Supplementary code for: "Historical glacier change on Svalbard predicts doubling of mass loss by 2100"

Code to perform the analysis in:

Geyman, E.C., van Pelt, W., Maloof, A.C., Faste Aas, H., and Kohler, J., 2021. "Historical glacier change on Svalbard predicts doubling of mass loss by 2100." Nature.

Abstract:

The melting of glaciers and ice caps accounts for about one third of current sea level rise, exceeding the mass loss from the more voluminous Greenland or Antarctic Ice Sheets. The Arctic archipelago of Svalbard, which hosts spatial climate gradients that are larger than the expected temporal shifts over the next century, is a natural laboratory to constrain the climate sensitivity of glaciers and predict their response to future warming. Leveraging an archive of historical aerial images from 1936 and 1938, we use structure-from-motion (SfM) photogrammetry to reconstruct the 3D geometry of 1,594 glaciers across Svalbard. We compare these reconstructions to modern ice elevation data to derive the spatial pattern of mass balance over a >70-year timespan, allowing us to see through the noise of annual and decadal variability to quantify how variables such as temperature and precipitation control ice loss. We find a robust temperature dependence of melt rates, whereby a 1°C rise in mean summer temperature corresponds to a decrease in area-normalized mass balance of -0.27 m yr^-1 of water equivalent. Finally, we design a space-for-time substitution to make first-order predictions of 21st century glacier change across Svalbard. Even in the most modest scenario (a ~1.4°C rise in mean summer temperature by 2100), we predict average glacier thinning rates in 2010-2100 of -0.67 m yr^-1, approximately twice the 1936-2010 rates.