42-7 Circulation Dynamics and Climate Change Impacts on Lake Tanganyika: Insights from Modeling and Sediment Core Analysis

Session: Integrating 20 Years of Scientific Drilling in the East African-Syrian Rift: A Session In Honor of Andrew Cohen, Part II

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Lake Tanganyika, Africa’s largest rift lake and a vital ecological and economic resource in East and Central Africa, exhibits complex circulation patterns that are crucial for nutrient dynamics. Utilizing the Regional Ocean Modeling System (ROMS), we identified primary upwelling in the southern and southeastern regions from May to August and secondary upwelling in the northern region from November to February. Notably, we identified previously unrecognized downwelling from September to November along the lake's western side. Bathymetric variations significantly influence these processes, leading to multiple localized upwelling and downwelling events.

Current surface water temperatures range from 25.8°C to 27.8°C, with increases of up to 0.4°C at depths below 150 meters from 2001 to 2020. Climate change projections for 2100 suggest warming trends of up to 4°C, particularly in the northern region, which may disrupt nutrient cycling and exacerbate thermal stratification, adversely affecting local fisheries that provide approximately 40% of animal protein for surrounding communities. Increased wind speeds, projected to double in some scenarios, could enhance nutrient mixing, but may also lead to complex ecological responses.

Our sediment core analysis reveals that productivity and nutrient availability correlate with upwelling and hydroclimatic conditions, especially in offshore areas (Core 6A). A nearshore core (1A) indicates steady warming from 1850 to 2016, while another nearshore core close to a small river (53A) shows temperature fluctuations and productivity influenced by terrigenous input. These findings suggest that nearshore productivity, particularly near river inputs, may respond differently to climate change than open-water areas, impacting ecosystem dynamics.

 Additionally, sediment cores provide insights into the effects of future changes in rainfall, which pose modeling challenges due to the lack of data on these anticipated changes. Our study underscores the need for a multi-proxy approach across various lake habitats, combined with data-driven modeling, to enhance understanding of circulation and productivity changes over time, especially in the context of global climate change.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10175

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