How do oceanographers measure the salinity of ocean water?

Oceanographers measure the salinityof ocean water by using a hydrometer, a hydrometer set, a chemical test kit or a salinometer. A hydrometer is a quicktest tool used in aquariums, and it works by reading the water density. Higher dissolved salts result in higher density.
Hope this helps.

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.

Ansarabs took control;