Drake Passage
[[File:Conveyor belt.svg|thumb|195x195px|Water circulates around the globe as if it was on a conveyor belt. The Drake Passage is the narrowest channel, and its shape (width, depth and bottom roughness) strongly affects the global circulation.]][[File:Experiments opening drake passage.jpg|left|thumb|427x427px|The Drake Passage influences the global surface temperature and Atlantic circulation. With a closed Drake Passage, there is no [[Antarctic Circumpolar Current]] (as the [[Pacific Ocean|Pacific]] and [[Atlantic Ocean|Atlantic]] are not connected), no [[North Atlantic Deep Water]] cell, the Southern Hemisphere is warmer and the Northern Hemisphere is colder. Gradually deepening the Drake Passage, a lighter [[Antarctic Circumpolar Current|ACC]] appears, but with a DP of 690m depth there is still no [[North Atlantic Deep Water|NADW]], and the Northern Hemisphere is still colder. Only with the current shape (width and depth) of the Drake Passage the Southern Hemisphere is cold enough for the Antarctic Ice Sheet to appear, and the Atlantic Circulation is strong enough for the Northern Hemisphere to warm. (adapted from [Sijp and England, 2003])]]