The Nature of Ocean WaterSea water makes up the largest store of water in the
hydrologic cycle. It is comprised of nearly 60 chemical substances with
common salt being the most abundant, 78% of the dissolved solids. Ocean
salinity varies from 32 - 37 parts per thousand. Salinity is lower near
land and in the polar regions (30 ppt). A number of factors determine ocean salinity. Salinity is lower where freshwater rivers enter the ocean. In the North Pacific precipitation exceeds evaporation thus diluting ocean water. Water is more saline in subtropical oceans where evaporation exceeds precipitation. The Atlantic ocean is the most salty while the Arctic ocean is the least. The oceans exhibit three vertical temperature zones, 1) a surface
layer of water water, 2) a transition zone of decreasing temperatures
with depth, and 3) the cold waters of the deep ocean. The zone of
transition, known as the thermocline, is most noticeable where
surface water is warmest. Polar water may have no thermocline as the
surface temperature are very cold.. |
Figure
OC.4 Controls over ocean salinity. (Courtesy