Publications de Ulrich Lemmin | EPFL Graph Search

Buoyancy-tilted Shear Layers and Coherent Structures in Hyperpycnal River Plume Plunging

Ulrich Lemmin, David Andrew Barry, Haoran Shi

Shear layers and corresponding Kelvin Helmholtz-type Coherent Structures (KHCS) can be generated by rivers discharging into laterally-unconfined quiescent open water bodies (e.g., lakes). When the river discharge has a greater density than the receiving wa ...

AMER GEOPHYSICAL UNION2025

Identifying and quantifying unexpected deep zooplankton diel vertical migration in a large deep lake

Ulrich Lemmin, David Andrew Barry, Htet Kyi Wynn, Valentin Kindschi, Rafael Sebastian Reiss, Violaine Florette Piton

Diel Vertical Migration (DVM), a widespread zooplankton behavior in freshwater and marine systems, affects ecological interactions and biogeochemical cycles. In lakes, DVM has mainly been studied in the upper 50 m of the water column. However, based on aco ...

American Society of Limnology and Oceanography2025

Hydro-sedimentary processes of a plunging hyperpycnal river plume revealed by synchronized remote imagery and gridded current measurements

Ulrich Lemmin, Koen Blanckaert, David Andrew Barry

The present knowledge of plunging hyperpycnal river plumes is mainly based on two-dimensional (confined) laboratory experiments. Several hypotheses on three-dimensional (unconfined) flow processes have been made, but not tested in situ. In this field study ...

American Geophysical Union2024

Field Observations Reveal How Plunging Mixing and Sediment Resuspension Affect the Pathway of a Dense River Inflow Into a Deep Stratified Lake

Ulrich Lemmin, David Andrew Barry

The pathway of dense river inflows into lakes, which affects the lake water quality, is not accurately predicted by existing models. The pathway of a dense riverine inflow in a lake with a submerged canyon is analyzed based on measurements during a 4-month ...

Amer Geophysical Union2024

Tracking the Nearfield Evolution of an Initially Shallow, Neutrally Buoyant Plane Jet Over a Sloping Bottom Boundary

Ulrich Lemmin, David Andrew Barry, Haoran Shi

Understanding coastal plane jets which occur when a body of water discharges into an ocean or a lake through a channel or outlet is important, since they play a significant role in sediment, nutrient, and pollutant exchange. This study investigates the nea ...

Amer Geophysical Union2024

Deepwater Renewal in a Large, Deep Lake (Lake Geneva): Identifying and Quantifying Winter Cooling Processes Using Heat Budget Decomposition

Ulrich Lemmin, David Andrew Barry, François Mettra, Rafael Sebastian Reiss, Naifu Peng

Wintertime deepwater renewal, which is important for heat-oxygen-nutrient exchange in lakes, is traditionally considered to be mainly driven by 1D vertical convective cooling. However, differential cooling between shallow and deep waters can produce densit ...

Amer Geophysical Union2024

From Particles to Flocs: Revealing Where Flocculation Occurs in the Nearfield of a Negatively-Buoyant River Plume in a Large Lake (Lake Geneva)

Ulrich Lemmin, David Andrew Barry, Htet Kyi Wynn, Valentin Kindschi, Violaine Florette Piton

The dynamics of sediments entering lakes in river plumes is virtually unknown. This field study provides unprecedented evidence of the initiation and evolution of suspended sediment flocculation in the nearfield of the negatively-buoyant Rh & ocirc;ne Rive ...

Amer Geophysical Union2024

Strong bottom currents in large, deep Lake Geneva generated by higher vertical-mode Poincaré waves

Ulrich Lemmin, David Andrew Barry, Rafael Sebastian Reiss

Although internal seiches are ubiquitous in large, deep lakes, little is known about the effect of higher vertical-mode seiches on deepwater dynamics. Here, by combining entire summer season current and temperature observations and 3D numerical modeling, w ...

Springer Science and Business Media LLC2024

What role does stratification play during winter in wind-induced exchange between the multi-depth basins of a large lake (Lake Geneva)?

Ulrich Lemmin, David Andrew Barry, Rafael Sebastian Reiss

Detailed studies of wind-driven interbasin exchange in lakes, focusing on the underlying driving forces and how they are affected by stratification, are presently lacking. We therefore investigated how strati-fication modifies wind-induced exchange between ...

2023

The role of submesoscale filaments in restratification of the surface mixed layer and dissolved oxygen variability in large Lake Geneva: field evidence complemented by Lagrangian particle-tracking

Ulrich Lemmin, David Andrew Barry, Rafael Sebastian Reiss, Mehrshad Foroughan, Seyed Mahmood Hamze Ziabari

Theoretical studies on oceans and large lakes have shown that submesoscale instabilities in frontal zones tend to reduce horizontal density gradients and enhance vertical density gradients, thereby re-stratifying the Surface Mixed Layer (SML). Submesoscale ...

2023

Chimney‐Like Intense Pelagic Upwelling in the Center of Basin‐Scale Cyclonic Gyres in Large Lake Geneva

Ulrich Lemmin, David Andrew Barry, Rafael Sebastian Reiss, Mehrshad Foroughan, Seyed Mahmood Hamze Ziabari

Basin-scale quasi-geostrophic gyres are common features of large lakes subject to Coriolis force. Cyclonic gyres are often characterized by dome-shaped thermoclines that form due to pelagic upwelling that takes place in their center. At present, the dynami ...

2023

Effects of natural surfactants on the spatial variability of surface water temperature under intermittent light winds on Lake Geneva

Ulrich Lemmin, David Andrew Barry, Mehrshad Foroughan

The spatial variability of lake surface water temperature (LSWT) between smooth and rough surface areas and its potential association with the natural surfactant distribution in the surface microlayer were investigated for the first time in a lake. In spri ...

2022

Unconfined Plunging of a Hyperpycnal River Plume Over a Sloping Bed and Its Lateral Spreading: Laboratory Experiments and Numerical Modeling

Ulrich Lemmin, Koen Blanckaert, David Andrew Barry, Haoran Shi

Hyperpycnal (negatively buoyant) river inflow into lakes and oceans often develops three-dimensional (3D) plunging flow patterns when laterally unconfined. To determine the 3D flow pattern characteristics, laboratory experiments of laterally unconfined plu ...

American Geophysical Union2022

Wind‐Induced Hypolimnetic Upwelling Between the Multi‐Depth Basins of Lake Geneva During Winter: An Overlooked Deepwater Renewal Mechanism?

Ulrich Lemmin, David Andrew Barry, Rafael Sebastian Reiss

Combining field observations, 3D hydrodynamic modeling, and particle tracking, we investigated wind-induced interbasin exchange between the Petit Lac (PL) (depth 75 m) and Grand Lac (GL) (depth 309 m) basins of Lake Geneva in early winter. Following a stro ...

2022

Detecting submesoscale cold filaments in a basin-scale gyre in large, deep Lake Geneva (Switzerland/France)

Ulrich Lemmin, David Andrew Barry, Amir Mehdi Razmi, Seyed Mahmood Hamze Ziabari

Submesoscale filaments are a well-documented feature of oceanic flow fields. Based on the analysis of high-resolution 3D numerical simulations, field observations and remote sensing imagery, this study, carried out in Lake Geneva, Western Europe's largest ...

2022

A Persistent Submesoscale Frontal Slick: A Novel Marker of the Mesoscale Flow Field in a Large Lake (Lake Geneva)

Ulrich Lemmin, David Andrew Barry, Mehrshad Foroughan, Seyed Mahmood Hamze Ziabari

Submesoscale fronts often become visible when the accumulation of biosurfactants in the water surface microlayer causes smooth surfaces, called frontal slicks, to develop. Based on in situ and remotely-sensed data, a frontal slick was documented for the fi ...

2022

Monitoring Mesoscale to Submesoscale Processes in Large Lakes with Sentinel-1 SAR Imagery: The Case of Lake Geneva

Ulrich Lemmin, David Andrew Barry, Mehrshad Foroughan, Seyed Mahmood Hamze Ziabari

As in oceans, large-scale coherent circulations such as gyres and eddies are ubiquitous features in large lakes that are subject to the Coriolis force. They play a crucial role in the horizontal and vertical distribution of biological, chemical and physica ...

2022

Tracing Unconfined Nearfield Spreading of a River Plume Interflow in a Large Lake (Lake Geneva): Hydrodynamics, Suspended Particulate Matter, and Associated Fluxes

Ulrich Lemmin, David Andrew Barry, Htet Kyi Wynn, Benjamin Daniel Graf, Frédéric Charles Soulignac, Violaine Florette Piton

River inflows have a major influence on lake water quality due to their input of sediments, nutrients and contaminants. After leaving the river channel, river waters form a plume and interact with ambient lake waters. Strong hydrodynamic changes take place ...

2022

Basin-scale gyres and mesoscale eddies in large lakes: A novel procedure for their detection and characterization, assessed in Lake Geneva

Ulrich Lemmin, David Andrew Barry, Mehrshad Foroughan, Frédéric Charles Soulignac, Seyed Mahmood Hamze Ziabari

In large lakes subject to the Coriolis force, basin-scale gyres and mesoscale eddies, i.e. rotating coherent water masses, play a key role in spreading biochemical materials and energy throughout the lake. In order to assess the spatial and temporal extent ...

2022

Rapid changes in river plume dynamics caused by advected wind-driven coastal upwelling as observed in Lake Geneva

Ulrich Lemmin, David Andrew Barry, Htet Kyi Wynn, Benjamin Daniel Graf, Frédéric Charles Soulignac, Seyed Mahmood Hamze Ziabari

Based on field investigations carried out in Lake Geneva during summer stratification in 2019, this study documents, for the first time, the rapid change of negatively buoyant river inflow dynamics caused by the passing of a coastal upwelling. Under calm c ...

American Society of Limnology and Oceanography2021