Understanding the performance of the FLake model over two African Great Lakes

Thiery, Wim; Martynov, Andrey; Darchambeau, François; Descy, Jean-Pierre; Plisnier, Pierre‐Denis; Sushama, Laxmi; Lipzig, Nicole Van

doi:10.5194/gmd-7-317-2014

Cited by 89 publications

(74 citation statements)

References 43 publications

(46 reference statements)

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“…It was found that there is only a little sensitivity to modifications in this parameter for Lake Erie. The same result was found for Lake Kivu in Thiery et al (2014). The bottom sediments module was switched off in all simulations and the zero bottom heat flux condition was adopted.…”

Section: Flake Model and Configurationmentioning

confidence: 56%

“…The same parametric concept is applied for the ice and snow layers, using linear shape functions . The mixed layer depth is calculated considering the effects of both convective and mechanical mixing, also accounting for volumetric heating which is through the absorption of net shortwave radiation (Thiery et al, 2014). The non-reflected shortwave radiation is absorbed after penetrating the water column in accordance with the Beer-Lambert law (Gordon, 1989).…”

Section: Flake Model and Configurationmentioning

confidence: 99%

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Satellite-derived light extinction coefficient and its impact on thermal structure simulations in a 1-D lake model

Zolfaghari

Duguay

Pour

2017

Hydrol. Earth Syst. Sci.

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Abstract.A global constant value of the extinction coefficient (K d ) is usually specified in lake models to parameterize water clarity. This study aimed to improve the performance of the 1-D freshwater lake (FLake) model using satellite-derived K d for Lake Erie. The CoastColour algorithm was applied to MERIS satellite imagery to estimate K d . The constant (0.2 m −1 ) and satellite-derived K d values as well as radiation fluxes and meteorological station observations were then used to run FLake for a meteorological station on Lake Erie. Results improved compared to using the constant K d value (0.2 m −1 ). No significant improvement was found in FLake-simulated lake surface water temperature (LSWT) when K d variations in time were considered using a monthly average. Therefore, results suggest that a timeindependent, lake-specific, and constant satellite-derived K d value can reproduce LSWT with sufficient accuracy for the Lake Erie station.A sensitivity analysis was also performed to assess the impact of various K d values on the simulation outputs. Results show that FLake is sensitive to variations in K d to estimate the thermal structure of Lake Erie. Dark waters result in warmer spring and colder fall temperatures compared to clear waters. Dark waters always produce colder mean water column temperature (MWCT) and lake bottom water temperature (LBWT), shallower mixed layer depth (MLD), longer ice cover duration, and thicker ice. The sensitivity of FLake to K d variations was more pronounced in the simulation of MWCT, LBWT, and MLD. The model was particularly sensitive to K d values below 0.5 m −1 . This is the first study to assess the value of integrating K d from the satellite-based CoastColour algorithm into the FLake model. Satellite-derived K d is found to be a useful input parameter for simulations with FLake and possibly other lake models, and it has potential for applicability to other lakes where K d is not commonly measured.

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Section: Flake Model and Configurationmentioning

confidence: 56%

Section: Flake Model and Configurationmentioning

confidence: 99%

Satellite-derived light extinction coefficient and its impact on thermal structure simulations in a 1-D lake model

Zolfaghari

Duguay

Pour

2017

Hydrol. Earth Syst. Sci.

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“…Its vertical structure consists of an oxic and nutrient-poor mixed layer (seasonally variable depth, up to 70 m), and a permanently anoxic monimolimnion rich in dissolved gases (CH 4 , CO 2 ) and inorganic nutrients (Damas, 1937;Degens et al, 1973;Schmid et al, 2005). Seasonal variations of the vertical position of the oxycline are driven by contrasting hygrometry and long wave radiation between rainy (October-May) and dry (JuneSeptember) seasons (Thiery et al, 2014), the latter being characterized by a deepening of the oxic zone, and an increased input of dissolved gases and inorganic nutrients into the mixed layer , Borges et al, 2011. O 2 concentration was measured with a YSI-proODO probe with a optical O 2 sensor (detection limit is 3 µmol L −1 ), calibrated using air saturated water.…”

Section: Study Site Description and Samplingmentioning

confidence: 99%

Methanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)

Morana

Borges²,

Roland³

et al. 2015

Biogeosciences

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Abstract. The permanently stratified Lake Kivu is one of the largest freshwater reservoirs of dissolved methane (CH 4 ) on Earth. Yet CH 4 emissions from its surface to the atmosphere have been estimated to be 2 orders of magnitude lower than the CH 4 upward flux to the mixed layer, suggesting that microbial CH 4 oxidation is an important process within the water column. A combination of natural abundance stable carbon isotope analysis (δ 13 C) of several carbon pools and 13 CH 4 -labelling experiments was carried out during the rainy and dry season to quantify (i) the contribution of CH 4 -derived carbon to the biomass, (ii) methanotrophic bacterial production (MBP), and (iii) methanotrophic bacterial growth efficiency (MBGE), defined as the ratio between MBP and gross CH 4 oxidation. We also investigated the distribution and the δ 13 C of specific phospholipid fatty acids (PLFAs), used as biomarkers for aerobic methanotrophs. Maximal MBP rates were measured in the oxycline, suggesting that CH 4 oxidation was mainly driven by oxic processes. Moreover, our data revealed that methanotrophic organisms in the water column oxidized most of the upward flux of CH 4 , and that a significant amount of CH 4 -derived carbon was incorporated into the microbial biomass in the oxycline. The MBGE was variable (2-50 %) and negatively related to CH 4 : O 2 molar ratios. Thus, a comparatively smaller fraction of CH 4 -derived carbon was incorporated into the cellular biomass in deeper waters, at the bottom of the oxycline where oxygen was scarce. The aerobic methanotrophic community was clearly dominated by type I methanotrophs and no evidence was found for an active involvement of type II methanotrophs in CH 4 oxidation in Lake Kivu, based on fatty acids analyses. Vertically integrated over the water column, the MBP was equivalent to 16-60 % of the average phytoplankton particulate primary production. This relatively high magnitude of MBP, and the substantial contribution of CH 4 -derived carbon to the overall biomass in the oxycline, suggest that methanotrophic bacteria could potentially sustain a significant fraction of the pelagic food web in the deep, meromictic Lake Kivu.

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“…The highly parameterized model is designed for long-term calculations of lake thermodynamics at low computational costs and with minimum adjustment (Mironov 2008), and was successfully validated for a number of lakes with similar morphological characteristics (Kirillin 2010;Kirillin et al 2012Kirillin et al , 2013Thiery et al 2014). Data input includes the daily sunshine duration and daily means for temperature, wind speed, relative humidity, and cloud cover (data set available since 1951).…”

Section: Monitoring Of Lake Conditions Meteorological Data and Modelingmentioning

confidence: 99%

Effects of spring warming and mixing duration on diatom deposition in deep Tiefer See, NE Germany

et al. 2016

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Monitoring during three meteorologically different spring seasons in 2012, 2013, and 2014 revealed that temperature increase in spring, which influences spring lake mixing duration, markedly affected nutrient availability and diatom deposition in a sediment trap close to the bottom of deep Tiefer See, NE Germany. Deposition of Stephanodiscus taxa and small Cyclotella taxa was much higher after late ice out and a deep, short lake mixing period in spring 2013, compared to that after gradual warming and lengthy lake mixing periods in spring 2012 and 2014, when only brief or marginal ice cover occurred. Availability of dissolved Si and P was 33% and 20% higher, respectively, in 2013 compared to 2014. The observed relation between high (low) diatom deposition and short (lengthy) mixing duration in spring was applied to varved sediments deposited between AD 1924 and 2008. Low detrital Si content in trapped material and a sediment core enabled use of µXRF-counts of Si as a proxy for diatom silica. The spring mixing duration for 1951-2008 was derived from FLake-model calculations. The spring warming duration related to lake mixing was approximated from air temperatures for 1924-2008 using the dates when daily mean air temperature exceeded 5°C (start) and 10°C (end). Diatom silica deposition showed a significant (p<0.0001) inverse linear relationship with the modeled spring mixing duration (R² = 0.36) and the spring warming duration (R² = 0.28). In both cases, the relationship is strengthened when data from the period of low diatom production (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) is excluded (R² = 0.59 and R² = 0.35). Part of this low diatom production is related to external nutrient supply that favored growth of cyanobacteria at the expense of diatoms. This approach shows that diatom Si deposition was strongly influenced by the availability of light and nutrients, related to the duration of lake mixing and warming in spring, during most of the studied period. The remaining unexplained variability, however, indicates that additional factors influence Si deposition. Further tests in other deep, temperate lakes are necessary to verify if this relation is a common feature and consequently, if diatom Si can be used as a proxy for spring mixing duration in such lakes.

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Understanding the performance of the FLake model over two African Great Lakes

Cited by 89 publications

References 43 publications

Satellite-derived light extinction coefficient and its impact on thermal structure simulations in a 1-D lake model

Satellite-derived light extinction coefficient and its impact on thermal structure simulations in a 1-D lake model

Methanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)

Effects of spring warming and mixing duration on diatom deposition in deep Tiefer See, NE Germany

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