Glaciers of East Antarctica less stable than thought?Antarctica is divided into 2 regions, East and

Glaciers of East Antarctica less stable than thought?Antarctica is divided into 2 regions, East and West Antarctica, separated by the Transantarctic Mountains. There are ice sheets in both areas; the West Antarctic ice sheet is smaller, sits at lower elevation, and consequently is believed to be more susceptible to changes in climate than the ice sheet in the east.2800 meters. It’s like a gigantic, flat mountain range.Based on satellite gravity data, there have been some estimates of mass changes in East Antarctica, but so far the data only covers a short time period and doesn’t really seem to show a convincing signal (some groups believe the mass is decreasing, some believe it is increasing much longer data series will likely be required to get an accurate measurement.Because of how remote East Antarctica is and the extreme conditions, there are fewer monitoring stations tracking changes in the ice sheet than there are in Greenland or in West Antarctica. Thus, the assumption that the East Antarctic Ice Sheet was more stable was to some extent, just that, an assumption. Without data, it’s difficult to tell for sure what is happening to the ice sheet or glaciers that drain it.But, if you want to track the ice sheet going back decades, there is one data set that will work; Landsat. Imagery from the spectacular Landsat satellite series goes back decades and cover the outflow glaciers in the east. It isn’t designed to measure the ice sheet’s mass, but Landsat data can at least tell whether the glaciers are as stable as people thought they were.The results, led by researchers from Durham University in the U.K., were published this week in Nature, and they suggest an ice sheet that is much more strongly impacted by the surrounding climate than previously thought.Antarctica on its own is somewhat isolated and so small areas don’t necessarily follow the global temperature trends. Most of the weather stations around East Antarctica show a warming trend from the 1970s to the 1980s, a cooling trend in the 1990s, and a slight warming trend resuming from 2000-2005. As with most weather data, single year measurements are highly variable, so determining trends over short timespans is difficult, but those are the measurements available.The satellite data show a surprisingly good match to these measured temperature trends. Glaciers in East Antarctica were mostly retreating during the 1970s and 1980s, advancing in the 1990s, and then holding steady or starting to retreat again in the 2000s.Overall, about 30% of the glaciers show significant total retreat from the starting point to the present, while the remaining ones are on average pretty close to their starting points.There is good news and bad news here. The good news is that although the world is warming, East Antarctica is still somewhat isolated; the pattern of the warming world hasn’t significantly degraded the East Antarctic Ice Sheet yet.But there is bad news as well; this study shows that the East Antarctic Ice Sheet is in fact significantly influenced by surrounding conditions. The continent of Antarctica is isolated from much of the oceans by particular ocean currents that keep the water and air East Antarctica sees somewhat steady. The key result of this study is that the ice sheet really is only as stable as those currents are.As the world warms over the next century, the hope is that the East Antarctic Ice Sheet remains somewhat stable, because the mass of water is so enormous that slightly destabilizing it would have global impacts. This study doesn’t show that it is in danger today, but it does say that this ice sheet too will be strongly impacted by a warming world, and this ice sheet will need to be monitored in much more detail than is currently the case.-JBBImage credit: USGS, and press report:http://www.bbc.co.uk/news/science-environment-23868841Original paper:www.nature.com/nature/journal/v500/n7464/full/nature12382.htmlSome other details:http://www.antarcticglaciers.org/antarctica/east-antarctic-ice-sheet/ -- source link

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