Abstract
ABSTRACTGlobal-scale 21st-century glacier mass change projections from six published global glacier models are systematically compared as part of the Glacier Model Intercomparison Project. In total 214 projections of annual glacier mass and area forced by 25 General Circulation Models (GCMs) and four Representative Concentration Pathways (RCP) emission scenarios and aggregated into 19 glacier regions are considered. Global mass loss of all glaciers (outside the Antarctic and Greenland ice sheets) by 2100 relative to 2015 averaged over all model runs varies from 18 ± 7% (RCP2.6) to 36 ± 11% (RCP8.5) corresponding to 94 ± 25 and 200 ± 44 mm sea-level equivalent (SLE), respectively. Regional relative mass changes by 2100 correlate linearly with relative area changes. For RCP8.5 three models project global rates of mass loss (multi-GCM means) of >3 mm SLE per year towards the end of the century. Projections vary considerably between regions, and also among the glacier models. Global glacier mass changes per degree global air temperature rise tend to increase with more pronounced warming indicating that mass-balance sensitivities to temperature change are not constant. Differences in glacier mass projections among the models are attributed to differences in model physics, calibration and downscaling procedures, initial ice volumes and varying ensembles of forcing GCMs.
Highlights
Retreating mountain glaciers around the world have become icons of anthropogenic climate change
Despite making up
This study presents the first activity within GlacierMIP, which aims to systematically compare recently published global-scale glacier model results in order to foster model improvements and reduce uncertainties in global glacier projections
Summary
Retreating mountain glaciers around the world have become icons of anthropogenic climate change. Gardner and others (2013) combined direct glaciological data with mass change estimates derived from geodetic and gravimetric data and estimated a sea-level contribution from glaciers of 259 ± 28 Gt a−1 (0.71 ± 0.08 mm SLE a−1 or ∼30% of observed sea-level rise) between October 2003 and October 2009. This estimate is similar to the one for both ice sheets combined (289 ± 49 Gt a−1, 0.80 ± 0.14 mm SLE a−1) for roughly the same period (2000–2011; Shepherd and others, 2012). Glaciers are expected to remain an important contributor to sea-level rise during the 21st century (Meier and others, 2007; Church and others, 2013), and any Downloaded from https://www.cambridge.org/core. 02 Nov 2021 at 14:47:39, subject to the Cambridge Core terms of use
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