Rocky Halley Picture Show

2007-08-26

The sun is back at Halley. A couple of week's ago, and right on schedule, a small burning bar of gold spread slowly out of the pale yellow distance and melted into view on the horizon. The unfamiliar sun slowly edged its way upwards and finally displayed a bite of a disc as Jim raised a fresh flag over the Brunt Ice Shelf. Since then the days have quickly gained more and more light, and we're now walking to work with a dark orange fire to the East, heading back for lunch with a blazing light hanging low in the South over the Laws, and ending our day with the sun setting in a dirty sea of mist to the West.

Deep blue dawn

Sunrise at Halley

Jim raises the Union flag at sun up

Having the light back makes an enormous difference to how much we can get done and triggers a massive amount of work outside. The masts need to be slackened off after the build up of snow over their stays, blimp hangers get constructed, cabooses are prepared for towing out to science sites and snow must be thrown off the platforms. It's still fairly cold and won't really warm up until we've had the sun for a couple of months. We have to be careful not to get frostnip and not to get sunburnt -- especially as the ozone hole is about to form high above us.

Tamsin gets a frosty face

I get a frosty face

Purple sunrise

Burning orange in the sky

Although ozone gas is concentrated in the stratosphere (which is to say, very high up), there is a small amount of the gas in the air nearer the surface. Usually this runs at a constant 30 or so parts per billion, but during the spring at Halley we sometimes see this concentration fall to a tenth of its normal levels before rising back after a few hours. We think these depletion events are caused as the sun hits freshly forming sea ice. Although the ocean around us is covered with ice, this shifts about and forms open patches now and then. As these cracks open up new ice forms rapidly on the sea surface and grows into frost flowers. Sharp spiky growths that look a bit like tiny thistle plants. The freezing process that forms them also concentrates halides on their surface, turning them into ideal sites for the sun-powered reaction that eats up ozone.

To test various ideas about exactly how and where this happens we fly a helium blimp into the first two hundred meters of the atmosphere with an ozone sonde dangling underneath it. This, in combination with an acoustic radar that lets us see how the air is split into layers, allows us to make good guesses at the cause for the depletion event.

Flying the boundary layer ozone probe

Elsewhere on base we've had a tiny bit of medical excitement as Julius has injured his leg. Like me back in my first summer he's now hobbling about on crutches with a plastercast, and we're getting plenty of exercise pulling him around the base sat in a sledge, bringing a whole new edge to the idea of man-hauling. He was even able to join in with the pub crawl we held to celebrate Ant's birthday. Having learnt a lesson last year I constructed an insulated holder for my wine so did not have to try drinking frozen slush.

Pulling a broken Julius back from work

Finally, yesterday, we celebrated my birthday a bit early. Perhaps a little bravely I went for a Rocky Halley Picture Show theme which produced a number of moderately disturbing fancy dress costumes and some dancing which, it must be said, should probably not be repeated. All in all we had a good time, danced the Time Warp, and tried to play pool in corsets constructed from cardboard and duct tape. I did, of course, look quite the part as Frank Furter...

The cast of the Rocky Halley Picture Show

Frank Furter (me) and Riff Raff (Mark)

Halley remembers that moment when..