Under average conditions the trade winds blow east to west across the tropical. In the eastern pacific the water temperature rises and there is greater precipitation in the eastern pacific, and sometimes flooding in south. American countries such as peru: el ni o also favors drought conditions in indonesia and australia. El ni o / la ni a - galapagos: currents causing upwelling reverse during el ni o resulting in barren conditions, currents causing upwelling are strengthened by la ni a, resulting in return of diversity. El ni o brings severe weather: severe el ni o events occur irregularly, about once every 10-12 years, consequences of severe el ni os: Drought in tropical south america, africa, and australia increased precipitation outside of tropics. Disruption of fisheries and seabird populations (upwelling nutrients stop) Thermohaline circulation: a global pattern of surface- and deep-water currents that flow as a result of variations in temperature and salinity that change the density of water.