Abstract
Glacier melt is an important fresh water source. Seasonal changes can have impacting consequences on downstream water resources management. Today’s glacier monitoring lacks an observation-based tool for regional, sub-seasonal observation of glacier surface mass balance and a quantification of the associated meltwater release at high temporal resolution. The snowline on a glacier marks the transition between the ice and snow surface, and is, at the end of the summer, a proxy for the annual glacier mass balance. Using transient snowlines for model calibration to derive annual mass balance time series for glaciers on regional scale has shown great potential to better grasp the glacier response to climate change for remote regions. Thereby, it was shown that model simulations closely tied to sub-seasonal snowline observations by optical satellite sensors are robust for the observation date, but glacier-specific snowline observation remained spare. We developed an approach that can automatically handle classification of multi-source and multiresolution satellite image stacks. This provides a unique solution for continuous snowline mapping since the beginning of the century when sensor availability and quality was still limited. With the provided closeto-daily transient snowlines, we provide the basis for a new strategy to directly integrate multi-source satellite image classification into glacier mass balance modelling. To estimate glacier mass balance and meltwater input to the total river runoff, AMUNDSEN (Alpine Multiscale Numerical Distributed Simulation Engine), a physically-based process model designed to quantify the energy and mass balance of ice and snow is used. Thereby, we develop a novel calibration strategy for AMUNDSEN, using the sub-seasonal snowline maps for annual model calibration. This setup is tested and validated with sub-seasonal mass balance measurements at Vernagtferner, Austria. We aim for a highly resolved, observation-based glacier monitoring and the detection of sub-seasonal changes of glacier meltwater contribution into the river system for the past two decades. The developed approach is applicable for remote and inaccessible glaciers and will help to better understand the impact of climate change on regional water availability for remote and so far, unmeasured regions.