Ocean Circulation

Temperature, salinity and density differences in ocean water are the prime causes of ocean water circulation. Elaborate. (200 Words)

 The deep ocean, devoid of wind, was assumed to be perfectly static by early oceanographers. However, it has been found with modern instrumentation that movement in deep water masses is frequent. In contrast to the wind over land, the major driving forces of ocean currents are differences in density and temperature.
Circumstances of ocean water circulation:
Role of Density: The ocean water is constantly churning underneath, bringing nutrients up to the top. The difference in density of cold water versus density of warmer water is responsible for ocean currents and up-welling. Warm seawater floats and cold (4°C ), dense (1 g/cm3), seawater sinks, so ocean temperatures also vary across the surface and into the depths.
Role of Salinity: Seawater is saturated with salts at 35 ppt and at 4°C the salinity causes the density to actually be 1.0278 g/cm3. This slightly heavier density is another contributing factor to up-welling as it causes the water molecules to roll over each other.
Role of Temperature: Temperatures range from -2°C to 28°C in most cases, but are hotter near hydro-thermal vents or closer to land. Salinity is usually 35 ppt (parts per thousand), but can range from 28-41 ppt and is highest in the northern Red Sea.
Thus, density, temperature and salinity provides for shuffling of layers which tries to balance into their most stable positions provides a driving force for ocean water circulation.
Describe and account for the surface currents of the Indian Ocean and explain how and why they differ from those of the Atlantic. (200 Words)
The current systems of the Indian Ocean are largely controlled and modified by landmasses and monsoon winds. Normally moving counter-clockwise, in the winter the Indian Ocean current reverses direction due to the seasonal winds of the South Asian Monsoon.
The currents in the northern Indian Ocean change their flow of direction twice a year due to north- east and south – west monsoon winds both are warm currents. Another two warms counter currents flows is easterly direction from Zanzibar to Sumatra. It disappears due to South West Monsoon Current. Mozambique Current moves  southward, it joins the Aughals current near 30 degree South latitude and moves up to tip of Africa.
Indian oceans currents flowing along the coasts modify their weather conditions in a number of ways. The warm currents, when they reach colder areas, do not allow their temperatures to fall rather they keep them relatively warmer in winter months.
Thus, there is a difference between The North Atlantic powerful Warm Ocean current that continues the Gulf Stream northeast. West of Continental Europe it splits into two major branches. But the Gulf Stream raises the temperature of Atlantic and Gulf Coastal plains of the USA during summer months and causes intensive heat waves (not in case of Indian Ocean currents).
While, Cold currents lower down the temperature of the affected areas considerably and thus cause snowfall, dense fog, etc.