El Niño-Southern Oscillation drives North Atlantic Oscillation as revealed with nonlinear techniques from climatic indices

Abstract

Based on the nonlinear techniques for estimation of coupling between oscillatory systems, we investigate the dynamics of climatic modes characterizing global and the Northern Hemisphere (NH) processes. In particular, indices of the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO) for 1950-2004 are analyzed. The methods based on phase dynamics modeling and nonlinear "Granger causality" are used. We infer that ENSO affects NAO during the last half a century with confidence probability higher than 0.95. The influence is characterized with time delay in the range from a couple of months up to three years and increases during the last decade. Copyright 2006 by the American Geophysical Union.