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Alfred Johny Wüest

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Related publications (118)

Using small-scale measurements to estimate hypolimnetic oxygen depletion in a deep lake

Alfred Johny Wüest, Damien Bouffard, Robert Vincent Schwefel

Low oxygen concentrations in lakes and reservoirs are an ongoing environmental concern, particularly in light of increasing anthropogenic activity and climate change. Oxygen depletion processes in lakes are still not completely understood and a variety of ...

American Society of Limnology and Oceanography2018

Hydrodynamics of a periodically wind‑forced small and narrow stratified basin: a large‑eddy simulation experiment

Alfred Johny Wüest, Damien Bouffard, Oscar Rodrigo Sepúlveda Steiner, Serban George Constantinescu, Kyoung Sik Chang, Hugo Nicolás Ulloa Sánchez

We report novel results of a numerical experiment designed for examining the basin-scale hydrodynamics that control the mass, momentum, and energy distribution in a daily wind-forced, small thermally-stratified basin. For this purpose, the 3-D Boussinesq e ...

2018

Are surface temperature and chlorophyll in a large deep lake related? An analysis based on satellite observations in synergy with hydrodynamic modelling and in-situ data

Alfred Johny Wüest, Damien Bouffard, Isabel Blanca Sophie Kiefer

2018

Effects of non-uniform vertical constituent profiles on remote sensing reflectance of oligo- to mesotrophic lakes

Alfred Johny Wüest, Damien Bouffard, Vincent Maurice Nouchi

We investigate the impact on remote sensing reflectance by the vertical non-uniformities of water constituents. Reflectance simulated for 210 pairs of in situ measured chlorophyll-a and turbidity profiles (z = 0–20 m) from Lake Geneva are compared to simul ...

2018

Scaling oxygen microprofiles at the sediment interface of deep stratified waters

Alfred Johny Wüest, Damien Bouffard, Robert Vincent Schwefel, Miki Hondzo

Dissolved oxygen microprofiles at the sediment-water interface of Lake Geneva were measured concurrently with velocities 0.25 to 2m above the sediment. The measurements and scaling analyses indicate dissolved oxygen fluctuations and turbulent fluxes in exc ...

American Geophysical Union2017

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

Ulrich Lemmin, Alfred Johny Wüest, Damien Bouffard, David Andrew Barry, 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

Physical effects of thermal pollution in lakes

Alfred Johny Wüest, Damien Bouffard

Anthropogenic heat emissions into inland waters influence water temperature and affect stratification, heat and nutrient fluxes, deep water renewal, and biota. Given the increased thermal stress on these systems by growing cooling demands of riparian/coast ...

American Geophysical Union2017

Oxygen depletion in stratified lakes - why shallow and deep lakes react differently

Alfred Johny Wüest, Robert Vincent Schwefel

Oxygen is the most important element in natural waters for any higher aquatic life, such as fish. As with humans, almost all members of aquatic ecosystems need oxygen to breathe. Building on this, treatment of drinking water is easier for oxic than for ano ...

2016

Effects of climate change on deepwater oxygen and winter mixing in a deep lake (Lake Geneva): Comparing observational findings and modeling

Alfred Johny Wüest, Damien Bouffard, Adrien Gaudard, Robert Vincent Schwefel

Low concentrations of dissolved oxygen remain a global concern regarding the ecological health of lakes and reservoirs. In addition to high nutrient loads, climate-induced changes in lake stratification and mixing represent additional anthropogenic menace ...

American Geophysical Union2016

A new robust oxygen-temperature sensor for aquatic eddy covariance measurements

Alfred Johny Wüest, Hua Li

The fragility of thin Clark-type glass microelectrodes used in aquatic eddy covariance measurements of benthic oxygen fluxes is a challenge when using this powerful technique. This study presents a new fast-responding dual oxygen-temperature sensor for edd ...

Association for the Sciences of Limnology and Oceanography (ASLO)2016

Effects of climate change on deep-water oxygen and winter mixing in a deep lake (Lake Geneva)

Alfred Johny Wüest, Damien Bouffard, Robert Vincent Schwefel

Oxygen is the most important dissolved gas for lake ecosystems. Because low oxygen concentrations are an ongoing problem in many parts of the oceans and numerous lakes, oxygen depletion processes have been intensively studied over the last decades and were ...

2016

Ice-covered Lake Onega: effects of radiation on convection and internal waves

Natacha Tofield-Pasche, Alfred Johny Wüest, Damien Bouffard

Early-spring under-ice convection in the Petrozavodsk Bay of Lake Onega (Russia) was investigated as part of an interdisciplinary research project conducted during March 2015. Measurements performed using a thermistor chain and vertical profiling sensors w ...

Springer Verlag2016

Application of remote sensing for the optimization of in-situ sampling for monitoring of phytoplankton abundance in a large lake

Alfred Johny Wüest, Damien Bouffard, Isabel Blanca Sophie Kiefer

Directives and legislations worldwide aim at representatively and continuously monitoring the ecological status of surface waters. In many countries, chlorophyll-a concentrations (CHL) are used as an indicator of phytoplankton abundance and the trophic lev ...

Elsevier2015

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

Impact of deepwater mixing on hypoxia in Lake Geneva

Alfred Johny Wüest, Damien Bouffard, Robert Vincent Schwefel

Lake Geneva is recovering from its eutrophic past but no significant trend in the areal hypolimnetic oxygen depletion rate has been observed over the last 30 years. Due to the large depth of 309 m, the lake is not mixed completely every winter which can le ...

2015

Characterisation of the subaquatic groundwater discharge that maintains the permanent stratification within Lake Kivu; East Africa

Alfred Johny Wüest, Martin Schmid

Warm and cold subaquatic groundwater discharge into Lake Kivu forms the large-scale density gradients presently observed in the lake. This structure is pertinent to maintaining the stratification that locks the high volume of gases in the deepwater. Our re ...

Public Library of Science2015

Lake surface temperatures in a changing climate: a global sensitivity analysis

Stefan Hunziker, Alfred Johny Wüest, Martin Schmid

We estimate the effects of climatic changes, as predicted by six climate models, on lake surface temperatures on a global scale, using the lake surface equilibrium temperature as a proxy. We evaluate interactions between different forcing variables, the se ...

Springer Verlag2014

Sediment oxygen uptake in Lake Geneva

Alfred Johny Wüest, Damien Bouffard, Robert Vincent Schwefel

Between 1960 and 1980, the trophic state of Lake Geneva (situated between France and Switzerland) has changed from oligotrophic to eutrophic. Since then, the areal hypolimnetic oxygen demand of 1.31 gm-2 d-1 is now the highest measured in Switzerland and l ...

2014

Accelerated Water Quality Improvement during Oligotrophication in Peri-Alpine Lakes

Alfred Johny Wüest, Beat Mueller

Monitoring of four eutrophic Swiss lakes undergoing oligotrophication during more than 25 years (i.e., gradually decreasing nutrient loading, productivity, and associated symptoms of eutrophication) revealed that phosphorus (P) net sedimentation rates (the ...

Amer Chemical Soc2014

Double-diffusive interfaces in Lake Kivu reproduced by direct numerical simulations

Alfred Johny Wüest

Double diffusion transforms uniform background gradients of temperature and salinity into "staircases" of homogeneous mixed layers that are separated by high-gradient interfaces. Direct numerical simulations (DNS) and microstructure measurements are two in ...

Amer Geophysical Union2014

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