Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> This study proposes an approach to estimate the ocean sea surface height signature of coherent internal tides from a 25-year along-track altimetry record, with a single inversion over time, resolving both internal tide contributions and mesoscale eddy variability. The inversion is performed on a reduced-order basis of topography and practically achieved with a conjugate gradient. The particularity of this approach is to mitigate the potential aliasing effects between mesoscales and internal tide estimation from the uneven altimetry sampling (observing the sum of these components) by accounting for their statistics simultaneously, while other methods generally use a prior mesoscale. The four major tidal components are considered (M2, K1, S2, O1) over the period 1992–2017 on a global configuration. From the solution, we use altimetry data after 2017 for independent validation in order to evaluate the performance of the simultaneous inversion and compare it with an existing model.

Highlights

  • This study proposes an approach to estimate the Ocean Sea Surface Height signature of coherent internal tides from 25 years of along-track altimetry record, with a single inversion over time, resolving both internal tide contributions and mesoscale eddy variability

  • 10 Ocean internal gravity waves forced by barotropic tidal currents, known as Internal Tides, have signatures on Sea Surface Height (SSH) at scales of 150km wavelength and below (e.g. Ray and Mitchum (1997))

  • 15 modulated (Zaron (2017)) and challenging to resolve from the present along-track Altimetry record, the 30% coherent can be estimated from the series of more than 25 years

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Summary

Introduction

10 Ocean internal gravity waves forced by barotropic tidal currents, known as Internal Tides, have signatures on Sea Surface Height (SSH) at scales of 150km wavelength and below (e.g. Ray and Mitchum (1997)) Their vertical extension splits in several modes with specific propagations modulated by vertical stratification at first order. To mitigate this issue, most of approaches use separate estimates of mesoscales such as the DUACS maps distributed by AVISO and CMEMS (Taburet et al (2019)) to substract to the altimetry data used for internal tide analysis. Most of approaches use separate estimates of mesoscales such as the DUACS maps distributed by AVISO and CMEMS (Taburet et al (2019)) to substract to the altimetry data used for internal tide analysis. We will discuss the perspectives, in particular to handle non-stationary internal tides with future wide-swath Altimetry data

The simultaneous estimation : principle and illustrations
General principle
Illustrations
Application to the global Altimetry Record
The inversion in reduced space
The decomposition basis for Mesoscales
The inversion
Conclusions

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