The water in the North Atlantic sinks because it's cold, but also because it's salty. Being both cold AND salty makes it really heavy, so it can sink very far. But if too much ice melts in the North Atlantic, the water could become less salty. If that happens, what about the Ocean Conveyor Belt? Would it stop warming the North Atlantic? Could Europe get really cold? Scientists say it seems unlikely, but NASA satellites are keeping a close eye on the melting ice and the ocean currents to try to understand this complicated system better.