Preprints
https://doi.org/10.5194/egusphere-2024-1857
https://doi.org/10.5194/egusphere-2024-1857
26 Jun 2024
 | 26 Jun 2024
Status: this preprint is open for discussion.

Internal tides off the Amazon shelf in the western tropical Atlantic: Analysis of SWOT Cal/Val Mission Data

Michel Tchilibou, Loren Carrere, Florent Lyard, Clément Ubelmann, Gérald Dibarboure, Edward D. Zaron, and Brian K. Arbic

Abstract. The Surface Water and Ocean Topography (SWOT) altimetry mission launched at the end of 2022 is an opportunity to access ocean variability at scales down to 15–30 km and to better understand high-frequency dynamic processes such as the internal tide (IT).  This study characterizes the internal tides off the Amazonian shelf in the tropical Atlantic; it is based on 2 km horizontally gridded observations along the swaths of SWOT track 20 during the calibration/validation phase (Cal/Val, 1-day orbit) from late March to early July 2023. Internal tide models for M2, S2 and N2 were first derived by harmonic analysis of the sea level anomaly (SLA), then improved by performing a principal component analysis (PCA) prior to harmonic analysis. The results compare very well with the high-resolution empirical tide (HRET) internal tide model, the reference product for internal tide corrections in altimetry observations. The coherent mode 1 and mode 2 can be distinguished in the internal tide model derived from SWOT, while the higher modes with their strong SLA signature seem mostly in the incoherent part. The PCA also gives an overview of the daily variability of the internal tide. 

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Michel Tchilibou, Loren Carrere, Florent Lyard, Clément Ubelmann, Gérald Dibarboure, Edward D. Zaron, and Brian K. Arbic

Status: open (until 21 Aug 2024)

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Michel Tchilibou, Loren Carrere, Florent Lyard, Clément Ubelmann, Gérald Dibarboure, Edward D. Zaron, and Brian K. Arbic
Michel Tchilibou, Loren Carrere, Florent Lyard, Clément Ubelmann, Gérald Dibarboure, Edward D. Zaron, and Brian K. Arbic

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Short summary
This study is based on sea level observations along the swaths of the new SWOT altimetry mission during its Calibration / Validation period. Internal tides are characterised off the Amazon shelf in the tropical Atlantic. SWOT observes internal tides over a wide range of spatial scales and highlights structures between 50–2 km, which are very intense and difficult to predict. Compared to the reference used to correct the altimetry data, the internal tide derived from SWOT performs very well.