Mapping vanishing glaciers in Vorarlberg, Austria

Abstract We assess ongoing regional glacier loss in the Austrian state of Vorarlberg using a set of manually mapped glacier outlines for 2017, 2020, 2022 and 2023. Vorarlberg has lost about half of its glacierized area since a previous inventory in the mid-2000s. In 2017–23, glacier area was lost at an average rate of 5% per year. Area loss rates at individual glaciers have increased over time but show considerable variability between glaciers and subperiods. Of 30 glaciers previously inventoried, 5 have vanished completely since 2017. We discuss mapping differences due to the variable interpretation of the images by multiple observers and the mapping challenges that arise even with very high-resolution (10 cm) imagery. Processes leading up to the complete loss of glacier ice, mainly increased debris cover and fragmentation into very small features, cause inherent uncertainties in documenting the disappearance of mountain glaciers and ice bodies. We considered criteria that might be used to define terminology and found 16 remaining glacier fragments with crevasses indicating past or current ice flow, which could be considered glaciers rather than ice bodies.