The Arctic Sunrise has left Greenland behind, and is now negotiating the sea ice that lies before our next port of call, the settlement of Longyearbyen, on the island of Spitsbergen, in the Svalbard archipelago, a place where the polar bears outnumber humans.

Our last few days in a very remote part of Greenland's northeast were the coldest of the trip so far. Gone is the light clothing of Petermann and Humboldt in July and August - a similar latitude, now its been thermals, gloves and hats.
© Greenpeace/Nick Cobbing

The actual temperature out on deck the last few days was about -10 Celcius, not low for anyone who lives through cold winters with lower temperatures in Canada or parts of the United States. But remember, it's only September, and the Arctic winter is already kicking in here at the top of the world. And the wind whipping off the ice sheet at "79 Glacier" (Nioghalvfjerdsfjorden) makes it feel a hell of a lot colder than -10.

Because of the bad weather and tough sea ice, we didn't have as much time as we would have liked, but glaciologists Gordon and Leigh managed to get their GPS equipment onto the glacier for more than two days – enough to gauge its reaction to two tide cycles. Fiamma and the Woods Hole team carried out temperature and depth surveys along the floating ice tongue – and one day, even drilled down through the sea ice to find out what was going on. The front of 79 Glacier is a flat, floating ice tongue, like Petermann Glacier, where we spent most of July. However, unlike the rapidly moving Helheim or Kangergluqussuaq glaciers that we visited in the last couple of weeks, 79 has not yet been activated by climate change and only moves a few hundred metres per year, yet still drains 10% of Greenland's ice; Kangergluqussuaq glacier, in comparison moves 14 kilometres a year!

79 Glacier sits in a deep fjord, or trough, which continues 700-800km into the heart of Greenland's Ice Sheet, well below sea level. The front of the glacier is pinned in front on a shoal or ridge in only 100m of water, which keeps the glacier in place. Behind that ridge, the 80 km-long tongue floats above water that is 800 to 1000 m deep. If any major changes take place at the front of the glacier, such as it losing touch with the ridge, this weakness will propagate inland, causing large amounts of ice to be dumped from the heart of Greenland's Ice Sheet, into the ocean, contributing to global sea level rise.

Because it hasn't speeded up (yet), 79 can be studied in a more 'natural' state, so scientists can understand how the faster glaciers used to be. The problem with 79 Glacier is that it's so hard to reach; the last team of scientists that worked on the glacier itself arrived 14 years ago!

Everywhere we're gone in Greenland has a distinctly different landscape, with the land in the north, around Humboldt, Petermann and 79 glaciers appearing more barren and dry than the tundra around Kangergluqussuaq or Helheim. At 79, great steep cliffs with silver rivers of shale sweep down to the frozen fjords and sounds, and the ice sheet dips its feet in the sea. Despite the gigatonnes of ice here, this part of Greenland is functionally a desert, and there's not much sign of life; the sea, however, harbours plenty; in the last few days, we've had whale sightings (humpback and possibly bowhead), seals and some polar bears – last night a mother and cub, and this morning a lone adult. That brings to ten the number of polar bears we've seen on our odyssey around Greenland so far. When I say ‘around Greenland', I'm being literal; given the fact that the extreme north coast and north east coasts of Greenland are hemmed in by sea ice year round, it's impossible to actually circumnavigate the island. However, since June 29th, when we reached the Arctic sea ice in the Lincoln Sea at 82.5 north, until last night, we've been pretty close to circumnavigating; to go further would need sleds and dogs.

So it's goodbye to glaciers, and hello to sea ice; in Longyearbyen we'll be picking up a new team of scientists, lead by Peter Wadhams from the University of Cambridge in the UK. We'll be spending until the end of September exploring the effects of climate change on the Arctic sea ice as it reaches its annual minimum extent.

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