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P as a function of S,T(P = 0 db) P as a function of P,T(S = 35)

P as a function of S,T(P = 0 db) P as a function of P,T(S = 35)

Fig. 2.8 Haline contraction coefficient (10 4/psu): a as a function of (S,T); b as a function of (P,T).

2.4.4 Specific heat capacity

Specific heat capacity differentiates in two different cases. First, if heating/cooling takes place under a constant pressure, we have cp=( £)„ = T( £)„ (175)

which is the specific heat capacity under constant pressure. Second, if heating/cooling takes place with a constant volume, we have c-=( i) „ - t(£) ,„ <2-76»

which is the specific heat capacity with constant volume. These two types of specific heat are related through the following relation

T a2

P\ dP / T,s is the isothermal compressibility of the fluid. Although seawater is almost incompressible, nevertheless its density can change, and therefore maintaining a constant specific volume is not a good assumption. As a result, the specific heat capacity under constant pressure is most commonly used.

2.4.5 Compressibility and adiabatic temperature gradient

The compressibility of a fluid can be defined in two ways. First, assuming that temperature remains constant during the compression, we obtain the compressibility under constant temperature, KT. Second, assuming that the entropy of the fluid remains constant, i.e., the process is adiabatic and reversible, we obtain the compressibility under constant entropy, Kn. Thus

The compressibility is closely related to the speed of sound waves c = ^(dP/dp)n.

bp]n d(P, n) d(T,P)d(P, n)/d(T,P) \dt dp dt dPj dn/dT

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