Intelligent Earth system sensing, scientific enquiry and discovery


Storm surges in the German Bight: Are loading effects detectable by the SG recording at the Geodynamic Observatory Moxa in Thuringia?

Thomas Jahr (1), Adelheid Weise (1), Sylvin Müller-Navarra (2)
(1) Institute of Geosciences, Friedrich Schiller University Jena, (2) Bundesamt für Seeschifffahrt und Hydrographie (BSH), Hamburg

For 18 years the superconductive gravimeter SG CD-034 is running continuously at the Geodynamic Observatory Moxa in Thuringia, Germany. In addition to the tides of the solid Earth the considerable smaller ocean load tides are recorded which are mainly caused by the North Atlantic and the North Sea  for Central Europe. The gravity ocean loading effect of the main semi diurnal constituent M2 amounts to 14 nm/s² in Moxa, which can also be estimated in the time series. Beside these well known and clearly detectable  gravity variations there are also much smaller non-periodical changes which can be caused, for example, by aerial masses or global to local hydrologic variations.

The discussion about the detectability  of very small signals has raised the question whether it is possible to observe an individual storm flood event in the German Bight via oceanic loading effect in the SG recording in Moxa, approx. 400 km from the coast, and to separate it. The necessary reductions of the atmospheric pressure effect as well as the local hydrologic correction obtain particular importance. The atmospheric pressure/mass effect is reduced by the three-dimensional modeling of the surrounding atmosphere of ATMACS extended to higher sample rate by including local air pressure variation. In addition, a local hydrologic model has been transferred into a time dependent gravity model which enables a local hydrologic reduction. The careful correction of  this influence as well as an accompanying ocean load modeling lead to the statement that the challenge is to resolve the effect of a storm flood event by most accurate reduction of all environmental effects.  The thrilling question remains: Can we separate the storm-induced signal in  the record of the superconductive gravimeter?

Scientific Topic: 
Tides and non tidal loading (Bruno Meurers, David Crossley)
Poster location: