The current and future anthropogenic-induced high-latitude warming will have global climatic implications due to polar ice mass loss, sea level rise and ocean circulation changes. However, uncertainty remains on future climate projections mainly due to an incomplete understanding of climate, cryosphere and carbon cycle feedback processes occurring at centennial to millennial- timescales. Progress can be achieved by exploring climate and environmental changes that occurred in the past. In the HOTCLIM project, we are studying past warm periods, also referred to as interglacials, which exhibit a polar warming comparable to that projected by 2100 due to specific combinations of orbital and CO₂ forcing. Especially, we are investigating the link between the carbon cycle dynamics and climate changes. To do so, we are combining (i) new analyses on the air trapped in Antarctic deep ice cores to inform on past changes in Antarctic climate and atmospheric CO2 concentrations (ii) climate and environmental data synthesis looking into the lower latitudes using terrestrial and oceanic archives (sea surface temperature, hydrological cycles, ocean circulation) (iii) an evaluation of outputs from climate models using the new comparison of the paleoclimatic datasynthesis and models output. The HOTCLIM project will improve our understanding of the natural climate variability and the processes involved during past periods associated with temperature changes comparable to projected future warming, hence helping improve climate projections

Here, we present the first results from the HOTCLIM project which is a multi-archive synthesis focused on the warm interval occurring between 190 and 243 ka BP, also refered to as Marine Isotopic Stage 7 (MIS 7). This warm period is of special interest because it follows the fastest transition between a cold (glacial) and a hot (interglacial) period of the last 800 000 ka, with a polar warming of 10 degrees in less than 5ka. We have compiled more than 30 oceanic cores, 9 speleothems and 3 ice cores covering the MIS 7 period. To compare them, we are now building a common chronology to these records. The use of combined continental (ice cores, speleothems) and oceanic (sediment cores) archives located on the whole surface of the Earth will allows to characterize (i) the amplitude and the temporal structure of the surface warming across the globe (ii) the contrast between oceanic and continental warming.

How to cite: Legrain, E., Capron, E., and Parrenin, F.: Toward an improved characterisation of climate and environmental changes during warm periods of the past: First results from the MOPGA HOTCLIM project , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12932, https://doi.org/10.5194/egusphere-egu21-12932, 2021.

A major cause of earth system model discrepancies result from processes that are missed or are incorrectly represented in the model's equations. Despite the increasing number of collected observations, reducing parametric uncertainties is still an enourmous challenge.

The process of relying on experience and intuition to find good sets of parameters, commonly referred to as "parameter tuning" keeps having a central role in the roadmaps followed by dozens of modeling groups involved in community efforts such as the Coupled Model Intercomparison Project (CMIP). 

In this work, we study a tool from the Uncertainty Quantification community that started recently to draw attention in climate modeling: History Matching also referred to as "Iterative Refocussing".

The core idea of History Matching is to run several simulations with different set of parameters and then use observed data to rule-out any parameter settings which are "implausible". Since climate simulation models are computationally heavy and do not allow testing every possible parameter setting, we employ an emulator that can be a cheap and accurate replacement. Here a machine learning algorithm, namely, Gaussian Process Regression is used for the emulating step. History Matching is then a good example where the recent advances in machine learning can be of high interest to climate modeling.

We investigate History Matching on a toy model: the two-layer Lorenz96, and share our findings about the challenges and opportunities of using this technique. We also discuss the use of this technique for realistic ocean models such as NEMO.

How to cite: Lguensat, R., Deshayes, J., and Balaji, V.: History Matching for parameter tuning: the Lorenz96 model as a case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7546, https://doi.org/10.5194/egusphere-egu21-7546, 2021.

There is a substantial gap between the current emissions of greenhouse gases and levels required for achieving the 2 and 1.5 °C temperature targets of the Paris Agreement. Understanding the implications of a temperature overshoot is thus an increasingly relevant research topic. We carry out a study as part of the “Achieving the Paris Agreement Temperature Targets after Overshoot (PRATO)” project of the MOPGA programme on the 2 °C overshoot of the Paris Agreement temperature target. We explore the carbon cycle feedbacks over land and ocean in the SSP5-3.4-OS overshoot scenario by using an ensemble of Coupled Model Intercomparison Project 6 Earth system models. Models show that after the CO₂ concentration and air temperature peaks, land and ocean are decreasing carbon sinks from the 2040s and become sources for a limited time in the 22^nd century. The decrease in the carbon uptake precedes the CO₂ concentration peak. The early peak of the ocean uptake stems from its dependency on the atmospheric CO₂ growth rate. The early peak of the land uptake occurs due to a larger increase in ecosystem respiration than the increase in gross primary production, as well as due to a concomitant increase in land-use change emissions primarily attributed to the wide implementation of biofuel croplands. The carbon cycle feedback parameters amplify after the CO₂ concentration and temperature peaks, so that land and ocean absorb more carbon per unit change in the atmospheric CO₂ change (stronger negative feedback) and lose more carbon per unit temperature change (stronger positive feedback) compared to if the feedbacks stayed unchanged. The increased negative CO₂ feedback outperforms the increased positive climate feedback. This feature should be investigated under other scenarios and reflected in simple climate models.

How to cite: Melnikova, I., Boucher, O., Cadule, P., Ciais, P., Gasser, T., Quilcaille, Y., Shiogama, H., Tachiiri, K., Yokohata, T., and Tanaka, K.: Carbon cycle response to temperature overshoot beyond 2 °C – an analysis of CMIP6 models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-819, https://doi.org/10.5194/egusphere-egu21-819, 2021.

Over recent years, climate change has become a global issue, leading political agendas and projecting onto almost every economic and development decision made today.  However, the way that we conduct climate science has remained broadly unchanged since the publication of the first IPCC report in 1990 - still relying on an ensemble of opportunity of climate models which doesn't allow for an estimation of high-impact tail risks and a highly idealized scenario framework which fails to test the fundamental technological assumptions which underpin our remaining pathways for achieving the Paris Agreement.  Here, we discuss how our strategy within the Make Our Planet Great Again "RISCCi" project is attempting to reframe the simulation of climate projections such as to provide better guidance for robust decision-making by categorizing the deep uncertainties of climate projections and mitigation pathways.  We present the initial results from an CNRM ensemble project which seeks to explore tail behaviour in climate feedbacks and impacts, and outline in a wider sense how future work and climate assessment needs to respond to the growing and evolving needs of a society as it works to minimise, and adapt to, climate change.

How to cite: Sanderson, B., Peatier, S., and Terray, L.: Retooling climate science for risk assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4435, https://doi.org/10.5194/egusphere-egu21-4435, 2021.

How to cite: Smerald, A., Kraus, D., Fuchs, K., Haas, E., Butterbach-Bahl, K., and Scheer, C.: Mitigation of greenhouse gas emissions from global croplands under a changing climate and increasing food demand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16433, https://doi.org/10.5194/egusphere-egu21-16433, 2021.

Greenhouse gas (GHG) metrics, that is, conversion factors to evaluate the emissions of non-CO₂ climate forcers on a common scale with CO₂, serve crucial functions upon the implementation of the Paris Agreement. While different metrics have been proposed, their economic cost-effectiveness has not been investigated under a range of pathways, including those temporarily missing or significantly overshooting the temperature targets of the Paris Agreement. Here we show that cost-effective metrics for methane that minimize the overall cost of climate mitigation are time-dependent, primarily determined by the pathway, and strongly influenced by temperature overshoot. The Paris Agreement will implement the conventional 100-year Global Warming Potential (GWP100), a good approximation of cost-effective metrics for the coming decades. In the longer term, however, we suggest that parties consider adapting the choice of common metrics to the future pathway as it unfolds, as part of the global stocktake, if cost-effectiveness is a key consideration.

How to cite: Tanaka, K., Boucher, O., Ciais, P., Johansson, D., and Morfeldt, J.: Cost-effective implementation of the Paris Agreement using flexible greenhouse gas metrics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13088, https://doi.org/10.5194/egusphere-egu21-13088, 2021.

In the Sahel food security has been a top development priority since the abrupt onset of persistent drought caught the region by surprise in the early 1970s, causing repeated recurrences of extreme food insecurity. Research ultimately demonstrated the global climate root of drought, going so far as to partially attributing persistence to anthropogenic emissions of aerosols and greenhouse gases. 

We exploit surveys collected in Senegal in the last 10 years to assess the year-to-year dynamics of household food security in relation to rainfall variability. We combine three variables from the household surveys, namely the Food Consumption Score, the Food Expenditure Share and the Reduced Coping Strategies Index, to explore the access dimension of food security. Cluster analysis on these three variables leads us to 1) classify households into categories of food security, and 2) discuss the response of each category of household to seasonality and year-to-year variability in climate. 

The UN World Food Programme and in-country partner institutions normally survey thousands of households every few years, in order to assess "baseline" (as opposed to "crisis") food security conditions. However, the years that Senegal households were surveyed in this most recent decade include 2014, a year of severe, national-scale drought. Comparison with the other, non-drought years allows to directly assess the shock from the perspective of the households themselves, and to describe coping mechanisms based on "baseline" food security category. We find that in the drought year (1) more of the “average rural” households that normally do not recur to coping strategies actually did, and (2) food expenditure share increases in all but one food security category.

How to cite: Giannini, A. and Ilboudo-Nébié, E.: Drought and food security in Senegal from the perspective of household access, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10246, https://doi.org/10.5194/egusphere-egu21-10246, 2021.

How to cite: Giordano, M. R., Bahino, J., Beekmann, M., and Subramanian, R. and the AfriqAir/MAQGA Team: MOPGA/Make Air Quality Great Again: AfriqAir and solution-oriented approaches to improving air quality in the Global South, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4975, https://doi.org/10.5194/egusphere-egu21-4975, 2021.

Changes in the surface ocean pH and temperature caused by the uptake of anthropogenic CO₂ are posing a threat to calcifying marine organisms. Recent studies have observed significant impacts on coral reef ecosystems with impaired carbonate skeletal growth and decreased calcification due to acidifying oceans. In situ measurements from buoys, ships, and remote observations by satellite of sea surface temperature, salinity, and ocean’s carbonate chemistry are sparse and only date back a few decades. The current coverage of observations for the northwestern Cuban coastal waters provides hence an incomplete picture of natural climate variability over interannual to interdecadal timescales, showing the need for high resolution climate archives.

Cuba is situated between densely populated landmasses of North and South America offering a unique environment to study multiple aspects of anthropogenic activity across the region as well as their interconnectivity.

A massive coral, Siderastrea siderea, from Cuba’s northwestern coast, was used as a natural archive to reconstruct bimonthly changes in SST, and carbonate chemistry through a multi-proxy approach since preindustrial times.

Preliminary results indicate a decrease in δ¹⁸O of 0.32 ‰ over 154 years since 1852,  indicating warming and/or freshening of the surface water over this period. Over the same time period, the δ¹¹B ratio decreased by ca. 1.6 ‰, translating into a decrease of 0.1 on the pH scale, reflecting the acidification of the northwestern Cuban coastal waters. Furthermore, an accelerating decrease of coral δ¹³C from the 1850s to 2005 of 1.5 ‰ demonstrates the anthropogenic imprint due to increased fossil fuel combustion. Further investigation and the comparison to trace elements indicate possible baseline shifts in regional seawater carbonate chemistry that have been affected by anthropogenic activity.

How to cite: Harbott, M., Wu, H., Kuhnert, H., Kasemann, S., Meixner, A., Jimenez, C., González-Diáz, P., and Rixen, T.: The anthropogenic environmental impacts and changes in the tropical Atlantic - a high resolution Cuban coral time series over 154 years, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12159, https://doi.org/10.5194/egusphere-egu21-12159, 2021.

The North Atlantic ocean is key to climate through its role in heat transport and storage, but the response of the circulation’s drivers to a changing climate is poorly constrained. The transparent machine learning method Tracking global Heating with Ocean Regimes (THOR) identifies drivers of circulation with minimal input: depth, dynamic sea level and wind stress. Beyond a black box approach, THOR's predictive skill is transparent. A dataset is created with features engineered and labeled by an explicitly interpretable equation transform and k-means application. A multilayer perceptron is then trained, explaining its skill using relevance maps and theory. THOR reveals a weakened circulation with abrupt CO₂ quadrupling, due to a shift in deep water formation areas and locations of the Gulf Stream and Trans Atlantic Current transporting heat northward. If CO₂ is increased 1% yearly, similar but transient patterns emerge. THOR could accelerate model analysis and facilitate process oriented intercomparisons.

How to cite: Sonnewald, M., Lguensat, R., and Balaji, V.: Revealing mechanisms of change in the Atlantic Meridional Overturning Circulation under global heating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6321, https://doi.org/10.5194/egusphere-egu21-6321, 2021.

CMIP5 models, including IPSL-5A, developed at the Institut Pierre Simon Laplace, largely reproduce the observed post-World War II decline in Sahel precipitation. We use all- and single-forcing historical simulations performed with IPSL-5A to better understand the impact of emissions of aerosols and greenhouse gases in Sahel drought. Specifically, we analyze the moisture budget to assess the two main processes, namely stabilization and moisture supply, that are hypothesized to shape moisture convergence and precipitation in the Atlantic sector.

1) The net change has the sign of the expected thermodynamic change: an increase in precipitation in GHG-induced warming, and a decrease in aerosol-induced cooling. Thermodynamic change is opposed by dynamical change.

The rainfall change in GHG-induced warming, in the Sahel as well as across all other regions of climatological precipitation, including the Atlantic Intertropical Convergence Zone (ITCZ), is positive and largely dominated by the change in the thermodynamic term associated with convergence, meaning that the change is consistent with an increase in moisture that assumes no change in the atmospheric circulation: as the ocean warms, it supplies more moisture to the monsoon.

This wetting thermodynamic term associated with convergence is opposed by drying associated with the corresponding dynamical term, which is especially strong at the margins, and signifies a weakened mass flux, or slow-down of the overturning circulation. This negative change in mass convergence is symptomatic of stabilization in a warmer world.

The effect of sulfate aerosol-induced cooling is equal and opposite to that of GHG-induced warming.

2) The ITCZ response is complicated by the dynamical ocean feedback associated with changes in the meridional gradient in sea surface temperature. GHG-induced warming leads not only to an increase in precipitation, but also to a poleward shift of the ITCZ. This poleward shift is accompanied by (south) westerly wind anomalies, which drive an off-equatorial cooling Ekman flow equatorward of the ITCZ. These same westerly anomalies induce a weakening of equatorial upwelling, and warming of the eastern equatorial Atlantic cold tongue.

Here, too, the effect of sulfate aerosol-induced cooling is equal and opposite to that of GHG-induced warming. An equatorward shift of the ITCZ is accompanied by (north) easterly wind anomalies, which drive off-equatorial warming, and equatorial cooling.

How to cite: Wenhaji Ndomeni, C. and Giannini, A.: Dynamical and Thermodynamic Changes in the Historical Response of Atlantic Sector Rainfall to Anthropogenic Emissions in the IPSL-5A Model., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15573, https://doi.org/10.5194/egusphere-egu21-15573, 2021.

Linking the Amazonian deforestation to changes in the hydrological cycle remains a puzzling question, addressed here through the use of recent global databases analyzing the relations between key hydro-climate variables (Precipitation (P), potential and actual evapotranspiration (PET and AET, respectively)), the surface water-energy balance and indices of forest cover change (regional forest loss ratio -RFL and regional non-forest vegetation ratio -RNF) for Southern Amazon (south of 8°S) and over the 1981-2018 period. The Southern Amazon constitutes a peculiar region due to specific climatic characteristics and shows a higher significant deforestation rate in comparison with the Northern Amazon. We further subdivided the study region into three subregions called Southern Bolivian Amazon (15° S‒21° S, 57° W‒70° W), Southern Peruvian Amazon (8° S‒15° S, 77° W‒65° W) and Southern Brazilian Amazon (8° S‒15° S, 65° W‒50° W). The surface water-energy balance is analyzed using a pixel-based Budyko-like theoretical framework approach, which discriminates energy-limited regions from water-limited regions. Southern Bolivian Amazon is shown to have undergone the strongest forest transition, becoming water-limited in conjunction with high forest loss. In this region, there is a significant relation between RFL values above 40%, P decrease, PET increases and AET decrease. These results suggest that areas with RNF values higher than 40% are prone to shift from an energy-limited to a water-limited state and remain trapped in this new state. Regions further north remain energy-limited due to minor P changes and even though significant increases in PET and decreases in AET are observed, associated with deforestation (high values RFL). This is typically the case in the ‘Arc of Deforestation’. In the Southern Bolivian Amazon, land use transition is associated with much larger changes from closed forest to a low-tree cover state as compared to regions further north - by at least a factor three as a proportion of area. Our findings indicate a clear link between hydro-climatic changes and deforestation, providing a new perspective on their spatial variability on a regional scale.

This research is part of the French AMANECER-MOPGA project.

How to cite: Wongchuig, S., Espinoza, J. C., Condom, T., Segura, H., Ronchail, J., Arias, P., Junquas, C., Rabatel, A., and Lebel, T.: A regional view of the linkages between hydro-climatic changes and deforestation in the Southern Amazon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9112, https://doi.org/10.5194/egusphere-egu21-9112, 2021.

Gradual anthropogenic warming and parallel changes in the major global biogeochemical cycles are slowly pushing forest ecosystems into novel growing conditions, with uncertain consequences for ecosystem dynamics and climate. Short-term forest responses (i.e., years to a decade) to global change factors are relatively well understood and skilfully simulated by land surface models (LSMs). However, confidence on model projections weaken towards longer time scales and to the future, mainly because the long-term responses (i.e., decade to century) of these models remain unconstrained. This issue limits confidence on climate model projections. Annually-resolved tree-ring records, extending back to pre-industrial conditions, have the potential to constrain model responses at interannual to centennial time scales. Here, we constrain the representation of tree growth and physiology in the ORCHIDEE global land surface model using the simulated interannual variability of tree-ring width and carbon (Δ¹³C) and oxygen (δ¹⁸O) stable isotopes in six sites in boreal and temperate Europe.  The model simulates Δ¹³C (r = 0.31-0.80) and δ¹⁸O (r = 0.36-0.74) variability better than tree-ring width variability (r < 0.55), with an overall skill similar to that of other state-of-the-art models such as MAIDENiso and LPX-Bern. These results show that growth variability is not well represented, and that the parameterization of leaf-level physiological responses to drought stress in the temperate region can be improved with tree-ring data. The representation of carbon storage and remobilization dynamics is critical to improve the realism of simulated growth variability, temporal carrying over and recovery of forest ecosystems after climate extremes. The simulated physiological response to rising CO2 over the 20th century is consistent with tree-ring data in the temperate region, despite an overestimation of seasonal drought stress and stomatal control on photosynthesis. Photosynthesis correlates directly with isotopic variability, but correlations with δ¹⁸O combine physiological effects and climate variability impacts on source water signatures. The integration of tree-ring data (i.e. the triple constraint: width, Δ¹³C and δ¹⁸O) and land surface models as demonstrated here should contribute towards reducing current uncertainties in forest carbon and water cycling.

How to cite: Barichivich, J., Peylin, P., Daux, V., Risi, C., Jeong, J., Luyssaert, S., and Launois, T.: Developing a triple tree-ring constraint for tree growth and physiology in a global land surface model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13546, https://doi.org/10.5194/egusphere-egu21-13546, 2021.

Soil carbon (C) models are used to predict C sequestration responses to climate and land use change. Yet, the soil models embedded in Earth system models typically do not represent processes that reflect our current understanding of soil C cycling, such as microbial decomposition, mineral association, and aggregation. Rather, they rely on conceptual pools with turnover times that are fit to bulk C stocks and/or fluxes. As measurements of soil fractions become increasingly available, it is necessary for soil C models to represent these measurable quantities so that model processes can be evaluated more accurately. Here we present Version 2 (V2) of the Millennial model, a soil model developed in 2018 to simulate C pools that can be measured by extraction or fractionation, including particulate organic C, mineral-associated organic C, aggregate C, microbial biomass, and dissolved organic C. Model processes have been updated to reflect the current understanding of mineral-association, temperature sensitivity and reaction kinetics, and different model structures were tested within an open-source framework. We evaluated the ability of Millennial V2 to simulate total soil organic C (SOC), as well as the mineral-associated and particulate fractions, using three independent data sets of soil fractionation measurements spanning a range of climate and geochemistry in Australia (N=495), Europe (N=176), and across the globe (N=716). Considering RMSE and AIC as indices of model performance, site-level evaluations show that Millennial V2 predicts soil organic carbon content better than the widely-used Century model, despite an increase in process complexity and number of parameters. Millennial V2 also reproduces between-site variation in SOC across gradients of climate, plant productivity, and soil type. By including the additional constraints of measured soil fractions, we can predict site-level mean residence times similar to a global distribution of mean residence times measured using SOC/respiration rate under an assumption of steady state. The Millennial V2 model updates the conceptual Century model pools and processes and represents our current understanding of the roles that microbial activity, mineral association and aggregation play in soil C sequestration.

How to cite: Abramoff, R., Guenet, B., Zhang, H., Georgiou, K., Xu, X., Viscarra-Rossel, R., Yuan, W., and Ciais, P.: Site-level simulations of measurable soil fractions with the Millennial V2 soil model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9795, https://doi.org/10.5194/egusphere-egu21-9795, 2021.

Cooperation between countries in managing and protecting shared marine resources is beneficial both ecologically and economically, but how best to establish the cooperation needed at a global scale is under constant evolution. Here, we used hydrodynamic modelling to identify ecologically connected networks of marine reserves and evaluated these networks with socio-economic indicators. We found that 17% (11/66) of the largest networks (>20 reserves) span multiple countries and are part of a heterogeneous networks. The countries involved in the heterogeneous networks have different economic, political, and cultural views. Most of the networks currently are homogenous and have similar levels of development, shared languages, and other cultural values. While economic and cultural homogeneity might lead to more efficient ecological management in the short term, heterogeneous networks may prove to be more resilient in the longer term, once climate change has impacted marine connectivity. 

How to cite: McDowell, J.: Low economic, political, and cultural diversity within the largest global networks of marine reserves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8540, https://doi.org/10.5194/egusphere-egu21-8540, 2021.

The `eddying' ocean, recognized for several decades, has been the focus of much observational and theoretical research.  We here describe a generalization for the analysis of eddy energy, based in the use of ensembles, that  addresses two key related issues: the definition of an `eddy' and the general computation of energy spectra. An ensemble identifies eddies as the unpredictable component of the flow, and permits the scale decomposition of their energy in inhomogeneous and non-stationary settings. It also avoids the `tapering' or `windowing' of the data required by traditional approaches. We apply the analysis to a mesoscale resolving  (1/12 degree) ensemble of the separated North Atlantic Gulf Stream. Our results show that the eddies are consistent with the theoretical predictions of quasi-geostrophy both at the surface and ocean interior. 

How to cite: Dewar, W. K., Jamet, Q., Uchida, T., and Poje, A.: An ensemble-based eddy and spectral analysis, with application to the Gulf Stream, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2447, https://doi.org/10.5194/egusphere-egu21-2447, 2021.

With the advent of high-performance computing, we are now capable of simulating the ocean and climate system on decadal to centennial timescales. However, global and basin-scale simulations still lack the spatial resolution necessary to resolve the mesoscales (hereon referred to as mesoscale-permitting simulations), a scale roughly on the order of O(100 km). Here, we provide a first step towards a potential vorticity (PV) based mesoscale closure scheme in order to improve the representation of mesoscale eddies in such simulations by taking advantage of the thickness-weighted averaged (TWA) framework. In the TWA framework the total eddy feedback can be encapsulated in the Eliassen-Palm (E-P) flux divergence. This implies that mesoscale closure schemes aimed at representing the total eddy feedback should therefore be representing the E-P flux divergence. The TWA framework further elucidates that its divergence is equivalent to the eddy Ertel PV flux. In other words, if one is to parametrize the eddy Ertel PV flux, one has parametrized the total eddy feedback onto the mean flow. Using a 1/12° North Atlantic ensemble simulation with 24 members, which allows us to decompose the mesoscale variability from the forced dynamics, we show that the eddy Ertel PV flux can be related to the local-gradient of mean Ertel PV as an active tracer via an anisotropic eddy diffusivity tensor. What follows is that not only does the tensor bring together the isopycnal thickness skew diffusivity and isopycnic tracer diffusivity, the former known as the Gent-McWilliams (GM) parametrization and latter the Redi parametrization, but also incorporates the eddy momentum fluxes. Although the Redi parametrization has existed longer than GM, there has been much more development in the latter, leaving the Redi diffusivity poorly constrained. Being able to treat GM and Redi simultaneously is another strength of our framework.

How to cite: Uchida, T., Jamet, Q., Dewar, W., Balwada, D., Le Sommer, J., and Penduff, T.: Towards a potential vorticity based mesoscale closure scheme, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-70, https://doi.org/10.5194/egusphere-egu21-70, 2020.

Ensemble simulations are becoming more and more popular in oceanography. Among other advantages, this modeling strategy elevates the number of dimensions available to apply statistics, and then offer new opportunities to disentangle small scale ocean turbulence from the larger scale (ensemble mean) flow, as well as their interactions. In such a framework, ocean turbulence is usually defined as the ensemble spread, reflecting the intrinsic variability that spontaneously emerges from the ocean, while the larger scale flow is defined as the ensemble mean, and whose variability is controlled by the forcing. Here, we aim at leveraging results of recently produced, submesoscale-permitting (1/60^o) ensemble simulations of a forced ocean model configuration of the western Mediterranean Sea (MEDWEST60, 20 members) to diagnose the role played by ocean turbulence in the Kinetic Energy (KE) budget of these simulations. We develop for this purpose offline tools to compute such budget based on the NEMO modeling platform, which we aim at presenting.

These offline tools are part of the CDFTOOLS, a FORTRAN based package developed to export the NEMO code into an offline version of it for post-processing. Our contributions have been to include the momentum budget of the code into this package, on which kinetic energy builds upon. We first evaluate the accuracy of these offline computations against online estimates over a short period of time. At the model time step, this accuracy reaches  up to 10^-3 -10^-4 for time rate of change, advection and pressure work, and 10^-1 for vertical dissipation. The surface pressure correction associated with the time-splitting scheme has proven difficult to implement offline, due to 1/ sub-domain boundaries instabilities in the computation of the barotropic mode, and 2/ replication of the interpolation scheme used in NEMO for atmospheric forcing fields (atmospheric surface pressure, evaporation, precipitations, runoff). The use of one hour model outputs is found to degrade the accuracy of the offline estimates by up to one order of magnitude locally. We then present and discuss preliminary applications of these diagnostics to the MEDWEST60 ensemble simulation model outputs (hourly averages).

How to cite: Jamet, Q., Dewar, W. K., Penduff, T., Le Sommer, J., Leroux, S., Molines, J.-M., and Gula, J.: Analyzing the Kinetic Energy budget of submesoscale-permitting ensemble simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13127, https://doi.org/10.5194/egusphere-egu21-13127, 2021.

We develop a parsimonious model-data fusion to capture the groundwater contribution to stream discharge and its effect on variable transit times. The modeling strategy relies on partitioning infiltration between 1) Boussinesq groundwater flows in shallow aquifers and 2) fast flows close to the surface. Partitioning is controlled by the relative aquifer saturation inducing groundwater return flows and fast flows on saturated soils. Flowpaths are computed with a new 2D particle tracking algorithm to obtain transient transit time distributions. Hydraulic conductivity, total and drainable porosities are constrained through a sequential calibration strategy based on discharge time series and point-based CFC tracer data. Application on a 43 km2 catchment in Brittany (France) highlights the important contribution of old groundwater flow dynamics to streamflow's transit time distributions in all seasons under temperate climate conditions. The calibrated model succeeds in reproducing CFC-based groundwater ages as well as discharge dynamics at the outlet of the catchment. Slow groundwater circulation (baseflow and return flow) represents ca. 75% of the streamflow with strong seasonal variations (between 40 and 95%). Mean transit times are ca. 13 years, varying between 5 and 20 years, inversely proportional to the groundwater contribution. These seasonal variations are dominantly due to the flow partitioning between the aquifer and soil compartments with a second-order contribution of the groundwater transit times stratification.

How to cite: Marçais, J., Derry, L. A., Guillaumot, L., Aquilina, L., and de Dreuzy, J.-R.: Partitioning fast flow from stratified groundwater flow modulates seasonal variations of old streamwater transit times, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16207, https://doi.org/10.5194/egusphere-egu21-16207, 2021.

Reducing greenhouse gas emissions, and in particular fossil carbon dioxide, is essential to sustain future human life on Earth. In this perspective, residual biomass becomes a potentially valuable resource to substitute fossil carbon, in particular when considered under the angle of national strategic planning. Yet, diverting this flow from its current (or baseline) use implies ensuring a net societal benefit, i.e. an overall enhanced environmental and economic performance. Here, we present an assessment covering the whole of France. The purpose of our study is three-fold: (i) providing and demonstrating a methodology for high-resolution spatial quantification of key residual biomass streams including Primary Forestry Residues (PFR), Agricultural Residues (crop residues, manure, prunings), Sewage Sludge, Garden Waste, Food waste (household, industrial); (ii) identifying the current use of these streams and (iii) quantifying, by life cycle assessment, the environmental impacts related to this baseline management. The vision is to supply the quantified minimal environmental performance that future bioeconomy uses of the residual biomasses must have in order to generate an overall improvement compared to today’s baseline. The aim is additionally to develop methods that can be reproduced and used for strategic circular- and bioeconomy planning in other countries (or regions) worldwide.

According to our results, the total biophysical available potential (in PJ y^-1) is: PFR: 158 PJ y^-1 [83-261]; Crop residues: 1178 PJ y^-1 [988-1369]; Manure: 433 PJ y^-1 [345-520];  pruning residues: 57 PJ y^-1 [30-85]; garden waste: 61 PJ y^-1 [49-73];  household biowaste currently separately collected: 103 PJ y^-1 [83-124]; household biowaste not collected today: 89 PJ y^-1 [81-97]; agri-industrial biowaste: 81.4 PJ y^-1 [65-98]; sewage sludge: 15.2 PJ y^-1 [12-18]. This totals ~2100 PJ y^-1, the equivalent of 20% of the primary energy supply in France. The current uses vary among the streams, including on-land decay, open-air burning, domestic heat use, direct use as organic fertilizer, use as organic fertilizer after composting or use as bedding, production of heat and power following biogas production through anaerobic digestion, mulch production and incineration amongst the most common ones. When services are supplied (e.g. heat, electricity, fertilizers), the life cycle assessment considered the avoided impacts induced by the substituted products (e.g. natural gas, mineral fertilizers).

To our knowledge, such a wide platform covering as many residual streams at this level of spatial resolution (from 10-m to the European NUTS-3 level), incorporating uncertainties and life cycle inventories on the current uses of streams, has never been elaborated until now.

How to cite: Hamelin, L. and Karan, S.: The role of residual biomass in the French transition towards low fossil C use: spatial quantification, current uses, and life cycle assessment of the baseline, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16493, https://doi.org/10.5194/egusphere-egu21-16493, 2021.

Continued fossil fuel burning is likely to increase CO2 concentrations in the atmosphere to previously unknown levels and emissions will continue to outpace uptake, unless limiting action is taken. This paper presents new approaches to mitigate emissions and drawdown atmospheric CO2 , that is, new combinations of developing and existing technologies in offshore settings. We consider the permanent and safe geological storage of carbon dioxide (CCS) through in situ carbon mineralization and the potential for CO2  uptake and disposal in offshore basalt formations. The CCS concept in general aims to separate CO2 from industrial emissions, and/or directly remove it from the air, and permanently store it underground. Integrating these technologies with renewable (wind) energy in offshore settings may offer a scalable, long-term climate mitigation choice that warrants early consideration. Current studies of co-located opportunities and new offshore demonstration projects are considered. 

How to cite: Goldberg, D.: Disposing of CO2 in basaltic rocks:  opportunities to upscale storage and co-locate sites with offshore renewable (wind) power , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3373, https://doi.org/10.5194/egusphere-egu21-3373, 2021.

The project, PYROKINE, aims at developing new modeling approaches adapted to one of the most promising thermochemical processes, fast pyrolysis, applied to the conversion of contaminated lignocellulosic biomass. The fast pyrolysis converts solid biomass into volatiles and a limited amount of char. The volatiles are then rapidly quenched resulting in a high yield of bio-oil, 70-75wt% of the starting material on a dry basis. The liquified biomass can be further upgraded catalytically or blended to produce new advanced biofuels. In addition to the yield, the product distribution determines their quality, and this is critically dependent on biomass type and its temperature-time history. In the present study, we propose to establish a dynamic model adaptable to the conversion of different biomass types under various pyrolysis regimes according to two research programs.

The first program consists of integrating coupled chemical kinetics into heat and mass transfer models for biomass fast pyrolysis. So far, the coupled kinetic model combining the Friedman isoconversional method with a Distributed Activated Energy Model (DAEM) has been developed and validated with a set of experimental data obtained under slow heating conditions. The apparent activation energy, Eα, one of the kinetic parameters that describes the overall reactivity of the feedstock, has been plotted versus the extent of conversion, α, to assess the chemical complexity of the reaction. For example, the lignin was found to degrade into two successive stages from 174 to 280kJ/mol between 0.05<α<0.60 and up to 322kJ/mol until α=0.85. Two kinetic parameter datasets were derived and used as inputs for the double-Gaussian DAEM that successfully fitted experimental curves. This chemical kinetic model will be combined with heat and mass transport models according to the type of thermal regimes.

The second program focuses on the thermodynamic and kinetic modeling of the intermediate liquid compound in the presence of metallic species. This liquid appears in the early stages of the fast pyrolysis and results from the softening of biomass. Its physico-chemical characteristics are the origin of the multiphasic nature of the biomass fast pyrolysis. A preliminary study has allowed the development of a thermodynamic model and headspace coupled to gas chromatographic methods to predict the vapor-liquid equilibrium for model liquid mixtures. The system studied was a closed system with air and a solution mixture of five components (acetic acid, hydroxyacetone, phenol, furfural, and methanol) near its boiling point, 90°C, and under atmospheric pressure. To predict the thermophysical parameters of the solution, the Soave-Redlich-Kwong (SRK) equation of state coupled with Modified Huron-Vidal (MHV2) mixing rules incorporating the UNIversal Functionnal Activity Coefficient (UNIFAC) model was implemented. Concentration measurements in vapor and liquid phases were compared to vapor-liquid equilibrium data. A quantitative agreement between simulated and measured concentrations in the liquid phase was achieved with this combined state-predictive model of the SRK-MHV2-UNIFAC model, confirming that it accounts well for the nonidealities. This thermodynamic model will need to be coupled with a chemical kinetic model in the presence of inorganics to reveal the role of those contaminants on the chemistry.

How to cite: Carrier, M., Nasfi, M., Ajam, M., Cassayre, L., and Salvador, S.: Biomass fast pyrolysis: Chemistry and thermodynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2878, https://doi.org/10.5194/egusphere-egu21-2878, 2021.

Nowadays, climate change is a reality because energy demand is mostly satisfied by fossil fuels which are limited resources and also responsible for greenhouse gas emissions. Actions have to be undertaken to overcome this issue. Among the solutions proposed to this is the development and use of new energy sources called renewable energies. By renewable energy, we understand energies coming from the sun, wind, geothermal, water, or biomass. Of these, solar energy is one of the most abundant, clean, effective, and easily deployed. One of the efficient ways to exploit solar energy is photovoltaics.

Two decades of research have allowed organic photovoltaics to appear today as an alternative to their conventional and inorganic counterparts. However, several issues have to be addressed in order to ease their production on an industrial level. Bulk heterojunction (BHJ) solar cells based on the blend of two types of conjugated molecules acting as an electron donor (hole transport) and an electron acceptor (electron transport) are the most efficient organic solar cells. Further, using non-fullerene acceptors (or NFA) in these BHJ solar cells have recently gained a broad interest due to their great potential to realize high conversion efficiencies (more than 18%) with a long lifetime over the conventional polymer/fullerene blend solar cells.

Here we provide an overview of the recent progress of different existing and growing photovoltaic technologies. We also provide prospects for the future development of organic photovoltaic devices.

How to cite: Tchognia Nkuissi, H., Labiod, A., Ferry, S., Lévêque, P., and Heiser, T.: Organic photovoltaics as a solution to overcome growing atmospheric carbon emissions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5879, https://doi.org/10.5194/egusphere-egu21-5879, 2021.

In the 21st century, where problems related to the city are legion (climate change, disease, depression, crime, etc.), urban ecology promises to provide concrete and effective solutions to enable humanity to live and the planet to breathe.

In a southern metropolis such as Algiers, these seemingly endless urban problems are becoming more acute due to a galloping population and an unbridled expansion of the urban fabric. This expansion is often at the expense of green spaces.

In this way, we worked on methodologies that will enable us to quantify the layout, condition and influence of these green spaces and to develop more appropriate management plans to optimize there functions.

We also carried out a preliminary study for the landscape analysis and spatialization of urban plants, to be able to deepen the study later and create an interrogative spatial database to help decision-making.

How to cite: Ighil agha, B.: urban vegetation of algiers : urban ecology approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6551, https://doi.org/10.5194/egusphere-egu21-6551, 2021.