[Solved] How do ocean currents and water masses differ in their impacts on marine life and coastal environment? Give suitable examples? (UPSC GS-1 mains 2019)

The ocean water is dynamic. Its physical characteristics like temperature, salinity, density and the external forces like the sun, the moon and the winds influence the movement of ocean water. Ocean currents are the continuous flow of huge amount of water in a definite direction. Water moves ahead from one place to another through ocean currents.

  • The ocean water is dynamic. Its physical characteristics like temperature, salinity, density and the external forces like of the sun, moon and the winds influence the movement of ocean water.
  • Ocean currents are the continuous flow of huge amount of water in a definite direction.
  • An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect and temperature and salinity differences.
  • An ocean current flows for great distances which play a dominant role in determining the climate of many of Earth’s regions.
  • Water mass, a body of ocean water with a distinctive narrow range of temperature and salinity and a particular density resulting from these two parameters.
  • Water masses are formed as the result of climatic effects in specific regions i.e. water mass is a body of water which has physical properties distinct from surrounding water
  • Water moves ahead from one place to another through ocean currents. Ocean currents has direct impact on the climate and economy of the region.

 Common water masses in the world ocean are: Antarctic Bottom Water (AABW), North Atlantic Deep Water (NADW), Circumpolar Deep Water (CDW), Antarctic Intermediate Water (AAIW), Subantarctic Mode Water (SAMW), Arctic Intermediate Water (AIW), North Pacific Intermediate Water (NPIW), the central waters of various oceanic basins, and various ocean surface waters.

 Ocean currents have direct impact on the climate and economy of the region. Ocean currents and water masses differ in their impacts on marine life and the coastal environment in different ways:

 • Impact on biodiversity – The physical parameters of water masses are essential because they structure the water masses and determine the various habitats that provide the environmental conditions required for marine life.

 –These conditions influence the production and the growth of plankton and fish species. The dispersion and dwelling of larvae for many benthic and pelagic species depend on hydrographical factors. They

 also play an important role for the exchanges between the sea and the atmosphere and between the various layers of water.

 –Ocean currents also have direct impact on the marine biodiversity. For example, mixing of ocean currents become a ground for fishing. Best example is eastern USA coast.

 • Osmo regulation and fertility– Water masses formation and location of its formation has direct bearing on the marine biodiversity as salinity and temperature of water masses change with its location.

 –While ocean currents also change the salinity of coastal region which changes the marine biodiversity, it has direct bearing on temperature of region also.

 Best example is north Atlantic drift of Atlantic region. Due to north Atlantic drift, Murmansk port of Russian region remain ice free.

 • Impact on corals. Formation of water masses near the region of corals can destroy the coral region of world.

 Deep coral will be more impacted by the formation of deep ocean water masses.

 • Impact on climate of regions. Impact of ocean currents has more bearing on the climate of the region. For example, north Atlantic Drift has direct bearing on climate of whole Europe region. Deccan currents have direct bearing on the whole climate of the world, for example- El-Nino, while ocean water masses have less impact on the climate. However, in the recent time melting of glaciers and global warming have had

 considerable impact on marine life.

 • Latitude heat balance. Ocean currents have key role in transferring heat from tropical regions to higher latitudes. This helps in rainfall and climate of higher latitudes. Also, ocean currents bring colder water from polar regions to tropical regions.

 Warm currents traveling along temperate coasts increase the temperature of the area.

 Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude.

 • Cold ocean currents have a direct effect on desert formation in west coast regions of the tropical and subtropical continents. Example- Peru( Humboldt), Canary Current • Warm ocean currents bring rain to coastal areas on the east coasts of the continents in tropical and subtropical latitudes. This results in warm and rainy climates.

 • Mixing of cold and warm ocean currents bear richest fishing grounds in the world. Example: Grand Banks around Newfoundland, Canada and North-Eastern Coast of Japan.

 • The mixing of warm and cold currents help to replenish the oxygen and favor the growth of planktons, the primary food for fish population. The best fishing grounds of the world exist mainly in these mixing zones.

 • The cold currents from Artic bring large ice mass from polar region which act as hindrance to the ship navigation.

 • Also the fog formation in the region of mixing of warm and cold water current hinders navigation.

 • The gyre circulation help in maintaining the latitudinal heat balance.

 • Antarctic bottom water is an important water mass that forms on the Antarctic continental shelf as a cold, dense residual brine during the formation of sea ice. Its salinity of 34.62 parts per thousand and temperature of -1.9° C result in a high density of 1.027grams per Mediterranean water is another example of a water mass. Excessive evaporation, low rainfall, and high temperatures continually generate large volumes of warm, salty (36.5 parts per thousand) water. Its high density causes it to sink to the bottom of the Mediterranean and overflow across the submarine sill at the Strait of Gibraltar, from this place it sinks and spreads at a depth of about 1,000 metres in the Atlantic.

Conclusion: Water masses have more bearing on the deep sea marine biodiversity as deep water masses have direct bearing on these species, while ocean currents have very less bearing on deep sea water species. Further, ocean currents and their impact have been studied in much detail while the impact of water masses need to be studied more elaborately. Further scientific studies must be carried out to study the impact of these two phenomena.

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