The equatorial undercurrent: 100 years of discovery



The Equatorial Undercurrent is a narrow ribbon of eastward flow centered on the equator in the upper thermocline. It is a permanent feature of the general circulation in the Atlantic and Pacific oceans and is present in the Indian Ocean in northern winter and spring during the northeast monsoon. It reaches speeds of 50–100 cm s −1 below the westward flow of the South Equatorial Current, and in the Pacific transports as much mass on average (40×106 m3 s −1 ) as the Florida Current, which feeds the Gulf Stream.