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Ocean Surface Topography from Space
Studies of Ocean Surface Tides and Internal Tides with Satellite Altimetry


Richard Ray - (Goddard Space Flight Center)

  Gary Egbert
Edward Zaron
(Oregon State University, College of Oceanic and Atmospheric Sciences, Oregon State University)
(Portland State University, Civil and Environmental Engineering)


This proposal is for continuation of our current OSTST investigation, studying ocean surface tides and internal tides with satellite altimeter data, other types of data, and numerical modeling and assimilation. Special emphasis will be given to the study of open-ocean internal tides, their variability and energetics, and the potential implications of this to the upcoming SWOT wide-swath altimeter mission. We propose to use both multi-satellite empirical tidal analyses and data asimilation to map the phase-locked internal tide, which should supply improved tidal corrections for all altimetry but will be especially critical for SWOT. The subject of internal tides is, of course, of greater import than simply providing better corrections to altimetry. Owing in part to our previous investigations, internal tides are thought to play an important role in deep-ocean diapycnal mixing. A precise account of the internal-tide energy fluxes, however, is far from clear. Studies of internal-tide generation, propagation, dissipation, and variability should shed much light on the question, and altimetry provides an invaluable dataset for obtaining global and quantitative constraints.

Using tools developed during the current investigation, we propose to further clarify the incoherent part of low-mode internal tides as detected by altimetry. This work especially exploits the long two-decade time series of high-quality T/P-Jason measurements. As part of this work we will study the physical mechanisms at play by comparing along-track altimetry with output from a high-resolution tide-resolving operational ocean model which includes the full spectrum of physical processes that generate temporal variability in tides. This work too is of critical importance to SWOT, because it reveals the extent to which altimetry can be corrected for internal tides or must be left uncorrected (but allowed for).

We will also continue to study the surface tide and its energetics and to improve our recent tidal atlases for shelf and near-coastal waters. Our recent work has highlighted the advantages of data assimilation into high-resolution regional and local tidal models that are nested within our global models. Further incorporation of additional interleaved Jason-1 data, improved Envisat data, and potentially Cryosat-2 data, should help considerably in pushing toward higher spatial resolutions, needed for both internal tides and shallow-water tides.

Finally, we propose to contribute to the OSTST's calibration and validation activities for Jason-3 in several ways, including follow-on to previous studies of Topex and Jason significant wave height measurements, and further investigation of the notorious 59-day oscillation in altimetric mean sea level.

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