IAP2-23-102

In hot water: How will climate-driven water level changes impact lakes?

Climate change is the dominant global environmental problem of our time, while lakes are sensitive sentinels of change (Williams et al. 2009). Nevertheless, our current understanding of climate change impacts on lakes is largely based on how atmospheric warming will lead to increased water temperatures and thermal stratification, and the consequences these changes will impose on the chemistry and biology in standing waters. Future changes and variation in evapotranspiration and precipitation, however, are predicted to disproportionately affect lakes and as a result, lake water levels will change substantially across the world. The impact of changes to lake water levels and how this affects the lake ecosystem is still poorly understood. This lack of understanding and evidence undermines our ability to manage effectively our lakes in the future.

This project will use a combined monitoring and numerical modelling approach to investigate how changes in water level will impact temperature and oxygen dynamics, two critical components of lake ecosystems, in standing water bodies across the globe. Water temperature has a huge influence on lake ecosystems as it is an important control on most biological and chemical rates and reactions. Similarly, the variation in temperature with depth – stratification – is of fundamental importance to the ecosystem, because it impacts rates of vertical mixing, particularly of oxygen, and hence influences whether bottom waters will become anoxic. The impacts of water level change on lake temperatures, stratification, and depth of surface mixing, are rarely investigated. This is despite the possible synergistic or antagonistic effects of a change in water level and a simultaneous increase in air temperature. Recent work has shown that even small, shallow lakes can experience complicated temperature and stratification changes on a daily basis (Anderson et al. 2017). Changes in water level could therefore affect temperature and stratification in a wide variety of standing water bodies. Ultimately, future variation in water level could have a profound influence on water quality worldwide. The impacts need to be understood in order to ascertain which lakes and regions are most at risk of a deterioration in water quality so that appropriate remediation measures can be employed.
This project will use a number of different approaches to develop understanding of this global issue. It will investigate the influence of lake shape and depth as well as the overlying climate region on the fundamental physical processes and use this understanding to predict how oxygen dynamics will be affected.

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Image Captions

Figure 1: Airthrey Loch on the University of Stirling campus

Methodology

This PhD will combine fieldwork, high resolution automated monitoring, and numerical modelling to study the impacts of changing water level on vertically resolved temperature and oxygen dynamics of lakes. As such, the project offers an exceptional training and development opportunity in a full range of techniques used in modern lake science. The project will involve fieldwork on Airthrey Loch on the University of Stirling campus (Figure 1) which will be supplemented by deployment of automated sensors for temperature, oxygen, and depth. The student will additionally visit the UK Centre for Ecology & Hydrology (Lancaster), one of the largest groups of lake scientists in the UK. At UKCEH the student will be able to utilise their historic long-term monitoring data for Blelham Tarn, a well-studied eutrophic lake with several decades of monitoring data. The data from the lakes will be used to calibrate and validate lake physics and lake oxygen models (for example, Burchard et al. 1999; Livingstone & Imboden, 1996). Modelling studies will explore the impacts of a wide range of water level change and air temperature change scenarios on stratification and bottom water deoxygenation in both Blelham Tarn and Airthrey Loch. Further modelling will then focus on the role of lake morphology, as one of the key determinants of net impact of water level change will be the rate of change of the surface area of the lake to the volume of the lake. The impact of geographical region – indicative of the background climate – will also be investigated to determine which types of lakes in which parts of the world will be most susceptible to reductions in water quality driven by changes in water level.

Project Timeline

Year 1

Literature review; development of programming and numerical modelling skills; deployment of automated instrumentation in Airthrey Loch; field campaign on Airthrey Loch; visit to UKCEH Lancaster to explore long-term data for Blelham Tarn.

Year 2

Further fieldwork in Airthrey Loch; numerical modelling study, and write-up, of temperature dynamics in Airthrey Loch; development of statistical analysis skills; analysis, and write-up, of field data for Airthrey Loch; visits to UKCEH; UK conference attendance.

Year 3

Numerical modelling study, and write-up, of oxygen dynamics in Blelham Tarn and Airthrey Loch; visits to UKCEH; complete study on global implications for lakes of different morphologies in different regions; overseas conference attendance.

Year 3.5

Completion of thesis write-up and submission.

Training
& Skills

The supervisory team are highly experienced in freshwater science and restoration ecology. The student will have access to a breadth of facilities at the UK Centre for Ecology and Hydrology and the University of Stirling (UoS) and be part of the inclusive and productive lab groups and PhD cohorts at these institutions. The successful candidate will receive wide-ranging interdisciplinary training to develop skills that will form the basis for a career in environmental science, for example, i) ‘R’ programming, ii) numerical modelling, iii) the use of automated sensors, iv) field sampling, v) limnology, vi) statistical analysis. Training courses on a variety of additional transferable skills will be available through UoS and the IAPETUS DTP, including presentation skills and grant writing. In addition, the successful candidate will experience working both in a university department (UoS) and at a Research Institute.

References & further reading

Anderson M. R., Sand-Jensen K., Woolway R. I. & Jones I. D. (2017) Profound daily vertical stratification and mixing in a small, shallow wind-exposed lake with submerged macrophytes. Aquatic Sciences, 79, 395–406.
Burchard H., Bolding K. & Ruiz-Villarreal M. (1999) GOTM, a general ocean turbulence model. Theory, implementation and test cases. Technical report, 103 pp.
Livingstone D. M. & Imboden D. M. (1996) The prediction of hypolimnetic oxygen profiles: A plea for a deductive approach. Canadian Journal of Fisheries and Aquatic Sciences, 53, 924–932.
Williamson C. E., Saros J. E. & Schindler D. W. (2009) Sentinels of Change. Science, 323, 887–888.

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