Evaluating ocean tide models using absolute gravity measurements at Aboa, Dronning Maud Land, Antarctica

We have conducted absolute gravity (AG) measurements over several austral summer seasons at the Finnish Antarctic base Aboa, located in western Dronning Maud Land. The most recent measurements were made in January–February 2024. Aboa is situated on the slope of Basen nunatak, approximately 470 m above sea level, 20 km from the grounding line of the ice shelf, and 100 km from the open sea. Individual AG measurement campaigns lasted from 24 hours to two weeks, with optimal conditions for measurements - stable, laboratory-level environment and low microseismic noise.

The AG measurements revealed clear signals of ocean tidal loading, with effects reaching several microgals. To identify the most accurate representation of ocean tidal dynamics at the site, we calculated theoretical tidal loading using multiple ocean tide models, including both global and regional solutions. Due to the limited duration of the measurement campaigns, our analysis is restricted to diurnal and semidiurnal tidal components. By comparing the calculated tidal loading with the AG residuals, we aim to assess the performance of different models and refine our understanding of tidal dynamics at Aboa. Preliminary results highlight significant discrepancies between models and observations.

Tidal modeling in Antarctic regions presents unique challenges, including limited observations, uncertain sub-ice topography, and complex grounding line dynamics. Transitional zones, where the ice shelf's stiffness dampens the effects of water column changes, as well as density differences at the ice shelf base and surface, further complicate accurate tidal loading modeling.

Identifying the most accurate tidal model is important for improving the interpretation of gravity and other geodetic data, like GNSS time series, and isolating other geophysical signals, such as ice mass changes and related solid Earth deformations.