Description

Lakes form an important part of our landscape. They are valued as sources of economic revenue and as recreational areas. Lakes play a large role in the regulation of river water flow, thereby influencing downstream water quality and easing the impacts of both floods and droughts. Moreover, they supply water to agriculture and industry.
Climate change causes increased temperatures and more frequently occurring heatwaves both over land and in lakes in all parts of the globe [1]. Changes in precipitation patterns have are expected to cause more flooding in some regions, whereas other regions may experience longer or more intensive droughts [5]. This calls for appropriate adaptation measures, but the diverse uses of lake water by a multitude of stakeholders make the development of adaptation strategies a wicked problem.
This MSc topic is aimed at investigating the effects of one particular aspect of climate change --- increased lake heatwave frequency and intensity --- on the composition, and therefore the health, of lakes. We expect lake heatwaves to influence key physical and biological processes, but the large variability in lake size, depth, and composition, and the likely non-linearity of effects of temperature increase prohibits the generalization of findings [1]. This investigation therefore focuses on a single lake, or at most a handful of similar lakes. A good starting point for the investigation is Lake Victoria, one of Africa’s great lakes, as it is rather shallow: heatwaves are expected to be less intense in deeper lakes [2]. But the topic is open for other suggestions, provided the lake’s surface area is large compared to the satellite footprint, which is on the order of 1 km2.
A successful investigation of effects of lake heatwaves may be presented as a so-called use case for the Copernicus Global Land Service (https://land.copernicus.eu/global/use-cases).

Objectives and Methodology

As a consequence of global warming, lakes are warming up [1]. This is expressed by steadily increasing base temperatures, but also in increases in the frequency and intensity of lake heatwaves [2]. Land-based organisms may adapt to a changing climate by migrating to more suitable habitats, but this is usually not an option for lake-dwellers. Because many livelihoods depend on lake-based organisms, understanding the effects of lake heatwaves on lake composition is an important input to climate adaptation strategies.
The objectives of this study are: (a) identification of lakes suitable for the study and assessment of heatwave frequency and intensity; (b) investigation of heatwave effects on lake composition: chlorophyll amount, colored dissolved organic matter, turbidity; (c) evaluation of consequences to life in and near lakes. For the first two objectives, the student will make use of variables from the satellite-based data sets provided by ESA CCI-Lakes (https://climate.esa.int/en/projects/lakes/) and/or Copernicus Global Land Services (https://land.copernicus.eu/global/products/). For objective (b) the student will use the 2SeaColor model [4] to convert the water-leaving radiance into depth-dependent attenuation coefficient and water quality variables.

Further reading

[1] O’Reilly, C. M. et al. (2015) ‘Rapid and highly variable warming of lake surface waters around the globe’, Geophysical Research Letters, 42(24), p. 10,773-10,781. doi: 10.1002/2015GL066235.
[2] Woolway, R. I. et al. (2021) ‘Lake heatwaves under climate change’, Nature, 589(7842), pp. 402–407. doi: 10.1038/s41586-020-03119-1.
[3] Arabi, B. et al. (2020) ‘Integration of in-situ and multi-sensor satellite observations for long-term water quality monitoring in coastal areas’, Remote Sensing of Environment, 239, p. 111632. doi: 10.1016/j.rse.2020.111632.
[4] Salama, M.S. and Verhoef, W. (2015), ‘Two-stream remote sensing model for water quality mapping: 2SeaColor’, Remote Sensing of Environment, 157, p. 111-122. doi: 10.1016/j.rse.2014.07.022.
[5] Hartmann, D.L., et al. (2013) ‘Observations: Atmosphere and Surface’, In: ‘Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change’ [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.