What is the "Larsen-B ice shelf" and why is it breaking up so rapidly?
In Antarctica, the glaciers flow off the continent and they form a little lip which floats on the ocean nearby, and that little lip, that floating lip of ice, is called an ice shelf. Ice shelves don't cause sea levels to rise themselves when they disintegrate because they're like the ice cubes in a glass of water; they just melt away and the level stays the same. However, they do have an important function which is that they jam the ice behind them onto land. They apparently are so jammed onto the edge of the continent that they block the ice in the glaciers on land from flowing into the sea. If you took a bottle of ketchup, put it on its side, and took off the cap, that's a lot like what happens to the ice in Antarctica if you melt or disintegrate the ice shelves. It's like taking off the cap. What's happened to the Larsen ice shelf is that a chunk of it the size of the state of Rhode Island disintegrated a few years ago all in the space of a few weeks due to melting at the surface. It's then allowed the glaciers to run into the ocean and those glaciers, because they're on land and not floating on the sea, actually contributed in a measurable way to sea level rise. Now, it's not a catastrophic thing, but there are much larger ice shelves farther to the south of Antarctica which are buttressing, penning in, or capping much larger glaciers called ice streams. We're concerned that if the warming proceeds to the south and knocks out those bigger ice shelves, then we'll see a very large sea level rise; one that could reverberate worldwide and really have catastrophic consequences.
