Vertical motion and ice thickness variation in western North America

Maps of the ice covered area of western North America and records of mass balance of 23 mountain glaciers in this region, were used to construct a gridded data set of average mass balance and to calculate a detailed description of time averaged radial displacement (uplift) in the region for the period, 1961-1990. While the region studied is tectonically active, there is some agreement between the rates of vertical uplift at several tide gauge sites along the Inside Passage of Alaska, and the measured sea level drop at these stations. The average sea level contribution from the melting of western North American glaciers, calculated from these gridded data is 0.4 ± 0.2 mm/yr, and is greater than prior esti-mates for the same time period.