Long Range Connections in the Weather
Scientists have recently learned that the average sea surface temperatures rise and fall over the entire North Atlantic in a predictable way. Every sixty-five to eighty years the surface waters from the equator north to Greenland switch from a cold mode to a warmer mode. When the North Atlantic is in its warm mode, as it was during the 1860s, the 1940s, and the present, most of the U.S. receives less than average rainfall. The El Niño in the Pacific Ocean also cycles from warm to cold but with a period of three to five years; it affects the weather patterns in parts of North and South America, Africa, Australia and Southeast Asia. We now know that the North Atlantic Multidecadal Oscillation (AMO) can add to or subtract from El Niño effects depending on whether it is in its warm or cool phase. We spoke with David Enfield about our evolving understanding of the connections between the oceans and the weather.