WunderBlog Archive » Dr. Ricky Rood's Climate Change Blog

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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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