12
Chemical Oceanography, 4th Edition
The temperature and salinity of ocean waters control the density. The change in the
density with depth is important because it determines the water’s static stability. When
the stability is high, vertical mixing is minimized. The density of ocean waters is normally
characterized by the symbol σ T , which is called sigma- T. This quantity is related to the
density (ρ, kg m –3 ) of seawater by
σ T = (ρ – 1) 10 3
(1.1)
The density of seawater as a function of salinity S and temperature T (°C) and pressure
(P, bar) can be calculated from the international equation of state (Millero and Poisson,
1981; Millero et al., 1980) given in Table 1.2. More is said about the new Thermodynamic
40°S
20°S
EQ
20°N
4000
5000
6000
Depth [m]
3000
2000
1000
0
Salinity [pss-78]
Atlantic Ocean A16
40°N
60°N
36.5
37
36
35.5
35
A16
34.5
34
Ocean Data View
Figure 1.14
North- south section of salinity in Atlantic Ocean.
36.5
36
35.5
35
34.5
34
33.5
33
Ocean Data View
40°N
20°N
EQ
20°S
40°S
Pacific Ocean P16
0
1000
2000
3000
P16
Depth [m]
4000
Salinity [pss-78]
Figure 1.15
North- south section of salinity in Pacific Ocean.