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In Belize, which is well known for the Belize Barrier Reef and its offshore atolls, coastal lagoons are frequent morphological features along the coast. They represent transitional environments between siliciclastic and carbonate settings. In order to shed light into the Holocene evolution of coastal lagoon environments, five localities along the central coast of Belize were selected as coring sites. These include four coastal lagoons and one marsh area, namely Mantatee Lagoon, Mullins River Beach, Colson Point Lagoon, Commerce Bight Lagoon and Sapodilla Lagoon. A total of 26 sediment cores with core lengths ranging from 109 cm to 500 cm, were drilled using a Lanesky-vibracorer. Overall, 73 m of Holocene sediments and Pleistocene soil were recovered. Together with 58 radiocarbon dates the sediments reveal details on the sediment architecture and depositional features of the localities.
Marine inundation of the mainland and coastal lagoon formation started around 6 kyrs cal BP.
As a response to sea-level rise during the Holocene transgression, facies retrograded towards the coast, as seen in marginal marine overlying brackish mollusk faunas. Evidence for late Holocene progradation of facies due to sea-level stagnation is largely lacking. The occurrence of landward thinning sand beds, hiatuses and marine fauna in lagoonal successions are indications of event (overwash) sedimentation. Sediments recovered are largely of Holocene age (<7980 cal BP), overlying Pleistocene sections. Analyses of sediment composition and texture, radiocarbon dating and mollusk shell identification were used to describe and correlate sedimentary facies.
XRD analyses have identified quartz as the dominant mineral, with the Maya Mountains as main source of coastal lagoon sediments. The most common sedimentary facies include peat and peaty sediment, mud, sand, and poorly sorted sediments. Pleistocene soil forms the basement of Holocene sediments. Holocene mud represents lagoon background permanent sedimentation.
Peats and peat-rich sequences were deposited in mangrove swamp environments, whereas sandy facies mainly occur in the shoreface, beach, barriers, bars, barrier spits and overwash deposits. Facies successions could be identified for each locality, but it has proven difficult to correlate the stratigraphic sequences, especially among localities. These differences among the five locations studied suggest that apart from regional influence such as sea-level rise, local environmental factors such as small-scale variation in geomorphology and resulting facies heterogeneity, connectivity of the lagoon with the sea, antecedent topography and river discharge, were responsible for coastal sedimentation and lagoon development in the Holocene of Belize.
Faunal composition and distribution patterns of mollusk assemblages from 20 shell concentrations in cores collected in coastal lagoons, a mangrove-fringed tidal inlet and the marginal marine area (shallow subtidal) show considerable variation due to environmental heterogeneity and the interplay of several environmental factors in the course of the mid-late Holocene (ca. 6000 cal BP to modern). The investigated fauna ≥2 mm comprises 2246 bivalve, gastropod and 11 scaphopod specimens. Fifty-three mollusk species, belonging to 42 families, were identified. The bivalve Anomalocardia cuneimeris and cerithid gastropods are the dominant species and account for 78% of the total fauna. Diversity indices are low in concentrations from lagoons and relatively high in the marginal marine and tidal inlet areas.
Based on cluster analysis and nonmetric multidimensional scaling (NMDS), seven lagoonal assemblages and three marginal marine/tidal inlet assemblages were defined. A separation between lagoonal and marginal marine/tidal inlet assemblages seen in ordination indicates a lagoon-onshore gradient. The statistical separation among lagoonal assemblages demonstrates environmental changes during the Holocene evolution of the coastal lagoons, which is probably related to the formation of barriers and spits. The controlling factors of species distribution patterns are difficult to figure out, probably due to the heterogeneity of the barrier-lagoon systems and the interaction of paleoecological and paleoenvironmental factors. In addition to the taxonomic analysis, a taphonomic analysis of 1827 valves of A. cuneimeris from coastal lagoons was carried out. There is no relationship between depth and age of shells and their taphonomic condition. Size-frequency distributions and right-left valve ratios of A. cuneimeris suggest that valves were not transported over long distances but were deposited parautochthonously in their original habitat. Shells from tidal inlet and marginal marine environments were also predominantly deposited in their original habitats.
Since the Belize coast was repeatedly affected by hurricanes and the paleohurricane record for this region is poor, the sediment cores have been examined in order to identify storm deposits.
The paleohurricane record presented in this study spans the past 8000 years and exhibits three periods with increased evidences of hurricane strikes occurring at 6000-4900 cal yr BP, 4200-3600 cal yr BP and 2200-1500 cal yr BP. Two earlier events around 7100 and 7900 cal yr BP and more recent events around 180 cal yr BP and during modern times have been detected. Sand layers, redeposited corals and lagoon shell concentrations have been used as proxies for storm deposition. Additionally, hiatuses and reversed ages may indicate storm influence. While sand layers and corals represent overwash deposits, the lagoon shell concentrations, which mainly comprise the bivalve Anomalocardia cuneimeris and cerithid gastropods, have been deposited due to changes in lagoon salinity during and after storm landfalls. Comparison with other studies reveals similarities with one record from Belize, but hardly any matches with other published records. The potential for paleotempestology reconstructions of the barrier-lagoon complexes along the central Belize coast differs depending on geomorphology, and deposition of washovers in the lagoon basins is limited, probably due to the interplay of biological, geological and geomorphological processes.
Die Revolutionen des Meeres
(1843)
Floodplains play an important role in the terrestrial water cycle and are very important for biodiversity. Therefore, an improved representation of the dynamics of floodplain water flows and storage in global hydrological and land surface models is required. To support model validation, we combined monthly time series of satellite-derived inundation areas (Papa et al., 2010) with data on irrigated rice areas (Portmann et al., 2010). In this way, we obtained global-scale time series of naturally inundated areas (NIA), with monthly values of inundation extent during 1993–2004 and a spatial resolution of 0.5°. For most grid cells (0.5°×0.5°), the mean annual maximum of NIA agrees well with the static open water extent of the Global Lakes and Wetlands database (GLWD) (Lehner and Döll, 2004), but in 16% of the cells NIA is larger than GLWD. In some regions, like Northwestern Europe, NIA clearly overestimates inundated areas, probably because of confounding very wet soils with inundated areas. In other areas, such as South Asia, it is likely that NIA can help to enhance GLWD. NIA data will be very useful for developing and validating a floodplain modeling algorithm for the global hydrological model WGHM. For example, we found that monthly NIAs correlate with observed river discharges.
Floodplains and other wetlands depend on seasonal river flooding and play an important role in the terrestrial water cycle. They influence evapotranspiration, water storage and river discharge dynamics, and they are the habitat of a large number of animals and plants. Thus, to assess the Earth’s system and its changes, a robust understanding of the dynamics of floodplain wetlands including inundated areas, water storages, and water flows is required.
This PhD thesis aims at improving the modeling of large floodplains and wetlands within the global-scale hydrological model WaterGAP, in order to better estimate water flows and water storage variations in different storage compartments. Within the scope of this thesis, I have developed a new approach to simulate dynamic floodplain inundation on a global-scale. This approach introduces an algorithm into WaterGAP, which has a spatial resolution of 0.5 degree (longitude and latitude) globally. The new approach uses subgrid-scale topography, based on high-resolution digital elevation models, to describe the floodplain elevation profile within each grid cell by applying a hypsographic curve. The approach comprises the modeling of a two-way river-floodplain interaction, the separate downstream water transport within the river and the floodplain – both with temporally and spatially different variable flow velocities – and the floodplain-groundwater interactions. The WaterGAP version that includes the floodplain algorithm, WaterGAP 2.2b_fpl, estimates floodplain and river water storage, inundated area and water table elevation, and also simulates backwater effects.
WaterGAP 2.2b_fpl was applied to model river discharge, river flow velocity, water storages, water heights and surface water extent on a global-scale. Model results were comprehensively validated against ground observations and remote sensing data. Overall, the modeled and observed data are in agreement. In comparison to the former version WaterGAP 2.2b, the model performance has improved significantly. The improvements are most remarkable in the Amazon River basin. However, the seasonal variation of surface water extent and total water storage anomalies are still too low in many regions on the globe when compared to observations. A detailed analysis of the simulated results suggests that in the Amazon River basin the introduction of backwater effects is important for realistically simulating water storages and surface water extent. Future efforts should focus on the simulation of water levels in order to better model the flow routing according to water slope. To further improve the model performance in specific regions, I recommend that the globally constant model parameters that affect inundation initiation, river-floodplain interaction, DEM correction for vegetation, and backwater amount at basin or subbasin-scale be adjusted.
WaterGAP (Water - Global Assessment and Prognosis) is a tool for modeling global water use and water availability. It participates among other models in the ISIMIP initiative (The Inter-Sectoral Impact Model Intercomparison Project). As part of this initiative, the water temperature should be calculated by participating hydrological models because it plays a vital role in many chemical, physical and biological processes. Therefore, the subject of this master thesis is to implement the physically based surface water temperature computation after VAN BEEK ET AL. (2012) and WANDERS ET AL. (2019) into WaterGAP and compare the results to the statistical regression approach by PUNZET ET AL. (2012). The computation is validated with observed water temperature data obtained from the GEMStat water quality database. The results are good for arctic and temperate latitudes. Surface water temperatures for tropical rivers are overestimated, most likely due to the overestimation of precipitation temperatures, incoming radiation and groundwater temperatures. The comparison with the regression model by PUNZET ET AL. (2012) shows matching results. The regression model even matches with WaterGAP results for most of the simulations of the future under climate change conditions, where the regression model should stop working due to changing environmental parameters. Several assumptions had to be made in order to implement the water temperature calculation in Water-GAP. These include, e.g., discharge temperatures for power plant cooling water, precipitation and surface runoff temperatures. For model improvements, perhaps three different values for the different regions of the world should be used to cool down the precipitation and surface runoff. The model could also be improved by refining the ice formation calculation, especially for the conditions when the ice melts, breaks up and is transported downstream. Furthermore, the feedback to the river channel roughness could be implemented if ice has formed. The WaterGAP model upgraded with the water temperature calculation will help the ISIMIP initiative in the future.
Polarization of Λ and ¯Λ hyperons along the beam direction in Pb-Pb collisions at √sNN=5.02 TeV
(2022)
The polarization of the Λ and ¯Λ hyperons along the beam (z) direction, Pz, has been measured in Pb-Pb collisions at √sNN=5.02 TeV recorded with ALICE at the Large Hadron Collider (LHC). The main contribution to Pz comes from elliptic flow-induced vorticity and can be characterized by the second Fourier sine coefficient Pz,s2=⟨Pzsin(2φ−2Ψ2)⟩, where φ is thhyperon azimuthal emission angle and Ψ2 is the elliptic flow plane angle. We report the measurement of Pz,s2 for different collision centralities and in the 30%–50% centrality interval as a function of the hyperon transverse momentum and rapidity. The Pz,s2 is positive similarly as measured by the STAR Collaboration in Au-Au collisions at √sNN=200 GeV, with somewhat smaller amplitude in the semicentral collisions. This is the first experimental evidence of a nonzero hyperon Pz in Pb-Pb collisions at the LHC. The comparison of the measured Pz,s2 with the hydrodynamic model calculations shows sensitivity to the competing contributions from thermal and the recently found shear-induced vorticity, as well as to whether the polarization is acquired at the quark-gluon plasma or the hadronic phase.
IFLS-Journal. Nr. 3, 2003
(2003)
Nach dem aktuellen Stand der Klimaforschung, der vor allem im jüngsten Bericht des ‘Intergovernmental Panel on Climate Change’ (IPCC) zusammengefaßt ist, liegt es nahe, von einem menschlichen Einfluß auf das globale Klima zu sprechen.Wenn es nicht gelingt, die bestehenden Wirtschafts- und Lebensweisen zu ändern, droht mit großer Wahrscheinlichkeit eine globale Klimaänderung in einem Ausmaß und in einer Geschwindigkeit, wie sie in den letzten 10.000 Jahren (im jüngeren Quartär) niemals aufgetreten ist. Um die deshalb zum Schutz des Klimasystems notwendigen Emissionsreduktionen zu bestimmen, wendet der Beirat das bereits 1995 in der Stellungnahme zur ersten Vertragsstaatenkonferenz genutzte Konzept der „Toleranzfenster“ erneut an. Dabei wird der für die kommenden 200 Jahre noch verbleibende Handlungsspielraum durch die normative Vorgabe von auf keinen Fall hinnehmbaren ökologischen, ökonomischen und sozialen „Leitplanken“ der Klimaentwicklung und der Klimapolitik ermittelt. Die Summe der Leitplanken definiert das „Toleranzfenster“ im Klimaschutz. Der Beirat geht davon aus, daß entsprechend dem „Berliner Mandat“ von 1995 und den in der Klimarahmenkonvention niedergelegten völkerrechtlichen Grundsätzen zunächst nur die in Anlage I aufgeführten Staaten (Industrieländer) durch konkrete Reduktionsziele in die Pflicht genommen werden. Für die Verteilung von Pflichten zwischen den einzelnen Ländern empfiehlt der Beirat den sogenannten „Pro-Kopf-Ansatz“ als grundsätzliches Kriterium, wobei in einer Übergangsphase andere Ansätze vorübergehend zum Einsatz kommen können. Daraus ergibt sich notwendigerweise ein stark verengter Handlungsspielraum für die Industrieländer. Der Beirat kommt zu dem Ergebnis, daß sein 1995 in der Stellungnahme zur ersten Vertragsstaatenkonferenz vorgeschlagenes Emissionsprofil („WBGUSzenario“) nur dann als mit den ökologischen, ökonomischen, sozialen und völkerrechtlichen Leitplanken verträglich ist, wenn es sich nicht nur auf Kohlendioxid bezieht, sondern auch die anderen wichtigen Treibhausgase wie Methan und Distickstoffoxid berücksichtigt.
Der vorliegende Hand-Atlas von Afrika ist in besonderer Beziehung auf das Werk über allgemeine vergleichende Geographie von C. Ritter herausgegeben. Die darin enthaltenen Karten und Pläne sollen zunächst als Beilagen für dies Werk betrachtet werden, bilden aber dem unerachtet auch ein für sich Bestehendes. Außer den eigentlichen Karten sind noch einige Ansichts - und Durchschnittszeichnungen zur besseren Versinnlichung besonders merkwürdiger Ländertheile hinzugefügt. Die 14 Blatt des Atlasses enthalten die Darstellung folgender geographischer Gegenstände : 1. Karte von Afrika, als Übersicht der Speciablätter. Auf dieser sind die Reisen von Clapperton im Norden und die der Portugiesen im Süden, welche seit der Erscheinung der 2ten Auflage des Theiles I. der Allgemeinen Erdkunde von C. Ritter bekannt wurden, bloß durch farbige Linien angedeutet: ihre nähere Erklärung soll später erfolgen, und zwar in den künftig erscheinenden Beiträgen und Nachträgen zur Erdkunde von Afrika (s. C. Ritter´s Erdkunde 2te Aufl. Th. I. Vorwort S. XIII. ). 2. Karte vom Südende Afrikas, vom Kap der guten Hoffnung landeinwärts, bis zum äußersten Ziele europäischer Reisenden, unter 25´ Südbreite, zu Seite 91. bis 136. der allgemeinen Erdkunde Th. I. 2te Aufl. Auf dieser Karte ist die spätere naturhistorische Reise Burchell´s um Litalcu, ohne nähere Bezeichnung, bloß durch einen hellgrünen Strich angedeutet, und wird von dieser Reise, ebenfalls in den oben erwähnten Nachträgen, Bericht erstattet werden. Beigegeben ist ein Pla n der Halbinsel des Vorgebirges, nach einer vortrefflichen Handzeichnug, deren gütige Mittheilung wir dem Herrn Professor Lichtenstein verdanken. 3. Äthiopisches Hochland, Alpenland Habesch und Vorstufe von Darfur und Sennaar; zu Seite 167. bis 255., und zu Seite 517. bis 571. des erwähnten Buches. Dies Blatt reichet im Norden bis zur Nilkatarakte von Dulga, wo das Blatt No. 5., das lste des Nillaufes, beginnt. 4. Karte von Hochsudan, welche Nordguinea, nebst den Senegal-Ländern, bis zur Sahara begreift, so wie auch den obern Lauf des Niger bis gegen Tombuktu. Zu Seite 330. bis 387. und Seite 401. bis 428. 5. Lauf des Nils von der Katarakte von Dulga bis Vady Halfa zu S. 594. bis 620. 6. Lauf des Nils von Wady Halfa bis Kous, zu S. 620. bis 757. Beigegeben ist eine landschaftliche Zeichnung und ein Grundriß des Felsentempels zu Ebsambol. 7. Lauf des Nils von Kous bis Kairo, zu Seite 757. bis 882. 8. Die Nilkatarakten von Syene zu Seite 680. und folgende. Beigegeben ist, in dreimal größerem Maßstabe, der Plan derjenigen Stelle des Hauptplans,; welche mit Chellal oder Kataracte bezeichnet ist, und zwar so, wie sie bei hohem Wasser sich darstellt, wo die, im Hauptplane hervorragenden Sandbänke und niedrigen Klippen vom Wasser bedeckt sind. 9. Plan der Gegend von Theben, zu Seite731.und folgende. 10. Karte von Unter-Ägypten, zu Seite 814. 11. und 12. Plan von Kairo und Umgegend, bis zu den Ruinen des alten Memphis, nebst der Lage der grorsen Pyramiden von Gizeh und der Pyramidengruppen von Sakkarah; zu Seite 814. usw. Beigegeben ein Querdurchschnitt des Nilthals bei Kairo. Die nähere Beschreibung in den Nachträgen zur Erdkunde von Afrika. 13. a) Plan von Alexandria, zu S. 863. b) Querdurchschnitt des Nilthales bei Stout, zu Seite 772. und folgende c) Kurve, welche das Steigen und Fallen des Wassers bei den Nilschwellen darstellt, zu S. 837. d) Nilmesser und Denkmale, an welchen die Erhühungen des Nilbettes beobachtet sind, zu Seite 840. usw. 14. Karte der Nordküste Afrikas, von Alexandria bis Tunis; also das Land der Cyrenais und des alten Karthago mit inbegriffen, zu Seite 912. bis 1015. Dabei der Entwurf eines berichtigten Planes der alten punischen und der romischen Koloniestadt Karthago, zu Seite 914. bis 921.