Movements in the Oceanic Waters

Movements in the Oceanic Waters The movement of ocean waters takes place in three different ways: waves, currents and tides.

Ocean Waves Waves are oscillatory movements in water, manifested by an alternate rise and fall of the sea surface. Waves are mainly produced by winds. When blowing winds impart their energy to the water in the form of friction Md pressure on the surface of the sea, waves are produced. There are three types of wind-generated waves:
(i) Sea Several trains of differing wave lengths and directional movements of sea waves occur simultaneously in the oceans. It results into an overall irregular and chaotic wave pattern called the sea.
(H) Swell Swells are the regular undulating movement of the surface of the open sea. They result from waves that have moved out of the area in which they were generated and have ceased increasing in size.
(iii) Surf The breaking waves in coastal regions are called surf.

Ocean Currents The ocean currents are the most important of the movements in the oceanic water. The ocean current is the general movement of a mass of water in a fairly defined direction over great distances. Ocean currents can broadly be divided into two types: (i) warm current, and (H) cool or cold currents. Those that flow from equatorial regions polewards have a higher surface tem­perature and are warm currents. Those that flow from polar regions equatorwards have a lower surface temperature and are cold currents.
The origin and nature of the movement of the currents are related to four sets of factors. (i) factors related to earth's rotation (gravitational force and force of deflection), (ii) factors originating outside the sea (atmospheric pres­sure, winds, etc.), (Hi) factors originating within the sea (pressure, salinity, etc.), and (iv) factors modifying the ocean currents (direction and shape of the coast, seasonal variations, etc.).

In the Northern Hemisphere, the currents move to' their right and in the Southern Hemisphere to their left. However, as an exception, in the northern part of the Indian Ocean, the direction of currents changes in response to the reversal of the monsoon winds. Warm currents move towards the cold; seas and cold currents towards the warm oceans. The direc\ion of currents in the Northern and Southern Hemispheres is determined by Coriolis force or Ferrel's law.