First order projections of frontal ablation at Alaska tidewater glaciers

Frontal ablation (the sum of mass loss by calving and submarine melt) is an important yet poorly constrained component of tidewater glacier mass balance. Because of the complicated nature of both calving and ice-ocean interations, there are relatively few studies of frontal ablation on a regional scale, and no projections of frontal ablation on a regional scale. We compare two methods for constraining projections of frontal ablation from 50 Alaska tidewater glaciers. The first method is based on conservation of mass, and estimates frontal ablation using surface mass balance and glacier length. This method has already been used to estimate rates of frontal ablation from 50 Alaska tidewater glaciers, over the period 1950-2009; we estimate that frontal ablation accounts for more than half of the net mass loss for all Alaska tidewater glaciers over this time period. The second method uses a cross-sectional area of the glacier bed, along with different scenarios for hypothetical changes in glacier velocities, to estimate rates of frontal ablation from 50 Alaska tidewater glaciers. We use these two methods, along with projected surface mass balances, to present a range of future losses through frontal ablation from all 50 Alaska tidewater glaciers until 2050.