Svalbard glacier calving front changes from the 1930s to the 1970s from archived satellite and aerial images

Abstract. We obtained calving front positions of 171 Svalbard tidewater glaciers from archived satellite imagery. We used early Landsat images from 1976–1978 as well as declassified intelligence satellite photographs from 1962–1963. To support the analysis of these calving fronts, we also used historical aerial images from 1936–1938. During our study period between 1936–1978, we estimate an average glacier retreat rate of 27.3±3.0myr-1. This corresponds to an average retreat of approximately 1 km for Svalbard tidewater glaciers during this period. By multiplying the retreats by the glaciers' widths, we estimate the cumulative area loss rate to be 17.0±2.5km2yr-1, which is slightly lower than the estimates found in the existing literature for the periods 1985–2023 and 2000–2020, and consistent with climatic trends from reanalysis data. Looking at individual glaciers, we identify and discuss 15 significant advance events. For four of them, our study provides additional information to current knowledge. We have discovered one undocumented surge – we show evidence that Emmabreen has surged between 1936–1963. We have also narrowed down the time windows of two previously known surges: the surge of Allfarvegen to between 1976–1978 (previously reported to have happened between 1970–1980), and the surge of Stonebreen to between 1936–1963 (previously reported between 1936–1971). We also show that Schweigaardbreen and Fonndalsbreen have advanced 400 and 541 m, respectively, between 1938–1976. We discuss the potential future uses of our dataset, consisting of georeferenced satellite images used in our study as well as digitized calving fronts, which is freely available for future research.