Salinity and Latitude
Figure 7.24 is a map of the globe comparing the rates of evaporation and precipitation. The map is a compilation of evaporation minus precipitation (E-P) values. The data basically shows the regions where there is a net gain of salinity created in surface waters by high evaporation rates. There is also a net loss of salinity where precipitation is higher than evaporation rates (Figure 7.25). In general:
• The tropics (equatorial region) is humid and cloudy, and receives much more rain than evaporates.
• The temperate regions receive less precipitation, so evaporation dominates.
• The polar regions have low evaporation rates relative to the amount of precipitation they receive.
Variability of ocean salinity: Ocean salinity is stable at depth but can be highly variable at the surface. The upper surface layers of the ocean impacted by wave energy is a mixing zone. Simply this: the more waves, the more mixing. Freshwater is less dense than seawater and without mixing freshwater will float (stratify) on top of seawater.
|Factors that decrease salinity:
||Factors that increase salinity:
• Melting icebergs/sea ice
• Freezing sea ice