In the 2004 disaster movie “The Day After Tomorrow” New York City suddenly finds itself engulfed in thick ice within the matter of days after a series of superstorms hit the East coast. Apparently these storms were triggered by global warming, which paradoxically causes extreme cooling in New York. Cue Jake Gyllenhaal to come to the rescue. Sounds crazy, right? Well, fear not, it is indeed complete hogwash. But the basic premise of the movie, that a major reorganization of the ocean circulation can make some places on Earth much warmer while other places become much colder, is basically right. In the surface 200 m or so of the ocean currents are driven by wind, making waves that can cause a lot of havoc along the Jersey Shore when a stiff Nor’easter blows. But in the rest of the ocean—and there’s another 3.4 km to go before reaching the seafloor—it is tiny differences in temperature and salinity (and therefore density) that sets currents into motion. That’s why a thermometer and a salinometer are the two most important instruments for a physical oceanographer. With just those two measurements we can follow the water through all the major ocean basins. This constant movement of deep currents brings warm water from the tropics to the higher latitudes and cold water back towards the equator, a process that Wally Broecker at Lamont termed "the ocean conveyor belt". And it is this heat transport that prevents New York from turning into a frozen tundra. So now lets talk about the 2000 flick "The Perfect Storm"... or maybe let's not. Although it does have George Clooney in it.