Paleolimnological assessment of human impacts in Lake Blanca, SE Uruguay

Paleolimnological techniques were used to assess human impacts onLake Blanca, a small (0.6 km²), coastal fresh waterbodyin southern Uruguay, which is the drinking water source for 100,000 localresidents. We retrieved a core that extends to about 1100 ¹⁴Cyr BP. ²¹⁰Pb ages, organic mater, CO₃, totalcarbon, nutrients, fossil pigments and diatoms allowed us to establishlimnological conditions before and after cultural impacts. Soil removal(1880–1960) and intensive cattle and sheep grazing (1943–1966) ledto gully formation in the catchment. This watershed erosion resulted inincreased sedimentation rates. The aquatic system appeared to be mesotrophicwith dominance of epibenthic diatoms until 1966, at which timeeutrophication intensified with forestry activities. Increases in nutrients, aswell as blooms of planktonic diatoms, were observed. During the last decade,tourist/urban development as well as high drinking water demand caused areduction in lake area. Subsequent marked increases in rainfall led to furtherphytoplankton blooms and macrophyte proliferation.     

Contained turbidites used to track sea bed deformation and basin migration, Sorbas Basin, south-east Spain

ABSTRACT The mechanisms driving subsidence in late orogenic basins are often not easily resolved on account of later fault reactivation and a rapidly changing stress field. Contained turbidites in such basins provide a unique opportunity of monitoring sea bed deformation and evolving bathymetry and hence patterns of subsidence during basin filling. A variety of interpretations have been proposed to explain subsidence in Neogene basins in SE Spain, including extensional, strike‐slip and thrust top mechanisms. Ponded turbidite sheets on the floor of the Neogene Sorbas Basin (SE Spain) were deposited by sand‐bearing currents which ran into enclosed bathymetric deeps where they underwent rapid suspension collapse. The structure and distribution of these sheets (and the thick mudstone caps which overlie them) act as a proxy for the containing sea bed bathymetry at the time of deposition. An analysis of the sheet architecture helps identify a trough‐axial zone of syndepositional faulting and reveals a westwards stepping of the ponding depocentre with time. Fault breaks at the sea bed influenced the position of flow arrest and the distribution of sandstone beds on the basin floor. Westward stepping of the deeper bathymetry was episodic and probably controlled by transverse faults. Re‐locations of the depocentre were accompanied by the destabilization of carbonate sand stores on the margins of the basin, resulting in the repeated emplacement of large‐volume carbonate megabeds and calciturbidites. The fill to the Sorbas Basin was shingled by the onset of compression in the east attributed to transfer of slip between intersecting strike‐slip fault strands. A sinistral fault (a splay of the Carboneras Fault System) propagated through the evolving basin fill from the east as the eastern part of the basin became inverted and the locus of subsidence migrated into the Tabernas area 20 km area to the west. The sedimentological analysis of the basin fill helps see through a late dextral overprint which ultimately juxtaposed basement rocks to the south against the inverted and upended basin, along a late slip‐modified unconformity. Conventional palaeostress analysis of fractures along the basin margin fails to see past this late dextral shearing event. Basin migration parallel to the E–W‐orientated basin axis, slip‐reversal (sinistral to dextral) and the active involvement of strike‐slip faults are now identified as important aspects of the evolution of the Sorbas Basin during the latestTortonian.     

Beiträge zu einer elektrischen Tornadotheorie

Zusammenfassung Ein VorschlagB. Vonneguts, elektrische Tornadotheorien wieder in Betracht zu ziehen, wird aufgegriffen und es wird gezeigt, daß die Gewittertheorie mit der elektromagnetischen Induktion als Grundlage auch auf das Tornadoproblem anwendbar ist. Dadurch finden nicht nur mehrere Eigenschaften des Tornados eine zwanglose Erklärung, vielmehr wird darüber hinaus auch die Wahrscheinlichkeit der Brauchbarkeit der Gewittertheorie bedeutend erhöht. Das beste Argument für die Wirksamkeit der elektromagnetischen Induktion dürfte in der Beobachtung einer rhombusförmigen, mehrere Tornados erzeugenden Gewitterwolke zu sehen sein, die durch das Raumgitter einer Dipolwolke befriedigend erklärt werden kann.Summary Following a suggestion byB. Vonnegut to reconsider electrical torando theories, the author shows that the thunderstorm theory based on electromagnetic induction is also applicable to the tornado problem. Several characteristics of the tornado are easily explained, adding evidence of the validity of the thunderstorm theory. The strongest argument in favour of the effectiveness of electromagnetic induction may be considered the observation of a rhomb-shaped thunderstorm cloud which generated several tornadoes. Such a cloud can be explained by the spacial distribution of its dipole elements.

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Résumé L'auteur se réfère à la proposition deB. Vonnegut de reconsidérer la théorie électrique des tornades. Il démontre que la théorie des orages, basée sur l'induction électro-magnétique, est également applicable au problème des tornades. Non seulement on explique aisément par ce moyen plusieurs propriétés des tornades, mais encore la probabilité de la valeur d'application de la théorie des orages en est sensiblement renforcée. Le meilleur argument en faveur de l'activité de l'induction électro-magnétique est certes l'observation d'un nuage d'orage en losange qui engendra plusieurs tornades. Cette formation peut s'expliquer de façon satisfaisante par la grille spaciale d'un nuage en dipole.

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Mit 6 Textabbildungen

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Dem Gedenken an Priv.-Doz. Dr.Fritz Rossmann gewidmet.     

Electric sector investments under technological and policy-related uncertainties: a stochastic programming approach

Although emerging technologies like carbon capture and storage and advanced nuclear are expected to play leading roles in greenhouse gas mitigation efforts, many engineering and policy-related uncertainties will influence their deployment. Capital-intensive infrastructure decisions depend on understanding the likelihoods and impacts of uncertainties such as the timing and stringency of climate policy as well as the technological availability of carbon capture systems. This paper demonstrates the utility of stochastic programming approaches to uncertainty analysis within a practical policy setting, using uncertainties in the US electric sector as motivating examples. We describe the potential utility of this framework for energy-environmental decision making and use a modeling example to reinforce these points and to stress the need for new tools to better exploit the full range of benefits the stochastic programming approach can provide. Model results illustrate how this framework can give important insights about hedging strategies to reduce risks associated with high compliance costs for tight CO₂ caps and low CCS availability. Metrics for evaluating uncertainties like the expected value of perfect information and the value of the stochastic solution quantify the importance of including uncertainties in capacity planning, of making precautionary low-carbon investments, and of conducting research and gathering information to reduce risk.     

On calculation of wind speed in tornado

A formula is obtained for calculation of wind speed in tornado, as proportional to the speed of convective updraft. Results are presented of wind speed calculation using the formula for 57 tornadoes observed at different time and in different regions of the world. Possibilities are shown of tornado wind speed forecasting taking into account criteria of tornado danger of the Cb clouds.     

The influence of air-sea interaction on the development and motion of a tropical cyclone: Numerical experiments with a triply nested model

Summary Tropical cyclone (TC)—ocena feedbacks are studied using a coupled tropical cyclone-ocean model consisting of an eightlayer triply-nested movable grid model of a TC and a three-layer primitive equation ocean model. The numerical results indicate that the TC-ocean interaction influences intensities, structures, and the trajectories of tropical cyclones. Two possible mechanisms, barotropic and baroclinic, influencing TC tracks under TC-ocean interaction are suggested. The barotropic mechanism is related to the changes of the vertically averaged TC structure, induced by the TC-ocean coupling. The baroclinic mechanism is related to the asymmetry of the condensation heating within the TC caused by the asymmetry of heat and moisture fluxes at the sea surface. This asymmetry arises due to the asymmetry in sea surface cooling relative to the storm center. The experiments indicate that the influence of TC-ocean interaction on the TC tracks is the greatest for the case of a zero background flow. In the case of a non-zero background flow the sensitivity of storm tracks to the coupling with the ocean decreases. It is found that the influence of the ocean coupling on the TC track is quite sensitive to the method of convective heating parameterization in the TC model. The TC-ocean interaction also results in a change of the amount and spatial distribution of precipitation.     

Simulating the 1999 Capbreton canyon turbidity current with a Cellular Automata model

A numerical model has been developed for the simulation of turbidity currents driven by nonuniform, non cohesive sediment and flowing over a complex three dimensional submarine topography. The model is based on an alternative approach known as Cellular Automata paradigm. The model is validated by comparing a simulation with a reported field-scale event. The chosen case is a turbidity current which occurred in Capbreton Canyon and was initiated by a storm in December 1999. Using data from recent oceanographic cruises, the deposit of the event has been precisely described, which constrain values of model parameters. The model simulates the 1999 turbidity current over the actual canyon topography and related turbidite using three different types of particle. The model successfully simulates areas of erosion and deposition in the canyon. It predicts the vertical and longitudinal grain size evolution, and shows that the fining-up sequence can be deposited by several phases of deposition and erosion related to the current energetic variation during its evolution. This result could explain the presence of intrabed contacts or the frequent lack of facies in Bouma sequences.