(A) There is nothing mentioned about this here, clearly not correct.
(B) "The formation of sea ice causes the concentration of salt in surface waters to increase; less sea ice would mean a smaller increase in the concentration of salt." This is the important sentence to demonstrate why (B) is wrong. If global warming occurs, there is less sea ice. Less sea ice means a smaller increase in salt, and thus the surface waters are less salty if global warming occurs. This means that they are currently more salty than if global warming were to occur.
(C) "Less salty surface waters would be less dense and therefore less likely to sink and stir up deep water." Because the surface waters will be less salty if global warming occurs, therefore they are currently more likely to sink and stir-up the deep water. This is correct!
(D) Nothing outside of Antarctica is mentioned.
(E) This is backwards!
(A) "The deep water, with all its stored heat, would rise to the surface at a slower rate." This means that he believes that currently - without global warming - they are rising more quickly than if global warming were to occur. This is correct!
(B) He does not believe that the deep waters storing heat will exacerbate the effects - he believes they will mitigate them.
(C) This is not mentioned anywhere. All that is mentioned is that the deep waters have "stored heat." There is no mention of the temperatures being increased!
(D) The salinity of the deep water is never discussed - only the surface water.
(E) This is again the opposite. They are more likely to be stirred up when the surface waters are salty than otherwise.
Hopefully this makes some sense! Happy to clarify if needed!