Ascertain occurrence of extreme melt events during Sentinel-1 SAR coverage gaps over Helheim Glacier

Ascertain whether extreme melt events over the Helheim Glacier study area occurred on dates when Sentinel-1A/B synthetic aperture radar observations did not cover portions of the region due to satellite swath patterns, or whether no melting occurred on those dates (specifically 07/31/2019, 07/28/2021, 08/14/2021, and 07/18/2022).

Background

The study constructs daily 100 m resolution maps of surface meltwater by downscaling regional climate model outputs using Sentinel-1 SAR, passive microwave observations, and a digital elevation model over Helheim Glacier for 2017–2023. Due to Sentinel-1’s 1–12 day revisit and swath geometry, SAR observations only partially cover the study area on any given day, leading to substantial spatial gaps in the meltwater targets.

These swath-induced gaps cause fluctuations in the observed meltwater fraction time series, making it difficult to determine whether some apparent spikes or absences correspond to actual extreme melt events or are artifacts of missing coverage. The authors highlight specific dates where the presence or absence of extreme melt remains ambiguous due to these observation gaps.