Discuss the effect of ocean currents on movement of water to different parts of the globe. Show how the gulf stream emerges and warms most of the east coast of the USA. Discuss the driving of ocean currents. Explain how tropical water is warmer and raises the surface water by about 8 cm. Discuss gyres as large scale patterns of water circulation in the N and S hemispheres. Explain upwellings. Explain thermoline circulation and the effect warmer water has on western Europe.