Geography and Dynamics of Small-scale Coastal and Internal Tides from Exact Repeat and Geodetic Mission Altimetry
Geography and Dynamics of Small-scale Coastal and Internal Tides from Exact Repeat and Geodetic Mission Altimetry
Abstract:
New empirical maps of tides with 3-minute spatial resolution have been prepared in order to study the
dynamics of small-scale coastal and internal tides, and to assess the potential for developing tidal
corrections that include these features. Two approaches have been used, (1) one which involves mapping
harmonic constants from exact-repeat altimeter missions (Topex/Poseidon, Jason-1, Jason-2, Envisat, ERS,
and Geosat Follow-On) using a simple weighted-averaging scheme, and (2) one which combines both exact
repeat and geodetic mission data (Geosat, ERS, and Jason-1) using spatially-coupled harmonic
analysis. High-resolution maps of the main semi-diurnal (M2) and diurnal (K1) tides constructed using these
approaches are analyzed and it is found that the wavelength of the internal tide in the deep ocean agrees
closely with the theoretically-predicted wavelength. The K1 map shows clearly the influence of the critical
latitudes beyond which K1 is non-propagating. Independent Cryosat-2 data are used to validate the tide
models by looking at maps of explained variance. Both approaches to mapping the internal tide result in
variance reductions; however, away from the coastline, the tide estimates constructed from exact-repeat
mission data alone are slightly more accurate than the maps which also incorporate geodetic mission data.
In spite of the reduced accuracy in the open ocean, the latter maps extend all the way to the coastline
and explain a significant amount of variance within 200km of the coastline.
dynamics of small-scale coastal and internal tides, and to assess the potential for developing tidal
corrections that include these features. Two approaches have been used, (1) one which involves mapping
harmonic constants from exact-repeat altimeter missions (Topex/Poseidon, Jason-1, Jason-2, Envisat, ERS,
and Geosat Follow-On) using a simple weighted-averaging scheme, and (2) one which combines both exact
repeat and geodetic mission data (Geosat, ERS, and Jason-1) using spatially-coupled harmonic
analysis. High-resolution maps of the main semi-diurnal (M2) and diurnal (K1) tides constructed using these
approaches are analyzed and it is found that the wavelength of the internal tide in the deep ocean agrees
closely with the theoretically-predicted wavelength. The K1 map shows clearly the influence of the critical
latitudes beyond which K1 is non-propagating. Independent Cryosat-2 data are used to validate the tide
models by looking at maps of explained variance. Both approaches to mapping the internal tide result in
variance reductions; however, away from the coastline, the tide estimates constructed from exact-repeat
mission data alone are slightly more accurate than the maps which also incorporate geodetic mission data.
In spite of the reduced accuracy in the open ocean, the latter maps extend all the way to the coastline
and explain a significant amount of variance within 200km of the coastline.