How will climate-induced changes in water level affect lake temperature and oxygen dynamics around the world?

Overview

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.
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 in evapotranspiration and precipitation, however, are predicted to be much larger than those in air temperature and be more variable across the globe. As a result, lake water levels will change substantially across the world. Changing water extraction practices will also severely impact lake water levels, exacerbating climate-induced changes. The combined impact of these pressures on lake water levels and how this affects the lake ecosystem is poorly understood, yet we need this information for the effective management of our lakes in the future.
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. Anoxia, in turn, has a detrimental effect on water quality, including promoting the internal release from lake sediment of key nutrients for algal growth. The impacts of water level change on lake temperatures, stratification, and depth of surface mixing, have, though, been little 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

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. Automated sensors for temperature, oxygen and depth will be deployed in two beautiful study sites, Airthrey Loch on the University of Stirling campus (Figure 1) and Elterwater, a small productive lake in the English Lake District. The student will additionally carry out a placement at the Centre for Ecology & Hydrology (Lancaster), one of the largest groups of lake scientists in the UK, to conduct a summer field campaign at Elterwater, collecting weekly samples of water quality data. These data will supplement existing historic datasets for Elterwater. The high resolution monitoring data 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 lakes. 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. There will also be opportunity to explore the use of data from satellites for examining recent global changes in lake water level.

Project Timeline

Year 1

Literature review; development of programming and numerical modelling skills; deployment of automated instrumentation in Airthrey Loch and Elterwater; field campaign in Elterwater (whilst based at CEH Lancaster)

Year 2

Numerical modelling study, and write-up, of temperature dynamics in Elterwater; development of statistical analysis skills; analysis, and write-up, of field data for Elterwater; UK conference attendance

Year 3

Numerical modelling study, and write-up, of oxygen dynamics in Elterwater and Airthrey Loch; investigation of water level changes from satellite data; 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 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 the University of Stirling and the IAPETUS DTP, including presentation skills and grant writing. In addition, the successful candidate will experience working both in a University department (Stirling) and at a Research Institute (CEH).

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.

Further Information

Please contact Dr Ian Jones (ian.jones@stir.ac.uk) for further details.

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