Svalbard glacier calving front retrievals during the 1960s and 1970s from archived Landsat and declassified intelligence satellite photographs

Abstract. We retrieved calving front locations 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 geophysical analysis of these calving fronts, we also used historical aerial images from 1936–1938. During our study period between 1936 and 1978, we estimate an average glacier retreat rate of 26.3 m yr^-1. This corresponds to an approximately 1 km of average retreat of Svalbard tidewater glaciers during this period. By multiplying the retreats by the glaciers' widths, we estimate the cumulative area loss rate to be 16.0 km² yr^-1 (R²=0.94), which is slightly lower than the estimates found in the existing literature for the periods 1985–2023 and 2000–2020. 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 and 1963. We have also narrowed down the time windows of two previously known surges: the surge of Allfarvegen to between 1976 and 1978 (previously reported to have happened between 1970 and 1980), and the surge of Stonebreen to between 1936 and 1963 (previously reported between 1936 and 1971). We also show that Schweigaardbreen and Fonndalsbreen have advanced 400 and 541 meters, respectively, between 1938 and 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.