Countrywide Observations of Plate Spreading and Glacial Isostatic Adjustment in Iceland Inferred by Sentinel-1 Radar Interferometry, 2015–2018

East-west and vertical ground velocities for 2015–2018 are retrieved over 81% of Iceland from Sentinel-1 radar interferometry, using satellite images from six different tracks. Only summertime images are considered, to avoid snow cover. Average line-of-sight velocity fields for 2015–2018 for each track are estimated using a simple approach: single master interferometry time series together with a linear component estimation for each pixel. The line-of-sight velocity fields are combined and their signal is decomposed to extract approximate east (near-East) and approximate vertical (near-Up) velocities. Only pixels passing a coherence and outlier criteria are considered, resulting in 81% coverage of Iceland. The 19% of missing coverage is mostly glaciers and farmland. We find a general agreement between the near-East velocity field and a revised plate spreading model, and the near-Up velocity field and a glacial isostatic adjustment model. Models and their residuals suggest a difference in rheology between the rift zones in Iceland.