GRE Reading Comprehension question

[theol]

In a plausible but speculative scenario, oceanographer Douglas Martinson suggests that temperature increases caused by global warming would not significantly affect the stability of the Antarctic environment, where sea ice forms on the periphery of the continent in the autumn and winter and mostly disappears in the summer. True, less sea ice would form in the winter because global warming would cause temperatures to rise. However, Martinson argues, the effect of a warmer atmosphere may be offset as follows. 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. Less salty surface waters would be less dense and therefore less likely to sink and stir up deep water. The deep water, with all its stored heat, would rise to the surface at a slower rate. Thus, although the winter sea-ice cover might decrease, the surface waters would remain cold enough so that the decrease would not be excessive.


The passage suggests that Martinson believes which of the following about deep waters in the Antarctic region?


A) They rise to the surface more quickly than they would if global warming were to occur.
B) They store heat that will exacerbate the effects of increases in atmospheric temperatures.
C) They would be likely to be significantly warmed by an increase in atmospheric temperatures.
D) They would be more salty than they currently are if global warming were to occur.
E) They are less likely to be stirred up when surface waters are intensely salty than when surface waters are relatively unsalty.


The answer is A.


I don't understand why the answer cannot be B because it mentions that "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. Less salty surface waters would be less dense and therefore less likely to sink and stir up deep water. The deep water, with all its stored heat, would rise to the surface at a slower rate.", so the deep waters come with the heat that increases the the atmospheric temperatures.

 

[Skrej]

It's not that Martinson doesn't believe B to be true, it's just that Martinson actually believes that B is less likely to happen because:

Global warming = less sea ice forming
Less sea ice = smaller increase in salt concentration
Less salt concentration = less dense water
Less dense water = less water sinking
Less water sinking = less stirring up deep water with heat
Less deep heat water rising = less heat released in atmosphere

Martinson believes that less ice forming due to global warming equals less heat brought up from the deep water.

 

[Tdol]

Offset seems to be key to this to me.