a few months ahead of time. And anytime there is the potential to make and test predictions in seasonal forecasting, scientists usually jump at the chance. So it proved for 2008.
Some forecasting efforts were organised through the SEARCH group of polar researchers, and I am aware of at least two informal betting pools that were set up. Another group of forecasts can be found from the Arctic ice forecasting center at the University of Colorado. I personally don’t think that the intrinsic worth of a successful prediction of overall sea ice extent or area is that societally relevant – interest in open shipping lanes that might be commercially important need much more fine-grained information for instance – but I think the predictions are interesting for improving understanding of Arctic processes themselves (and hopefully that improved understanding will eventually feed into the models and provide better tests and targets for their simulations).
What was particularly interesting about last years forecasts was the vast range of forecasting strategies. Some were just expert guestimates, some people used linear regression on past data, some were simply based on persistence, or persistence of the trend. In more mature forecasting endeavours, the methods tend to be more clustered around one or two proven strategies, but in this case the background work is still underway.
Estimates made in June 2008 for the September minimum extent showed a wide range – from around 2.9 to 5.6 M km2. One of the lowest estimates assumed that the key criteria was the survivability of first year ice. If one took that to be a fixed percentage based on past behaviour, then because there was so much first year ice around in early 2008, the minimum would be very low (see also Drobot et al, 2008). This turned out not to be a great approach – much more first year ice survived than was predicted by this method. The key difference was the much greater amount of first year ice there was near the pole. Some of the higher values assumed a simple reversion to trend (i.e. extrapolation forward from the long-term trend to 2008).
Only a couple of the forecasts used physics-based models to make the prediction (for instance, Zhang et al, 2008). This is somewhat surprising until one realises how much work is needed to do this properly. You need real time data to initialise the models, you need to do multiple realisations to average over any sensitivity to the weather, and even then you might not get a range of values that was tight enough to provide useful information.
So how did people do? The actual 2008 September minimum was 4.7 M km2, which was close to the median of the June forecasts (4.4 M km2) – and remember that the 2007 minimum was 4.3 M km2. However, the spread was quite wide. The best estimates used both numerical models and statistical predictors (for instance the amount of ice thicker than 1m). But have these approaches matured this time around?
In this year’s June outlook, there is significantly more clustering around the median, and a smaller spread (3.2 to 5.0 M km2) than last year. As with last year, the lowest forecast is based on a low survivability criteria for first year ice and I expect that this (as with last year) will not pan out – things have changed too much for previous decades’ statistical fits on this metric to be applicable. However, the group with the low forecast have put in a ‘less aggressive’ forecast (4.7 M km2) which is right at the median. That would be equal to last year’s minimum, but not a new record. It would still be well below the sea ice trend expected by the IPCC AR4 models (Stroeve et al, 2008).
There is an obvious excitement related to how this will pan out, but it’s important that the thrill of getting a prediction right doesn’t translate into actually wanting the situation to get worse. Arctic ice cover is not just a number, but rather a metric of a profound and disruptive change in an important ecosystem and element of the climate. While it doesn’t look at all likely, the best outcome would be for all the estimates to be too low.
BobFJ:
> Yes, you are right I did miss that point,
Thank you!
@ manacker 24 Jul 2009 at 7:33 am
“Based on a quick look at the satellite photos, let’s assume that half of the Arctic surface area is covered by clouds, which reflect incoming solar radiation, so that its surface albedo is essentially unaffected by the state of the sea below (ice or water).”
This is an oversimplified assumption which will lead to underestimation of the effect of water versus snow-covered ice. Clouds scatter light down as well as up, so the surface state below them has an effect – to see the effect in qualitative lay terms, put down a sheet of wax paper (model “cloud”), half over white paper (model “snow covered ice”), half over black construction paper (model “open water”). Use several sheets of waxed paper to simulate thicker clouds, or several layers of clear plastic under the wax paper to simulate higher cloud base. How thick a model “cloud layer” does it take to hide the difference between the model “snow covered ice” and “open Water”?
“NSIDC data show us that the average summer-month (April-September) Arctic sea ice extent was 10.93 million km^2 (1979-2000 baseline) and 9.87 km^2 (latest 2008/09 values).
At the same time Antarctic sea ice extent was 9.66 million km^2 (1979-2000 baseline) and 10.09 million km^2 (latest 2008/09 values) for the summer months there (October-March).”
Averaging over six month periods is another oversimplification that will lead to an underestimation of the effect of loss of ice cover. The insolation varies with time, as the sun moves higher in the sky, following a curve that is roughly the top half of a sine wave. As the sun moves higher in the sky and the incoming radiation increases, the open water area is also increasing, multiplying the effects. Google “crest factor” and “root mean squared” to learn more. To get an accurate estimate, you would need to multiply the changing insolation by the changing absorption curves on a point by point basis, and integrate the area under the resulting curve.
“This is obviously not a problem.”
Diluting the affected Arctic area (where the methane hydrates are concentrated) by averaging in the area of the rest of the globe where the heat will eventually end up erroneously underestimates the transient catastrophic effect.
pete best 24 Jul 2009 at 8:14 am
Truly staggering indeed. I keep on wondering why, since we know this free ride is going to stop, we’re not acting in a more concerted way to ease our way out of the problem? Quite apart from climate change, we’ve got a huge problem on our hands here, it’s going to manifest itself in a big way in little more than a generation even if we give not a whit about what parts of the planet are newly dessicated, etc.
Again, I believe the author too casually dismisses the damping effect on necessary action created by existing industry that is directly concerned with fossil fuels. From manufacturers of boilers to tiny firms attempting to produce better diesel emissions controls, there’s an enormous amount of potential inertia here. Many of these actors are sufficiently organized (API, for instance) to form a diamond-hard constituency and public relations message apparatus, arrayed against a mushy and disorganized rabble of environmentalists, alternative energy interests, etc. History is littered with examples of the outcome of knives left resting edgewise on warm butter.
So between misdirection, sloth, and denial we recline in ease, watching and doing nothing as prices for fossil fuels not only inevitably rise but become increasingly chaotic, unpredictable and dangerous. We’re in a deck chair, sitting on the tracks with a tasty cocktail in our hands, waiting for the fossil fuel powered juggernaut to crush us flat even as it runs out of motive power.
John P. Reisman (274), it seems a bit misleading, though I don’t choose to make a big deal out of it. While the average ice albedo exceeds 50% as your reference states, to take ‘snow-covered ice might exceed 80%’ to a simple diagram with a smiley Sun getting reflected 85% over ice (it looks a little snow-covered but the title says “ice”) is quite a stretch for a general idea.
The shown water albedo is pretty good.
Thanks Doug Bostrom for this:
“So between misdirection, sloth, and denial we recline in ease, watching and doing nothing as prices for fossil fuels not only inevitably rise but become increasingly chaotic, unpredictable and dangerous. We’re in a deck chair, sitting on the tracks with a tasty cocktail in our hands, waiting for the fossil fuel powered juggernaut to crush us flat even as it runs out of motive power.”
—
It was said recently that at the moment we are experiencing the beginning of a permanent drought in the southwest which has recently been named as one of the first obvious US outcomes.
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I’d like to know if there is any connection between Atlantic (not Pacific) northern cool and current Arctic and Greenland melting. In my naive unscientific way, I look at those satellite images and it seems likely. Does anyone know anything that will enlighten my ignorance?
—
I understand that comparative pictures of Greenland this year/last year will soon be available, and think they will startle. I’ll have to look out some maps and see how much of a “bowl” it is and how much of that ice is inside it.
—
On the lay front, several excellent PBS programs have provided information that seems to me to be relevant to the discussion above.
Nova’s Extreme Ice shows glacier melt and even goes down into a moulin hole.
Alan Alda takes a walk in northern areas and shows and discusses permafrost and albedo with scientists, in relationship to trees, shrubs, growth, etc.
I found this fascinating and it might be useful to a slightly larger sliver of the population than hardworking scientists. Chris Mooney has been pushing for communication and Alan Alda doesn’t get enough credit for the great job he does on this.
Brian, thanks for a good discussion.
Anne van der Bom Reur 298:
[edit] Yet again; NO, I did not say that!
Kevin McKinney Reur 300, in part:
Quickly; Well actually the discussion is about the complex dynamic of ice SHELVES in Antarctica. Can you elaborate what part of the world you are refering to and where/how the observations were made?
Oh and BTW, the further down a crack, (that has not yet propagated all the way through), the more likely it is (if water can get down there), that freezing will take place because of the huge difference in “thermal mass”.
Quickly: And neither will snow and ice reflect infrared? Is it not black in those wavelengths? Do you have time to check that out for me please?
Re: #302 with regard to #296
Dear Brian,
Once again, thanks!
manaker at #296 says:
“So, if the surface albedo was changed from 80 to 37.5% due to melting ice, this means that the average albedo of the Earth was lowered by 0.06% (from 30% to 29.94%). Not much of an ‘albedo feedback’ there.”
Brian clarifies:
“Diluting the affected Arctic area (where the methane hydrates are concentrated) by averaging in the area of the rest of the globe where the heat will eventually end up erroneously underestimates the transient catastrophic effect.”
What you said!
Looks like the NW passage(siberia) is about to open, been watching it over the last few weeks and it is melting rapidly, by the look at how it’s going I bet it will exceed last years. The NE passage is melting less rapidly and will probably not completely open I my guesstimation.
In post 291, doofus:
“I don’t know if you have caught-on yet but these mechanical hinging failures of ice shelves do not happen overnight, but perhaps over a decade or so.”
And no mention of ANY OTHER EFFECT.
Now if you want to change your story again, do so. but do so clearly, rather than just straight out denial.
Denial isn’t a river in Egypt, you know…
re 309 have you got that the wrong way around? Siberia is the NE passage and looks likely to open soon. The NW passage through the Canadian Archapeligo looks iffy.
Lawrence (#310, 3:07 am)–NE is Siberia, yes? NW is Canadian archipelago.
I’m thinking they are both going to open, FWIW.
#309 Lawrence, The NE passage is traditionally known as the passage on top of Eurasia, The NW passage is the term used for North American Arctic.
And now for something completely different: +18 C at 83 degrees North!
http://www.weatheroffice.gc.ca/trends_table/pages/ylt_metric_e.html
New uncharted passages should open. Its a tad less cloudy, as one would expect when temperatures are simply too warm in the Arctic.
It will be +27 in Inuvik Canada as per forecast. Watch the Beaufort Sea Expand really fast as well.
http://www.weatheroffice.gc.ca/forecast/canada/index_e.html?id=NT
For Alert temps, as I remember, we were lucky to get +5 during the summer, back in the 80’s.
http://www.eldoradocountyweather.com/canada/climate/alertclimate.html
Again, this data begets serious attention, and also absolute negation of a so called “pause” in warming. Some model experts should
respond to these events accordingly. Unlike elsewhere in the world, Arctic temperatures do not have the tendency to vary wildly, and are truly a reflection of climatic trends and of the landscape and sea scape around, rather than the usual spike on a temp graph.
From Wayne’s link:
ding! http://www.weatheroffice.gc.ca/data/saisons/images/mfe1t_s.gif
so the 18 degrees up in the 83o would be sort of out of line? Funny but there have been some of days in Scandinavia too which have been hotter in the north (70o)than in the south (60o). Never used to happen, but I may recall this wrong. Some sort of analysis could be done.
So there’s still a stubborn cool spot over the southern part of Hudson’s Bay, if I read that correctly. Hudson’s Bay has been one area that has been melting slower than the 1979-2000 average, judging by the NSIDC daily map, and of course it’s been cool south of there clear into the American mid-West.
But that stubborn bit of Hudson’s Bay ice is almost gone. The slope of the daily graph at IJIS, NSIDC and yes, even denialist-favorite Arctic Roos as steepened. Even Arctic Roos now shows the ice extent almost down to the 2008 level, and it’s crossing the 2008 ice area.
In the far turn, we’ve got a horse race, people! 2007 by a length over 2009, followed by 2008 trailing by a head, with 2009 starting to make its move along the rail…
Rod B, 304 and John. P. Reisman, Reur 274:
Here is an extract from Wiki’
Although the reflectivity of water is very low at low and medium angles of incident light, it increases tremendously at high angles of incident light such as occur on the illuminated side of the Earth near the terminator. (early morning, late afternoon and near the poles).
And here is their graph:
http://en.wikipedia.org/wiki/File:Water_reflectivity.jpg
Kevin McKinney Reur 300, last part:
In fact, snow is an extremely good absorber of infrared EMR.
This fact is demonstrated in this photo taken with infrared film. “Snow White” on Flickr photo sharing
http://farm4.static.flickr.com/3472/3365391796_169fea972f_m.jpg
What may appear to be counter-intuitive is that the “hottest” part of the image is from the snow. This means that the most powerful emitter of infrared in the image is the snow.
In turn, it follows from Kirchhoff’s law of radiation, that snow is a powerful absorber. (a black body in that spectrum)
Itg may be off topic but are there any sites that show land ice?, since UIUC no longer do. It would be intersting to see if the ice on Baffin or Ellsmire islands are surviving the warm condtitions. Is Greenland having above normal melt?
If you want to see a slightly broader picture of Arctic temperatures on a spot basis, this site has a map with little yellow dots on the entire Arctic Circle (none of the dots on the eastern coast of Greenland works, unfortunately). It is a bit hokey looking, but the info is good.
http://www.athropolis.com/map2.htm
For example, clicking on Fairbanks, Alaska, gives this info:
July 25, 2009, weather report for
FAIRBANKS, ALASKA, USA
Weather report as of 61 minutes ago (23:55 UTC):
The wind was blowing at a speed of 3.1 meters per second (6.9 miles per hour) from South/Southwest in Fairbanks, Alaska. The temperature was 22 degrees Celsius (72 degrees Fahrenheit). Air pressure was 1,017 hPa (30.03 inHg). Relative humidity was 30.8%. There were scattered clouds at a height of 2438 meters (8000 feet), scattered clouds at a height of 3658 meters (12000 feet) and broken clouds at a height of 6096 meters (20000 feet). The visibility was 16.1 kilometers (10.0 miles).
And, clicking on Thule gives:
July 25, 2009, weather report for
THULE, GREENLAND
Weather report as of 3 minutes ago (00:55 UTC):
The wind was calm in Thule, Greenland. The temperature was 12 degrees Celsius (54 degrees Fahrenheit). Air pressure was 1,018 hPa (30.05 inHg). Relative humidity was 40.5%. The sky was clear. The visibility was >11.3 kilometers (>7 miles).
There is a particular spot of ice between Northern Ellesmere and Greenland , a rock steady sheet for as long as I can remember, disintegrating. This is new, the last remnants of steady ice are disappearing in front of our eyes. #318, same in Canada, except distances from North and South range about 2000 miles.
http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png
Re:319 I’ve got my money on 2009 by a nose, I think now it’s squeak in under the radar, it’s finally found it’s legs and is romping home. lol!
But jokes aside this shows that the ice albedo momentum is building every year despite 2009 not being an outstandingly hot year.
Tenney Naumer, Reur 323, you reported in part:
That sounds a bit like some weather we have had in Melbourne (Australia) recently.
However, compare Greenland to the current Wiki’ entry concerning temperatures in Antarctica:
The lowest temperature ever recorded in nature on Earth was −89.2°C (−128.6°F) recorded on Thursday, July 21, 1983 at Vostok Station. For comparison, this is 11 °C colder than subliming dry ice. The highest temperature ever recorded in Antarctica was 14.6°C (58.3°F) in two places, Hope Bay and Vanda Station, on January 5, 1974.
The mean annual temperature of the interior is −57°C (−70°F). The coast is warmer. Monthly means at McMurdo Station range from −28°C (−18.4°F) in August to −3°C (26.6°F) in January. At the South Pole, the highest temperature recorded was −14°C (7°F). Along the Antarctic Peninsula, temperatures as high as 15°C (59°F) have been recorded, though the summer temperature is usually around 2°C (36°F).
Severe low temperatures vary with latitude, elevation, and distance from the ocean. East Antarctica is colder than West Antarctica because of its higher elevation. The Antarctic Peninsula has the most moderate climate. Higher temperatures occur in January along the coast and average slightly below freezing.
In my engineering/geological comments to others previously here, concerning ice SHELF mechanical failures in Antarctica, there have been various vague counter-references to massive melt ponds and moulins, (as reported in Greenland?), as being causal to those mechanical failures in Antarctica. However, I’ve pointed out that the Greenland ice SHEET is a different animal to ice SHELVES in Antarctica, for instance; it is substantially geologically captured in a basin, and not subjected to tidal heaving etc. (and of course, Antarctica is much colder)
Are you able to give me a response to some of the issues I’ve raised, (that have been avoided or derided by others), such as the decadal nature of hinging failure, and for example the apparent absence of melt water in the two summer aerial photos of the Filchner chasms in 1957.
Oh, incidentally, to help in understanding, floating ice SHELVES are fed by Glaciers/ice SHEETS which creep seaward under gravitational force. Consequently, the initial hinging failure lines are progressively advanced seaward and the resulting canyons may become massive over time.
Wayne, could you tell what do you think of the effect this breakup has? I’d expect the additional cold from this ice to melt and sink once it gets to Atlantic, and have no effect on the European winter, but I haven’t seen 10 by 10 km ice bergs melt… they only drift away in the Baltic coasts…
Wayne@324: do you mean the Lincoln Sea, about 83N, 57W? That came apart very rapdily after the “ice bridge” at the north end of the Nares Strait broke up a couple of weeks ago.
Rod B #235,236: the tides is something I have actually published on a long time ago: see the introduction (first page) of
http://www.springerlink.com/content/h7674t3q42453mj4/
equations 1-4. The tidal potential is in practice exactly proportional to d^-3. Only for objects a lot closer than the Moon this would be different. This is for the tidal potential (the tidal deviation of ideal sea level) but is the same for tidal force (its gradient).
BTW there is no difference between the direct torque effect and the friction effect: the tidal bulge lags Sun and Moon because of friction. And that again makes the torque nonzero. I don’t understand (and don’t even recognise as coherent) your “explanation” in #235. You do get the ratio between Sun and Moon right though, to end on a positive note.
re: #322
Dear dave p,
It seems pretty clear that this year Greenland will have an extraordinary mass balance loss, but those data will not come out until September, probably, or even later. I will be posting updates on my blog as usual. For everything you wanted to know about the melt on Greenland but were afraid to ask see here:
http://climatechangepsychology.blogspot.com/search/label/Greenland%20ice%20melt
re: #318
Dear jyyh,
Hammerfest in the extreme north of Norway has been very warm. In 2007, it was also very hot up there. It was in the 70s there yesterday, I believe.
You can get the temps around the Arctic at this site:
http://www.athropolis.com/map2.htm
July 26, 2009, weather report for HAMMERFEST, NORWAY
Weather report as of 15 minutes ago (12:50 UTC):
The wind was blowing at a speed of 7.7 meters per second (17.3 miles per hour) from Northeast in Hammerfest, Norway. The temperature was 20 degrees Celsius (68 degrees Fahrenheit). Air pressure was 1,012 hPa (29.88 inHg). Relative humidity was 52.5%. There are no clouds below 1,524 meters (5,000 feet). The visibility was >10 kilometers (>6.2 miles).
re: #324
Dear Wayne,
The multi-year ice in the location to the north of Ellesmere and Greenland all moved east last year. What is there now is what came from the west last year before it all froze solid again. The multi-year ice is at a very low percent of total ice now, as I am sure you know. But it is all much thinner. In that particular location, it began to crack up in early April. Again, it has moved to the east. Nares Strait didn’t even freeze up properly this past winter.
The Canadian Met Office has a very good overview of what is going on there:
http://tinyurl.com/nares-ice-arch-2009
re: #326
Dear BobFJ,
I am afraid that all of your questions are way out of my area of expertise.
In fact, I just look at Greenland as if it were one very large snowcone on a hot summer’s day — to my unscientific eyes, that is how it is behaving.
#324, Terry, Its highly likely that ice has moved East or West at that location, but in the past it was the most stable area, where as buoys didn’t move fast, but the main point is that the entire area is melting, something I never seen before, Usually only a small section remained open Just North of the Strait between Greenland and Ellesmere… #324, Nick, the effects of this is highly likely much quicker flow of the entire ice pack, since a stable ice sheet “anchor” is no longer present.
Bob, you’ll need to either get out of your chair and go to the library, or pay the publisher for full copies, for most of the current work in the area you ask about. A few more examples just to encourage you to read in the field in which you want to shine:
http://www.esajournals.org/doi/abs/10.1890/07-1941.1
Jeff W. Higdon, Steven H. Ferguson (2009) Loss of Arctic sea ice causing punctuated change in sightings of killer whales (Orcinus orca) over the past century. Ecological Applications: Vol. 19, No. 5, pp. 1365-1375.
doi: 10.1890/07-1941.1
http://ams.confex.com/ams/10POLAR/techprogram/session_22845.htm
10th Conference on Polar Meteorology and Oceanography
Session 16 Atmosphere-Ocean-Sea Ice Interactions
http://linkinghub.elsevier.com/retrieve/pii/S0012821X08007887
T Scambos, HA Fricker, CC Liu, J Bohlander, … – Earth and Planetary Science Letters, 2009
… Ice shelf disintegration by plate bending and hydro-fracture: Satellite observations and model results of the 2008 Wilkins ice shelf break-ups. …
http://journals.cambridge.org/action/displayAbstract?aid=5856680
Antarctic Science
doi:10.1017/S0954102009990137
Published online by Cambridge University Press 16 Jun 2009 ($20.00)
Review — Ice sheet mass balance and sea level
http://www.guardian.co.uk/environment/2009/jul/26/climate-change-obama-administration
Unbelievable, unfathomable, that Global Warming pictures of the Arctic were censured top secret… As if the Arctic itself should be cut off from the rest of the world. How utterly deprived!
It seems possible that northern melt is causing cooler weather to the south. The stuff about Hudson Bay seems to be another instance, like here in Boston. Of course we’ll have to wait and see.
(My family calls this an “Anderson check”, asking a question and since no one actually contradicted my idea (too vague to call a hypothesis), making a statement.)
#334 Sorry Tenney, not Terry , me bad.
#337 Susan, its the clouds coinciding with El-Nino, I elaborate more on my website.
In Montreal, elders are acknowledging the cloudiest summer ever.
Dear Wayne,
Well, we know the ice is thinner, and we know it is stormier up there these days, and we know that the water underneath is warmer, so it only makes sense that a bunch flowed out and then was not replaced.
Last year when I commented that the ice was flowing out faster, someone jumped all over me, but this is what I found on the speed:
Journal of Geophysical Research, 114, C05013; doi: 10.1029/2008JC005066.
Positive trend in the mean speed and deformation rate of Arctic sea ice, 1979–2007
P. Rampal (Laboratoire de Glaciologie et Géophysique de l’Environnement, UMR5183, Université Joseph Fourier, CNRS, Saint Martin d’Hères, and Laboratoire de Géophysique Interne et Tectonophysique, UMR5559, Université de Savoie, CNRS, Le Bourget du Lac, France), J. Weiss (Laboratoire de Glaciologie et Géophysique de l’Environnement, UMR5183, Université Joseph Fourier, CNRS, Saint Martin d’Hères, France), and D. Marsan (Laboratoire de Géophysique Interne et Tectonophysique, UMR5559, Université de Savoie, CNRS, Le Bourget du Lac, France)
(Received 1 August 2008, accepted 11 March 2009, published 14 May 2009.)
Abstract
Using buoy data from the International Arctic Buoy Program, we found that the sea ice mean speed has substantially increased over the last 29 years (+17% per decade for winter and +8.5% for summer). A strong seasonal dependence of the mean speed is also revealed, with a maximum in October and a minimum in April. The sea ice mean strain rate also increased significantly over the period (+51% per decade for winter and +52% for summer). We check that these increases in both sea ice mean speed and deformation rate are unlikely to be consequences of a stronger atmospheric forcing. Instead, they suggest that sea ice kinematics play a fundamental role in the albedo feedback loop and sea ice decline: increasing deformation means stronger fracturing, hence more lead opening, and therefore a decreasing albedo. This accelerates sea ice thinning in summer and delays refreezing in early winter, therefore decreasing the mechanical strength of the cover and allowing even more fracturing, larger drifting speed and deformation, and possibly a faster export of sea ice through the Fram Strait. The September minimum sea ice extent of 2007 might be a good illustration of this interplay between sea ice deformation and sea ice shrinking, as we found that for both winter 2007 and summer 2007 exceptionally large deformation rates affected the Arctic sea ice cover.
Link to abstract: http://www.agu.org/pubs/crossref/2009/2008JC005066.shtml
Actually, Wayne, that Nares Strait ice arch had big cracks in it last year, if I can find a photo, I will post it on my blog for you.
hmmm, permit me to correct myself. Last year, I commented that most of the multi-year ice had moved out, and someone jumped on me by saying that it was not possible because the ice couldn’t move that fast. I was looking at the satellite images every day, and you could see it was going at a pretty fast click.
Now we know that there is hardly any decent mult-year ice left:
“New NASA Satellite Survey Reveals Dramatic Arctic Sea Ice Thinning”
http://www.nasa.gov/topics/earth/features/icesat-20090707.html
N.B. That link takes forever to open, but has tons of data and charts.
#341 Dear Tenney, I agree, melting doesn’t happen without thinner ice, I appreciate your links as well, it is nevertheless very significant area of melting. Usually there is an arcof open water in the Robeson channel as per picture:
http://bprc.osu.edu/~jbox/img/polynya/2009.086_location_map_sm.jpg
It varied in size and dimensions over the years. I surmise it was due to very steady ice, as confirmed by buoys. The area of ice Northwards of Robeson is melting dramatically now.
Not far away Greenland Glacier is melting dramatically as well,
http://www.meltfactor.org/blog/?cat=1
Which merely again confirms that chaos from melting has started a while ago.
Dear Tenney, Fortunately there is a link showing a recent picture of the melting and cracking…
http://www.meltfactor.org/blog/?p=66
Gee, looks like I am hogging the comments section, sorry.
But, be that as it may, is anyone willing to call the Northeast Passage open or would that be premature just based on this graphic (I had to post it to my own blog because those images are changed daily — hit the page down key a few times to get down the page to the post):
http://climatechangepsychology.blogspot.com/2009/07/did-northeast-passage-open-today-july.html
The people here:
http://peakoil.com/environment/record-sea-ice-loss-in-arctic-2009-t49665-585.html
are saying that the Arctic ice cap is now detached and free floating. Is this what others are seeing? Has this happened before? Is it significant for predicting rate of melt?
[Response: It’s always free floating… This is nothing extra to be concerned about. – Gavin]
30 James wonders, “if less sea-ice in the Arctic might not let the Gulf Stream penetrate into – and thus spend itself – the Arctic Ocean.”
It would make a rather good heat exchanger. The North Atlantic MOC gets its thrust from wind-blown cold and salty water. Move the deep water formation locations a few hundred miles northward and things get interesting. I’m sure someone here could speak to the odds.
44 Steve ponders, “it seems to me that in terms of albedo, it’s the late spring / early summer coverage that’s important (when the sun is highest).”
Late spring sea ice extent is very consistent. This will likely change as winters get shorter, ice gets thinner, and warm waters penetrate the Arctic further. As melt season gets up to steam earlier, the albedo effect will come more into play and an ice-free minimum will result quite soon.
Still haven’t changed my guess on minimum extent – 4.0 to 4.5 million km. Look at the concentration maps. There’s large areas with concentrations below 65%. That’s a lot of open water; kind of like the slush left over after the cubes in your iced tea are almost all gone. Add in that Hudson Bay has some remnants to melt and it looks like the melt season has plenty of steam left.
“This will likely change as winters get shorter, ice gets thinner, and warm waters penetrate the Arctic further.”
Why will winters get shorter, Richard?
The onset of winter depends on the orbit of the earth, not the temperature. And CO2 doesn’t affect the orbit of the earth…
John P. Reisman, Rod B, Kevin McKinney, & Manacker,
Further my 320, Mark Serreze, newly director of NSIDC is the apparent author of this article:
http://www.arctic.noaa.gov/essay_serreze.html
Please study the following graphic comparison of its figure 1, with some other information in Wikipedia:
http://farm4.static.flickr.com/3496/3760617259_68b468d807_o.jpg
I’d be interested in your comments, and also from anyone with a rational consideration.
While strictly true, the reality is that we pitiful humans in large parts of the temperate zone think that winter begins when winterish weather arrives, typically in November here in PDX.
I suspect the “shorter winters” comment was made in the weatherish, not orbital, sense. The date of the summer minimum is moving to later in september than in the past (on average) despite their being no change in the nice, neat, definition of “winter” based on earth’s orbit ’round the sun. If it makes you feel better to call it a “shorter freezing season” rather than “shorter winter”, cool – but it doesn’t really add anything to the discussion …