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Currently, Arctic sea ice extent is reaching near record low levels, so thought it might deserve its own thread. I posted earlier on a storm going through the Arctic a few weeks back.
Here's an image of sea ice in the Arctic before and after the storm:
And currently (hot-linked so it'll keep changing):
There are 3 measures of Arctic Sea Ice.
1) Extent - amount of area that is ice clogged; usually anywhere that is covered by 15% or more ice
2) Area - total area of just the ice itself
3) Volume - Ice Volume, obviously. Requires a satellite
Volume divided by area gives the thickness of the sea ice. Sea ice extent has declined slower than sea ice area, which in turn has declined slower than sea ice volume. This suggests that ice is getting more fragmented, and ice is melting more from the bottom and thinning rather than from the edges.
Notice that sea ice volume has been decreasing rather steadily while sea ice extent hasn't passed 2007 levels (until probably this year)
Should be interesting to see what the sea ice does in the next month or so. Biggest determinant of this year's concentration will be the configuration of weather systems; in 2007 the weather patterns were setup in a way to draw warmer water from the North Pacific into the Arctic Ocean. A repeat of that pattern would increase melting. Also, what would the weather effects of little or no sea ice be? Ice reflects sunlight, open ocean absorbs most of it. But at this point in the year, the sun is so low in the atmosphere around the north pole, so there isn't much sunlight to absorb. Open water evaporates water while sea ice is kind of a "lid" between the ocean and the atmosphere. This could affect the dominant pressure and air circulation. This graphs shows how drastic the summer volume decrease has been:
If the trend holds, a summer without any Arctic sea ice should occur within the next 10 years. I know this thread lends itself to a global warming debate, but I hope this thread would stay on the topic of the Arctic ice for its own sake rather than diverging to a more general topic. And yes, I know Antarctic sea ice has been increasing, though the data shows its increase has not been as dramatic as the Arctic sea ice loss. I wanted to focus on just the Arctic for now.
Thanks for the link, that ice volume chart was a shock, I didn't know that we were so much below 2007 levels as I don't follow the subject much (volume cut by half if the projections are correct).
Btw, looks like the absolute low sea ice area record is about to be broken.
^^ Re. the ice volume chart at the bottom - what strikes as much as the amount of extra melting in the past ten years (you're saying that ten summers ago there was three times more ice up there than this summer?!) is that each summer since 2002 has had less ice than the one before with no anomaly apart from 2007 (with a less pronounced trend in the winters). I find it hard to believe that summer temperatures over such a big region can be uniformly going up and up every year with no cooler years thrown in for variability - is there a 'point of no return' factor at play which outweighs the importance of actual temperatures or synoptics?
NASA released a remarkable satellite image (above) of the Arctic storm discussed below. Click for background and technical details.
The National Snow and Ice Data Center has posted on what it calls “a most interesting Arctic summer,” and that is certainly the case, given this week’s powerful and rare summer storm, which is churning the Arctic Ocean’s already thin and reduced sea ice cover.
In the third installment in a running series of posts on the potent storm, the Arctic Sea Ice blog, a popular aggregator of all things related to the sheath of ice floating on Arctic seas, has proposed calling it the “Great Arctic Cyclone of 2012.”
An unusually large, long-lasting, and powerful cyclone was churning over the Arctic recently. Two smaller systems merged on August 5 to form the storm, which at the time occupied much of the Beaufort-Chukchi Sea and Canadian Basin. On average, Arctic cyclones last about 40 hours; as of August 9, 2012, this storm had lasted more than five days, and had an impressive low pressure below 958 mb.
^^ Re. the ice volume chart at the bottom - what strikes as much as the amount of extra melting in the past ten years (you're saying that ten summers ago there was three times more ice up there than this summer?!) is that each summer since 2002 has had less ice than the one before with no anomaly apart from 2007 (with a less pronounced trend in the winters). I find it hard to believe that summer temperatures over such a big region can be uniformly going up and up every year with no cooler years thrown in for variability - is there a 'point of no return' factor at play which outweighs the importance of actual temperatures or synoptics?
My guess is that the Arctic has warmed up past a threshold where every year is warm enough to melt more ice. Cooler years melt less ice, but almost every year melts some ice, similar to a series of winter days with a mean above freezing that melt some snow every day even if the nights are below freezing, so total snow cover continuously declines. Summer melt is faster since most of the ice is close to the freezing or rather melting point. There is some variability; some years so bigger decreases than others. The estimate for the minimum volume this year is shockingly low, 3000 cubic kilometers or less than 1/4 of what it was a few decades ago. My guess of the future fate of summer sea ice:
1) Sometime within the next 10 years there will be a summer with no Arctic sea ice for short time. The sea ice extent would have to have a large nosedive
2) Arctic sea ice could stabilize at a new, lower value because some portions of the Arctic stay too cold in the summer.
I'm leaning towards (1) since sea ice loss has been accelerating, and a small, thin ice pack might be in danger of fragmenting or blown around to spots where it could melt (just guessing).
wow, amazing stuff the climatic changes that we are going to see to the planet from just purely scientific observation point of view are going to be very interesting.
Ouch. We'll have to watch what happens from here. Will it stabilize and have an early minimum or will it continue to decline the way it is now? And also, how fast will the autumn ice buildup progress? One interesting factor this year versus 2007 is that 2012 had a pretty good Spring maximum (near normal) whereas 2007 was low for the entire cycle.
As for the sea ice volume, I believe that recently (2010 or 11) a new satellite was launched that provided much more accurate figures of sea ice volume. What's up with that? Is the new data baked into the volume figures Nei showed, or is that something else (perhaps less accurate?)? As for Arctic summer temperatures, NASA GISS is just about the most inaccurate measure there is, and there is a dearth of ground observation sites in the Arctic. While GISS is better than nothing, it should be taken with a grain of salt. With that in mind, I find it doubtful that there has been a uniform increase in summer temperatures in the Arctic over the past 10 years. The sea ice data alone shows a big warming, sure, but a neverending train of warmer summers sounds suspicious. I'm sure there were a few cooler years mixed in, even with the warming trend. There certainly were cooler years in the High Arctic settlements such as Barrow.
The NORSEX chart that Cambium posted is a different measurement than what he NSIDC uses, and it looks to me like it's a tie of the record more than anything else. Of course it will break the record on that chart in short order, it just hasn't occurred yet (at least by any significant margin).
Nei is right in that if the present trend continues there will be a ice-free summer in the Arctic sooner or later. I'd say more in the next 20 years than 10 years, due to natural variability and the like. The big question is, of course, whether the present trend will continue. Some, including myself, say no, and others say yes. I also agree with Nei in that I would like to keep this thread purely interested in Arctic sea ice for its own sake, and not to bring climate change into it (well, nothing beyond Arctic warming). We "coolists" had our day in the sun last March, now it's the "warmist's" turn.
Harkening back to the first paragraph, as it stands now, has the sea ice set a new record for the most extreme swing from Spring to Autumn? Going from a bit above normal for the maximum to record lows for the minimum sounds quite unusual.
Another note: with the before and after maps it seems that the storm and melting has almost exclusively wiped out the areas that had a low ice concentration. The areas that had the densely-packed ice remained stable (by melt season standards). While everything could change between now and the minimum, I think the "low hanging fruit" has been picked off, and the melting rate has probably been maxed out. We're entering that time of year when the ice curve starts to bend. How much it bends will determine how low the minimum will go.
As for the sea ice volume, I believe that recently (2010 or 11) a new satellite was launched that provided much more accurate figures of sea ice volume. What's up with that? Is the new data baked into the volume figures Nei showed, or is that something else (perhaps less accurate?)?
The volume figures I showed are from PIOMASS, which is not from a satellite (which I originally assumed). I think it's from a combination of submarine soundings and modeling. Details here:
part of which is nothing more than a quoted newspaper article 50% more loss computer climate forecast models isn't saying much, since they've performed terribly at predicting summer sea ice.
Quote:
As for Arctic summer temperatures, NASA GISS is just about the most inaccurate measure there is, and there is a dearth of ground observation sites in the Arctic. While GISS is better than nothing, it should be taken with a grain of salt. With that in mind, I find it doubtful that there has been a uniform increase in summer temperatures in the Arctic over the past 10 years. The sea ice data alone shows a big warming, sure, but a neverending train of warmer summers sounds suspicious. I'm sure there were a few cooler years mixed in, even with the warming trend. There certainly were cooler years in the High Arctic settlements such as Barrow.
I'm not sure why you dislike GISS, its results haven't been much different than other surface based land measures, and satellite record measure something slightly different. You could average individual stations, rather than creating an average for individual regions as GISS did. The same link I posted averaged 137 of the stations below to get the following chart with similar results to GISS but I thought GISS had a more accurate procedure. I'd curious to see more data, though.
The NORSEX chart that Cambium posted is a different measurement than what he NSIDC uses, and it looks to me like it's a tie of the record more than anything else. Of course it will break the record on that chart in short order, it just hasn't occurred yet (at least by any significant margin).
Quote:
Nei is right in that if the present trend continues there will be a ice-free summer in the Arctic sooner or later. I'd say more in the next 20 years than 10 years, due to natural variability and the like.
My thought was that there would be one unusually warm year that would reach 0 summer sea ice even though the average wasn't declining as fast. The following summer might not be ice free.
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