In AD 1755 a strong earthquake-generated tsunami destroyed large parts of the southwest Iberian coastline. Data for the study of the sedimentological characteristics and palaeo-ecological effects of the backwash of this well-known AD 1755 Lisbon tsunami and possible preceding events on the continental shelf was obtained during RV METEOR cruise M152 in November 2018, since the hydrodynamics of tsunami backwash currents are as yet poorly understood. Furthermore, the suitability of the shelf as a reliable sedimentary archive for tsunami deposits was investigated. Along the Algarve coast, prominent AD 1755 Lisbon tsunami deposits have been detected onshore for quite some time. Cruise M152 conducted a geophysical survey on the corresponding shelf area to obtain bathymetry and sub-bottom profiles for the recognition of depositional basins. Subsequently, 19 sediment cores were retrieved from the most suitable depositional basins by vibracoring at water depths from 65 to 114 m. The cores were analysed in a multiproxy approach (granulometry, magnetic susceptibility, P-wave velocities, organic and inorganic geochemistry, micropalaeontology). Deposits of the AD 1755 Lisbon tsunami were identified in most of the cores as a thin layer at ca. 20 cm depth. More surprisingly, a second event deposit dating to ca. 3700 years cal. BP was detected at core depths of 122 to 155 cm. It is even traceable in the sub-bottom profiles and consists of a distinctive ca. 30 cm thick well sorted medium-sized siliciclastic sand. Due to the thickness of the deposit an in-depth study of its characteristics was possible. It displays an erosive basal contact followed by a thin matrix-poor shell hash layer, a reversely graded fine sand layer and ultimately a massive, quite homogeneous medium sand resembling the Ta division of the Bouma sequence or the S1, S2 and S3 divisions of the Lowe sequence. The deposit is distinguishable from the silt to silty sand-dominated background sedimentation not only due to the textural and compositional features, but also due to contrasting geophysical and geochemical properties. Terrestrial provenance for (at least parts of) the sediment is revealed by biomarker analysis. Based on these characteristics, the deposit is interpreted as the result of a high density hyperpycnal flow from the coast towards the offshore caused by tsunami backwash. This event layer may be correlated to onshore observations of tsunami deposits along the southwest coast of Spain but has never been identified in Portugal where the onshore record of tsunami deposits only covers the last three millennia. The results of this multiproxy analysis strongly suggest the shallow offshore area below storm wave base to host reliable sedimentary archives for tsunami backwash deposits, which allow the discovery of as yet unknown events. Palaeotsunami research can benefit from the investigation of offshore archives, especially where onshore records are incomplete or sparse.
Precaspian basin is the most petroliferous basin in Kazakhstan with more than 100 years of history of the oil and gas industry. The economy of the country has been depending on the revenues coming from the sale of Precaspian oil. Nevertheless, the average oil recovery rate in the country remains low around 30-35% and its government planned to increase the recovery rate to 55-60%. The high oil recovery rate could be achieved by enhanced oil recovery (EOR) methods by injecting diverse inert gases and liquids. The global challenge of excessive CO2 emissions makes an EOR with CO2 injection (CO2-EOR) a good candidate because the anthropogenic CO2 emission could be a good source of the injection gas. Depleted oil reservoirs are the first targets for the implementation of carbon storage. The basin contains 178 oil and gas fields distributed in pre-salt and post-salt sections divided by the huge Kungurian salt bed that deformed into domes throughout the basin. A set of suitable reservoir parameters (Original Oil In Place (OOIP), depth, API, pressure, porosity, permeability, initial oil saturation) for CO2-EOR have been identified by earlier works of researchers based on previous experience of the petroleum industry and used to screen the oil reservoirs of the Precaspian basin. Thirty-four reservoirs of the basin were identified to be suitable for CO2-EOR or CO2 storage. The effective CO2 storage capacity of the reservoirs has been estimated using the Carbon Sequestration Leadership Forum (CSLF) method. The previous estimation of the storage capacity of 178 reservoirs was 179.2 Mt of CO2 however, after the CO2-EOR screening, the capacity decreased to 24.4 Mt. The mapping of CO2 sources and investigation of CO2 amount released from each CO2 source in the Precaspian basin will contribute to the CO2 source-CO2 sink matching to decide the most feasible CCS options. In addition, the analysis of fault intensity and seismicity in suitable reservoir-seal pairs could have important implications for the safety of CO2 storage.
Geodynamic models for continental collision require information on rock density and rheology as they evolve during the subduction-eduction cycle. The Western Gneiss Complex (WGC) in the Scandinavian Caledonides represents continental lithosphere that underwent transient subduction during the Scandian collision. Preservation of eclogite facies mineral parageneses in the predominant granitoid gneisses is rare due to amphibolite-facies overprinting and partial melting. However, rocks in the Dalsfjord area of the southern WGC underwent a lower-T, HP eclogite facies metamorphism and lie outside the realm of migmatisation in the higher-T, UHP domains further north. Grey bt+pl+qz+ep±grt±Ca-amp orthogneisses enclose areas of green, omphacite-bearing granitoid gneiss. These evolved from a dry, charnockitic precursor to omp+grt+czo+ky+qz+rt±pg±phe. They are L>S tectonites with a strong omphacite-aggregate shape fabric. Peak P-T was∼650C at 2.3GPa. Density of the omphacite gneiss under these conditions was calculated at ∼3.2 g.cm−3 based upon the estimated mineral mode and pseudosection analysis. This would have been neutrally or slightly positively buoyant relative to anhydrous lithospheric mantle but negatively buoyant relative to a serpentinised mantle wedge. If this applied through a large enough rock volume it could have aided subduction or at least retarded buoyant uprise of the WGC during the early stages of the collision cycle.
Atmospheric chemistry models are a central tool to study the impact of chemical constituents on the environment, vegetation and human health. These models split the atmosphere in a large number of grid-boxes and consider the emission of compounds into these boxes and their subsequent transport, deposition, and chemical processing. The chemistry is represented through a series of simultaneous ordinary differential equations, one for each compound. Given the difference in life-times between the chemical compounds (milli-seconds for O (sup 1) D (Deuterium) to years for CH4) these equations are numerically stiff and solving them consists of a significant fraction of the computational burden of a chemistry model. We have investigated a machine learning approach to emulate the chemistry instead of solving the differential equations numerically. From a one-month simulation of the GEOS-Chem model we have produced a training dataset consisting of the concentration of compounds before and after the differential equations are solved, together with some key physical parameters for every grid-box and time-step. From this dataset we have trained a machine learning algorithm (regression forest) to be able to predict the concentration of the compounds after the integration step based on the concentrations and physical state at the beginning of the time step. We have then included this algorithm back into the GEOS-Chem model, bypassing the need to integrate the chemistry. This machine learning approach shows many of the characteristics of the full simulation and has the potential to be substantially faster. There are a wide range of application for such an approach - generating boundary conditions, for use in air quality forecasts, chemical data assimilation systems, etc. We discuss speed and accuracy of our approach, and highlight some potential future directions for improving it.
Speleothems are important archives for paleo environments thanks to their high temporal resolution and potential for precise and accurate dating. Organic biomarkers in speleothems are not widely explored because of low concentrations and high sample amount required to obtain detectable levels. The potential for paleoenvironmental reconstruction from organic molecules in speleothems is high, but low contamination and high sensitivity analytical tools are required to obtain well resolved and reliable records.
In our study, we will assess the performance of different ionosphere models based on the comparison with measurements. Both, physics based models and empirical models will be tested, to demonstrate and compare their different capabilities. As representatives, we are using the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model, the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) and the “TUM-Model”.
Glaciers distinct from the Greenland and Antarctic ice sheets cover an area of approximately 706,000 square kilometres globally 1 , with an estimated total volume of 170,000 cubic kilometres, or 0.4 metres of potential sea-level-rise equivalent 2 . Retreating and thinning glaciers are icons of climate change 3 and affect regional runoff 4 as well as global sea level 5 , 6 . In past reports from the Intergovernmental Panel on Climate Change, estimates of changes in glacier mass were based on the multiplication of averaged or interpolated results from available observations of a few hundred glaciers by defined regional glacier areas 7 – 10 . For data-scarce regions, these results had to be complemented with estimates based on satellite altimetry and gravimetry 11 . These past approaches were challenged by the small number and heterogeneous spatiotemporal distribution of in situ measurement series and their often unknown ability to represent their respective mountain ranges, as well as by the spatial limitations of satellite altimetry (for which only point data are available) and gravimetry (with its coarse resolution). Here we use an extrapolation of glaciological and geodetic observations to show that glaciers contributed 27 ± 22 millimetres to global mean sea-level rise from 1961 to 2016. Regional specific-mass-change rates for 2006–2016 range from −0.1 metres to −1.2 metres of water equivalent per year, resulting in a global sea-level contribution of 335 ± 144 gigatonnes, or 0.92 ± 0.39 millimetres, per year. Although statistical uncertainty ranges overlap, our conclusions suggest that glacier mass loss may be larger than previously reported 11 . The present glacier mass loss is equivalent to the sea-level contribution of the Greenland Ice Sheet 12 , clearly exceeds the loss from the Antarctic Ice Sheet 13 , and accounts for 25 to 30 per cent of the total observed sea-level rise 14 . Present mass-loss rates indicate that glaciers could almost disappear in some mountain ranges in this century, while heavily glacierized regions will continue to contribute to sea-level rise beyond 2100.
Some organic pollutants found in soils, like the herbicide 2,4-D, are very mobile and can easily infiltrate, reach the underground water and spread more broadly in the environment. The degradation of these pollutants during their lixiviation through soil is a critical point to understand. This degradation starts with the encounter between the pollutant and the degrading agent, that are mainly bacterial endoenzymes in the case of 2,4-D. Encounter, and thus spatial distributions of bacteria and pollutants, appear to be particularly relevant in soils, where these distributions can be highly heterogeneous and sparse. This leads us to wonder how the macroscopic spatiotemporal distributions of bacteria and their substrate impact their encounter and thus pollutant degradation. It is often assumed that the dispersion of bacteria and their substrate in soil eventually promotes their encounter. But the validation and the fine understanding of this assumption, especially of how this encounter is shaped by the interaction between transport processes and bacterial metabolism, is still unclear. We use this assumption as our working hypothesis. We develop several reactive transport models at mm-to-cm scale (Babey et al., 2017), in a considered homogeneous medium, aimed at investigating the impacts of initial localizations (mainly co-localization) and concentrations of 2,4-D and its bacterial degraders on 2,4-D biodegradation, under several transport processes (diffusion and advection) and biochemical processes (sorption and microbial metabolism). These models are built and calibrated on cm-scale experiments performed on the degradation of 2,4-D spots in natural repacked soil cores without dispersion of bacteria (Pinheiro et al., 2015), and compared to homologous experiment with dispersion of bacteria (Pinheiro et al., 2018). Contrary to our hypothesis, we show through modeling that dispersion of bacteria and substrate decreases their encounter in many cases. This is caused by the immediate, continuous, and strongly adverse effect of substrate dilution. We show that dispersion promotes encounter in some very specific cases, when an inversion of substrate gradient occurs, that is when the effect of dilution is at least counterbalanced by a decrease of spatial competition of bacteria for substrate. Whether bacteria dispersion promotes or not encounter strongly depends on the interplay between transport processes and metabolism. We also show that the positive effect of dispersion on encounter is theoretically limited, and that in some experiments it is not high enough to explain the observed increase of pollutant biodegradation caused by bacteria dispersion. This points out that dispersion can act also through processes other than encounter between bacteria and their substrate. One of these processes could be spatial inhibition between bacteria. References Babey T, Vieuble-Gonod L, Rapaport A, Pinheiro M, Garnier P, de Dreuzy J-R. Spatiotemporal simulations of 2,4-D pesticide degradation by microorganisms in 3D soil-core experiments. Ecol Model. 2017 Jan;344:48–61. Pinheiro M, Garnier P, Beguet J, Martin Laurent F, Vieuble Gonod L. The millimetre-scale distribution of 2,4-D and its degraders drives the fate of 2,4-D at the soil core scale. Soil Biol Biochem. 2015 Sep;88:90–100
The impact of the Drake Passage (DP) opening on climate is being debated for dozens of years. Indeed, being one of the major geographical changes occurring during the Eocene and at the beginning of a global climate cooling, it has often generated a lot of interest. To date, even though the overall signal remains unclear, it is considered as one of the main potential cause of the contemporaneous climate change. Several model studies have been aiming to assess the importance of this gateway opening through different more or less complex models. However, according to our knowledge on palaeoenvironments, most of them considered unrealistic boundary conditions (notably a low pCO2 or a today-like geography) that might corrupt the transposition of their results to the original deep-time context. In order to better understand if and how climate might have been affected by this gateway opening the DP question is here evaluated using an up2date IPCC like model, the IPSL-CM5A2, and Eocene-friendly boundary conditions (1120ppm, 40Ma land-sea distribution including an open Panama Seaway). Four simulations have been performed using a closed Drake configuration and different DP depths 100m, 300m and 1000m. Striking changes are visible, since the earliest changes of the gateway opening, in the oceans dynamics and the Southern Ocean properties. However, the Drake throughflow remains weak, by far less intense than a mature Antarctic Circumpolar Current and effects on temperatures remain geographically constrained. These experiments should help to understand if the impact of the DP was progressive or rather non linear while the passage deepened. Our results are compared to Neodymium and d13C data and discussed in the broader context of the Eocene-Oligocene climatic transition.
Predicting the evolution of nitrate pollution at the catchment scale implies a global evaluation of residence times and denitrification rates in the aquifer. Data acquired in wells only result from processes occurring in their capture zone and are rarely representative of the whole aquifer [1]. Stream data, on the opposite, integrate the processes occurring along all contributing groundwater flowpaths and thus could be more relevant for upscaling. But stream signal is also controlled by soil, hyporheic zone and in-stream processes. Here we investigate the possibility of extracting groundwater signature from such a complex stream signal. In-stream spatially-distributed measurements were performed during low flow over a 35 km2 crystalline agricultural catchment in Brittany, Western France. Groundwater inputs into the streams were localized and quantified using radon mass balance. In conjunction with radon, dissolved gases (O2, CO2, N2, N2O, CH4, Ar), wet chemistry and nitrate isotopes were measured at each site. Quantification of in-stream processes was further realized by performing tracer injections in three selected reaches. Injections were coupled with continuous in-situ measurement of dissolved gases using membrane inlet mass spectrometry (MIMS). Helium injections allowed to calculate gas exchange rates, while nutrient injections (acetate, nitrate) allowed to characterize in-stream biological activity (oxygenic respiration, denitrification). Radon mapping reveals a high localization degree of groundwater inputs into the streams. Groundwatersurface water exchanges are strongly concentrated after a major topographic slope that separates two geological units, showing that geomorphology is a major control of hydrogeological circulations. These results are consistent with a 3D-groundwater flow model of the catchment calibrated with age tracer data acquired in wells [1]. Close to groundwater input zones, stream chemistry is strongly impacted by groundwater signature. Helium and nutrient injections evidence that gas exchanges between stream and atmosphere constitute the main eraser of groundwater signature as water is flowing dowstream. Groundwater signature is lost specifically at highly turbulent sites, such as small cascades, where measured gas exchange rates are one to two orders of magnitude higher than in calm reaches. [1] Kolbe, T., J. Marcais, Z. Thomas, B. W. Abbott, J. R. de Dreuzy, P. Rousseau-Gueutin, L. Aquilina, T. Labasque & G. Pinay, 2016. Coupling 3D groundwater modeling with CFC-based age dating to classify local groundwater circulation in an unconfined crystalline aquifer. Journal of Hydrology 543:31-46 doi:10.1016/j.jhydrol.2016.05.020.
Transport through 2D correlated porous media has been shown to induce mixing through deformation of material elements owing to the heterogeneity in the flow fields [1]. The stretching of line elements brings about an increase in the area for reaction and increases the diffusive flux through the thinning of the direction transverse to stretching and is thought to be an important mechanism to determine hotspots of mixing in various flow conditions [2]. These mechanisms are useful to quantify the extent of reaction for fast reactive fluids wherein the local reactivity may be obtained through the information gained from the gradient maps of a conservative tracer. Unlike earlier works which have primarily focussed on a Lagrangian approach for quantifying dispersion, we attempt to establish the dispersion rates in the transport through a porous media by means of fully resolved Eulerian simulations for the typical Peclet numbers (ratio of the diffusion time to the advection time) encountered in transport through porous media. The observations do indicate that the dispersion has a strong dependence on the Peclet number and correlation length for lognormal conductivity fields. This approach will helps us alleviate the problems of binning and coarse graining that the Lagrangian methods suffer from. [1] Borgne, Tanguy Le, Timothy R. Ginn, and Marco Dentz. Impact of fluid deformation on mixing-induced chemical reactions in heterogeneous flows. Geophysical Research Letters 41.22 (2014): 7898-7906 [2] Bandopadhyay, Aditya, Philippe Davy, and Tanguy Le Borgne. Shear flows accelerate mixing dynamics in hyporheic zones and hillslopes. Geophysical Research Letters 45.21 (2018): 11-659
A source to sink study was performed at the scale of Africa based on (1) the measurement of the compacted siliciclastic sediment volumes preserved in the African Basins (margins, rifts, intracratonic), for the sink (see for the method in Guillocheau et al., 2012, Basin Research) and (2) the measurement of the eroded volumes obtained by the difference of elevation between the modern topography and remarkable deformed planation surfaces (etchplains or pediplains), for the source (see for the method in Guillocheau et al., 2018, Gondwana Research). Two main planation surfaces of Upper Cretaceous and Middle Eocene age were mapped. They are weathering surfaces (etchplains) known as the African Surface(s). (1) The sink analysis shows evidences of three periods of major denudation of Africa during Early Cretaceous (145-125 Ma, Berriasian-Barremian), Late Cretaceous (94-80 Ma) and uppermost Eocene to today (40-0 Ma). They record major Africa-scale uplifts related to mantle dynamics. The Cenozoic is a period of increase of the siliciclastic sediment volumes with a paroxysm during Plio-Pleistocene (5.5-0 Ma), here related to the dynamic of the Southern African superplume and not to climate changes. (2) The range of the sedimentation rates is between 5 and 80 x 103 km3/Ma, i.e. the rates of passive margin out of direct feeding by active mountain belts. (2) The analysis of the denudation through time shows two different spatial patterns: from 94 to 80 Ma, denudation is located all over Africa and from 40 to 0 Ma, only along the “coastal” plain of Africa (with the noticeable exception of the Congo catchment). This is interpreted as different modes of plate deformation and relief growth. (3) The source to sink budgets has been performed on the catchment of the Congo, Orange, Zambezi and East African rivers from 94-80 Ma to today. Surprisingly, they show equilibrated balances, suggesting low chemical erosion and/or neoformation of sedimentary particles (mainly clays: kaolinites to smectites) from the solutes along the sediment routing system.
Many orogens, such as the Western Alps, are characterised by the collision of hyper-extended margins. Before the onset of subduction these margins may have undergone several phases of deformation including rifting periods and periods without significant deformation in which the margins have been thermally relaxed. In consequence, modelling orogenic wedge formation in a self-consistent manner with application to the Western Alps requires modelling over large time spans (200 Ma) and sufficiently high resolution of the distinct deformation phases in both space and time. We perform high resolution long-term (>200 Ma) 2D thermo-mechanical numerical simulations including the lithosphere and upper mantle down to 660 km depth to study the dynamics of the Alpine cycle. Modelling of this cycle is subdivided into the following four stages: (I) in a slow spreading rift system of 60 Ma duration a 400 km wide basin is generated which contains exhumed lithospheric mantle and is bounded by regions of hyper-extended continental crust. (II) the modelled basin and hyper-extended passive margin system is thermally relaxed for 70 Ma. During this stage, the lithosphere is neither compressed nor extended. No spontaneous subduction initiation due to the densification of the cooling exhumed mantle occurs in the models. (III) the evolved system is shortened and a one-sided, forced subduction is initiated by thermal softening within the proximal part of the passive margin without prescribing any weak zone. (IV) after ca. 60 Ma of convergence the basin is closed and an orogenic wedge forms during continent-continent collision. We first quantify the impact of the initial geometric configuration from the onset of rifting on the Alpine cycle by varying the mechanical strength of the crust, being either an alternating sequence of horizontal mechanically strong and weak layers, or a homogeneous crust. Second, we investigate the control of lithospheric mantle characteristics on the Alpine cycle by (I) varying the rheological flow law of the mantle, (II) computing effective densities by either using a linearized equation of state, or a precomputed look-up table using Perple_X and (III) investigating the impact of serpentinisation of the lithospheric mantle exhumed in the basin by replacing the olivine rheology of the topmost 7 km by an antigorite rheology. First results show that rheology and density structure of the mantle lithosphere have a strong impact on the establishment and intensity of upper mantle convection. When convection cells are established a long-term thermal field is stabilised so that Moho temperatures do not decrease during the 130 Ma of extension and thermal relaxation. The geothermal profile across the passive margins is a crucial parameter for their effective strength and for subsequent forced subduction initiation by thermal softening. The flow law of the mantle lithosphere hence controls upper mantle convection which controls the pre-convergence thermal state which controls subduction initiation and the style of deformation within the resulting orogenic wedge.
Most renewable energy mismatch problems are considered at either the national scale or the building scale. In a smart integrated urban energy infrastructure, mismatch could be solved at the neighborhood scale by matching building electricity, heat and cold demand profiles, waste heat and cold supply profiles and renewable energy generation profiles. The energy profile of a building is both dependent on the occupants and usage, as well as the time of year and the time of day. Buildings provide opportunities for storing heat and electricity over periods of up to a few days (e.g. EV batteries, thermal mass). This can be added upon by seasonal heat and cold storage systems like ATES at the neighborhood level. Making smart use of this variety within a neighborhood provides opportunities for increased local consumption of renewable energy and decreased requirements of transmission infrastructure, as well as decreasing the total energy demand by using waste heat and cold at another moment and/or in another location. In our study we aim to contribute to the knowledge on renewable urban energy supply by identifying the potentials of the neighborhood as a multi-scale energy system and unit of analysis. This is done in a model-based approach by creating heat, cold, and electricity demand and supply profiles for different types of buildings that can be found in a neighborhood. These are integrated into a spatial model, that can take into account potentials from building energy demand and supply profiles next to renewable energy production potential and seasonal storage.
