Gulf Stream eddy characteristics in a high‐resolution ocean model

A detailed statistical study of the mesoscale eddy activity in the Gulf Stream (GS) region is performed based on a high‐resolution multidecadal regional ocean model hindcast. An eddy detection and tracking method that can be used to capture eddy features from large datasets is presented. This method is applied to the 50 year model hindcast within a domain with the most energetic eddy activity along the GS. Detection results are then analyzed to investigate the kinematic properties and temporal variability of GS mesoscale eddies. The studied kinematic properties include the eddy size, duration, intensity, propagation, and spatial distribution. On average, cyclonic eddies are smaller in size but more energetic and remain coherent longer than anticyclonic ones. Cyclonic eddies generally travel further from the generation sites and have a strong tendency for westward propagation with a small equatorward deflection. Anticyclonic eddies remain near their generation locations and tend to propagate northward. The temporal evolution of eddy properties for long‐lived eddies (lifetime >90 days) is also examined. For both cyclonic and anticyclonic eddies, the size increases rapidly to their maximum value within the first 20 days at which point they begin to slowly decay. In terms of intensity, cyclonic eddies show a quasi‐linear decay while the anticyclonic ones reach a quasi‐steady state after 3–4 months of a more rapid decay. Finally, the seasonal variability of the GS mesoscale eddies is explored. In autumn and winter, both types of eddies are more numerous and larger but less intense, while in spring they are more intense but less numerous and generally smaller. Several possible mechanisms, including the wind stress, thermal forcing, and topographic influence, are considered to explain the seasonal cycle of eddy variability.