ABSTRACT
Within our lifetime, the Arctic Ocean will transform from a permanent sea-ice cap to a seasonally ice-free sea. Like a fertile area becoming a desert or a glacier becoming a mountain valley, this is an environmental state-change where the boundary conditions and dynamics of the system are fundamentally replaced. 1 Consider that the boundaries of the Arctic Ocean have been the sea-ice cap, the sea floor and surrounding continents, with inflow-outflow from the North Pacific and North Atlantic, together with solar forcing from the Sun. Removing the sea-ice cap fundamentally alters the dynamics of this Arctic Ocean system. Over timescales that are relevant to humans in the region, even in a historical context over centuries and millennia, the new Arctic Ocean is unprecedented.
