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. Key Points Deformation information over 81% of Iceland is derived from InSAR time‐series analysis Plate spreading dominates long‐wavelength east‐west displacements; GIA dominates long‐wavelength vertical displacements Models and residuals suggest spatially variable rheology beneath Iceland