YEAR-TO-YEAR FLUCTUATIONS OF GLOBAL MASS-BALANCE OF SMELL GLACIERS AND THEIR CONTRIBUTION TO SEA-LEVEL CHANGES

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 gla ciers except for the two large ice sheets), as well as the influence o f these mass balance changes on fluctuations of sea level and their re lation 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 X 10(3) km(2). The global mean m ass balance as a function of time was calculated three ways: the arith metic mean for all glaciers (Gb(1)), arithmetic mean for a group of re presentative glaciers with longterm mass balance records (Gb(2)), and an area-weighted mean (Gb(3)). The last was calculated for seven large regions in order to estimate the contribution of small glaciers to se a-level change more precisely. The results include the following: Gb(1 ) and Gb(2) shaw good correlations with each other and with global air temperature anomalies, with correlation coefficients around 0.90. Gb( 3) 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 yea rs with unusually negative mass balances, ice wastage contributed abou t 0.9 mm yr(-1) to global sea-level rise, about 50% of the average ris e over the recent past. The contribution of glaciers to sea-level rise has increased greatly since the middle 1980s and even more steeply si nce the late 1980s, which is in agreement with the rise of global temp erature.