Classifying disequilibrium of small mountain glaciers from patterns of surface elevation change distributions

Abstract

The overall trend of rapid retreat of Alpine glaciers contains considerable variability of responses at the scale of individual glaciers. As a step towards a regional assessment of glacier state that allows a detailed differentiation of single glaciers, we explore the potential of a self-organizing maps (SOM) algorithm to identify and cluster recurring patterns of thickness change at glaciers in western Austria. Using digital elevation models and glacier inventories for three time periods, we compute the frequency distribution of surface elevation change over the area of each glacier in the data set, for each period. The results of the SOM clustering show a distinct pattern shift over time: From 1969 to 1997, surface elevation change occurred at relatively uniform rates across a given glacier. Since 1997, the distribution of surface elevation change at individual glaciers has been far less uniform, indicating accelerated processes of disintegration. Tracking the evolution of individual glaciers throughout the time periods via the clusters highlights both the broader regional trend as well as glaciers that deviate from this trend, e.g. some very small, high elevation glaciers that have reverted to reduced and more uniform volume loss patterns.

Ötzi, 30 years on: A reappraisal of the depositional and post-depositional history of the find

“…Glaciological data that describe the specific setting of the findspot consist of historical maps, a glacier inventory for the late LIA, and several different sources of information for recent decades. The latter include data on glacier extent and elevation between 1969 and 2017 (Fischer et al, 2015; Hartl et al, 2022), ice thickness measurements (Fischer and Kuhn, 2013), time series of orthophotos taken at the end of summer, and mass balance data regarding the nearby glaciers Hintereisferner and Kesselwandferner (Strasser et al, 2018 and references herein). Additional data arise from dating the basal layer of the ice core drilled on the nearby summit of Weißseespitze (3500 m) complemented by the direct mass measurements starting in 2017 and historical maps of the last century.…”

“…In a first step, the changes in extent and volume were analysed from historical maps (~1870) and the glacier inventories (1969, 1997, 2006Fischer et al, 2015;Hartl et al, 2022). The topographic setting of the former glacier base was analysed from a high-resolution LiDAR digital elevation model of the now ice-free area.…”