1. Alfred Wegener Institute for Polar and Marine Research, 27515 Bremerhaven, Germany
2. School of Environment and Development, University of Manchester, Manchester M13 9PL, UK
3. †Present address: CATE, Dalton Research Institute, Manchester Metropolitan University, Manchester M1 5GD, UK

Correspondence to: Sarah C. B. Raper^1,3 Correspondence and requests for materials should be addressed to S.C.B.R. (Email: s.raper@mmu.ac.uk).

The mean sea level has been projected to rise in the 21st century as a result of global warming¹. Such projections of sea level change depend on estimated future greenhouse emissions and on differing models, but model-average results from a mid-range scenario (A1B) suggests a 0.387-m rise by 2100 (refs 1, 2). The largest contributions to sea level rise are estimated to come from thermal expansion (0.288 m) and the melting of mountain glaciers and icecaps (0.106 m), with smaller inputs from Greenland (0.024 m) and Antarctica (- 0.074 m)¹. Here we apply a melt model³ and a geometric volume model⁴ to our lower estimate of ice volume^{5, 6, 7} and assess the contribution of glaciers to sea level rise, excluding those in Greenland and Antarctica. We provide the first separate assessment of melt contributions from mountain glaciers and icecaps, as well as an improved treatment of volume shrinkage. We find that icecaps melt more slowly than mountain glaciers, whose area declines rapidly in the 21st century, making glaciers a limiting source for ice melt. Using two climate models, we project sea level rise due to melting of mountain glaciers and icecaps to be 0.046 and 0.051 m by 2100, about half that of previous projections^{1, 8}.

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