On the disequilibrium response and climate change vulnerability of the mass-balance glaciers in the Alps

Glaciers in the Alps and several other regions in the world have experienced strong negative mass balances over the past few decades. Some of them are disappearing, undergoing exceptionally negative mass balances that impact the mean regional value, and require replacement. In this study, we analyse the geomorphometric characteristics of 46 mass-balance glaciers in the Alps and the long-term mass-balance time series for a subset of nine reference glaciers. We identify regime shifts in the mass-balance time series (when non-climatic controls started impacting) and develop a glacier vulnerability index (GVI) as a proxy for their possible future development, based on criteria such as hypsometric index, breaks in slope, thickness distribution and elevation change pattern. We found that the subset of 46 mass-balance glaciers reflects the characteristics of the total glacier sample very well and identified a region-specific variability of the mass balance. As the GVI is strongly related to cumulative glacier mass balances, it can be used as a pre-selector of future mass-balance glaciers. We conclude that measurements on rapidly shrinking glaciers should be continued as long as possible to identify regime shifts in hind-cast and better understand the impacts of climatic variability on such glaciers.