NSIDC Arctic Sea Ice Extent – click to enlarge
Arctic sea ice has retreated significantly in recent years, reaching a record low in September 2007. It is known that the seasonal cycle in Arctic sea ice extent is not symmetric—seasonal ice retreat proceeds gradually during early summer and then accelerates toward end of summer, while in winter, ice growth is rapid at first and then slows later in the season. Scientists have observed that ice cover has retreated far more rapidly in September than during other times of the year.
Some scientists have suggested that this seasonal asymmetry is due to factors such as temperature changes. However, Eisenman finds that the seasonal differences in rate of ice growth or retreat are caused by the geometry of the landmasses surrounding the Arctic Ocean. Because the Arctic Ocean is mostly surrounded by land, coastlines block the southward extent of sea ice growth during the winter, but coastlines have little effect on the extent of ice during the summer.
The author suggests that to better interpret changes in Arctic sea ice, instead of considering sea ice areal extent, scientists should track the line marking the latitude of the Arctic sea ice edge, averaged zonally over locations where the edge is free to move. He finds that this line moves northward or southward at a steady pace over the course of the year, with no seasonal asymmetry. In recent years, this line has been migrating northward at a rate of about 8 kilometers (5 miles) per year, consistent with overall ice loss. The study explains some aspects of the seasonal Arctic sea ice cycle and could help scientists better interpret sea ice evolution in the future.
Title: Geographic muting of changes in the Arctic sea ice cover
Author: Ian Eisenman: Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA and Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA.
Source: Geophysical Research Letters (GRL) paper 10.1029/2010GL043741, 2010 http://dx.doi.org/10.1029/2010GL043741
==============================================
Here’s the abstract:
GEOPHYSICAL RESEARCH LETTERS, VOL. 37, L16501, 5 PP., 2010
doi:10.1029/2010GL043741
Geographic muting of changes in the Arctic sea ice cover
Ian Eisenman
Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA
Department of Atmospheric Sciences, University of Washington, Seattle, Washington
The seasonal cycle in Arctic sea ice extent is asymmetric. Its amplitude has grown in recent decades as the ice has retreated more rapidly in summer than in winter. These seasonal disparities have typically been attributed to different physical factors operating during different seasons. Here we show instead that the seasonal asymmetries in Arctic sea ice extent are a geometric consequence of the distribution of continents. Coastlines block southward ice extension during winter, thereby muting changes in ice extent, but they have relatively little effect at the time of summer minimum extent. We suggest that the latitude of the Arctic sea ice edge, averaged zonally over locations where it is free to migrate, is the most readily interpretable quantity to describe the Northern Hemisphere sea ice cover. We find that the zonal-mean sea ice edge latitude during the 1978–present era of satellite measurements has been following an approximately sinusoidal seasonal cycle that has been migrating northward at an approximately annually constant rate of 8 km/year. These results suggest a change in perspective of the most critical quantities for understanding changes in Arctic sea ice.
http://www.agu.org/pubs/crossref/2010/2010GL043741.shtml
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My big question would be to Judith Curry, if she happens to drop in on this thread:
How does the AAC affect/interact/limit the Antarctic Sea Ice?
Tamino discussed this rather extensivly:
http://tamino.wordpress.com/2010/08/22/on-ice-with-a-twist/
This is the explanation, as per WUWT’s regular M.Vukcevik:
http://www.vukcevic.talktalk.net/AT-GMF.gif
If at first you don’t succeed, try try again.
I guess since ice thickness and rotten ice are no longer in the picture, zonal averaged whatnots must be found.
We need to see the data; or maybe it is a model thing once more?
I am curious how cherry picking can be avoided in an area with so many lace like landmasses when one defines “northwards” and “soutwards”.
Retreat is faster in early summer than late summer. It takes about 10 seconds looking at any of the graphs to realize that maximum rate of retreat occurs when the sun is highest. In September the sun is low and retreat occurs more slowly.
Well, it’s older name is “The Great Polar Basin”, isn’t it? What’s in a name? A clue?
It’s also the shallowest by far of all the oceans and the smallest.
Landmass shape affects extent of Arctic sea ice
Think next time, a deeper research, will blame Whiskey instead.
“Arctic sea ice has retreated significantly in recent years, reaching a record low in September 2007”
No it didn’t, it reached a 30+ year low. The record low is none.
Curiously Eisenman means “The Man of the Ice”
This study is like throwing money at a proposal to discover that warm loving birds migrate in the winter. Of course land edges affect ice movement. What would be far more interesting is to study Arctic current affects from El Nino waters since 1978 as well as the AO pressure patterns (IE wind direction) with this northern migration of the ice edge in September. Bet the migration of the Northern edge is weather and oceanic current related and could be modeled without the assumed warming of CO2.
And what about the multiyear ice?
If the area were more, but it was all new ice, how would this compare with less ice but mostly multiyear? The first would indicate a more dynamic system, while the other would appear to have less drastic extremes.
It did not take long for Seth Borenstein to plot with Serreze another alarmist garbage and for the newly fully owned by Bell Canada and Thomson family -the richest Canadians- Globe and Mail, to repost it:
http://www.theglobeandmail.com/news/world/melting-sea-ice-forces-walruses-ashore-in-alaska/article1705659/
How about lower layers atmospheric circulation and how relief above 1500m do affect it? This is already well known to those who read Leroux…
“The results suggest…”. I thought the science was settled?
Maximum rate of retreat occurs near the end of June. How curious.
Because we are getting closer to an ice-free Arctic (giggle), the Sea Ice Extent graphs should really be scaled from 0.0 to 16.0 million, not 4.0 million to 16.0. Then we can watch the decline.
I have a similar problem with my icemaker. There’s this little wire thingie that keeps ice from being produced when the bin is full. I suspect it’s controlled by freezer warming.
Pamela Gray says
“…What would be far more interesting is to study Arctic current affects from El Nino waters since 1978 as well as the AO pressure patterns (IE wind direction)…”
Yes, exactly. It’s all about the wind. Which way is the wind blowing? How hard, and for how long? The wind piles up the ice and snow when it blows towards the land and thins it when it blows towards the sea. It has nothing to do with temperature. That’s why all those global warming people make such idiots of themselves by actually going to the Arctic in (yet another) attempt to prove that the Arctic is becoming “ice-free”. They can consider themselves lucky to get out of there alive.
It is time to find a name for these non-studies that are only a shallow re-evaluation of old data designed to lead to a misrepresentation of reality. I wonder how many of the “millions” of “peer” reviewed papers the greenies always talk about are deliberate attempts to generate greenie headlines and have nothing to do with science?
Suspiciously these things are occurring near Alaska…..hmmmm….
Hush! don’t say anything!. Just go to WUWT and there you’ll find the real cause:
http://www.vukcevic.talktalk.net/AT-GMF.gif
I don’t get it how these deniers have an answer for everything, was it not supposed they are dumb and we are wise?, at least my mommy told me so….
Enneagram says: September 13, 2010 at 11:29 am
This is the explanation, as per WUWT’s regular M.Vukcevik:
http://www.vukcevic.talktalk.net/AT-GMF.gif
Or here is a version with few more details:
http://www.vukcevic.talktalk.net/NFC1.htm
Enneagram says: “Curiously Eisenman means “The Man of the Ice””
Actually, it means Iron Man. Similar to Eisenhower, a hewer of iron.
Duh. The geographic constraint is obvious by inspection of the sea ice area charts. The lines pass thru or close to “knots” at around mid-May and mid-November every year.
jorgekafkazar says:
September 13, 2010 at 1:41 pm
However the German prefix EIS means ICE. It would really mean the Ice-cream salesman 🙂 (because the suffix mann denotes craftmanship or occupation, like in gold-mann )
No Enneagram,
Here you are wrong.
I am a native German speaker, so I should know 🙂 .
The prefix “Eisen” means simply Iron. The suffix “mann” just means ‘man’, nothing else. It has nothing to do with craftmanship or occupation. Eisenmann literally means Iron-man.
If it were “man of the ice”, it would be “Mann des Eises”. Ice-man would be Eismann, but not Eisenmann.