|Antarktisk udtynding af "Ice Shelf"...29-03-2007 23:52|
|Antarctic ice sheet 'thinning'|
From correspondents in Houston
March 29, 2007 10:33am
A PIECE of the Antarctic ice sheet the size of Texas is thinning, possibly due to global warming, and could cause the world's oceans to rise significantly, polar ice experts say.
|Tak for linket, Gorm. Meget interessant. Det fik mig til at grave min atlas frem!|
Også til at grave lidt på nettet; fandt kilden her:
'Thinning Antarctic ice needs improved monitoring to reduce uncertainty over sea-level rise' (28/4):
Interessant var " The consensus view of the workshop"
Også 'Animation of Larsen B breakup, 31 January to 7 March'
"See also" øverst hjørne til højre)
"The limitations of ice sheet models were revealed starkly by the collapse of the northern sections of the Larson B ice shelf in 1998 and 2002. Glaciers bounded by the landward edge of the ice shelf accelerated toward the sea while glaciers bounded by the more southerly section of the ice shelf, which remained intact, didn't. Apparently, backpressure on glaciers from the abutting ice shelf provides a significant portion of the restraining forces keeping land-based ice in place, at least in some instances. The recent behavior of glaciers farther south in West Antarctica, and in Greenland, points to a similar dynamical response to ice-shelf fragmentation.
Many glaciologists regarded these observations as a clear test of the ability of ice sheet models to forecast dynamical changes in a warming ice sheet, a test the models failed. The long-standing inability of ice sheet models to reproduce the ice streams of West Antarctica, unexplained dynamical contributions to the mass balance of the Greenland ice sheet during the late 1990s and its apparent basal response in one location to surface melt-water reinforced this skepticism."
"4. Finally, there is another way how ice sheets can contribute to sea level rise: rather than melting at the surface, they can start to flow more rapidly. This is in fact increasingly observed around the edges of Greenland and Antarctica in recent years: outlet glaciers and ice streams that drain the ice sheets have greatly accelerated their flow. Numerous processes contribute to this, including the removal of buttressing ice shelves (i.e., ice tongues floating on water but in places anchored on islands or underwater rocks) or the lubrication of the ice sheet base by meltwater trickling down from the surface through cracks. These processes cannot yet be properly modelled....."
Hvordan udviklingen bliver i virkeligheden vil tiden vise..
Vi har hørt varslerne. Klokken tikker....Informerede valg.
Redigeret d. 08-04-2007 21:30
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