PHYSICS AND CHEMISTRY OF THE SEAS
Water, a unique compound without which there can be no life, is the main component of the seas. To understand and appreciate the myriad processes taking place in the seas, it is important to understand the physical and chemical properties of sea water, including those occurring at the global scale.
From space, the earth looks blue because it has more ocean than land. About 80 per cent of the earth's water is sea water, containing salts. It is from this combination of water, salts and simple organic molecules that life on earth originated. The salinity of the water in the Strait of Melaka is lower than that of other seas because it is diluted by large amounts of fresh water from rivers. Salinity levels have a bearing on the type of organisms present. Besides salts, sea water also contains sediments. These determine light penetration, and, again, the range of living organisms found. Both the amount of sediment and type of organisms present affect the colour waters appear. Coastal waters, such as those around the west coast of Malaysia, are often a dirty brownish green because of the presence of much sediment and plankton. Conversely, those to the east, in the South China Sea, are much clearer because they harbour much less sediment.
The gravitational pull of the sun and the moon creates tides, and because of the size, shape and shallow nature of the seas, Malaysia's tides are among the most complex in the world. The sun causes differential heating of the atmosphere, resulting in winds which, in turn, create waves. Differential heating of the oceans globally, combined with the earth's rotation, result in currents which keep sea water circulating, and also strongly influence the climate of the nearby landmasses. The monsoon winds are a good example of this action, and as Malaysia lies within the monsoon regime, seasonal characteristics in terms of waves, currents, sea surface temperatures and sea level variations are greatly affected. The northeast and southwest monsoons have had, and continue to exert, a major influence on the economy and culture of the country. The forces of the waves and currents help shape Malaysia's coastline and, in turn, the variety of habitats found along its shorelines—from strands of fine, golden sand to muddy, mangrove-lined estuaries.
Water moves around, or cycles, flowing as currents, evaporating from seas, and condensing as mist, cloud and rain. It moves with it both dissolved and small particles. Water also aids in the cycling of other materials like carbon and nitrogen. Disturbances of these biogeochemical cycles result in disruptive global changes.
El Niño is an excellent example of atmosphere–ocean interaction. Although this phenomenon has long been known to Peruvian sardine fishermen, it has only recently become familiar to Malaysians. El Niño is now known to affect much of the tropics, bringing coastal flooding and reduced fish stocks to the southeast Pacific, but drought to Southeast Asia, particularly Sabah and Sarawak.