A5017218652- Cryospheric studies and observations
- Arctic and Antarctic ice dynamics
- Winter Sports Injuries and Performance
- Geology and Paleoclimatology Research
- Climate change and permafrost
- Landslides and related hazards
- Seismology and Earthquake Studies
- Meteorological Phenomena and Simulations
- Icing and De-icing Technologies
- Methane Hydrates and Related Phenomena
- Oceanographic and Atmospheric Processes
- Aerospace Engineering and Energy Systems
- Nuclear Physics and Applications
- Climate variability and models
- Adventure Sports and Sensation Seeking
Los Alamos National Laboratory
2022-2025
British Antarctic Survey
2020-2023
Bjerknes Centre for Climate Research
2023
Natural Environment Research Council
2020-2023
New York University
2015-2019
Courant Institute of Mathematical Sciences
2016-2019
Oceanography Society
2016
Abstract Thwaites Glacier is one of the fastest-changing ice–ocean systems in Antarctica 1–3 . Much ice sheet within catchment grounded below sea level on bedrock that deepens inland 4 , making it susceptible to rapid and irreversible loss could raise global by more than half a metre 2,3,5 The rate extent loss, whether proceeds irreversibly, are set ocean conditions basal melting grounding-zone region where first goes afloat 3,6 both which largely unknown. Here we show—using observations...
Abstract Recent work on the Filchner‐Ronne Ice Shelf (FRIS) system has shown that a redirection of coastal current in southeastern Weddell Sea could lead to regime change which an intrusion warm Modified Circumpolar Deep Water results large increases basal melt rate. Work date mostly focused how crossing continental shelf break leads directly heat driven changes melting ice‐shelf cavity. In this study, we introduce regional ocean model configuration with static ice shelves. We evaluate...
Abstract. When subglacial meltwater is discharged into the ocean at grounding line, it acts as a source of buoyancy, enhancing flow speeds along ice base that result in higher basal melt rates. The effects discharge have been well studied context Greenland-like, vertical calving front, where Earth's rotation can be neglected. Here we study these Antarctic shelves, important. We use numerical model to simulate circulation and melting beneath an idealized three-dimensional shelf vary rate...
Retrogressive slumping could accelerate sea-level rise if ice-sheet retreat generates ice cliffs much taller than observed today. The tallest cliffs, which extend roughly 100 m above sea level, calve only after ice-flow processes thin the to near flotation. Above some ice-cliff height limit, stress state in will satisfy material-failure criterion, resulting faster brittle failure. New terrestrial radar data from Helheim Glacier, Greenland, suggest that subaerial are prone failure by...
Iceberg calving is a major contributor to Greenland's ice mass loss. Pro-glacial mélange (a mixture of sea ice, icebergs, and snow) may be tightly packed in the long, narrow fjords that front many marine-terminating glaciers can reduce by buttressing. However, data limitations have hampered quantitative understanding. We develop new radar-based approach estimate time-varying elevations near mélange-glacier interface, generating factor three or more improvement elevation precision. apply...
Abstract A phase‐sensitive radar (ApRES) was deployed on Totten Ice Shelf to provide the first in situ basal melt estimate at this dynamic East Antarctic ice shelf. Observations of internal dynamics tidal time scales showed that early arrivals from off‐nadir reflectors obscure true depth shelf base. Using observed deformation, base found lie 1,910–1,950‐m depth, 350–400 m greater range than reflection an ice‐ocean interface. The robustness rate increased by using multiple reflections over...
Abstract Totten Glacier is a fast‐moving East Antarctic outlet with the potential for significant future sea‐level contributions. We deployed four autonomous phase‐sensitive radars on its ice shelf to monitor ice‐ocean interactions near grounding zone and made active source seismic observations constrain gravity‐derived bathymetry models. observe an asymmetry in basal melting mean melt rates along differing by up 20 m/a. Our new model reveals that this rate coincides water column thickness...
Abstract Fourteen phase‐sensitive radars (ApRES) were deployed on the Filchner‐Ronne Ice Shelf (FRIS) to measure variability in its basal melt rate. Melt rates from sites along Ronne Depression vary seasonally, consistent with dynamics of propagation seasonal dense water western ice front into cavity. Several at back FRIS cavity feature a signal two maxima. Sub‐ice shelf oceanographic data available one indicate that this is caused by different pathways followed same source water....
Abstract. Continuous moored time series of temperature, salinity, pressure and current speed direction are great importance for understanding the continental shelf under-ice-shelf dynamics thermodynamics that govern water mass transformations ice melting in around Antarctic marginal seas. In these regions, icebergs sea make ship-based mooring deployment recovery challenging. Nevertheless, over decades, expeditions fringe Antarctica sporadically deployed recovered hundreds instruments,...
Abstract Basal melting of ice shelves is fundamental to Antarctic sheet mass loss, yet direct observations remain sparse. We present the first year‐round melt record (2017–2021) from a phase‐sensitive radar on Fimbulisen, one fastest flowing in Dronning Maud Land, East Antarctica. The observed long‐term mean ablation rate at 350 m depth below central shelf was 1.0 ± 0.5 yr −1 , marked by substantial sub‐weekly variability ranging 0.4 3.5 . 36‐h filtered basal fluctuations closely align with...
Subglacial discharge beneath ice shelves is a source of freshwater, and therefore buoyancy, at the grounding line. Being released depth, it accelerates an ascending plume along ice-shelf base, enhancing entrainment ambient waters, increasing melt rates. By now understood that subglacial key control on rate variability majority Greenland's glaciers. However, its importance in present-day future Antarctic rates less clear. To address this point, we use Energy Exascale Earth System Model (E3SM)...
Representing ice-shelf and ocean interactions in Earth system models (ESMs) has been challenging due to their coarse resolution static ice shelf cavity geometries. Additionally, coupling techniques often struggle conserve mass energy across components. We have recently implemented new algorithms the component of Energy Exascale System Model enable dynamic ice-ocean within Antarctica’s cavities. These include a thin subglacial film below grounded ice, runoff into cavities,...
The Filchner‐Ronne Ice Shelf experiences strong tidal forcing known to displace portions of the ice shelf by several meters over a cycle. These large periodic displacements may cause significant variation vertical strain. Further, currents in cavity be responsible for basal melt variations. We deployed autonomous phase‐sensitive radio‐echo sounders at 17 locations across and measured motion internal sufficiently short intervals allow resolution all constituents. Basal estimates with this...
Calving of glacial ice into the ocean from Greenland Ice Sheet is an important component global sea level rise. The calving process itself relatively poorly observed, understood, and modeled; as such, it represents a bottleneck in improving future estimates climate models. We organized pilot project to observe at Helheim Glacier East effort better understand it. During intensive one-week survey, we deployed suite instrumentation including terrestrial radar interferometer, GPS receivers,...
Basal melting of ice shelves is fundamental to Antarctic Ice Sheet mass loss, yet direct observations are sparse. We present the first melt record (2017 2021) from a phase-sensitive radar at Fimbulisen, East Antarctica, one fastest flowing in Dronning Maud Land. The observed long-term mean ablation below central part shelf was 1.0 ±0.4 m yr, marked by substantial sub-weekly variability ranging 0.3 3.8 yr. 36-h filtered fluctuations basal exhibit close alignment with ocean velocity, revealing...
Abstract The interior dynamics of Helheim Glacier were monitored using an autonomous phase‐sensitive radio‐echo sounder (ApRES) during two consecutive summers. return signals from all observational sites exhibited strong non‐tidal, depth‐dependent diurnal variations. We show that these variations in the glacier can be explained by englacial meltwater cycle: a data interpretation assumes constant ice‐column composition through time leads to dynamical inconsistencies with concurrent...
Abstract In‐situ phase‐sensitive radar measurements from the Ronne Ice Shelf (RIS) reveal evidence of intermittent basal accretion periods at several sites that are melting in long‐term mean. Periods when ice is accreted ice‐shelf base coincide with a decrease amplitude return up to 4 dB. To quantify we constrain simultaneously dielectric constant, electrical conductivity, and thickness ice. We do this by exploring sensitivity received echo strength phase different transmit frequencies using...
Abstract The ice mélange, a mixture of sea and icebergs, often present in front outlet glaciers Greenland or shelves Antarctica, can have profound effect on the dynamics ice‐ocean system. current inability to numerically model mélange motivates new modeling approach proposed here. A continuum sea‐ice is taken as starting point icebergs are represented thick compact pieces held together by large tensile shear strength, selectively introduced into rheology. In order modify rheology correctly,...
Abstract When glaciers calve icebergs, a fraction of the released potential energy is radiated away via gravity waves. The characteristics such waves, caused by iceberg calving on Helheim Glacier in east Greenland, are investigated. Observations were collected from an array five high-frequency bottom pressure meters placed along Sermilik Fjord. Calving-generated tsunami waves identified and used to construct event catalog. Calving events observed cluster around high low semidiurnal tides...
Abstract Ocean-driven melt of Antarctic ice shelves is an important control on mass loss from the sheet, but complex to study due significant variability in rates both spatially and temporally. Here we assess strengths weakness satellite field-based observations as tools for testing models ice-shelf melt. We discuss how complementary use field, model data can be a powerful underutilised tool studying processes. Finally, identify some community initiatives working collate publish coordinated...
Abstract Several autonomous phase-sensitive radio-echo sounders (ApRES) were deployed at Greenland glaciers to investigate ice deformation. Different attenuation settings tested and it was observed that, in the presence of clipping deramped ApRES signal, each setting produced a different result. Specifically, higher levels associated with lower an apparent linear increase diurnal vertical cumulative displacement depth, obscured visibility basal reflector return amplitude. An example...
Abstract Numerical modeling of ice sheet motion and hence projections global sea level rise require information about the evolving subglacial environment, which unfortunately remains largely unknown due to its difficulty access. Here we advance such observations by reporting multi‐year seismic tremor likely associated with glacier sliding at Helheim Glacier. This association is confirmed correlation analysis between power multiple environmental forcings on different timescales. Variations...
Subglacial runoff beneath ice shelves is a source of freshwater, and therefore buoyancy, at the grounding line. Being released depth, it accelerates an ascending plume along ice-shelf base, enhancing entrainment ambient waters, increasing melt rates. By now understood that subglacial key control on rate variability majority Greenland's glaciers. However, its importance in present-day future Antarctic rates less clear. To address this point, we use Energy Exascale Earth System Model (E3SM)...
To date, few Earth System Models (ESMs) have the ability to simulate flow in ocean cavities below Antarctic ice shelves and its influence on basal melting.  Yet capturing both this resulting melt patterns is critical for representing local, regional, global feedbacks between climate sub-ice-shelf Here, we present a small ensemble of historical simulations SSP3-7.0 projections an ESM that includes ice-shelf cavities, Energy Exascale Model (E3SM) v2.1.  The active ocean,...