Warm water pathways, transports, and transformations in the northwestern North Atlantic and their modification by cold air outbreaks

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Abstract

[1] This paper presents a numerical study of the warm water pathways, transports, and water mass transformation in the Newfoundland Basin region and an investigation of the rectification effects of a series of cold air outbreaks (CAOs) on the above processes. An initial “mean state” simulation was compared with observations and showed good agreement. Then, repeated CAO events were explicitly included in the surface fluxes and illustrated the following rectification effects. The thermal regime of the entire baroclinic layer was impacted, as the thermocline deepened and the temperature anomaly was noticeable down to ∼500 m. Different mechanisms were responsible for the propagation of the temperature anomaly at different stages. During the onset of the CAO, vertical diffusion propagated the temperature anomaly downward near the surface, then vertical advection further propagated the anomaly downward between CAO events to about 500 m depth. With CAOs, the North Atlantic Current carried more warm water, and its pathway in the Northwest Corner shifted towards the southeast. The volume-averaged mean and eddy kinetic energy increased by 30% and 20%, respectively, and the water mass transformation rate in the Newfoundland basin was doubled. The Gulf Stream carried more heat, but heat transport to the eastern basin decreased owing to the increase in heat release to the atmosphere.

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