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An icy retreat

Filed under: — group @ 26 July 2010 - (Deutsch) (Español)

Guest Commentary by Dirk Notz, MPI Hamburg

It’s almost routine by now: Every summer, many of those interested in climate change check again and again the latest data on sea-ice evolution in the Arctic. Such data are for example available on a daily basis from the US National Snow and Ice Data Center. And again and again in early summer the question arises whether the most recent trend in sea-ice extent might lead to a new record minimum, with a sea-ice cover that will be smaller than that in the record summer of 2007.

However, before looking at the possible future evolution of Arctic sea ice in more detail, it might be a good idea to briefly re-capitulate some events of the previous winter, because some of those are quite relevant for the current state of the sea-ice cover. The winter 2009/2010 will be remembered by many people in Europe (and not only there) as particularly cold, with lots of snow and ice. Not least because of the sustained cold, some began to wonder if global warming indeed was real.

Such questioning of global warming based on a regional cold period of course neglects the crucial difference between weather and climate, with the former being the only thing that we as individuals will ever be able to experience first hand. A single regional cold spell has not a lot to do with climate – let alone with global climate. This becomes quite obvious if one instead considers the mean temperature of the entire globe during the last 12 months: this period was, according to the GISS data, the warmest 12-month period since the beginning of the records 130 years ago. Regarding sea ice, it was particularly important that temperatures in parts of the Arctic were well above average for most of the winter. This was directly experienced by some members of our working group during a field experiment at the West Coast of Greenland.


Fig. 1: Temperature anomaly at 1000 hPa during the first half of January 2010 with respect to the period 1968-1996. Warm anomalies in the Arctic and cold anomalies in Northern Europe and parts of North America are clearly visible.

The initial plan of this field experiment was to study the growth and decay of sea ice in great detail throughout an entire winter. In particular, we wanted to focus on the evolution of very young sea ice that had just formed from open water. Therefore, we wanted to start our measurements just before initial ice formation, which usually takes place in mid-November, at least according to past experience of the local Greenlandic population. Hence, we traveled to our measuring site close to the Greenlandic settlement of Upernavik in early November to put out our measuring buoys. We were hoping that ice formation would start shortly after we had put out the instruments such that they were protected from storms and waves. However, with temperatures that were often more than 10°C above the long-term mean, sea ice was nowhere to be seen. Even in January, there were days on end with above 0°C temperature and heavy rain fall. Finally, in February a stable ice cover formed, which of course remained relatively thin and which hence had melted completely by mid May.

The fact that it was sometimes warmer at our measurement site at the West Coast of Greenland than it was in Central Europe at the same time surprised us quite a bit. However, some recent studies indicate that such a distribution of relatively high temperature in parts of the Arctic and relatively low temperature in Northern and Central Europe and parts of the US might become somewhat more wide-spread in the future. While the Arctic has always shown large internal variability that lead to large-scale shifts in weather patterns, in the future the ongoing retreat of Arctic sea ice might cause those weather patterns to occur more often that allow for Northerly winds to bring cold air from the Arctic to the mid-latitudes. Hence, it is quite possible that because of the retreat of Arctic sea ice, some smaller parts of the Northern Hemisphere will experience pronounced cold spells during winter every now and then. The mean temperature of the Northern Hemisphere will nevertheless increase further, and the export of cold air from the Arctic of course leads to warm anomalies there.


Fig.2: Evolution of Arctic sea-ice extent from September 2009 until mid May 2010. The blue line denotes the mean extent from 1979 until 2000, while the shaded region denotes the variability during that time (± 2 standard deviations)

But let’s return to the evolution of Arctic sea ice. Because of relatively high temperatures, Arctic sea-ice extent remained well below the long-term mean for most of the preceding winter. However, in March temperatures suddenly dropped for a couple of weeks, in particular in parts of the Barents Sea and in parts of the Beaufort Sea. This in turn lead to the formation of a thin ice cover in these regions, which caused a marked increase in observed sea-ice extent. For the measurement of this extent, it doesn’t matter at all how thick the ice is: any ice, however thin, contributes to sea-ice extent. Therefore, only considering a possible “recovery” of just the extent of Arctic sea ice always remains somewhat superficial, since sea-ice extent contains no information on the thickness of the ice. A much more useful measure for the state of Arctic sea ice is therefore the total sea-ice volume. However, for its estimation one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past. While this will hopefully change in the future because of the successful launch of the Cryosat 2 satellite a couple of weeks ago, at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.


Fig.3: Evolution of Arctic sea-ice extent since April 2010 in comparison to 2007 and 2009. The blue line denotes the mean extent from 1979 until 2000, while the shaded region denotes the variability during that time (± 2 standard deviations)

Because of the very low thickness of much of the Arctic sea ice, it wasn’t too surprising that at the end of the winter, sea-ice extent decreased rapidly. This rapid loss lead up to the lowest June sea-ice extent since the beginning of reliable observations. After this rapid loss of the very thin ice that had formed late in winter, the retreat slowed down substantially but the ice extent remained well below the long-term mean. Currently, the ice covers an area that is slightly larger than the extent in late July of the record year 2007. However, this does not really allow for any reliable projections regarding the future evolution of Arctic sea ice in the weeks to come.

The reason for this is mostly that sea ice in the Arctic has become very thin. Hence, in contrast to the much thicker ice of past decades, the ice now reacts very quickly and very sensitively to the weather patterns that are predominant during a certain summer. This currently limits the predictability of sea-ice extent significantly. For example, in 2007 a relatively stable high-pressure system formed above the Beaufort sea, towards the north of North America, leading to rapid melting of sea ice there. If again such stable high pressure system forms in the Arctic throughout the coming weeks, we might well experience a sea-ice minimum that is below the record minimum as observed in 2007. However, if the summer should turn out to be colder than during the previous years, a sea-ice minimum similar to that observed in 2009 would not be too surprising. Hence, at the moment all that remains is to wait – and to check again and again the latest data of Arctic sea-ice extent.


Fig.4: Arctic sea-ice extent on June 28July 20, 2010. The orange line denotes the mean extent on June 28July 20 from 1979 until 2000.

Dirk Notz is head of the research group “Sea ice in the Earth System” at the Max-Planck-Institute for Meteorology in Hamburg.

The original version of this article was published in German at KlimaLounge

References:

Honda, M., J. Inoue, and S. Yamane (2009), Influence of low Arctic sea-ice minima on anomalously cold Eurasian winters, Geophys. Res. Lett., 36, L08707, doi:10.1029/2008GL037079.

Notz, D. The future of ice sheets and sea ice: Between reversible retreat and unstoppable loss. Proc. Nat. Ac. Sci. 106(49), 20590–20595, doi:10.1073/pnas.0902356106 (2009).

Polyakov, I. V., and M. A. Johnson (2000), Arctic decadal and interdecadal variability, Geophys. Res. Lett., 27(24), 4097–4100.

Credits:
Figure 1: NOAA ESRL Physics Science division

Figures 2-4: Data: NSIDC, Graphics: D. Notz.


175 Responses to “An icy retreat”

  1. 1

    I wonder if someone can help with a query here. This article and most of the other articles and comments I can find on Arctic sea ice concentrate very much on sea ice extent. But towards the end of the article the author mentions sea ice thickness, but only in passing. Presumably the actual amount of ice up there is measured by multiplying extent by thickness. I would have thought that the amount of ice was more important than either extent or thickness – but maybe I am missing something. So why does nearly everyone talk about extent? Is it easier to measure? Or is there a deeper (forgive the pun) reason?

  2. 2
    Paul says:

    That ginormous temperature anomaly over Greenland makes me wonder what the melt rates are there this year.

  3. 3
    Mike says:

    #1 You are missing this (from the text):

    “A much more useful measure for the state of Arctic sea ice is therefore the total sea-ice volume. However, for its estimation one additionally requires information on the overall distribution of ice thickness, which we have not been able to measure routinely in the past. While this will hopefully change in the future because of the successful launch of the Cryosat 2 satellite a couple of weeks ago, at the moment we unfortunately must rely on judging the current state of the Arctic sea-ice cover mostly by its extent.”

  4. 4
    Lord Soth says:

    Thanks for the interesting article Dirk.

    I have really noticed how the day to day weather is having a dramatic impact on sea ice extent. Instead of depending on climate issues, we are looking at the right weather conditions for three to four months of the year, to make the knockout punch on the arctic ice cap.

    2008 has proven to us that we can have significant ice loss in August. 2009 has also proven that unfavorable weather can turn a contender into a dud for sea ice loss, based on extent.

    The important thing to remember is that volume is going down year after year, and 2009 despite its lackluster extent, did beat 2007 and 2008 for lowest volume. And it appears that 2010 will score a knockout punch in regard to minimun volume.

    I would love to get some detailed info on cryosat-2, such as how long would it take to get full coverage of the arctic (even north of 80) for sea ice volume. Are we talking daily, weekly, monthly or seasonal post processing for sea ice volume graphs ?

  5. 5
    jyyh says:

    No deeper reason needed, as it’s somewhat more difficult to measure anything from orbit than in location. On exchange one gets a large coverage for observations (though not a full one, ask people who know orbitals why is that) Volume is better and harder to measure than extent, that can be measured from orbit quite easily (well people doing that might disagree, the clouds are quite hard to discount sometimes) from refractive properties of ice, but volume isn’t the absolutely optimal parameter either, but for better one one would need also the consistency of the ice (how porous it is) and the core temperature on the onset of melting (which is very hard to measure). F.e. ice that forms when slush ices over is much more porous than the clear ice from the freezer. For volume calculations one needs to know f.e. the underlying ocean temperatures quite well(as ~90% of ice is under water, hence there are buoys sailing in there.

  6. 6
    mauri pelto says:

    The volume is simply not directly measured. The volume measuring system has been well validated and the results demonstrated as robust, but it has still not been direct. The Polar Science Center at U of Washington provides the daily volume updates, PSC. The extent is visible to all of us in daily imagery and the ability to observe the changes is fascinating take a look at the nearly daily reporting and new imagery provided by Neven

  7. 7
    Rosemary says:

    Thanks for the clear, accessible and engaging article, Dirk!

  8. 8

    #1 Rupert Matthews

    Extent is pretty easy to see and volume or thickness is not as obvious. But simply multiplying the extent by the thickness does not get you where you want to go.

    Reason being, the thickness is different in different areas of the Arctic.

    I have been testing a new page on OSS for Current Climate Conditions for about a month. And though I’m not done making sure everything is working yet, you might as well take a look

    http://www.ossfoundation.us/the-leading-edge/projects/environment/global-warming/current-climate-conditions

    There will be an underlying section in the future to provide more detail and more data products. The Cryo section, at the moment, has the basics, extent, volume, flow and even some forecasting, in case you drive a submarine?


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future – climatelobby.com
    L

  9. 9
    Nagraj Adve says:

    I believe that Arctic sea ice has thinned by an average of roughly 40 per cent over the last few decades, from an average of ten feet to six feet. What does more current data suggest?
    Nagraj Adve

  10. 10
    Eli Rabett says:

    The issue with climate studies is not what you got but what you had. Since no one was really doing appropriate measurements 30 or more years ago, you take the records that still exist, dig up and drill new proxys and try and figure what the various things you were interested in were. Same with ice volume and even extent back before the satellite era.

  11. 11
    Walt Bennett says:

    What catches my eye is the temp anomaly. Plus ten on a sustained basis?

    And surely we admit that we are still in the early stages of the warming.

    Sustained temps above 0*C in total darnkess at the top of the planet?

    With surely much more warming to come?

    Dirk, I’m looking upon the field science and the honest observations of those such as you who spend significant time there, because to be honest the men in computer labs have not succeeded in delivering the message.

    Which is unfortunate because we all agree that “by the time you can see it, it’s just too late.”

    Would you concur with my observation that the arctic is well on its way to becoming substantially warmer for a very long period of time?

    In other words, this trend cannot turn around in time scales meaningful to this discussion due to the inertia of its own accelerating positive feedback loop.

    Would you concur with that?

  12. 12
    wilt says:

    July is the month when the average temperature in the Arctic is at its maximum. Up till now in July, the daily loss of arctic sea ice has been about 60,000 square kilometers, as compared to about 80,000 in 2008 and more than 100,000 in 2009 or the ‘record year’ 2007. I don’t understand how this would be compatible with the ‘very thin ice’ suggested by Dirk Notz.
    http://wattsupwiththat.com/2010/07/25/sea-ice-news-15/

  13. 13

    RE

    However, some recent studies indicate that such a distribution of relatively high temperature in parts of the Arctic and relatively low temperature in Northern and Central Europe and parts of the US might become somewhat more wide-spread in the future.

    Drats! I was sort of hoping that the one thin silver thread (no lining, of course) in this AGW debacle/catasstophe would be no more freezes here in the lower Rio Grande Valley, so our tropic plants and garden veggies wouldn’t freeze, as they did this past winter several times in Dec and Jan. Which is unusal, since we only get a killing freeze here maybe once (if twice, then within a few days) about every 5 to 10 years.

    Are there any sources or studies on this, that the strongly negative arctic oscillation (I think that’s what they call it) may become more common in the future?

  14. 14
    Thomas says:

    We have three easy to understand measures for sea ice. Extent is the most widely used, but a pixel (or grid cell) is counted as ice covered if the estimation of cover is 15% or more. Obviously a system with say 10 cells at 16% coverage has less ice than a system with 5 cells at 100% coverage, so extent can give a misleading indication of ice area. Area would be an estimation of the actual area covered. I think area is probably more relevant for measuring ice/albedo, and ice-atmosheric interactions. I doubt area is that straightforward to estimate, otherwise we would be seeing routine reports of it. Finally you have ice volume.

  15. 15
    chris says:

    It would be really helpful to have some expert insight into the contribution of the AMO to the very high current Arctic temperature anomalies. There’s no question that the dominant contribution to warming is global warming (!); however to what extent are the extreme effects in the Arctic (which are greater than projected from models) due to a superposition of global warming and enhanced N. Atlantic heat arising from the positive phase of the AMO?

    Earlier studies (e.g. Trenberth and Shea, 2006) suggested that once the global warming effect on SST was removed from the AMO variability, there wasn’t actually very much of a contribution from the AMO (around 0.1 oC to SST in the tropical N. Atlantic in 2005). However more recent analyses support a stronger contribution from the AMO to high sea surface temperatures in the N. Atlantic (e.g. Chylek et al, 2009; Enfield and Cid-Serrano, 2010; Polyakov et al. 2010).

    This seems like an important issue for properly understanding events in the Arctic.

    Trenberth, KE and Shea P (2006) Atlantic hurricanes and natural variability in 2005, Geophys. Res. Lett. 33, L12704
    http://www.agu.org/journals/ABS/2006/2006GL026894.shtml

    Chylek P et al. (2009) Arctic air temperature change amplification and the Atlantic Multidecadal Oscillation, Geophys. Res. Lett. 36, L14801.
    http://www.agu.org/journals/ABS/2009/2009GL038777.shtml

    Enfield DB and Cid-Serrano L (2010) Secular and multidecadal warmings in the North Atlantic and their relationships with major hurricane activity, Int. J. Climatol. 30, 174-184.
    http://www3.interscience.wiley.com/journal/122261152/abstract?CRETRY=1&SRETRY=0

    Polyakov IV et al. (2010) North Atlantic warming: patterns of long-term trend and multidecadal variability, Climate Dyn. 34, 439-457.
    http://www.springerlink.com/content/8415720180780275/

  16. 16

    Question: I recently discovered the North Pole Cam. It’s fascinating beyond belief to me that I can spend a part of my day basically watching the north pole melt in real time using graphs, animated graphics, and even actual north pole time lapse footage. It fascinating and frightening that it’s happening, and it’s fascinating that I can watch. 20 years ago it was amazing to watch the first Gulf war in real time. Now it’s the Arctic.

    The world we are blessed to live in (at least for the moment, if we don’t throw it all away with arrogance and collective stupidity) is truly amazing.

    Looking at previous years of North Pole time lapse footage, it appears that ice begins to refreeze by the end of July or middle of August. Is this true, or just a mistaken impression I have from watching the footage?

    If so, the implication would be that while extent would continue to decrease from the edges, most chances of a very low final minimum would be greatly reduced after July.

    Also, that refers to the surface and presumably surface temperatures. What’s going on underneath? What it the sea water temperature at the actual pole? Is it causing melting from the bottom up at this time of year, or freezing from underneath?

  17. 17
    NeilT says:

    Over the years I have noticed that Scientists simply don’t want to get into the Extent v Volume v Area debate. Partially because the data for Extent is long term and reliable, partly because it is extremely difficult to calculate volume as the recent IPY webcast showed. When we actually went there and looked at the “old” ice it simply wasn’t there. No matter what the satellites reported.

    Of course there is also the problem that Extent includes areas of sea that are 85% water, which would effectively kill any quality volume assessment using Extent. For that you would have to use Area and the Area figures have been deemed to be less accurate.

    I am much more interested in the first half of the article. At the beginning it talks about the changes in winter. Whilst summer is more “sexy” in terms of reporting the loss of ice, it is the winter (I believe), which is more indicative of the changing climate forced by emissions.

    In the last 2 years much has been said about the “near misses” to the 2007 low. Yet almost nothing (in relative terms), has been said about the fact that winters are growing shorter and warmer. At the same time the ice cycle is growing shorter and the open water cycle is growing longer.

    Whilst it is no surprise, to those who doubt, that we don’t break any records in summer ice melt, in the middle of one of the deepest solar minimums since solar records began; it should be of huge surprise, to those same doubters, that the winters (in the middle of the same solar minimum), are so warm with so little ice.

    If we look at the Sunspots for solar cycles and map it against the , it is no surprise that the breakup is so early in 2002 – 2004. What is a surprise, though, is the W/Msq delivered in 2007 (ok the weather was good but the solar output was low) and the early breakup then.

    However if we look at the ice low in 2005, the winter/spring low in 2006/2007 and the near miss in summer 2006 plus the ever decreasing volume of ice, the lengthening Autumn ice free season and the ever increasing winter temperatures; the 2007 result should not really be a surprise. Either spring, summer, autumn or winter.

    So really something is forcing a change in the arctic which is making it warmer, not just in the summer, not just because of albedo (no sun in the winter although the water is giving back it’s heat), but generally over the whole year. Also not just one year but year after year after year; solar high or solar low.

    Personally that’s my definition of climate change but I do understand we can’t say that until we have tracked it for a few decades. BUT will we even have any summer ice there in a few decades?

  18. 18
    Edward Greisch says:

    16 Bob (Sphaerica): What is the URL of the North Pole Cam?

    Every decrease in sea ice means we are closer to BP drilling in the Arctic Ocean. An oil well there would be another bad reason to not fight GW.

  19. 19
    Greg Robie says:

    I’m one of those who watches the extent on a daily basis during the melt season and, more often than not, also do so year around. This year I added http://arctic.atmos.uiuc.edu/cryosphere/ and http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm to my daily ritual of checking the NSIDC graph http://nsidc.org/data/seaice_index/images/daily_images/N_timeseries.png and NOAA’s National Ice Center’s 31 day extent animation http://www.natice.noaa.gov/ims/loop/ak-1mo-loop.html (when the “Near real-time Arctic site was taken down for a while http://quartet.narod.ru/arctic.html ). I find all of these different representations of data on Arctic ice helpful for thinking about the import of the occasional story and blog post about the changes unfolding in the Arctic.

    Latent heat factors strongly into what one needs to watch for/think about, both as the ice reforms in winter, and, as it melts in the summer. This post’s point about the delay in ice formation off Greenland last winter is an example of this. The same will be true for the ice melting this summer: becasue all we can measure on an Arctic-wide basis is the extent, there will be a lag before the extent decline will confirm the loss of volume the Arctic ice cap has experienced due to global warming—particularly in the past decade.

    This year the perimeters of the Arctic ice cap seem to be melting more or less as per the new normal of the last decade. What does appear to be different this year, and is indicative of the lack of volume in the remaining Arctic ice, is the “flows” of 60% – 80% ice extent through the center of the ice cap that the Cryosphere Today site displays. Comparing what is being observed this year with 2007, it almost constitutes a sea change. And this has an impact on the prediction I made here back in May—and posted a graph of on the solstice: http://home.roadrunner.com/~robie/opento/welcome.html .

    I created the curve using Photoshop and the 1979-2000 average. That choice has me as wrong as I currently am because of the role latent heat differently plays in todays ice extent change dynamics depending on whether the melt is occurring at the edges or internally to the ice cap. What happens, on average, at the ice cap’s edges does not apply to how the thermodynamics will play out at the center of the ice cap. In the center of the ice cap latent heat and ice extent decline will interplay over time to yield yet another new normal. Learning from my less-than-completely-thought-through prediction, and as best I can guess now, the new shape of the ice extent decline will be defined by the thermal dynamics created by the eventual impact shortening daylight will have on solar incidence’s contribution the change of phase in an area where ice extent has rarely dropped below 90% in the past.

    The current slope of the ice extent curve is tracking last year’s. This is descriptive of what happens at the ice cap’s perimeter. If the percent of ice extent continues to lower in the ice cap’s center, as it has so far in the melt season, the slope of the curve could steepen significantly in the next 6 weeks. Surface winds will also play a major role in what is observed. Regardless, the amount of open water that is exposed will delay the reformation at the start of the winter freeze. The more diffuse that open water the less its impact (this year); the more concentrated it is, the greater (this and future years). Either way, this year should begin to define a new melt pattern that will be defined the curve of the ice extent loss that leads to late summers with 90% sea ice loss. Such is our near, and maybe very near, future.

    The confusion that is possible when conflating extent and volume as one thinks/feels about future behavior of a substance with the latent heat that water has re its solid/liquid change of phase, can, as it did to me with my choice to use the curve of the 1979-2000 average, lead to too-quick-thinking. Such thinking and its predictions can be more a reflection on ones limited mental capacity and the role motivated reasoning plays in obscuring contradictions; complexity; (and ironically) simple physics and math!

  20. 20

    Just a quick note on the temp anomaly over Greenland. The image states it is first half of January, so i don’t think it sustained for very long.

    Here’s the NCDC/NOAA chart for the month of January

    http://www.ncdc.noaa.gov/sotc/?report=global&year=2010&month=1&submitted=Get+Report

    Not to belittle the concern however.

    I forgot about the north pole cams, I used to watch those too.

    I just loaded them in the Cryo section with source links

    http://www.ossfoundation.us/projects/environment/global-warming/current-climate-conditions


    A Climate Minute: The Natural CycleThe Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future – climatelobby.com
    Learn the Issue & Sign the Petition

  21. 21

    18 (Edward),

    North Pole Cam

    Amazing beyond belief. Truly. I live in a wonderful age. I can’t believe I didn’t become a scientist myself. I need a do over on life (not really, but you know what I mean).

  22. 22
    NeilT says:

    I knew I shouldn’t have tried to use html….. :-(

    solar cycle sunspots courtesy of solarcycle24 and the hathaway prediction
    http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif

    Barrow sea ice breakup courtesy of the Alaska Uni sea ice group

    http://seaice.alaska.edu/gi/observatories/barrow_breakup/Melt-out-20100709.png

  23. 23
    Pete Dunkelberg says:

    Wilt # 12

    How can reality not be consistent with itself?

    The arctic ice is not simply uniformly thin. It is broken with lots of gaps. Whether an area becomes clear of ice depends very much on the wind blowing the ice elsewhere. The net effect depends on whether the ice has been blown to a warmer spot. Look at the graphs provided above, or look at Arctic Sea Ice News daily.

    Around the end of June the wind shifted and the daily reduction of ice extent fell way off. Lately though the graph is running about parallel to the 2007 line.

    The daily Arctic Oscillation graph gives you a first approximation to winds in the Arctic. What it indicates just now is quite modest overall wind in the Arctic.

    What will Arctic weather be for the rest of this summer? The answer is blowing in the wind. But no matter which way the wind blows, CO2 is in the air intercepting long wave radiation.

  24. 24

    12 (wilt),

    What I have gleaned from reading, watching, and keeping an open mind is that we do not have any true way of measuring ice in the Arctic (although Cryosat 2 should get us a lot closer). Extent, area, everything is just a proxy for the amount of total ice in the Arctic, and they are all limited proxies… and even then, it’s just a measurement, not an understanding of a complex system. Extent doesn’t tell you how thick the ice is, or how much ice is really there. Area doesn’t tell you how thick it is, either, and is only a gross estimate of actual area. Any single number doesn’t really tell you what is really there, or what is going to happen.

    In each case, you are looking at wide expanses of ocean with varying amounts of floating ice interspersed. Or, you are looking at sheets of seemingly solid ice of unknown depth and consistency (is it solid ice, or packed snow, or ice riddled with fissures and pockets of melted water?).

    In addition, it is constantly moving. Now you see it, now you don’t. Winds and currents move it around, dispersing or compressing it. It melts from above (air temperature and direct sunlight). It melts from below (water temperature). It freezes. It melts here and freezes there. It’s not an easy, simple thing to measure, especially when you consider the massive area involved, the harshness of the conditions, and that there’s no solid land on which to base a permanent station.

    [Along those lines, the fact that some North Pole Cams seem to fall over or potentially start floating if enough ice melts gives you some pause. 2007 includes images from an icebreaker, but it's unclear from the comments if this was done just because one was handy, or if it was necessary because of the degree of melt involved.]

    So any effort to argue that this year is more or less than that year, because this measurement is more or less than that measurement, is fallacious to begin with. That, I think, is a main point of the original post, that it’s an environment and situation which is difficult to observe and then water down into a single, easy to consume and accept number. Predicting what will happen is just not easy and simple.

    It’s a complex system. A single number which represents “how much” by any measure is just an oversimplified model of a complex system. Models exist for specific purposes, and to use them for the wrong purpose is wrong. What we need to do is to better understand the system, and to improve our measurements. These are the two things that I think scientists working in that area are attempting, and I’m grateful to them for the effort.

  25. 25

    12 (wilt),
    18 (Edward),

    Something that I consider immensely useful in understanding better (from a visualization perspective) what is happening in the Arctic are the animations provided here:

    The Cryosphere Today

    Watch thirty days of melt and shuffle in action. It’s informative.

  26. 26
    Halldór Björnsson says:

    Re #12.
    Wilt, look at the evolution of sea ice extent this year
    (http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png). You will notice that this summer the decline in extent has been fairly steady (since May). In early July there was a period when the rate of decline seemed to be levelling off. This was concurrent with a cold anomaly devloping in the Arctic. Once that was over, the decline continued. Hence, Dirk’s statement on the sensitivity to weather patterns seems to hold.

  27. 27
    Mark Zimmerman says:

    in 2007 a relatively stable high-pressure system formed above the Beaufort sea, towards the north of North America, leading to rapid melting of sea ice there.

    Have similar conditions occurred in the past 30 years, other than in 2007?

  28. 28
    wilt says:

    Pete Dunkelberg # 22

    Thanks for the informative links, and especially for the observation that the outcome is litterally blowing in the wind: the minimum value will be determined by the local weather, especially the direction and strength of the wind (as it was in the exceptional year 2007). It seems to me that in this situation things like AMO are more important than CO2.

  29. 29
    Hank Roberts says:

    Which navies have submarines operating in the Arctic these days?
    Are any of them, when they have a submarine in the Arctic, providing any data for scientific use on a realtime or frequently updated basis?

    I realize they’re called the ‘silent service’ because they don’t want to be noticed, generally.

    Does anyone know if the Navy’s sea ice publications are based on updated data sets that aren’t available to other scientists, or are delayed?

    (I ask because I remember, when I was a marine biology student for a while in the 1960s, how researchers got their sonar gear from their country’s navy — and each sonar rig had cutouts for particular bands so those scientists couldn’t see their own navy’s submarines. Instead the scientists got together at meetings and swapped data sets a few times a year, and the combined data gave good coverage. Nobody cared about that — it was _realtime_ detection of the submarines that worried the navies.)

  30. 30

    28 (wilt),

    It seems to me that in this situation things like AMO are more important than CO2.

    This is a bait-and-switch. What you are saying is that because there’s wind, and it’s an important factor in the final annual degree of the current, unheard of summer Arctic ice melt, nothing else matters.

    Without CO2, temperatures wouldn’t be warm enough to cause the anomaly and for wind to matter all that much. Yes, certain conditions will tip things further one way or the other, but we wouldn’t be on the precipice of watching summer Arctic ice disappear if it weren’t for dramatic and indisputable Arctic warming. Wind wouldn’t be a factor worth measuring if it weren’t for CO2 and the resulting temperature increase.

  31. 31
    jyyh says:

    “The arctic ice is not simply uniformly thin. It is broken with lots of gaps.” , this is clearly seen in satellite photos where thicker (and usually older) ice floe takes on wind or current and creates an “open sea wake” on its tail.

  32. 32
    John says:

    This article mentions air temperature anomalies a lot. It does not mention sea temperatures or currents? What about the contribution of AMO and others? Have any of the relevant cycles/currents changed in recent years and if so what effect is this potentially having?

    It sounds really bad, but when we have only got 30 years of (incomplete) data for a region that fluctuates between no ice and ice swallowing a third of the planet, what are we really watching here?

  33. 33
    Lou Grinzo says:

    If I may, my page with a lot of these graphs plus some others:

    http://www.grinzo.com/energy/graphs.html

    I semi-regularly update this page, reorganize it, etc. as I become aware of new graphics relevant to energy and climate issues.

  34. 34
    Hank Roberts says:

    “The summers observed by the North Pole Web Cams were very different. (see table …). The onset of melting is typically in early June, but occurred in late July in 2002, and late June in 2003 and 2004. The Web Cam images show very limited melt pond coverage in 2002, but widespread melt pond coverage in 2003 and 2004. In 2003, the melt ponds were widespread by July 4, but diminished in late July, and then reformed in mid-August. ….”

    Much more: http://www.arctic.noaa.gov/detect/ice-npole.shtml

  35. 35

    Another important distinction between weather and climate:

    Weather forecasting is a vital service, heavily funded, with reports used by all sectors of business, agriculture, military and personal lives.

    Climate forecasting reports are poorly funded, outdated, actively suppressed by political groups and lack much of an institutional structure in the US. Met office in England is the exception. Few business have discovered the value of regional climate forecasting.

  36. 36
    DeNihilist says:

    Excellent article. Short, precise, and easily accesable. Thanx.

  37. 37

    28 (wilt),
    30 (myself),

    Actually, I’m going to revise what I said a bit. Wind matters, AMO matters, but it’s not nearly as important temperature, period, and the effect of local (Arctic) weather on temperature.

    Wind and currents shuffle the ice around, which affects measurements of extent, but again, extent is merely a proxy for total ice volume. It may make things look better or worse, by making the proxy larger or smaller, but what really matters is the amount of total melt (and winter recovery in ice volume, again not extent).

    Put another way, one can say that things are no better than is represented by the extent… but things can be considerably worse. This position was presented (and scoffed at on WUWT) by one scientist who said that when the final full summer Arctic melt comes it may be sudden and unexpected. The proxy of ice extent is not what it seems. It’s not volume, it’s not “ice quality,” and it may not even be close

    Do not fall in love with simple numbers and graphs that make a complex world into a simple, predictable place.

  38. 38
    Walt Meier says:

    Thanks to Dirk for a nice discussion of sea ice conditions and for highlighting NSIDC’s news and analysis site.

    In regards to volume, I will point out a couple things:

    1. We have gotten some volume estimates from the NASA ICESat satellite, e.g.:

    Kwok, R., G. F. Cunningham, M. Wensnahan, I. Rigor, H. J. Zwally, and D. Yi, 2009: Thinning and volume loss of the Arctic Ocean sea ice cover: 2003-2008. J. Geophys. Res., 114.

    Unfortunately, ICESat went out of service last October.

    2. In recent post, we mentioned modeled ice volume estimates at the University of Washington:

    http://psc.apl.washington.edu/ArcticSeaiceVolume/IceVolume.php

    These assimilate our sea ice concentration data and then use model physics to track thickness and hence total volume. They’ve shown record low volume since spring. I’m a little bit skeptical that the volume anomaly is so low. One has to keep in mind that these are model estimates and may be subject to some biases. However, the model has agreed well with previous observations and it does provide at least some estimate of volume. Also, while there is less first-year ice and more 2nd and 3rd year ice, which is thicker, compared to recent years, the amount of the thickest, oldest ice (>5 years) has continued to decline. So the volume anomaly may be reflecting that loss of the oldest ice.

  39. 39
    Didactylos says:

    wilt:

    You are comparing four consecutive years. In climate terms, that is meaningless. Yes, some of the 2010 late winter ice was ridiculously thin, and melted as easily as it formed. But the rest of the single year ice is only thin compared to the long term average. You won’t get anywhere comparing it to very recent years, unless you want to join us in speculating about polar weather conditions.

    Was the entire extent of single year ice significantly thinner than the previous year? That’s the part we needed Cryosat-2 for. Instead, we have to make do with scattered observations. We know more southerly ice was very thin. We know that some areas didn’t ice over until the melt season had nearly begun. And those areas have all melted out long ago, confirming that they were, indeed, very thin.

  40. 40
    Douglas says:

    Echoing #14. I would think a complementary measure would be area of arctic covered with 85% sea ice. Or 100%. Does anyone plot this? I just looked at NSDIC and didn’t see it.

  41. 41

    I finally hunted around enough to try to find out where the North Pole Cams are actually located, and was pleased to find the following image, showing their changing locations with time… I was not entirely surprised to find that the answer is “it depends on what day you ask.”

    Buoy Drift Track Map

    It serves as an important reminder that, even with the support of the illusion of the steady, continuous images from the pole cams, the Arctic is a fluid, dynamic environment, not a pseudo-continent made of solid ice as the Rudolph Christmas specials of our youth lead us to believe.

    Has anyone considered, proposed, or implemented an “ARGO float” type project for the Arctic? I’d think it would be quite informative to have an army of robotic buoys which could report their locations and status — either resting on ice or afloat, along with air temperature and, if afloat, the water temperature — giving a clear image of how the Arctic surface stretches and morphs over the course of a year.

    It would also help to silence the critics who keep complaining that the Arctic is a huge gap in the temperature record.

  42. 42
    geo says:

    I am not sure if this has been referenced, for an estimate of volume of ice see:
    http://www.agu.org/pubs/crossref/2010/2010GL042652.shtml

    This will be used to calabrate crysostat

  43. 43
    dhogaza says:

    Wilt:

    It seems to me that in this situation things like AMO are more important than CO2.

    Please re-read Dirk’s article, in which he explains that higher temps have led to thinner ice, which is more easily blown around than the thick sea ice which covered most of the arctic in the past.

    So in a trivial sense, yes, “things like AMO” are more important for the extent figure, because this impacts how the ice is blown around. However, that ice being blown around is still melting.

    Try this thought experiment:

    Dump a few bags of crushed ice into a swimming pool this summer.

    Use some blowers or fans to push that ice towards one side of the pool. Extent will drop.

    Now reposition your blowers or fans to push that ice away from the side of the pool, spreading it across a wider area. The “15% or more” extent will grow.

    Yet … the ice will still be melting. The fact that the water and the air over the water is warm does matter.

    (in actuality, in the arctic, the extent actually didn’t grow earlier this july, but rather the rate of decline in extent slowed dramatically. But hopefully you get the point.)

  44. 44
    pete best says:

    I have a question. As Arctic summer sea ice decline is a central prediction of AGW theory can it be claimed that the increased summer sea ice melt and possibly overall its thickness (volume) is in line with these predictions taking into account natural variability of course ?

  45. 45
    wilt says:

    #37, #43
    ‘Do not fall in love with simple numbers and graphs that make a complex world into a simple, predictable place.’

    Bob, I am trying to avoid the trap you refer to, and I understand and respect the arguments that you and Dhogaza have put forward. And it will probably be a lot easier to discuss this topic once the data from Cryosat-2 have been available for some years. But for the moment I remain unconvinced that overall the Arctic ice is much thinner than it used to be. Let me rephrase my position by formulating two (provocative) statements:
    1. The sea ice minimum in 2008 was above the 2007 value, and 2009 was above the 2008 value. If again 2010 yields a minimum value higher than in 2009, this would not support the hypothesis that we are on the way to a summer-ice-free Arctic (and yes, I realize that it’s only a limited number of years)
    2. In view of the decisive effects of wind and ocean currents, would you agree that the minimum value of Arctic sea ice is more related to weather than to climate? In other words, whatever the outcome this year, neither AGW-proponents nor their adversaries should claim it as a ‘victory’ for their point of view.

  46. 46

    Another Q sort of related. Someone brought up a terrible cold snap happening right now in Peru (see: http://www.bbc.co.uk/news/world-latin-america-10749124 ), as proof against AGW, of course. I spoke about the difference between weather and climate — to deaf ears, I’m sure.

    But I also went on to tell about our cold spell here in the lower Rio Grande Valley (and elsewhere) this past winter, and how I asked the scientists, and they told me we were in a strongly negative arctic oscillation — with wind bringing cold north to south, instead of the usual west-east pattern. And that the global average temps for those winter months were actually above average a bit.

    I suggested maybe Peru is also experiencing the same type of thing, but what did I know, since I’m not a scientist.

    Does anyone know whether this might also be the cause of Peru’s astral winter’s cold snap this year, and ?? is any part of the antarctic or its nearby oceans well above average ??

    I did find this article on Google Scholar (which I suggested my denialist friend make use of), which seems to indicate against this, but have there been any developments on this since 2004? — http://www.nature.com/nature/journal/v432/n7015/abs/432290b.html :

    Atmospheric science: Early peak in Antarctic oscillation index
    Julie M. Jones & Martin Widmann
    Nature 432, 290-291 (18 November 2004)

    The principal extratropical atmospheric circulation mode in the Southern Hemisphere, the Antarctic oscillation (or Southern Hemisphere annular mode), represents fluctuations in the strength of the circumpolar vortex and has shown a trend towards a positive index in austral summer in recent decades, which has been linked to stratospheric ozone depletion, and to increased atmospheric greenhouse-gas concentrations. Here we reconstruct the austral summer (December–January) Antarctic oscillation index from sea-level pressure measurements over the twentieth century and find that large positive values, and positive trends of a similar magnitude to those of past decades, also occurred around 1960, and that strong negative trends occurred afterwards. This positive Antarctic oscillation index and large positive trend during a period before ozone-depleting chemicals were released into the atmosphere and before marked anthropogenic warming, together with the later negative trend, indicate that natural forcing factors or internal mechanisms in the climate system must also strongly influence the state of the Antarctic oscillation.

  47. 47
    Doug Bostrom says:

    I remain unconvinced that overall the Arctic ice is much thinner than it used to be.

    Leaving us with the observation and possible problem that ice that is not visible is either nonexistent or is physically arranged in such a fashion that the total amount has not changed yet is no longer directly visible.

    Presumably if Wilt’s implication that no ice has in fact vanished is correct, this means that -effective- sum thickness of the ice is the same, it’s just stacked into extremely tall, vertically oriented slabs projecting far below the surface of the Arctic Ocean. In other words, volume is equal to the past, areal distribution has radically changed. Has anybody observed these features?

  48. 48
    Didactylos says:

    wilt said: “But for the moment I remain unconvinced that overall the Arctic ice is much thinner than it used to be.”

    Why is this? We lack data, yes – but we’re not as ignorant as all that. Icesat and submarine data show beyond doubt that the ice is a lot thinner now than previously.

    “In view of the decisive effects of wind and ocean currents, would you agree that the minimum value of Arctic sea ice is more related to weather than to climate? In other words, whatever the outcome this year, neither AGW-proponents nor their adversaries should claim it as a ‘victory’ for their point of view.”

    This is missing the point in spectacular style. We can easily discount the year-to-year variation and look at the longer trends. And those are indisputable: ice extent has plummeted dramatically, particularly during the summer (hence having the greatest effect on the minimum extent). So, the real answer to your question is: no matter what happens this year, we are in big trouble. If you call that a ‘win’ for the warmists, then I think perhaps that’s not the most productive way of looking at it.

  49. 49
    wilt says:

    #47 “Wilt’s implication that no ice has in fact vanished…”

    I don’t know why you are twisting my words, but I do know that it’s making the discussion needlessly complicated. Let us focus on the facts and their interpretation. Facts are that the minimum was higher in 2008 than in 2007, and higher in 2009 than in 2008. We will have to wait and see whether the outcome for 2010 is higher than in 2009 (in my view this is more likely than not). If it is, then those results are not easily compatible with an ice layer that is supposed to get thinner year after year.
    Whatever your point of view, I suppose that any reasonable discussion starts with respect for the facts, and for arguments.

  50. 50

    Something to consider, and I had thought about it earlier but did not write what I was thinking.

    One of the current issues is that the multi-year ice was able to build more second year I think that was last year due to natural variability factors. The trend is clear and down but there’s lots of stuff gong on up there.

    I think that the dispersion and changing action of the ice also can trick us. The models are still models and measurements are developing. I’ll be interested to see how things work out with the new satellite.

    With all the complexities, the ice is trending down and doing things that it was not able to do when the pack was thicker and more stable.

    I think it could take at least one more year if weather patterns are nominal to see a more dramatic spike down.

    One of the conflicting bits of data is in between the Navy models and PIOMAS, which shows a dramatic spike down. I wonder if there is an input issue, or resolution issue there?

    The truth may lie somewhere in between. If I were to guess, their might be an ice action issue that is confounding the data collection too. I don’t know, and I’m very interested what the science comes up with this year, that should help refine the understanding of these issues.

    But as has been said before, we are losing the ice. It’s just a matter of time. The changes in the weather patterns if they become more normal especially with the AO, then that and other factors could speed things up, while other factors could slow it down.

    Lot’s to learn and it’s fun to try to figure it out. But the end result is we are dong some rather amazing damage to our planet in relation to our ability to safely interact with those things that have kept us alive so far.


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