2005-12-19

Since Bird Island, about a week ago, we've headed along the length of South Georgia, then ESE until hitting a spot around 60°S 05°W, where we turned right and made due south towards the coast of the continent. The ice has been thin, then not there, and now there again and much thicker. We expect to arrive at Halley in a couple of days, so evenings have becomed more subdued, with less drinking (with some exceptions), and fewer people standing sentry on deck for whales and other wildlife. Mostly we're quietly waiting to get there, with the silence pierced from time to time by the mighty roar of the ice ripping apart under our prow, then banging and scraping along the hull. The ice serves one wholesome purpose: it kills any swell, leaving the sea wearing only the smallest of ripples. The ship now jerks and jumps on impacts but the constant lurching is banished to another ocean.

We passed the Antarctic Circle at around 1925 (2225 GMT) on the 18th. To celebrate a few of the Halley winterers "camped" out on the monkey island (the roof of the bridge), with only our full-on expedition sleeping bags between us and the softly falling snow. The temperature was a balmy two degrees below zero so we were all fairly hot. Sleep was made even less likely by the constant daylight but it was nice for once to be able to sit up in bed without hitting my head on the roof of a cabin.

This morning, while decamping, we saw an Emperor penguin sat on a little bit of broken off pack ice. Head held aloof he watched our passing as if it happened every day. He was the first we've seen since South Georgia, but then we are now only a hundred miles or so off the coast of the continent we've been getting to for the last month.

In a musical interlude we've had the first session of the forthcoming Halley samba spectacular. Under the vigourous leadership of Comms-guy Dave, a bunch of total beginners managed to knock out a passable sort of noise after a couple of hours. It was certainly a fairly special moment as we grooved out on the after deck while icebergs drifted slowly by.

I've even managed to fit in something scientific. Back in the Seventies a large area of warm water occupied the Weddell sea for a few years running, preventing the formation of winter sea ice and generally confusing oceanographers. This polynya has not recurred since but it is expected that one will happen again, although no one knows when. If one does happen, it will be very useful to have data on the ocean state before it appears, and especially as it forms. Seeing as the Shackleton lurks around anyway we take measurements of the sea's temperature profile every three hours.

We do this by dropping an expendable bathymetric thermograph (XBT) off the end of the boat. This is a weight, a thermocouple junction and a long thin wire. Using the known rate of falling, and the output of the thermocouple, we can obtain the temperature-depth profile. From the couple of runs I've helped with, we've seen the cold upper layer of the sea increase in depth, and the transition between layers takes longer, as we've headed further south, which is roughly what you'd expect.

Launching an XBT

We're now following the coast southwards towards Halley, and expect to arrive sometime on the 21st. As all of the sea ice around the coast near Halley has already disconnected and disappeared it looks that this year the relief operation will have to take place from a location about 65km away from the base. This will take longer than usual. Although we're arriving early we'll still be cancelling Christmas, and possibly New Year, as all hands will work all hours until we've moved everthing from the ship to the station.

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