WAIS Divide: Ice and Ash
Deep in the ice sheet, the ice is very clear – there are almost no bubbles in it. By about 1500 meters, the pressure in the ice is so great that air in the bubbles gets forced into the ice matrix into something called clathrates. It’s really fun to look at such a pure substance. It’s hard (for me at least) to capture it with a camera.
There’s only a limited window to see the ice this clear because once the ice is at the surface, the pressure has been relieved, and the bubbles start to reappear. When I see this ice again in Denver this summer, it will not be nearly as clear.
Most of the ice cores are perfectly clear except for the breaks that occur every three meters. However, we have gotten to see a lot of ash layers. West Antarctica is volcanically active – Ross Island, where McMurdo is, is a volcanic island with the very active Mt. Erebus just a few miles away. That volcanism leaves beautiful layers in the ice.
This layer is from a little over 3000 meters deep. The ash is about ~45,000 years old and is still amazingly preserved. We jokingly call it “skua poop.” It was probably a very thick ash layer at one point because the ice has thinned ~20x (that is, a layer that started 20 cm thick is now 1 cm thick).
We just got a new ash layer, so I’m adding photos of it too! It’s probably around 60,000 years old.