Four factors which determine the direction of flow of ocean current are
(i) Planetary winds
(ii) Temperature
(iii) Salinity
(iv) The Earth's rotation
(i) Planetary Winds: Between the equator and the tropics, the Trade Winds move equatorial water polewards and westwards and warm the eastern coasts of continents, e.g the North - East Trade winds move the North Equatorial current, Florida current and Gulf stream Drift, to warm the Southern and Eastern coasts of U.S.A.
(ii) Temperature: Because of the difference in temperature of ocean waters at the equator and at the poles the warm water is,lighter and rises and the cold water is denser and sinks hence warm equatorial water moves slowly along the surface poleward and the cold water moves equatorwards.
(iii) Salinity: Water of high salinity are denser than water of low salinity hence water of low salinity flows on the surface of water of high salinity
(iv) Rotation of the earth: The earth rotates from west to east and causes the ocean water to deflect to the right thereby making ocean water to deflect in a clockwise direction in the Northern hemisphere and anticlockwise in the Southern hemisphere.
(b) Effects of ocean current on the climate of the adjacent coastal areas,
(i) Warm current raise the temperatures of adjacent lands
(ii) Warm current brings regular and heavy rainfall to the coastlands
(iii) Warm current helps to keep ports in polar region free from ice
(iv) Cold current causes aridity and desert e.g Benguela current of west coast of South Africa causes Namid desert
(v) The meeting of two different current (i.e cold and warm currents) is a blessing as it results in the growth of planktons where fishing can be done.