Physical properties of sea water 2.7.9



	You are here:		Chapter: 2 General physics Section: 2.7 Astronomy and geophysics SubSection: 2.7.9 Physical properties of sea water

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2.7.9 Physical properties of sea water

The properties of sea water are a function of temperature, salinity (i.e. total dissolved solids in g kg⁻¹) and pressure. For the sources of the data see M. Hill (ed.), The Sea, vol. 1, chap. 1 and vol. 4, pt. 1, chap. 18 (Wiley) and Cox et al., Deep Sea Res., 1970, 17, 679. For chemical composition see section 3.1.3.

Density ρ of sea water at atmospheric pressure

Temperature

°C

Salinity/(g kg⁻¹)

(ρ/kg m⁻³ − 1000)*


0 . . . . . . . . .	16.04	20.06	24.08	28.10	32.14
5 . . . . . . . . .	15.84	19.78	23.73	27.68	31.64
10 . . . . . . . . .	15.31	19.18	23.07	26.96	30.86
15 . . . . . . . . .	14.48	18.30	22.13	25.97	29.82
20 . . . . . . . . .	13.39	17.17	20.96	24.75	28.56
25 . . . . . . . . .	12.07	15.82	19.57	23.34	27.12

* In oceanographical work these data are always expressed in terms of 1000(S − 1) where S is the density relative to water at 4 °C. Values for this can be obtained by adding 0.03 to the values in the table.

Density ρ of sea water at 0 °C and salinity 35 g kg⁻¹

Pressure/MPa	0	20	40	60	80	100
(ρ/kg m⁻³ − 1000)	28.10	37.44	46.37	54.92	63.12	71.02

Mechanical and thermal properties of sea water at salinity 35 g kg⁻¹ and atmospheric pressure (unless otherwise stated)

Property

0 °C

20 °C


Dynamic viscosity . . . . . . . . . .	1.88 × 10⁻³ Pa s	1.08 × 10⁻³ Pa s
Kinematic viscosity, ν . . . . . . . . .	1.83 × 10⁻⁶ m² s⁻¹	1.05 × 10⁻⁶ m² s⁻¹
Thermal conductivity . . . . . . . . .	0.563 W m⁻¹ K⁻¹	0.596 W m⁻¹ K⁻¹
Thermal diffusivity, κ . . . . . . . . .	1.37 × 10⁻⁷ m² s⁻¹	1.46 × 10⁻⁷ m² s⁻¹
Prandtl number, ν/κ . . . . . . . . .	13.4	7.2
Specific heat capacity, C_p . . . . . . . . . .	3985 J kg⁻¹ K⁻¹	3993 J kg⁻¹ K⁻¹
Thermal expansion coefficient . . . . . . . .
Pressure = 0.1 MN m⁻² . . . . . . . . .	52 × 10^{− 6} K^− 1	250 × 10⁻⁶ K⁻¹
Pressure = 100 MN m⁻² . . . . . . . . .	244 × 10^{− 6} K^− 1	325 × 10⁻⁶ K⁻¹
Ratio of specific heat capacities, C_p /C_v . . .	1.000 4	1.010 6
Velocity of sound* . . . . . . . . . . . . . .	1449 m s⁻¹	1522 m s⁻¹
Compressibility . . . . . . . . . . . . . . . .	4.65 × 10⁻¹⁰ Pa⁻¹	4.28 × 10⁻¹⁰ Pa⁻¹
Freezing point . . . . . . . . . . . . . . . .		− 1.910 °C
Boiling point . . . . . . . . . . . . . . . .		100.56 °C
* See also section 2.4.1.

Electrical conductivity γ of sea water at atmospheric pressure

	Temperature	Salinity / (g kg⁻¹)
	°C	20	25	30	35	40
		20	25	30	35	40
		γ / (S m⁻¹ )
0 . . . . . . . . . . . . . . .		1.745	2.137	2.523	2.906	3.285
5 . . . . . . . . . . . . . . .		2.015	2.466	2.909	3.346	3.778
10 . . . . . . . . . . . . . . .		2.300	2.811	3.313	3.808	4.297
15 . . . . . . . . . . . . . . .		2.595	3.170	3.735	4.290	4.837
20 . . . . . . . . . . . . . . .		2.901	3.542	4.171	4.788	5.397
25 . . . . . . . . . . . . . . .		3.217	3.926	4.621	5.302	5.974

At a depth of 4000 m the bottom water (about 0 °C, salinity 35 g kg⁻¹) has a conductivity 6% greater than the surface water. The mean conductivity of the oceans (excluding the shallow seas) is 3.27 S m⁻¹.

Sir Edward Bullard

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