The chemical composition of the ocean is determined by rivers, submarine hot springs, and ocean sediments that add or remove elements to seawater.
Throughout the oceans, the more abundant elements have near constant
ratios to salinity (a measure of total dissolved salts).

The Atlantic meridional overturning circulation (AMOC) transports warm salty surface waters to high latitudes, where they cool, sink and return southwards at depth. Through its attendant meridional heat transport, the AMOC helps maintain a warm northwestern European climate, and acts as a control on the global climate.