Historical glacier change on Svalbard predicts doubling of mass loss by 2100

Abstract

In this Supplementary Information document, we:1. Illustrate our firn densification correction for converting volume change to mass change.2. Describe our treatment of grounded subaqueous ice.3. Present the datasets we use to estimate temperature and precipitation on Svalbard (1936Svalbard ( -2010.4. Show the relationships between ∆h/∆t and climate parameters such as mean annual temperature, positive degree days, and total precipitation.5. Compare our results to literature estimates of historical and future glacier change on Svalbard.Note that our 1936/1938 models, including 5 meter resolution orthophotomosaics and digital elevation models (DEMs), and a vector shapefile containing outlines and attributes of the 1,888 glaciers on Svalbard, is available on the Norwegian Polar Institute (NPI) website (https: // publicdatasets. data. npolar. no/ ) and on Zenodo (https: // doi. org/ 10. 5281/ zenodo. 5644415 ). The DEMs and orthophotomosaics are divided into the 8 regions in Main text, Fig. 1d, and represent the unprocessed SfM output-i.e., before the co-registration procedure of Nuth & Kääb ( 2011) is applied to each glacier basin individually. We also provide the raw 3D point clouds as .laz files and an .xlsx file with the glacier-by-glacier statistics of area, volume, ∆h/∆t, ∆M/∆t, mean summer temperature, total solid precipitation, etc.

Halving of Swiss glacier volume since 1931 observed from terrestrial image photogrammetry

“…This indicates that glaciers with flatter termini or higher debris cover tend to experience higher mass loss rates as their steeper and ice-free counterparts. These findings support the results from studies performed with smaller subsets of glaciers (Huss, 2012), over shorter time spans (Fischer et al, 2015), in different geographical regions (Brun et al, 2019;Geyman et al, 2022), and based on area-change data (Linsbauer et al, 2021).…”

“…Comparisons between glacier extents obtained from digitized maps and modern digital photogrammetric reconstructions show significantly reduced biases for the latter (e.g. Koblet et al, 2010;Midgley and Tonkin, 2017;Geyman et al, 2022). In addition, many maps are temporally inconsistent, because maps are asynchronously updated with newer data that are added to older maps during successive revisions.…”

“…Large-scale changes throughout the 1900s are however still largely unknown. Recently, photogrammetric studies reconstructing glacier surface geometries for the late 19 th and early 20 th centuries have emerged (Mertes et al, 2017;Midgley and Tonkin, 2017;Girod et al, 2018;Dehecq et al, 2020;Holmlund, 2021), partially revealing large discrepancies when compared to model-based estimates (Holmlund and Holmlund, 2019;Belart et al, 2020;Geyman et al, 2022). For a better understanding of the response of glaciers to a changing climate, more historic data to understand these discrepancies are essential.…”

“…This is one of the rare regional reconstructions based on digital photogrammetry before the 1950s (e.g. Belart et al, 2020;Geyman et al, 2022), and to the knowledge of the authors, the first of such scope to use terrestrial photographs as the source material.…”

Reply on RC1

“…The latter underlines the relevance of closely monitoring these environments with simple and accessible tools. Even more so when considering that Svalbard experienced an average air temperature warming rate that was seven times greater than the global average since 1991 (Nordli et al, 2020) and that Svalbard glaciers continue to retreat significantly (Geyman et al, 2022) also when compared to other tidewater glaciers in the Northern hemisphere (Kochtitzky and Copland, 2022).…”