A new model for global glacier change and sea-level rise

Abstract

The anticipated retreat of glaciers around the globe will pose far-reaching challengeto the management of fresh water resources and significantly contribute to sea-levrise within the coming decades. Here, we present a new model for calculating twenty-first century mass changes of all glaciers on Earth outside the ice sheets. ThGlobal Glacier Evolution Model (GloGEM) includes mass loss due to frontal ablation marine-terminating glacier fronts and accounts for glacier advance/retreat and surfacelevation changes. Simulations are driven with monthly near-surface air temperaturand precipitation from 14 Global Circulation Models forced by RCP2.6, RCP4.5, anRCP8.5 emission scenarios. Depending on the scenario, the model yields a global glacievolume loss of 25-48% between 2010 and 2100. For calculating glacier contributioto sea-level rise, we account for ice located below sea-level presently displacing oceawater. This effect reduces the glacier contribution by 11-14%, so that our model predicta sea-level equivalent (multi-model mean ±1 standard deviation) of 79±24mm(RCP2.6108±28mm (RCP4.5), and 157±31mm (RCP8.5). Mass losses by frontal ablatioaccount for 10%of total ablation globally, andupto ∼30%regionally. Regional equilibriuline altitudes are projected to rise by ∼100-800m until 2100, but the effect on wastage depends on initial glacier hypsometries.