what causes the sinking of water in the northern atlantic ocean, which to drive the ocean conveyor belt?

a) the low salinity water coming from the south gains salt and becomes more dense.

b) the high salinity water coming from the south warms and becomes less dense.

c) the high salinity water coming from the south cools and becomes more dense.

d) the low salinity water coming from the south looses salt and becomes less dense.