Abstract Submarine melt can account for substantial mass loss at tidewater glacier termini. However, the processes controlling submarine are poorly understood due to limited observations of Here a in central West Greenland, we identify subglacial discharge outlets and infer across terminus using direct face. We find extensive melting associated with small outlets. While majority is routed single, large channel, not fed by tributaries drive rates excess 3.0 m d −1 85% total estimated...

Glacier terminus changes are one of the hallmarks worldwide glacier change, and thus, there is significant focus on controls limits to retreat in literature. Here we use observational record change from satellite remote sensing data characterize central West Greenland with a last 30 years. We compare observations glacier/fjord geometry available bed bathymetry find that accelerates through wide, overdeepened parts characterized by retrograde slopes. morphology overdeepening can be used as...

Abstract Meltwater from the Greenland Ice Sheet often drains subglacially into fjords, driving upwelling plumes at glacier termini. Ocean models and observations of submarine termini suggest that enhance melt undercutting, leading to calving potential destabilization. Here we systematically evaluate how simulated plume structure during summer months depends on realistic ranges subglacial discharge, depth, ocean stratification 12 fjords. Our results show grounding line depth is a strong...

Abstract Water that pressurizes the base of glaciers and ice sheets enhances glacier velocities modulates glacial erosion. Predicting flow erosion therefore requires knowledge subglacial channel evolution, which remains observationally limited. Here we demonstrate detailed analysis seismic ground motion caused by water at Mendenhall Glacier (Alaska) allows for continuous measurement daily to subseasonal changes in basal pressure gradient, size, sediment transport. We observe intermittent...

Abstract At tidewater glaciers, plume dynamics affect submarine melting, fjord circulation, and the mixing of meltwater. Models often rely on buoyant theory to parameterize plumes melting; however, these parameterizations are largely untested due a dearth near‐glacier measurements. Here we present high‐resolution ocean survey by ship remotely operated boat near terminus Kangerlussuup Sermia in west Greenland. These novel observations reveal 3‐D structure transport near‐surface plume,...

Abstract Subglacial discharge influences glacier basal motion and erodes redeposits sediment. At tidewater termini, drives submarine terminus melting, affects fjord circulation, is a central component of proglacial marine ecosystems. However, our present inability to track subglacial its variability significantly hinders understanding these processes. Here we report observations hourly seasonal variations in 1.5–10 Hz seismic tremor that strongly correlate with but not motion, weather, or...

Accurately projecting mass loss from ice sheets is of critical societal importance. However, despite recent improvements in sheet models, our analysis a effort to project contribution future sea level suggests that few models reproduce historical accurately and they appear much too confident the spread predicted outcomes. The inability observations raises concerns about models' skill at loss. Here we suggest uncertainties Greenland Antarctica may well be significantly higher than reported...

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. present detailed records of dynamic during quiescence (2013–2019) progression (2020–2021). Throughout quiescence, we observe order-of-magnitude speedups that propagate down-glacier seasonally from the glacier's upper northern tributary, above steep icefall, into reservoir zone for portion glacier. The...

Abstract Nearly 100 days of hourly glacier motion, hydrology and hydrochemistry measurements on Kennicott Glacier, Alaska, USA, demonstrate the complicated relationship between water motion at bed. Our observations capture transient response to seasonal daily melt cycles, a jökulhlaup that prompts sixfold increase in speed. Sliding is promoted whenever inputs exceed capacity subglacial hydrologic system transmit water. Sensitivity sliding meltwater varies strongly through season, implying...

Abstract The majority of Greenland tidewater glaciers undergo a seasonal cycle in terminus position, characterized by wintertime advance and summertime retreat. Understanding mechanisms that control cycles can help elucidate how regulate dynamic ice loss on longer timescales. However, controls position are numerous complex. To address this, we compare time series satellite‐derived positions for central west with observations environmental forcings, including runoff at the grounding line,...

ABSTRACT Neighboring tidewater glaciers often exhibit asynchronous dynamic behavior, despite relatively uniform regional atmospheric and oceanic forcings. This variability may be controlled by a combination of local factors, including glacier fjord geometry, heat content circulation, surface melt. In order to characterize understand contrasts in adjacent dynamics, we made coincident ice-ocean-atmosphere observations at high temporal resolution (minutes weeks) within 10 000 km 2 area near...

Greenland's outlet glaciers have been a leading source of mass loss and accompanying sea-level rise from the Greenland Ice Sheet (GrIS) over last 25 years. The dynamic component glacier depends on both ice flux through terminus inland extent thinning, initiated at ice-ocean interface. Here, we find limits to spread thinning that initiates termini for 141 ocean-terminating around GrIS. Inland diffusion is limited by steep reaches bed topography call "knickpoints." We show knickpoints exist...

Abstract Frontal ablation processes at marine‐terminating glaciers are challenging to observe and difficult represent in numerical ice flow models, yet play critical roles modulating sheet mass balance. Current models typically rely on simple iceberg calving prescribe either terminus positions or rates, but the relative accuracies uncertainties of these remain largely unconstrained scale. Here, we evaluate six published against spatially temporally diverse observations from 50 outlet...

Iceberg calving is known to release substantial seismic energy, but little about the specific mechanisms that produce icequakes. At Yahtse Glacier, a tidewater glacier on Gulf of Alaska, we draw upon local network seismometers and focus 80 hours concurrent, direct observation terminus show dominant source seismicity. To elucidate seismogenic mechanisms, synchronized video seismograms reveal majority energy produced during iceberg interactions with sea surface. Icequake peak amplitudes...

ABSTRACT The subglacial hydrologic system exerts strong controls on the dynamics of overlying ice, yet parameters that govern evolution this are not widely known or observable. To gain a better understanding these parameters, we invert spatially averaged model hydrology from observations ice surface velocity and outlet stream discharge at Kennicott Glacier, Wrangell Mountains, AK, USA. identify independent formally non-dimensionalize forward model. After specifying suitable prior...

Abstract Ice stream bed topography contains key evidence for the ways ice streams interact with, and are potentially controlled by, their beds. Here we present first application of two‐dimensional Fourier analysis to 22 marine terrestrial topographies from 5 regions in Antarctica Canada, with without mega‐scale glacial lineations (MSGLs). We find that MSGL‐rich sedimentary beds is characterized by multiple, periodic wavelengths between 300 1200 m amplitudes decimeters a few meters. This...

Abstract The seismic signatures of calving events, i.e., icequakes, offer an opportunity to examine variability with greater precision than is available other methods. Here using observations from Yahtse Glacier, Alaska, we describe methods detect, locate, and characterize icequakes. We combine these icequake records a coincident, manually generated record observed events develop validate statistical model through which can infer iceberg sizes the properties find that duration single most...

Abstract Subglacial water flow impacts glacier dynamics and shapes the subglacial environment. However, due to challenges of observing beds, spatial organization systems time scales conduit evolution migration are largely unknown. To address these questions, we analyze 1.5‐ 10‐Hz seismic tremor that associate with flow, hat is, glaciohydraulic tremor, at Taku Glacier, Alaska, throughout 2016 melt season. We use frequency‐dependent polarization analysis estimate propagation direction (related...

Abstract Seasonal variability in the Greenland Ice Sheet's (GrIS) sliding speed is regulated by response of subglacial drainage system to meltwater inputs. However, importance channelization relative dewatering isolated cavities controlling seasonal ice deceleration remains unsolved. Using motion, moulin hydraulic head, and glaciohydraulic tremor measurements, we show passing a floodwave triggered upglacier supraglacial lake drainages slowed wintertime background speeds without increasing...

Abstract Glacier surges are opportunities to study large amplitude changes in ice velocities and accompanying links subglacial hydrology. Although the surge phase is generally explained as a disruption glacier's ability drain water from bed, extent duration of this remain difficult observe. Here we present combination situ remotely sensed observations discharge evacuation during latter half an active subsequent quiescent period. Our data reveal intermittently efficient drainage prior...

Abstract. Crevasses are affected by and affect both the stresses surface mass balance of glaciers. These effects brought on through potentially important controls meltwater routing, glacier viscosity, iceberg calving, yet there few direct observations crevasse sizes locations to inform our understanding these interactions. Here we extract depth estimates for visible portion crevasses from high-resolution elevation 52 644 19 Greenland We then compare observed depths with those calculated...