Beneath the ice

Adrian Glover braves the freezing ocean around Antarctica and finds it rich with underwater life

I have recently returned from a two-month trip to Antarctica. I can report that despite our best efforts to warm it up, it is still damn cold. I can report the vast ice-world of our imaginations, but with a thin human presence of Portakabins, scientists and construction workers. I can report a land locked in white, but a freezing ocean still rich with life. And I can report that ice cubes carved from thousand-year-old snow make the best gin and tonics in the world.

I am a research scientist at the Natural History Museum in London. On occasion, they let us out of the basement, sometimes even out of South Kensington, to find and describe new species, discover more about the natural world, and generally try to get into dangerous places. In April last year, I got a call. My colleagues at the British Antarctic Survey, run from an anonymous, shedlike building just off the M11, had a problem: too many worms. This is a problem that afflicts many a marine biologist. These are not worms from lack of personal hygiene, but worms from deep-sea mud. In particular, the segmented, hairy ones called polychaetes, which were too numerous for the BAS team to cope with alone. For some perspective, consider that 60 per cent of the planet is deep ocean, and in most areas, about 60 per cent of the large animals living there are polychaetes. "Mud with worms" could be considered typical for Planet Earth.

The BAS scientists were planning a vast deep-ocean survey in a region of the Antarctic never sampled before. Their target was the huge Pine Island Bay, located in the part of the continent that faces the Pacific Ocean. It is one of the remotest regions of the Antarctic coast, lying more than a thousand miles from the nearest research bases on the Antarctic Peninsula and Ross Sea.

The Antarctic coast dips south here - this was where James Cook, in his second voyage on the Resolution, tried to reach the supposed southern continent, and failed. This southerly dip in latitude creates problems. In most of the Antarctic Ocean, the winter sea-ice that forms around the land mass melts away in the summer, with temperatures reaching a balmy 5°C in the peninsular area. But the more southerly Pine Island Bay has, until recently, been locked in with thick sea-ice that lasts throughout the year, the bane of any Southern Ocean ship's captain. Only huge US and Swedish icebreakers have ever penetrated it, and nobody had taken samples there.

I run a small research team studying deep-sea biodiversity. We specialise in polychaete worms, and the collaboration with BAS seemed ideal. With access to their incredible logistic platform - five research bases, two ships and five aircraft - I would be able to collect data from one of the most remote regions on the planet. They, in return, would have someone to take the worms off their hands. First there was a phone call, then a meeting at an office in Cambridge, followed by a military flight to the Falklands, and suddenly we were steaming south into what could only be described as vaguely charted waters.

It might surprise many that we know neither what lives in most of the ocean, nor even how deep the ocean is. With a few clicks of my mouse, I can launch Google Earth and view almost any point on land with startling clarity. The blue bit remains just that - blue. Vague undersea mountain ranges are visible, but zoom in and all you get is pixellated noise. The opacity of water to almost anything except sound waves is our greatest obstacle to visualising the planet. Because of our water, we have better topographical knowledge of Mars than of Earth.

Sampling the deep-sea bed has been likened to drifting in a hot-air balloon over land shrouded in mist, occasionally lowering a bucket over the side to see what lives there. Armed with advanced bucket technology, our ship, the James Clark Ross, steamed into Pine Island Bay. For two days we pushed through broken floes of multi-year ice, until finally we popped into clear, open ocean at a latitude of 70 degrees south, not far from the point Cook reached in 1774. Cook, his crew no doubt yearning for a return to Tahiti, was forced back. We had open sea all the way to the coast, and a pod of minke whales bow-surfing in the sunshine as we headed south. There is no evidence that global warming opened the channel for us - if anything, the recent trend has been an extension of sea-ice around Antarctica - but we were all thinking it.

Sea-ice has unusual properties: the sorts of properties that give Southern Ocean captains sleepless nights, keep them looking anxiously out to sea and, more recently, darting to the satellite data that streamed daily into our ship's computers. Within days, sea-ice may be blown out to sea and break up, and open water may form around the continent. Just as quickly, winds can push it back together to form impenetrable pack ice, trapping ships for an entire season.

Concerned that the open water would not last, we worked quickly. The geologists used sonar - sound waves sent through the kilometre-deep water - to form images of the seabed, looking for evidence of glacial erosion. Irrespective of human-caused global warming, we already live in a warm age, with sea levels almost as high as they have ever been. Twenty thousand years ago, the giant ice cube that sits on the Antarctic continent - the "ice sheet" - extended far out to sea, perhaps extinguishing much of the rich Southern Ocean marine life. While the geologists looked for evidence of these ice sheets, we used deep-water trawls to collect marine animals from the basins of Pine Island Bay far below.

We worked hard, sampling 24 hours a day, the scientists and crew on rotating shifts, sleeping one minute in snug cabins, then dressing - thermals, fleeces, sea boots and all-in-one orange flotation suits that are supposed to keep you alive if you go over. On the deck, in the early hours, the pack ice looming on the horizon, we hauled in trawl nets, picking, identifying and sorting animals we brought up. Every day, the captain scanned the radar and ice data for evidence that the pack was closing around us.

There is a theory in biology that the higher the latitude you are in, the fewer the species you will find. On land, there is good evidence for this - the ice dome of the Antarctic continent has a species diversity of virtually zero. One of our goals is to test this theory in the marine environment. Our trawls seemed rich in life. For just one family of polychaetes, I found 15 species from the same location, several new to science. It will take time, and painstaking microscope work back at the museum, to analyse our data. Once we have it, we can start to answer one of the great questions in ecology - the reason for biodiversity.

As we steamed back north out of the bay, the sea around us started to freeze. First we saw an oily sheen on the water surface, then crispy pancakes began to form, speckled with icing-sugar snow. Our ship could push through it easily, but, with winter setting in, it was time to get out. After three weeks on a glittering, icy ocean, we popped back into the grey Southern Ocean rollers, and headed for home.