Calculation of nonlinearity parameter for seawater

The nonlinearity parameter B/A of seawater from 25%o to 40%o has been calculated in the temperature range from 0° to 35 °C and at pressure of up to 1000 bars by use of the acoustic and thermodynamic approaches. Their agreement with an accuracy of 2% is within ±0.1 over most of the range from 0° to 35 °C up to 800 bars. The ratio B/A at each concentration increases monotonically with pressure in the range covered. The increase rate at higher temperatures becomes slower than that at low temperatures. It is found that the B/A at low pressure increases with increasing temperature, and at higher pressures decreases. However, the quantity B/A at moderate pressure near 500 bars is relatively insensitive to temperature changes and then reveals a small temperature minimum. Although the B/A at a fixed P and T increases with increasing salinity, the increment of B/A decreases as pressure increases. To find a relationship between B/A and T or P, we obtained the thermodynamic expressions for [∂(B/A)/∂T]P and [∂(B/A)/∂...