Landfast ice growth and displacement in the Mackenzie Delta observed by 3D time-series SAR speckle offset tracking

Abstract. This study investigates the growth and displacement of landfast ice along the shoreline of the Mackenzie Delta by synthetic aperture radar (SAR) speckle offset tracking (SPO). Three-dimensional (3D) offsets were reconstructed from Sentinel-1 ascending and descending SAR images acquired on the same dates during the November 2017–April 2018 and October 2018–May 2019 annual cycles. The results showed horizontal and vertical displacements of floating landfast ice caused by ice breakups and pressure ridges, which are mainly driven by drift sea ice motions and Mackenzie Delta discharges. Cumulative vertical offsets of approximately −1 to −2 m were observed from freshwater landfast ice, which is due to longer radar penetration into the ice-water interface with increasing landfast ice thickness. Numerical ice thickness model estimates confirmed that the cumulative vertical downward offsets indicate the growth of freshwater landfast ice thickness. Time-series analysis showed that significant growth and displacement of floating landfast ice in the Mackenzie Delta occur between November and January.