ALBERT

Description: Electromagnetic (EM) surveys are widely used in geophysical study. Reliable 3-D forward modeling is required for the inversion and interpretation of geophysical data. We have introduced a novel method for 3-D EM modeling using stretching grids, which uses a multigrid iterative solver for solving the formed linear system of equations based on the staggered finite-difference method. The developed algorithm is applied for the simulation of the magnetotelluric fields. We have tested this new algorithm using synthetic geoelectric models. The proposed multigrid method using stretching grids is also compared with the preconditioned Krylov-subspace solvers, the biconjugate gradients stabilized method, and the generalized minimum residual method. The developed multigrid method is proved to be more stable and requires less iterations to converge.

Description: Der Dorschbestand in der westlichen Ostsee befindet sich seit Jahren außerhalb sicherer biologischer Grenzen. Diese Situation hat sich jetzt weiter verschlechtert, so dass im Jahr 2016 die Anzahl der einjährigen Jungdorsche nur 3.5% des durchschnittlichen Nachwuchses betrug. Der Internationale Rat für Meeresforschung (ICES) hat deshalb eine drastische Reduzierung der kommerziellen Fänge im Jahr 2017 angeraten. Leider ist die Politik dieser Empfehlung nicht gefolgt und es sind etwa doppelt so hohe Fänge erlaubt worden. In Deutschland beschlossene finanzielle Hilfsmittel für die Fischer tragen ebenfalls nicht zur Verringerung dieser Fänge bei. Die wenigen einjährigen Dorsche von 2016 werden daher in 2017 stark befischt, bevor sie im Jahr 2018 den Elternbestand stellen. Es ist zu befürchten, dass der Nachwuchs von diesem viel zu kleinen Elternbestand ganz ausbleibt und der westliche Dorschbestand im Jahr 2019 zusammenbricht, mit den entsprechenden drastischen Folgen für Berufs- und Angelfischerei. Um den Fortbestand des westlichen Dorsches zu sichern, schlagen wir vor, die Fischerei und Angelei auf Dorsch in der westlichen Ostsee für zwei Jahre einzustellen, mit Ausgleichszahlungen für Berufsfischer und Angelkutter.

Description: Practical course at sea for students of Biological Oceanography (MNF-bioc-301)

Description: The majority of M〉8.5 active plate boundary earthquakes has hypocenters located beneath the oceans in subduction zones. Post-hoc analysis shows that most of the surface deformation related to co-seismic stress release takes place on the seafloor, in many cases unleashing major tsunamis. The structure and morphology of the seafloor and shallow subbottom thus stores crucial information on sub-seafloor processes, such as permanent deformation by seismic slip or aseismic creep within the overriding plate and earthquake and tsunami generation. We have mapped the seafloor seaward of the Northern Chilean coast between about 19°S and 22°S down to the Northern Chile deep sea trench, using the ship-based Multibeam Echosounder EM122, Parasound, and AUV (autonomous underwater vehicle) – in selected subareas - at sufficient resolution to identify active tectonic fault structures and submarine mass wasting structures, to quantitatively assess young and active deformation of the overriding plate in the area, and quantify the extent of recent catastrophic downslope mass movements of sediment. Furthermore, the investigations serve as a site survey for the deployment of the GeoSEA seafloor geodetic array, to be installed immediately after completion of this cruise. The investigations were made timely by the 1st April 2014 Pisagua M=8.2 earthquake, that ruptured the plate interface in the northern part of the area of investigation. The central and southern parts are located in the last remaining locked seimotectonic segment along the Chilean active margin. In addition to providing the first data base for geomorphological and tectonic interpretation of geo-processes at the seafloor, the bathymetric mapping done during SO244 Leg 1 will provide an important data reference for possible post-earthquake surveys once this seismotectonic segment will have broken in the future.

Description: Cruise Report POS493 (AUV DeDAVE) – Canary Islands, January 26th to February 1st, 2016 - Test cruise for AUV “DeDAvE” around the Canary Islands

Description: The R/V SONNE expedition SO-249 is part of the research project BERING, conducted in the framework of the Russian-German Agreement on Marine and Polar Research and in close cooperation with U.S. American colleagues. The overarching goal of BERING is to elucidate the magmatic and tectonic evolution of the Bering Sea and its margins over the past ≥50 m.y. In particular, BERING investigates the physical and chemical conditions that control the development of subduction zones, including subduction initiation, evolution of mature arc systems, and the impact of subduction volcanism on the environment. R/V SONNE cruise SO- 249 BERING conducted geological, morphological, and biological studies in the in western the Aleutians, the Pacific seafloor subducting beneath the Aleutians and northern Kamchatka, and in the western Bering Sea. Besides extensive multi-beam mapping and sediment echo-sounder profiling, total of 150 dredge hauls have been conducted on the two legs of cruise SO-249. Of these, 91 delivered massive magmatic and/or metamorphic rocks, 34 volcaniclastic rocks including breccias containing lava fragments, 64 sedimentary rocks, and 19 Mn-Fe-Oxide crusts and nodules. No equipment was lost or seriously damaged. SO-249 achieved its major goals and the SO-249 sample set represents the most detailed sampling of the working areas to date. The on shore work program at Russian, German, and U.S.-American institutions includes geochronological, petrological and geochemical studies on igneous samples obtained during the cruise. The results of BERING will be integrated with those of previous campaigns (e.g. KOMEX, KALMAR), and work carried out within the World Oceans and GeoPRISMS initiatives. The main goal of biological sampling was to survey the benthic biodiversity in the study area. In addition, fresh specimens pertaining to specific taxa (Cnidaria, Brachiopoda, Cephalopoda, Echinodermata) were collected to supplement ongoing research projects. Of the 150 dredges taken, 150 (100%) contained sediment and 112 (74.7%) contained macrofauna. In addition to the 150 sediment samples, almost 1,500 single benthic, benthopelagic, and pelagic macrofaunal organisms were obtained. The majority of the objectives of biological sampling were reached, in particular with regard to obtaining fresh tissue for immunohistochemical, genomic, and transcriptomic analysis from various brachiopod and ophiuroid species.

Description: Dates of Cruise: 28. September to 01. October 2015 Projects: Student course CAU Kiel (MNF-Pher-110b)