Circulation and Dynamics of the Western North Atlantic. Part II: Dynamics of Meanders and Rings

Abstract

A multiparameter kinematic synthesis of multiscale feature models for the circulation of the western North Atlantic was developed in Part I of this study. The dispersion characteristics and dynamical behavior of this circulation model are presented here in detail. Insertion of the kinematically synthesized features into a numerical dynamical model dynamically adjust the features and provide the basis for a multiparameter sensitivity study with respect to the reasonable range of parameter variation consistent with observations. Two primary characteristics of the Gulf Stream meandering behavior, namely, the wave-growth characteristics and the ring formation and absorption statistics are studied via both quasigeostrophic and primitive equation dynamics. In achieving realistic dispersion characteristics, a comprehensive methodology for dynamical model tuning and validation in this limited region ocean is developed. The realistic regimes of parameter variation are identified on the basis of observational growth rate and phase speed of the Gulf Stream meanders. Long-term simulations within these realistic regimes provide statistics of ring production and interaction behavior. The observed range of transport variability of the Gulf Stream system further constrains the parameter selection. Final tuning of parameters is obtained through an extensive study of the response from the dynamical models to the changes of parameters of the circulation model. Usefulness of the circulation model for initializing, forecasting, and updating in real synoptic cases will be the focus of Part III of this series of studies.