Consider the method of acoustic thermometry using the ocean. In Example 13.8, we saw that very small changes in the travel time of sound can be detected and can be used to observe very small changes in the ocean temperature. There are, however, complications that we did not mention in that example. It turns out that the velocity of sound in water also depends on the salinity of the water. Ocean water contains about 3.5% salt by volume, and the speed of sound changes by about 1.4 m/s for each 0.1% change in the salt concentration. Investigate (using the Internet or some other reference) how much the salinity of ocean water fluctuates over time and discuss how much this fluctuation will affect the measurement of temperature changes with this technique.