Agence France-Presse: Oceanographers said on Sunday they had measured a system of mighty currents off Antarctica that are a newly-discovered factor in the equation of climate change. The system, known as Antarctic Bottom Water (AABW), is generated in clockwise movement in four big sea shelves that abut Antarctica – the Weddell Sea, Prydz Bay, Adelie Land and Ross Sea. Extremely cold water sinks to the bottom of these shelves and slides out northwards along the continental shelf. At the edge …