ABSTRACT: Are glaciers shrinking more rapidly now than formerly?

CGRG Bibliography of Canadian Geomorphology
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Abstract

Measurements of glacier shrinkage (reduction of area) have proliferated recently. What do the results tell us about change at the global scale, and is there evidence of recent acceleration of shrinkage to complement the well-established evidence of more negative mass balance? In most reports, the more recent rate s of shrinkage are more negative, but it is surprisingly difficult to generalize this observation. The variation of methods between successive area measurements continues to contribute significant uncertainty. The shrinkage measurements have irregular durations, with irregularly-distributed and often imprecisely documented dates. Measurements are more uncertain on smaller glaciers than on larger glaciers. Most seriously, we still do not know why in some regions the smaller glaciers are shrinking faster than larger ones while in other regions they are not. Allowing for these uncertainties, we see a strong acceleration of shrinkage between 1990-2000 and 2000-current. But, when errors of interpolation (to uniform, decadal periods) are a l so factored in, the acceleration becomes statistically insignificant. This result shows how important it is to keep trying to improve the methods and especially to solve the problem of size dependence. An early finding is that this problem may berelated to the restricted elevation range of many of the smallest glaciers. Region-to-region variations may depend on the vertical distribution of these ranges with respect to the rising altitude of the regional equilibrium line. A preliminary time series of global total glacier area suggests that shrinkage has yet to affect estimates of global average mass balance significantly. But it soon will.

Bibliography of Canadian Geomorphology