10/31 NEWS: See updated graphs here
UPDATED: 10/22/08 The new images below are even closer
Watching arctic sea ice rebound this year has been exciting, more so since a few predictions and expeditions predicated on a record low sea ice this past summer failed miserably. I’ve spent a lot of time this month looking at the graph of sea ice extent from the IARC-JAXA website, which plots satellite derived sea-ice extent. However, there is another website that also plots the same satellite derived data, the Nansen Environmental and Remote Sensing Center of Bergen Norway, and they have an added bonus: a standard deviation shaded area. For those that don’t know what standard deviation is, here is a brief explanation from Wiki
…standard deviation remains the most common measure of statistical dispersion, measuring how widely spread the values in a data set are. If many data points are close to the mean, then the standard deviation is small; if many data points are far from the mean, then the standard deviation is large. If all data values are equal, then the standard deviation is zero.
In a nutshell, you could say that any data point that falls within the standard deviation area would be considered “within normal variances” for the data set. That said, current sea ice extent and area data endpoints (red line) are both approaching the edge of the standard deviation (gray shading) for both data sets. Here is sea ice area:
Click for a larger image
And here is sea ice extent:
Click for a larger image
Extent has a bit further to go than area, and of course it is possible that the slope will flatten and it may not reach the SD gray area. It’s also possible it may continue on the current trend line. Only nature knows for certain. A complete presentation from Nansen is on this page which is well worth bookmarking.
What I find particularly interesting is the graph comparing the 2008, 2007, and 2006 sea ice extent. It appears 2008 extent has already bested 2006 extent:
with a hat tip to commenter Patrick Henry
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kim (09:25:40) :
“If NASA’s source for your graph is CU, why don’t they have the intervening data points that are on my graph?”
That’s explained above, the Uni Col were having issues with processing the data. The La Nina can reduce global sea level due to the cooling of the surface of a very large area of sea water. If you look at a globe you will see the Pacific Ocean covers half the earths surface, the increased trade winds result in more evaporation that cools the surface very effectively (think of a breeze on sweaty skin). This cooling will result in a temporary drop in SL but the actual SL during the dip is higher than it was in the beginning of 2006.
The stored heat in sub surface currents are becoming a little more understood, though still very sketchy. This paper http://www.nature.com/ngeo/journal/v1/n10/full/ngeo316.html
shows the effects of the relatively warm subsurface water on Greenland fjordic glaciers. Look at fig. 4, it shows how quickly the warmer sub surface water entred the system. This warmer sub-surface water has to be a contender for the dramatic melting of the Arctic ice sheet. Evidence is only circumstantial butit was worth looking at the ice extent anomoly graphs to see the pattern of much reduced ice coverage since 2001 coinciding with the flat temperature trend over the same period. http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg
I had looked at your link but I still prefer in some cases to trust other dynamic models and to look at what the SST and SL tell me. The Australian sources have proven to be the most accurate, mainly because they are the ones who directly feel the effects!
Mary Hinge (10:53:40) Surface cooling will not thermally contract enough water to lower sea level, at least not within our capacity to measure it. You’ve not convinced me that the La Nina cooling penetrated deeply enough to lower sea level. I think the lowering of sea level is from thermal contraction and my rationale is the four years of slight oceanic cooling to two miles deep as measured by the Argos buoys. I agree, though, that if your two orphaned data points have validity, then maybe sea level isn’t dropping.
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Furthermore, the four years of oceanic cooling to two miles deep corresponds to the approximately four years of cooling seen in the atmospheric temperature trends. I don’t think individual Las Ninas or Los Ninos have much effect on sea level. Now, the PDO, that is another thing. Too bad we don’t have TOPEX/Jason back to the last time that the PDO was in a cooling phase.
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Nitpicking here, but your link is to ice area anomoly, not ice extent. Don’t be confused.
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Note, too, the ice area anomoly rising dramatically again back toward the mean of the last thirty years, with little chance of it turning back around again, soon, unless your Los Ninos come out of nowhere. This is, of course, a very short term trend, so far. The Antarctic surprised me this last SH winter.
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/// Rob (16:40:49) :
Sea ice area approaching the edge of normal standard deviation Oct 2008,
Do you actually believe this BBC garbage, of cause you don`t. //
I don’t always believe the BBC and I certainly don’t believe much of the garbage posted on here but I do give some credence to current data rather than the cherry-picked data that some people on this site worship. They denigrate ANY data that counters their belief, calling it unreliable, but then have the brazen cheek to use the data from the same sources as definitive proof if the data agrees with their beliefs over a selected period. I like to keep an open mind so maybe this board is not for me.
kim (13:01:36) :
” Surface cooling will not thermally contract enough water to lower sea level, at least not within our capacity to measure it. ”
An efficient cooling mechanism such as evaporation will if over a sufficiently large area, don’t forget how large an area the Pacific covers!
“I don’t think individual Las Ninas or Los Ninos have much effect on sea level”
As further evidence look at the 1997-1998 levels where the sea levels rose during that strong El Nino.
“Now, the PDO, that is another thing.”
As has been discussed before the PDO phases are in effect neutral, it is their effect on ENSO that determines temerature changes.
Mary Hinge (05:42:07) There would be less evaporation during a La Nina than during an El Nino. You have something backward here.
And if Jason’s data is not available, whence the two orphaned dots on your sea level graph? Also, see the latest thread for more doubt about 3.4mm/yr rise.
You are simply not persuasive, sorry. I’m sure you’ve convinced yourself.
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Dennis Ward,
If you really have an open mind, you should stay since you can see and hear both sides here. If, however, you prefer an echo chamber with the same old ideas bouncing around forever, there are many, many sites you can go to. I would recommend Real Climate. Of course if you make a comment there like the one you just did here, it will be promptly deleted. So make sure you hold up the party line there.
Thanks for visiting,
Mike Bryant
kim (07:15:51) :
Try not to think in one dimension for a change. At first glance it would seem logical to assume that a warm water event results in more evaporation than a cool event. Bear in mind that the air above the initial upwelled cold sub-surface water is cooler and drier than during a neutral or El Nino episode. There is also an increase in the trade wind speed, put the two together and this results in greater evaporation (using the body sweat anology again, if you work out in cool, dry air the sweat evaporates very quickly, in humid conditions the sweat doesn’t evaporate as fast). But don’t take my word on it, this is the important part of this paper :
Gautier C. Peterson P. and Jones C. Global Estimation of Freshwater Fluxes and Freshwater Oceanic Transport from Satellite Data, World Water Resources Vol 8, No. 4 pg 505-514.1996
“Evaporation exceeds precipitation by about 200 cm year-1 during the La Niña conditions of 1988-89, whereas precipitation exceeds evaporation by about 200 cm year-1 during the El Niño of 1991-92.”
“And if Jason’s data is not available……”
If you don’t believe the data, fine. Whatever data anyone, or any organisation presents that goes against your preset ideas you’re going to ignore anyway.
“You are simply not persuasive”
With your answers revealing your thought processes, I really couldn’t care less
Mike Bryant (07:39:45) :
“Dennis Ward,
If you really have an open mind, you should stay since you can see and hear both sides here. ”
I am in total agreement with Mike here Dennis (put that in a diary as a red letter day!). There is nothing like healthy debate to help you learn about what is a very complex subject. A lot of posters do produce good sources of information and it all helps stimulate the intellectual juices!
Mary Hinge (08:41:08) Look, they tell us that the data from Jason is problematic, then put out two data points off in isolation that are not in line with the other data, and you expect me to be persuaded?
Also, if the Los Ninos and Las Ninas do effect the volume of the ocean, and hence the sea level, it looks to me like the volume and sea level change precede the atmospheric manifestation. So you have your causality backward. I wish I could remember who said ‘The climate is the continuation of the ocean by other means’.
I’ve been studying this stuff for several years, now, and my understanding and beliefs have undergone a number of sea changes. Can you say the same about yourself? When are you going to question your underlying assumption that climate is exquisitely sensitive to CO2. How cold does it have to get?
I’m just a little amused that a true believer like yourself criticizes a skeptic like myself in the manner you have. You’ve got that part backwards, too.
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Mary, when you consider that the heat content of the oceans is very much greater than the heat content of the atmosphere, it seems that you ought to know better than to argue that the atmosphere heats and cools the oceans rather than the other way around. So, what about it?
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kim (11:53:53) :
Mary Hinge’s thought processes may be revealing about her apparent lack of blog etiquette.
edcon (13:03:38) Someday she’ll learn that insults are a hallmark, but not a pathognomonic sign, of a failing argument. I’ve run into so much bluster and bluff from true believers on other boards that I take it as a sign of weakness. It may not be in this case(what is sea level doing, anyway) but it is certainly suggestive.
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kim (12:05:00) :
“….it seems that you ought to know better than to argue that the atmosphere heats and cools the oceans….”
I assumed you had at least a basic idea of heat transfer in dynamic systems. No where did I say the atmosphere heats the ocean, I did say that the atmospheric conditions will affect the rate of ocean cooling, surely you agree with that!
“Furthermore, the four years of oceanic cooling to two miles deep …….”
Do not confuse metric and imperial measurements, a common source of errors in junior school classes, use km and not miles . Argo/Argos meaurements are what you must be referring to, homepage here http://www-argo.ucsd.edu/
These measure the upper 2km depth of the oceans and, because of the sea ice, there are fewer Argo bouys in the Arctic and Antarctic waters. Another factor to remember is that the average ocean depth is 3.5km.
edcon (13:03:38) :
“Mary Hinge’s thought processes may be revealing about her apparent lack of blog etiquette.”
I have not insulted Kim at all, read the posts! It is up to the reader to determine the thought processes, I can see what she is doing, I am sure others will to. Why are you so sensitive?
Sometimes I think I am in a scientific debate instead of a blog. It is only when your debatee constantly fails to provide any evidence for their argument, uses false quotations and mixes up imperial and metric measurements then you realise this is just a blog.