Ocean tidal loading anomaly revealed by lake-level observations in Tierra del Fuego

A. RICHTER; J. L. HORMAECHEA; R. DIETRICH; R. PERDOMO; M. FRITSCHE; D. DEL COGLIANO; G. LIEBSCH; L. MENDOZA

Buenos Aires

Congreso; Reunión Científica de la International Association of Geodesy, Geodesy for Planet Earth; 2009

Asociación Argentina de Geofísicos y Geodestas, Comité Nacional de la Unión Geodésica y Geofísica Internacional

We demostrate the application of a 100 km long lake as a sensor for studyng tidal effects on Tierra del Fuego main island, southermost South America. Pressure tide gauges were operated at three locations in Lago Fagnano for one year. from these measurement data lake.lavel records were derived with accuracy of 3 mm for single reading. A harmonic analysis of these time series yielded the aplitudes and phase angles for the main tidal constitutents M2, S2 O1, and K1. The lake tides reflect both the direct responcse to the tidal potential and the indirect effect of the ocean tidal loading. The theoretical lake-tide signal comprising both contributions was modeled numerically. For the modelling of the indirect effect the global ocean tide model FES2004 was used as load model and Green´s functions representing the Gutenberg-Bullen A lithosphere as elastic earth model. The modelled lake tides explain the observed tidal signal in the lake to about 70%. Underestimated model load tide amplitudes are found to be probably responsible for the remaining difference. We interpret this discrepancy as a hint for regional elastic lothosphere properties differing substantially from those represented by currently available global models. The presence of the Magallanes-Fagnano fault system representing the active boundary between the South American and Scotia tectonic plates as well as the substantial sediment cover throughout the region under investigation provide the geophysical/geological background for this conclusion.