Proglacial lakes and their impact on Himalayan glacier evolution

The vast majority of mountain glaciers have been losing mass since at least the early part of the 20th Century, and have been in a particularly marked period of recession in recent decades1,2. The clearest visual evidence of this ice recession is the presence of many thousands of glacial lakes, ubiquitous in all major glacierised regions of the world, formed as meltwater occupies glacially carved basins and the voids that now exist behind moraine dams3. These proglacial lakes represent critical natural reservoirs that can be utilised to sustain river flows during the dry season and generate hydro-electric power for urban areas; however, many also represent a growing concern because they pose an outburst flood risk to downstream communities4. Recent work has also shown that they can have a profound impact on glacier mass balance, accelerating ice loss when compared to their land-terminating counterparts5,6.

The presence of a proglacial lake can enhance ablation through three key mechanisms: via subaqueous thermal erosion, by promoting glacier calving7, and by ice acceleration (or drawdown)8. The rates at which each of these processes contributes to enhanced mass loss are only loosely constrained at present9, meaning the current impact of lake formation on glacier mass balance is uncertain. Even less is known about how, and where, future lakes will contribute to patterns of glacier evolution, to the extent that they remain largely ignored in numerical simulations of future cryospheric change. This PhD project will seek to close each of these major knowledge gaps.

The project will assess recent and future changes in mountain glacier environments, focussing on the Himalaya, with the aim of establishing the empirical data required to formulate relationships between lake characteristics (area, volume, depth) and glacier response to climate change. This will require a systematic review of existing data within the literature, and the derivation of new remotely sensed datasets from both optical and SAR-based sources, and if appropriate, historical aerial photography. There will be the opportunity to develop skills in automatic classification (e.g. Google Earth Engine), glacier velocity derivation (e.g. Cosi-CORR10, GAMMA), statistical analysis (R Studio) and geodetic mass balance calculation (e.g. Imagine Photogrammetry). Analysis of future lake development will require estimates of ice thickness to be made (using, for example, the GlabTop model11). The final step will be to further develop the student’s glacier modelling training by incorporating these analyses into ice-flow models (e.g. iSOSIA12) being developed by the supervisory team, to make experiments as a first step towards explicitly including lake-ice interactions in simulations of future glacier change.

Depending on the interests and skills of the successful applicant, there will be exciting opportunities to visit remote field sites, to ground-truth interpretations of satellite data and to collect in-situ measurements of key lake parameters. The student will also be encouraged to build collaborations with the broad group of international experts working in this topical area.

Objectives

This project will use a combination of remote sensing techniques at a range of scales, and numerical modelling, to study recent changes in Himalayan glaciers and their implications for future cryospheric evolution. More specifically, the project will address the following objectives:

  1. To quantify current and recent changes in mountain glacier mass balance, brought about by processes of subaqueous melt, ice calving, and ice acceleration, following proglacial lake development.
  2. To simulate future ice-free environments using contemporary ice-thickness and DEM data, establish the likely locations of lake development, and estimate the likely timing of lake emergence in line with ice recession.
  3. To establish and incorporate the model parameterisation necessary to simulate the impacts of emerging/new glacial lakes on current/future glacier mass balances.

Potential for high impact outcome

The project will contribute to one of the most pressing environmental issues of our time – the response of the cryosphere, and all of the services it offers by way of freshwater storage, climate feedbacks and habitat provision, to recent and ongoing climate change. The research has been designed so that each of the objectives (above) will lead directly to an important, high-profile journal article that the student will lead. The student will be guided in this endeavour and all other aspects of the project by the supervisors, who have a track record of publishing in some of the world’s most prestigious scientific journals, and who have pioneered relevant methods in the geosciences.

Training

The student will work under the supervision of Prof. Duncan Quincey and Dr. Jonathan Carrivick in the School of Geography, where they will become a member of the River Basins Processes and Management research cluster. Drs Ann Rowan and Simon Cook will provide relevant expertise in numerical modelling and glacial lake analysis, respectively. The project will provide the student with high-level training in (i) mountain glaciology; (ii) state-of-the-art remote sensing techniques; (iii) numerical modelling of glacier evolution; and (iv) advanced data analysis skills. The student will be supported throughout by a comprehensive postgraduate 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 student will be encouraged to participate in the numerous training and development courses that are run within the university to support postgraduate students, including statistics training (e.g. R, SPSS), academic writing, grant writing, and other relevant skills (see http://www.emeskillstraining.leeds.ac.uk/). Supervision will involve regular meetings between all supervisors, while an independent Research Support Group will provide the student with external guidance at regular intervals throughout their studies.

Student profile

The student should have a keen interest in contemporary environmental change, demonstrable research skills in remote sensing and GIS techniques, and a strong background in physical geography, earth sciences, environmental sciences or a related discipline.  Some experience of research into cryospheric systems, and glaciers in particular, is also desirable but not essential.

References

  1. Wouters, B., Gardner, A.S. and Moholdt, G., 2019. Global glacier mass loss during the GRACE satellite mission (2002-2016). Frontiers in earth science, 7, p.96.
  2. Maurer, J.M., Schaefer, J.M., Rupper, S. and Corley, A., 2019. Acceleration of ice loss across the Himalayas over the past 40 years. Science advances, 5(6), p.eaav7266.
  3. Shugar, D.H., Burr, A., Haritashya, U.K., Kargel, J.S., Watson, C.S., Kennedy, M.C., Bevington, A.R., Betts, R.A., Harrison, S. and Strattman, K., 2020. Rapid worldwide growth of glacial lakes since 1990. Nature Climate Change, pp.1-7.
  4. Carrivick, J.L. and Tweed, F.S., 2016. A global assessment of the societal impacts of glacier outburst floods. Global and Planetary Change, 144, pp.1-16.
  5. King, O., Bhattacharya, A., Bhambri, R. and Bolch, T., 2019. Glacial lakes exacerbate Himalayan glacier mass loss. Scientific Reports, 9(1), pp.1-9.
  6. King, O., Dehecq, A., Quincey, D. and Carrivick, J., 2018. Contrasting geometric and dynamic evolution of lake and land-terminating glaciers in the central Himalaya. Global and Planetary Change, 167, pp.46-60.
  7. Watson, C.S., Kargel, J.S., Shugar, D.H., Haritashya, U.K., Schiassi, E. and Furfaro, R., 2020. Mass loss from calving in Himalayan proglacial lakes. Frontiers in Earth Science, 7.
  8. Liu, Q., Mayer, C., Wang, X., Nie, Y., Wu, K., Wei, J. and Liu, S., 2020. Interannual flow dynamics driven by frontal retreat of a lake-terminating glacier in the Chinese Central Himalaya. Earth and Planetary Science Letters, 546, p.116450.
  9. Song, C., Sheng, Y., Wang, J., Ke, L., Madson, A. and Nie, Y., 2017. Heterogeneous glacial lake changes and links of lake expansions to the rapid thinning of adjacent glacier termini in the Himalayas. Geomorphology, 280, pp.30-38.
  10. Leprince, S., Ayoub, F., Klinger, Y. and Avouac, J.P., 2007, July. Co-registration of optically sensed images and correlation (COSI-Corr): An operational methodology for ground deformation measurements. In 2007 IEEE International Geoscience and Remote Sensing Symposium (pp. 1943-1946). IEEE.
  11. Linsbauer, A., Frey, H., Haeberli, W., Machguth, H., Azam, M.F. and Allen, S., 2016. Modelling glacier-bed overdeepenings and possible future lakes for the glaciers in the Himalaya—Karakoram region. Annals of Glaciology, 57(71), pp.119-130.
  12. Egholm, D.L., Pedersen, V.K., Knudsen, M.F. and Larsen, N.K., 2012. On the importance of higher order ice dynamics for glacial landscape evolution. Geomorphology, 141, pp.67-80.