From: Ricardo Roura - Greenpeace scientist
10th February 1997
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10 February 1997
The MV Arctic Sunrise is heading south again, rolling on the Southern Ocean swells that crash against the western side of the Antarctic Peninsula. Last night we crossed the Antarctic Circle and that refreshes our excitement after a few busy weeks on a crowded ship. Further south, new icescapes, new horizons, more discoveries.
Over the past few weeks our ship was able to sail through the uncharted waters that were once covered by the 200m thick layer of ice that was once the northern part of the Larsen Ice Shelf. An area 25 nautical miles square, now open waters. Every mile ahead was a mile nobody had sailed before. The unknown becoming known progressively, at the speed in which the ship could sail through close pack ice.
For two decades or more scientists have been working in the Larsen Ice Shelf; they travelled over its icy surface, described its shape and movement and tried to read through into the mass of ice and beyond, trying to visualise what was under the ice. Theories appeared to describe what was unknown on the bases of what was known, and while some of these were plausible, the truth was that nobody knew what was under the ice. How deep it was? How was the under-ice landscape? Why? It was our fate to find the answers for some of these questions.
As we sounded the depths our working hypothesis was that we should come across channels in the shallow waters that once were under the ice. Then we would stop the ship and take core samples of the sediments lying on the seabed. The sediments would provide a record of the recent depositional history under the ice, marked by the recent collapse of the ice shelf.
Our hypothesis vanished as our echo sounder signals took longer and longer to return to the ship. The depths increased by the minute. We could see before our eyes how the underwater landscape was drawn in the echo sounder's graph. There were no multiple channels, no shallow waters; there would be no sediment sampling -- depths were just too great.
What we saw was a very deep channel, up to one thousand meters deep, several miles wide, stretching for over fifteen miles, nearly reaching what was once the ice shelf front.
In a glacial period back in time, glaciers had carved the channel when the sea level was lower because all the water was on land as ice. Later, in an ensuing interglacial period, the sea level had risen as the glaciers disintegrated. The channel was covered by the sea and, later on, by a floating mass of ice (the Larsen Ice Shell). As that part of the ice shelf collapsed, possibly caused by climatic change, the channel was once again under open waters. On the water surface minke whales swim amongst the pack ice.
Finding a deep underwater channel instead of shallow waters gave place to more questions than those that were answered. Had the channel developed over older structures, or had it been solely the making of a glacier? What was its role in the collapse of the ice shelf? And so on. (There are already new theories awaiting to be tested).
The excitement of this finding left us scientists on board floating in a cloud, as when you meet someone and fall in love. In true Antarctic tradition, the experience set us back to a time when geographical discovery was still possible. Not that everybody shared our excitement, but for us it was special. It is comforting to think that while the world is changing rapidly, Antarctica remains a source of wonders, even though globalization and climate change seem to have caught up with it.