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RINEX files of high-precision GPS observations from Sit Kusa, southeast Alaska, during its 2020-2025 surge cycle. 

Data collected from a lidar rangefinder installed on Sít' Kusá (Turner Glacier) in Alaska, measuring surface height change from August 2022 to August 2024. Installation locations and instrument height above surface are recorded in the CSV file header along with variable descriptions. 

Data collected from a weather station installed on Sít' Kusá (Turner Glacier) in Alaska, from October 2022-October 2023. Station description is included in the metadata file and data variables are described in the CSV file header. 

Abstract: This archive contains seismic data collected from on and around Sít’ Kusá, over August 2020 to September 2025. Sít’ Kusá is a surge-type glacier, and the network was installed with support from the U.S. National Science Foundation to study changes in subglacial hydrology and basal processes over the course of a surge cycle. The period of deployment includes portions of surges that lasted from 2020 to 2021, quiescence between 2021 and 2025, and the onset of a next, but relatively weaker surge that started in 2025. The dataset consists of miniseed files and associated metadata that are archived through the EarthScope SAGE Data Management Center under networks YG_2020 and 1W_2024. The data were collected from 17 different stations and ground velocities were sampled at either 200 or 250 Hz (hertz). 

We will deploy up to six pairs of three-component broadband passive seismic stations along the margins of Turner Glacier. Five more intermediate-period geophones will be installed on the glacier surface (stations from the University of Idaho). Each glacier-adjacent pair will be orientated normal to the glacier flow, with one station on each side of the glacier and installed on bedrock or shallow sediment. Continuous broadband seismic data will be recorded at 100 Hz for the duration of the field deployment. This configuration will allow us to replicate the surface wave anisotropy study by Zhan (2019). Zhan (2019) used seismic noise to interrogate the subglacial drainage system of a surging glacier and found that changes in mechanical coupling between the ice and the glacial bed not only affects ice flow, but also the overall (poro)elastic properties of the ice‐water‐till‐bedrock system. From observations of seismic noise and the corresponding frequency-dependent surface-wave anisotropy, Zhan (2019) was able to infer that high subglacial water pressures are maintained by the impoundment of water in transverse basal crevasses during a glacier surge. We will apply the methodology of Zhan (2019) to determine if fluid-filled transverse basal crevasses exist prior to, during, and after surging at Turner Glacier. Passive seismic data will also allow us to track variations in subglacial water discharge. Recent observations of flow‐induced seismic noise, including at Alaskan tidewater glaciers similar to Turner Glacier, have demonstrated the ability to track increases and decreases in subglacial discharge and sediment transport, changes in the efficiency of the subglacial hydrologic system, and the extent of subglacial water pressurization (Bartholomaus et al., 2015; Gimbert et al. 2016; Bartholomaus et al., in prep.). The passive seismic data will be coupled with a numerical model of noise production by subglacial water flow and sediment transport to disentangle the noise produced by water or sediment transport using a technique newly developed by co-I Beaud. Extension of these techniques to ~15 km of Turner Glacier will allow us an unprecedented view of imbalances in water and sediment transport along the glacier bed, including and extending beyond the length of the actively surging glacier. To complement our assessment of subglacial water storage and transport, we will track changes in till consolidation and failure using seismic coda wave changes over time. Coda wave methods can be used to track seismic velocity variations in the subsurface (e.g., Sens-Schönfelder and Wegler 2006; Meier et al. 2010; Mainsant et al. 2012; Hillers et al. 2014; Hillers et al. 2015; Rivet, et al. 2015; Larose et al. 2015, and references therein). In general, the observed seismic velocity changes are attributed to changes in tectonic stress, hydrologic loading, or climate variation (e.g. air temperature or pressure). Mainsant et al. (2012) used coda wave changes to observe the failure of a clay layer at depth during a landslide. They showed that the seismic velocity of the sliding material, from daily noise-based coda wave measurements, decreased continuously and rapidly for several days prior to the catastrophic failure event as the layer became oversaturated. In order to test hypothesis 1, we will monitor changes in the till layer using this technique to determine the till state prior to, during, and after surge along the length of the glacier. To further refine this methodology, we will use the glacier parameters derived from active-source seismic observations to model the frequency-dependent sensitivity of surface waves (Mainsant et al. 2012) to the till layer and incorporate a new wavelet-based coda wave change measurement technique to improve depth resolution (Mordret et al., in review). The till state will be inferred from the observed frequency-dependent seismic velocity changes, with decreases in seismic velocity directly proportional to decreases in the shear modulus of the till. 

Abstract. En masse application of feature tracking algorithms to satellite image pairs has produced records of glacier surface velocities with global coverage, revolutionizing the understanding of global glacier change. However, glacier velocity records are sometimes incomplete due to gaps in the cloud-free satellite image record (for optical images) and failure of standard feature tracking parameters, e.g., search range, chip size, or estimated displacement, to capture rapid changes in glacier velocity. Here, we present a pipeline for pre-processing commercial high-resolution daily PlanetScope surface reflectance images and for generating georeferenced glacier velocity maps using NASA's autonomous Repeat Image Feature Tracking (autoRIFT) algorithm with customized parameters. We compare our velocity time series to the NASA Inter-Mission Time Series of Land Ice Velocity and Elevation (ITS_LIVE) global glacier velocity dataset, which is produced using autoRIFT, with regional-scale feature tracking parameters. Using five surge-type glaciers as test sites, we demonstrate that the use of customized feature tracking parameters for each glacier improves upon the velocity record provided by ITS_LIVE during periods of rapid glacier acceleration (i.e., changes greater than several meters per day over 2–3 months). We show that ITS_LIVE can fail to capture velocities during glacier surges but that both the use of custom autoRIFT parameters and the inclusion of PlanetScope imagery can capture the progression of order-of-magnitude changes in flow speed with median uncertainties of <0.5 m d−1. Additionally, the PlanetScope image record approximately doubles the amount of optical cloud-free imagery available for each glacier and the number of velocity maps produced outside of the months affected by darkness (i.e., polar night), augmenting the ITS_LIVE record. We demonstrate that these pipelines provide additional insights into speedup behavior for the test glaciers and recommend that they are used for studies that aim to capture glacier velocity change at sub-monthly timescales and with greater spatial detail. 

Abstract Globally, glaciers are changing in response to climate warming, with those that terminate in water often undergoing the most rapid change. In Alaska and northwest Canada, proglacial lakes have grown in number and size but their influence on glacier mass loss is unclear. We characterized the rates of retreat and mass loss through frontal ablation of 55 lake-terminating glaciers (>14 000 km²⁾in the region using annual Landsat imagery from 1984 to 2021. We find a median retreat rate of 60 m a⁻¹(interquartile range = 35–89 m a⁻¹) over 1984–2018 and a median loss of 0.04 Gt a⁻¹(0.01–0.15 Gt a⁻¹) mass through frontal ablation over 2009–18. Summed over 2009–18, our study glaciers lost 6.1 Gt a⁻¹to frontal ablation. Analysis of bed profiles suggest that glaciers terminating in larger lakes and deeper water lose more mass to frontal ablation, and that the glaciers will remain lake-terminating for an average of 74 years (38–177 a). This work suggests that as more proglacial lakes form and as lakes become larger, enhanced frontal ablation could cause higher mass losses, which should be considered when projecting the future of lake-terminating glaciers. 

Abstract Glacier surges are opportunities to study large amplitude changes in ice velocities and accompanying links to subglacial hydrology. Although the surge phase is generally explained as a disruption in the glacier's ability to drain water from the bed, the extent and duration of this disruption remain difficult to observe. Here we present a combination of in situ and remotely sensed observations of subglacial water discharge and evacuation during the latter half of an active surge and subsequent quiescent period. Our data reveal intermittently efficient subglacial drainage prior to surge termination, showing that glacier surges can persist in the presence of channel-like subglacial drainage and that successive changes in subglacial drainage efficiency can modulate active phase ice dynamics at timescales shorter than the surge cycle. Our observations favor an explanation of fast ice flow sustained through an out-of-equilibrium drainage system and a basal water surplus rather than binary switching between states in drainage efficiency. 

Abstract We use satellite image processing techniques to measure surface elevation and velocity changes on a temperate surging glacier, Sít’ Kusá, throughout its entire 2013–2021 surge cycle. We present detailed records of its dynamic changes during quiescence (2013–2019) and its surge progression (2020–2021). Throughout quiescence, we observe order-of-magnitude speedups that propagate down-glacier seasonally from the glacier's upper northern tributary, above a steep icefall, into the reservoir zone for the surging portion of the glacier. The speedups initiate in fall and gradually accelerate through winter until they peak in late spring, ~1 − 2 months after the onset of melt. Propagation distance of the speedups controls the distribution of mass accumulation in the reservoir zone prior to the surge. Furthermore, the intensity and propagation distance of each year's speedup is correlated with the positive degree day sum from the preceding melt season, suggesting that winter melt storage drives the seasonal speedups. We demonstrate that the speedups are kinematically similar to the 2020–2021 surge, differing mainly in that the surge propagates past the dynamic balance line at the lower limit of the reservoir zone, likely triggered by the exceedance of a tipping point in mass accumulation and basal enthalpy in the reservoir zone.