1Vrije Universiteit Brussel, Department of Hydrology and Hydraulic Engineering, 1050 Brussels, Belgium
2Institute for Marine and Atmospheric Research, Utrecht University, Princetonplein 5, 3584 CC Utrecht, the Netherlands
3Université Catholique de Louvain, Institute of Mechanics, Materials and Civil Engineering (IMMC), 1348 Louvain-la-Neuve, Belgium
4Université Catholique de Louvain, Institute of Mechanics, Materials and Civil Engineering (IMMC) & Earth and Life Institute (ELI), 1348 Louvain-la-Neuve, Belgium
5ETH Zurich, Institute for Atmospheric and Climate Science, 8092 Zurich, Switzerland
1Vrije Universiteit Brussel, Department of Hydrology and Hydraulic Engineering, 1050 Brussels, Belgium
2Institute for Marine and Atmospheric Research, Utrecht University, Princetonplein 5, 3584 CC Utrecht, the Netherlands
3Université Catholique de Louvain, Institute of Mechanics, Materials and Civil Engineering (IMMC), 1348 Louvain-la-Neuve, Belgium
4Université Catholique de Louvain, Institute of Mechanics, Materials and Civil Engineering (IMMC) & Earth and Life Institute (ELI), 1348 Louvain-la-Neuve, Belgium
5ETH Zurich, Institute for Atmospheric and Climate Science, 8092 Zurich, Switzerland
Received: 02 Jun 2020 – Discussion started: 08 Jul 2020
Abstract. Lake Tanganyika is the second oldest (oldest basin of the lake is 9–12 million years old), second deepest (1470 m) lake in the world. It holds 16 % of the world's liquid freshwater. Approximately 100 000 people are directly involved in the fisheries operating from almost 800 sites along its shores. Despite the vital importance of Lake Tanganyika and other African inland waters for local communities, very little is known about the impacts of future climate change on the functioning of these lacustrine systems. This is remarkable, as projected future changes in climate and associated weather conditions are likely to influence the hydrodynamics of African water bodies, with impacts cascading into ecosystem functioning, fish availability and water quality. Here we project the future changes in the hydrodynamics of Lake Tanganyika under a high-end emission scenario using the 3D version of the Second-generation Louvain-la-Neuve Ice-ocean Model (SLIM 3D) forced by a highresolution regional climate model. We first show the added value of 3D simulations compared to previously obtained 1D model results. The simulated interseasonal variability of the lake with this 3D model explains how the current mixing system works. A short-term present-day simulation (10 years) shows that the 75 m deep thermocline moves upward in the south of the lake until the lower layer reaches the lake surface during August and September. Two 30-year simulations have been performed (one with present day and one with future conditions), such that a comparison can be made between the current situation and the situation at the end of the 21st century. The results show that the surface water temperature increases on average by 3 ± 0.5 K. The latter influences the hydrodynamics in the top 150 m of the lake, namely the bottom of the thermocline does not longer surface. This temperature-induced stratification fully shuts down the earlier explained mixing mechanism.
This work covers multiple 3D simulations of the hydrodynamics of Lake Tanganyika, covering the inter-seasonal variations and the evolution linked to climate change. The research was done with COSMO-CLM2 data, which was used to run the SLIM 3D Lake Tanganyika model. The main results explain how this stratified lake can still maintain a certain mixing between the different layers, but how this would come to an end due to climate change.
This work covers multiple 3D simulations of the hydrodynamics of Lake Tanganyika, covering the...