HR: 13:40h
AN: C22A-01 INVITED     [PDF]
TI: A Macroscopic Approach to the Response of Glaciers to Climate
AU: * Harrison, W D
EM: harrison@gi.alaska.edu
AF: Geophysical Institute, University of Alaska, Fairbanks, AK 99775-7320 United States
AB: We explore a drastic simplification of the theory of glacier response to small climate changes, a "macroscopic" one in which the distribution of thickness change is replaced by its integrated value, the total volume change. We also deal with change of area near the terminus rather than change in length. In the resulting area-volume relationship there are three parameters: an "area" time scale characterizing the time for area to respond to changes in volume, a thickness scale, and area characterizing the condition of the initial state. The first two characterize the dynamics of the glacier, and are 8 years and 123 meters for South Cascade Glacier as obtained by a fit of cumulative balance and area data from 1977 to 1997. Combining the area-volume relationship with a version of mass continuity expressed in terms of these same variables produces a theory of response of area and volume to climate in which a second time scale appears, the "volume" time scale. It is about 48 m for South Cascade Glacier, and differs from the usual estimate in that it includes the effect of both glacier length and surface elevation. The macroscopic theory characterizes a glacier as a damped oscillator forced by climate. For climate driving frequencies that are not too high, it reproduces the response of South Cascade Glacier predicted by the more complicated traditional theory of Nye; the analogous oscillator is critically damped. The response can be expressed in terms of a single "reaction" time scale, the geometric mean of the area and volume time scales.
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2003 Fall Meeting