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At Roger Pielke Sr.'s blog entry:

As discussed on Climate Science, when climate metrics are investigated in detail, the reality of the real world often conflicts with the pronouncements of the climate assessments. With respect to glaciers, this mismatch between reality and the assessments has been presented before (see and see).

The weblog for today provides yet another example of the incomplete information that is being communicated to policymakers and others.

An article in the November-December 2006 issue of the Earth Observer entitled “The GLIMS Glacier Inventory of the Antarctic Peninsula” by Frank Rau,  Jeffrey S. Kargel,  and Bruce H. Raup provides an update on the recent behavior of glaciers in the northern Antarctica peninsula (see the November-December pdf on pages 9-11). This is a region where significant regional surface temperature warming has been recorded.

An excerpt from their article, however, shows that the response of the glaciers is more complex in response to this reported regional warming. They write,

“Analysis of high resolution ASTER data co-registered to Landsat Thematic Mapper ™ and Enhanced Thematic Mapper Plus (ETM+) data provide information on glacier front variations between the years 1986 and 2002. In regional case studies, more than 300 glaciers were examined, covering a variety of glacial systems distributed over the northern Antarctic Peninsula. Of these, only 40 (12.8%) displayed advancing glacier fronts accounting for a gain of 7.1 km², while 171 (54.6%) showed retreating ice fronts accounting for a loss of 146.1 km². In addition, 102 (32.6%) were found to be in invariant conditions. The glaciers examined displayed no indications of dynamic flow instabilities. The observed glacial variations are therefore interpreted as direct consequences of the rapidly changing climatic conditions in the region that are affecting accumulation and ablation.

Beyond the overall trend toward retreating ice fronts, observations dating from the mid 1980s to 2001 reveal different patterns of glacier variation across the Antarctic Peninsula. An area of significant retreat is concentrated on the northeastern sectors of the peninsula-- eastern coast of Trinity Peninsula and James Ross Island. Similarly, a consistent distribution of predominant glacial recession is also identifiable along the southwestern coasts of the study area--Graham Coast, Loubet Coast and Marguerite Bay. Thisis in sharp contrast with glacier frontal positions recorded in northwestern parts of the Antarctic Peninsula adjacent to Bellingshausen Sea, where only slight recessions and minor advances were recorded--western coast of Trinity Peninsula and Danco Coast. These observations from the northwest, which are presumed to be in the natural range of frontal fluctuations of tidewater glaciers, suggest relative dynamic stability of the glacial systems in this sector.”

This article indicates that 45.4% of the glacier fronts are either advancing or are invariant over the period from the 1980s to 2001. While the retreating glaciers have lost more area than has been gained by the advancing glaciers, this also need to be placed in context of the total area of the glaciers in this region (which was not done in this article).

Nonetheless, even without that information, the general message that glaciers are receding almost everywhere is clearly not accurate when the data is evaluated in detail.

by Nomad (Bjinse) on Mon Feb 12th, 2007 at 04:16:10 AM EST
To compare & contrast, this is what the IPCC's summary for policy makers says on the topic:
Mountain glaciers and snow cover have declined on average in both hemispheres. Widespread decreases in glaciers and ice caps have contributed to sea level rise (ice caps do not include contributions from the Greenland and Antarctic ice sheets)

New data since the TAR now show that losses from the ice sheets of Greenland and Antarctica have very likely contributed to sea level rise over 1993 to 2003 (see Table SPM-1). Flow speed has increased for some Greenland and Antarctic outlet glaciers, which drain ice from the interior of the ice sheets. The corresponding increased ice sheet mass loss has often followed thinning, reduction or loss of ice shelves or loss of floating glacier tongues. Such dynamical ice loss is sufficient to explain most of the Antarctic net mass loss and approximately half of the Greenland net mass loss. The remainder of the ice loss from Greenland has occurred because losses due to melting have exceeded accumulation due to snowfall.

I see no 'mismatch' here. The report clearly states that glaciers are retreating 'on average' and notes the relative balance between the melting of ice and increased precipitation in Antartica and Greenland. Clearly, the glaciers on the Antartic peninsula are also retreating on average.

A map of the peninsula can be found here. Note that the 300 glaciers represented in the study are all 'case studies' that do not necessarily represent more than a sample of the total glacier area (the question by Pielke Sr. about the significance of the loss in the context of the total glacier area would otherwise probably have to be answered with 'miniscule').

by nanne (zwaerdenmaecker@gmail.com) on Mon Feb 12th, 2007 at 02:11:36 PM EST
[ Parent ]
  1. Beyond what nanne says about the supposed claim of all glaciers receding, I don't understand why Roger Pielke Sr. didn't further consider the stark regional differences. Could it be that local geologic features ensure a 'heat insulation' for glaciers there? Say, shielding by the South Shetland Islands?

  2. Why does the ratio of glacier surface loss to total glacier area matter? The way I understand it, the mass loss of a glacier is in significant part thinning, not just shortening.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Wed Feb 14th, 2007 at 09:12:14 AM EST
[ Parent ]


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