Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

Abstract

Abstract.It is standard to compare climate model results covering the past millennium and reconstructions based on various archives in order to test the ability of models to reproduce the observed climate variability. Up to now, glacier length fluctuations have not been used systematically in this framework even though they offer information on multidecadal to centennial variations complementary to other records. One reason is that glacier length depends on several complex factors and so cannot be directly linked to the simulated climate. However, climate model skill can be measured by comparing the glacier length computed by a glacier model driven by simulated temperature and precipitation to observed glacier length variations. This is done here using the version 1.0 of the Open Global Glacier Model (OGGM) forced by fields derived from a range of simulations performed with global climate models over the past millennium. The glacier model is applied to a set of Alpine glaciers for which observations cover at least the 20th century. The observed glacier length fluctuations are generally well within the range of the simulations driven by the various climate model results, showing a general consistency with this ensemble of simulations. Sensitivity experiments indicate that the results are much more sensitive to the simulated climate than to OGGM parameters. This confirms that the simulations of glacier length can be used to evaluate the climate model performance, in particular the simulated summer temperatures that largely control the glacier changes in our region of interest. Simulated glacier length is strongly influenced by the internal variability in the system, putting limitations on the model-data comparison for some variables like the trends over the 20th century in the Alps. Nevertheless, comparison of glacier length fluctuations on longer timescales, for instance between the 18th century and the late 20th century, appear less influenced by the natural variability and indicate clear differences in the behaviour of the various climate models.

The Open Global Glacier Model (OGGM) v1.1

“…The dynamical representation of glacier advance and retreat enables studies of glacier evolution at long (paleo-) timescales, where ice dynamics and geometrical attributes such as the accumulation area ratio play an important role (e.g., Mackintosh et al, 2017). The first OGGM simulations over the last millennium show very promising results (Goosse et al, 2018). The modular framework allows one to compare the performance of various pa- rameterizations such as the mass balance and downscaling algorithms.…”

Modelling the future evolution of glaciers in the European Alps under the EURO-CORDEX RCM ensemble

“…Zekollari et al, 2013), justifying an approach in which both are combined (e.g. Gudmundsson, 1999;Clarke et al, 2015).…”

19th century glacier retreat in the Alps preceded the emergence of industrial black carbon deposition on high-alpine glaciers

“…To isolate the often complex relationships between glacier fluctuations and meteorological forcing and to identify the mechanisms responsible for glacier retreat in the second half of the 19th century requires comprehensive modelling efforts (e.g. Lüthi, 2014;Zekollari, 2017;Goosse et al, 2018). Underpinning such efforts, accurate and precise delineation of external forcing (e.g.…”