Numerical simulation of CH4 and its stable isotopologues on regional and global scale

Die vorliegende Studie versucht das globale CH4 Budget und den Anstieg von CH4 in der Atmosphäre seit 2007 zu verstehen. Der erste Teil befasst sich mit unserem derzeitigen Verständnis lokaler anthropogener CH4 Emissionen aus Punktquellen und deren atmosphärischer Verteilung auf regionaler Ebene. Mit Hilfe des dreifach „genesteten“ globalen und regionalen Klima-Chemie-Modells MECO(3) wird dafür die atmosphärische Ausbreitung von CH4 Emissionen aus Kohleminenschächten und deren stabile Isotopensignatur untersucht. Die Arbeit umfasst außerdem die Entwicklung eines Vorhersagesystems zur Unterstützung von Messkampagnen. Global wird der CH4 Anstieg im Hinblick auf eine gleichzeitige δ 13C(CH4) Abnahme analysiert. Diese weist auf einen veränderten relativen Beitrag der einzelnen CH4 Quellen zum erneuten CH4 Anstieg hin. Sensitivitätssimulationen mit dem “state-of-the-art” globalen Klima-Chemie-Modell EMAC, die insbesondere die Rolle von unkonventioneller Gasförderung (“fracking”) untersuchen, zeigen, dass der globale CH4-Anstieg nicht allein auf diese Emissionen zurückzuführen ist. Zudem ist der Einfluss einer OH Konzentrationssenkung auf das globale δ13C(CH4) eher gering. Stattdessen spielen biogene Emissionen eine wichtige Rolle. Darüber hinaus reagiert δ13C(CH4) sehr empfindlich auf Änderungen der Emissionen aus Biomassebrennen, was die Bedeutung der in den Simulationen verwendeten Emissionsabschätzungen unterstreicht

Synchronizing the timing of anoxia, volcanism and the pacing of the Earth’s orbit in the Early Cretaceous

Recurrent acceleration of the hydrolysing cycle, so-called Episodes of Environmental Changes, occur in the Early Cretaceous. As the geologic time scale show large uncertainties, the pacing and the chronological relationship of these events remain obscure. We present here new radio-astrochronologic data from the Neuquén Basin (Argentina) anchored to the Tethyan realm. The new time sale of the Valanginian-Hauterivian provides ages of ammonite zones with an uncertainty of ± 0.2 myr and provides much precise age of the start of the Weissert Event. The age of the start of the Weissert Event is at 134.5 ± 0.2 myr, which is exactly synchronous with the main phase of the Paraná-Etendeka large igneous province activity. Most recent duration and age estimates from the Berriasian to the Barremian are reviewed and differ from the Geologic Time Scale 2016 by several million of years. Thanks to this new time scale, belemnite δ13C are reviewed and show a strong pacing with a period of 2.4 myr, which correspond to the long-eccentricity cycle. Higher amplitudes of the 2.4-myr cycle are observed at time of large igneous province emplacement, which may be due to accelerated hydrolysis cycle following CO2 input to the atmosphere from the volcanic activity.Fil: Martinez, Mathieu. Universite de Rennes I; FranciaFil: Aguirre Urreta, María Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Lescano, Marina Aurora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Omarini, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Tunik, Maisa Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Frederichs, Thomas. Universitat Bremen; AlemaniaFil: Nickl, Anna-Leah. Universitat Bremen; AlemaniaFil: Pälike, Heiko. Universitat Bremen; AlemaniaEGU General Assembly 2019VienaAustriaEuropean Geosciences Unio

Provenance of nutrients in fresh water samples from Tahiti and Moorea, French Polynesia

Physico-chemical parameters, chloride, bromide and sulfate concentrations, nutrient concentrations, oxygen and hydrogen isotopic composition of water as well as oxygen and nitrogen isotopic composition of dissolved nitrate were measured in sea water, fresh submarine groundwater discharge (FSGD), groundwater and stream water samples collected during a field expedition on Tahiti and Moorea, French Polynesia in January and February 2016

Provenance of nutrients in submarine fresh groundwater discharge on Tahiti and Moorea, French Polynesia

International audienceSubmarine fresh groundwater discharge (SFGD) provides a pathway for dissolved nutrients and other solutes from land to the ocean. It connects pollution from anthropogenic land use with coastal marine waters. In case of the oligotrophic central South Pacific Ocean around Tahiti and Moorea, French Polynesia, nutrient concentrations are particularly low. Both islands are surrounded by tropical coral reefs, which are highly sensitive to nutrient concentrations in the ambient water so that a surplus of nutrients, e.g. from SFGD, could lead to the degradation of coral reef ecosystems.We examined nutrient contributions from different land cover classes to nutrient fluxes through SFGD by combining nutrient concentration data, spatial data, oxygen and hydrogen isotope ratios of water (δ18OH2O and δ2HH2O, respectively) and nitrogen and oxygen isotope ratios of nitrate (δ15NNO3- and δ18ONO3-). Undeveloped land provides measurable quantities of phosphate while nitrate concentrations are often below the detection limit. The bulk of the nutrient load in nutrient enriched groundwater is of anthropogenic origin. It enters the aquifer system at low altitudes, where catchments are characterized by anthropogenic land use. Elevated nitrate concentrations are mainly associated with septic waste/manure inputs in fresh water.This study elucidates sources of nutrients in the groundwater of two volcanic islands, highlighting the impact that even a small populated area along the coast of an island can have, as well as the differences in nutrient transport between these seemingly similar locations

Interhemispheric radio-astrochronological calibration of the time scales from the Andean and the Tethyan areas in the Valanginian–Hauterivian (Early Cretaceous)

International audienceAn integrated radio-astrochronological framework of the Agrio Formation in the Andean Neuquén Basin of west-central Argentina provides new constraints on the age and the duration of the late Valanginian through Hauterivian stratigraphic interval. A CA-ID TIMS U-Pb age of 126.97 ± 0.04(0.07)[0.15] Ma is presented here from the upper Hauterivian Agua de la Mula Member of the Agrio Formation. Biostratigraphic data from ammonoids and calcareous nannofossils and this high precision new radioisotopic age, together with three former ones from the same Agrio Formation are combined with new astrochronological data in the Andes. These are correlated with modern cyclostratigraphic studies in the classical sections of the Mediterranean Province of the Tethys, supporting detailed interhemispheric correlations for the Early Cretaceous. We also provide new δ13C data from the Agrio Formation which are compared with records from the classic Tethyan sections. According to our calibration, the minimum in the values in the mid-Hauterivian appears to be synchronous and, thus, another important stratigraphic marker for global correlation. A new duration of 5.21 ± 0.08 myr is calculated for the Hauterivian Stage, starting at 131.29 ± 0.19 Ma and ending at 126.08 ± 0.19 Ma. The difference between the duration of the Hauterivian in GTS2016 and in this study is 1.32 myr while the base and top of the GTS2016 Hauterivian differ respectively by 3.40 and 4.69 myr

Stable isotopes from the El Portón section, Argentina, Early Cretaceous

An integrated radio-astrochronological framework of the Agrio Formation in the Andean Neuquén Basin of west-central Argentina provides new constraints on the age and the duration of the late Valanginian through Hauterivian stratigraphic interval. A CA-ID TIMS U-Pb age of 126.97 ± 0.04(0.07)[0.15] Ma is presented here from the upper Hauterivian Agua de la Mula Member of the Agrio Formation. Biostratigraphic data from ammonoids and calcareous nannofossils and this high precision new radioisotopic age, together with three former ones from the same Agrio Formation are combined with new astrochronological data in the Andes. These are correlated with modern cyclostratigraphic studies in the classical sections of the Mediterranean Province of the Tethys, supporting detailed interhemispheric correlations for the Early Cretaceous. We also provide new δ13C data from the Agrio Formation which are compared with records from the classic Tethyan sections. According to our calibration, the minimum in the values in the mid-Hauterivian appears to be synchronous and, thus, another important stratigraphic marker for global correlation. A new duration of 5.21 ± 0.08 myr is calculated for the Hauterivian Stage, starting at 131.29 ± 0.19 Ma and ending at 126.08 ± 0.19 Ma. The difference between the duration of the Hauterivian in GTS2016 and in this study is 1.32 myr while the base and top of the GTS2016 Hauterivian differ respectively by 3.40 and 4.69 myr