Wednesday 14 September 2005
Snow rolls - the answer
In my last post I asked what caused strange rolls of snow to form at Halley. Thanks for all the great answers, but no-one got it quite right (don't worry I didn't expect you to!). I think Sue was probably the closest with her suggestion of snow curling off the roof of buildings - good effort! Ken, I'm afraid you were disqualified for having a daughter at Halley and getting inside information ;-)
It all starts with the line of shipping containers which run to the north of the main base. Because we have such a limited amount of space on the base we use containers mounted on skis to store additional equipment (stuff that isn't used very often and can survive in the cold). There is a line of about 20 of them containing everything from field equipment, reels of cables, electrical and plumbing spares to emergency food and clothing.
The container line with Drewery building and Garage in the distance.
Because the prevailing wind here is most commonly from the east, snow tends to stick to the west side of the containers where it is sheltered from the wind. The snow gets packed quite tightly then freezes in place which makes these walls of snow pretty strong.
Walls of snow forming on the containers.
Like everything else at Halley the containers get buried by drifting snow and after a while they have to be pulled out of their windscoop by a bulldozer and dragged to a new location. When they are moved these walls of snow stay put, creating a perfect imprint right down to the corrugated side of the container wall:
Vanessa standing next to a newly formed snow wall right after the containers have been moved. Pictures by Frank Swinton.
Now that the sunlight has started to return the walls have begun to collapse and sag, and any further easterly winds that come along seem to push them from the top and roll them back on themselves.
The walls collapse to form rolls of snow.
They shadows, by the way, are caused by wind tails from the containers in their new positions, which is around 10 metres to the east of where they were.
Posted by simon at 12:07 PM | Feedback (4)