But regardless how safe we make offshore drilling in the Arctic, there will still be a significant risk of a major oil spill, and policy makers and industry need to be honest about this. People will make mistakes, and equipment will fail. It's not a question of 'if' a major spill will occur, but 'when and where.'

A major spill will travel with currents, in and under sea ice during ice season, and it would be virtually impossible to contain or recover. Even with robust oil spill response capability, in most scenarios far less than 10 per cent will be recovered, and a major spill could easily become a transnational event.

A large spill would undoubtedly cause extensive acute mortality in plankton, fish, birds, and marine mammals. As well, there would be significant chronic, sub-lethal injury to organisms - physiological damage, altered feeding behavior and reproduction, genetic injury, etc. - that would reduce the overall viability of populations.

There could be a permanent reduction in certain populations, and for threatened or endangered species, a major spill could tip them into extinction. With low temperatures and slow degradation rates, oil spilled in the Arctic would persist for decades. And a major oil spill in the Arctic Ocean could severely damage subsistence harvest opportunities, and forever change the lives of coastal peoples.

Put simply, oil drilling in the Arctic Ocean cannot be done without risk and serious impact. There will be chronic degradation, and there will be spills. So the policy question is whether we wish to expose the Arctic Ocean and its people to such risk.

http://www.theecologist.org/blogs_and_comments/commentators/other_comments/1096998/why_arctic_ocean_oil_drilling_is_a_risky_choi