Controls on short-term calving glacier dynamics

The global retreat and thinning of mountain glaciers and ice sheet margins is a well-documented consequence of recent climate changes, impacting both downstream hydrology and freshwater availability and eustatic sea-level rise. Alongside recent reductions in ice volume, proglacial lakes observed at the termini of many glaciers have increased in both number and areal extent (Shugar et al., 2020) as glacier overdeepenings become ice-free and fill with meltwater. The size and number of such lakes is projected to increase in future (Schomacker, 2010).

The presence of an ice-marginal lake has been observed to change the dynamics and behaviour of a glacier (e.g. Baurley et al., 2020) via a number of thermo-mechanical processes and positive feedbacks. While calving fluxes are mostly a function of ice velocity, the retreat of a glacier margin into progressively deeper water alters the longitudinal stress distribution of a glacier. Moreover, the lake itself can decouple glacier mass loss from climate forcing as heat absorption by the lake and seasonal fluctuations in water temperature, depth and circulation patterns influence the calving regime (Watson et al., 2020).

UAV flying in front of a glacier  Kayaks at a calving glacier front Boat in front of a glacier shon in overhead image

Remote sensing data indicates that the flow velocity and retreat of lake-terminating glaciers is substantially faster than nearby land-terminating glaciers (e.g. Kirkbride and Warren, 1997; Baurley et al., 2020). These changes provide an insight into ablation mechanisms at a local scale that have hitherto been poorly quantified in mass balance and surface energy models because of the difficulty of acquiring data at the necessary temporal and spatial scale. Indeed, despite these important contributions to overall glacier mass loss, there is a paucity of field data documenting and quantifying “frontal ablation” (including calving, subaqueous and subaerial frontal melt) of lake-terminating glaciers and ice sheets.

Advances in field sensors and monitoring/survey techniques, coupled with developments in remote sensing platforms (Taylor et al., 2021) have created a step-change in the quantity, quality and availability of data. Such advances have opened up new opportunities to better understand the rates, controls and mechanisms of glacier frontal ablation at a nested range of space and time scales (e.g. Mallalieu et al., 2020). These data are urgently needed to better represent lake-glacier interactions in numerical models of mountain glacier and ice sheet evolution (Carrivick et al., 2020).

The aim of this project is to constrain the short-term dynamics of glaciers calving into ice marginal lakes. An array of novel field monitoring techniques will be deployed as part of data acquisition. High resolution, short-term repeat Structure-from-Motion (SfM) glacier surveys will be undertaken from a packraft, boat or Uncrewed Aerial Vehicle (UAV) and differenced to provide information on calving volumes, timing and mechanisms. A weather station, trail cameras and networks of pressure sensors and thermistor strings will provide information on weather and lake conditions.

The final field site(s) will be chosen in discussion with any successful candidate. The project team have an established history and experience of working on these questions at a range of field sites including the Himalayas, West Greenland, Arctic Sweden and New Zealand. Owing to the logistical advantages and number of such proglacial lakes, we anticipate initial fieldwork to be conducted on outlet glaciers of the Vatnajökull Ice Cap, Iceland. Moreover, at this site there is the potential opportunity to examine the impact of large-scale additions of debris onto the glacier surface on the monitored relationships.

Objectives
(1) To intensely monitor glacier calving processes alongside environmental/lake data collection at one site for a season/year;
(2) To partition mass loss between surface melt and calving volumes at that site (or multiple sites nearby);
(3) To determine the controls on that mass loss partition from a wider light touch monitoring campaign/analyses of other data sources and analysis of the longer-term remote sensing data archive.

Fit to NERC Science
This project is aligned to the NERC ‘Terrestrial and freshwater environments’, ‘Geosciences’ and ‘Climate & climate change’ research areas. This project will contribute to the UK’s research ambitions to contribute to our understanding of how the planet works and predict how it will change, and to manage our presence responsibly.

Training
The successful student will work under the supervision of Dr Mark Smith, Prof Duncan Quincey and Dr Jonathan Carrivick (SoG) within the River Basin Dynamics and Management research cluster in the School of Geography, University of Leeds. The successful candidate will develop a range of research skills including field instrumentation, photogrammetry, GIS and Remote Sensing, python scripting, statistical analysis, data presentation, academic writing skills and giving presentations. Fieldwork is a core part of this project. Training will be provided in field health and safety procedures.

The student will be supported throughout the studentship by a comprehensive PGR skills training programme that follows the VITAE Research Development Framework and focuses on knowledge and intellectual abilities; personal effectiveness; research governance and organisation; and engagement, influence and impact. Training needs will be assessed at the beginning of the project and at key stages throughout the project and the student will be encouraged to participate in the numerous training and development course that are run within the NERC DTP and the University of Leeds to support PGR students, including statistics training (e.g. R, SPSS), academic writing skills, grant writing etc.. Supervision will involve regular meetings between supervisors and further support of a research support group.

Student profile
The student should have a keen interest in environmental issues with a strong background in a physical geography, earth sciences, environmental sciences, ecology or related discipline. Strong GIS/remote sensing/statistical/fieldwork skills are desirable but not essential, as training will be provided during the PhD.

References
Baurley, N.R., Robson, B.A. and Hart, J.K., 2020. Long‐term impact of the proglacial lake Jökulsárlón on the flow velocity and stability of Breiðamerkurjökull glacier, Iceland. Earth Surface Processes and Landforms, 45(11), pp.2647-2663.

Carrivick, J.L., Tweed, F.S., Sutherland, J.L. and Mallalieu, J., 2020. Toward numerical modeling of interactions between ice-marginal proglacial lakes and glaciers. Frontiers in Earth Science, 8, p.500.

Kirkbride, M. P., and Warren, C. R. (1997). Calving processes at a grounded ice cliff. Ann. Glaciol. 24, 116–121.

Mallalieu, J., Carrivick, J.L., Quincey, D.J. and Smith, M.W., 2020. Calving seasonality associated with melt‐undercutting and lake ice cover. Geophysical Research Letters, 47(8), p.e2019GL086561.

Schomacker A. 2010. Expansion of ice-marginal lakes at the Vatnajökull ice cap, Iceland, from 1999 to 2009. Geomorphology 119(3–4): 232–236.

Shugar, D. H., Burr, A., Haritashya, U. K., Kargel, J. S., Watson, C. S., Kennedy, M. C., et al. (2020). Rapid worldwide growth of glacial lakes since 1990. Nat. Clim. Chang. 10, 939–945.

Taylor, L.S., Quincey, D.J., Smith, M.W., Baumhoer, C.A., McMillan, M. and Mansell, D.T., 2021. Remote sensing of the mountain cryosphere: Current capabilities and future opportunities for research. Progress in Physical Geography: Earth and Environment, p.03091333211023690.

Watson, C. S., Kargel, J. S., Shugar, D. H., Haritashya, U. K., Schiassi, E., & Furfaro, R. (2020). Mass loss from calving in Himalayan proglacial lakes. Frontiers in Earth Science, 7.