Surface ocean currents are powered by wind and caused by Earth's rotation. The Gulf Stream flows northeast from Florida and curves east, keeping Iceland's climate mild. Cold currents like the California Current cause cool, foggy weather along western coasts. Density currents form when dense, salty water sinks and flows slowly along ocean floors. Changes to density currents from climate change could disrupt global ocean circulation and cause drastic climate shifts. Upwelling occurs along some coasts, bringing nutrient-rich deep water to the surface and fueling marine life.