Saturday, February 21, 2009

Day 30

Today we visited the English antarctic base Halley. Our shuttle consisted of a platform mounted on skis and pulled by a snowcat. The base was only 15 km away, but it took our shuttle about 50 minutes to complete the journey. With -16 degrees Celcius and a bit of wind, I was pretty cold when reaching the base !

The first sight we got of the base was a row of multi-colored containers. As the wind blows around the containers, the snow is removed along their sides, so they must be sufficiently spaced from each other to prevent them from falling in their neighbors holes. The trail we followed was marked with barrels every 50 m or so, reminding us that visibility can get very poor in bad weather conditions.

Finally there ! Paris was not indicated on the sign post. Ah, these British people...

Below is the main building where the living quarters are located. We ate lunch with the base crew there. Not as good as on the ship... But not too bad for such an isolated place !
The buildings are built on stilts to reduce snow accumulation due to wind transport, but the stilts must be extended every year to prevent the buildings from being buried under the falling snow anyway. Earlier versions of the base, the first one of which was built in 1956, were simple buildings built directly on the ice, but had to be abandoned and replaced every decade or so because they were buried and crushed by the snow.
Below is one of the science buildings. It is located about 200 m from the main building, but imagine having to walk there back and forth every day in the dark during winter with temperatures reaching down to -50 degrees ! Brrr...

Inside is the ozone lab, where they measure the ozone content of the air column above the base. It was there in 1985 that scientists first measured the ozone depletion of the Antarctic stratosphere, the famous ozone hole.

The present base, Halley V, is drifting westward with the ice shelf, and has already entered an unstable area which could suddenly detach and drift away as icebergs. Therefore, a new base will be installed further east around 2012. Some building modules (see below) have already been built and await their turn. They are designed with hydraulic stilts, which can be extended much more easily than the present stilts, and the stilts are mounted on skis so that the buildings will be relocatable, to maintain the base location despite the continuous ice flow motion (about 1-2 m per day).

We then returned to our ship, squeezing ourselves inside the snowcat to avoid freezing in the platform behind. We left some of the crew that will spend the whole winter there, isolated from the rest of the world for months... The rest of the crew joined us on the ship, and partied joyfully to celebrate the end of their work in this extreme environment.

Tomorrow the ship will sail away, and we are going to deploy our last SASSI mooring and our PIES.


  1. This place is quite amazing and out of norm. I have a question. The buildings are getting buried by snow accumulation but the whole surface level does not go up every year, is not it? I am guessing the whole snow mass is on the contrary going down, maybe due to its own weight and lateral motions, so that the surface level stays -at first order- stationary with time?

  2. Good question ! I am not the right person to answer, but my guess is that since the ice shelf is floating on water, as snow accumulates on the surface, it sinks deeper, but gets melted by the water below, so probably stays leveled to first order. At the same time, ice from the continent flows outward continuously and pushes/replenishes the ice shelf, which therefore also moves laterally. Then ice calving breaks some parts on its edge to form icebergs.