The Gulf Stream can be thought of as a "river" in the ocean.

The Gulf Stream carries warm, salty water northward along the Northeast Shelf (Gulf of Maine to Cape Hatteras, NC), bringing heat from the tropics to higher latitudes.  The northward and landward extent of warm Gulf  Stream waters affects ecological processes  in the ocean, including the distribution of commercially important fish species. It also affects weather in the region. The Gulf Stream returns a considerable amount of heat to the atmosphere. 

Nor’easter storms are fueled by the meeting of cold Arctic air from land and warm air over the Gulf Stream and coastal waters. The trajectory of the Gulf Stream also influences storm tracks in the North Atlantic. 

Credit: NOAA