Greenland Ice Sheet Historical Maximum (GRISHM): A Continuous LIA Ice Margin Dataset for the Greenland Ice Sheet

The Greenland Ice Sheet (GrIS) has retreated since its historical maximum position during the Little Ice Age (LIA, ~1300–1850 CE), but the spatial pattern and rate of that recession between the LIA and the satellite era have remained poorly constrained. This dataset provides the first continuous, Greenland-wide reconstruction of the maximum observable LIA ice extent of the GrIS, referred to here as the Greenland Ice Sheet Historical Maximum (GRISHM). GRISHM was reconstructed by manually digitizing trimlines and maximum glacier terminus positions across all seven major drainage basins of Greenland, integrating multispectral imagery, ice sheet boundaries, terminus positions, and historical maps and photographs. The mapped maximum positions are largely attributed to the LIA (~1850–1900 CE), though the reconstruction is asynchronous across the ice sheet. The deposit contains three datasets, all in EPSG:32624 (WGS 84 / UTM Zone 24N): GRISHM (two versions): (a) a continuous ice surface polygon without nunataks, suited for glaciological modeling and ice volume calculations; and (b) the same margin with more than 4,000 nunatak polygons removed, suited for geomorphological analyses and area change calculations. LIA Nunataks: ice-free nunatak polygons within the LIA ice margin, filtered to ≥0.4 km², with areas computed from geometry. LIA Source Index Map: A line dataset labeling every segment of the LIA margin with the reference dataset used to define it. Note: If you use this dataset, please also cite the accompanying preprint: Salmani, M. et al. Nearly half of Greenland’s post-Little Ice Age area loss occurred since 2000. Preprint at https://doi.org/10.21203/rs.3.rs-9125064/v1 (2026).