7.7: Salinity and Latitude

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Miracosta Oceanography 101
Miracosta)

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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.

Figure 7.24. Map of net evaporation minus precipitation (E-P) on oceans.

Evaporation and Precipitation curves by latitude — Figure 7.25. Evaporation and precipitation curves compared with latitude.

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:
• Precipitation • Runoff • Melting icebergs/sea ice	• Evaporation • Freezing sea ice