New Arctic satellite data shows Arctic literally on thin ice
April 6, 2009
Data from NASA satellites show younger, thinner Arctic sea ice is replacing multi-year ice. Credit: James Maslanik, University of Colorado
The latest data from NASA and the University of Colorado at Boulder's National Snow and Ice Data Center show the continuation of a decade-long trend of shrinking sea ice extent in the Arctic, including new evidence for thinning ice as well.
The researchers, who have been tracking Arctic sea ice cover with satellites since 1979, found that the winter of 2008-09 was the fifth lowest maximum ice extent on record. The six lowest maximum events in the satellite record have all occurred in the past six years, according to CU-Boulder researcher Walt Meier of NSIDC.
The new measurements by CU-Boulder's NSIDC show the maximum sea ice extent for 2008-09 reached on Feb. 28 was 5.85 million square miles, which is 278,000 square miles below the average extent for 1979 to 2000, an area slightly larger than the state of Texas, said Meier.
In addition, a team of CU-Boulder researchers led by Research Associate Charles Fowler of the Colorado Center for Astrodynamics Research, or CCAR, has found that younger, thinner ice has replaced older, thicker ice as the dominant type over the past five years, making it more prone to summer melt.
"Ice extent is an important measure of the health of the Arctic, but it only gives us a two dimensional view of the ice cover," said Meier. "Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover. As the ice cover in the Arctic grows thinner, it becomes more vulnerable to summer melt."
Until recent years, measurements have shown most Arctic ice has survived at least one summer and often several, said Meier. But the balance has now flipped, and seasonal ice -- which melts and re-freezes every year -- now comprises about 70 percent of Arctic sea ice in winter, up from 40 to 50 percent in the 1980s and 1990s, he said. Thicker ice that has survived two or more years now comprises just 10 percent of ice cover, down from 30 to 40 percent in years past.
Scientists believe Arctic sea ice functions like an air conditioner for the global climate system by naturally cooling air and water masses, playing a key role in ocean circulation and reflecting solar radiation back into space.
In a related study led by Ron Kwok of NASA's Jet Propulsion Laboratory in Pasadena, Calif., researchers have demonstrated a way to estimate ice thickness over the entire Arctic Ocean. Using two years of data from NASA's Ice, Cloud and Land Elevation Satellite, or ICESat, the team made the first basin-wide estimate of the thickness and volume of the Arctic Ocean ice cover for 2005 and 2006.
"With the new data on the area and thickness of Arctic sea ice, we can now better understand the sensitivity and vulnerability of the ice cover to changes in climate," Kwok said.
A recent study by a team from CU-Boulder's CCAR concluded there has been a near complete loss of the oldest, thickest Arctic ice, and that 58 percent of perennial ice was only two to three years old. In the mid-1980s, only 35 percent of that sea ice was that young and that thin, according to aerospace engineering sciences department Research Professor James Maslanik, who led the 2008 study published in Geophysical Research Letters.
"Heading into the 2009 summer melt season, the potential continues for extensive ice retreat due to the trend toward younger, thinner ice that has accelerated in recent years," said Maslanik, also a member of the Cooperative Institute for Research in Environmental Sciences. "A key question will be whether this second year ice is thick enough to survive summer melt," said Maslanik.
"If it does, this might start a trend toward recovery of the perennial sea ice pack," Maslanik said. "If it doesn't, then this would be further evidence of the difficulty of re-establishing the ice conditions that were typical of 20 or 30 years ago."
The Arctic ice cap grows each winter as the sun sets for several months and intense cold sets in. The total volume of winter Arctic ice is equal to the volume of fresh water in Lake Superior and Lake Michigan combined.
While some sea ice is naturally pushed out of the Arctic by winds, much of it melts in place. First-year sea ice usually reaches 6 feet in thickness, while ice that has lasted through more than one summer averages 9 feet and can grow much thicker in some locations near the coast.
Source: University of Colorado at Boulder
Apr 04, 2007 |
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There are two reasons: First the bulk of the ice that is impacted in the Arctic is floating already so you can melt it all with little change in sea level. The same goes with the Antarctic where the ice shelves are breaking up but are still floating. The second reason is that the sea is very deep and the immediate warming touches the surface and you rely on convection to carry some of the heat to the deep. So sea level rise due to expansion of the water (cold water takes up less space than hot) is currently still relatively low.
The problem we are facing is that without the sea ice, which acts as a dam, the ice on the land of Antarctica and Greenland start to slide into the sea. That does raise sea level. Also if the surface temperature stays high for a long time the temperature of the deep oceans will slowly rise and the expansion raises sea level. Both of these effects take a long time to build up a head of steam and the global temperature average has only started to become noticeably higher than "normal" in recent times.
Now the global warming deniers will be all over this post but there is a lot of irrefutable evidence that the oceans are warmer than they ware and that the Arctic and Antarctic ice is melting WHATEVER THE CAUSE.
There is only 30 years of accurate records, so when they say that the last six years have the least ice ever recorded, it is only in the last 30 years.
While it is true there is less arctic ice in summer, most of it returns in winter. There is little loss of global sea ice, since the antarctic has the most sea ice ever recorded in 2008, over one million square kilometers more ice than in anytime in the last 30 years of measurement. Why the press doesnt mention this is interesting.
The oceans have been cooling since 2003, and warm water is the most effective way to melt arctic ice. With the cooling oceans, a la nina phase, there should be even less summer arctic sea ice melting this summer, even if the ice is thinner.
Here's a graph of monthly sea ice for 2002 to 2009:
http://www.ijis.i...tent.png
Also it is important to keep in mind that we are presently at a Solar minimum which means that the Sun is putting out less energy. So the ice pack should be increasing. So this year should have the LARGEST icepack and it doesn't. CO2 and other greenhouse gas levels affect the poles the most.
Ethelred
Melting sea ice doesn't effect sea level at all. It is just an indicator. Pay attention to reports on Greenland and the Antarctic land mass ice. Those are the sources of rising sea level. Both are reported to be melting at a faster than historical rate. Unfortunately, it is a difficult thing to measure.
Rising sea levels are also caused by the thermal expansion of seawater due to warming. I believe this is now the major cause of higher sea levels.
Could it because I was right and just pointed out what the Graymouser's post showed. Greymouser for once hasn't given me a one.
Miki look at what the Ratfornicator(Yes I have read all the Fafard and Greymouser stories, have that one in hardback first edition) has posted. There is nothing wrong in my post.
Apologize.
Ethelred
Maybe my grandkids will complain that the sea has risen 2inches in 50 or so years time but tbh, I'm sure they will be as fearful of it as any open minded free-thinker currently is.
Personnally I would consider NASA using their resources for something benefical like measuring the amount of toxic plastic crap in the oceans due to us humans (a real problem) and even pushing to get something done about it to be far more worthwhile than this doctored scaremongering BS!
http://www.natura...802.html
Icepack is driven by precipitation. At the poles it hasn't been a notable precipitation year. With lower than average precipitation be it rain or snow, the ice pack cannot expand. Let it also be understood that the relative humidity has a lot to do with the ice loss. Ice will also sublimate in extraordinarily dry climates, like the top of Kilamanjaro or either of the poles. This is commonly confused with warmer temperatures by laymen when it is not the case.
What are you talking about? I have not posted let alone commented on your post.
There is basicaly nothing wrong with your first comment. The graph shows that the ice is recovering from its recent minimum. The NW Passage was open in the 1940s, so the recent minimum is not unique. I was going to mark it 3 or 4 until I saw your second comment.
Yet you saw fit to give a one.
Yet you gave it a one.(Yes I said the same thing twice. Duplicity results in duplication.)
Interesting claim, so false and so easily checked. Since I wouldn't be complaining about a ranking that wasn't there it should be clear to anyone that noticed that IT WAS THERE. You have the first comment on that. It was one which makes it obvious who did it since it was the ONLY ranking it had at that time. There are now two others.
You gave me the one. I commented on that.
It is beyond duplicity to claim you gave me a one for calling you out for giving me a one.
Its a plain lie.
That's TWO apologies.
Not that I ever expected one. I astounded that you would just plain lie to cover up dubious behavior. And such a stupid lie. Makes one wonder just how many of your posts a equally intentionally false.
Ethelred
It can act as a dam when it is pressing against the land as well as glaciers. Not the case though for the Arctic. Not even around Greenland most of the time. It does seem to do it in some parts of the Antarctic.
Much of sea ice in the Arctic is initially formed by the sea itself freezing. Then the snow can accumulate on it. Not until then. Again the situation is different from the South Pole where the sea ice is mostly overflow from the glaciers.
Ethelred
That's false. The way it works is precipitation at a higher elevation precipitates. It does not melt or sublimate and over the course of seasons builds up. Since ice itself acts as an incredibly viscous fluid it flows down to the sea where it calves or continues advancing. As that ice advances over the ocean it receives more precipitation which doesn't melt or sublimate while the sea eats away at the base of the ice pack. If this ice pack reaches another point of land as it advances through the adjacent sea, as it has in the case of the ice shelves, the sea water erodes the base resulting in the shelf itself.
Salt water of the consistency of the ocean has to be brought well below the freezing point of fresh water as to make your statement unrealistic, as well as require that the ocean water nearer the poles be at least twice as saline as the ocean water near the equator due to the loss of fresh water, (the salt would precipitate out of solution during the freezing process).
Precipitation and relative humidity drive glaciation, which in turn drive sea ice extent and ice shelving.
My apologies Ethelred.
You gave me the one. I commented on that.
It is beyond duplicity to claim you gave me a one for calling you out for giving me a one.
Its a plain lie.
That's TWO apologies.
Not that I ever expected one. I astounded that you would just plain lie to cover up dubious behavior. And such a stupid lie. Makes one wonder just how many of your posts a equally intentionally false.
Ethelred
What is your problem!
Where is my first, invisible post? Where and why did you pick up my name as I had not posted here at that time? I only post after I saw your childish rant.
If I choose to rank anyone 1, I will, no matter what you think or say. Grow up! It's no big deal.
Shut up or you will be sent to bed with no supper.
I don't normaly respond to rants, but you have got a problem.
Happy now ;-)
Sea ice is ice that it floating. A single block of sea ice can be mostly floating and still be pressing against a shoreline. That pressure against the shoreline can result in backpressure on glaciers. This does seem to be the case in many areas of the Antarctic. I don't think it has any siginificance in the Arctic as the only massive glaciers there are on Greenland and the sea ice around Greenland does not have any land to press against besides Greenland.
Thats the case for Greenland and Antactica. Not for much of the sea ice in the Northwest Passage area.
It wouldn't require that much of an increase in salinity. After all the ice isn't very thick in comparison to the water below it. Yes the ice would squeze out the salt. I recall reading about it a number of years ago. Will try to find a link.
Found some stuff.
http://www.arctic...ams.html
That is what I was remembering but there is more there about the physics of ice formation in salt water. That kind of ice is quite different from Antarctic sea ice which is glaciers that are going of to sea.
Link to a simpler site.
http://nsidc.org/...ion.html
For those that think this a US government plot to turn money over to vile liberal Illuminati here is German site:
http://www.awi.de...rmation/
Oh dear I wrote up that stuff above first. Still I think its good stuff.
Thank you.
Ethelred
Where did I claim you posted anything? In fact I pointed out that you didn't bother to explain what you didn't like about my post.
If you hadn't ranked my post as a one there wouldn't have been anything to rant about.
Grow up yourself. Giving me a one is standard for you, in this case you even did it to a post you actually admitted was correct. You do it to pretty much any post you don't like with no matter its merits. Kinda like President Dumbya firing people that told him the truth. Which led to wonderful things for all of us.
Speaking of childish remarks.
Yes. Your behavior on this site when confronted by facts you don't like. If you don't like what I write I have no problem with a rebuttal and would welcome an actual debate. I do have problem with an attempt to suppress information that disturbs your ignorance.
Ethelred
No. I was rather hoping that it was sign of maturity.
However since you only did to that one post I will not seek a mighty vengeance. Childish behavior is to be expected occasionally of the Gray Mouser. Of Fafhrd as well but less often. I have been advised by Ningauble of the Seven Eyes on what do if the need arises.
Ethelred
Forgoe the ranking system for the conversation gained by not marking an arbitrary number to someone's opinion.
Now as for spammers and people who are downright incorrect, feel free to give them a 1 when called for.
No he's not Noein. Ethelred can actually type out full sentences that make sense, and are devoid of mindless propaganda.
Point to you. Consistency has never been one of my strong points.
When you see Ningauble, tell him (it?) that I have one of his eyes...
I am pleased to see the change, but can you tell me what it was that convinced you when I could not? I am curious from an academic perspective since I am always interested in doing a better job of communicating. Thanks.
I think you have me confused with Miki or Gray.
I recall the conversation involving how glacier could advance and calve simultaneously, but I was an observer, not a participant to the best of my recollection.
You can only be sure with the first person. After that you can figure it out IF you see each increment.
If 1 with only one person then that person gave a one. If it then goes to 3 with two the second person gave a 5. If it went to 3 but you didn't see it till 4 more people joined in you can only know that first person's vote. The voters seem to be listed in order of time voted. If you first see two votes and it totals three then it could be
1 5=3
5 1=3
2 4=3
4 2=3
3 for both
Ethelred
Go to a thread you have posted in and click your name. It will open your profile as another observer would see it. Click the activity tab and that will pop up a list of your posts and who ranked them.
It's interesting to see who's running n alias through that method. It's how we've figured out Noein, MsDeeNyer, and a few other random names are the same person.
Mick.
Thank you.
I don't mind getting a one. Well I can live with it. But I want a chance for rebuttal. Its going on now in another thread where a guy called UncleDave just gave me so many ones I went down a point from 3.6 to 3.5. He hasn't made a single post there. That's what really ticks me off.
Ethelred
Now you have shown me how to do it, I have notice the same with UncleDave. I also wish people would show their country or origin in their profile. It would give a bit of insight into their reasoning, especially political and forgive rather than note spelling errors, some of which alter meanings.
With your nickname you should be another Brit, are you? I usally roughly judge on the spelling of colour (color) etc. but have not seen one to judge.
Mick.
Hence why miki and gray look at me oddly when I talk highly of a forum combatant.
I would like to see less bickering and more honest exchange of ideas, but that is just asking too much. It is all part of the internet culture.
Just be glad this isn't YouTube with comments like: "You're an idiot!", "What a @#$", and the classic "You're mother is a hamster, and your father smells of elderberries!"
Apologize to mikiwud, even if he did give you a one that is his right to do so!
No. From California. Something I wrote up a while ago:
Ethelred ban Hangyvezenyl, AKA the Armourer, was the cousin of a character my brother had resurrected from another player that had retired from the game, Eusebius ban Hangyvezenyl. The game was a peculiar play-by-mail variant of Diplomacy called Slobsovia.
Slosbovia existed largely to tell stories about what was going on in the game. The most unusual rule variation was the total lack of victory conditions. The game literally could not be won. If a player had more than a certain number of provinces they had to assign some to another player as a lieutenant. That player had the option to revolt. As a consequence even if someone held every province they still could only keep them with the cooperation of other players. To give you idea of how important the role playing and story telling aspect was the Slobinpolit Zhurnal that the game was published in usually had about 5 pages of game results and 95 pages of story and often some art.
http://en.wikiped...lobbovia
Ethelred just seemed like an appropriate name at the time.
Ethelred
How is this possible? The current arctic explorers are encountering temperatures of -40; as far as I know water, even salt water turns to ice at temperatures this low. Can't they find it? Maybe it's out of sight of NSIDC satellite sensors?
Thanks for explanation. I was, as a Brit, thinking of Ethelred the Unready (which apparently he was not) 968-1016. Ruled 978-1013 and 1014-1016. Plus another couple of King Ethelreds.
As in a lot of things, the obvious explanation is not always correct. Especially in cause and effect. If we all reasoned the same way, we could all be wrong. Not just me!
Mick.
Water temp is a greater driver than air temp. Tht's another thing people get confused about, and why I was at odds with Ethel's explanation of sea ice formation. The surface waters are well above -40 at this point in time of the year. Probably in the area of -20 or so.
"Ethelred is an Old English name meaning "noble council" or ("well advised") (æþel and ræd, cf. German Adel and Rat)."
Incidentally, the order the in which the names are listed in the scoring page seems to be in order of 'seniority' (i.e. those that registered the earliest).