Arctic Ocean
From dKosopedia
The Arctic Ocean is mostly frozen over with ice caps. Global Warming caused by the Global Warming, a.k.a. the Greenhouse Effect, threatens to melt these ice caps and raise sea level worldwide. Since the majority of people in the world live close to sea level, with many cities going right up to the water front this could have devistating effects. Vienna, Austria already struggles to keep water out with elaborate waterworks. Some Pacific Island nations could simply vanish into the sea.