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Internal tide variability off Central California: multiple sources, seasonality, and eddying background
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  • Tongxin Cai,
  • Zhongxiang Zhao,
  • Eric A D'Asaro,
  • Jinbo Wang,
  • Lee-Lueng Fu
Tongxin Cai
University of Washington

Corresponding Author:[email protected]

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Zhongxiang Zhao
University of Washington
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Eric A D'Asaro
University of Washington
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Jinbo Wang
Scripps Institution of Oceanography
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Lee-Lueng Fu
Jet Propulsion Laboratory
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Two moorings deployed for 75 days in 2019 and long-term satellite altimetry data reveal a spatially complex and temporally variable internal tidal field at the SWOT Cal/Val site off central California due to the interference of multiple seasonally-variable sources. Coherent tides account for $\sim$45\% of the potential energy. The south mooring exhibits more energetic semidiurnal tides, while the north mooring displays stronger mode-1 M$_2$ with an amplitude of $\sim$5.1 mm. These findings from in situ observations align with the analysis of 27-year altimetry data. The altimetry results indicate that the complex internal tidal field is attributed to multiple sources. Mode-1 tides primarily originate from the Mendocino Ridge and the 36.5\textendash37.5$^\circ$N California continental slope, while mode-2 tides are generated by local seamounts and Monterey Bay. The generation and propagation of these tides are influenced by mesoscale eddies and seasonal stratification. Seasonality is evident for mode-1 waves from three directions. Southward components from the Mendocino Ridge consistently play a dominant role ($\sim$268 MW) yearlong. We observed the strongest eastward waves during the fall and spring seasons, generated remotely from the Hawaiian Ridge. Westward waves from the 36.5\textendash37.5$^\circ$N California continental slope are weakest during summer, while those from the Southern California Bight are weakest during spring. The highest variability of energy flux is found in the westward waves ($\pm 22\%$), while the lowest is in the southward waves ($\pm 13\%$). These findings emphasize the importance of incorporating the seasonality and spatial variability of internal tides for the SWOT internal tidal correction.
21 Feb 2024Submitted to ESS Open Archive
26 Feb 2024Published in ESS Open Archive