Research
I am a glaciologist interested in using satellite remote sensing, fieldwork, and numerical modelling to investigate hydrology-dynamic and ice-ocean interactions in the global cryosphere.
Ice discharge into the ocean (i.e. iceberg calving) is a key contributor to sea level rise, making up approximately half of sea level contribution from the Greenland Ice Sheet and representing a key future concern in the Antarctic Ice Sheet. Discharge can be accelerated or suppressed by the influence of surface meltwater as it drains through the ice sheet, as well as the thermal forcing from the ocean. However, our observations and understanding of the interactions between these processes are poor, making predicting the future losses from the ice sheets highly uncertain. A better understanding of future loss is essential when considering the enormous societal investment required to mitigate the effects of sea level rise on communities living in affected low-lying coastal regions, which could exceed 10% of the global population by the end of the 21st century.
I use a combination of methods - including satellite remote sensing, high resolution topographic data, ground-based geophysical methods, and numerical modelling - to monitor how glacial dynamics are changing and understand the reasons why, with the aim of better understanding how the ice sheet will continue to evolve in the 21st century and beyond.
Current Research Projects
How do crevasses transfer water to the bed of ice sheets?
2023-2026 | Leverhulme Trust
My current research fellowship aims to assess the influence of crevasse hydrology on the dynamics of the Greenland Ice Sheet (GrIS). Half of all meltwater is delivered to the bed of the GrIS via crevasses, and we are increasingly aware that crevasses can deliver water to the ice sheet in diverse ways, from slow and inefficient drainage via fracture networks through to discrete rapid drainage events. However, due to a paucity of observations on where, why, and how crevasses drain, these important processes have yet to be parameterised in ice sheet models, and the vast majority of hydrological models neglect to include crevasses at all.
Knowing where crevasses drain begins by knowing where crevasses are. I have developed a new workflow that takes advantage of high-resolution digital elevation models (DEMs) to generate large-scale, multitemporal 3D observations of crevasse geometry (image above). Using this technique, we have mapped crevasses across the whole of the Greenland Ice Sheet, showing for the first time how crevasses are evolving as the ice sheet accelerates in response to climate change. Alongside this project, I have released public Python tools for management of ArcticDEM and Reference Elevation Model of Antarctica (REMA) data, making large-scale DEM analysis more accessible for glaciologists and other polar scientists.
I am using deep learning approaches detect water-filled crevasses that are otherwise challenging to detect in medium-resolution Sentinel-2 imagery. This allows for temporally deep time stacks of crevasse drainage behaviour to be automatically extracted at regional scales. With these datasets, alongside public datasets of climate and ice dynamics, I am exploring the dynamic controls on crevasse hydrological behaviour. These controls will be parameterised within coupled models of ice sheet hydrology-dynamics in order to quantify the influence of crevasse hydrology on the future of the Greenland Ice Sheet.
Research Highlights
Rapid changes forced by ocean warming
Understanding the exact causes of glacier retreat is critical in order to properly project how the ice sheet will continue to change throughout the 21st century. During my postdocoral work at Ohio State University, I examined K.I.V Steenstrups Nordre Bræ (‘Steenstrups’) in Southeast Greenland, which, between 2018 and 2021, retreated ~7 km, thinned ~20%, doubled in discharge, and accelerated ~300%. This rate of change is unprecedented amongst Greenland’s glaciers and now places Steenstrups in the top 10% of glaciers by contribution to ice-sheet-wide discharge. Steenstrups appeared to retreat in response to a >2 °C anomaly in ocean-derived Atlantic water (AW), highlighting that even long-term stable glaciers with high sills are vulnerable to sudden and rapid retreat from warm AW intrusion.
See our paper in Nature Communications, and associated press release.
Lake drainage at a fast-flowing glacier
Supraglacial lake drainage is a critical component of Greenland's hydrological system, but all prior research examined drainages at slow-flowing, land-terminating glaciers. I used novel geophysical methods - including UAVs, GNSS, and seismometers - to examine the causes and consequences of a drainage at a fast-flowing Greenlandic outlet where ice moves in excess of 600 metres a year, finding unique processes occurring in this dynamic context.
See our paper in PNAS, and associated press release.
Controls on crevasse ponding
Surface crevasses transfer nearly half of all of Greenland's meltwater to the bed, yet when, where, and how this occurs is poorly understood. I used large-scale satellite analysis to assess the spatial variability of meltwater ponding across a fast-flowing sector of the Greenland Ice Sheet. Unlike supraglacial lakes, ponding cannot by explained by water collecting in surface basins. Instead, we find that ponded crevasses exist in regions of compressive surface stress, which closes pathways that elsewhere allow crevasses to drain into the wider surface hydrological system. Differing drainage processes in regions of compressive and extensional regimes may have distinct consequences for subglacial drainage and the heating of the ice sheet due to energy release during meltwater refreezing.
UAVs and Photogrammetry
Producing accurate georeferenced models from UAV photogrammetry is difficult in glaciological applications, where implementing ground control can be hazardous. In order to aid our work at Store Glacier in Greenland, I developed a low-cost, custom built unmanned system that utilised on-board GPS post-processing in order to produce accurate glacier velocity fields even on an inland ice sheet.
