Abstract
AbstractGlacier mass loss is recognized as a major contributor to current sea level rise. However, large uncertainties remain in projections of glacier mass loss on global and regional scales. We present an ensemble of 288 glacier mass and area change projections for the 21st century based on 11 glacier models using up to 10 general circulation models and four Representative Concentration Pathways (RCPs) as boundary conditions. We partition the total uncertainty into the individual contributions caused by glacier models, general circulation models, RCPs, and natural variability. We find that emission scenario uncertainty is growing throughout the 21st century and is the largest source of uncertainty by 2100. The relative importance of glacier model uncertainty decreases over time, but it is the greatest source of uncertainty until the middle of this century. The projection uncertainty associated with natural variability is small on the global scale but can be large on regional scales. The projected global mass loss by 2100 relative to 2015 (79 ± 56 mm sea level equivalent for RCP2.6, 159 ± 86 mm sea level equivalent for RCP8.5) is lower than, but well within, the uncertainty range of previous projections.
Highlights
Glaciers are prominent features of many mountain and arctic landscapes
We present an ensemble of 288 glacier mass and area change projections for the 21st century based on 11 glacier models using up to 10 general circulation models and four Representative Concentration Pathways (RCPs) as boundary conditions
The greatest source of uncertainty in projected glacier mass at the end of the 21st century is the lack of knowledge on future emissions, similar to global mean temperature change (Collins et al, 2013)
Summary
All glaciers on Earth (excluding the ice sheets, but including peripheral glaciers in Greenland and Antarctica) cover around 700,000 km (RGI Consortium, 2017) Their almost universal retreat in recent decades (Zemp et al, 2019), which has been MARZEION ET AL. Glaciers act as seasonal redistributors of water input into many drainage basins, modifying water availability (e.g., Bliss et al, 2014; Huss & Hock, 2018; Immerzeel et al, 2013, 2020). Both advancing and retreating glaciers can create geohazards, such as glacier lake outburst floods, catastrophic ice collapses, and increased slope instability (e.g., Kääb et al, 2018; Richardson & Reynolds, 2000)
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