A nine-year record of slush on the Greenland Ice Sheet

A Nine-Year Record of Slush Extent on the Greenland Ice Sheet (2016–2024) Emily Glen, Lancaster University Dataset Description This dataset provides the first near-decadal, ice-sheet-wide record of slush extent on the Greenland Ice Sheet, covering melt seasons from 2016 to 2024. Slush is defined as partially saturated snow or firn, formed by meltwater accumulation and refreezing, with significant implications for runoff, energy balance, and supraglacial drainage evolution. Methodology Satellite source: Sentinel-2 MSI Classification: Supervised Random Forest model in Google Earth Engine Output: Monthly classifications at 10 m resolution Regional summaries produced for six basins (SW, CW, NW, NO, NE, SE) Contents Monthly slush shapefiles (2016–2024)Classified monthly slush extent (May–September) for each year. Annual compositesUnion of monthly slush extent per year (2016–2024). Format and Metadata File format: ESRI Shapefile (.shp, .shx, .dbf, .prj) Coordinate system: EPSG:3413 — WGS 84 / NSIDC Sea Ice Polar Stereographic North Usage Notes Cloud-covered regions are excluded from classification. Slush extent may be underestimated in persistently cloudy areas. Use in conjunction with climate data (e.g., RACMO) for full context. Funding This work was conducted under the 4DGreenland project, funded by the European Space Agency (ESA) and the UK Engineering and Physical Sciences Research Council (EPSRC). Dataset DOI https://doi.org/10.5281/zenodo.16338735 Figures from our Upcoming Paper Figure 1. Overview map of Greenland separated into six drainage basins: Southwest (SW), Central West (CW), Northwest (NW), North (NO), Northeast (NE), and Southeast (SE) (Mouginot and Rignot, 2019). Red boxes indicate the footprints of the 24 training/validation images used to train and validate the RF classifier.Base map source: Esri. Figure 2. Flowchart of slush classification workflow adapted from Dell et al. (2022), originally designed for Antarctic ice shelves and modified here for the Greenland Ice Sheet (GrIS). Figure 3. Slush persistence and average coverage across basins during summer (May–September). Persistence is indicated by colour (1–9 years). Circle size represents average slush coverage (2016–2024). Embedded pie charts show average monthly slush distribution. Additional overlays: Ice slab extent (2010–2018; Jullien et al., 2023) – dark green dotted outline Firn aquifer extent (2010–2014; Miège et al., 2016) – purple dotted outlineBase map source: Esri. Figure 4. Temporal variability in slush area and climate anomalies (2016–2024). Top: Total slush area by month (May–September), annually. Middle: Monthly snowmelt anomalies (mm w.e.) from RACMO (Noël et al., 2019). Bottom: Monthly near-surface air temperature anomalies (°C) from RACMO. Figure 5. Bar plots of total slush-covered area (km²) by basin and month. Each panel shows a specific basin (NW, CW, SW, SE, NE, NO). Monthly breakdown: May–September. Overlaid: Snowmelt anomalies (black lines, mm w.e.) 2 m air temperature anomalies (red lines, °C) Shaded regions = standard error.