Adrien Bella

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The interaction between the internal tide and the mesoscale circulation are studied from the internal tide energy budget perspective. To that end, the modal energy budget of the internal tide is diagnosed using a high resolution numerical simulation covering the North Atlantic. Compared to the topographic contribution, the advection of the internal tide by the background flow and the horizontal and vertical shear are found to be significant at global scale, while the buoyancy contribution is important locally. The advection of the internal tide by mesoscale currents is responsible for a net energy transfer from the large scale to smaller scale internal tide, without significant exchanges with the background flow. On the opposite, the shear of the mesoscale circulation and the buoyancy field are responsible for exchanges between the internal tide and the background flow. The importance of the shear increases in the northernmost part of the domain, and a partial compensation between the buoyancy and the shear contributions is found in some areas of the North Atlantic, such as in the Gulf Stream region. In addition, the temporal variability of the topographic, advection, mesoscale shear and buoyancy gradient induced energy transfers is investigated. The spring neap cycle is the dominant frequency for the topographic scattering, but other frequencies modulate this term in areas of strong mesoscale activity. Mesoscale induced energy fluxes are modulated by both the spring neap cycle and the variation in the mesoscale circulation patterns.