ALBERT

Description: In the eastern Karawanken Mountains, the siliciclastic sedimentary succession of the Hochwipfel Formation was deposited within a narrow marginal basin of the western Paleotethys. Variations of detrital sandstone modes define four petrofacies types, and allow the succession to be stratigraphically divided into Lower and Upper Hochwipfel Formation. Petrographical and geochemical provenance analysis indicate that the basal quartz-rich sandstones derived mainly from the Intraalpine Terrane in the north and the passive Gondwana margin in the south. In the sediments of the Upper Hochwipfel Formation, an increase of (meta)sedimentary as well as of magmatic lithoclasts is discernible indicating a convergent tectonic situation and increased sediment supply derived from a magmatic arc. Zusammenfassung: Die klastische Sedimentabfolge der karhonen HochwipfelFormation der Ostkarawanken wurde in einem schmalen Randbecken der westlichen Paläotethys abgelagert. Auf Grund der Modalzusammensetzung der Sandsteine lassen sich vier Petrofaziestypen unterscheiden, und die sedimentäre Abfolge in eine Untere und eine Obere Hochwipfel-Formation gliedern. Petrographische und geochemische Provenienz-Indikatoren deuten darauf hin, dass die basalen quarzreichen Sandsteine der unteren Hochwipfel-Formation überwiegend von dem nördlich gelegenen Intraalpinen Terran bzw. dem südlich gelegenen passiven Kontinentalrand Gondwanas stammen. In den Sedimenten der oberen Hochwipfel-Formation ist eine Zunahme von (meta)sedimentären Lithoklasten sowie magmatischen Gesteinsbruchstücken zu beobachten. Dies zeigt den Übergang zu einer konvergenten tektonischen Situation und den verstärkten Sedimenteintrag aus einem magmatischen Bogen an.

Description: In late 1999, seismic and seismological investigations were carried out on the Continental margin of Costa Rica. Besides conventional wide angle refraction profiles, airgun shots were fired on a sub circular profile around Osa Peninsula into Golfo Dulce and were recorded by 20 ocean bottom hydrophones deployed along the crest of Cocos Ridge and by 13 Seismometers across the ridge. The resulting uneven distribution of shots and receivers does not allow for a full 3Dtomographic inversion. However, for selected parts detailed velocity information can be obtained providing constraints on the structure of the subsurface. Preliminary results indicate that Cocos Ridge has a bowl-shaped crustal root with a thickness of nearly 20 km in its center and only small changes along strike within the first 50 km seaward of the Middle America trench.

Description: In this article we review the indirect interactions prevailing in littoral communities and compare their importance to direct trophic interactions. We focus on the interaction between benthic algae and their herbivorous consumers, i. e. invertebrate grazers and herbivorous fish. In addition to the effects of grazers on periphyton biomass and production, we categorise and describe the types of indirect interactions observed and we present a quantitative meta-analysis to compare the effect magnitude of indirect and direct effects. Our review shows that herbivore-plant interactions comprise considerable complexity beyond consumption. We identify and review three different indirect interactions, which play important roles for periphyton-grazer interactions in benthic food webs. These are keystone predation, trophic cascading and habitat facilitation. Direct negative effects were stronger than indirect positive effect, because grazing leads in almost all studies to a decrease in algal biomass. We found positive effects of grazing on algal nutrient content, biomass-specific productivity and evenness. We found negative overall effects on species richness and area-specific productivity. Moreover, spatial heterogeneity was on average increased by grazing. The magnitudes of direct and indirect effects were often correlated

Description: The understanding of the tectonic processes shaping the Pacific margin off Costa Rica has undergone a dramatic evolution during the past 25 years. The margin, initially interpreted to be built by accretion of sediment from the ocean plate, is now interpreted as made of ophiolitic rocks that are exposed onshore, with no net accretion currently active. New seismic images indicate that upper plate tectonic erosion might be the dominant process. Erosion is accomplished in some cases through transport of large bodies from upper to lower plate by plate boundary readjustment. Subduction of seamounts locally accelerates tectonic erosion.

Description: In order to investigate the energy and water balance of the Baltic Sea and its catchment area, the commonly used regional models have to be validated against observation data. One of the most important parameters of the hydrological cycle is the vertically integrated atmospheric water vapour content. Satellite observations from SSM/I (Special Sensor Microwave/Imager) can help to provide data over the sea. The accuracy of these results are tested with observations of radiosondes, which are launched from RV Alkor cruising in the Baltic Sea. The bias of both data sets is negligibly small. However, due to the low spatial resolution, problems occur in coastal regions, arising problems in particular in the small-scaled Baltic Sea. Thus, a correcting scheme for disturbing land influences is presented. This satellite-derived data set is compared with REMO-DWD results (REgional Model using physical package of DWD) for the PIDCAP period (Pilot Study for Intensive Data Collection and Analysis of Precipitation) from August to October 1995. Effects of the different temporal and spatial data resolutions on the variance are quantified and eliminated. For this purpose the water vapour content is used, which is derived from the GPS (Global Positioning System) network over Sweden and Finland by ELGERED et al. (1997). SSM/I and cps data indicate that REMO overestimates the total water vapour content by about 2 kgm(-2).

Description: A three-dimensional fully coupled high resolution atmosphere-ocean model for the BALTEX (Baltic Sea Experiment) region has been developed from two independent models, the atmospheric regional model REMO and the Kiel Baltic Sea model. The coupled model was set up in the framework of the BALTEX program to contribute to one of its major objectives, the investigation and quantification of the energy and water cycle in the Baltic Sea and its catchment area. As a first step towards the fully coupled system, sensitivity studies with different forcings for its uncoupled components, the atmosphere and ocean models. were performed. These sensitivity studies demonstrated that both models are able to produce rea onable results which in turn can act as forcing for the respective other model. In the first simulation of the fu lly coupled system the modeled sea surface temperatures (SST) agree well with satellite observations. Thus they are at least as good as the previously used SSTs from operational analyses and in some cases even better. The detailed evaluation of the coupled model results reveals that often the coupling effects are superimposed by advective influences and that only under specific conditions the atmospheric variables show a remarkable response to different fluxes. The atmosphere-ocean model is coupled directly via the corresponding fluxes across the interface between atmosphere and ocean. For the here presented simulation no flux corrections were necessary. Thus a consistent model system has been developed which can be utilized for further studies of the energy and water cycle in the BALTEX area.