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Chemical Oceanography, 4th Edition
wind field are further south. This limits the effectiveness of the winds to transfer warm
subtropical water to the North. This may be a response to large- scale factors. The density
of the North Pacific is thus reduced by lower evaporation at the lower temperatures. The
inflow of water into the North Pacific matches the Ekman- induced upwelling in the subpolar gyre. The surface waters of the Pacific have a lower density because of the decrease
in salinity caused by lower evaporation. In the North Atlantic, the densities are higher
because of the increase in evaporation. This allows for deep- water formation.
Recent studies have suggested that a number of areas of the world ocean have higher or
lower salinity due to evaporation and precipitation. Measurements with 3500 Argo floats
Aquarius
Aug. 25 – Sept. 11, 2011
Figure 1.11
Salinity of ocean surface waters from satellite.
Latitude
–60
–40
–20
0
20
40
60
Salinity
33
34
35
36
37
Salinity
Evap-Ppt
100
–100
0
Evaporation - Precipitation, cm/y
Figure 1.12
Surface salinity compared to evaporation minus precipitation (cm yr –1 ).