Abstract. Ice-marginal lakes impact glacier mass balance, water resources, and ecosystem dynamics and can produce catastrophic glacial lake outburst floods (GLOFs) via sudden drainage. Multitemporal inventories of ice-marginal lakes are a critical first step in understanding the drivers of historic change, predicting future lake evolution, and assessing GLOF hazards. Here, we use Landsat-era satellite imagery and supervised classification to semi-automatically delineate lake outlines for four ∼5-year time periods between 1984 and 2019 in Alaska and northwest Canada. Overall, ice-marginal lakes in the region have grown in total number (+183 lakes, 38 % increase) and area (+483 km2, 59 % increase) between the time periods of 1984–1988 and 2016–2019. However, changes in lake numbers and area were notably unsteady and nonuniform. We demonstrate that lake area changes are connected to dam type (moraine, bedrock, ice, or supraglacial) and topological position (proglacial, detached, unconnected, ice, or supraglacial), with important differences in lake behavior between the sub-groups. In strong contrast to all other dam types, ice-dammed lakes decreased in number (six fewer, 9 % decrease) and area (−51 km2, 40 % decrease), while moraine-dammed lakes increased (56 more, 26 % and +479 km2, 87 % increase for number and area, respectively) at a faster rate than the average when considering all dam types together. Proglacial lakes experienced the largest area changes and rate of change out of any lake position throughout the period of study and moraine-dammed lakes which experienced the largest increases are associated with clean-ice glaciers (<19 % debris cover). By tracking individual lakes through time and categorizing lakes by dam type, subregion, and topological position, we are able to parse trends that would otherwise be aliased if these characteristics were not considered. This work highlights the importance of such lake characterization when performing ice-marginal lake inventories and provides insight into the physical processes driving recent ice-marginal lake evolution.

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&lt;p&gt;As ice thins and retreats due to climate change, glacial lakes can form and grow. Rapid lake drainage can produce devastating outburst floods leading many to propose that hazards from glacial lakes are increasing. Outburst flood compilations do show an increase in the number of events documented over time, however, recent studies attribute such trends to observational bias. This leaves large uncertainty about current and future glacial-lake hazards. Here, we focus on ice-dammed lake drainages in Alaska, as a third of documented events globally occurred in this region. Using multitemporal satellite imagery (Landsat and Sentinel-2), we documented 1150 drainages from 106 lakes over 1985&amp;#8211;2020. Accounting for the increase in satellite imagery availability over time, we find no temporal trend in drainage frequency. Furthermore, 70% of lakes decreased in estimated volume and peak discharge since the 1960s, and nearly a third of lakes released earlier through time. These results suggest a decrease in overall regional flood hazard from ice-dammed lakes and motivates an unbiased look at other regions.&lt;/p&gt;

Abstract. The Chaos Canyon landslide, which collapsed on the afternoon of June 28th, 2022 in Rocky Mountain National Park presents an opportunity to evaluate instabilities within alpine regions faced with a warming and dynamic climate. Video documentation of the landslide was captured by several eyewitnesses and motivated a rapid field campaign. Initial estimates put the failure area at 66,630 m2, with an average elevation of 3,555 m above sea level. We undertook an investigation of previous movement of this landslide, measured the volume of material involved, evaluated the potential presence of interstitial ice/snow within the failed deposit, and examined potential climatological forcings at work in causing the collapse of the slope. Satellite radar and optical measurements were used to measure deformation of the landslide in the years leading up to collapse. From 2017 to 2019, the landslide moved ∼5 m yr-1, accelerating to 17 m yr-1 in 2019. Movement took place through both internal deformation and basal sliding. Climate analysis reveals the collapse took place during peak snowmelt, and 2022 followed 10 years of higher than average positive degree day sums. We also made use of slope stability modeling to test what factors controlled the stability of the area. Models indicate even a small increase in the water table reduces the Factor of Safety to <1, leading to failure. Material volumes were estimated using Structure from Motion (SfM) models incorporating photographs from two field expeditions on July 8th, 2022 – 10 days after the slide. Detailed mapping and SfM models indicate ∼ 1,258,000 ± 150,000 m3 of material was deposited at the slide toe and ∼1,340,000 ± 133,000 m3 of material was evacuated from the source area. Our holistic approach to the collapse of the Chaos Canyon landslide provided an opportunity to examine a landslide that may be representative of future dynamic alpine topography, wherein failures becomes more common in a warming climate.