It is formed by the convergence of the Antilles and Caribbean currents.  
Most subtropical cyclones form along the margins of this natural phenomenon that marks Nantucket   Island as a marine biodiversity boundary. Lemon trees can grow in Devonshire, England because of  this phenomenon's effect on climate, which also keeps the coast of Norway ice- free through the winter.   First mapped by Ben Franklin, it explains why ships take less time to sail from North America to  Europe than the reverse trip. It is formed by the convergence of the Antilles and Caribbean currents.  Name this large, warm-water current that flows up the east coast of the US and across the North  Atlantic.
Most subtropical cyclones form along the margins of this natural phenomenon that marks Nantucket   Island as a marine biodiversity boundary.
{Gulf Stream} [prompt on oceanic currents]