Calm centre of the anticyclonic gyre in the N. Atlantic. This large eddy of surface water has boundaries demarcated by major current systems such as the Gulf Stream, Canary Current, and North Atlantic Drift. The Sargasso Sea is a large, warm (18 °C), saline (36.5–37.0‰) lens of water, which is characterized by an abundance of floating brown seaweed (Sargassum).