SEASONAL CLIMATIC FORCING OF ALPINE GLACIERS REVEALED WITH ORBITAL SYNTHETIC-APERTURE RADAR

The evolution of four dynamic radar glacier zones at the surface of an alpine icefield in British Columbia is monitored using a time series of 35 First European Remote Sensing Satellite (ERS-1) synthetic apertu re radar (SAR) images acquired from 1992 to 1994. These zones result f rom changing wetness and textural properties, and appear to represent: (1) cold snow with no liquid water present; (2) an initial melt front with an upper boundary near the elevation of the 0 degrees isotherm; (3) metamorphosed, rapidly melting first-year snow with a rough or pit ted surface; and (4) bare ice. This interpretation is aided by tempera ture and runoff data, air photographs and field measurements of snowpa ck properties acquired simultaneously with two ERS-1 SAR scenes, ice-s urface elevations derived from 1:50000 topographic maps and simulation s or radar backscatter from a geometric optics model of surface scatte ring. Meltwater production is affected by the development of zones (2) , (3) and (4), which form, migrate up-elevation and disappear each yea r between April and September.