Journal Article

Combining a Multi‐Lake Model Ensemble and a Multi‐Domain CORDEX Climate Data Ensemble for Assessing Climate Change Impacts on Lake Sevan

Shikhani, Muhammed, Boehrer, Bertram, Shatwell, Tom, Rinke, Karsten, Mi, Chenxi, Barfus, Klemens, Misakyan, Amalya, Feldbauer, Johannes, Ladwig, Robert, Moore, Tadhg N., Mercado‐Bettín, Daniel, Gevorgyan, Artur, Schultze, Martin

2024

Overview

Global warming is shifting the thermal dynamics of lakes, with resulting climatic variability heavily affecting their mixing dynamics. We present a dual ensemble workflow coupling climate models with lake models. We used a large set of simulations across multiple domains, multi‐scenario, and multi GCM‐ RCM combinations from CORDEX data. We forced a set of multiple hydrodynamic lake models by these multiple climate simulations to explore climate change impacts on lakes. We also quantified the contributions from the different models to the overall uncertainty. We employed this workflow to investigate the effects of climate change on Lake Sevan (Armenia). We predicted for the end of the 21st century, under RCP 8.5, a sharp increase in surface temperature (4.3±0.7K)$(4.3\\pm 0.7\\,\\mathrm{K})$and substantial bottom warming (1.7±0.7K)$(1.7\\pm 0.7\\,\\mathrm{K})$ , longer stratification periods (+55 days) and disappearance of ice cover leading to a shift in mixing regime. Increased insufficient cooling during warmer winters points to the vulnerability of Lake Sevan to climate change. Our workflow leverages the strengths of multiple models at several levels of the model chain to provide a more robust projection and at the same time a better uncertainty estimate that accounts for the contributions of the different model levels to overall uncertainty. Although for specific variables, for example, summer bottom temperature, single lake models may perform better, the full ensemble provides a robust estimate of thermal dynamics that has a high transferability so that our workflow can be a blueprint for climate impact studies in other systems. Plain Language Summary Lakes are threatened by climate change because of effects related to the increasing temperature, long stratification, and ice disappearance. One of the best tools to predict these effects on lakes is numerical modeling of lakes that benefit from climate modeling. Climate modeling is normally done globally or in the so‐called general circulation model (GCM) or more detailed simulations on regional levels (RCM) like the CORDEX data set. In this study, we used the CORDEX data, which employed several climate models from several regions (domains) for several climatic scenarios (emissions scenarios) to force multiple lake models. This approach gave us an extensive prediction about various possible outputs. We applied this approach to Lake Sevan (Armenia), a large mountain lake. Our study predicted for the worst‐case scenario, an increase of the surface temperature by almost 4.3 K by the end of the 21st century, 1.75 K for bottom temperature, a total disappearance of ice cover, and about 55 extra days of stratification, showing its vulnerability for climate change. This optimized workflow uses the strength of a wide variety of models on the climate and lake levels to better understand the impact of climate change and quantify the sources of uncertainty in the workflow. Key Points Dual multi‐model ensemble of climate data and lake models is used for robust projections of climate change impacts Variance decomposition effectively identified the sources of uncertainty and contributions of different models to the overall uncertainty Significant warming, longer stratification periods, and loss of ice cover are predicted for Lake Sevan by the end of the 21st century

• Publisher: John Wiley & Sons, Inc,John Wiley and Sons Inc,Wiley
• Subject: 21st century / Abrupt/Rapid Climate Change / Air/Sea Constituent Fluxes / Air/Sea Interactions / Armenia / Atmospheric / Atmospheric Composition and Structure / Atmospheric Effects / Atmospheric Processes / Avalanches / Benefit‐cost Analysis / Biogeosciences / Bottom temperature / Climate / Climate and Interannual Variability / Climate change / Climate Change and Variability / climate change impacts / Climate Dynamics / Climate effects / Climate Impact / Climate Impacts / Climate models / Climate prediction / Climate studies / Climate Variability / Climatic data / Climatology / Computational Geophysics / cooling / CORDEX / Cryosphere / Decadal Ocean Variability / Disaster Risk Analysis and Assessment / Earth System Modeling / Earthquake Ground Motions and Engineering Seismology / Effusive Volcanism / Environmental assessment / Environmental impact / Explosive Volcanism / General Circulation / General circulation models / Geodesy and Gravity / Geological / Global Change / Global Change from Geodesy / Global warming / Gravity and Isostasy / hydrodynamics / Hydrological Cycles and Budgets / Hydrology / Ice cover / Impacts of Global Change / Informatics / Lake effects / Lake levels / lake modeling / Lake models / LakeEnsemblR / Lakes / Land/Atmosphere Interactions / Limnology / Marine Geology and Geophysics / Mass Balance / Mathematical Geophysics / meteorological data / Modeling / Modelling / Mountain lakes / Mud Volcanism / multi model ensemble (MME) / Natural Hazards / Numerical Modeling / Numerical models / Numerical Solutions / Ocean influence of Earth rotation / Ocean Monitoring with Geodetic Techniques / Ocean/Atmosphere Interactions / Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions / Oceanic / Oceanography: General / Oceanography: Physical / Oceans / Paleoceanography / Physical Modeling / Policy Sciences / Predictions / Radio Oceanography / Radio Science / Regional Climate Change / Regional Modeling / Risk / Robustness / Sea Level Change / Sea Level: Variations and Mean / Seismology / Simulation / Solid Earth / Stratification / summer / Surface temperature / Surface Waves and Tides / Theoretical Modeling / Tsunamis and Storm Surges / Uncertainty / Uncertainty Assessment / Uncertainty Quantification / variance decomposition / Volcanic Effects / Volcanic Hazards and Risks / Volcano Monitoring / Volcano Seismology / Volcano/Climate Interactions / Volcanology / water / Water Cycles / Workflow