Effects of Climate Change on CO₂ Concentration and Efflux in a Humic Boreal Lake: A Modeling Study

Abstract

Climate change may have notable impacts on carbon cycling in freshwater ecosystems, especially in the boreal zone. Higher atmospheric temperature and changes in annual discharge patterns and carbon loading from the catchment affect the thermal and biogeochemical conditions in a lake. We developed an extension of a one-dimensional process-based lake model MyLake for simulating carbon dioxide (CO 2 ) dynamics of a boreal lake. We calibrated the model for Lake Kuivajärvi, a small humic boreal lake, for the years 2013-2014, using the extensive data available on carbon inflow and concentrations of water column CO 2 and dissolved organic carbon. The lake is a constant source of CO 2 to the atmosphere in the present climate. We studied the potential effects of climate change-induced warming on lake CO 2 concentration and air-water flux using downscaled air temperature data from three recent-generation global climate models with two alternative representative concentration pathway forcing scenarios. Literature estimates were used for climate change impacts on the lake inflow. The scenario simulations showed a 20-35% increase in the CO 2 flux from the lake to the atmosphere in the scenario period 2070-2099 compared to the control period 1980-2009. In addition, we estimated possible implications of different changes in terrestrial inorganic and organic carbon loadings to the lake. The scenarios with plausible increases of 10% and 20% in CO 2 and dissolved organic carbon loadings, respectively, produced increases of 2.1-2.5% and 2.2-2.3% in the annual CO 2 flux.Boreal inland waters must be considered in assessing the effects of climate change on global carbon cycle because of their significant role in carbon cycling (Battin et al., 2009;Downing et al., 2006). Air temperature KIURU ET AL.2212

Coupling Water Column and Sediment Biogeochemical Dynamics: Modeling Internal Phosphorus Loading, Climate Change Responses, and Mitigation Measures in Lake Vansjø, Norway

“…We further showcase the use of the model to assess a management practice aimed at reducing internal P loads via the addition of reactive Fe to the water column. 2015) and C (de Wit et al, 2018;Kiuru et al, 2018), as well as reactions of N, Fe, Al, Ca, and S, were similarly coupled between sediment and water column (Figure 1; Tables 1 and 2).…”

“…In the current study, the existing physical hydrodynamic, ice, and snow cover modules of MyLake were used, and the P‐phytoplankton module was reformulated for direct coupling to the reaction network in the sediment. Biogeochemical reactions involving O (Couture et al, ) and C (de Wit et al, ; Kiuru et al, ), as well as reactions of N, Fe, Al, Ca, and S, were similarly coupled between sediment and water column (Figure ; Tables and ).…”

“…Here, we build upon two existing Matlab‐based models: MyLake, which focuses on the reactions of P (Saloranta & Andersen, ), oxygen (O; Couture et al, ), and carbon (C; de Wit et al, ; Kiuru et al, ), and Matsedlab, which focuses on the reactions of O, C, iron (Fe; Couture, Gobeil, et al, ), sulphur (S; Couture et al, ), and nitrogen (N; Akbarzadeh et al, ). In order to couple the two individual models into the 1.5‐D Lake‐Sediment model, we merged their reactions networks.…”

CH4 oxidation in a boreal lake during the development of hypolimnetic hypoxia

“…In the future, as the aquatic systems in the boreal zone are exposed to increasing terrestrial organic C load due to climate-induced changes in precipitation and air temperature (Lepistö et al 2008;Sarkkola et al 2009;Couture et al 2012;Kiuru et al 2018), the accelerated decomposition of OM might emphasize the role of alternative inorganic EAs in CH 4 oxidation. The development of summer stratification, on the other hand, suggests that the annual CH 4 emissions will remain largely regulated by aerobic CH 4 consumption due to the well-oxygenated water column throughout the summer.…”

Applicability and consequences of the integration of alternative models for CO<sub>2</sub> transfer velocity into a process-based lake model

“…The estimation of the flux footprint distribution functions was made using the model by Kormann and Meixner (2001). The average footprint contributing to 80 % of the fluxes varies from 100 up to about 300 m from the measurement platform depending on atmospheric stability conditions as described in Mammarella et al (2015).…”