A radar survey conducted between 2004 and 2008 by Japanese, Chinese, and British scientists reveals how the ice on Antarctica grew, and what the land looks like beneath the ice. At the center of the continent, a nearly two-mile-thick slab of ice has clung to Antarctica’s rocky surface for 14 million years; this is the first time scientists have gotten a virtual glimpse beneath the sheet’s surface.
The topography beneath the ice is mountainous, with peaks and valleys like the European Alps, according the study published Nature. Scientists say that 34 million years ago, small glaciers expanded from the mountaintops and shifted to carve out the terrain. To collect the data, scientists drove huge trains of caterpillar tractors in tight lines over Dome A, a plateau of ice at the heart of Antarctica. The tractors carried radars that pinged down through the ice and sent back profiles of the frozen rock landscape below [New Scientist]. Scientists knew the velocity of the radar’s radio waves, so they calculated the depth of the ice by timing how long it took the waves to hit the rock and come back to the surface.
For the glaciers at the tops of the so-called Gamburtsev mountains to begin flowing and carving the terrain about 34 million years ago, when Antarctica first began to cool, the study determined that average summer temperatures at those altitudes must have been at least 3° Celsius…. As Antarctica cooled even further, mountain glaciers grew, swept downslope and coalesced in valleys already previously carved by major rivers and their tributaries [Science News]. The original glaciers in the region became thicker, expanding into the ice sheet that for about 14 million years has blanketed the Antarctic continent.
This new information is important because it adds to our understanding of what keeps ice sheets stable. If the globe continues to warm, being able to predict how ice sheets like the Antarctic one will react could be crucial. “This puts the ice sheet into the context of global climate and what conditions are needed to grow an ice sheet,” explained [geoscientist Martin] Siegert. “The worrying thing is that we seem to be going back to carbon dioxide concentrations consistent with there being a lot less ice around” [BBC].
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Image: flickr / es0teric