By: Dr. Ricky Rood , 4:14 AM GMT on February 25, 2007

I love the comments and questions...nice to see people returning and some new people showing up. Promised something about melting ice, our evolving understanding of how ice can melt rapidly. Here are two pictures from NASA Goddard's Scientific Visualization Studio. They show the Larsen Ice Shelf in the Antarctic Peninsula. These figures have been seen around a lot.

Figure 1.From NASA Goddard Scientific Visualization Studio: Larsen Ice Shelf 31 January 2002. Note pools of water on the ice.

Figure 2.From NASA Goddard Scientific Visualization Studio: Larsen Ice Shelf 7 March 2002. The shelf has collapsed with ice bergs moving out to sea.

An ice shelf is where a glacier is flowing into the sea. It is grounded on rock on the sea floor. Over the course of a couple of months this ice shelf collapsed; it is believed to have existed since the last ice age. What I first want to point out is that in the first figure the ice has pools of water on its surface. When there is melting on the surface the water starts to infiltrate down into the ice, flowing through, causing fast melting. In this way sustained surface melting greatly influences the stability of the ice.

Recently Richard Alley from Penn State has developed an elegant description of ice sheets and how they are maintained and how they melt. The basics of the idea are to imagine the ice as a pile, similar to pancake batter placed in the middle of a pan. The batter will try to spread out. If it is runny batter you might try to put a spatula around the edges to hold the batter together, to slow the spreading. So the ice shelf is like the spatula; it sits in the ocean grounded on the sea floor, and helps to hold the ice on the land. Another metaphor that you can imagine is a flying buttress on a Gothic Cathedral, which basically holds up the piles of rock which make up the walls. So this entry describes two pieces of the ice melting puzzle: the presence of water infiltrating and melting the ice and the loss of the ice shelf which helps to hold the ice on the land. There's more.

This type of metaphor is often used in science; it's a heuristic or conceptual model. They help us build and analyze the physical models used to quantify processes and make predictions.


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22. LowerCal
10:38 PM GMT on February 27, 2007
When ice on land is no longer held there it raises sea level just as much as if it had melted. Statements that it would take centuries(?) for it to melt don't tell a critical part of the story ... and there's even more?
Member Since: July 26, 2006 Posts: 59 Comments: 10336
19. desertdisaster
1:56 PM GMT on February 27, 2007
During that time, somwere else in the word...
Drought in southwestern China is threatening the drinking water supplies of 1.5 million people and authorities are considering seeding clouds to make it rain, state media said on Tuesday.

The problem has been compounded by last summer's heat wave in the densely populated municipality of Chongqing, as water supplies have still not recovered, the Beijing News said.

More than 10 ships that ply the Yangtze River have been stranded by the low water levels, it added.

Some parts of Chongqing -- home to some 30 million people -- have started limiting water supplies to residents and are drilling new wells to find underground sources of water, the report said.

Last summer's drought was the worst to hit southwest China in more than a century, when temperatures topped 40 degrees Celsius (104 F), and about 18 million people faced drinking water shortages.

Can't wait to see summer 2007...wich should breake all previous records of extreems!

15. desertdisaster
4:51 PM GMT on February 26, 2007
This exciting discovery of large lakes exchanging water under the ice sheet surface has radically altered our view of what is happening at the base of the ice sheet and how ice moves in that environment...

A lot more here:Link
10. Fshhead
8:07 PM GMT on February 25, 2007
Buster I think we know what would happen if this occurred. In my opinion the tsunami that hit Asia would be small in comparision & we saw the damage it created. The whole Atlantic coastal basin would be in SERIOUS trouble.
Member Since: November 19, 2005 Posts: 9 Comments: 9960
8. Dr. Ricky Rood , Professor
4:50 PM GMT on February 25, 2007
Let's nuance it a little. Yes the ice shelves are in water,they rise and fall with tide, but they still "see" the bottom and shore and, hence, are anchored near the shore. They have much more push back on the glacier than ice only floating in the water. Once in the water, they are sensitive to more rapid melting.
Member Since: January 31, 2007 Posts: 376 Comments: 393
7. Snowfire
4:29 PM GMT on February 25, 2007
I beg to differ on one point: an ice shelf is not grounded on the sea floor. It is afloat, by definition. This is why large pieces can crack off and drift away so easily. They are the source of the giant "tabular" icebergs which are common in the Antarctic (but much rarer in the Arctic). There are tidewater glacial fronts which are in fact grounded on the bottom, such as the Steenstrups front in Greenland; but these do not form tabular bergs. Instead, they calve into the ocean to form icebergs of the more ordinary kind.
Member Since: June 29, 2005 Posts: 24 Comments: 315
6. Dr. Ricky Rood , Professor
3:16 PM GMT on February 25, 2007
Here are some other places to look at images of ice and snow. Here are images of Ice Shelves and Icebergs from the National Snow and Ice Data Center. For those so inclined, you can get data from this data center and do your own investigations. Here are a set of images from a single instrument, the Moderate Resolution Imagining Spectroradiometer (MODIS).
Member Since: January 31, 2007 Posts: 376 Comments: 393
4. ricderr
1:12 PM GMT on February 25, 2007
CB...stand underneath it and give us a first hand report please
Member Since: June 27, 2006 Posts: 688 Comments: 24003
2. Fshhead
9:17 AM GMT on February 25, 2007
Has anyone seen the satellite pics of the ice shelf collapsing in northern Canada??
Member Since: November 19, 2005 Posts: 9 Comments: 9960
1. Flakeman
4:40 AM GMT on February 25, 2007
Been lurking here. Does that Fast Ice go well with sloe gin ? :P
Member Since: March 3, 2006 Posts: 9 Comments: 375

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