A large pressure ridge


8 February 2007

As we drift through the Arctic Ocean Tara is like a small piece in a massive 13 million square kilometer jigsaw puzzle, a puzzle of ice floes jostling in constant motion, pushed by the invisible ocean currents below the ice, the wind above the ice and the distant force of the moon.

We have experienced significant ice movement on average every 6 weeks throughout the winter, this week being the most recent period of activity. While we have learned to live with this constant threat, I don’t think we will ever become completely accustomed to the distant growl of breaking ice, the screeching sound inside Tara, the vibrations reverberating throughout the boat and the unstoppable indiscriminate force of bus sized blocks of ice coming our way. Each event has been very different in nature, sometimes sudden fracturing and areas of open water, other times compression with ice floes sliding beneath the hull. Last night and today a large pressure ridge 5m high formed beside Tara. Several decades ago, in the era of Nansen on the Fram, it was common to encounter ridges up to 10m high. The reduction in height is though to be mainly due to the reduction in the thickness of the sea ice across the Arctic. Forming during the night by two colliding ice floes, what appeared to be a living breathing ice mountain advanced at a maximum speed of about one meter per minute in our direction. As this ridge slowly but surely crept towards the boat and meteorological mast there was not a lot we could do except observe. The biggest risk for Tara is the possibility of a pressure ridge pushing onto the side of the boat tumbling onto the deck, pushing us onto our side or compromising the structure of the hull. Thankfully stopping short of our scientific installations, a chaotic scrum of ice blocks did however compress onto the port bow with extreme pressure, providing a few tense hours on board as we stood by with chainsaws at the ready to attack.

This latest storm period and resulting ice activity has lasted for the past week, giving us a few sleepless nights and reminding us once again that we will only be able to fully relax again when back on terra firma.