Tuesday, October 09, 2007

A very thin reed

Tamino has an interesting post on Arctic and Antarctic ice extent. Now if you stare at the stuff long enough you realize that the maximum is pretty much always the same

but after a bit of thought, you realize that the Arctic is a closed ocean and it pretty much freezes completely over each year (PS the above only goes to 2000 and does not show the 2000 - 2007 decline. Tamino has the more recent information). Still, this is not completely the case, and analysis shows that even in the winter the ice area is declining.
we can learn even more by looking at maps of the maximum ice concentration from the National Sea Ice Data Center. The map on the left is from Feb 1979 and the one on the right from Feb 2007.
















The major differences are in the areas north of the Norway/Russian border. But when we look at the minimum extent from 2007 we see that it is the area between Alaska and Siberia that is relatively clear of ice.


So, we still need to decide whether our bet with Belette is in carrots or in pounds. Hmm, maybe we are looking at the wrong thing. During the autumn and winter the Arctic freezes over, but HOW THICK IS THE ICE. The thicker the ice, the more heat needed to melt the stuff in the summer. The thinner the less.

There are not very many measurements of ice thickness trends for obvious reasons. The best come from Rothrock at the University of Washington who analyzed data from nuclear submarine cruises (Al Gore played a key role in getting these released). Here is what he came up with.


What is a bunny to do? Well we will chew a few carrots and keep a close watch on how rapid the freeze is and try and figure out how deep.

31 comments:

Steve Bloom said...

The last sentence in Rothrock et al (1999) is, IIRC, a reference to the Navy's refusal to cough up everything they have. Of course the Navy's own sea ice modeler (Maslowski) has that data, and he's the one who's made the most extreme projections of ice loss (although sans publication). Peter Wadhams has more recent information from Royal Navy sub cruises, but he hasn't published anything lately. Also, I'm not sure how terribly relevant Rothrock et al is to the present trend since it predates the inflection point that happened around 2000. Finally, since there is very little multi-year ice remaining, is the thickness data still especially important?

Looking around a bit, it appears that Rothrock's home page has much more current and complete stuff (still missing the secret data, though).

Anonymous said...

Great. Just what we need, another scientist, publishing a report, and not releasing the information he used.

Looks like the next project for CA.

Anonymous said...

Actually, what is most significant is the mass loss for arctic sea ice over the past half century, ie, AREA at minimum x thickness.

I have seen graphs for glacier mass and for land ice mass, but don't recall having seen any for sea ice mass. Probably because the data on thickness is so thin.

EliRabett said...

The thickness data is important, because the thickness of the new ice predicts the next year's melt.

Cynthia said...

So even with all the intelligence collected by submarine sailors, covertly or otherwise, the base of the iceberg is still shrouded in mystery -- figuratively speaking, of course...

Hank Roberts said...

It'd be cute to see CA go up against the Russian, Royal and US Navy secrecy rules.

The "Gore Box" declassified maybe a third of the Arctic Ocean and all that was released thanks to then VP Gore's pressure for opening up the data.

CA should go after the Russians for their data, none of it has been released.

There's a lot of work at the Navy Postgrad School in Monterey and on their website. We can hope the anonymite from CA is correct that many papers are indeed being written (their thesis papers are mostly online) even if the underlying ice depth measurements are still classified secret.

For this, our climate data collection instrument is the nuclear attack or defense submarine fleet loaded with Trident MIRVs and the Russian equivalent, all hiding under the diminishing ice, kept hidden under the ice to be able to make the planet-killer third wave nuclear war move -- the "greater madman" mutually assured destruction retaliatory strike back meant to deter a first strike by anyone.

I'm sure CA can get the data by asking nicely.

Nitwits.

Say, does the killfile work on IP numbers? I don't want to ignore any anonymouse with a brain.

Anonymous said...

This chart shows how the mean thickness has changed over the last 40 years -- decreased by about 40%.

So, if the area covered by the sea ice has declined by about 50% over that same period, the percent mass loss (at the end of the melt season) has been somewhere around 70%.

No, nothing out of the ordinary here.

Anonymous said...

The thickness data is important, because the thickness of the new ice predicts the next year's melt.'

Understood, but from the standpoint of assessing the impact of climate change, the percent ice mass loss over the past 40 years is even more significant than percent extent decrease or percent thickness decrease alone.

Anonymous said...

"submarine fleet loaded with Trident MIRVs and the Russian equivalent, all hiding under the diminishing ice, kept hidden under the ice"

That would make a funny cartoon.

Flash forward 20 years when a couple hundred US and Russian submarines are all trying to hide under the one remaining piece of arctic ice the size of a football field -- with all the remaining polar bears crowded on top, of course.

Hey, that gives me an idea. maybe we can paint all the submarines white on top and keep them cruising around on the surface. that way the polar bears can use them as hunting platforms. The submarines would certainly be more useful in the latter capacity than they are now.

Steve Bloom said...

Hank, there's a possibility here of serious jail time for some of the auditors if they're persistent enough about that data, so let's not be too discouraging. Seriously, since the data they're not releasing is for the 200-mile economic zones, I have a feeling that military secrecy is just an excuse. I suspect certain privileged parties may have access.

Eli, I didn't have a chance to look at the other Rothrock papers yet, but the 1999 paper is for summer thickness. IOW, is there any useful information about the thickness of the recovered ice?

Anonymous said...

The earlier mentioned seaice.dk has great charts about this. You can go to september and apply date and then change the year and apply date again to check it. Years vary a lot, sometimes the northeast passage has lots of ice and sometimes a lot less. I think it was completely clear in 2005 for example, there was less ice than in 2007. But then there was ice elsewhere.

http://www.seaice.dk/test.N/
use the quickscat data from the top menu..

This doesn't of course mean that there are no trends in the area, just that the other signals change a lot more and lot more clearly, and we have to make sure that the area isn't a side effect of these other signals like the different location of the ice in different years.
But look at the data yourself. You find the years are quite different.

-flavius collium

Anonymous said...

I was reading a NY Times article about winter ice in the Sea of Japan, which noted a loss of ice in the last decade, with a corresponding loss of tourism. It's not all happening at the poles.
stewart

EliRabett said...

Anon 9:15, but Eli's purpose here is not climatological but assessing what he is going to bet Belette

EliRabett said...

Hi anon 6:18, you can clearly see the loss of ice in the two winter images of this post. If you go to the web site you can track it over the years.

Anonymous said...

Sorry to interupt the thread, but it looks like McIntyre is moving on to push some other bean -- again, (because the "Hansen bean" has yielded a sprout rather than a giant bean stalk up to the sky like he thought it would):

"John V has posted some graphics recently arguing that CRN1-2 yielded pretty much the same results as major temperature indices and, in some sense, vindicated these results. As Gavin Schmidt has pointed out, the U.S. is only 2% of the world’s surface; and as I’ve observed on many occasions, the statistical methodologies and data quality in the U.S. are different from the ROW, as is the history.

I’ve been focussing more on ROW issues recently rather than U.S. issues..."

I think we need a bean counter to keep track.

Gareth said...

The freeze has started, but the anomaly has increased to -2.5m km2. They'll have to add some more room to the bottom of that graph - last time they did that was in June/July...

Anonymous said...

Hey, maybe this Beancounter Mouse would suffice.

EliRabett said...

Ah, Eli's sister in law, the CPA!:) (She will kill me. . . )

Anonymous said...

That's your sister-in-law -- a mouse?

Hmm, I guess that means your parents had no problem with mixed marriages.

What do they call their offspring, by the way? -- Mabbet? or Rouse?

BTW, your sister in law doesn't really read this blog, does she?

EliRabett said...

What? You never heard of cross-species dating?

Anonymous said...

"Anonymous 8:15 AM said...

This chart shows how the mean thickness has changed over the last 40 years -- decreased by about 40%."

It's almost like that chart is missing a line: 1977-1992.

Since there's accurate satellite data starting in 1979, seems strange they'd omit it.

As it is, they're comparing a 18 year period (58-76) to a 4 year period (93-97).

Also, they're not showing data from 98-06, which would include the record low years (and the date on the file is Feb 05).

Inclusion of all this data would show a greater difference, wouldn't it?

- Henry

EliRabett said...

Go read the papers at Rothrock's site. This is a blog.

Anonymous said...

I posted the link to the above chart -- from Rothrock et al. (1999)
http://nsidc.org/sotc/sea_ice.html

Also, sea ice thickness would explain why you get "dropouts" in the "extent " in a single summer like we just saw.

The ice thickness decreases from year to year until it drops below the minimum thickness needed to kepp it from melting entirely over a single summer melt season.

I suspect we will see many more such dropouts in the coming years before the ice disappears entirely at the end of the melt season.

In other words, the ice extent will no longer be anything close to a smooth curve.

EliRabett said...

The link is to a much better discussion than Eli's post.

Anonymous said...

Anon 9:23

I looked at your chart, and simply commented about the years covered.

And to Eli: you're right, this is a blog, and the discussion is Arctic Ice.

And I did RTFR, such as this one:

http://psc.apl.washington.edu/pscweb2002/pubs/Rothrock&Wensnahan-JAOTO.pdf

and found that "The Navy's Arctic Submarine Laboratory (ASL) had the foresight to save all ice draft data starting with the first cruise in 1958 and continuing until the present.

There have been over 70 cruises, roughly one per year, each lasting some 20 to 40 days and transiting much of the Arctic Ocean, sometimes once, sometimes twice. Many of these draft data have been released for a region covering about half of the Arctic Ocean and are archived for public use at the National Snow and Ice Data Center (NSIDC)."

Data IS available.

and here:

http://psc.apl.washington.edu/pscweb2002/pubs/Wensnahan%20etal.(2007)EOS-SubData.pdf

"All useable data from U.S. submarines from 1975 through 2000 within the SCICEX box are believed to be now in the public archive at NSIDC."

More data.

and also looked at the synopsis of the SCICEX trips, as listed here:

http://www.ldeo.columbia.edu/res/pi/SCICEX/Pages/SCICEXab.html

in which the following jewel is listed:

Title: Arctic Ocean Methane
PI(s): Keith Kvenvolden, USGS
Point of Contact: Keith Kvenvolden kkvenvolden@usgs.gov

SCICEX Cruise: 1993

Abstract: In this project, we have shown that methane a "greenhouse gas" is present throughout the arctic ocean. In surveys conducted mainly between 120 and 230 degrees longitude using the U.S. Navy nuclear submarine Pargo (1993) and the Canadian ice breaker Louis S. St. Laurent (1994), we showed that methane is present in water beneath the permanent ice at variable concentrations near the surface that usually exceed the atmospheric equilibrium concentrations of about 4 nanomolar by factors of about 1.3 to 4. Methane concentrations decrease with depth.

More data.

- Henry

stevesadlov said...

Top extent plot records an apparent regime change in 1978. Second set of plots incurs a regime change in 1950. I doubt Rumsfeld had much to so with either.

Fergus said...

sorry that I can't find it, but a report out of Norway last month featured in an article, which said that the sea ice this year around the Kara/Laptev seas was about a metre think. In previous year it has been around two metres think at the comparable time of year. This is the only material I have found on the subject since Rothrock (there's a discussion of how valid the R. data is in ACIA or ICARP). There was no formal finding, but the implication is that the Summer single year ice may be only half as think as previously, across large areas of the Arctic.

Perhaps you ought to take that bet...

Fergus said...

Revision; that was Schauer at the AWI (Germany, not Norway): http://news.mongabay.com/2007/0914-sea_ice.html

There was a paper on '05 by a team from Southampton which used data from HMS Tireless, and stuff from Haas, Zhang, and assorted others; much of it is about estimating thickness from assorted satellite data; only two base their findings on direct measurement.

To 2006, average thickness probably declined by about 43%. This comes from a comparable decline in multi season ice. There's nothing much on how thick the single year ice 'should' be, but ~1m seems a reasonable average.

cce said...

Sorry for this off topic post.

I recently gave a presentation to a friend's Audubon group titled "The Global Warming Debate." I've added a narration and converted it to a video. My goal was to create something that is both easy to understand and covers the topics that people might hear on TV , on the Internet, or in skeptical books. It should be a good companion to any (good) documentary on Global Warming. The popular press and blogosphere obsesses over these details, so it's important for the average person to be aware of the actual facts and evidence.

I'm hoping to get feedback so that I can correct any significant problems or inaccuracies. I don't want to be accused of spreading misinformation.

It is broken into 5 parts, but if you watch it from start to finish it is about 3 and 1/2 hours. So, it is not insignificant in content. While recording the narration, I went from not sick to sick to not sick so my voice can be pretty hoarse in some places. I also make no claims to my skill as a narrator.

I cover these topics:

Volcano Case Study/Lyndon LaRouche
History of Global Warming
IPCC 4th Assessment Report WGI
The Scientific Consensus
Attacks on the Consensus
Greedy Scientists
A New Ice Age
Attributing CO2
Glaciers
It's Cold Outside
Solar
Cosmic Rays
Proof!
Climate Models
The Hockey Stick
Why Now?
Energy Issues

I spent some time at the library and purchased a number of "historical" books. For example, I spent a lot of time documenting the "Volcanoes cause more ____ than all of mankind" skeptical claim, which many might find amusing. I retrieved some additional "global cooling" articles from the '70s. I have Hansen's entire 1987 Senate testimony (his '88 testimony was, sadly, missing). I have the original graph from Lamb first published in 1965 and covering the temperature of Central England. This eventually became the "global temperature of the last 1000 years" chart from the first IPCC report. I have a lot of other graphics and charts taken from journal articles, and swiped from the internet. Some should be familiar, and I hope that no one minds that I used them (I cited the sources). I have more than what is in the presentation, and can provide these documents to those who request them. However, my first emphasis is on creating a reasonably final version of this presentation.

I've uploaded the parts to one of those free web hosting sites. It is here:
cce.000webhost.org

This site may not be adequate, but for now it will have to do. I picked it mainly for its high monthly bandwidth limits, but it seems pretty sluggish sometimes.
(I looked at Google video but the videos are too small to provide the text based detail necessary.)

The video uses the H.264 MPEG4 codec and requires a recent version of Quicktime. It is 640X480 which is large enough for the detail I needed. I went to great lengths to make sure it will play in real time over a dialup modem. I might make a “broadband” version that will be 800X600.

Because it is still a draft, I ask everyone not to publicize or distribute it, beyond the blog sites that I am posting this to.

Please send me any feedback that you wish (email address on site). I have worked on this for 5 months, so I am not eager to turn it inside out. I am more interested in correcting significant errors.

Thanks!

Hank Roberts said...

Speaking of cross-species dating, a pointer to a longterm online classic:

http://www.kevinandkell.com/1995/strips/kk19950904.gif

Anonymous said...

Excellent article, it will be interesting to see, if the winter trajectory will mimic the Summer again, or buck it, like it did between 1998- 2004. If not we could see a highly accelerated decline for the next few years.Grave maintenance and Care - Ireland!