29 September 2013
Jean-Claude Gascard, physicist/oceanographer and emeritus research director of the CNRS laboratory LOCEAN at the University Pierre et Marie Curie in Paris, joined us aboard Tara in Tuktoyaktuk (Canada). He is one of the designers of the Tara Oceans Polar Circle Expedition, which just succeeded in traversing the Northeast and Northwest Passages in 7 months. He explains scientifically how this type of expedition is now possible in such a short time. A tour of the Arctic during the summer was still exceptional only 20 years ago.
- Vincent Hilaire: Why is circumnavigation of the Arctic Ocean now possible during the summer season, crossing first the Northeast and then the Northwest Passage?
- Jean-Claude Gascard : During the summer ice melt, the Northeast Passage opens up before the Northwest Passage. The reason is that geographically the Northwest Passage is closer to the “pole of cold” than is the Northeast Passage. On average, the Northwest region of the Arctic is colder at comparable latitudes and seasons during the period of freeze – from September to May. Which is why we chose to sail from east to west for the Tara Oceans Polar Circle Expedition. ”
- Vincent Hilaire: What is the “pole of cold” in relation to the geographic North Pole?
- Jean-Claude Gascard : The pole of cold is centered in northern Canada and Greenland, and includes almost all the Canadian Northwest Territories, including the research base Eureka, Resolute Bay, and the military base Alert on Ellesmere Island, among others. It’s the reason why there are so few Inuit villages in these latitudes and in this region of the Arctic in general. It’s too cold. Resolute and Grise Fjord are villages, Eureka and Alert are research bases further north.
- Vincent Hilaire: How has the pole of cold evolved since the early 80s?
- Jean-Claude Gascard : It is still located north of Ellesmere Island and Canada. It includes the Northwest Passage, either on its way north or south. It actually moves very little, and remains localized in this geographic zone. But the intensity of the cold, though still extreme, has been decreasing considerably over the last 30 years. For reference, instead of blizzard at -30° C, we have blizzards at -20° C. We measure this in periods of freezing degree-days (FDD) accumulated during the cold period. Since the 80s, we have gone from 6 000 FDD to 4 000 FDD. This is equivalent to a one-meter decrease in thickness of the ice. The ice is definitely thinner than before, even within this pole of cold.
- Vincent Hilaire: If the pole of cold remains in the Canadian North, therefore in the Northwest region, does this logically mean the Northeast Passage will open up increasingly earlier in summer?
- Jean-Claude Gascard : Yes, because it’s far away from the pole of cold. But in general, both the Northeast and Northwest Passages will tend to open up earlier and close in later, except for a seasonal anomaly related to natural variability, as we experienced this year. But that didn’t prevent Tara, though she’s not an icebreaker, from going through.