Tidal gravimetry in polar regions: An observation tool complementary to continuous GPS for the validation of ocean tide models

SCHEINERT, M; ZAKRAJSEK, A; MARENSSI, S; DIETRICH, R; ERBELEIN, L

Geodetic and geophysical observations in polar regions - Overview in IPY perspective

Springer-Verlag

Año: 2008; p. 267 - 280

Ocean tides are an important phenomenon thathas to be considered in a variety of geoscientic investigationsin polar regions. Using ocean tide models, appropriatecorrections can be calculated and applied in the differentanalyses, e.g. to infer temporal mass variations from satellitedata, to investigate ice-shelf dynamics and deformation, tocome up with precise station positions and velocities withina terrestrial reference system. However, those models showlarger uncertainties in the polar seas and at areas covered byice shelves and, therefore, need to be improved. Within thiscontext, tidal gravimetry provides a powerful tool to validateocean tide models. Sensing the cumulative signal of differenteffects (solid earth tides, ocean tidal loading, atmosphericloading) tidal gravimetry can be regarded as an independentobservation technique and thus complements continuousGPS measurements. This paper reviews the backgroundand the work done so far by the authors in Greenland andin Antarctica. Within a current project tidal gravimetry isapplied at the Argentine Antarctic stations Belgrano II andSan MartÌn. This joint Argentine-German project is a contributionto the IPY project POLENET. The set-up of theinstruments in Belgrano II as well as rst results of the ongoingobservations, started February 2007, are presented. Wediscuss the problem of observing ocean tides in the area ofthe glacier near Belgrano II, which is ñ at least in parts ñfreely oating.1 IntroductionOne of the major goals of the International Polar Year 2007/2008 (IPY), which has been started 01 March 2007, is tocollect "`a broad range of measurements that provide a snapshotin time of the state of the polar regions"´ and "`to improveour understanding of global processes in these importantareas"´1.With regard to geodesy and geophysics the IPYproject 185 "`Polar Earth Observing Network"´ (POLENET)pursues exactly this goal with aiming on deploying autonomousobservatories at remote polar sites including GPS,seismics, gravity and tide gauges. Closing observational gapsin polar regions POLENET will substantially help to investigatepolar geodynamics and to gain deeper insight into theinteractions between cryosphere, solid earth, oceans and atmosphere.Within this framework, tidal gravimetry is onetechnique contributing to the goals of POLENET. Tidal gravimetrythrough its observations provides a connection betweenthe aforementioned spheres. Sensing the tides of thesolid earth as the main contribution, gravimetric time seriesobservations are sensitive to ocean loading, to ice masschanges and the viscoelastic reaction of the earth linked tothese as well as to atmospheric mass changes and loading.In the following, we will exemplarily review the results ofgravimetric time series observations carried out by the TU