Guest post by Steven Goddard
In past years, NSIDC has referred to “declining multi-year ice” as the problem which the Arctic faces. Mark Serreze at NSIDC forecast a possible “Ice Free North Pole” in 2008, based on the fact that it had only first year ice. This year, multi-year ice has increased and NSIDC is now referring to declining “2+ year old” ice as the problem. Note the missing age group (2 year old ice) in the paragraph below from their latest press release .
First-year ice in particular is thinner and more prone to melting away than thicker, older, multi-year ice. This year, ice older than two years accounted for less than 10% of the ice cover at the end of February. From 1981 through 2000, such older ice made up an average of 30% of the total sea ice cover at this time of the year.
Due to the record minimum in 2007, it goes without saying that there isn’t a lot of three year old ice in 2009. Maybe next year they can raise the bar to 3+ year old ice, as the multi-year ice ages one more year?
Multi-year ice has increased from 2008, up to nearly 25%. Compare multi-year ice vs. last year’s map below – upper right corner.
http://nsidc.org/arcticseaicenews/2008/040708.html
The press has picked up on the 10% figure, based on the new higher standard NSIDC has set.
Ice older than two years once accounted for some 30 to 40 percent of the Arctic’s wintertime cover and made up 25 percent as recently as 2007.
But last year it represented only 14 percent of the maximum. This year the figure fell to 10 percent.
Note too that ice extent is nearly back to normal and has not declined significantly from the winter maximum.
The correlation of CO2 and Arctic ice is really quite funny. The problem with correlations (eg cross-correlation) is causality. In a closed system, this become trivial. a measure of input must measure an output.
I do know the NSIDC is fully aware AND capable of performing statisical analysis, but it seems to vaporize once they put out a press release.
The most interesting feature of the 30 year sea ice extent record is October of 2007. The change in sea ice extent (happened to be an increase) was the largest of the recorded period. Yet this is dismissed as due to wind changes. So wind changes can increase sea ice but only AGW can reduce sea ice? Now that is truely an amazing finding.
Goddard Space Centre released a number of sea ice thickness movies and graphics on April 2nd from the IceSat satellite.
Covers 2003 to the winter of 2008 (last year).
Here is an mpeg-1 movie.
http://svs.gsfc.nasa.gov/vis/a000000/a003500/a003593/minANDmax30fps512x288_30.mpg
Webpage is here.
http://svs.gsfc.nasa.gov/vis/a000000/a003500/a003593/index.html
The baby ice is just getting thinner and thinner. Call the doctor.
I suspect NSIDC has been told by their superiors to become more alarmist.
The huge 2007 arctic melt was wind driven. Even most alarmist admit that. As such common sense tells us we won’t replace all that lost ice instantaneously. Common sense tells us we would expect slow but sure increases until we get back to a temperature driven mean. If the mean temperature increases this mean will decrease slowly over time. Sure there will be lots of noise but after all is said and done there is really no logical reason for NSIDC to state anything else.
So, why didn’t they make this obvious statement? Back to my first sentence.
sod,
There is no calculation involved. The NSIDC graph shows 25% multiyear ice.
http://nsidc.org/arcticseaicenews/
No need to be shocked.
the reply i quoted used that number to calculate that we will see 100% in a few years under current conditions. we wont!
the graph is not misleading, but pointing out an important fact: we are still losing older ice!
your article is based on the assumption that the 2 year ice will grow older under current conditions as well. but very few of it will. temperatures are still above long time average. so is extent.
if 2009 extent is below 2008 (looks very similar so far), then we will lose 2 years ice AND older ice again this year.
http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Extent.png
From 1998 through 2007 NSIDC shows about an 8% decline in Northern Hemisphere sea ice extent (below the 1979-2000 mean) and then a recovery to about 4% below the mean in about one year…Nine years to lose 8%; one year to regain 4%…Even Hans Blix could find the significance in that recovery rate.
a comparison between a long time average and a single year doesn t make a lot of sense. why not compare with the maximum extent?
why not compare the last few years with the long time average?
Squidly (03:17:51) :
I’m sorry, but I don’t get it. Do they mean to tell me that if I keep ice-cubes in my freezer for 2 or 3 years before I use them, that they will last longer in my drinks?
Could someone please explain to me just how newer ice melts faster than older ice? I honestly don’t see where the age of the ice can make any difference at all.
That’s because you don’t freeze saltwater ice in your freezer and subject it to periodic freeze/thaw cycles causing surface meltwater to percolate through taking the brine with it!
Henry,
My point about (exactly) three year old ice is that there is almost none, due to the 2007 minimum. There is however considerable ice older than three years, as you mentioned – which is the multi-year ice which survived the 2007 melt.
crosspatch (18:47:26) wrote (editted):
“It would nice to know the salinity values for sea ice by year to fully understand the implications of this subject.
“The amount of salt that works out of the ice is pretty much a function of the amount of sunlight it gets. If you have an unusually cloudy summer, you get less salt worked out of the ice. Now there would be a general range of what is typical, but that will change depending on where the ice was when it aged and the conditions at that location…..”
It is my understanding that sea water does not freeze and entrap salt in place. The water crystallizes as almost-pure ice and the salt is concentrated in the remaining liquid phase. (The same process of repeated melting and freezing is used to purify silicon for electronic applications.) If the freezing face remains open, the salty water will “escape” into the bulk of the sea. Only if the water is freezing around (on all sides of) a blob of sea water will any salt become entrapped within the ice. So I do not see salt “working its way” out of the ice.
Comments invited.
Steve,
Okey-dokey, I get it. Thanks.
Ian L. McQueen (09:11:02) :
crosspatch (18:47:26) wrote (editted):
It is my understanding that sea water does not freeze and entrap salt in place. The water crystallizes as almost-pure ice and the salt is concentrated in the remaining liquid phase. (The same process of repeated melting and freezing is used to purify silicon for electronic applications.) If the freezing face remains open, the salty water will “escape” into the bulk of the sea. Only if the water is freezing around (on all sides of) a blob of sea water will any salt become entrapped within the ice. So I do not see salt “working its way” out of the ice.
Your understanding is at variance with he established science on the subject:
http://nsidc.org/seaice/characteristics/brine_salinity.html
sod,
Most of the multi-year ice was lost during the winter of 2007-2008 due to wind. Obviously there is no in-situ melting going on in the Arctic during the winter.
It is mostly a question of surface area to volume. A thin sheet of ice the same volume as a cube of ice has much more surface area and will melt faster when exposed to warmer air, warmer ocean currents and solar radiation.
The Multiyear ice is thicker, so it has less exposed surface for its volume.
This is really important when the ice gets quite thin late in the summer, but at some 3 to 3.5 meters thick I am not sure it all that significant. If we have a summer that is even slightly cooler than the recent past, or slightly cooler ocean currents all that will not matter. The other side of the coin is that thin first year ice is more prone to being pushed up into pressure ridges by the wind as it is not as strong as thicker ice. Once it gets compacted into pressure ridges that extend above and below the water surface you now have a very thick area of ice which would be very resistant to melting as its volume to surface area would be much higher than the parent thin ice sheet.
The current ice extent plots look like the melt is progressing slower than in the past as the current ice extent plot is still converging with the 1979-2000 mean and diverging from the low extent plot. In short for this time of the year the ice is increasing compared to low ice years.
I personally am expecting to see the ice extent plot merge with and perhaps exceed the 1979-2000 mean line in a few weeks if it maintains its current converging trend.
Larry
From 1998 through 2007 NSIDC shows about an 8% decline in Northern Hemisphere sea ice extent (below the 1979-2000 mean) and then a recovery to about 4% below the mean in about one year…Nine years to lose 8%; one year to regain 4%…Even Hans Blix could find the significance in that recovery rate.
sod (08:37:10) :
[…]
a comparison between a long time average and a single year doesn t make a lot of sense. why not compare with the maximum extent?
why not compare the last few years with the long time average?
In the case of sea ice extent records…”the long time average” is 30 years…The extent of the satellite data. That 30-year period is more or less coincident with the recent warm phase of the PDO/QDO (1978-2005). Almost all of “the long time average” falls within a 27-year warming trend.
If the “single year” is the inflection point…It makes a lot of sense. The Northern Hemisphere sea ice extent didn’t really vary that much from 1979-1998…Basically hovering within 2% of the mean… With a slight down-trend. The down-trend steepened after 1998.
If you download the Lower Troposphere satellite temperature data (either UAH or RSS – I prefer UAH because of the way the data are subsetted) and plot Northern Hemisphere, Southern Hemisphere, Oceans, Land, Arctic and Antarctic as separate curves…You’ll see that the Southern Hemisphere, Antarctic and Oceans warmed less and started to cool sooner than the Northern Hemisphere, Arctic and Land (probably why HadCRUT3 and GIS show more warming and less cooling than the satellite data)…The Antarctic actually shows a linear cooling trend throughout the 30-year satellite record. The peak warming in the Arctic and the cooling both occurred latest in the Arctic data set…Both of those temperature curves correlate quite well with the NSIDC Northern and Southern Hemisphere ice extent graphs.
The current ice extent plots look like the melt is progressing slower than in the past as the current ice extent plot is still converging with the 1979-2000 mean and diverging from the low extent plot. In short for this time of the year the ice is increasing compared to low ice years.
I think you’re misinterpreting the data, currently extent is below 2008 and is converging on 2007, and is 2std below the ’79-’07 average.
I personally am expecting to see the ice extent plot merge with and perhaps exceed the 1979-2000 mean line in a few weeks if it maintains its current converging trend.
Not very likely, at this time of year all the recent trajectories converge and by the end of the month they’re close to indistinguishable. The indications are that this season is following the same path. There’s very little relationship between what happens now and after July.
This post is off topic somewhat but related in a general way.
[snip – see main page]
Surely ice is only fresh water with the solution that it formed from becoming more salt rich?
Martin Mason (11:11:05) :
Surely ice is only fresh water with the solution that it formed from becoming more salt rich?
No, I suggest you read the link I posted above (here it is again).
http://nsidc.org/seaice/characteristics/brine_salinity.html
Phil. (09:42:33) :
Thanks for the link about the formation of sea ice. I’m feeling less frazil-ed already.
Every now and then, when I turn my head just right, a tiny amount of blood squirts through my carotid arteries, and my brain lurches into action. Today is not one of those days, however. Here is what I can remember:
1. Three year ice is not everybody over the age of three, just three year olds.
2. The structural part of ice is fresh water. This is the good part.
3. All kinds of stuff can be caught in the structure of ice, including salt, Chinese black carbon, plankton, and chunks of polar bear poop. Don’t eat the ice.
4. Young ice is thin, physically unsound, and drifts around with the breeze. It’s quite willing to melt if the conditions are right, and everybody else is doing it.
5. Old ice is fat, lumpy, rigid, and sedentary. It is uncooperative with melting or most other forms of weight-loss. Naturally.
6. The best way to make sure your tax-supported research says what you want it to is to change the data recording parameters. Then change the definitions. Then change the subject.
This climate stuff is starting to look easy. I think I need a nap.