Mass balance of mountain and subpolar glaciers: A new global assessment for 1961-1990

The goals of this article are (1) to combine published and unpublished mass balance measured data on more than 200 glaciers, check the quality of the data, digitize, and compile these for the period from the end of World War LI (1945) to 1993 (with emphasis on the 1961-1990 period), and (2) to perform a review and analysis of this compilation. A simple global average mass balance for this period is -164 mm yr(-1) (totaling -4.9 m) in water equivalent, not including iceberg calving. There are only about 40 glaciers with continuous mass balance measurements for more than 20 yr, but more than 100 with 1 to 5 yr of mass balance records. The glaciers under mass balance study differ in size from very small mountain cirque glaciers (less than I km?) to large valley glaciers (several hundred square kilometers) and subpolar ice caps with an area of several thousand square kilometers. Continuous and long-term mass balance measurements have been carried out mostly on middle-size glaciers with several exceptions. There are no longterm mass balance measurements in the following size classes: from 2(-6) to 2(-3) km(2); 2(8) to 2(10); and above 2(12) km(2). The area of these unmeasured size classes of glaciers is about 200 x 10(3) km(2), or about 29% of the global glacier area. The glacier area of mountain and subpolar glaciers (including local glaciers around Greenland and Antarctica ice sheets) is taken to be about 680 X 10(3) km(2). The reduction in global glacier area due to retreat is calculated as 6-8 X 10(3) km(2) from 1961-1990.