Pack ice

Pancake ice
Pancake ice (Photo: J Smith)
Closed pack iceExpeditioners conduct research on the sea ice alongside the ship.

21st October 2004

Jeremy Smith, Station Leader (on board the Aurora Australis)

The transition when it finally came was startlingly abrupt. Appropriately enough it happened during a one hour afternoon talk on sea ice – the different forms it takes, its environmental significance, and the safety aspects of travelling on it. When the talk was ended the blinds on the window of the recreation room were opened, and there beyond the trawl deck, instead of the heaving steely ocean we knew so well, was ice!

Initially, and for the next 24 hours or so, it was very loose, light ice through which the ship moved without the least difficulty. It was mostly pancake and brash, that is to say discs of mushy, re-forming ice mixed with boulders of broken old ice. Grease ice (loose crystals) streaked the surface between the solid pieces, and a few floes (larger, intact, flat slabs of sea ice) drifted with it. Icebergs (not sea ice at all, but freshwater ice derived form the accumulated snow of the continent) dotted the horizon. Newcomers were entranced, and we all felt a surge of interest and enthusiasm at this concrete evidence of our progress south.

Other evidence came in the form of a visit by King Neptune, to welcome and initiate to his icy oceanic realm all newcomers from the north. We had all been summoned to a compulsory meeting in the mess, billed as a fly-off preparation meeting, but it turned out to be no more than a few words of thanks to the crew and voyage management for a quick, happy and uneventful voyage (so far). At a cue from the speaker, Voyage Leader Vicky, the meeting was then transformed by an invasion of oddly attired, loud creatures who introduced themselves as the King and his consort with several assistants, who, beneath their fishnets, masks, paint and other adornments, could be recognised as various crew and expeditioners recruited for the occasion.

All this hilarity and frivolity was followed by a barbecue on the trawl deck. As one person remarked, he'd been to some great barbecues in his time but this was one of the very best. It wasn't the food that was unusual (regular barbecue fare) nor the drinks (light beer and cask wine is all we are permitted on this ship) but the background scenery. The ship was heading into the light wind so at the stern were sheltered from its chill. Beyond the deck, as snowflakes drifted down, the white scenery was dappled by patchy, passing sunshine. Sea ice passed us in a constant parade of jostling white shapes, with Antarctic petrels wheeling above. The wake foamed and tossed, and as it receded behind us it was progressively concealed by a spreading carpet of ice fragments as they resumed their nearly continuous cover. The ship was steered to pass close to a couple of icebergs which drifted past in majestic glory a few hundred metres away.

A day later the ice had changed, and we began to press through more resistant, continuous pack ice. At first it was mostly thin, first-year ice, less than a metre thick, slowing but not preventing our progress. But hopes that we would break through it into clear water beyond were eventually dashed as the leads of thinner ice or open water gave out and we were faced with an almost unbroken lumpy white surface of rafted ice, with even thicker pressure ridges, all mantled in nearly a metre of snow. To break through, while not impossible, would be slow and very expensive in fuel. The snow made matters worse, cushioning the impact of the ship and making the underlying ice more difficult to break and shoulder aside. We stopped.

Fortunately by now we were within helicopter fly-off range of our destination; Casey was some 80 sea miles to our south-south-east. Unfortunately the weather was not suitable for flying, with a poor horizon, poor visibility, and a forecast of bad weather for the next three days. So for three days we have been, if not quite stationary, then not moving much: ten miles west each day with the drifting pack, and yesterday a few miles back to the northeast to find some flat floes for the sea ice scientists to work on, drilling and taking water samples (they are particularly interested in algae and plankton, the basis for the Antarctic ocean food chain, and source of climatically significant atmospheric sulphur chemicals involved in cloud formation).

Today is our third day stuck in the pack. We are not beset – immovably stuck – but are we unable to get closer to our destination; in fact we are drifting away. Nor, so far, have we been able to fly the helicopters. That should change tomorrow, according to our forecasters, when with luck we will get at least the glaciologists to Casey. They need to get there in a hurry as they intend to return to Australia, with ice cores, on this voyage, giving them only a few days to drive up to Law Dome inland of Casey, set up a drill tent, take their cores down to 150 metres, and return. It will probably take all day to get them to Casey, even with three helicopters. Each machine will need to make three flights, and we are an hour's flying (presently 102 nautical miles to be precise) from Casey.

So it will be Saturday before I myself might fly across to my new home, even if the weather becomes and remains suitable. Still, the end of the voyage is finally in sight, after two and a half weeks. Another Antarctic year is about to begin.