Medieval geographers referred to very distant places as Ultima Thule, beyond the "borders of the known world", but even before that, as far back the classical period, authors like Strabo and Pliny talked of a mysterious, semi-legendary place, found at the end of the world, called Thule.
By the Renaissance, Thule came to be identified with Iceland and Greenland. Sitting here on board the Esperanza as I look through my cabin's porthole over the ice-choked waters of Baffin Bay, with storm-flecked waves, roiling seas and towering icebergs slipping silently through the banks of mist that surround our ship, it's not hard to see why this spectacular region inspired mariners to talk of it as being the very edge of the world.
I'm the campaigner here on the Esperanza as we, together with our fellow Greenpeace ship the Arctic Sunrise, travel north through the ice floes towards the Arctic Circle on our journey to expose and confront a British company, Cairn Energy, that plans to kick-start a dangerous new oil rush here in the High North.
This is the first time I've sailed on a Greenpeace ship, which is an enormous privilege in itself, but it's also the first time I've ever been this far north.
As a child I grew up reading about the Norse myths, tales of Thor, Heimdall, Loki and, above all, the sinister Frost Giants who lived in the frozen lands of Jotunheim. I remember daydreaming about watching the aurora dancing and flickering high above the ice fields. Ever since then, I've been captivated by the Arctic.
While being here now has fulfilled a lifetime ambition, actually seeing, hearing and feeling first-hand this unique, vulnerable and pristine region - the absolute silence, the remoteness - makes me realise more than ever just how crucial it is that we succeed in our campaign to stop Arctic oil drilling.
I've worked on the campaign for a year and over the last few months have read with increasing alarm the reports of scientists telling us how the northern polar areas are warming faster than anywhere else on Earth. In a few short years, the north pole may even be ice-free during the summer.
This means the Arctic is becoming less remote. Global warming is melting this once impenetrable frontier as governments and corporations begin to carve up the resources they suspect lie beneath the ice. Companies like Cairn Energy, which this year plans to drill four exploratory oil wells in the deep waters of Baffin Bay, are now rushing in to exploit the very fossil fuels that are causing the melting in the first place.
At the very same time, Cairn refuses to publish a plan to explain how it will try to deal with an Arctic oil spill. When you see for yourself the volume of ice out here, this seems incredible. How can any company be allowed to operate so recklessly, especially when experts are telling us that cleaning up an Arctic oil spill would be nigh-on impossible?
The international team of Greenpeace volunteers on board the Esperanza and Arctic Sunrise are here to show the world just what Cairn Energy is gambling with. Though we have now been joined by a Danish Navy warship, we will confront and expose the incredible risks this little-known company is taking here in the near-frozen waters off Greenland. We're doing this because it's time to go beyond oil and protect the Arctic.
Photo (C) Will Rose / Greenpeace