Soirée de rencontre autour du livre « Tout comprendre (ou presque) sur le climat »

10/11/2023 19:00

Keep In Touch 2023 ! Le 2e RDV Alumni de l’IPSL-Climate Graduate School

09/11/2023 18:30

Festival Explor'Espace

03/11/2023 10:00

ClimarisQ: un jeu vidéo pour comprendre la complexité du climat et l'urgence d'une action collective

17/06/2021 11:00

ClimarisQ est un jeu pour smartphone/web issu d’un projet de médiation scientifique qui met en évidence la complexité du système climatique et l’urgence d’une action collective pour limiter le changement climatique.

Impact de la fonte du pergélisol sur la dynamique du carbone des tourbières arctiques

15/06/2021 11:00

Aux hautes latitudes, le pergélisol, le sol restant gelé deux années consécutives, évolue rapidement sous la pression du changement climatique. Le pergélisol contient la moitié du stock de carbone organique mondial des sols. Si ce carbone, accumulé depuis des millénaires, est réémis vers l’atmosphère, cela constituerait un rétroaction positive au changement climatique.

Impacts de l’arasement d’un barrage sur la morphologie d’un cours d’eau et la remobilisation de sédiments contaminés

11/06/2021 12:00

L’impact anthropique sur les cours d’eau a significativement augmenté suite à la révolution industrielle engagée par les pays occidentaux.

Caractérisation de la banquise Arctique à partir d'observations micro-ondes multi-instruments et multi-fréquences

16/11/2022 14:30

La glace de mer joue un rôle majeur dans la circulation océanique et dans le système climatique et météorologique. Dans un contexte de réchauffement climatique, où l’étendue de la glace de mer arctique diminue régulièrement depuis 40 ans, le suivi et la surveillance de l’Arctique sont essentiels. Les instruments micro-ondes embarqués sur les satellites permettent d’étudier cette région de la Terre par tous les temps, indépendamment du cycle jour/nuit. Particulièrement adaptées à l’observation des régions polaires où la présence de nuages est importante et où la nuit polaire dure six mois, les observations par satellite micro-ondes sont la pierre angulaire des estimations des paramètres géophysiques de la glace de mer.
Néanmoins, la compréhension de la physique sous-jacente aux signatures micro-ondes observées est encore partielle. Cette thèse vise à améliorer notre compréhension des signaux micro-ondes de la glace de mer.

Impact of the spatial and temporal variability of the Mistral on dense water formation in the Mediterranean Sea

21/10/2022 14:00

Deep convection is the process where surface water is cooled to the point it becomes dense enough that it sinks to the seafloor. In the Gulf of Lion, the dense water it produces helps the general circulation of the Mediterranean Sea. In this region, the cooling is mainly caused by the Mistral winds and seasonal change of the atmosphere. This thesis explores the individual and relative cooling provided by these two sources, finding that both sources contribute to the cooling, with the seasonal change providing more than the Mistral. However, in the future neither are able to overcome the predicted changes to the gulf due to climate change, and deep convection is believed to stop altogether. Due to this, part of the thesis looks at methanol producing islands; devices that could help mitigate climate change and energy availability, especially in the Mediterranean.

Local and remote sources of Arctic air pollution

09/09/2022 10:00

The Arctic region is warming faster than any other region on Earth due to the effect of greenhouse gases, notably CO₂, and short-lived climate forcers of anthropogenic origin, such as black carbon (BC). Over the last 20-30 years, remote anthropogenic emissions over mid-latitude regions have been decreasing. Anthropogenic emissions within the Arctic are also contributing and might increase in the future and further affect Arctic air pollution and climate. Natural emissions, such as sea-spray aerosols, also might increase due to on-going climate change. However, the processes and sources influencing Arctic aerosols and trace gases are poorly quantified, especially in wintertime.

In this thesis, quasi-hemispheric and regional simulations are performed using the Weather Research Forecast model, coupled with chemistry (WRF-Chem). The model is used to investigate atmospheric composition over the wider Arctic and during two field campaigns, one in northern Alaska at Barrow, Utqiaġvik in January and February 2014 and the second in Fairbanks, central Alaska in November and December 2019 during the French pre-ALPACA (Alaskan Layered Pollution And Chemical Analysis) campaign.

First, modelled inorganic and sea-spray (SSA) aerosols are evaluated at remote Arctic sites during wintertime. Then, the model is improved with respect to SSA treatments, following evaluation against Barrow field campaign data, and their contribution to the total aerosol burden within the Arctic region is quantified. A series of sensitivity runs are performed over northern Alaska, revealing model uncertainties in processes influencing SSA in the Arctic such as the presence of sea-ice and open leads. Second, a sensitivity analysis is performed to investigate processes and sources influencing wintertime BC over the wider Arctic and over northern Alaska, with a focus on removal treatments and regional emissions. Variations in model sensitivity to wet and dry deposition are found across the Arctic and could explain model biases. Over northern Alaska, regional emissions from petroleum extraction are found to make an important contribution to observed BC.

Model results are also sensitive to planetary boundary layer parameterisation schemes. Third, the improved version of the model is used to investigate the contribution of regional and local sources on air pollution in the Fairbanks area in winter 2019. Using up-to-date emissions, the model performs better in winter 2019 than in winter 2014, when compared to observations at background sites across Alaska. Underestimations in modelled BC and sulphate aerosols can be partly explained by lacking local and regional anthropogenic emissions. In the case of sulphate, additional secondary aerosol formation mechanisms under dark/cold conditions also need to be considered.