An 85-year record of glacier change and refined projections for Kennicott and Root Glaciers, Alaska.

Long-term historical records of glacier mass change are key to advancing understanding of glaciers' response to climate change and improving predictions of their future. Here, we use historical aerial photographs and new bed topography measurements to provide an 85-year record of glacier change on Kennicott and Root Glaciers in Alaska. At the glacier terminus, little change is observed in the two decades prior to 1957, followed by ongoing and accelerating mass loss with dynamically driven spatial variability. Glacier projections, constrained by these mass loss estimates, predict that Kennicott Glacier will lose 38 ± 14% to 63 ± 18% of its mass by 2100, relative to 2000, and Root Glacier will lose 38 ± 11% to 58 ± 12%, depending on the emissions scenario. These results differ by up to 22% from similar predictions made by projections calibrated from the past two decades of glacier change only. This highlights the importance of long-term glacier mass-loss records that help us better project far-reaching consequences of climate change related to sea level rise, water resources, natural hazards, climate, and culture.