W. Greuell, Melt-water accumulation on the surface of the Greenland ice sheet: Effect on albedo and mass balance, GEOGR ANN A, 82A(4), 2000, pp. 489-498
Satellite-derived albedo maps of the western part of the Greenland ice shee
t (between 64.5 and 70.5 degreesN) reveal a north-south extending zone with
relatively low albedos at some distance from the ice margin. In the litera
ture it has been hypothesized that this "dark zone" is due to a local maxim
um in melt-water accumulation on the ice-covered surface. A plausible expla
nation for this maximum in melt-water accumulation is that relative to the
situation within the "dark zone", melt-water accumulation is reduced at hig
her elevations by a smaller melt-water production rate whereas runoff occur
s more easily at lower elevations where slopes are generally steeper.
For the present paper AVHRR images from eight years (1990-1997) were analys
ed. The following indications confirming the "melt-water accumulation hypot
hesis" were found: (1) there is a significant correlation between the annua
l mean albedo lowering within the "dark zone" and the annual amount of melt
as inferred from local mass-balance measurements: and (2) within each summ
er season the albedo lowering within the "dark zone" seems to respond to th
e melt-water production rate as inferred from local temperature measurement
s. The effect of melt-water accumulation on the albedo implies a positive f
eedback between the albedo and the amount of melt. It is estimated that app
roximately 40% of the interannual mass-balance variations in the ''dark zon
e" are due to this feedback.