In this talk, I will present results from several studies conducted in Lake Geneva, Western Europe's largest lake (max. depth 309 m). These studies combine field observations, 3D numerical modelling, and Lagrangian particle tracking. The first part of the talk will demonstrate the unexpected role of frequent coastal upwelling events during winter in
deepwater renewal and re-oxygenation of Lake Geneva’s deepest layers which routinely experience critically low oxygen levels. This is a process that has long been overlooked but is anticipated to become increasingly important as wintertime convective cooling weakens due
to climate change.
In the second part, I will explore the role that different higher vertical-mode standing internal waves play in the lake’s deepwater and nearshore dynamics. Instead of the “classical” two-layer current structure of their more widely studied vertical mode-one counterparts, these
standing wave modes are characterized by three- or four-layer current structures. The results shed light on the complex vertical and horizontal structure of these higher vertical-mode internal Kelvin and Poincaré waves and explain why numerous previous investigations in one
of the world’s most studied lakes – where the term limnology was coined more than a century ago and where the first Kelvin wave in a lake was documented in the 1960s – have not detected these wave modes. Understanding these wave modes, in Lake Geneva and in other
lakes worldwide, is crucial because of their role in deepwater mixing and sediment-water exchange, as well as the transport and dispersion of sediments, nutrients, and pollutants.