This map that represents the temperature of the oceans can easily relate to a map that would be representing the salinity of the oceans, and that is due to the correlation of the temperature and the salinity of the water.
The warmer the water is, the higher the salinity is, and vice versa, the lower the temperature of the water, the lower the the salinity.
On this map, we can see that the places like the Timor Sea, Arafura Sea, and the northern part of the Coral Sea, all have higher temperatures than most of the surrounding waters, and the main reasons for that are that they are under the influence of warm ocean currents, the waters are shallow, and they are close to the equator. In turn, that would mean that they have higher evaporation of the water, which contributes to bigger concentration of the salt, thus the water is more salty than on the other places.