Other major current systems

This chapter explores the equatorial systems, and the contrasting patterns of ocean circulation in northern and southern polar/subpolar regions. The chapter also shows how the natural oscillation of the North Atlantic atmosphere and ocean appears quite subdued when compared with that of the more closely coupled atmosphere and ocean of the Tropical Pacific. The major components of equatorial current systems are westward flowing North and South Equatorial currents, one or more eastward flowing counter-currents, and an eastward flowing Equatorial undercurrent, which is generally centered on the Equator.. The equatorial current system is best developed in the Pacific Ocean, where the surface waters are under the cumulative influence of the prevailing Trade Winds over the greatest distances. The winds over the Indian Ocean change seasonally as a result of the differential heating of the ocean and the Asian landmass. The most dramatic seasonal change in the surface circulation of the Indian Ocean is the reversal of the Somali Current, which flows south-westwards during the North-East Monsoon but is a major western boundary current during the South-West Monsoon. The Agulhas Current is the next most powerful western boundary current, second only to the Gulf Stream. Similarly, the major current feature of the Southern Ocean is the Antarctic Circumpolar Current (ACC), which, by virtue of its great depth, has an enormous volume transport.