Climatic and oceanic conditions at Bermuda can be considered sub-tropical. Unlike the tropics, there is a marked distinction between summer and winter seasons. However, the climate is moderated somewhat by a mass of seawater at 18o C (degrees Centigrade) which persists throughout the year. In the winter, it extends from the sea surface down to a depth of approximately 450 m (1500 ft). From late spring, the layer is gradually displaced, downwards, by warmer sea water, with a thermocline (vertical transition in temperature) at approximately 100m, below which the 18o C waters are temporarily restricted .
Bermuda is situated on the western edge of the Sargasso Sea, which is a water mass defined by relatively high salinities, high water temperatures and low current velocities. It is bordered by vast oceanic “gyres” namely the westward flowing North Equatorial Current to the south and the eastward flowing North Atlantic Current to the north. Also, forming part of this largely wind-driven system of surface water circulation is the Gulf Stream, which carries warm waters northward between Bermuda and the east coast of the USA.
Sargassum (shown pictured on the South Shore of Bermuda) is a brown, rough textured “sea weed”, or algae, which grows and floats free on the deep ocean waters of the Sargasso Sea. It has berry-like gas filled bladders which help keep it afloat. It provides a unique ecological niche for a variety of marine organisms.