Explain how the density of ocean water is affected by temperature and salinity and how this results in
major ocean currents distributing heat away from the equator toward the poles.

Salinity is the amount of dissolved chemicals in the ocean water (this is primarily sodium chloride, or salt). These chemicals enter the ocean from streams and rivers flowing into the sea. The higher the salinity, the denser the water is. Temperature also affects ocean water density and through this, ocean [convection] currents. Warm water will rise and cold will fall, resulting in rotating currents of water.
KNOW THAT:
Ocean currents are constantly moving warm water away from the equatorial region and toward the poles.
Similarly, currents move cold water from the poles toward the equator.