The figure below shows the formation and sinking of dense water in the Arctic Ocean between Greenland and northwest Europe. Why
is there an increased density of surface waters in this region? A. Evaporation decreases salinity, and heavy polar air increases atmospheric pressure.
B. Evaporation decreases salinity, and cool atmospheric temperatures decrease water temperature.
C. Formation of sea ice increases salinity, and heavy polar air increases atmospheric pressure.
D. Formation of sea ice increases salinity, and cool atmospheric temperatures decrease water temperature.
Answer: The correct option is A. Evaporation decreases salinity, and heavy polar air increases atmospheric pressure.
The ocean circulation conveyor belt or the thermohaline circulation of sea water that circulates massive water currents from northern to southern oceans and again back. The warm water on releasing heat becomes denser and sinks down. This closed circulation loop makes the cold water move towards the tropical region at the deeper levels.
The decrease in salinity results due to evaporation. The density of sea water depends on pressure, temperature and salinity. Density increases when temperature decreases and salinity increases. The wind field pattern is formed from the warm ascending air from the low atmospheric pressure in tropical region and high atmospheric pressure from the cool descending air in subtropical region.
In the Arctic region dense sinking surface water is counteracted by the release of fresh water due to melting of ice and a high atmospheric pressure. The low temperature in the polar region makes the air heavy and is forced to descend which causes high pressure zone.
