Katabatic Winds of Antarctica

John Goodge, left, a professor of geological sciences at the University of Minnesota-Duluth, and Jeff Vervoort, an isotope geochemist from Washington State University, will be writing occasional posts from their research expedition in Antarctica.

Thursday, Dec. 9

Katabatic winds are an Antarctic specialty. They are a phenomenon of nature, but they are no friend to those of us who are mere summertime outsiders. Katabatics form by cold air masses descending onto the ice cap and spreading along the ground. There is nothing to stop them, so they form sheet-like rivers of air and blowing snow. It seems like you are in a relentless storm, but it’s odd because when you look up, the sky is most often sunny and blue, seemingly benign. The katabatics will keep up until the cold air mass dissipates, or until there is a countervailing push from the ice shelf side of the mountains. The hardest part about dealing with katabatics is that they can last for days on end, unlike most storms we are familiar with at home that come with short-lived frontal systems.

Late Wednesday afternoon we had a sudden — literally within minutes — turn around in the weather, when the winds reversed direction, a white wall of blowing snow descended on camp and the wind speed jumped high enough to make you lean into it. That lasted most of the night without letup, yet I had a fairly good sleep in my tent despite the incessant flapping of the tent fly. By morning some calm returned, so we waited to see if the weather would stabilize for a few hours. I didn’t want to push out at the first sign of calm because the winds can come back at any point. We were taking down our tents — the very last thing to do when moving a camp on the ice — when the wind started picking up again. By the time we had loaded the Twin Otter and taken off, the blowing snow was almost up to the wing. But we were committed to at least go have a look.

I don’t think anyone in our group was particularly anxious to be headed over to our first site in a small mountain range at the edge of the polar plateau. This area, with nothing between it and the expansive Antarctic ice cap, is notorious for wind. I was apprehensive about what we would find. By the time we got over the Miller Range, I could see plumes of snow blowing off ridges and looping out of “blowouts” where vortexes of wind hollow out scoop-shaped cavities in the snow and ice. Not a good sign. As the plane descended for an approach, I saw streamers of snow scooting across the surface. In katabatic conditions, the whole surface is active.

Our pilot measured the wind speed on the ground at about 35 knots and pulled up from his final approach to head back to camp. As we flew over our site we could see our previously staged cargo drifted in, half buried by snow blown in over the last 12 hours. When we return, our first job will be to dig out the tent, stoves and radio we will need to establish a camp before the plane is permitted to leave us. The large drift around our cargo cache is not going to make that any easier.

This is the reality of getting to places in Antarctica. Weather delays are a staple, whether you are traveling by air or on the ground. There are just some conditions that are not worth struggling against and risking anyone’s safety. Today’s were not as cold as many places in winter, but not the best conditions for setting up a new tent camp. Maybe this is where the expression “hurry up and wait” was coined. I know that it will subside, and I have had many fine days when it is possible to work in relative comfort, but it will take another day, or maybe more, until we get to that point. In meantime, the CTAM camp is burgeoning with staff and science groups, and more are scheduled to arrive, so the camp staff members, like ourselves, are hoping for better weather so we can get out.