What are surface currents caused by

The amount of wind seems like the most possible cause for surface currents. I believe temperature has a little something to do with it as well. Fill a clear dish with water and gently blow. You'll notice waves. Try blowing across it a second time with a little more force. You'll see even bigger waves. Vibrations in the earth also can contribute to waves ... earthquakes or any kind of seismic activity can cause surface currents as well.