Comment on essd-2021-46

Abstract

Solgaard and Kusk, 2021)) which is a September 2016 through present time series of Greenland Ice Sheet ice velocity mosaics. The product is based on Sentinel-1 synthetic aperture radar data and has a 500 m spatial resolution. A new mosaic is available every 12 days and span two consecutive Sentinel-1 cycles (24 days). The product is made available within ∼10 days of the last acquisition and includes all possible 6 and 12 day pairs within the two Sentinel-1A cycles. We describe our operational processing chain in high detail from data selection, mosaicking and error estimation to final outlier removal. The product is validated against in-situ GPS measurements.We find that the standard deviation of the difference between satellite and GPS derived velocities is 20 m/yr and 27 m/yr for the v x and v y components, respectively. This is within the expected bounds, however, we expect that the GPS measurements carry a considerable part of this uncertainty. We investigate variations in coverage from both a temporal and spatial perspective. Best spatial coverage is achieved in winter due to excellent data coverage and high coherence, while summer mosaics have the lowest coverage due to widespread melt. The southeast Greenland Ice Sheet margin, along with other areas of high accumulation and melt, often have gaps in the ice velocity mosaics. The spatial comprehensiveness and temporal consistency make the product ideal for monitoring and studying ice-sheet wide ice discharge and dynamics of glaciers. IntroductionThe Greenland Ice Sheet (GrIS) is a major contributor to sea-level rise, and approximately half of this contribution is due to ice dynamics (Shepherd et al., 2019; Mankoff et al., 2020). Thus, in order to constrain the on-going mass loss of the Greenland Ice Sheet it is important to obtain observations of ice-flow velocities. High temporal and spatial resolution will further allow us to distinguish between annual or sub-annual variations and long-term trends, aiding in improving our understanding of the processes behind the observed changes. This is especially important because the flow of glaciers and ice caps vary on a range of timescales in response to the seasonal cycles, climate change, or internal variability (e.g. Moon et al., 2020; Joughin et al., 2018;Mouginot et al., 2018). In-situ measurements of ice-flow velocities are relatively sparse on the GrIS and most of the measurements stem from GPS surveys (Ahlstrøm et al., 2013). The sparseness is due to the inaccessibility of the GrIS and the harsh climatic conditions, which make fieldwork and instrumentation challenging. Satellite observations are thus key for 1