Why would changes in temperature and salinity of NADW or ABW affect thermohaline circulation of global ocean?

Question

NADW- North Atlantic Deepwater
ABW- Antarctic Bottom Water

How might NADW be altered if temp and/or salinity change?

Answer 1

Saline water has a higher density, as does colder water (until a few degrees before it freezes). A large change in the amount of fresh water entering the ocean (such as melting or forming glaciers and ice sheets) could alter both or either, as could an increase in the rate of evaporation from the ocean surface.

The change in density would alter the efficiency of convection that allows the exchange of cool and warm water between the surface and deeper zones.... which of course is a major driving force in some important ocean currents.

One possible scenario is that a change in the salinity or temperature of the Atlantic could stop much of the circulation of the water, allowing stratification of the water and leading to anoxic conditions in the depths and the mass extincitions such changes bring.