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Das Oberjura-Profil im Erdgasgraben bei Hitzhausen (Westliches Wiehengebirge, Nordwestdeutschland)
(1996)
Im Sommer 1995 war beim Bau einer Erdgasleitung im Wiehengebirge nordöstlich Osnabrück kurzfristig die gesamte Schichtenfolge vom tiefen Oxford bis zur Tithon-Basis aufgeschlossen. Die Gesteinsansprache ermöglichte unter Berücksichtigung der Mikrofauna eine feinstratigraphische Gliederung. Die Sedimente wurden außerdem mit einer Gamma-Sonde nach dem Scintillometer-Prinzip vermessen und daraus eine Gamma-ray-Kurve erstellt.
In Oppenwehe, ca. 2 km östlich der Stemweder Berge, befindet sich zwischen dem Oppenweher Moor im Norden und dem Großen Dieckfluß im Süden eine ca. 3 km lange und 1 km breite Erhebung. Sie überragt das umgebende Flachland um ca. 5-6 m und bildet vermutlich das nordwestliche Ende einer bei Hille westlich von Minden verlaufenden saalezeitlichen Stauchungsstruktur, die sich anscheinend in einer Reihe von Rücken bis nach Oppenwehe fortsetzt. In der seit Herbst 1995 am Ostrand von Oppenwehe bestehenden Abgrabung der Fa. Lindemann, Lemförde, konnten detaillierte Beobachtungen zum inneren Aufbau und damit zum Entstehungsablauf dieser Struktur gewonnen werden. Es liegt hier eine glaziäre Abfolge ("Serie") von Vorschüttsanden, Grundmoräne und Nachschüttbildungen vor, die verfaltet und verschuppt ist. Daraus läßt sich eine zweimalige Überfahrung dieses Raumes durch das saalezeitliche Inlandeis ableiten. Eine wenige Meter südlich der Sandgrube abgeteufte Rammkernbohrung erbrachte darüber hinaus Aufschluß über den tieferen Teil der Schichtenfolge des Quartärs. Sie umfaßt holsteinzeitliche Ablagerungen und endet mit einer elsterzeitlichen Grundmoräne, die unmittelbar auf Tonsteinen der Unterkreide liegt.
Ein neues Bajocium-Profil (Mittlerer Jura) im Osnabrücker Bergland (Niedersachsen) : mit 2 Tabellen
(1990)
In den Jahren 1984-1986 wurde südöstlich von Osnabrück beim Bau der Autobahn (A 33) ein großer Aufschluß im Bajocium und Bathonium geschaffen. Mit Hilfe der horizontiert aufgesammelten Ammoniten konnte das Bajocium im Osnabrücker Bergland entsprechend den Standard-Zonen und -Subzonen der nordwesteuropäischen Faunenprovinz untergliedert werden.
The theoretical basis for the link between the leaf exchange of carbonyl sulfide (COS), carbon dioxide (CO2) and water vapour (H2O) and the assumptions that need to be made in order to use COS as a tracer for canopy net photosynthesis, transpiration and stomatal conductance, are reviewed. The ratios of COS to CO2 and H2O deposition velocities used to this end are shown to vary with the ratio of the internal to ambient CO2 and H2O mole fractions and the relative limitations by boundary layer, stomatal and internal conductance for COS. It is suggested that these deposition velocity ratios exhibit considerable variability, a finding that challenges current parameterizations, which treat these as vegetation-specific constants. COS is shown to represent a better tracer for CO2 than H2O. Using COS as a tracer for stomatal conductance is hampered by our present poor understanding of the leaf internal conductance to COS. Estimating canopy level CO2 and H2O fluxes requires disentangling leaf COS exchange from other ecosystem sources/sinks of COS. We conclude that future priorities for COS research should be to improve the quantitative understanding of the variability in the ratios of COS to CO2 and H2O deposition velocities and the controlling factors, and to develop operational methods for disentangling ecosystem COS exchange into contributions by leaves and other sources/sinks. To this end, integrated studies, which concurrently quantify the ecosystem-scale CO2, H2O and COS exchange and the corresponding component fluxes, are urgently needed.
We investigate the potential of carbonyl sulfide (COS) for being used as a tracer for canopy net photosynthesis, transpiration and stomatal conductance by examining the theoretical basis of the link between leaf COS, carbon dioxide (CO2) and water vapour (H2O) exchange. Our analysis identifies several limitations that need to be overcome to this end, however at present we lack appropriate ecosystem-scale field measurements for assessing their practical significance. It however appears that COS represents a better tracer for CO2 than H2O. Concurrent measurements of ecosystem scale COS, CO2 and H2O exchange are advocated.
Sedimentologie und Verwitterungsbeständigkeit des Wellenkalks
(Unterer Muschelkalk) von Osnabrück
(1993)
Die Sedimentologie und Verwitterungsbeständigkeit des Osnabrücker Weilenkalks (Unterer Muschelkalk) werden an Mauersteinen aus zwei Gebäuden in Osnabrück und an Proben aus dem Steinbruch im Botanischen Garten Osnabrück untersucht. Es lassen sich 6 Mikrofaziestypen (A-F) unterscheiden, die ausführlich beschrieben werden. Ihre Analyse erlaubt detaillierte Aussagen zum Sedimentationsraum und zur Entstehung. Darauf aufbauend werden die in der Schichtenfolge beobachtbaren Sedimentationszyklen auf Meeresspiegeländerungen zurückgeführt. Es lassen sich deutliche Unterschiede in der Verwitterungsbeständigkeit der verschiedenen Mikrofaziestypen erkennen. Am verwitterungsbeständigsten sind die Mikrofaziestypen A und B, durch Sturmfluten entstandene Lagen im unteren und oberen Teil des Oolithbank-Members der Wellenkalk-Formation. Die Mikrofaziestypen A und B sind so verwitterungsbeständig., da sie nicht feingeschichtet sind und freiwillige Wasseraufnahme, Schurecht-Ratio (= freiwillige Wasseraufnahme geteilt durch effektive Porosität) sowie der Gehalt an salzsäureunlöslichem Rückstand relativ gering sind.
Die Wetterstation und die Photovoltaikanlage (Leihgabe der Stadtwerke Osnabrück) auf dem Dach des Museums am Schölerberg wurde von Hänel (1998a) beschrieben. In einem weiteren Artikel sind die Daten der Wetterstation und der Photovoltaikanlage für das Jahr 1997 zusammengefasst (Hänel, 1998b), dort ist auch die Herkunft der Vergleichsdaten beschrieben. In Tabelle 1 sind die Monatswerte für 1998 zusammengestellt.
Von der Gemeinde Hagen a.T.W. wurde am Butterberg ein ehemaliger Steinbruch im Osning-Sandstein durch die Anlage eines Schurfgrabens so erweitert, daß jetzt die Basis des Osning-Sandsteins und etwa 20, m der Schichtenfolge aus seinem Liegenden freigelegt sind. Die Basis des Osning-Sandsteins besteht aus einem dünnen Geröllhorizont, dem Osning-Konglomerat. Das Konglomerat wurde transgressiv auf Schichten der Bückeberg-Folge 1 (tiefster "Wealden") geschüttet. Unter den Gesteinen der Bückeberg-Folge, die mit einer Restmächtigkeit von nur noch etwa 5 m erhalten sind, treten in dem Schurfgraben noch ca. 15 m Ablagerungen des Serpulits auf. Dieser neu geschaffene Aufschluß wird langfristig - als Naturdenkmal geschützt - erhalten bleiben.
This article presents a multiscale approach for detecting and monitoring soil erosion phenomena (i.e. gully erosion) in the agro-industrial area around the city of Taroudannt, Souss basin, Morocco. The study area is characterized as semi-arid with an annual average precipitation of 200 mm. Water scarcity, high population dynamics and changing land use towards huge areas of irrigation farming present numerous threats to sustainability. The agro-industry produces citrus fruits and vegetables in monocropping, mainly for the European market. Badland areas strongly affected by gully erosion border the agricultural areas as well as residential areas. To counteract the significant loss of land, land-leveling measures are attempted to create space for plantations and greenhouses. In order to develop sustainable approaches to limit gully growth the detection and monitoring of gully systems is fundamental. Specific gully sites are monitored with unmanned aerial vehicle (UAV) taking small-format aerial photographs (SFAP). This enables extremely high-resolution analysis (SFAP resolution: 2-10 cm) of the actual size of the gully channels as well as a detailed continued surveillance of their growth. Transferring the methodology on a larger scale using Quickbird satellite data (resolution: 60 cm) leads to the possibility of a large-scale analysis of the whole area around the city of Taroudannt (Area extent: ca. 350 km²). The results will then reveal possible relationships of gully growth and agro-industrial management and may even illustrate further interdependencies. The main objective is the identification of areas with high gully-erosion risk due to non-sustainable land use and the development of mitigation strategies for the study area.
Zusammenfassung der Ergebnisse.
1. Eine einheitliche Gliederung der diluvialen Terrassen ist Voraussetzung für die vorliegende Untersuchung.
a) Die Bezeichnung "Mittelterrassen" wurde vermieden, vielmehr ist in Hoch- und Talwegterrasse gegliedert worden. b) Die Höhenbezeichnungen wurden durch Altersbestimmungen ersetzt.
2. Eine gemeinsame Behandlung erforderten die älteren Terrassen des Eis- und Eckbaches.
a) Der Oberlauf des Eckbaches ist tektonisch angelegt. In diesem Engtal wie auch in den südlich folgenden fehlen nicht nur die älteren sondern überhaupt jegliche Terrassen.
b) Die Schotterfluren innerhalb der Marnheimer Bucht stellen Gleithänge dar, an denen der Eisbach nach dem Innern hin heruntergerutscht ist.
c) Schon im Pliozän ist die Scholle der Marnheimer Bucht gegen den Rheintalgraben aufgerichtet.
3. Die Hochterrasse ist nur im nördlichen Gebietsteil ausgebildet, im Süden wird sie durch die Ablagerung der Freinsheimer Tonschichten lokal ersetzt.
4. Die Freinsheimer Tonschichten stellen eine lokale prärißeiszeitliche Auffüllung des rückgesunkenen Mitteldiluvialen Senkungsfeldes dar.
5. Die mittel diluviale Reakkumulation ist eine der bedeutendsten Erscheinungen für die Morphologie des Mainzer Beckens.
a) Infolge der starken Niveaudifferenzen am Rand des Pfälzerwaldes mußte die Aufschüttung gerade hier sehr mächtig sein.
b) Die Schuttkegel sind teils ein Ergebnis dieser Aufschüttung teils ein Ergebnis der flächenhaften Abtragung und mechanischen Zertrümmerung am Gebirgsrand.
c) Morphologische Tatsachen beweisen, daß die südlichen Seitenfliisse des Rheins jünger sind als Pfrimm und Eisbach.
6. Die Ursache für die Entstehung des einzelnen Fluß terrassenrestes im Gebirge (Rotliegendausräumung von Lambrecht-Grevenhausen) ist die Stauung des Speyerbaches unmittelbar vor der Verwerfung Albersweiler-Lindenberg-Bad Dürkheim.
7. Der Niederterrasse kommt im südlichen Teil des Untersuchungsgebietes größere morphologische Bedeutung zu als im nördlichen.
8. Der Südwestteil des Mainzer Beckens kann in einzelne tektonische Senkungsfelder eingeteilt werden, die durch· Verwerfungen begrenzt sind.
a) Erst im Mitteldiluvium sind die Hauptschollen des Rheinhessischen Blockgebirges aus dem allgemeinen Senkungsbereich ausgegliedert worden.
b) Verschiedene morphologische Tatsachen, besonders in der Rheinpfalz, sprechen dafür, daß im Rheintalgraben gegensätzliche Bewegungsrichtungen der sich senkenden Schollen geherrscht haben.
c) Im Mitteldiluvium wirkte noch die alte Bewegungstendenz mit größter Intensität im Innern.
d) Frühestens im Riß-Würm-Interglazial sank alsdann das Mitteldiluviale Senkungsfeld gebirgswärts zurück.
e) Aber auch in gleichen Zeitabschnitten herrschten im Rheintal verschiedene Bewegungsrichtungen, wobei sich Wilsers Ansicht bestätigt, daß das Rheintal in quer gerichtete Unterabschnitte zu gliedern ist, die als Einheiten verschiedensinnige Bewegungen zeigen.
We conducted measurements of the five important short-lived organic bromine species in the marine boundary layer (MBL). Measurements were made in the Northern Hemisphere mid-latitudes (Sylt Island, North Sea) in June 2009 and in the tropical Western Pacific during the TransBrom ship campaign in October 2009. For the one-week time series on Sylt Island, mean mixing ratios of CHBr3, CH2Br2, CHBr2Cl and CH2BrCl were 2.0, 1.1, 0.2, 0.1 ppt, respectively. We found maxima of 5.8 and 1.6 ppt for the two main components CHBr3 and CH2Br2. Along the cruise track in the Western Pacific (between 41° N and 13° S) we measured mean mixing ratios of 0.9, 0.9, 0.2, 0.1 and 0.1 ppt for CHBr3, CH2Br2, CHBrCl2, CHBr2Cl and CH2BrCl. Air samples with coastal influence showed considerably higher mixing ratios than the samples with open ocean origin. Correlation analyses of the two data sets yielded strong linear relationships between the mixing ratios of four of the five species (except for CH2BrCl). Using a combined data set from the two campaigns and a comparison with the results from two former studies, rough estimates of the molar emission ratios between the correlated substances were: 9/1/0.35/0.35 for CHBr3/CH2Br2/CHBrCl2/CHBr2Cl. Additional measurements were made in the tropical tropopause layer (TTL) above Teresina (Brazil, 5° S) in June 2008, using balloon-borne cryogenic whole air sampling technique. Near the level of zero clear-sky net radiative heating (LZRH) at 14.8 km about 2.25 ppt organic bromine was bound to the five short-lived species, making up 13% of total organic bromine (17.82 ppt). CH2Br2 (1.45 ppt) and CHBr3 (0.56 ppt) accounted for 90% of the budget of short-lived compounds in that region. Near the tropopause (at 17.5 km) organic bromine from these substances was reduced to 1.35 ppt, with 1.07 and 0.12 ppt attributed to CH2Br2 and CHBr3, respectively.
We conducted measurements of up to the five important short-lived brominated species in the marine boundary layer (MBL) of the mid-latitudes (List/Sylt, North Sea) in June 2009 and of the tropical Western Pacific during the TransBrom ship campaign in October 2009. For the one-week time series in List mean mixing ratios of 2.0, 1.1, 0.2, 0.1 ppt were analysed for CHBr3, CH2Br2, CHBr2Cl and CH2BrCl, with maxima of 5.8 and 1.6 ppt for the two main components CHBr3 and CH2Br2. Along the cruise track in the Western Pacific (between 41° N and 13° S) mean mixing ratios of 1.0, 0.9, 0.2, 0.1 and 0.1 ppt for CHBr3, CH2Br2, CHBrCl2, CHBr2Cl and CH2BrCl were determined. Air samples with coastal influence showed considerably higher mixing ratios than the samples with open ocean origin. Correlation analyses of the two datasets yielded strong linear relationships between the mixing ratios of four of the five species (except for CH2BrCl). Using a combined dataset from the two campaigns, rough estimates of the molar emission ratios between the correlated substances were derived as follows: 9/1/0.3/0.3 for CHBr3/CH2Br2/CHBrCl2/CHBr2Cl. Additional measurements were made in the tropical tropopause layer (TTL) above Teresina (Brazil, 5.07° S, 42.87° W) in June 2008, using balloon-borne cryogenic whole air sampling technique. Near the level of zero clear-sky net radiative heating (LZRH) at 14.8 km about 2.25 ppt organic bromine was bound to the five short-lived species, making up 13 % of total organic bromine (17.82 ppt). CH2Br2 (1.45 ppt) and CHBr3 (0.56 ppt) accounted for 90 % of the budget of short-lived compounds in that region. Near the tropopause (at 17.5 km) organic bromine from short-lived substances was reduced to 1.35 ppt, with 1.07 ppt and 0.12 ppt attributed to CH2Br2 and CHBr3 respectively.
Balloon-borne stratospheric BrO measurements : comparison with Envisat/SCIAMACHY BrO limb profiles
(2005)
For the first time, results of all four existing stratospheric BrO profiling instruments, are presented and compared with reference to the SLIMCAT 3-dimensional chemical transport model (3-D CTM). Model calculations are used to infer a BrO profile validation set, measured by 3 different balloon sensors, for the new Envisat/SCIAMACHY (ENVIronment SATellite/SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) satellite instrument. The balloon observations include (a) balloon-borne in situ resonance fluorescence detection of BrO, (b) balloon-borne solar occultation DOAS measurements (Differential Optical Absorption Spectroscopy) of BrO in the UV, and (c) BrO profiling from the solar occultation SAOZ (Systeme d'Analyse par Observation Zenithale) balloon instrument. Since stratospheric BrO is subject to considerable diurnal variation and none of the measurements are performed close enough in time and space for a direct comparison, all balloon observations are considered with reference to outputs from the 3-D CTM. The referencing is performed by forward and backward air mass trajectory calculations to match the balloon with the satellite observations. The diurnal variation of BrO is considered by 1-D photochemical model calculation along the trajectories. The 1-D photochemical model is initialised with output data of the 3-D model with additional constraints on the vertical transport, the total amount and photochemistry of stratospheric bromine as given by the various balloon observations. Total [Bry]=(20.1±2.8)pptv obtained from DOAS BrO observations at mid-latitudes in 2003, serves as an upper limit of the comparison. Most of the balloon observations agree with the photochemical model predictions within their given error estimates. First retrieval exercises of BrO limb profiling from the SCIAMACHY satellite instrument agree to <±50% with the photochemically-corrected balloon observations, and tend to show less agreement below 20 km.
Contribution of sulfuric acid and oxidized organic compounds to particle formation and growth
(2012)
Lack of knowledge about the mechanisms underlying new particle formation and their subsequent growth is one of the main causes for the large uncertainty in estimating the radiative forcing of atmospheric aerosols in global models. We performed chamber experiments designed to study the contributions of sulfuric acid and organic vapors to formation and to the early growth of nucleated particles, respectively. Distinct experiments in the presence of two different organic precursors (1,3,5-trimethylbenzene and α-pinene) showed the ability of these compounds to reproduce the formation rates observed in the low troposphere. These results were obtained measuring the sulfuric acid concentrations with two Chemical Ionization Mass Spectrometers confirming the results of a previous study which modeled the sulfuric acid concentrations in presence of 1,3,5-trimethylbenzene.
New analysis methods were applied to the data collected with a Condensation Particle Counter battery and a Scanning Mobility Particle Sizer, allowing the assessment of the size resolved growth rates of freshly nucleated particles. The effect of organic vapors on particle growth was investigated by means of the growth rate enhancement factor (Γ), defined as the ratio between the measured growth rate in the presence of α-pinene and the kinetically limited growth rate of the sulfuric acid and water system. The observed Γ values indicate that the growth is dominated by organic compounds already at particle diameters of 2 nm. Both the absolute growth rates and Γ showed a strong dependence on particle size supporting the nano-Köhler theory. Moreover, the separation of the contributions from sulfuric acid and organic compounds to particles growth reveals that the organic contribution seems to be enhanced by the sulfuric acid concentration. The size resolved growth analysis finally indicates that both condensation of oxidized organic compounds and reactive uptake contribute to particle growth.
A comprehensive set of stratospheric balloon and aircraft samples was analyzed for the position-dependent isotopic composition of nitrous oxide (N2O). Results for a total of 220 samples from between 1987 and 2003 are presented, nearly tripling the number of mass-spectrometric N2O isotope measurements in the stratosphere published to date. Cryogenic balloon samples were obtained at polar (Kiruna/Sweden, 68° N), mid-latitude (southern France, 44° N) and tropical sites (Hyderabad/India, 18° N). Aircraft samples were collected with a newly-developed whole air sampler on board of the high-altitude aircraft M55 Geophysica during the EUPLEX 2003 campaign. All samples were analyzed by laboratory mass spectrometry for their 18O/16O and position-dependent 15N/14N isotope ratios with very high precision (standard deviation about 0.15 per mil for 18O/16O and average 15N/14N ratios, about 0.5 per mil for 15NNO/14NNO and N15NO/N14NO ratios). For mixing ratios above 200 nmol mol−1, relative isotope enrichments (δ values) and mixing ratios display a compact relationship, which is nearly independent of latitude and season and which can be explained equally well by Rayleigh fractionation or mixing. However, for mixing ratios below 200 nmol mol−1 this compact relationship gives way to meridional, seasonal and interannual variations. A comparison to a previously published mid-latitude balloon profile even shows large zonal variations, justifying the use of three-dimensional models for further data interpretation.
In general, the magnitude of the apparent fractionation constants (apparent isotope effects) increases continuously with altitude and decreases from the equator to the North pole, which can be qualitatively understood by the interplay between the time-scales of N2O photochemistry and transport. Deviations from this behavior occur where polar vortex air mixes with nearly N2O-free upper stratospheric/mesospheric air (e.g., during the boreal winter of 2003 and possibly 1992). Aircraft observations in the polar vortex at mixing ratios below 200 nmol mol−1 deviate from isotope variations expected for both Rayleigh fractionation and end-member mixing, but could be explained by continuous weak mixing between intravortex and extravortex air (Plumb et al., 2000). Finally, correlations between 18O/16O and average 15N/14N isotope ratios or between the position-dependent 15N/14N isotope ratios show that photo-oxidation makes a large contribution to the total N2O sink in the lower stratosphere (up to 100%). Towards higher altitudes, the temperature dependence of these isotope correlations becomes visible in the stratospheric observations.
Surface measurements of aerosol and ice nuclei (IN) at a Central European mountain site during an episode of dust transport from the Sahara are presented. Transport is simulated by the Eulerian regional dust model DREAM. Ice nuclei and mineral dust are significantly correlated. The highest correlation is found between IN concentration and aerosol surface area. The ice nucleating characteristics of the aerosol with respect to temperature and supersaturation are similar during the dust episode than during the course of the year. This suggests that dust is always a dominant constituent of ice nucleating aerosols in Central Europe.
Surface measurements of aerosol and ice nuclei (IN) at a Central European mountain site during an episode of dust transport from the Sahara are presented. Ice nuclei were sampled by electrostatic precipitation on silicon wafers and were analyzed in an isothermal static vapor diffusion chamber. The transport of mineral dust is simulated by the Eulerian regional dust model DREAM. Ice nuclei and mineral dust are significantly correlated, in particular IN number concentration and aerosol surface area. The ice nucleating characteristics of the aerosol as analyzed with respect to temperature and supersaturation are similar during the dust episode than during the course of the year. This suggests that dust may be a main constituent of ice nucleating aerosols in Central Europe.
The isotopic composition of methane in the stratosphere : high-altitude balloon sample measurements
(2011)
The isotopic composition of stratospheric methane has been determined on a large suite of air samples from stratospheric balloon flights covering subtropical to polar latitudes and a time period of 16 yr. 154 samples were analyzed for δ13C and 119 samples for δD, increasing the previously published dataset for balloon borne samples by an order of magnitude, and more than doubling the total available stratospheric data (including aircraft samples) published to date. The samples also cover a large range in mixing ratio from tropospheric values near 1800 ppb down to only 250 ppb, and the strong isotope fractionation processes accordingly increase the isotopic composition up to δ13C = −14‰ and δD = +190‰, the largest enrichments observed for atmospheric CH4 so far. When analyzing and comparing kinetic isotope effects (KIEs) derived from single balloon profiles, it is necessary to take into account the residence time in the stratosphere in combination with the observed mixing ratio and isotope trends in the troposphere, and the range of isotope values covered by the individual profile. The isotopic composition of CH4 in the stratosphere is affected by both chemical and dynamical processes. This severely hampers interpretation of the data in terms of the relative fractions of the three important sink mechanisms (reaction with OH, O(1D) and Cl). It is shown that a formal sink partitioning using the measured data severely underestimates the fraction removed by OH, which is likely due to the insensitivity of the measurements to the kinetic fractionation in the lower stratosphere. Full quantitative interpretation of the CH4 isotope data in terms of the three sink reactions requires a global model.
The isotopic composition of methane in the stratosphere : high-altitude balloon sample measurements
(2011)
The isotopic composition of stratospheric methane has been determined on a large suite of air samples from stratospheric balloon flights covering subtropical to polar latitudes and a time period of 16 yr. 154 samples were analyzed for δC and 119 samples for δD, increasing the previously published dataset for balloon borne samples by an order of magnitude, and more than doubling the total available stratospheric data (including aircraft samples) published to date. The samples also cover a large range in mixing ratio from tropospheric values near 1800 ppb down to only 250 ppb, and the strong isotope fractionation processes accordingly increase the isotopic composition up to δ13C=−14‰ and δD= +190‰, the largest enrichments observed for atmospheric CH4 so far. When analyzing and comparing kinetic isotope effects (KIEs) derived from single balloon profiles, it is necessary to take into account the residence time in the stratosphere in combination with the observed mixing ratio and isotope trends in the troposphere, and the range of isotope values covered by the individual profile. Temporal isotope trends can also be determined in the stratosphere and compare reasonably well with the tropospheric trends. The effects of chemical and dynamical processes on the isotopic composition of CH4 in the stratosphere are discussed in detail. Different ways to interpret the data in terms of the relative fractions of the three important sink mechanisms (reaction with OH, O(1D)) and Cl, respectively), and their limitations, are investigated. The classical approach of using global mean KIE values can be strongly biased when profiles with different minimum mixing ratios are compared. Approaches for more local KIE investigations are suggested. It is shown that any approach for a formal sink partitioning from the measured data severely underestimates the fraction removed by OH, which is likely due to the insensitivity of the measurements to the kinetic fractionation in the lower stratosphere. Attempts can be made to correct for the lower stratospheric sink bias, but full quantitative interpretation of the CH4 isotope data in terms of the three sink reactions requires a global model.
This paper presents an analysis of the recent tropospheric molecular hydrogen (H2) budget with a particular focus on soil uptake and European surface emissions. A variational inversion scheme is combined with observations from the RAMCES and EUROHYDROS atmospheric networks, which include continuous measurements performed between mid-2006 and mid-2009. Net H2 surface flux, then deposition velocity and surface emissions and finally, deposition velocity, biomass burning, anthropogenic and N2 fixation-related emissions were simultaneously inverted in several scenarios. These scenarios have focused on the sensibility of the soil uptake value to different spatio-temporal distributions. The range of variations of these diverse inversion sets generate an estimate of the uncertainty for each term of the H2 budget. The net H2 flux per region (High Northern Hemisphere, Tropics and High Southern Hemisphere) varies between −8 and +8 Tg yr−1. The best inversion in terms of fit to the observations combines updated prior surface emissions and a soil deposition velocity map that is based on bottom-up and top-down estimations. Our estimate of global H2 soil uptake is −59±9 Tg yr−1. Forty per cent of this uptake is located in the High Northern Hemisphere and 55% is located in the Tropics. In terms of surface emissions, seasonality is mainly driven by biomass burning emissions. The inferred European anthropogenic emissions are consistent with independent H2 emissions estimated using a H2/CO mass ratio of 0.034 and CO emissions within the range of their respective uncertainties. Additional constraints, such as isotopic measurements would be needed to infer a more robust partition of H2 sources and sinks.
This paper presents an analysis of the recent tropospheric molecular hydrogen (H2) budget with a particular focus on soil uptake and surface emissions. A variational inversion scheme is combined with observations from the RAMCES and EUROHYDROS atmospheric networks, which include continuous measurements performed between mid-2006 and mid-2009. Net H2 surface flux, soil uptake distinct from surface emissions and finally, soil uptake, biomass burning, anthropogenic emissions and N2 fixation-related emissions separately were inverted in several scenarios. The various inversions generate an estimate for each term of the H2 budget. The net H2 flux per region (High Northern Hemisphere, Tropics and High Southern Hemisphere) varies between −8 and 8 Tg yr−1. The best inversion in terms of fit to the observations combines updated prior surface emissions and a soil deposition velocity map that is based on soil uptake measurements. Our estimate of global H2 soil uptake is −59 ± 4.0 Tg yr−1. Forty per cent of this uptake is located in the High Northern Hemisphere and 55% is located in the Tropics. In terms of surface emissions, seasonality is mainly driven by biomass burning emissions. The inferred European anthropogenic emissions are consistent with independent H2 emissions estimated using a H2/CO mass ratio of 0.034 and CO emissions considering their respective uncertainties. To constrain a more robust partition of H2 sources and sinks would need additional constraints, such as isotopic measurements.
We have used the SLIMCAT 3-D off-line chemical transport model (CTM) to quantify the Arctic chemical ozone loss in the year 2002/2003 and compare it with similar calculations for the winters 1999/2000 and 2003/2004. Recent changes to the CTM have improved the model's ability to reproduce polar chemical and dynamical processes. The updated CTM uses σ-θ as a vertical coordinate which allows it to extend down to the surface. The CTM has a detailed stratospheric chemistry scheme and now includes a simple NAT-based denitrification scheme in the stratosphere.
In the model runs presented here the model was forced by ECMWF ERA40 and operational analyses. The model used 24 levels extending from the surface to ~55 km and a horizontal resolution of either 7.5°×7.5° or 2.8°×2.8°. Two different radiation schemes, MIDRAD and the CCM scheme, were used to diagnose the vertical motion in the stratosphere. Based on tracer observations from balloons and aircraft, the more sophisticated CCM scheme gives a better representation of the vertical transport in this model which includes the troposphere. The higher resolution model generally produces larger chemical O3 depletion, which agrees better with observations.
The CTM results show that very early chemical ozone loss occurred in December 2002 due to extremely low temperatures and early chlorine activation in the lower stratosphere. Thus, chemical loss in this winter started earlier than in the other two winters studied here. In 2002/2003 the local polar ozone loss in the lower stratosphere was ~40% before the stratospheric final warming. Larger ozone loss occurred in the cold year 1999/2000 which had a persistently cold and stable vortex during most of the winter. For this winter the current model, at a resolution of 2.8°×2.8°, can reproduce the observed loss of over 70% locally. In the warm and more disturbed winter 2003/2004 the chemical O3 loss was generally much smaller, except above 620 K where large losses occurred due to a period of very low minimum temperatures at these altitudes.
Two aircraft instruments for the measurement of total odd nitrogen (NOy) were compared side by side aboard a Learjet A35 in April 2003 during a campaign of the AFO2000 project SPURT (Spurengastransport in der Tropopausenregion). The instruments albeit employing the same measurement principle (gold converter and chemiluminescence) had different inlet configurations. The ECO-Physics instrument operated by ETH-Zürich in SPURT had the gold converter mounted outside the aircraft, whereas the instrument operated by FZ-Jülich in the European project MOZAIC III (Measurements of ozone, water vapour, carbon monoxide and nitrogen oxides aboard Airbus A340 in-service aircraft) employed a Rosemount probe with 80 cm of FEP-tubing connecting the inlet to the gold converter. The NOy concentrations during the flight ranged between 0.3 and 3 ppb. The two data sets were compared in a blind fashion and each team followed its normal operating procedures. On average, the measurements agreed within 6%, i.e. within the combined uncertainty of the two instruments. This puts an upper limit on potential losses of HNO3 in the Rosemount inlet of the MOZAIC instrument. Larger transient deviations were observed during periods after calibrations and when the aircraft entered the stratosphere. The time lag of the MOZAIC instrument observed in these instances is in accordance with the time constant of the MOZAIC inlet line determined in the laboratory for HNO3.
Two aircraft instruments for the measurement of total odd nitrogen (NOy) were compared side by side aboard a Learjet A35 in April 2003 during a campaign of the AFO2000 project SPURT (Spurengastransport in der Tropopausenregion). The instruments albeit employing the same measurement principle (gold converter and chemiluminescence) had different inlet configurations. The ECO-Physics instrument operated by ETH-Zürich in SPURT had the gold converter mounted outside the aircraft, whereas the instrument operated by FZ-Jülich in the European project MOZAIC III (Measurements of ozone, water vapour, carbon monoxide and nitrogen oxides aboard Airbus A340 in-service aircraft) employed a Rosemount probe with 80 cm of FEP-tubing connecting the inlet to the gold converter. The NOy concentrations during the flight ranged between 0.3 and 3 ppb. The two data sets were compared in a blind fashion and each team followed its normal operating procedures. On average, the measurements agreed within 7%, i.e. within the combined uncertainty of the two instruments. This puts an upper limit on potential losses of HNO3 in the Rosemount inlet of the MOZAIC instrument. Larger transient deviations were observed during periods after calibrations and when the aircraft entered the stratosphere. The time lag of the MOZAIC instrument observed in these instances is in accordance with the time constant of the MOZAIC inlet line determined in the laboratory for HNO3.
Numerical simulation of flow, H₂SO₄ cycle and new particle formation in the CERN CLOUD chamber
(2011)
To study the effect of galactic cosmic rays on aerosols and clouds, the Cosmic Leaving OUtdoor Droplets (CLOUD) project was established. Experiments are carried out at a 26 m3 tank at CERN (Switzerland). In the experiments, the effect of ionising particle radiation on H2SO4 particle formation and growth is investigated. To evaluate the experimental configuration, the experiment was simulated using a coupled multidimensional CFD – particle model (CLOUD-FPM). In the model the coupled fields of gas/vapour species, temperature, flow velocity and particle properties were computed to investigate the tank's mixing state and mixing times. Simulation results show that the mixing state of the tank's contents largely depends on the characteristics of the mixing fans and a 1-fan configuration, as used in first experiments, may not be sufficient to ensure a homogeneously mixed chamber. To mix the tank properly, 2 fans are necessary. The 1/e response times for instantaneous changes of wall temperature and saturation ratio inside the chamber were found to be in the order of few minutes. Particle nucleation and growth was also simulated and particle number size distribution properties of the freshly nucleated particles (particle number, mean size, standard deviation of the assumed log-normal distribution) were found to be mixed over the tank's volume similar to the gas species.
To study the effect of galactic cosmic rays on aerosols and clouds, the Cosmics Leaving OUtdoor Droplets (CLOUD) project was established. Experiments are carried out at a 26.1 m3 tank at CERN (Switzerland). In the experiments, the effect of ionizing radiation on H2SO4 particle formation and growth is investigated. To evaluate the experimental configuration, the experiment was simulated using a coupled multidimensional computational fluid dynamics (CFD) – particle model. In the model the coupled fields of gas/vapor species, temperature, flow velocity and particle properties were computed to investigate mixing state and mixing times of the CLOUD tank's contents. Simulation results show that a 1-fan configuration, as used in first experiments, may not be sufficient to ensure a homogeneously mixed chamber. To mix the tank properly, two fans and sufficiently high fan speeds are necessary. The 1/e response times for instantaneous changes of wall temperature and saturation ratio were found to be in the order of few minutes. Particle nucleation and growth was also simulated and particle number size distribution properties of the freshly nucleated particles (particle number, mean size, standard deviation of the assumed log-normal distribution) were found to be distributed over the tank's volume similar to the gas species.
In this paper we present evidence that the observed increase in tropical upwelling after the year 2000 may be attributed to a change in the Brewer-Dobson circulation pattern. For this purpose, we use the concept of transit times derived from residual circulation trajectories and different in-situ measurements of ozone and nitrous dioxide. Observations from the Canadian midlatitude ozone profile record, probability density functions of in-situ N2O observations and a shift of the N2O-O3 correlation slopes, taken together, indicate that the increased upwelling in the tropics after the year 2000 appears to have triggered an intensification of tracer transport from the tropics into the extratropics in the lower stratosphere below about 500 K. This finding is corroborated by the fact that transit times along the shallow branch of the residual circulation into the LMS have decreased for the same time period (1993–2003). On a longer time scale (1979–2009), the transit time of the shallow residual circulation branch show a steady decrease of about −1 month/decade over the last 30 years, while the transit times of the deep branch remain unchanged. This highlights the fact that a change in the upwelling across the tropical tropopause is not a direct indicator for changes of the whole Brewer-Dobson circulation.
In this paper we present evidence that the observed increase in tropical upwelling after the year 2000 may be attributed to a change in the Brewer-Dobson circulation pattern. For this purpose, we use the concept of transit times derived from residual circulation trajectories and different in-situ measurements of ozone and nitrous dioxide. Observations from the Canadian midlatitude ozone profile record, probability density functions of in-situ N2O observations and a shift of the N2O-O3 correlation slopes, taken together, indicate that the increased upwelling in the tropics after the year 2000 appears to have triggered an intensification of tracer transport from the tropics into the extratropics in the lower stratosphere below about 500 K. This finding is corroborated by the fact that transit times along the shallow branch of the residual circulation into the LMS have decreased for the same time period (1993–2003). On a longer time scale (1979–2009), the transit time of the shallow residual circulation branch show a steady decrease of about −1 month/decade over the last 30 yr, while the transit times of the deep branch remain unchanged. This highlights that changes in the upwelling across the tropical tropopause are not sufficient as an indicator for changes in the entire Brewer-Dobson circulation.
Yuanmou Basin of Yunnan, SW China, is a famous locality with hominids, hominoids, mammals and plant fossils. Based on the published megaflora and palynoflora data from Yuanmou Basin, the climate of Late Pliocene is reconstructed using the Coexistence Approach. The results indicate a warm and humid subtropical climate with a mean annual temperature of ca. 16–17°C and a mean annual precipitation of ca. 1500–1600 mm in the Late Pliocene rather than a dry, hot climate today, which may be due to the local tectonic change and gradual intensification of India monsoon. The comparison of Late Pliocene climate in Eryuan, Yangyi, Longling, and Yuanmou Basin of Yunnan Province suggests that the mean annual temperatures generally show a latitudinal gradient and fit well with their geographic position, while the mean annual precipitations seem to be related to the different geometries of the valleys under the same monsoon system.
We have analysed the microseismic activity within the Rwenzori Mountains area in the western branch of the East African Rift. Seismogram recordings from a temporary array of up to 27 stations reveal approximately 800 events per month with local magnitudes ranging from –0.5 to 5.1. The earthquake distribution is highly heterogeneous. The majority of located events lie within faults zones to the East and West of the Rwenzoris with the highest seismic activity observed in the northeastern area, where the mountains are in contact with the rift shoulders. The hypocentral depth distribution exhibits a pronounced peak of seismic energy release at 15 km depth. The maximum extent of seismicity ranges from 20 to 32 km and correlates well with Moho depths that were derived from teleseismic receiver functions. We observe two general features: (i) beneath the rift shoulders seismicity extends from the surface down to ca. 30 km depth; (ii) beneath the rift valley seismicity is confined to depths greater than 10 km. From the observations there is no indication for a crustal root beneath the Rwenzori Mountains. The magnitude frequency distribution reveals a b-value of 1.1, which is consistent with the hypothesis that part of the seismicity is caused by magmatic processes within the crust. Fault plane solutions of 304 events were derived from P-polarities and SV/P amplitude ratios. More than 70 % of the source mechanisms exhibit pure or predominantly normal faulting. T-axis trends are highly uniform and oriented WNW-ESE, which is perpendicular to the rift axis and in good agreement with kinematic rift models. At the northernmost part of the region we observe a rotation of the T-axis trends to NEN-SWS, which may be indicative of a local perturbation of the regional stress field.
Spatial variations of nitrogen trace gas emissions from tropical mountain forests in Nyungwe, Rwanda
(2012)
Globally, tropical forest soils represent the second largest source of N2O and NO. However, there is still considerable uncertainty on the spatial variability and soil properties controlling N trace gas emission. Therefore, we carried out an incubation experiment with soils from 31 locations in the Nyungwe tropical mountain forest in southwestern Rwanda. All soils were incubated at three different moisture levels (50, 70 and 90 % water filled pore space (WFPS)) at 17 °C. Nitrous oxide emission varied between 4.5 and 400 μg N m−2 h−1, while NO emission varied from 6.6 to 265 μg N m−2 h−1. Mean N2O emission at different moisture levels was 46.5 ± 11.1 (50 %WFPS), 71.7 ± 11.5 (70 %WFPS) and 98.8 ± 16.4 (90 %WFPS) μg N m−2 h−1, while mean NO emission was 69.3 ± 9.3 (50 %WFPS), 47.1 ± 5.8 (70 %WFPS) and 36.1 ± 4.2 (90 %WFPS) μg N m−2 h−1. The latter suggests that climate (i.e. dry vs. wet season) controls N2O and NO emissions. Positive correlations with soil carbon and nitrogen indicate a biological control over N2O and NO production. But interestingly N2O and NO emissions also showed a positive correlation with free iron and a negative correlation with soil pH (only N2O). The latter suggest that chemo-denitrification might, at least for N2O, be an important production pathway. In conclusion improved understanding and process based modeling of N trace gas emission from tropical forests will benefit from spatially explicit trace gas emission estimates linked to basic soil property data and differentiating between biological and chemical pathways for N trace gas formation.
The Late Miocene (11.6–5.3 Ma) is a crucial period in the history of the Asian monsoon. Significant changes in the Asian climate regime have been documented for this period, which saw the formation of the modern Asian monsoon system. However, the spatiotemporal structure of these changes is still ambiguous, and the associated mechanisms are debated. Here, we present a simulation of the average state of the Asian monsoon climate for the Tortonian (11–7 Ma) using the regional climate model CCLM3.2. We employ relatively high spatial resolution (1° × 1°) and adapt the physical boundary conditions such as topography, land-sea distribution and vegetation in the regional model to represent the Late Miocene. As climatological forcing, the output of a Tortonian run with a fully-coupled atmosphere-ocean general circulation model is used. Our regional Tortonian run shows a stronger-than-present East Asian winter monsoon wind as a result of the enhanced mid-latitude westerly wind of our global forcing and the lowered present-day northern Tibetan Plateau in the regional model. The summer monsoon circulation is generally weakened in our regional Tortonian run compared to today. However, the changes of summer monsoon precipitation exhibit major regional differences. Precipitation decreases in northern China and northern India, but increases in southern China, the western coast and the southern tip of India. This can be attributed to the changes in both the regional topography (e.g. the lower northern Tibetan Plateau) and the global climate conditions (e.g. the higher sea surface temperature). The spread of dry summer conditions over northern China and northern Pakistan in our Tortonian run further implies that the monsoonal climate may not have been fully established in these regions in the Tortonian. Compared with the global model, the high resolution regional model highlights the spatial differences of the Asian monsoon climate in the Tortonian, and better characterizes the convective activity and its response to regional topographical changes. It therefore provides a useful and compared to global models, a complementary tool to improve our understanding of the Asian monsoon evolution in the Late Miocene.
Wenn Klimaforscher wissen wollen, was die Zukunft
bringt, schauen sie gern in die Vergangenheit. Während
der Kreidezeit herrschte auf der Erde ein Treibhausklima
mit atmosphärischen CO2-Gehalten, die weitaus
höher waren als heute. Welche Konsequenzen das für
die Meeresströmungen und die marinen Ökosysteme
hatte, können Geowissenschaftler heute nicht mehr direkt
messen. Bei der Spurensuche helfen ihnen die
Fossilien mikroskopisch kleiner Einzeller, deren wunderschöne
Kalkschalen als Klimagedächtnis dienen.
Occurrence and sources of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) in the aquatic environment
(2011)
The aim of the present study was to identify the sources of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) into the aquatic environment and to investigate its occurrence in rivers and wastewater treatment plants (WWTPs). Therefore, TMDD was analyzed in 441 wastewater samples from influents and effluents of 27 municipal WWTPs, in 6 sludge samples, in 52 wastewater samples from 3 sewage systems of municipal WWTPs, in 489 surface samples from 24 rivers, in 9 wastewater samples of 3 paper-recycling industries and in 65 groundwater samples. TMDD was also analyzed in household paper products, in 23 samples of toilet
papers, in 5 types of paper towels and in 12 types of paper tissues. The samples were collected between 2007 and 2011. The water samples were extracted with solid phase extraction (SPE) and the household paper samples with Soxhlet extraction. Gas chromatography-mass spectrometry (GC-MS) was used for quantification purposes. Between November 2007 and January 2008, TMDD was detected in the river Rhine at Worms with permanent high concentrations (up to 1330 ng/L). The results showed that TMDD is uniformly distributed across the river at Worms. An increase of the mean TMDD concentration from approximately 500 ng/L to 1000 ng/L was registered in January 2008. Due to the minor fluctuations of the TMDD concentration during the sampling period it is expected that the input of TMDD into the river is continuous. Therefore, TMDD might rather originate from effluents of municipal WWTPs than from temporal sources. The mean TMDD load based on the analysis of 147 water samples collected in the River Rhine was 62.8 kg/d which is equivalent to 23 t/a suggesting that TMDD must be used and/or produced in high quantities in order to be found in those high concentrations. To determine if TMDD is discharged by effluents of municipal WWTPs into the rivers, 24 hours influent and effluent samples of four municipal WWTPs in the Frankfurt/Rhine-Main metropolitan region were collected during November 2008 and February 2010 and analyzed for TMDD. The TMDD influent concentrations varied between 134 ng/L and 5846 ng/L and the effluent concentrations between <LOQ (limit of quantitation) and 3539 ng/L. The TMDD elimination rates in the four WWTPs varied between 33% and 68%. The results showed that effluents of municipal WWTPs are an important source of TMDD in the aquatic environment because TMDD is not completely removed from the sewage during the wastewater treatment. Weekly and daily variations of the TMDD concentration in the influents of two municipal WWTPs indicated that both private households and indirect industrial dischargers contribute to the introduction of TMDD into the municipal sewage systems. A more detailed study of the TMDD elimination rate in the different wastewater treatment stages was carried out in the WWTP Niederrad/Griesheim in Frankfurt am Main. The results showed that the removal of TMDD is mainly carried out during the aerobic biological treatments, where the elimination rate was 46%. In contrast, during the anoxic treatment the removal efficiency was only 1.4% and during the mechanical treatment the elimination rate was 19%. To determine the sources of TMDD in the sewage, household paper products (paper tissues, toilet papers and paper towels) were analyzed for TMDD using Soxhlet extraction. TMDD was detected in 83% of the samples (n=40). The highest mean TMDD concentrations were found in recycled toilet paper (0.20 μg/g) and in paper towels (0.11 μg/g). In paper tissues and non-recycled toilet paper the mean TMDD concentrations were lower 0.080 μg/g and 0.025 μg/g respectively. According to these results the high TMDD influent concentrations found previously in municipal WWTPs (mean 1.20 μg/L) cannot be explained due to migration of TMDD from the household paper products into the sewage. Thus indirect industrial dischargers are the cause of the high influent TMDD concentrations. Effluents of municipal WWTPs with different indirect industrial dischargers (textile-, metal processing-, food processing-, electroplating-, paper-recycling- and printing ink factories) were analyzed. The highest mean TMDD concentrations were found in the effluents of municipal WWTPs that have paper-recycling (71.3 μg/L) and printing ink factories (138 μg/L) as indirect industrial dischargers. These results were confirmed by analyzing process wastewater of three paper-recycling factories located in Germany. High TMDD concentrations were detected and fluctuated between 1.83 μg/L and 113 μg/L. TMDD was also analyzed in the wastewater of a non-recycling-paper factory but its concentration was much lower (0.066 μg/L) indicating that TMDD is introduced into the processing water during the papermaking process due to the use of waste paper. Analyses of wastewater samples from different parts of the sewage pipes of a municipal WWTP in Hesse, which receives the wastewater from a printing ink factory, were carried out. The TMDD concentration in the wastewater sample from the sewage pipe of the printing ink factory was much higher (3,300 μg/L) than the TMDD concentration detected in the other wastewater samples from the sewage system (0.030 μg/L – 0.89 g/L). These results confirm the printing ink production as one of the principal sources of TMDD in the sewage. Analysis of surface water samples of the River Modau downstream from the effluent of the WWTP Nieder-Ramstadt showed TMDD concentrations of up to 28.0 μg/L. These high TMDD concentrations might be caused by the indirect wastewater discharges of a paint factory connected to the municipal sewage system. These results indicate that TMDD is introduced into the municipal WWTPs principally by indirect industrial dischargers and they are mainly paint and printing ink factories. The paper-recycling factories also represent an important source of TMDD in municipal WWTPs but indirectly. According to statements given by the representatives of two paper recycling factories neither TMDD or any other TMDD containing product is used or added during the papermaking process. Therefore, TMDD is washed out from the printing inks of the coloured waste paper and concentrated in the process wastewater in the closed water circuits of paper-recycling factories reaching rivers and municipal WWTPs. The occurrence and distribution of TMDD in surface waters in Germany was also studied. The results showed that TMDD is widely distributed across different rivers systems in the federal states of Hesse, North-Rhine-Westphalia, Bavaria, Baden-Wuerttemberg and Rhineland-Palatinate. In Hesse, TMDD was detected in the some of main rivers with mean concentrations of 812 ng/L (Schwarzbach, Hessian Ried), 374 ng/L (Kinzig), 393 ng/L (Main, at Frankfurt), 539 ng/L (Werra), 326 ng/L (Fulda), 151 ng/L (Emsbach) and 161 ng/L (Nidda). In small rivers (creeks) the mean TMDD concentrations varied between <LOQ (Diemel, Urselbach) and 1890 ng/L (Darmbach). The results showed that the TMDD concentrations in creeks are highly influenced by both effluents of WWTPs and by the distance between the sampling point and the nearest WWTP. Surface samples from sampling locations downstream from WWTPs dischargers showed higher TMDD concentrations (mean 518 ng/L) than sampling locations upstream from WWTPs dischargers (mean 35.1 ng/L). The behavior of TMDD during bank filtration was investigated at two locations, at a water utility company at the Lower River Rhine (urban area) and at the Oderbruch polder (rural area). The results indicated that TMDD is removed from the surface water by bank filtration at both sampling locations. The removal process is probably carried out in the first meters of the aquifer (hyporheic zone) by biodegradation processes, since TMDD does not tend to be absorbed by sediments and it was not found in the groundwater of monitoring wells. In groundwater samples from the Hessian Ried (n=23) TMDD was found only in five samples and the highest TMDD concentration was 135 ng/L. According to these results, TMDD does not represent a concern for drinking water in Germany, since it does not reach the groundwater with high concentrations and it has a low toxicity potential. The input of TMDD into the North Sea was estimated to be 60.7 t/a by considering the mean transported loads of TMDD by the River Rhine at Wesel (58.3 t/a) and Meuse in the Netherlands (2.40 t/a). The estimated discharge of TMDD by German municipal WWTPs (8.19 t/a) and paper-recycling factories (9.24 t/a) into rivers seems to be too low considering that the mean TMDD load in the River Rhine downstream from Wesel is 58.3 t/a. However, due to the high density of population and industries at the Lower Rhine it is expected that more relevant sources of TMDD are located along the Rhine River increasing the transported load. According to the results of this PhD project TMDD is a non-ionic surfactant contained in products, which are applied on surfaces (printing inks and paints) and has the potential to reach the aquatic environment. Therefore, TMDD should fulfill the requirement of a biodegradability of 80% established by the “Law on the Environmental Impact of Detergents and Cleaning Products” in Germany. However, due to the partial elimination rates of TMDD obtained in municipal WWTPs (between 33% and 68%) and to the absence of information about the execution of the biodegradation test on TMDD, it is unknown if TMDD is in accordance with this law. Otherwise, its use as surfactant in such products is questionable.
Sedimentbilanzen haben sich als Methode zur Quantifizierung von Sedimentflüssen in Raum und Zeit in den Geowissenschaften etabliert. Sie eröffnen die Möglichkeit, differenzierte Aus¬sagen über die Erosions- und Sedimentationsdynamik von Einzugsgebieten zu treffen. Ziel der vorliegenden Arbeit ist es, die holozäne Erosions- und Sedimentationsentwicklung im mesoskaligen Mittelgebirgseinzugsgebiet des Speyerbachs im Pfälzerwald zu erfassen, und räumlich und zeitlich möglichst differenziert darzulegen. Um Langzeit-Sedimentbilanzen für den Speyerbach zu berechnen wurden verfügbare Daten zum Boden, eine eigene Kartierung der Erosion und Sedimentation sowie eine intensive (OSL und 14C-) Datierung zweier Stand¬orte durchgeführt. Die Sedimente wurden durch eine direkte Kartierung erfasst. Die Erosions¬tiefe errechnet sich aus der Subtraktion der aktuellen Mächtigkeit der Hauptlagen und der Parabraunerden vom initialen Zustand (= Berechnungsgrundlage).
Die Sedimentbilanz I basiert auf öffentlich zugänglichen bodenkundlichen Punkt- und Flächendaten und hat eine Erosion von ~27 Mio. m³ mit einem Einzugsgebiets-Sedimentaus¬tragsverhältnis (CSDR) von 31,5 % ergeben. Die Sensitivitätsanalyse belegt eine hohe Abhängigkeit des Ergebnisses von der Wahl der Berechnungsgrundlage. Aufgrund fehlender Daten sind eine höhere räumliche Auflösung sowie Aussagen zur zeitlichen Entwicklung nicht möglich.
Die Berechnung der Sedimentbilanz II erfolgte auf der Grundlage eigens erhobener Punkt- und Flächendaten, womit die Anwendung eines nested approach möglich wurde: Neben der Gesamtbilanz für den Speyerbach (sechste Strahler-Ordnung) wurden Bilanzen für Teilein¬zugsgebiete erster und vierter Strahler-Ordnung erstellt, anhand derer die Skalenabhängigkeit der Sedimentdynamik diskutiert werden konnte. Es wurden ~109 Mio. m³ und ein CSDR von 5 % errechnet und ebenfalls eine hohe Sensitivität gegenüber der Änderung der Erosionstiefen festgestellt.
Die erfolgreiche Datierung von periglazialen Deckschichten zweier Bodenprofile unterstützt die Ergebnisse der Landnutzungsrekonstruktion aus Literaturdaten und historischen Karten und zeigt, dass in den Tälchen erster Ordnung Erosion verstärkt in der Neuzeit stattfand. Nur in den lösslehmbeeinflussten Gebieten hat sich die Besiedlung im Frühmittelalter in der Ablagerung von Bodensedimenten abgebildet. Es wurden frühholozäne Umlagerungsprozesse am Hang identifiziert. Aufgrund der guten Datierungseigenschaften der sandigen periglazia¬len Lagen wäre das Untersuchungsgebiet geeignet, der Frage nach der Parallelisierung der frühholozänen Umlagerungen von Hangsedimenten mit Klimaschwankungen nachzugehen.
Die vorliegende Arbeit liefert mit den erstellten Sedimentbilanzen und der Darlegung der Landnutzungsverhältnisse ein regionales Beispiel für Mittelgebirgsräume im Rhein-Einzugs¬gebiet. Die mikro- bis mesoskaligen Ergebnisse folgen der generellen Tendenz anderer welt¬weiter Studien, wonach die Sedimentaustragsverhältnisse mit steigender Einzugsgebietsgröße abnehmen. Die Werte der Sedimentbilanz II liegen jedoch deutlich unter denen der Lössge¬biete und belegen, dass sich die Zwischenspeicherung in der Mittelgebirgsregion höher ist. Die räumliche Differenzierung zeigt regionale Unterschiede, die auf der Zugänglichkeit, der administrativen Zugehörigkeit und die naturräumliche Ausstattung zurückzuführen sind. Arbeiten in anderen Sandsteinregionen Deutschlands sind derzeit im Gange und werden in Zukunft eine Einschätzung der vorliegenden Untersuchung zulassen.
The aim of this study is a better understanding of radiation processes in regional climate models (RCMs) in order to quantify their impact and to reduce possible errors. A first important task in finding an answer to this question was to examine the accuracy of the components of the radiation budget in regional climate simulations. To this end, the simulated radiation budgets of two regional climate simulations for Europe were compared with a satellite-based reference. In the simulations with the RCM COSMO-CLM there were some serious under- and overestimations of short- and long-wave net radiation in Europe. However, taking into account the differences in the reference datasets, the results of the COSMO-CLM were quite satisfactory.
Using statistical methods, the influence of potential sources of uncertainties was estimated. Uncertainties in the cloud cover and surface albedo had a significant impact on uncertainties in short-wave net radiation, the explained variance of uncertainties in cloud cover was two to three times higher than that of uncertainties in surface albedo. Uncertainties in the cloud cover resulted in significant errors in the net long-wave radiation. However, the influence of uncertainties in soil temperature on errors in the long-wave radiation budget was low or even negligible. These results were confirmed in a comparison with simulations of the REMO and ALADIN regional climate models. It is reasonable to expect that a better parameterization of relatively simple parameters such as cloud cover and surface albedo is a means of significantly improving the simulation of radiation budget components in the COSMO-CLM.
An important question for the application of RCMs is to examine whether the results of radiation uncertainties and their impact factors are comparable if the model is applied in a region that is not the one for which it was originally created. Comparisons of the simulated radiation budgets of different RCMs for West Africa showed that problems in the simulation of short- and long-wave radiation fluxes were a widespread problem. Most of the tested models showed some considerable under- or overestimation of the short- and long-wave radiation fluxes.
Similar to Europe uncertainties in cloud cover were also in the simulations for Africa a significant factor affecting uncertainties in the simulated radiation fluxes. However, for the African simulations uncertainties in the parameterization of surface albedo were much more important than in Europe. On average, overland uncertainties in the cloud cover and surface albedo were of similar importance. Uncertainties in soil temperature simulations were of higher importance in Africa, and reached overland similar values of the mean explained variance (R2 ≈ 0.2) such as uncertainties in the cloud cover. This indicates a geographical dependence of the model error. This study confirmed the assumption that an improved parameterization of relatively simple parameters such as the surface albedo in RCMs leads to a significant improvement in the modeled radiation budget, particularly in Africa.
The influence of errors in the simulated radiation budget components on the simulation of climate processes, such as the West-African monsoon (WAM), was investigated in a next step. The evaluation of ERA-Interim and ECHAM5 driven COSMO-CLM simulations for Africa showed that the main features of the WAM were well reproduced by the model, but there were only slight improvements compared to the driving data. The index of convective activity in the model simulations was much too high and precipitation was underestimated in large parts of tropical Africa. The partly considerable differences between the ERA-Interim and ECHAM5 driven simulations demonstrated the sensitivity of the RCM to the boundary conditions and in particular to the sea surface temperature. An excessive northwards shift of the monsoon in the model was influenced by the land-sea temperature gradient and the strength of the Saharan heat low. Consequently, a part of the error was due to the driving data and the model itself produced another part.
By modifying the parameterization of the bare soil albedo the errors in the radiation budget and 2 m temperature in the Sahara region were significantly reduced. Similarly, the overesti-mation of precipitation and convection has been reduced in the Sahel. The effect of this modifi-cation on the examined WAM area was low. This confirmed that especially in desert regions, errors in the surface albedo were a driving factor for errors in the radiation budget. However, there are other important factors not yet sufficiently understood that have a strong influence on the quality of the simulation of the WAM.
The analysis of the actual state, the quantification of error sources and the highlighting of connections made it possible to find means to reduce uncertainties in the simulated radiation in RCMs and to have a better understanding of radiation processes. However, the magnitude of the errors found, the number of possible influencing factors, and the complexity of interactions, indicate that there is still a need for further research in this area.
In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6) cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm.
Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10−4 g m−3. All known in situ measurements of subvisual tropopause cirrus are compared and an exponential fit on the size distributions is established for modelling purposes.
A comparison of aerosol to ice crystal number concentrations, in order to obtain an estimate on how many ice particles may result from activation of the present aerosol, yielded low ratios for the subvisual cirrus cases of roughly one cloud particle per 30 000 aerosol particles, while for the MCS outflow cases this resulted in a high ratio of one cloud particle per 300 aerosol particles.
Globally, tropical forest soils represent the second largest source of N2O and NO. However, there is still considerable uncertainty on the spatial variability and soil properties controlling N trace gas emission. To investigate how soil properties affect N2O and NO emission, we carried out an incubation experiment with soils from 31 locations in the Nyungwe tropical mountain forest in southwestern Rwanda. All soils were incubated at three different moisture levels (50, 70 and 90% water filled pore space (WFPS)) at 17 °C. Nitrous oxide emission varied between 4.5 and 400 μg N m−2 h−1, while NO emission varied from 6.6 to 265 μg N m−2 h−1. Mean N2O emission at different moisture levels was 46.5 ± 11.1 (50% WFPS), 71.7 ± 11.5 (70% WFPS) and 98.8 ± 16.4 (90% WFPS) μg N m−2 h−1, while mean NO emission was 69.3 ± 9.3 (50% WFPS), 47.1 ± 5.8 (70% WFPS) and 36.1 ± 4.2 (90% WFPS) μg N m−2 h−1. The latter suggests that climate (i.e. dry vs. wet season) controls N2O and NO emissions. Positive correlations with soil carbon and nitrogen indicate a biological control over N2O and NO production. But interestingly N2O and NO emissions also showed a negative correlation (only N2O) with soil pH and a positive correlation with free iron. The latter suggest that chemo-denitrification might, at least for N2O, be an important production pathway. In conclusion improved understanding and process based modeling of N trace gas emission from tropical forests will not only benefit from better spatial explicit trace gas emission and basic soil property monitoring, but also by differentiating between biological and chemical pathways for N trace gas formation.
Calibration of TCCON column-averaged CO₂: the first aircraft campaign over European TCCON sites
(2011)
The Total Carbon Column Observing Network (TCCON) is a ground-based network of Fourier Transform Spectrometer (FTS) sites around the globe, where the column abundances of CO2, CH4, N2O, CO and O2 are measured. CO2 is constrained with a precision better than 0.25% (1-σ). To achieve a similarly high accuracy, calibration to World Meteorological Organization (WMO) standards is required. This paper introduces the first aircraft calibration campaign of five European TCCON sites and a mobile FTS instrument. A series of WMO standards in-situ profiles were obtained over European TCCON sites via aircraft and compared with retrievals of CO2 column amounts from the TCCON instruments. The results of the campaign show that the FTS measurements are consistently biased 1.1% ± 0.2% low with respect to WMO standards, in agreement with previous TCCON calibration campaigns. The standard a priori profile for the TCCON FTS retrievals is shown to not add a bias. The same calibration factor is generated using aircraft profiles as a priori and with the TCCON standard a priori. With a calibration to WMO standards, the highly precise TCCON CO2 measurements of total column concentrations provide a suitable database for the calibration and validation of nadir-viewing satellites
Calibration of TCCON column-averaged CO₂: the first aircraft campaign over European TCCON sites
(2011)
The Total Carbon Column Observing Network (TCCON) is a ground-based network of Fourier Transform Spectrometer (FTS) sites around the globe, where the column abundances of CO2, CH4, N2O, CO and O2 are measured. CO2 is constrained with a precision better than 0.25 %. To achieve a similarly high accuracy, calibration to World Meteorological Organization (WMO) standards is required. This paper introduces the first aircraft calibration campaign of five European TCCON sites and a mobile FTS instrument. A series of WMO standards in-situ profiles were obtained over European TCCON sites via aircraft and compared with retrievals of CO2 column amounts from the TCCON instruments. The results of the campaign show that the FTS measurements are consistently biased 1.0 % ± 0.2 % low with respect to WMO standards, in agreement with previous TCCON calibration campaigns. The standard a priori profile for the TCCON FTS retrievals is shown to not add a bias. The same calibration factor is generated using aircraft profiles as a priori and with the TCCON standard a priori. With a calibration to WMO standards, the highly precise TCCON CO2 measurements of total column concentrations provide a suitable database for the calibration and validation of nadir-viewing satellites.
Soil biogenic NO emissions (SNOx) play important direct and indirect roles in chemical processes of the troposphere. The most widely applied algorithm to calculate SNOx in global models was published 15 years ago by Yienger and Levy (1995), was based on very few measurements. Since then numerous new measurements have been published, which we used to build up a atabase of field measurements conducted world wide covering the period from 1978 to 2009, including 108 publications with 560 measurements.
Recently, several satellite based top-down approaches, which recalculated the different sources of NOx (fossil fuel, biomass burning, soil and lightning), have shown an underestimation of SNOx by the algorithm of Yienger and Levy (1995). Nevertheless, to our knowledge no general improvements of this algorithm have yet been published.
Here we present major improvements to the algorithm, which should help to optimize the representation of SNOx in atmospheric-chemistry global climate models, without modifying the underlying principal or mathematical equations. The changes include: 1) Using a new up to date land cover map, with twice the number of land cover classes, and using annually varying fertilizer application rates; 2) Adopting the fraction of SNOx induced by fertilizer application based on our database; 3) Switching from soil water column to volumetric soil moisture, to distinguish between the wet and dry state; 4) Tuning the emission factors to reproduce the measured emissions in our database and calculate the emissions based on their mean value. These steps lead us to increased global yearly SNOx, and our total SNOx source ends up being close to one of the top-down approaches. In some geographical regions the new results agree better with the top-down approach, but there are also distinct differences in other regions. This suggests that a ombination of both top-down and bottom-up approaches could be combined in a future attempt to provide an even better calculation of SNOx.
Biogenic NO emissions from soils (SNOx) play important direct and indirect roles in tropospheric chemistry. The most widely applied algorithm to calculate SNOx in global models was published 15 years ago by Yienger and Levy (1995), and was based on very few measurements. Since then, numerous new measurements have been published, which we used to build up a compilation of world wide field measurements covering the period from 1978 to 2010. Recently, several satellite-based top-down approaches, which recalculated the different sources of NOx (fossil fuel, biomass burning, soil and lightning), have shown an underestimation of SNOx by the algorithm of Yienger and Levy (1995). Nevertheless, to our knowledge no general improvements of this algorithm, besides suggested scalings of the total source magnitude, have yet been published. Here we present major improvements to the algorithm, which should help to optimize the representation of SNOx in atmospheric-chemistry global climate models, without modifying the underlying principals or mathematical equations. The changes include: (1) using a new landcover map, with twice the number of landcover classes, and using annually varying fertilizer application rates; (2) adopting a fraction of 1.0 % for the applied fertilizer lost as NO, based on our compilation of measurements; (3) using the volumetric soil moisture to distinguish between the wet and dry states; and (4) adjusting the emission factors to reproduce the measured emissions in our compilation (based on either their geometric or arithmetic mean values). These steps lead to increased global annual SNOx, and our total above canopy SNOx source of 8.6 Tg yr−1 (using the geometric mean) ends up being close to one of the satellite-based top-down approaches (8.9 Tg yr−1). The above canopy SNOx source using the arithmetic mean is 27.6 Tg yr−1, which is higher than all previous estimates, but compares better with a regional top-down study in eastern China. This suggests that both top-down and bottom-up approaches will be needed in future attempts to provide a better calculation of SNOx.
Residual circulation trajectories and transit times into the extratropical lowermost stratosphere
(2011)
Transport into the extratropical lowermost stratosphere (LMS) can be divided into a slow part (time-scale of several months to years) associated with the global-scale stratospheric residual circulation and a fast part (time-scale of days to a few months) associated with (mostly quasi-horizontal) mixing (i.e. two-way irreversible transport, including extratropical stratosphere-troposphere exchange). The stratospheric residual circulation may be considered to consist of two branches: a deep branch more strongly associated with planetary waves breaking in the middle to upper stratosphere, and a shallow branch associated with synoptic and planetary scale waves breaking in the subtropical lower stratosphere. In this study the contribution due to the stratospheric residual circulation alone to transport into the LMS is quantified using residual circulation trajectories, i.e. trajectories driven by the (time-dependent) residual mean meridional and vertical velocities. This contribution represents the advective part of the overall transport into the LMS and can be viewed as providing a background onto which the effect of mixing has to be added. Residual mean velocities are obtained from a comprehensive chemistry-climate model as well as from reanalysis data. Transit times of air traveling from the tropical tropopause to the LMS along the residual circulation streamfunction are evaluated and compared to recent mean age of air estimates. A time-scale separation with much smaller transit times into the mid-latitudinal LMS than into polar LMS is found that is indicative of a separation of the shallow from the deep branch of the residual circulation. This separation between the shallow and the deep circulation branch is further manifested in a distinction in the aspect ratio of the vertical to meridional extent of the trajectories, the integrated mass flux along the residual circulation trajectories, as well as the stratospheric entry latitude of the trajectories. The residual transit time distribution reproduces qualitatively the observed seasonal cycle of youngest air in the extratropical LMS in fall and oldest air in spring.
Residual circulation trajectories and transit times into the extratropical lowermost stratosphere
(2010)
Transport into the extratropical lowermost stratosphere (LMS) can be divided into a slow part (time-scale of several months to years) associated with the global-scale stratospheric residual circulation and a fast part (time-scale of days to a few months) associated with (mostly quasi-horizontal) mixing (i.e. two-way irreversible transport, including stratosphere-troposphere exchange). The stratospheric residual circulation can be considered to consist of two branches: a deep branch more strongly associated with planetary waves breaking in the middle to upper stratosphere, and a shallow branch more strongly associated with synoptic-scale waves breaking in the subtropical lower stratosphere. In this study the contribution due to the stratospheric residual circulation alone to transport into the LMS is quantified using residual circulation trajectories, i.e. trajectories driven by the (time-dependent) residual mean meridional and vertical velocities. This contribution represents the advective part of the overall transport into the LMS and can be viewed as providing a background onto which the effect of mixing has to be added. Residual mean velocities are obtained from a comprehensive chemistry-climate model as well as from reanalysis data. Transit times of air traveling from the tropical tropopause to the LMS along the residual circulation streamfunction are evaluated and compared to recent mean age of air estimates. A clear time-scale separation with much smaller transit times into the mid-latitudinal LMS than into polar LMS is found that is indicative of a clear separation of the shallow from the deep branch of the residual circulation. This separation between the shallow and the deep circulation branch is further manifested in a clear distinction in the aspect ratio of the vertical to meridional extent of the trajectories as well as the integrated mass flux along the residual circulation trajectories. The residual transit time distribution reproduces qualitatively the observed seasonal cycle of youngest air in the extratropical LMS in fall and oldest air in spring.
A complete, well-preserved record of the Cenomanian/Turonian (C/T) Oceanic Anoxic Event 2 (OAE-2) was recovered from Demerara Rise in the southern North Atlantic Ocean (ODP site 1260). Across this interval, we determined changes in the stable carbon isotopic composition of sulfur-bound phytane (δ13Cphytane, a biomarker for photosynthetic algae. The δ13Cphytane record shows a positive excursion at the onset of the OAE-2 interval, with an unusually large amplitude (~7 ‰) compared to existing C/T proto-North Atlantic δ13Cphytane records (3–6 ‰). Overall, the amplitude of the excursion of δ13Cphytane decreases with latitude. Using reconstructed sea surface temperature (SST) gradients for the proto-North Atlantic, we investigated environmental factors influencing the latitudinal δ13Cphytane gradient. The observed gradient is best explained by high productivity at DSDP Site 367 and Tarfaya basin before OAE-2, which changed in overall high productivity throughout the proto-North Atlantic during OAE-2. During OAE-2, productivity at site 1260 and 603B was thus more comparable to the mid-latitude sites. Using these constraints as well as the SST and δ13Cphytane-records from Site 1260, we subsequently reconstructed pCO2 levels across the OAE-2 interval. Accordingly, pCO2 decreased from ca. 1750 to 900 ppm during OAE-2, consistent with enhanced organic matter burial resulting in lowering pCO2. Whereas the onset of OAE-2 coincided with increased pCO2, in line with a volcanic trigger for this event, the observed cooling within OAE-2 probably resulted from CO2 sequestration in black shales outcompeting CO2 input into the atmosphere. Together these results show that the ice-free Cretaceous world was sensitive to changes in pCO2 related to perturbations of the global carbon cycle.