ALBERT

Beschreibung: The South Sandwich Islands and associated seamounts constitute the volcanic arc of an active subduction system situated in the South Atlantic. We introduce a map of the bathymetry and geological setting of the South Sandwich Islands and the associated East Scotia Ridge back-arc spreading centre that consists of two sides: side 1, a regional overview of the volcanic arc, trench and back-arc, and side 2, detailed maps of the individual islands. Side 1 displays the bathymetry at scale 1:750 000 of the intra-oceanic, largely submarine South Sandwich arc, the back-arc system and other tectonic boundaries of the subduction system. Satellite images of the islands on side 2 are at scales of 1:50 000 and 1:25 000 with contours and main volcanological features indicated. These maps are the first detailed topological and bathymetric maps of the area. The islands are entirely volcanic in origin, and most have been volcanically or fumarolically active in historic times. Many of the islands are ice-covered, and the map forms a baseline for future glaciological changes caused by volcanic activities and climate change. The back-arc spreading centre consists of nine segments, most of which have rift-like morphologies.

Beschreibung: We will present new multibeam bathymetry data that make the Anvers-Hugo Trough west of the Antarctic Peninsula one of the most completely surveyed palaeo-ice stream pathways in Antarctica. We interpret landforms revealed by these data as indicating that subglacial water availability played an important role in facilitating ice stream flow in the trough during late Quaternary glacial periods. Specifically, we observe a set of northward-shoaling valleys that are eroded into the upstream edge of a sedimentary basin, extend northwards from a zone containing landforms typical of erosion by subglacial water flow, and coincide spatially with the onset of mega-scale glacial lineations. Water was likely supplied to the ice stream bed episodically as a result of outbursts from a subglacial lake previously hypothesized to have been located in the Palmer Deep basin on the inner continental shelf. In a palaeo-ice stream confluence area, close juxtaposition of mega-scale glacial lineations with landforms that are characteristic of slow, dry-based ice flow, suggests that water availability was also an important control on the lateral extent of these palaeo-ice streams. These interpretations are consistent with the hypothesis that subglacial lakes or areas of elevated geothermal heat flux play a critical role in the onset of many large ice streams. The interpretations also have implications for the dynamic behaviour of the Anvers-Hugo Trough palaeo-ice stream and, potentially, of several other Antarctic palaeo-ice streams. Keywords: multibeam bathymetry, ice stream, subglacial water, landform

Beschreibung: The Drake Passage is an oceanic gateway of about 850km width located between South America and the Antarctic Peninsula that connects the southeastern Pacific Ocean with the southwestern Atlantic Ocean. It is an important gateway for mantle flow, oceanographic water masses, and migrations of biota. This sector developed within the framework of the geodynamic evolution of the Scotia Arc, including continental fragmentation processes and oceanic crust creation, since the oblique divergence of the South American plate to the north and the Antarctic plate to the south started in the Eocene. As a consequence of its complex tectonic evolution and subsequent submarine processes, as sedimentary infill and erosion mainly controlled by bottom currents and active tectonics, this region shows a varied physiography. We present a detailed map of the bathymetry and geological setting of the Drake Passage that is mainly founded on a new compilation of precise multibeam bathymetric data obtained on 120 cruises between 1992 and 2015, resulting in a new Digital Bathymetric Model with 200x200 m cell spacing. The map covers an area of 1,465,000km2 between parallels 52°S and 63°S and meridians 70°W and 50°W at scale 1:1,600,000 allowing the identification of the main seafloor features. In addition, the map includes useful geological information related to magnetism, seismicity and tectonics. This work constitutes an international cooperative effort and is part of the International Bathymetric Chart of the Southern Ocean project, under the Scientific Committee on Antarctic Research umbrella.

Beschreibung: IBCSO is a major project for the entire Ocean and Earth Science community since it not only contributes to international research programmes but also to global mapping projects like the General Bathymetric Chart of the Oceans (GEBCO) and to the production of Nautical Charts in Antarctic waters. The IBCSO Editorial Board comprises representatives from SCAR-nations conducting specific research in the Antarctic Treaty Area and has an interest in developing an improved bathymetric chart of the Southern Ocean for scientific purposes. These include (a) creating a chart of the seafloor for interpreting seabed geology, (b) building the basis for habitat maps and modelling, and (c) mapping and tracing the pathways of deep oceanic currents. The objective of IBCSO is the production of a homogeneous and seamless bathymetric grid for the Southern Ocean with an associated meta-database. Echosounding data in these harsh regions are heterogeneous in terms of age, acquisition system, environmental condition, accuracy, and documentation. In ice-covered regions, systematic multibeam surveys are rare. As a consequence, the production of a bathymetric grid requires special expertise in hydrography and ocean mapping. Metadata is needed for quality assessment and accurate sonar data processing and gridding. Bathymetric grids have been compiled in regions of special research activities around the Antarctic continent (Bellingshausen/Amundsen Seas, Weddell Sea, Prydz Bay, Kerguelen Plateau, Antarctic Peninsula, and Ross Sea). The results of these regional compilations will be used as basis for the production of the first seamless Circum-Antarctic bathymetric map. The IBCSO version 1 will consequently be an assembly of existing grids produced by different research institutes. The regions not covered will be modelled by using single- and multibeam sonar data in combination with predicted bathymetry. Professional production of this bathymetric chart requires the utilization of a Geographic Information System (GIS) for data collection, storage, manipulation, and visualization. The version 1 IBCSO product will cover the ocean and land topography of the Antarctic Treaty Area south of 60°S, and include the coast-line, and toponymic. The current status of data collection and map production will be presented and discussed, including questions about the model parameterization and gridding techniques. The use of predicted bathymetry in regions of permanent ice-coverage (Weddell Sea, Amundsen Sea) will be introduced. It is shown that predicted bathymetry cannot simply be used in place of real sonar measurements, since differences of several hundred meters in depth were noted particularly in coastal and shelf regions. The horizontal resolution of the version 1 grid will be 2km by 2km. After publication in 2012, the IBCSO grid will be made available to the public.