The potential for sea level rise: New estimates from glacier and ice cap area and volume distributions

Projections of sea-level rise from mountain glaciers and ice caps for the next century and beyond should be based on an assessment of the ice available for melting. Projections to date are based on all regions except Greenland and Antarctica (the latter are considered separately by the IPCC), yet no sound estimates for the appropriate volume of ice and its potential for sea level rise are evident in the literature. An ice cap data set is compiled allowing the separate treatment of glacier area coverage data. Glacier inventory data are comprehensive enough in some regions to allow the estimation of glacier size distributions. The differences in the distributions are related to a metric of the regional topographic variability, allowing glacier size distributions to be estimated on a 1 degrees latitude longitude grid of cells containing glaciers. Appropriate volume-area scaling for glaciers and for ice caps gives global estimates of glacier and ice cap volumes by size class. This leads to an estimate of the total ice volume of 0.087 +/- 0.010 10(6) km(3) and a sea level rise equivalent of 0.241 +/- 0.026 m. The glaciers and ice caps contribute 41% and 59% to these estimates respectively. These values are based on data sets compiled during several decades, mainly in the second half of the 20th Century. We compare our results to published results that include the glaciers and icecaps at the margins of the Greenland and Antarctic ice sheets.