Select all the primary causes of surface currents in the oceans. a. wind b. gravity c. earth's rotation d. extreme weather e. density differences f. uneven heating of oceans which of the following is an important effect of ocean gyres? a. moderation of earth's climate b. unequal distribution of water on earth c. transportation of goods across the oceans d. isolation of marine species into different ecosystems deep ocean water from the north arctic region warms and rises back to the surface again in the a. indian ocean b. southern ocean c. north atlantic ocean d. south atlantic ocean