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Abstract Accelerated climate warming has caused the majority of marine-terminating glaciers in the Northern Hemisphere to retreat substantially during the twenty-first century. While glacier retreat and changes in mass balance are widely studied on a global scale, the impacts of deglaciation on adjacent coastal geomorphology are often overlooked and therefore poorly understood. Here we examine changes in proglacial zones of marine-terminating glaciers across the Northern Hemisphere to quantify the length of new coastline that has been exposed by glacial retreat between 2000 and 2020. We identified a total of 2,466 ± 0.8 km (123 km a⁻¹) of new coastline with most (66%) of the total length occurring in Greenland. These young paraglacial coastlines are highly dynamic, exhibiting high sediment fluxes and rapidly evolving landforms. Retreating glaciers and associated newly exposed coastline can have important impacts on local ecosystems and Arctic communities. 

Abstract. Glacier velocity measurements are essential to understand ice flow mechanics, monitor natural hazards, and make accurate projections of future sea-level rise. Despite these important applications, the method most commonly used to derive glacier velocity maps, feature tracking, relies on empirical parameter choices that rarely account for glacier physics or uncertainty. Here we test two statistics- and physics-based metrics to evaluate velocity maps derived from optical satellite images of Kaskawulsh Glacier, Yukon, Canada, using a range of existing feature-tracking workflows. Based on inter-comparisons with ground truth data, velocity maps with metrics falling within our recommended ranges contain fewer erroneous measurements and more spatially correlated noise than velocity maps with metrics that deviate from those ranges. Thus, these metric ranges are suitable for refining feature-tracking workflows and evaluating the resulting velocity products. We have released an open-source software package for computing and visualizing these metrics, the GLAcier Feature Tracking testkit (GLAFT). 

Abstract Glacier surges are periodic episodes of mass redistribution characterized by dramatic increases in ice flow velocity and, sometimes, terminus advance. We use optical satellite imagery to document five previously unexamined surge events of Sít’ Kusá (Turner Glacier) in the St. Elias Mountains of Alaska from 1983 to 2013. Surge events had an average recurrence interval of ~5 years, making it the shortest known regular recurrence interval in the world. Surge events appear to initiate in the winter, with speeds reaching up to ~25 m d −1 . The surges propagate down-glacier over ~2 years, resulting in maximum thinning of ~100 m in the reservoir zone and comparable thickening at the terminus. Collectively, the rapid recurrence interval, winter initiation and down-glacier propagation suggest Sít’ Kusá's surges are driven by periodic changes in subglacial hydrology and glacier sliding. Elevation change observations from the northern tributary show a kinematic disconnect above and below an icefall located 23 km from the terminus. We suggest the kinematic disconnect inhibits drawdown from the accumulation zone above the icefall, which leads to a steady flux of ice into the reservoir zone, and contributes to the glacier's exceptionally short recurrence interval.