A novel method for estimating the onset of thermal stratification in lakes from surface water measurements

Woolway, R. Iestyn; Maberly, Stephen C.; Jones, Ian D.; Feuchtmayr, Heidrun

doi:10.1002/2013wr014975

Cited by 46 publications

(33 citation statements)

References 41 publications

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“…In this study, the lake was considered stratified when the difference between surface temperature and bottom temperature ( T ) was greater than 1 • C (Woolway et al, 2014). The onset of stratification was considered to be the first day of the first period of 4 or more consecutive days in which T > 1 • C (Yang et al, 2016), and, in general, stratification events shorter than 4 d were also not considered when estimating duration and loss of stratification.…”

Section: Calibration Interval Model Statistics Valuementioning

confidence: 99%

Historical modelling of changes in Lake Erken thermal conditions

Moras

Ayala

Pierson

2019

Hydrol. Earth Syst. Sci.

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Abstract. Historical lake water temperature records are a valuable source of information to assess the influence of climate change on lake thermal structure. However, in most cases such records span a short period of time and/or are incomplete, providing a less credible assessment of change. In this study, the hydrodynamic GOTM (General Ocean Turbulence Model, a hydrodynamic model configured in lake mode) was used to reconstruct daily profiles of water temperature in Lake Erken (Sweden) over the period 1961–2017 using seven climatic parameters as forcing data: wind speed (WS), air temperature (Air T), atmospheric pressure (Air P), relative humidity (RH), cloud cover (CC), precipitation (DP), and shortwave radiation (SWR). The model was calibrated against observed water temperature data collected during the study interval, and the calibrated model revealed a good match between modelled and observed temperature (RMSE =1.089 ∘C). From the long-term simulations of water temperature, this study focused on detecting possible trends in water temperature over the entire study interval 1961–2017 and in the sub-intervals 1961–1988 and 1989–2017, since an abrupt change in air temperature was detected in 1988. The analysis of the simulated temperature showed that epilimnetic temperature increased on average by 0.444 and 0.792 ∘C per decade in spring and autumn in the sub-interval 1989–2017. Summer epilimnetic temperature increased by 0.351 ∘C per decade over the entire interval 1961–2017. Hypolimnetic temperature increased significantly in spring over the entire interval 1961–2017, by 0.148 and by 0.816 ∘C per decade in autumn in the sub-interval 1989–2016. Whole-lake temperature showed a significant increasing trend in the sub-interval 1989–2017 during spring (0.404 ∘C per decade) and autumn (0.789 ∘C per decade, interval 1989–2016), while a significant trend was detected in summer over the entire study interval 1961–2017 (0.239 ∘C per decade). Moreover, this study showed that changes in the phenology of thermal stratification have occurred over the 57-year period of study. Since 1961, the stability of stratification (Schmidt stability) has increased by 5.365 J m−2 per decade. The duration of thermal stratification has increased by 7.297 d per decade, corresponding to an earlier onset of stratification of ∼16 d and to a delay of stratification termination of ∼26 d. The average thermocline depth during stratification became shallower by ∼1.345 m, and surface-bottom temperature difference increased over time by 0.249 ∘C per decade. The creation of a daily time step water temperature dataset not only provided evidence of changes in Erken thermal structure over the last decades, but is also a valuable resource of information that can help in future research on the ecology of Lake Erken. The use of readily available meteorological data to reconstruct Lake Erken's past water temperature is shown to be a useful method to evaluate long-term changes in lake thermal structure, and it is a method that can be extended to other lakes.

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Section: Calibration Interval Model Statistics Valuementioning

confidence: 99%

Historical modelling of changes in Lake Erken thermal conditions

Moras

Ayala

Pierson

2019

Hydrol. Earth Syst. Sci.

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“…These model results were then compared to those produced from the first sensitivity analysis (i.e., using the 1982 data as a constant annual cycle) for validation. Though vertical temperature differences are often used to define stratification (Stefan et al 1996;Woolway et al 2014), stratification is the result of the associated density differences and these vary non-linearly with temperatures. Thus, at 5°C, a 1°C temperature difference is equivalent to less than a 0.025 kg m −3 density difference, while at 19°C a 1°C temperature difference represents more than a 0.2 kg m −3 density difference.…”

Section: Mylake Experimentsmentioning

confidence: 99%

Atmospheric stilling leads to prolonged thermal stratification in a large shallow polymictic lake

et al. 2017

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To quantify the effects of recent and potential future decreases in surface wind speeds on lake thermal stratification, we apply the one-dimensional process-based model MyLake to a large, shallow, polymictic lake, Võrtsjärv. The model is validated for a 3-year period and run separately for 28 years using long-term daily atmospheric forcing data from a nearby meteorological station. Model simulations show exceptionally good agreement with observed surface and bottom water temperatures during the 3-year period. Similarly, simulated surface water temperatures for 28 years show remarkably good agreement with long-term in situ water temperatures. Sensitivity analysis demonstrates that decreasing wind speeds has resulted in substantial changes in stratification dynamics since 1982, while increasing air temperatures during the same period had a negligible effect. Atmospheric stilling is a phenomenon observed globally, and in addition to recent increases in surface air temperature, needs to be considered when evaluating the influence of climate change on lake ecosystems.

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“…Additionally, the model's representation of stratification was evaluated based on the rate of false absence and false presence compared to observations. Lakes were considered stratified when the difference between surface and bottom water temperatures exceeded 1 • C (Stefan et al, 1996;Woolway et al, 2014).…”

Section: Model Post-processingmentioning

confidence: 99%

Simulating 2368 temperate lakes reveals weak coherence in stratification phenology

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Winslow

Hansen

et al. 2014

Ecological Modelling

118

116

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a b s t r a c tChanges in water temperatures resulting from climate warming can alter the structure and function of aquatic ecosystems. Lake-specific physical characteristics may play a role in mediating individual lake responses to climate. Past mechanistic studies of lake-climate interactions have simulated generic lake classes at large spatial scales or performed detailed analyses of small numbers of real lakes. Understanding the diversity of lake responses to climate change across landscapes requires a hybrid approach that couples site-specific lake characteristics with broad-scale environmental drivers. This study provides a substantial advancement in lake ecosystem modeling by combining open-source tools with freely available continental-scale data to mechanistically model daily temperatures for 2368 Wisconsin lakes over three decades . The model accurately predicted observed surface layer temperatures (RMSE: 1.74 • C) and the presence/absence of stratification (81.1% agreement). Among-lake coherence was strong for surface temperatures and weak for the timing of stratification, suggesting individual lake characteristics mediate some -but not all -ecologically relevant lake responses to climate.Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).

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A novel method for estimating the onset of thermal stratification in lakes from surface water measurements

Cited by 46 publications

References 41 publications

Historical modelling of changes in Lake Erken thermal conditions

Historical modelling of changes in Lake Erken thermal conditions

Atmospheric stilling leads to prolonged thermal stratification in a large shallow polymictic lake

Simulating 2368 temperate lakes reveals weak coherence in stratification phenology

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