GLACIER TERMINUS FLUCTUATIONS ON MOUNT BAKER, WASHINGTON, USA, 1940-1990, AND CLIMATIC VARIATIONS

The terminus positions of six glaciers located on Mount Baker, Washing ton, were mapped by photogrammetric techniques at 2- to 7-yr intervals for the period 1940-1990. Although the timing varied slightly, each o f the glaciers experienced a similar fluctuation sequence consisting o f three phases: (1) rapid retreat, beginning prior to 1940 and lasting through the late 1940s to early 1950s; (2) approximately 30 yr of adv ance, ending in the late 1970s to early 1980s; (3) retreat though 1990 . Terminus positions changed by up to 750 m during phases, with the ad vance phase increasing the lengths of glaciers by 13 to 24%. These flu ctuations are well explained by variations in a smoothed time-series o f accumulation-season precipitation and ablation-season mean temperatu re. The study glaciers appear to respond to interannual scale changes in climate within 20 yr or less. The glaciers on Mount Baker have a ma ritime location and a large percentage of area at high elevation, whic h may make their termini undergo greater fluctuations in response to c limatic changes, especially precipitation variations, than most other glaciers in the North Cascades region.