Year-to-Year Fluctuations of Global Mass Balance of Small Glaciers and Their Contribution to Sea-Level Changes

Abstract

We estimate the means and the interannual variability during the last 30 yr of the mass balances of the small glaciers of the world (all glaciers except for the two large ice sheets), as well as the influence of these mass balance changes on fluctuations of sea level and their relation to climate. The mass balance data base was enriched by data for glaciers of the Arctic islands, Antarctica, and mountainous areas of Siberia, Central Asia, and the Caucasus, which have not been included in previous compilations. We also use a new estimate of the total area for the small glaciers on Earth: 680 × 103 km2. The global mean mass balance as a function of time was calculated three ways: the arithmetic mean for all glaciers (Gb1), arithmetic mean for a group of representative glaciers with long-term mass balance records (Gb2), and an area-weighted mean (Gb3). The last was calculated for seven large regions in order to estimate the contribution of small glaciers to sea-level change more precisely. The results include the following: • Gb1 and Gb2 show good correlations with each other and with global air temperature anomalies, with correlation coefficients around 0.90. • Gb3 produces a new global mass balance value, averaging −130 ± 33 mm yr−1, totaling −3.9 m in water equivalent for 1961–1990 period, or 0.25 ± 0.10 mm yr−1 in sea-level equivalent. This is about 14 to 18% of the average rate of sea-level rise in the last 100 yr. In the years with unusually negative mass balances, ice wastage contributed about 0.9 mm yr−1 to global sea-level rise, about 50% of the average rise over the recent past. • The contribution of glaciers to sea-level rise has increased greatly since the middle 1980s and even more steeply since the late 1980s, which is in agreement with the rise of global temperature.