Even if the global climate did not continue to warm, sea level will still rise at least 184 ± 33 mm (7.2 ± 1.3 inches) due to the current mass wastage of the world’s mountain glaciers and ice caps, according to a new study published 11 February in Geophysical Research Letters.
If the climate continues to warm along current trends, a minimum of 373 ± 21 mm (14.7 ± 0.83 inches) of sea-level rise over the next 100 years is expected from glaciers and ice caps, according to the study by researchers at Regis University and the University of Colorado, Boulder. When compared to recent estimates from all other sources, melt water from glaciers must be considered as a particularly important fraction of the total sea-level rise expected this century.
Glaciers and ice caps can be split into regions where snow is accumulated and regions where snow and ice melt—if more snow accumulates than melts, the glacier will advance and grow larger. One of the most easily measured dimensions of a glacier, the accumulation area is linked to future changes in glacier volume and consequent changes in sea level.
Currently observed accumulation areas are too small, forcing glaciers to lose 27% of their volume to attain equilibrium with current climate. This will result in the 184 ± 33 mm of sea-level rise, according to the authors, who analyzed mass balance data from 86 mountain glaciers and ice caps from around the world.
A sea-level rise of 184 ± 33 mm is substantially larger than previous estimates that attribute 104 ± 25 mm to small glaciers and ice caps over the next 100 years when assuming no acceleration in ice loss. Our estimate places no bounds on time and only indicates the final outcome after all glaciers reach equilibrium. Therefore, it is possible that the additional ~80 mm represents sea-level rise that will occur after the 100 year time scale of previous estimates. However, with an e-folding response time that averages on decadal to century time scales for most glaciers, the bulk of the 184 mm of predicted rise is expected within this century.
The preceding analysis derives the changes in sea level to which we are committed by climate as it existed in 2006. Actual sea-level rise due to melting glaciers and ice caps will likely be much higher. Climate is not fixed and the rate of ice mass loss continues to accelerate.—Bahr et al. (2009)
Bahr, D. B., M. Dyurgerov, and M. F. Meier (2009), Sea-level rise from glaciers and ice caps: A lower bound, Geophys. Res. Lett., 36, L03501, doi: 10.1029/2008GL036309