North Atlantic Oscillation and variability of characteristics of the upper oceanic layer

Variability of sea surface temperature (SST) and heat content of the upper 200-m layer in the North Atlantic and cross correlations of these characteristics with the North Atlantic Oscillation (NAO) index are analyzed on the basis of data from the National Oceanographic Data Center for the postwar period. The goal of the analysis is to detail a mechanism of the maintenance of the NAO. It is shown that NAO variability with a typical period of 5 to 10 years is a coupled oscillation in the North Atlantic ocean-atmosphere system. The typical lag of an oceanic response to an atmospheric forcing (NAO) is I to 3 years for different regions of the tropical, subtropical, and subpolar gyres. The entire cycle of the interaction of the NAO with upper-layer temperature anomalies including their advection is 6 to 8 years. This gives rise to a spectral peak in most analyzed time series at corresponding frequencies. The interaction between the ocean gyres, including meridional advection of the anomalies, is also important in maintaining the NAO.