Mapping of the PARASOUND penetration depth in the Pine Island Bay, West Antarctica

Summary: The PARASOUND-data of the study area show all a relatively small penetration depth. The acoustic penetration is between 0 and 45 m, but in most parts of the area less than 5 m. The maximum of 45 m occurs only at one point. The bathymetry is very rugged in most parts of the study area. Due to the sensibility of the PARASOUNDsystem to a dipping seafloor the wide low penetration depth is not only an effect of the physical properties of the seafloor, but also of the relief. Data quality in western and northern parts of the study area was strongly influenced by sea ice conditions, due to inconstant speed, ramming and the ice itself. In some parts of PIB West disturbances during measurements were so strong that the seafloor could not be located. While PIB North has almost no penetration of more than 5 m, PIB West has some parts of deeper penetration in troughs and depressions. High penetration was almost exclusively found in the deep troughs – especially in depressions within the troughs. Since PIB South includes the deepest troughs, it is the area where one can find the penetration at its largest; here the high penetration is most frequently. This part has also the highest density of data, the largest continuous area of penetration larger than 5 m and the deepest penetration depth (45 m

Mid-Pleistocene Mg/Ca, temperature and stable isotopes from Globigerinoides ruber white and Globorotalia inflata of sediment core GeoB3801-6 from the subtropical South Atlantic

The glacial marine isotope stage 14 (MIS 14) appears in many climate records as an unusually warm glacial. During this period an almost monospecific, up to 1.5 m thick, laminated layer of the giant diatom Ethmodiscus rex has been deposited below the South Atlantic Subtropical Gyre. This oligotrophic region is today less favorable for diatom growth with sediments typically consisting of calcareous nannofossil oozes. We have reconstructed temperatures and the stable oxygen isotopic compositions of sea surface and thermocline water (d18Ow) from planktonic foraminiferal (Globigerinoides ruber and Globorotalia inflata) Mg/Ca and stable oxygen isotopes to test whether perturbations in surface ocean conditions contributed to the deposition of the diatom layer at ~530 kyr B.P. Temperatures and d18Ow values reconstructed from this diatom ooze interval are highly variable, with maxima similar to interglacial values. Since the area of the Ethmodiscus oozes resembles the region where Agulhas rings are present, we interpret these hydrographic changes to reflect the varying influence of warm and saline water of Indian Ocean origin that entered the Subtropical Gyre trapped in Agulhas rings. The formation of the Ethmodiscus oozes is associated with a period of maximum Agulhas leakage and a maximum frequency of Agulhas ring formation caused by a termination-type position of the Subtropical Front during the unusual warm MIS 14. The input of silica through the Agulhas rings enabled the shift in primary production from calcareous nannoplankton to diatoms, leading to the deposition of the massive diatom oozes

Deep crustal refraction and reflection seismics; crustal and sedimentary structures and geodynamic evolution of the West Antarctic continental margin and Pine Island

The RV Polarstern expedition ANTARKTIS-XXIII/4 (ANT-XXIII/4) began on 10 February 2006 from Punta Arenas returning on 11 April 2006. The main goal of the expedition was to study glaciomarine sedimentation and the evolution of the tectonic-geodynamic setting of the southern Amundsen Sea and Pine Island bay. Crustal and sedimentary structures on the West Antarctic continental margin and Pine Island were surveyed using deep crustal refraction and reflection seismic geophysical methods

Deep crustal refraction and reflection seismics. Crustal and sedimentary structures and geodynamic evolution of the West Antarctic continental margin and Pine Island

Accurate models of the geodynamic-tectonic evolution contain some of the most important parameters for understanding and reconstruction of the palaeo- environment. Geophysical surveys of the sedimentary sequences and the underlying basement of the shelf and slope of the southern Amundsen Sea, Pine Island Bay and its adjacent continental rise allow reconstructions of the formation of the tectonic and older sedimentary processes. The following objectives are addressed as part of a cooperative project between the Vernadsky Institute in Moscow (Dr. Gleb Udintsev) and AWI:• Identification of the boundaries between suspected crustal blocks and volcanic zones in Pine Island Bay. The glacier troughs and Pine Island Bay are thought to have developed along such tectonic boundaries.• During and after separation from the Chatham Rise and Campbell Plateau (New Zealand), the continental margin of Marie Byrd Land developed as a passive margin, probably accompanied by intensive volcanism. The question is whether this volcanism occurred mainly during the rifting process or during post-rift phases, or if it developed in relation to the West Antarctic rift system.• Recording of the sedimentary sequences across the shelf, slope and the continental rise, using deep reflection seismics, sub-bottom profiler (Parasound) and swath-bathymetry (Hydrosweep) in order to derive a sedimentation model.• Mapping of the acoustic basement and its structure with deep seismic reflection methods to obtain the tectonic geometries and boundary conditions necessary to understand sediment transport and depositional processes.info:eu-repo/semantics/publishe

Crustal and Sedimentary Structures and Geodynamic Evolution of the West Antarctic Continental Margin and Pine Island Bay

Since the last glacial maximum the West Antarctic Ice Sheet (WAIS) with a base mostly beneath the present-day sea-level has experienced dramatic volume changes within short periods of time. Studies are urgently required to show how these short-term variations are related to volume changes in the older geological past. Next to the ice drainage basins of the Weddell Sea and the Ross Embayment, Pine Island Bay forms the third-largest outflow area for the West Antarctic ice-shield. The main ice streams from the WAIS into Pine Island Bay flow through the Pine Island and Thwaites Glacier systems, through which most of the glacial-marine sediments onto the shelf of Pine Island Bay and across the continental slope into the deep sea have been transported. Geophysical surveys of the sedimentary sequences and the underlying basement of the shelf and slope of the southern Amundsen Sea, Pine Island Bay and its adjacent continental rise would allow reconstructions of the formation of the tectonic and older sedimentary processes as well as to find out about the history of large-scale glaciation in West Antarctica. Accurate models of the geodynamic- tectonic evolution contain some of the most important parameters for understanding and reconstruction of the palaeo-environment.info:eu-repo/semantics/publishe

Crustal and Sedimentary Structures and Geodynamic Evolution of the West Antarctic Continental Margin and Pine Island Bay

Since the last glacial maximum the West Antarctic Ice Sheet (WAIS) with a base mostly beneath the present-day sea-level has experienced dramatic volume changes within short periods of time. Studies are urgently required to show how these short-term variations are related to volume changes in the older geological past. Next to the ice drainage basins of the Weddell Sea and the Ross Embayment, Pine Island Bay forms the third-largest outflow area for the West Antarctic ice-shield. The main ice streams from the WAIS into Pine Island Bay flow through the Pine Island and Thwaites Glacier systems, through which most of the glacial-marine sediments onto the shelf of Pine Island Bay and across the continental slope into the deep sea have been transported. Geophysical surveys of the sedimentary sequences and the underlying basement of the shelf and slope of the southern Amundsen Sea, Pine Island Bay and its adjacent continental rise would allow reconstructions of the formation of the tectonic and older sedimentary processes as well as to find out about the history of large-scale glaciation in West Antarctica. Accurate models of the geodynamic- tectonic evolution contain some of the most important parameters for understanding and reconstruction of the palaeo-environment.info:eu-repo/semantics/publishe