Mercury (Hg) is a ubiquitous toxicant harmful to human health and the environment. Consumption of Hg-contaminated fish and seafood increases the risk for cardiovascular diseases and cognitive impairments. This global contamination issue is addressed under the 2017 Minamata Convention which commits its current 148 parties to curb anthropogenic Hg emissions. One common misconception is that mitigation policies will directly translate into reduced ecosystems contamination and human exposure. However, Hg environmental levels are driven by both modern emissions and remobilised legacy Hg from past emissions. In that context, international efforts to reduce Hg levels may be dampened as remobilisation of legacy Hg reservoirs is exacerbated by climate change. Here, we postulate that the Arctic, currently warming four times faster than the rest of the planet and already undergoing rapid ecosystem change, could become a globally-significant source of legacy Hg. This project focuses on large Hg stocks in Arctic permafrost soils that will be remobilised by intensifying permafrost thaw. What is unknown is the fate of this remobilised Hg: will it remain in the Arctic Ocean with possible dramatic effects on local food webs, or will it enter the global atmosphere and possibly counterbalance anthropogenic emissions reductions under the Minamata Convention? To address this major scientific knowledge gap, we propose novel model developments. We also address science-policy interactions by quantifying potential local and global impacts in the context of the Minamata Convention. This research will improve our ability to predict the region’s Hg contribution as a source of Hg and will have large policy implications.

This project, which builds on the results of the ANR COCOA project, aims at improving the representation of turbulent ocean-atmosphere exchanges in climate models by taking into account their modulation by waves using ocean-waves-atmosphere coupled modelling systems. Waves form by absorbing momentum in areas of storms and tropical cyclones, and transmit part of it to the ocean, with an impact on deep mixing and the overall heat balance. This energy absorbed by waves can be transported by swell over very long distances, from energetic areas (Southern Ocean, storms) to the inter-tropical band, for example. In this inter-tropical zone, where much of the heat and moisture exchange that drives atmospheric circulation on climatic scales takes place, conditions are met for swell to impact air-sea fluxes. It is therefore important to take into account the impact of waves in energetic zones, where they are formed and a large part of the energy is transferred to the ocean, and in dissipation zones, where they have an impact on surface fluxes. We plan to: 1) quantify the impact of wave-related processes on atmosphere-wave and wave-ocean exchanges at climate scales, based on existing model representations; 2) develop and validate new parameterizations to take into account, in coupled ocean-wave-atmosphere models at climate scales, processes related to tropical cyclones, the effect of waves on ocean mixing, and swell; 3) to build a coupled system around the wave model, ensuring complete consistency of momentum exchanges by resolving the inconsistencies of most of the current coupled systems used at weather prediction scales. This project should pave the way for state-of-the-art consideration of wave effects in climate models.

The Young Toba Tuff (YTT) super-eruption occurred 74 ky ago in Sumatra and is considered to be a single, brief, cataclysmic volcanic event. However, its climatic and environmental impact is the subject of lively debate. The critical issues remain the quantity and dynamics of its sulphur emissions, which are key to determining the climatic consequences of an eruption through the cooling role of stratospheric sulphate aerosols. Our recent results support a multi-eruptive Toba activity during the Earth's entry into the last ice age. Compared to a single cataclysmic event of a few days, a prolonged multi-eruptive activity could have a significant climatic impact by accumulating oceanic radiative cooling from repeated sulphur emissions and by perturbing atmosphere-ocean dynamics. The addition of volcanic sulphur could also lead to ocean acidification, damage oceanic biocalcifiers and interfere with background atmospheric CO2, although these effects have not been thoroughly investigated. To address these important issues, our project aims to i) constrain the rate of eruptive activity of the Young Toba super-volcano, ii) estimate its sulphur emission budgets and dynamics, and iii) reveal their impact on the surface temperature and ocean-atmosphere dynamics of the tropical Indian Ocean, including ocean acidification. To achieve our objectives, we have assembled an unprecedented team with a broad range of expertise in environmental and earth sciences (volcanology, paleoclimatology, paleoceanography, micropaleontology, glaciology, geochemistry, sedimentology), access to key archives (ice and marine cores), high performance analytical instrumentation and expertise in small sample geochemical techniques (tephra, polar ice, monospecific foraminiferal assemblages), all of which are essential to the success of the project. This new, unprecedented dataset will provide the basis for a better understanding of the climate forcing of super-volcanoes in the past and in the future.

Climate change and air pollution are two related issues. The novelty of ClimAir is to consider these issues in a combined way at the urban scale, that of Grenoble, during this century. The objective is to evaluate scenarios for mitigating greenhouse gas (GHG) emissions and air pollution, as well as scenarios for adapting to climate change that preserve air quality. Another objective is to provide recommendations to local authorities for consistent public policies in terms of pollution and GHG emissions. The local impact of climate change for the 21st century is first estimated using an original chain of numerical models based on the latest generation of climate models. Policies for mitigating GHG emissions and air pollution, as well as for adapting to climate change, are then studied using an interdisciplinary approach. Scenarios are considered for (i) emissions from mobility and the residential sector, (ii) adaptation measures through urban planning, such as greening the city. The impact of these scenarios on GHGs, air quality and health and their economic costs and benefits are assessed and quantified. ClimAir also deals with the social impact of these scenarios, through the resulting choice of residential location, the resulting social inequalities, and their impact on the most vulnerable population. The consortium brings together partners with complementary skills in the fields of climate, atmospheric sciences, urban air quality, epidemiology and environmental economics, social sciences, in particular socio-spatial inequalities, and geography. The collaboration builds on the experience gained from past and ongoing projects. It also includes international researchers (UK and Spain). The project is organized in six work packages (WP). WP1 provides climate projections for the 21st century, with a focus on three periods centered on 2030, 2050 and 2070. A downscaling is performed towards the Auvergne Rhône-Alpes region in WP2, and towards the Grenoble agglomeration in WP3. WP2 is dedicated to air pollution mitigation scenarios. WP3 considers heat waves and the effect of mitigation scenarios on temperature and air pollution. The aim of WP4 is to quantitatively estimate the impact of these scenarios on health. WP5 is devoted to a cost-benefit analysis of the scenarios, their social and economic impact and the impact on residential location choices. WP6 loops through feedback scenarios from WP5 to the other WPs, such as the definition and study of scenarios aiming at reducing the social inequalities that will be highlighted by WP5. The health and economic impact of these feedback scenarios will also be addressed. An annual meeting will be organized with local decision-makers in a co-construction approach of policies for the urban area. Among the expected results is the joint determination of adaptation measures to climate change during heat wave periods that preserve air quality. The health impact of each scenario (mitigation or adaptation) will be determined in terms of mortality and morbidity, with a particular focus on vulnerable people. New socio-economic results on the impact of air pollution and climate change and related policies on residential location choices will be obtained. In addition to specialized scientific publications, the results will be disseminated to a wide audience through various initiatives: courses, an interdisciplinary summer school, a science café, and interventions in the media.