Up to recent years, the study of trends and variability of the salinity (and freshwater) distributions was hampered by the lack of temporal and spatial resolution of the available observations (Wang DFG form 54.011 - 1/12 page 3 of 6 et al., 2010). With the onset of the Argo programme, the number of observed salinity profiles have significantly increased. The many Argo profiles distributed evenly over the year provide not only the means to calculate seasonally averaged salinity (and freshwater) distributions, but they can also be used to calculate regional Gravest Empirical Modes (GEMs) parameterized by pressure and dynamic height. Dynamic height is measured by altimetry and high quality altimeter data are available since 1992. GEMs will be used to construct from altimetry high resolution (in time and space) salinity, temperature and density fields. The objectives of the proposal are to - combine Argo/CTD profiles and altimetry to calculate temporal and spatial high resolution salinity fields in the mixed layer and in the upper 1500-2000m for the time period 1992 - 2013 for the subpolar and the subtropical Atlantic. - Construct regional freshwater budgets for the mixed layer and the upper 1500-2000m and estimate the contributions of the main processes to the observed change - Follow salinity anomalies from their origin along their circulation pathways, and study involved mechanisms (for instance role of eddies, mean circulation) for shallow, intermediate and deep water masses - Investigate changes in the formation of North Atlantic mode waters in the subpolar and subtropical gyre
The Labrador Sea is one of the few places in the world ocean, where deep water formation takes place. This water is exported from the Labrador Sea to become part of the southward branch of the meridional overturning circulation. Previous observational work has largely focused on the role of deep convection in the interior of the Labrador Sea. Recent evidence from observations and numerical ocean models specifically indicate that processes near the ocean boundaries might be most relevant for both Eulerian downwelling of waters in the Labrador Sea and the fast export of newly transformed waters. We propose to analyze mooring based observations at the western margin of the Labrador Sea together with high resolution numerical model simulations to understand the role both processes play for the meridional overturning circulation in the subpolar North Atlantic. Specifically, we want to test (i) if (and where) downwelling occurs along the margins of the Labrador Sea, (ii) how downwelling relates to the seasonal evolution of convection and eddy activity, (iii) how fast waters newly transformed near the western margin of the Labrador Sea are exported, and (iv) how the two processes (downwelling, fast export) affect the temporal variability of the Atlantic meridional overturning circulation.
Laminierte Seesedimente sind unschätzbare Informationsquellen zur Geschichte der Umwelt und des Klimas direkt aus der Lebenssphäre des Menschen. Ein exzellentes Beispiel dafür ist der Sihailongwan-Maarsee aus NE-China. In einem immer noch dicht bewaldeten Vulkangebiet gelegen, bieten seine Sedimente ein ungestörtes Abbild der Monsunvariationen über zehntausende von Jahren. Nur die letzten ca. 200 Jahre zeigen einen deutlichen lokalen anthropogenen Einfluss. Das Monsunklima der Region mit Hauptniederschlägen während des Sommers und extrem kalten Wintern unter dem Einfluss des Sibirischen Hochdrucksystems bildet die Voraussetzung für die Bildung von saisonal deutlich geschichteten Sedimenten (Warven), die in dem tiefen Maarsee dann auch überwiegend ungestört erhalten bleiben. Insbesondere die Auftauphase im Frühjahr bringt einen regelmässigen Sedimenteintrag in den See, der das Gerüst für eine derzeit bis 65.000 Jahre vor heute zurückreichende Warvenchronologie bildet. Für das letzte Glazial zeigen Pollenspektren aus dem Sihailongwan-Profil Vegetationsvariationen im Gleichklang mit bekannten klimatischen Variationen des zirkum-nordatlantischen Raumes (Dansgaard-Oeschger-Zyklen) zu dieser Zeit. Der Einfluss dieser Warmphasen auf das Ökosystem See war jedoch sehr unterschiedlich. So sind die Warven aus den Dansgaard-Oeschger (D/O) Zyklen 14 bis 17 mit extrem dicken Diatomeenlagen (hauptsächlich Stephanodiscus parvus/minutulus) denen vom Beginn der spätglazialen Erwärmung zum Verwechseln ähnlich, während Warven aus dem D/O-Zyklus 8 kaum Unterschiede zu überwiegend klastischen Warven aus kalten Interstadialen aufweisen. Gradierte Ereignislagen mit umgelagertem Bodenmaterial sind deutliche Hinweise auf ein Permafrost-Regime während der Kaltphasen. Auch während des Spätglazials treten deutliche klimatische Schwankungen auf, die der in europäischen Sedimentarchiven definierten Gerzensee-Oszillation und der Jüngeren Dryas zeitlich exakt entsprechen. Das frühe Holozän ist von einer Vielzahl Chinesischer Paläoklima-Archive als Phase mit intensiverem Sommermonsun bekannt. Überraschenderweise sind die minerogenen Fluxraten im Sihailongwan-See während des frühen Holozäns trotz dichter Bewaldung des Einzugsgebietes sehr hoch. Sowohl Mikrofaziesanalysen der Sedimente als auch geochemische Untersuchungen deuten auf remoten Staub als Ursache dieses verstärkten klastischen Eintrags hin. Der insbesondere in den letzten Jahrzehnten zunehmende Einfluss des Menschen zeigt sich in den Sedimenten des Sihailongwan-Maarsees vor allem in einem wiederum zunehmenden Staubeintrag und einer Versauerung im Einzugsgebiet. Der anthropogene Einflusss auf die lokale Vegetation ist immer noch gering.
The present-day configuration of Indonesia and SE Asia is the results of a long history of tectonic movements, volcanisms and global eustatic sea-level changes. Not indifferent to these dynamics, fauna and flora have been evolving and dispersing following a complicate pattern of continent-sea changes to form what are today defined as Sundaland and Wallacea biogeographical regions. The modern intraannual climate of Indonesia is generally described as tropical, seasonally wet with seasonal reversals of prevailing low-level winds (Asian-Australian monsoon). However at the interannual scale a range of influences operating over varying time scales affect the local climate in respect of temporal and spatial distribution of rainfall. Vegetation generally reflects climate and to simplify it is possible to distinguish three main ecological elements in the flora of Malaysia: everwet tropical, seasonally dry tropical (monsoon) and montane. Within those major ecological groups, a wide range of specific local conditions caused a complex biogeography which has and still attract the attention of botanists and biogeographers worldwide. Being one of the richest regions in the Worlds in terms of species endemism and biodiversity, Indonesia has recently gone through intensive transformation of previously rural/natural lands for intensive agriculture (oil palm, rubber, cocoa plantations and rice fields). Climate change represents an additional stress. Projected climate changes in the region include strengthening of monsoon circulation and increase in the frequency and magnitude of extreme rainfall and drought events. The ecological consequences of these scenarios are hard to predict. Within the context of sustainable management of conservation areas and agro-landscapes, Holocene palaeoecological and palynological studies provide a valuable contribution by showing how the natural vegetation present at the location has changed as a consequence of climate variability in the long-term (e.g. the Mid-Holocene moisture maximum, the modern ENSO onset, Little Ice Age etc.). The final aim of my PhD research is to compare the Holocene history of Jambi province and Central Sulawesi. In particular: - Reconstructing past vegetation, plant diversity and climate dynamics in the two study areas Jambi (Sumatra) and Lore Lindu National Park (Sulawesi) - Comparing the ecological responses of lowland monsoon swampy rainforest (Sumatra) and everwet montane rainforests (Sulawesi) to environmental variability (vulnerability/resilience) - Investigating the history of human impact on the landscape (shifting cultivation, slash and burn, crop cultivation, rubber and palm oil plantation) - Assessing the impact and role of droughts (El Niño) and fires - Adding a historical perspective to the evaluation of current and future changes.
Der Beginn der nordhemisphärischen Vereisung und die Entwicklung kontinuierlichen Permafrostes in Eurasien zwischen dem Ende des Miozäns und dem frühen Pleistozän zählt zu den bedeutendsten klimatischen Ereignissen des Känozoikums. Der Zeitpunkt extensiver Vereisung auf den Kontinenten und des Arktischen Ozeans und damit verbundene Veränderungen der klimatischen Bedingungen bleibt bislang ungenau bestimmt.Speläotheme (sekundäre Höhlenkarbonate) stellen ein wichtiges Archiv kontinentaler Umweltbedingungen dar, welches durch besonders genaue radiometrische Altersmodelle für eine grosse Bandbreite an Paläoklimaproxies charakterisiert ist.Wir konnten erfolgreich diagenetisch unveränderte und datierbare Proben aus Zentral- und Nordsibirien identifizieren und schlagen eine Multi-proxy-Studie an U/Pb-datierten Stalagmiten vor. Diese Studie wird Einblicke in die thermalen und hydrologischen Bedingungen zwischen 10.3 Ma und 8 Ma liefern. Wasser aus in den Speläothemen eingeschlossenen Fluidinklusionen wird auf seine Isotopenzusammensetzung hin untersucht. Zudem wird die in den Speläothemen beobachtete Lamination genutzt, um die Saisonalität während des Torton und Messiniums zu rekonstruieren. Wir suchen finanzielle Unterstützung für die parallele Analyse der Isotopie des Fluidinklusionswassers, der Sauerstoff- und Kohlenstoffisotopie des Karbonates, und der Elementkonzentration in den Speläothemen. Diese Kombination geochemischer Methoden wird Einblicke in regionale Umweltbedingungen, die Niederschlagshistorie und Temperaturen während des Miozäns und vor der Entwicklung kontinuierlichen Permafrostes geben. Zusätzliche Proben werden genutzt, um den Wechsel vom eisfreien zu einem durch Permafrost charakterisierten Sibirien zeitlich genauer einzugrenzen.Das vorgeschlagene Projekt wird unser Wissen zur atmosphärischen Zirkulation, und daran geknüpfter Veränderungen des Feuchte- und Temperaturregimes während eines saisonal eisfreien Arktischen Ozeans erweitern.
Über dem Nordatlantik und Europa wird die Variabilität der großräumigen Wetterbedingungen von quasistationären, langandauernden und immer wiederkehrenden Strömungsmustern â€Ì sogenannten Wetterregimen â€Ì geprägt. Diese zeichnen sich durch das Auftreten von Hoch- und Tiefdruckgebieten in bestimmten Regionen aus. Verlässliche Wettervorhersagen auf Zeitskalen von einigen Tagen bis zu einigen Monaten im Voraus hängen von einer korrekten Darstellung der Lebenszyklen dieser Strömungsregime in Computermodellen ab. Um das zu erreichen müssen insbesondere Prozesse, die günstige Bedingungen zur Intensivierung von Tiefdruckgebieten aufrecht erhalten, und Prozesse, die den Aufbau von stationären Hochdruckgebieten (blockierende Hochs) begünstigen, richtig wiedergegeben werden. Aktuelle Forschung deutet stark darauf hin, dass Atmosphäre-Ozean Wechselwirkungen, insbesondere entlang des Golfstroms, latente Wärmefreisetzung in Tiefs, und Kaltluftausbrüche aus der Arktis dabei eine entscheidende Rolle spielen. Dennoch mangelt es an grundlegendem Verständnis wie solche Luftmassentransformationen über dem Ozean die großskalige Höhenströmung beeinflussen. Darüber hinaus ist die Relevanz solcher Prozesse für Lebenszyklen von Wetterregimen unerforscht. In dieser anspruchsvollen drei-jährigen Kollaboration zwischen KIT und ETH Zürich streben wir an ein ganzheitliches Verständnis zu entwickeln, wie Wärmeaustausch zwischen Ozean und Atmosphäre und diabatische Prozesse in der Golfstromregion die Variabilität der großräumigen Strömung über dem Nordatlantik und Europa prägen. Zu diesem Zweck werden wir ausgefeilte Diagnostiken zur Charakterisierung von Luftmassen mit neuartigen Diagnostiken zur Bestimmung des atmosphärischen Energiehaushaltes verbinden und damit den Ablauf von Wetterregimen und Regimewechseln in aktuellen hochaufgelösten numerischen Modelldatensätzen und mit Hilfe von eigenen Sensitivitätsstudien untersuchen. Dazu werden wir unsere Expertise in größräumiger Dynamik und Wettersystemen, sowie Atmosphäre-Ozean Wechselwirkungen â€Ì insbesondere während arktischen Kaltluftausbrüchen â€Ì und der Lagrangeâ€Ìschen Untersuchung atmosphärischer Prozesse nutzen. Im Detail werden wir (i) ein dynamisches Verständnis entwickeln, wie Luftmassentransformationen entlang des Golfstroms die Höhenströmung über Europa beeinflussen, mit Fokus auf blockierenden Hochdruckgebieten, (ii) die Bedeutung von Luftmassentransformationen und diabatischer Prozesse für den Erhalt von Bedingungen, die die Intensivierung von Tiefdruckgebieten während bestimmter Wetterregimelebenszyklen bestimmen, untersuchen, (iii) diese Erkenntnisse in ein einheitliches und quantitatives Bild vereinen, welches die Prozesse, die den Einfluss des Golfstroms auf die großräumige Wettervariabilität prägen, zusammenfasst und (iv) die Güte dieser Prozesse in aktuellen numerischen Vorhersagesystemen bewerten. Diese Grundlagenforschung wird wichtige Erkenntnisse zur Verbesserung von Wettervorhersagemodellen liefern.
This project is part of the large multidisciplinary CCES project RECORD (Assessment and Modeling of Coupled Ecological and Hydrological Dynamics in the Restored Corridor of the River Thur). It deals with the role of microbial transformations and plant uptake in the cycling of nitrogen in different functional processing zones of a restored section of river Thur. The results will help to gain a better understanding of the filter function of restored river corridors and of their potential to emit greenhouse gases. Main hypothesis: Nitrogen fluxes and transformations in floodplains strongly depend on the specific response of microorganisms and dominant plants in different functional processing zones to the hydrologic conditions that vary with season and flooding events. Objectives: At the example of a restored section of river Thur, we want to gain a better insight into the role of riparian systems as sink or source of nitrogen species and the potential risks for drinking water sources and atmosphere. Specific objectives: - quantify the rates of microbial nitrogen transformations within the model floodplain: comparison between different functional processing zones, temporal variations due to seasonal climatic and biological effects and flooding events, dependence on governing soil parameters (temperature, moisture, redox potential). - quantify the rates of nitrogen species uptake by model plants (Phalaris arundinacea, Salix alba): potential uptake depending on nutrient availability and nutrient balance; effects of plant age and and temporary flooding. - measure and model nitrogen species concentrations in the soil solution and nitrous oxide emissions: comparison between different functional processing zones, temporal variations due to seasonal climatic and biological effects and flooding events. Methods: - Sampling and monitoring plots with a diameter of 8m have been set-up in different functional processing zones: (i) pasture in a neighboring non-restored section, (ii) river-forest transect including weakly colonized gravel, gravel covered by fine over-bank material densely overgrown with reed grass (Phalaris arundinacea) and other herbaceous species, zone planted with willow (Salix alba) during the restoration, mixed deciduous forest dominated by ash, (iii) old riparian willow forest. - Microbial nitrogen transformation rates are determined from soil samples taken from within the plots at specific times. Mineralisation immobilisation turnover (MIT) is determined by isotopic dilution, potential denitrification by acetylen-inhibition incubation. - Specific nitrate and ammonium uptake rates by model plants are determined in hydroponic treatments in the climate chamber. - Soil respiration and trace gas efflux/influx is measured by in-situ gas sampling from within large rings permanently installed on the plots followed by GC analysis. Etc.
We intend to investigate the molecular mechanisms of mineral nutrient dependent poplar physiology with special focus on potassium. This will be accomplished using two different approaches. 1. Molecular biology: We will study the regulation of ion channels and transporters by different environmental conditions, such as the effect of nutrition, salt, hormonal action, cold and drought during wood production and the dormancy-growth transitions. Phenotype analysis of transporter sense/antisense plants will be used to gain insights into the role of the transporters in tree physiology. On the basis of a laser-micro-dissection system, we will be able to prepare cDNA of distinct cell types and generate subtractive cDNAs to determine genes, specific for the differentiation of vessels and bast fibers. 2. Electrophysiological investigations: We will compare the functional properties of the transporters. Ion-fluxes and transporters, involved in cambial activation will be characterized in vivo and in vitro. The response to changes in e.g. the extracellular medium in vitro, will provide a measure for the regulation of ion transport by apoplastic factors in vivo. Based on this data sets we should be able to establish a model on the seasonal fluxes of potassium in relation to the transporter properties and dynamics in the context of tree physiology in general and xylogenesis in particular.
The project 'Transfer over Ecosystems of Reduced Nitrogen by Mass Spectrometry' (TERMS) proposes to adopt Proton Transfer Reaction Mass Spectrometry (PTR-MS) to measure ambient concentrations of ammonia and selected volatile organic nitrogenous compounds. The project also aims at measuring turbulent ammonia fluxes using eddy covariance approaches by taking advantage of the fast time resolution of PTR-MS. The project consists of the following three parts: a) Instrument development: The PTR-MS instrument will be operated in a new mode, using O2+ as the reagent ion instead of H3O+. Because NH3 is a very sticky molecule, memory effects in the inlet system -- including the sampling line and the transfer into the drift tube of the instrument -- limit the time resolution and present major challenges to the application in an eddy covariance approach. A series of optimizations will be performed to lower memory effects to a degree that the losses can be corrected for. b) Concentration measurements of ammonia and other volatile organic nitrogen species: Measurements will be carried out at the NitroEurope grassland site Oensingen in Switzerland. The focus of the ammonia measurements is the characterization of the temporal dynamics of ambient concentrations at diurnal to seasonal time scales, with a special focus on the morning breakup of the nocturnal boundary layer. In addition the concentrations of selected volatile organic nitrogen compounds will be measured in order to assess their relevance for atmospheric chemistry processes. c) Ammonia exchange flux measurements at NitroEurope sites: The modified and improved PTR-MS system will be applied to measure ammonia exchange fluxes with an eddy covariance approach over several months. We focus on temperate grasslands systems that dominate agricultural production in Switzerland, covering about 69Prozent of the agricultural land. On the European scale this fraction amounts to 49Prozent, representing 30Prozent of the total land area. Grasslands are alternately important sinks and sources for reduced nitrogen, and thus influence the fraction of total emitted reduced nitrogen that is deposited downwind onto semi-natural and natural areas. The quantification of exchange fluxes is crucial for the evaluation of the ecological problems related to the N-cycle. The core of the project is a dissertation focusing on the characterization of the concentrations and fluxes of reduced nitrogen compounds over grassland systems. The PhD candidate can build on the large experience of our group both in field measurements and in the application of eddy covariance techniques for flux measurements of reactive trace gases.
The Okavango is a large African wetland of prime ecological importance. Its existence is in jeopardy due to upstream development and increasing water demand in combination with predicted climatic change. Less water means a reduction of the permanent and seasonal swamp areas. The project creates a computer model serving as a tool to predict the impact of upstream hydraulic measures, channel management and changes in climate on the availability of water in the delta and its spatial distribution. It also looks at the sediment transport. The availability of water e.g. expressed by the frequency of flooding at a location is essential for the type of habitat prevailing at that point. Changes of water availability will therefore also cause changes in the habitat composition of the delta. Management of channels by cutting of papyrus or dredging will change the distribution of flooded areas. The interaction of the channels of the Okavango Delta with the floodplains and the underlying groundwater is of crucial importance. Vegetation on the islands gets its water through infiltration from the river channels and the yearly flood propagates both in the channels and in the groundwater. Therefore the model couples the surface water flow - in channels and overland during flooding - with the groundwater flow. In a region with little infrastructure it is hard to find data for this modelling effort. However, nowadays many data can be found through remote sensing techniques both from satellite and airborne platforms. These include the topography (from the Shuttle Mission), the rainfall (from METOESAT 5), the evapotranspiration (from NOAA-AVHRR) and the extension of water surfaces in their temporal development (from radar satellites and others). The thickness of the groundwater body is evaluated from aeromagnetic records provided by the geological Survey of Botswana. The infiltration zones can be seen through another airborne geophysical technique, the TEM-method. This survey is financed by the Botswanan government and will take place in April 2007. All satellite and airborne information needs calibration and interpretation through ground truth which is obtained in yearly field campaigns. The water areas serve as data for the adjustment and verification of the model. The insight gained through the model will flow into the work of the Okavango River Commission (OKACOM) which has to negotiate the permissible water use in the upstream.
| Organisation | Count |
|---|---|
| Bund | 56 |
| Europa | 6 |
| Land | 2 |
| Wissenschaft | 30 |
| Type | Count |
|---|---|
| Förderprogramm | 55 |
| unbekannt | 1 |
| License | Count |
|---|---|
| Offen | 55 |
| Unbekannt | 1 |
| Language | Count |
|---|---|
| Deutsch | 6 |
| Englisch | 55 |
| Resource type | Count |
|---|---|
| Keine | 45 |
| Webseite | 11 |
| Topic | Count |
|---|---|
| Boden | 51 |
| Lebewesen und Lebensräume | 53 |
| Luft | 46 |
| Mensch und Umwelt | 55 |
| Wasser | 47 |
| Weitere | 56 |