Modélisation numérique des cycles de l'eau et des poussières de la planète Mars et de leurs couplages

This thesis focuses on the improvement of the representation of the atmosphere of the planet Mars by the martian Global Climate Model (GCM) of the Laboratoire de Météorologie Dynamique (LMD). The martian GCM developped at LMD in collaboration with several european teams (LATMOS, IAA Grenade, University of Oxford, The Open University) and with the support of ESA and CNES is used for many applications. This model aims at forecasting the detailed behaviour of the martian climate described by the cycles of carbon dioxyde, of water, of dust so as photochemistry, essentially based on universal equations. The comparison of GCM simulations with the available observations allows their interpretation, and sometimes reveals that some climatic processes are poorly modeled. These problematic processes notably result from the action of sub-grid scale mechanisms, meaning they are not directly resolved by the model. The work of this thesis consists in studying and parametrizing the effect of some of these mechanisms. With the help of the analysis and modeling of these processes, we try to correct the model's defects regarding the vertical distribution of water vapour and water ice, so as the exchanges with the surface, the vertical distribution of dust, with notably the modeling of the detached dust layers, and of course the effect of their couplings. Furthermore, we focus on the sub-grid scale processes of the atmosphere, which can significantly impact the global circulation, in particular the non-orographic gravity waves, which I have studied by analysing MAVEN mission observations.Cette thèse porte sur l'amélioration de la représentation de l'atmosphère de la planète Mars par le Modèle de Climat Global (« GCM ») martien du Laboratoire de Météorologie Dynamique (LMD). Le GCM martien développé au LMD en collaboration avec plusieurs équipes européennes (LATMOS, IAA Grenade, University of Oxford, The Open University), et avec le soutien de l'ESA et du CNES, est utilisé pour de nombreuses applications. Ce modèle s'efforce de prédire le comportement détaillé du climat martien décrit par les cycles du dioxyde de carbone, de l'eau, des poussières et de la photochimie, uniquement à partir d'équations universelles. La comparaison des simulations du GCM avec les observations disponibles permet de les interpréter, et révèle parfois que certains processus climatiques martiens restent mal modélisés. Le travail de cette thèse consiste à étudier et paramétriser l'effet de certains de ces mécanismes sous-maille, c'est-à-dire non résolus directement par le modèle. À l'aide de l'analyse et de la modélisation de ces processus on tente de corriger les défauts du modèle concernant la distribution verticale de la vapeur et de la glace d'eau, ainsi que les échanges avec la surface, la distribution verticale des poussières, avec notamment la modélisation des couches détachées de poussière, et bien sûr les effets de leurs couplages. Mais aussi, on s'intéresse aux phénomènes sous-maille de l'atmosphère qui peuvent avoir un impact extrêmement important sur la circulation globale, en particulier les ondes de gravité non-orographiques que j'ai étudiées en analysant les observations de la mission MAVEN

Numerical modeling of the water and dust cycles of the planet Mars and their couplings

Cette thèse porte sur l'amélioration de la représentation de l'atmosphère de la planète Mars par le Modèle de Climat Global (« GCM ») martien du Laboratoire de Météorologie Dynamique (LMD). Le GCM martien développé au LMD en collaboration avec plusieurs équipes européennes (LATMOS, IAA Grenade, University of Oxford, The Open University), et avec le soutien de l'ESA et du CNES, est utilisé pour de nombreuses applications. Ce modèle s'efforce de prédire le comportement détaillé du climat martien décrit par les cycles du dioxyde de carbone, de l'eau, des poussières et de la photochimie, uniquement à partir d'équations universelles. La comparaison des simulations du GCM avec les observations disponibles permet de les interpréter, et révèle parfois que certains processus climatiques martiens restent mal modélisés. Le travail de cette thèse consiste à étudier et paramétriser l'effet de certains de ces mécanismes sous-maille, c'est-à-dire non résolus directement par le modèle. À l'aide de l'analyse et de la modélisation de ces processus on tente de corriger les défauts du modèle concernant la distribution verticale de la vapeur et de la glace d'eau, ainsi que les échanges avec la surface, la distribution verticale des poussières, avec notamment la modélisation des couches détachées de poussière, et bien sûr les effets de leurs couplages. Mais aussi, on s'intéresse aux phénomènes sous-maille de l'atmosphère qui peuvent avoir un impact extrêmement important sur la circulation globale, en particulier les ondes de gravité non-orographiques que j'ai étudiées en analysant les observations de la mission MAVEN.This thesis focuses on the improvement of the representation of the atmosphere of the planet Mars by the martian Global Climate Model (GCM) of the Laboratoire de Météorologie Dynamique (LMD). The martian GCM developped at LMD in collaboration with several european teams (LATMOS, IAA Grenade, University of Oxford, The Open University) and with the support of ESA and CNES is used for many applications. This model aims at forecasting the detailed behaviour of the martian climate described by the cycles of carbon dioxyde, of water, of dust so as photochemistry, essentially based on universal equations. The comparison of GCM simulations with the available observations allows their interpretation, and sometimes reveals that some climatic processes are poorly modeled. These problematic processes notably result from the action of sub-grid scale mechanisms, meaning they are not directly resolved by the model. The work of this thesis consists in studying and parametrizing the effect of some of these mechanisms. With the help of the analysis and modeling of these processes, we try to correct the model's defects regarding the vertical distribution of water vapour and water ice, so as the exchanges with the surface, the vertical distribution of dust, with notably the modeling of the detached dust layers, and of course the effect of their couplings. Furthermore, we focus on the sub-grid scale processes of the atmosphere, which can significantly impact the global circulation, in particular the non-orographic gravity waves, which I have studied by analysing MAVEN mission observations

Cryogenic origin of fractionation between perchlorate and chloride under modern martian climate

International audienceAbstract The high perchlorate (ClO 4 − ) to chloride (Cl − ) ratios observed at the Phoenix landing site, northern polar region of Mars, have been puzzling since detection. However, a lack of understanding of perchlorate-chloride-water systems under cryogenic conditions makes it difficult to assess ClO 4 − /Cl − ratios during deliquescence-related processes. Here we quantitatively evaluate ClO 4 − /Cl − fractionation in deliquescence-induced brines of magnesium- and calcium-perchlorate-chloride salt mixtures under subzero conditions, by measuring solubility data and constructing temperature-dependent thermodynamic models. We find that under specific relative humidity (RH) and temperature ( T ) conditions, deliquescence of perchlorate-chloride mixtures may form brines with fractionated ClO 4 − /Cl − signatures. Appropriate RH -T , water-limited conditions, and aeolian processes are required to produce and preserve the elevated ClO 4 − /Cl − signatures in soils. Under the present climate, the north polar region can support ClO 4 − /Cl − fractionation and potentially enrich perchlorate for longer periods on global Mars. This highlights the uniqueness of Mars’ arctic environment and its implications for modern habitability

Climatological controls on the chemical stratigraphy of the martian polar layer deposits

International audienc

Climatological controls on the chemical stratigraphy of the martian polar layer deposits

International audienc

Climatological controls on the chemical stratigraphy of the martian polar layer deposits

International audienc

The effect of the Martian 2018 global dust storm on HDO as predicted by a Mars Global Climate Model

International audienceThe D/H ratio is commonly used to investigate the history of water on Mars, yet the mechanisms controlling present‐day HDO behavior are poorly understood. Significant variations of the D/H ratio were first predicted on the basis of a 3D global climate model, which were later confirmed by ground‐based observations. This behaviour, consisting of lower HDO/H2O ratios in the colder regions of Mars, is related to the isotopic fractionation occurring at condensation. We leverage this previous effort and present an updated implementation, using the modern version of the model, that remains in agreement with the older version. We explore the impact of the Global Dust Storm that occurred during Martian Year 34 on HDO. Our simulations indicate that HDO is on average 40% more abundant at 100 km during the MY34 GDS year than during a regular year, with likely large consequences for the escape flux of water that year

Stratigraphic and Isotopic Evolution of the Martian Polar Caps from Paleo‐Climate Models.

International audienceExposed scarps images and ice-penetrating radar measurements in the North Polar Layered Deposits (NPLD) of Mars show alternating layers that provide an archive of past climate oscillations, that are thought to be linked to orbital variations, akin to Milankovitch cycles on Earth. We use the Laboratoire de Météorologie Dynamique (LMD) Martian Global Climate Model (GCM) to study paleoclimate states to enable a better interpretation of the NPLD physical and chemical stratigraphy. When a tropical ice reservoir is present, water vapor transport from the tropics to the poles at low obliquity is modulated by the intensity of summer. At times of low and relatively constant obliquity, the flux still varies due to other orbital elements, promoting polar layer formation. Ice migrates from the tropics towards the poles in two stages. First, when surface ice is present in the tropics, and second, when the equatorial deposit is exhausted, from ice that was previously deposited in mid-high latitudes. The polar accumulation rate is significantly higher when tropical ice is available, forming thicker layers per orbital cycle. However, the majority of the NPLD is sourced from ice that temporary resided in the mid-high latitudes and the layers become thinner as the source location moves poleward. The migration stages imprint different D/H ratios in different sections in the PLDs. The NPLD is isotopically depleted compared to the SPLD in all simulations. Thus we predict the D/H ratio of the atmosphere in contact with NPLD upper layers is biased relative to the average global ice reservoirs

Climatological controls on the chemical stratigraphy of the martian polar layer deposits

International audienc

Modeling of the effect of the MY34 Global Dust Storm on the martian HDO cycle.

International audienc