Antarctic Ice Shelf Melting Influenced By Warming Ocean Water - NASA

[hatrack]

EDIT

"On average, Antarctic Peninsula (AP) ice shelves have retreated by ~ 300 km2 each year since 1980. This gradual retreat has been punctuated by two catastrophic collapses, in January 1995 and February 2002, when the remaining northern sections of the Larsen Ice Shelf fragmented into icebergs. In contrast to the prolonged retreats, these 2,000 and 3,250 km2 ice shelf sections disintegrated over days or weeks. Although the initial retreats of their ice fronts may have resulted from iceberg calving beyond stable geometrical positions, it is not clear this explains the wholesale disintegration of large ice shelf sections. Speculation as to the mechanism that caused the final collapses has concentrated upon the destabilising effects of increased surface melt-water, which may have enhanced the process of crevasse fracture. Whilst that mechanism provides a link between the regional climate warming and the break-up of ice shelves at the AP, direct observations are insufficient to determine the importance of ice shelf stability criteria or the impact of increased surface melt.

We used 9 years of ERS satellite radar altimeter measurements to determine the surface elevation change of the LIS since 1992 (Fig. 1). Between 1992 and 2001 the mean rates of elevation change of the Larsen-B and -C ice shelves were -0.17 ± 0.11 and -0.08 ± 0.04 m yr-1. In general, the northernmost sections of the Larsen-C experienced the greatest decrease in surface elevation, with a peak rate of lowering of 0.27 ± 0.11 m yr-1 some 10 km south of Churchill Peninsula.

EDIT

We find this conclusion, which requires unbalanced basal melting of 0.78 m yr-1, is not unreasonable given what oceanographic data there is. Recent measurements showed large quantities of modified Weddell Deep Water (a source of which has warmed for several decades) present in front of the northern Larsen-C at depths well below the ice shelf draft. Elsewhere such ocean-ice temperature differences generate basal ice melting well in excess of that we have estimated when water is delivered to the ice shelf base. If our estimate of the basal erosion rate is correct, the Larsen-C will approach the thickness of the Larsen-B at the time of its collapse in some 100 years; more rapidly if the rate is increased by a warming ocean. It is possible that the LIS thinning provides a link between the regional climate warming and the disintegration of ice shelves at the Antarctic Peninsula."

EDIT/END






http://igloo.gsfc.nasa.gov/wais/abstracts03/Shepherd.html

[trotsky]

1. Evolution of right-wing naysaying

"There is no such thing as global warming."

to

"Global warming may exist, but humans aren't the cause."

to

"Global warming appears to exist, humans may be contributing, but natural cycles are far more to blame."

Slip-slidin' awaaaaaaay...

[Gman]

2. Whoa! Wrong answer for Karl Rove... Their heads

will be presented on a platter. How dare a government agency proclaim the blasphemy of global warming??? Off with their heads! Make them an example!!! Call Bob Novak!

[TreasonousBastard]

3. Look at a map of Antarctica.

The Larsen shelf is a small one. Ross and Weddell are a bit more problematic. They are the only things stopping hundreds of cubic miles of ice sitting on land from slipping into the sea.

I've seen estimates of sea rise from that ice ranging from 6 to 30 feet.

Just think of how much of the earth is less than 30 feet above sea level.

[ramapo]

4. That would make folks take notice

What's the elevation of Washington, DC? Kennebunkport? I think Crawford, TX is >30ft above sea level.