Internal Tide Surface Signature and Incoherence in the North Atlantic.

Despite intensified efforts to better quantify Internal Tide dynamics over past decades, large uncertainties remain regarding their distribution and lifecycle in the ocean. In particular, internal tide incoherence (loss of time‐regularity) has limited our ability to characterize, understand, and predict internal tides, challenging the exploitation of new‐generation wide‐swath satellite altimeters. Based on a realistic high‐resolution numerical simulation, we quantify the internal tide distribution and incoherence properties in the North Atlantic. We quantify IT incoherence for sea level and surface currents, and for different vertical modes independently. Our results show that typical decorrelation timescale induced by the mesoscale turbulence are rather short—below 25 days for the first vertical mode. It further exhibits a strong dependence of the internal tide incoherence with location, reflecting regions of enhanced eddy activity, and with vertical mode number—higher baroclinic modes being much more incoherent with shorter decorrelation timescale. Plain Language Summary: Internal tides are perturbations of currents and density that propagate in the ocean (i.e., internal waves) and are generated when the astronomical tide flows over underwater topographic features. Because of interactions with other types of currents in the ocean, the corresponding signal is not perfectly regular in time, which has limited our understanding and ability to predict these motions for decades. In this study, we quantify this loss‐of‐regularity of the internal tides based on a numerical simulation of the North Atlantic. Key Points: Surface signatures of semidiurnal coherent and incoherent internal tides are quantified and decomposed into vertical mode contributionsIntra‐annual decorrelation time scale is typically less than 20 days for the first baroclinic mode, and less than 10 days for higher modesMean levels of incoherence of sea level and current are 55% and 68% (variance fraction), reflecting a larger high mode content in currents [ABSTRACT FROM AUTHOR]