Dynamics and stability of Alaskas lake-terminating glaciers

Frontal ablation (iceberg calving and subaqueous melt) provides a mechanism for rapid mass loss on glaciers and ice sheets that terminate in water. While frontal ablation processes at marine-terminating glaciers have received substantial attention, considerably less is known about the dynamics of lake-terminating glaciers. While lake-terminating glaciers are generally thought to calve less vigorously than their marine-terminating counterparts, they have been observed to experience faster rates of mass loss than marine- or land-terminating glaciers in Alaska and High Mountain Asia. Here, we characterize multi-decadal retreat rates across Alaska and northwest Canadas lake-terminating glaciers using Landsat imagery over 1984 2021. We combine these observations with existing ice thickness, surface mass balance, and surface velocity datasets to estimate rates of frontal ablation on these glaciers. Further, we investigate the impact of water depth and remotely-sensed water temperature on lacustrine frontal ablation. We utilize long-term records of glacier speed to document which glaciers experience dynamic instability in response to terminus-forced perturbations. In low-elevation coastal settings, intrusion of warm, saline ocean water into freshwater proglacial lakes could increase rates of frontal ablation. We investigate whether coastal lake-terminating glaciers experience different behavior than their higher elevation counterparts, as well as whether the narrow forelands separating a lake from the ocean appear stable over the past decades. This work will increase understanding of how frontal ablation dynamics differ between lake- and marine-terminating glaciers, as well as the future stability of lake-terminating glaciers across the Gulf of Alaska, with implications for sea level rise and local landscape and ecosystem change.