Antarctic ice sheet built “bottom-up”

BBC : Survey data collected from the Gamburtsev mountain range shows liquid water is being frozen to the bottom of the Antarctic ice sheet. In some places, it makes up about half of the entire ice column, writes Jonathan Amos for the BBC. The Gamburtsevs are similar to the European Alps in scale, but they lie hidden beneath kilometers of ice. It’s well known that ice sheets grow from the top down as snow settles and compacts over thousands of years; the new data illustrate how they also can grow from the bottom up by accumulating layers of liquid water. If subglacial water is forced up valley sides to locations of lower pressure or away from heat retained in rocks, it will turn to ice and stick to the bottom of the sheet above. Aircraft used radar to detect ice thickness and layering and mapped the shape of the underlying bedrock. They also conducted gravity and magnetic surveys and listened to seismic waves passing through the mountain range.