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A subglacial groundwater system beneath Taylor Glacier, Antarctica, discharges hypersaline, iron‐rich brine episodically at the glacier surface to create Blood Falls. However, the triggering mechanism for these brine release events is not yet understood. Identifying which fracture processes are observed seismically can help us better characterize the hydrological system at Taylor Glacier, and more generally, provide us with a broader understanding of englacial hydrologic activity in cold glaciers. We document wintertime brine discharge using time‐lapse photography. Subfreezing air temperatures during the brine discharge indicate that surface melt‐induced hydrofracture is an unlikely trigger for brine release. Further, we analyze local seismic data to test a hypothesis that fracturing generates elevated surface wave energy preceding and/or coinciding with brine release events. Our results show no discernible elevated Rayleigh wave activity prior to or during Blood Falls brine release. Instead, we find a pattern of seismic events dominated by a seasonal signal, with more Rayleigh events occurring in the summer than the winter from the Blood Falls source area. We calculate that the volumetric opening of cracks that would generate Rayleigh waves at our detection limits are of similar size to myriad cracks in glacier ice, lake ice, and frozen sediment in the terminus area. We therefore propose that any fracturing coincident with brine release activity likely consists of a series of smaller opening events that are masked by other seismicity in the local environment. Plain Language Summary: Blood Falls is a reddish feature that forms at the terminus of Taylor Glacier in Antarctica when hypersaline, iron‐rich brine flows from sediment under the glacier up through the ice to emerge from cracks at the surface. We used data from a time‐lapse camera and nearby seismic sensors to document a brine release. Our images show a brine release event starting in May 2014 (austral winter), and fractures in the glacier surface observed following the event encouraged us to hypothesize that we would detect an increase in Rayleigh waves (a type of seismic wave that can be generated by surface crack opening). However, we do not observe an increase in Rayleigh wave activity prior to or during brine release. When we estimate the average size of the fractures that we detect, we find the size is similar to many types of cracks in the nearby environment (for instance, cracks in the lake ice). We conclude that any Rayleigh wave seismicity that occurred during the Blood Falls brine release must be from a series of crack openings smaller than our detection limit, and that other cracks opening in the nearby environment may mask any signal specific to the Blood Falls release. Key Points: Time‐lapse photos capture wintertime Blood Falls brine releaseBrine release occurs without evidence for enhanced Rayleigh wave seismicity near the release pointThe Blood Falls crack may open as a series of small fracture events, masked by local seismicity [ABSTRACT FROM AUTHOR]

Sliding of glacial ice over its base is typically described by a frictionless or slowly deforming bed. This view is challenged by recent seismic observations of stick‐slip motion at the ice‐bed interface. We revisit a high‐frequency (20–35 Hz) harmonic tremor recorded on Gornergletscher, Switzerland. In contrast to previous interpretation in terms of glaciohydraulic tremor, we present evidence for superimposed stick‐slip episodes as tremor sources: we locate the tremor source with matched field processing polarity optimization, which allows for azimuthal polarity patterns associated with nonisotropic moment tensors and yields a tremor source clustering near the glacier bed. Our analysis confirms an S wave radiation pattern in agreement with a double‐couple source derived from ice sliding over bedrock and explains our tremor observations in terms of glacier stick‐slip motion. Adding to observations of stick‐slip tremor beneath polar ice streams, this first report on stick‐slip tremor beneath Alpine ice favors widespread seismogenic glacier sliding. Plain Language Summary: For many years, researchers have observed cryoseismic stick‐slip tremor exclusively in Antarctica. Stick‐slip tremor is due to small repeating slip events at the glacier bed as a glacier advances downstream. This type of tremor is a telltale sign of what is happening at the ice‐bed interface and indicates frictional sliding. Here, we present first evidence for stick‐slip tremor at an Alpine glacier—Gornergletscher, Switzerland. We identify indicators in the seismic signature and apply data processing techniques that reveal that the creeping glacier sole moves under the influence of gravity and irregularly rubs over a sticky area at the bed. Key Points: We revisit a harmonic tremor recorded by a seismic array on an Alpine glacier, which was previously interpreted as hydraulic tremorApplying matched field processing that accounts for nonisotropic radiation patterns suggests a tremor source at the ice‐bedrock interfaceA focal mechanism derived from ice slip over bedrock explains our results and suggests seismogenic stick‐slip motion at the glacier's base [ABSTRACT FROM AUTHOR]