Thermohaline circulation instead of wind friction drives the mid- to deep ocean currents. This type of circulation is powered by _________________.
a) Uneven solar input.
b) heat from the Earth's mantle altering the level of the pycnocline.
c) changes in water density that causes it to rise or fall through the water column.
d) all of the above.
e) answers a and c only.
Answer: E