Description: The dataset contains model output presented in the manuscript 'A long-term dataset of climatic mass balance, snow conditions and runoff in Svalbard (1957-2018)', which is considered for publication in The Cryosphere. The data are structured in 3-D arrays containing spatially distributed and annual mean values of the variables specified below. The spatial resolution is 1x1-km. Variables included in the dataset: ----------------------------- - Climatic mass balance - Air temperature - Precipitation - Runoff - Refreezing - Pore space (down to 14 m) - Subsurface temperature (at 14 m depth) - Snow disappearance date - Snow onset date

Description: Compared to other Arctic ice masses, Svalbard glaciers are low-elevated with flat interior accumulation areas, resulting in a marked peak in their current hypsometry (area-elevation distribution) at ~450 m above sea level. Since summer melt consistently exceeds winter snowfall, these low-lying glaciers can only survive by refreezing a considerable fraction of surface melt and rain in the porous firn layer covering their accumulation zones. We use a high-resolution climate model to show that modest atmospheric warming in the mid-1980s forced the firn zone to retreat upward by ~100 m to coincide with the hypsometry peak. This led to a rapid areal reduction of firn cover available for refreezing, and strongly increased runoff from dark, bare ice areas, amplifying mass loss from all elevations. As the firn line fluctuates around the hypsometry peak in the current climate, Svalbard glaciers will continue to lose mass and show high sensitivity to temperature perturbations. The data set includes annual cumulative SMB and components statistically downscaled from the output of the Regional Atmospheric Climate Model RACMO2.3 to 500 m spatial resolution (1958-2018). SMB components include total precipitation (snowfall and rainfall), snowfall, runoff, melt, refreezing and retention (mm w.e. per year), as well as summer (June-July-August) 2 m air temperature (K). The data set also includes modelled (RACMO2.3; 1958-2018) and observed (MODIS; 2000-2018) bare ice area, and modelled ablation zone area (1958-2018; km2). The mask file includes longitude/latitude (ºN/ºW), land-sea, ice and sector masks from the Randolph Glacier Inventory version 6, and surface topography (m above sea level) from the S0 Terreng Digital Elevation Model (Norwegian Polar Institute) on the 500 m grid. Daily downscaled SMB and components are available from the authors upon request and without conditions (b.p.y.noel@uu.nl).