I just saw this on Yahoo's news list:
Study Shows Antarctic Glaciers Shrinking
About the only good news here is that the glaciers in question represent a fairly small portion of the Antarctic ice sheet -- the Antarctic Peninsula in the northernmost part of the continent. Even there, the process is a little disturbing, because this is an area of Antarctica that is uniquely susceptible to ice melting as a result of local climate change.
More below:
The changes observed in the Antarctic Peninsula are quite striking:
Researchers from the British Antarctic Survey and the U.S. Geological Survey analyzed more than 2,000 aerial photographs dating from 1940 and more than 100 satellite images from the 1960s onwards.
They calculated that 87 percent of the 244 glaciers going out to sea from the peninsula have retreated during the last 50 years and that the pace of shrinkage has accelerated in the last decade. Until now, scientists were uncertain whether the glaciers were growing or melting.
"Fifty years ago, most of the glaciers we look at were slowly growing in length but since then this pattern has reversed. In the last five years the majority were actually shrinking rapidly," said the study's leader, Alison Cook of the British Antarctic Survey.
Five out of six glaciers on the peninsula have retreated.
What does this have to do with global climate change? For one thing, sea level rise. The amount of water from retreating glaciers in the Antarctic Peninsula is fairly small. However, much of the continent near the Antarctic Peninsula is thought to be a place where significant ice melting can occur fairly quickly.
A little geography first. Antarctica is divided into two regions, Western and Eastern Antarctica, by a wide mountain range. The Antarctic peninsula is located in the Western portion, further north than most of the continent:
One interesting aspect to the ice there is the ice tied up in the ice "shelves" -- the dark-blue regions in the Ross and Weddell Seas on the map above. It turns out the ice in these ice shelves is dynamically unstable -- that is, it will tend to either grow dramatically or shrink (melt) dramatically, with no middle ground. A gradual collapse of the entire ice cap in the area is possible, as ice from higher elevations moves in to replace the ice over the ocean. In this case, most of the ice in Western Antarctica could disappear over a few centuries' time. For further background, there is an excellent lay summary of the Antarctic ice sheet here.
The good news is that melting in Eastern Antarctica is unlikely -- it's too cold and dry there, and there are fewer outlets for that ice to reach the sea. The really bad news: if the ice cap on Western Antartica melts, it will contribute approximately 5 meters (16 feet) to sea level, if it were all to melt. It would take centuries to do so, but even so, that is an enormously worse scenario than any others being seriously considered. As a result, just about any warming in Western Antarctica is worth watching very closely.
Fortunately, right now it's just the peninsula that's showing unusual melting. The rest of Western Antarctica is not so clear, and in any event it will take still more warming to cause the serious scenario I mention above. However, one thing we've learned from the past is that these sorts of changes are rarely confined to a small region.
Thoughts?
