Icelandic Low and Azores High Migrations Impact Florida Current Transport in Winter.

Previous work by Meinen and coworkers to find an association between variations of annually averaged Florida Current transport (FCT) and the North Atlantic Oscillation (NAO) has yielded negative results. Here we show that the Florida Current in winter is impacted by displacements in the positions of the Azores high and the Icelandic low, the constituent pressure centers of the NAO. As a one-dimensional representation of North Atlantic atmospheric circulation, the NAO index does not distinguish displacements of the pressure centers from fluctuations in their intensity. FCT is significantly correlated with Icelandic low longitude with a lag of less than one season. We carried out perturbation experiments in the ECCOv4 model to investigate these correlations. These experiments reveal that east–west shifts of the Icelandic low perturb the wind stress in midlatitudes adjacent to the American coast, driving downwelling (through longshore winds) and offshore sea level anomalies (through wind stress curl) that travel to the Straits of Florida within the same season. FCT is also correlated with the latitude variations of both the Icelandic low and the Azores high with a lag of 4 years. Regression analysis shows that latitude variations of the Icelandic low and the Azores high are associated with positive wind stress curl anomalies over extended regions in the ocean east of Florida. Rossby wave propagation from this region to the Straits of Florida has been suggested as a mechanism for perturbing FCT in several previous studies by various researchers, as detailed in sections 4b and 5. [ABSTRACT FROM AUTHOR]