How are ocean current produced?

Answer 1

I am not an oceanographer but I imagine there are several different processes which occur to make currents (as currents can from at very different spatial scales).

Large scale processes could be:

1) atmospheric circulation (e.g Hadley cell) - caused by temperature gradients.

2) temperature gradient on the oceans.

small scale processes could be:

1) wind

2) salinity gradients

3) changes in ocean topography

I hope someone will expand on my simple, hypothesised, answer.