Publications related to Downwelling

Shedding light on the MRI-driven dynamo in a stratified shearing box

We study the magneto-rotational instability (MRI) dynamo in a geometrically thin disc (H/R < 1) using stratified zero net (vertical) flux shearing box simulations. We find that mean fields and electromotive forces (EMFs) oscillate with a primary frequency ...

2024

Combined Earth observations reveal the sequence of conditions leading to a large algal bloom in Lake Geneva

Damien Bouffard, Rafael Sebastian Reiss, Abolfazl Irani Rahaghi, Oscar Rodrigo Sepúlveda Steiner, Marco Toffolon, Frédéric Charles Soulignac

Freshwater algae exhibit complex dynamics, particularly in meso-oligotrophic lakes with sudden and dramatic increases in algal biomass following long periods of low background concentration. While the fundamental prerequisites for algal blooms, namely ligh ...

Springernature2024

Unraveling submesoscale processes associated with meso- and basin-scale gyres in Lake Geneva

Seyed Mahmood Hamze Ziabari

In large lakes, basin-scale gyres and submesoscale eddies, i.e., rotating coherent water masses, play a key role in spreading biochemical materials and energy throughout the basin, thereby significantly impacting water quality. Due to their transient and s ...

EPFL2023

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

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

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

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

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

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

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

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

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

Dynamics of wind-induced coastal upwelling and interbasin exchange in Lake Geneva during winter: Implications for deepwater renewal

Rafael Sebastian Reiss

Water quality in lakes is closely linked to hydrodynamics and often dominated by stratification, limiting the exchange between the epi- and hypolimnion. Thus, the vertical redistribution of biogeochemical tracers such as dissolved oxygen and nutrients by c ...

EPFL2021

Wintertime Coastal Upwelling in Lake Geneva: An Efficient Transport Process for Deepwater Renewal in a Large, Deep Lake

David Andrew Barry, Ulrich Lemmin, Andrea Cimatoribus, Rafael Sebastian Reiss

Combining field measurements, 3‐D numerical modeling, and Lagrangian particle tracking, we investigated wind‐driven, Ekman‐type coastal upwelling during the weakly stratified winter period 2017/2018 in Lake Geneva, Western Europe's largest lake (max. depth ...

2020

Diel quenching of Southern Ocean phytoplankton fluorescence is related to iron limitation

Nina Schuback

Evaluation of photosynthetic competency in time and space is critical for better estimates and models of oceanic primary productivity. This is especially true for areas where the lack of iron (Fe) limits phytoplankton productivity, such as the Southern Oce ...

2020

Differential Heating Drives Downslope Flows that Accelerate Mixed-LayerWarming in Ice-Covered Waters

Alfred Johny Wüest, Damien Bouffard, Hugo Nicolás Ulloa Sánchez, Kraig Bates Winters

In ice-covered lakes, penetrative radiation warms fluid beneath a diffusive boundary layer, thereby increasing its density and providing energy for convection in a diurnally active, deepening mixed layer. Shallow regions are differentially heated to warmer ...

2019

Gyre formation in open and deep lacustrine embayments: The example of Lake Geneva, Switzerland

David Andrew Barry, Alfred Johny Wüest, Ulrich Lemmin, Damien Bouffard, Amir Mehdi Razmi, Robert Eduard Uittenbogaard

Numerical simulations were carried out to investigate gyres within open lacustrine embayments subjected to parallel-to-shore currents. In such embayments, gyre formation occurs due to flow separation at the embayment’s upstream edge. High momentum fluid fr ...

Springer Verlag2017

Drivers of deep-water renewal events observed over 13 years in the South Basin of Lake Baikal

Alfred Johny Wüest, Martin Schmid

Lake Baikal, with a depth of 1637 m, is characterized by deep-water intrusions that bridge the near-surface layer to the hypolimnion. These episodic events transfer heat and oxygen over large vertical scales and maintain the permanent temperature stratifie ...

Amer Geophysical Union2015

Methane formation and future extraction in Lake Kivu

Alfred Johny Wüest, Natacha Tofield-Pasche, Martin Schmid

This chapter summarises the current knowledge on the vertical distribution of methane (CH4) and its formation in Lake Kivu. Additionally, we review the objectives and restrictions under consideration for sustainable extraction (safe, environmentally accept ...

Springer2012

Heat-driven spin currents on large scales

Jean-Philippe Ansermet, Sylvain Bréchet

Using a three-current model (i.e. heat, spin-up and spin-down electrons) the thermodynamics of irreversible processes predicts that a temperature gradient gives rise to a spin current on large scales, in particular under the conditions used to measure the ...

Wiley-Blackwell2011

An experimental study of coherent structures, secondary currents and surface boils and their interrelation in open-channel flow

Ismail Albayrak

River and open-channel flows are free surface boundary layer flows with complex 3D, large-scale, turbulent structures. The study of 2D and 3D large-scale turbulent flow structures is a great challenge for physicists, mathematicians and engineers from such ...

EPFL2008

Lake Baikal deepwater renewal mystery solved

Alfred Johny Wüest, Martin Schmid

Deepwater renewal by intrusions and turbulent diffusion in Lake Baikal is very effective despite the enormous depth of up to 1642 m and the permanently stable stratification below similar to 300 m depth. Temperature time series recorded at the bottom of a ...

Amer Geophysical Union2008

Intermittent oxygen flux from the interior into the bottom boundary of lakes as observed by eddy correlation

Alfred Johny Wüest, Bernhard Wehrli

Turbulent oxygen transport from the overlying stratified water column into the bottom boundary layer (BBL) on the slope of a medium-sized lake was investigated using the eddy correlation (EC) technique. The seicheinduced oscillatory flow of the BBL, with a ...

American Society of Limnology and Oceanography2008