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Post by StuartG on Jul 23, 2011 0:01:41 GMT 1
"Early start to Arctic melt" " When sea ice starts to melt in spring, small ponds known as melt ponds form on its surface. The small pools create a darker surface (a lower albedo) that fosters further melt. How early sea ice melt starts is one indicator of how much the ice will melt in a given year. New research by Don Perovich and colleagues shows that an early start to sea ice melt increases the total amount of sunlight absorbed through the melt season." nsidc.org/arcticseaicenews/ [http://nsidc.org/arcticseaicenews/] ---- doesn't seem to work via proboards "Definition of sea-ice cover (extent and area)" "The area of sea-ice cover is often defined in two ways, i.e., sea-ice “extent” and sea-ice “area.” " "These multiple definitions of sea-ice cover may sometimes confuse data users. The former is defined as the areal sum of sea ice covering the ocean (sea ice + open ocean), whereas the latter “area” definition counts only sea ice covering a fraction of the ocean (sea ice only). Thus, the sea-ice extent is always larger than the sea-ice area. Because of the possible errors in SIC mentioned above, satellite-derived sea-ice concentration can be underestimated, particularly in summer. In such a case, the sea-ice area is more susceptible to errors than the sea-ice extent. Thus, we adopt the definition of sea-ice extent to monitor the variation of the Arctic sea ice on this site." www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm
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Post by marchesarosa on Jul 23, 2011 18:29:16 GMT 1
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Post by louise on Jul 23, 2011 20:35:42 GMT 1
My comment to Principled was that April in the Arctic is not the melting season and so it was not surprising that looking out of an airplane window at that time showed a vaste expanse of ice.
There is probably a very differnt view from that window right now.
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Post by principled on Jul 24, 2011 11:06:50 GMT 1
Louise
And my point was that most non-scientific people who read/view the news media would have believed that there was almost no ice left. The issue is the mental picture that some people deliberately paint in order to frighten others into not questioning the science nor the metrology behind the various hypotheses about ice melts and ice extent. P
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Post by louise on Jul 24, 2011 12:00:25 GMT 1
Louise And my point was that most non-scientific people who read/view the news media would have believed that there was almost no ice left. That's not the point you made - you said Being April (meltiong season) and having read so much about the rapidly retreating ice sheet, I expected to see broken ice sheets intersposed with open sea. I pointed out the April is not melting season, in fact it's not very far off the peak of the freezing season. However, this recent winter did have one of the lowest recorded ice extents for the arctic, but nobody has said they expect an ice free North Pole in the winter, not even the popular press.
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Post by principled on Jul 24, 2011 21:32:37 GMT 1
Louise
That's exactly the point I made. As a non-scientist but one who takes an interest in science I had expected-based on media reports- to see much less ice than there was and also signs of early melting. The fact that someone who is interested in science can be manipulated into believing that the ice extent was SEVERELY affected and that the melting season was coming ever earlier, is evidence enough IMO for my statement about impressions given by the media. P
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Post by StuartG on Jul 24, 2011 21:51:17 GMT 1
On the above post there are two links to the graph seen illustrated elsewhere. These links are the ORIGINATORS of it. I was rather hoping someone might read them and perhaps produce some comment on the area that we are talking about. Also , the ice measurement and area look to me as not being representative of anything near the extent of the ice, regardless of the time of year. Has anyone any idea of when Spring in the Arctic is? Please do read the two leads, decide and then tell the rest. Many Thanks, StuartG radio4scienceboards.proboards.com/index.cgi?action=gotopost&board=witter&thread=819&post=13178
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Post by marchesarosa on Jul 25, 2011 2:37:16 GMT 1
I will try to understand and comment on the difference tomorrow, stu, old thing.
In the meantime, I'm sure Louise and nickRs can explain it to us.
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Post by marchesarosa on Jul 28, 2011 13:49:41 GMT 1
Antarctic ice – more accurate estimatesby Verity Jones @ Digging In The Clay diggingintheclay.wordpress.com/2011/07/27/antarctic-ice-more-accurate-estimates/#more-2246Cracking ice shelves make headlines, but ice loss estimates that are revised downwards don’t. While there is great hand wringing over coastal ice loss in Greenland and the West Antarctic Peninsula, East Antarctica has more than eight times the ice mass of either. East Antarctica lies to the right of the Transantarctic Mountains which cut the continent in half at its 'waist' between the two largest ice shelves. (Location Map from T. Scambos and J. Bohlander. "Images of Antarctic Ice Shelves". National Snow and Ice Data Center: nsidc.org/data/iceshelves_images/index_modis.html)Last week’s Science magazine had a News Focus article on estimates of ice loss in Antarctica. It quietly discussed a paper published in May by two NASA scientists: H. Jay Zwally & Mario B. Giovinetto (2011) Overview and Assessment of Antarctic Ice-Sheet Mass Balance Estimates: 1992– 2009. Surv Geophys DOI 10.1007/s10712-011-9123-5 (note this is Open Access)Estimates of Antarctic ice net variation vary widely. This is in part due to the different methods used, but the magnitude of the change might surprise you. “Mass balance estimates for the Antarctic Ice Sheet (AIS) in the 2007 report by the Intergovernmental Panel on Climate Change and in more recent reports lie between approximately +50 to -250 Gt/year for 1992 to 2009. The 300 Gt/year range is approximately 15% of the annual mass input and 0.8 mm/year Sea Level Equivalent (SLE).”The paper set out to investigate the various estimates, assessing previously published results that used three standard methods which the Science article conveniently summarises: "Each of the three methods has its foibles.
* In the first, altimetry, researchers bounce laser or radar signals off the ice to measure its height and thus its volume. The method has been used to survey most of the continent, but converting changes in volume to changes in mass raises major uncertainties.
* The second technique, gravity, employs the two satellites of the Gravity Recovery and Climate Experiment flying over the ice in tight formation to measure mass directly. But that record goes back to only 2002, and data analysis is tricky.
* Finally, the input-minus-output method (IOM) works by subtracting ice flow into the sea from total snowfall. Both numbers are huge, however, and the mass of snow falling on East Antarctica is especially hard to gauge.”Zwally and Giovinetto’s reassessment also included a challenge to some assumptions, substituting field measurements and making ‘preferred estimates’. These took account of the uncertainties inherent in the various techniques. Their reanalysis provides much lower estimates of net change in ice, ranging from +27 to -40 billion tons per year. For 1992 – 2001 they are prepared to go even further, estimating a loss of only 31 billion tons per year. These still sound like huge numbers, but to put it in perspective, 2400 billion tons of snow falls in Antarctica each year, so we’re dealing with a gain or loss in the range +1.1 to -1.7%. The same techniques applied by the authors in a previous paper (Zwally HJ et al (2011) Greenland ice sheet mass balance: distribution of increased mass loss with climate warming. J Glaciol 57(201):88–102) brought a significant convergence to estimates produced by ICESat altimetry and the GRACE gravity signal in Greenland, however, while the Greenland ice sheet continues to grow inland and thin at the margins, overall recently it has been losing mass. What I find most refreshing is the revision and quantification of uncertainty. What is shocking is not the magnitude of the possible loss, but the short timescale on which the estimates are based and the lack of knowledge of historical data. “The new analysis is a “perfectly reasonable reinterpretation,” glaciologist Andrew Shepherd of the University of Leeds, U.K., says. “The paper’s main contribution is a very convincing argument that one needs to account for uncertainties in a consistent way.” “ The Science article ends by hinting that this may make no more than tiny ripples in the consensus. “Getting more than a feeling for what Antarctic ice is doing to sea level will take more than one group’s reassessment of the published literature, researchers agree. The Intergovernmental Panel on Climate Change (IPCC) is already working on an ice balance assessment for its report due in mid-September 2013, but researchers say more must be done to focus scientists’ attention on the problem.”Does that sound like a dismissal? It does to me. Verity's post can also be found here wattsupwiththat.com/2011/07/27/antarctic-ice-–-more-accurate-estimates/#more-44166
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Post by marchesarosa on Jul 28, 2011 13:53:26 GMT 1
Another paper to be ignored by the BBC's Alarmism Department.
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Post by nickrr on Jul 28, 2011 20:26:36 GMT 1
I was going to reply to the content of this post but it is set out so badly I gave up.
The big chunk of copy / pasted text includes some stuff from WUWT which itself includes quotes, presumably from the original paper with some of MR's comments thrown in.
Not going to waste time trying to work out who said what.
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Post by marchesarosa on Jul 29, 2011 11:05:03 GMT 1
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Post by marchesarosa on Jul 29, 2011 11:26:46 GMT 1
The Science article says
Antarctic Ice's Future Still Mired in Its Murky Past Richard A. Kerr
A new reanalysis by two NASA scientists of the three standard ice-monitoring techniques slashes the estimated loss from East Antarctica, challenging the large, headline-grabbing losses reported lately for the continent as a whole. Although not the final word, the new study shows that researchers still have a lot to learn about the vast East Antarctic Ice Sheet. Understanding the role of East Antarctica is one key to figuring out what the ice sheets, and thus sea level, will be doing by century's end.
Louise in particular will be interested in this NASA paper by Zwally and Giovinetto because she is always trumpeting the accelerating lost of ice round the world and the accelerating catastrophic sea level rise that can be expected, er, umm, sometime in the future.....
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Post by marchesarosa on Aug 8, 2011 19:56:45 GMT 1
There is a debate on Climate Etc, Judith Curry's blog about Arctic Ice. judithcurry.com/2011/08/07/arctic-update/#comments Very interesting. I just found this statement from "Herman Alxander Pope" August 8, 2011 The warm times, when the Arctic is thawed, are when it snows and rebuilds the glaciers. We need these warm times. They are part of the stable cycle. It gets warm and snows more, then it gets cool and it snows less. Back and forth, up and down, in a very stable cycle. The temperature of earth is regulated by ice and water. Albedo goes up when it snows more and down when it snows less. If a trace of CO2 actually makes us a trace warmer, that makes it snow a trace more and cool a trace more and it does not matter.
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Post by eamonnshute on Aug 8, 2011 20:31:33 GMT 1
The warm times, when the Arctic is thawed, are when it snows and rebuilds the glaciers. We need these warm times It is getting warmer, but the glaciers are not rebuilding, just the opposite in fact.
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