The Gulf Stream is an important ocean current that surges northward along the eastern coast of North America. It has had a tremendous influence on climate, marine life and early exploration of the New World. In his new book, “The Gulf Stream: Tiny Plankton, Giant Bluefin, and the Amazing Story of the Powerful River in the Atlantic,” Stan Ulanski, a geology professor at James Madison University, shares the story of the mighty Gulf Stream, past and present.