Large-scale ground deformation in Iceland is dominated by extensional plate-boundary deformation, where the Mid-Atlantic Ridge crosses the island, and by uplift due to glacial isostatic adjustment from thinning and retreat of glaciers. While this deformation is mostly steady over multiple years, it is modulated by smaller-scale transient deformation associated with e.g., earthquakes, volcanic unrest, and geothermal exploitation. Here we combine countrywide Sentinel-1 interferometric synthetic aperture radar (InSAR) data (from six tracks) from 2015 to 2021 with continuous GNSS observations to produce time-series of displacements across Iceland. The InSAR results were improved in a two-step tropospheric mitigation procedure, using (1) global atmospheric models to reduce long-wavelength and topography-correlated tropospheric signals, and (2) modeling of the stochastic properties of the residual troposphere. Our results significantly improve upon earlier country-wide InSAR results, which were based on InSAR stacking, as we use more data, better data weighting, and advanced InSAR corrections to produce time-series of ground displacements instead of just velocities. We fuse the three ascending and three descending track results to estimate maps of East and Up velocities, which clearly show the large-scale extension and GIA deformation. Using a revised plate-spreading and glacial isostatic adjustment models, based on these new ground velocity maps, we remove the large-scale and steady deformation from the InSAR time-series and analyze the remaining transient deformations. Our results demonstrate the importance of (1) mitigating InSAR tropospheric signals over Iceland and of (2) solving for time-series of deformation, not just velocities, as multiple transient deformation processes are present.
Bibliographical noteKAUST Repository Item: Exported on 2023-02-27
Acknowledged KAUST grant number(s): BAS/1/1353-01-01
Acknowledgements: We thank the editor and the anonymous reviewers for their many insightful comments and suggestions. We thank Dr He Tang and Dr Charles Williams for the discussions on GIA modeling. This research was supported by King Abdullah University of Science and Technology (KAUST), under award number BAS/1/1353-01-01, and public research funding from the Government of New Zealand. The Sentinel-1 images are from the European Space Agency (ESA) and were downloaded from the Alaska Satellite Facility (ASF)(https://asf.alaska.edu/data-sets/sar-data-sets/sentinel-1/), and the ERA5 data used by ICAMS are provided by ECMWF(The European Centre for Medium-Range Weather Forecasts)(https://www.ecmwf.int/en/forecasts/datasets/reanalysis-datasets/era5). The earthquake data (locationsand magnitudes) are from the Icelandic Meteorological Office (IMO) (https://hraun.vedur.is/). The operation of the GNSS stations used in this study is led by IMO with several of their international partners