There are actually currents within the Ocean itself (ie, it's like some big pond or bathtub)...Just like the atmosphere is moving around hot and cold air to balance things around (which is really the basis for all weather)...The Oceans do the same thing. The ocean itself has currents within it to transport warm water poleward and cold water equator-ward. The fact that the Earth has an axial tilt and is unevenly heated by the Sun during the course of the year really forces this to happen.

Anyway...There are warm currents and cold currents. An example of a cold current would be the "Laborador Current" which was responsible for kiting some icebergs into the path of the Titanic...among its general function of bringing cold ocean water down through the Maritimes and mix out with the water it finds.

The warm ocean currents are always associated with storm development. Hurricanes need warm water to intensify, and storm systems themselves benefit from said currents. It's the reason why we get all these 'noreasters and why storms really balloon off the Carolina Coast.

It's also why hurricanes stay alive a long time going up the eastern seabord, and why they NEVER go up the California coastline. You'll often see a storm like a hurricane, once it finds itself in the Gulf Stream, it'll adjust its course to follow along the nice water temperatures, making it seemingly 'curve away' from the coast, often sparing citizens of impending disaster...

...or bumming out the guy who drove 8 hours overnight to see himself some good wind action. :)