Abstract

D'ONOFRIO, Enrique E; OREIRO, Fernando A; GRISMEYER, Walter H  and  FIORE, Mónica M. E. Accurate astronomical tide predictions calculated from satellite altimetry and coastal observations for the area of Isla Grande de Tierra del Fuego, Isla de los Estados and Beagle channel. Geoacta [online]. 2015, vol.40, n.2, pp.60-75. ISSN 1852-7744.

The ocean tide is one of the major contributions to the variation of sea surface height, and is responsible for much of the variance in many oceanographic variables. Also, it is essential to have accurate tidal predictions for many practical applications in the marine environment, such as navigation, planning coastal construction, flood zone determination and pollutants dispersion modeling. On continental shelves, tide is mainly forced by resonance phenomena produced by the co-oscillation of the ocean tide, reaching large amplitudes, with significant energy dissipation. An example of resonance phenomena corresponds to the continental shelf where the East coast of the Isla Grande de Tierra del Fuego is located, where tidal amplitudes vary between 4 m and 10 m, and then a decrease till 2 m in the Beagle Channel. This area has always been an area of interest due to the significant hydrocarbon reserves it holds. Oil exploitation in marine environments of large tidal amplitude, requires very accurate tide predictions for both, logistical support tasks as for their own exploitation. An alternative way to calculate astronomical tide predictions is using harmonic constants provided by the results of global models as GOT4.7, TPXO7.2, TPXO8, FES2012, EOT11a and regional ones such as AO-ATLAS-2011, available on the INTERNET. Although these models substantially improved the tide knowledge at a global scale, their results, in the vicinity of the coast are less accurate than in the rest of the oceans, also having low resolution (between 3,7 km x 3,7 km and 18,5 km x 18,5 km). Then, remain insufficient to accurately predict the tide on the corresponding continental shelf of the Isla Grande de Tierra del Fuego, Isla de los Estados and Beagle Channel. The aim of this work is to obtain harmonic tidal constants for a 500 m x 500 m grid, between latitudes 52°00'00' S and 55°20'30' S and longitudes 63°30'00' W and 69°00'00' W, to be sufficient to make an accurate prediction of the astronomical tide. Corange and cotidal charts are built from these results for proper and complete characterization of the astronomical tide in the region. The sea level heights obtained in 34 tide stations and 111 satellite altimetry data positions, for an area that extends slightly beyond the study area, are used as baseline information. The results are verified by performing linear regressions between predicted tidal heights using calculated harmonic constants versus observed satellite altimetry sea level heights, corresponding to 10 different positions of the 111 used to calculate the grid, resulting slopes close to 1. In addition RMSMisfit values, between the harmonic constants obtained here and those calculated by Richter et al. (2012), were calculated in 3 locations. Values in the range 0,00 m - 0,04 m were obtained for components that were not contaminated by other nearby frequencies components. These results indicate that the harmonic constants obtained allow calculation of accurate astronomical tide predictions. Finally, using the grid of harmonic constants obtained, the surface corresponding to the astronomical tide on 08/11/2014 at 9 am (time zone +3) for the entire study area is calculated.

Keywords : Tidal harmonic constants; Cotidal chart; Corange chart; Satellite altimetry; Tierra del Fuego.

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