Dernière période glaciaire

vignette|redresse=1.5|Extension des inlandsis dans l'hémisphère nord lors de la dernière glaciation. vignette|redresse=1.5|L'Europe au dernier maximum glaciaire, il y a environ . La dernière période glaciaire est une période de refroidissement global, ou glaciation, qui caractérise la fin du Pléistocène sur l'ensemble de la planète. Elle commence il y a et se termine il y a , quand commence l'Holocène. Elle correspond aux stades 2, 3, 4 et 5a-d de la chronologie isotopique, mise au point à la fin du . Le maximum glaciaire a été atteint il y a environ . Ses manifestations locales plus ou moins synchrones sont connues sous les noms de glaciation de Würm ou Würmien dans les Alpes, Wisconsinien en Amérique du Nord, glaciation vistulienne ou Vistulien en Europe du Nord, Devensien ou Midlandien dans les Îles Britanniques, Zyriankien en Sibérie, glaciation de Valdaï dans les plaines de Russie occidentale, glaciation de Merida au Venezuela, et glaciation de Llanquihue en Patagonie. Selon l

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (19)

Publications associées

Chargement

Personnes associées (2)

Personnes associées

Chargement

Unités associées (2)

Unités associées

Chargement

Concepts associés (71)

Concepts associés

Chargement

Cours associés (2)

Cours associés

Chargement

Séances de cours associées (2)

Séances de cours associées

Chargement

Modelling pumped-storage effects on thermal structure, ice cover and water quality of lakes and reservoirs in a changing climate

Ulrike Kobler

New renewable electricity is nowadays often generated by photovoltaics and wind. Yet, their intermittent nature calls for energy storage, which is today still provided to ~95% by pumped-storage (PS) hydropower plants. However, PS is known to affect abiotic and biotic characteristics of the two connected water bodies. Thus, a two-dimensional laterally-averaged hydrodynamic and water quality model was set up to assess the impacts on water quality and temperature in a first step. Then, this analysis was extended to evaluate the additional effect of climate change, which also modifies abiotic and biotic characteristics. For this purpose, 150-years long synthetic time series of meteorological conditions for current (1998-2012) and future climate (2078-2092) were generated with a weather generator. To assess the robustness of projected impacts on the ice cover of the upper reservoir (Sihlsee) three one-dimensional, vertical hydrodynamic models were additionally set up. To attribute effects to either the PS flows or to water withdrawal from the hypolimnion, two reference scenarios were defined: one with deep-water withdrawal (NoPS) and another one with surface outflow (QNat). While the hypolimnetic temperature differs by

EPFL2019

Chargement

Ensemble modelling of ice cover for a reservoir affected by pumped-storage operation and climate change

Ulrike Kobler, Martin Schmid

Ensemble modelling was used to assess the robustness of projected impacts of pumped-storage (PS) operation and climate change on reservoir ice cover. To this end, three one-dimensional and a two-dimensional laterally averaged hydrodynamic model were set up. For the latter, the strength of the impacts with increasing distance from the dam was also investigated. Climate change effects were simulated by forcing the models with 150 years of synthetic meteorological time series created with a weather generator based on available air temperature scenarios for Switzerland. Future climate by the end of the 21(st) century was projected to shorten the ice-covered period by similar to 2 months and decrease ice thicknesses by similar to 13 cm. Under current climate conditions, the ice cover would already be affected by extended PS operation. For example, the average probability of ice coverage on a specific day was projected to decrease by similar to 13% for current climate and could further be reduced from similar to 45% to similar to 10% for future climate. Overall, the results of all models were consistent. Although the number of winters without ice cover was projected to increase for all one-dimensional models, studying individual segments of the two-dimensional model showed that the impact was pronounced for segments close to the PS intake/outlet. In summary, the reservoir's ice cover is expected to partially vanish with higher probability of open water conditions closer to the PS intake/outlet.

WILEY2019

Chargement

Seasonal and spatial variation in hydrochemical parameters of Lake Onego (Russia): insights from 2016 field monitoring

Natacha Tofield-Pasche

This study describes seasonal water quality parameters measured in Petrozavodsk Bay, Lake Onego, Russia. Petrozavodsk Bay (PB) lies in the north of Lake Onego and adjacent to the city of Petrozavodsk. PB water quality is controlled by anthropogenic input, inflow of the Shuya River, and water exchange with open areas of the greater Lake Onego. We measured ion composition, organic matter, nutrients, gas composition, trace elements, and mercury throughout 2016, to evaluate PB water quality. Elevated humic content and organic matter, including total organic carbon (TOC = 17.0 mg L−1), total phosphorus (TP = 36 μg L−1), and water color (134 mg Pt L−1), demonstrated the eutrophic character of Shuya River input. Low humic and organic matter content (TOC = 6.5 mg L−1, TP=7μgL−1, water color = 26 mg Pt L−1) indicated the oligotrophic character of open lake waters. During winter, the PB hydrochemical regime was primarily controlled by Shuya River inflow because water exchange between the bay and open lake was restricted during its ice-covered period. As a result, PB chemical indices varied considerably. TOC varied from 7.6 to 17.8 mg L−1, TP from 7 to 55 μg L−1, and О2 from 69% to 87% saturation during this period. Total filterable mercury concentrations (THg = inorganic mercury plus methylmercury) at all measurement sites remained low. Overall, these results help constrain understanding of lake dynamics, anthropogenic influence, and river input to the lake during icecovered periods.

2019

Chargement

ENV-410: Science of climate change

The course equips students with a comprehensive scientific understanding of climate change covering a wide range of topics from physical principles, historical climate change, greenhouse gas emissions, the IPCC assessment to future scenarios and climate action.

ENV-220: Fundamentals in ecology

The students will learn the fundamentals in ecology with the goal to perceive the environment beyond its physical and chemical characteristics. Starting from basic concepts, they will acquire mechanistic understanding of biodiversity, ecosystem functioning and global change.

Glaciation

thumb|Représentation artistique de l'englacement lors du dernier maximum glaciaire (DMG) selon Ice age terrestrial carbon changes revisited de Thomas J. Crowley. Une glaciation (ou englaciation) est u

Europe

L’Europe est un territoire considéré conventionnellement comme un continent, délimité à l’ouest par l’océan Atlantique et le détroit de Danemark, au nord par l’océan Arctique. Sa limite méridionale

Holocène

L' (du grec ancien : , « entier », et , « récent ») est une époque géologique s'étendant sur les années, toujours en cours. Il est fréquemment subdivisé en fonction de palynozones. Définition