We have started drilling ice cores here at Allan Hills! Ice drilling takes place at many places in Antarctica and Greenland (as well as at high altitude glaciers around the world), but we are here for some very specific ice.
Allan Hills is a blue ice area. Blue ice areas only cover about 1% of surface of Antarctica. It’s called blue ice because, well, it is blue. If you’ve ever seen glaciers or icebergs that look blue on the underside, they look that way because that older ice underneath has been compressed by the weight of the ice on top of it, squeezing out air and making it look blue for the same reason that liquid water in the ocean looks blue.
Blue ice at Allan Hills, with a little bit of white snow on top
In blue ice areas, the natural movement of the ice sheet is stopped by mountains, trapping the ice and preventing it from flowing out to the ocean. But the ice behind it keeps flowing, and as a result the trapped ice gets folded and pushed up, so that the old ice at the bottom of the ice sheet glides up the incline toward the surface. In addition, the winds off of the nearby mountains - known as katabatic winds - are fierce and nearly constant, scouring away snow and the topmost layers of ice over time.
A view of our camp with the Allan Hills in the background. Much of the mass of these mountains is under the ice sheet, and they are helping to trap the blue ice here.
For most ice core projects, scientists have to drill down very far into the ice sheet to find ice that is more than a couple hundred thousand years old. But here at Allan Hills, the surface ice is that old. And when we drill down just a couple hundred meters, we can find ice that is millions of years old. In fact, in a previous field season, our team found 6 million year old ice - the oldest ice ever found on the planet!
And that is why we are here in this part of Antarctica, to find more ancient ice. The ice has trapped air bubbles, containing air that is millions of years old. Our team analyzes the chemical content of these air bubbles, to help us better understand the climate from that time period. More ancient ice means more bubbles and more data!
Air bubbles in a piece of ice core we drilled earlier this week. The air trapped in these bubbles is probably at least 200,000 years old.
The blue ice is beautiful. Riding a snowmobile from our camp out to the ice core drill across the blue ice looks like you are driving on the surface of the ocean - it is all blue and ripply. Any holes we drill into the ice - not just ice cores, but holes for staking our tents in the ice, for example - glow a deep blue as the sunlight passes through the blue ice. We have a storage trench dug into the ice, where we store the cores as they await transport, and sitting in there with the doors closed is ethereal.
A view inside our ice storage trench. The blue color is the result of the sunlight shining through the blue ice.
Stay tuned for more ice core science and Antarctic adventures!