Description: High resolution 230Thex and 10Be and biogenic barium profiles were measured at three sediment gravity cores (length 605–850 cm) from the Weddell Sea continental margin. Applying the 230Thex dating method, average sedimentation rates of 3 cm/kyr for the two cores from the South Orkney Slope and of 2.4 cm/kyr for the core from the eastern Weddell Sea were determined and compared to δ18O and lithostratigraphic results. Strong variations in the radionuclide concentrations in the sediments resembling the glacial/interglacial pattern of the δ18O stratigraphy and the 10Be stratigraphy of high northern latitudes were used for establishing a chronostratigraphy. Biogenic Ba shows a pattern similar to the radionuclide profiles, suggesting that both records were influenced by increased paleoproductivity at the beginning of the interglacials. However, 230Thex0 fluxes (0 stands for initial) exceeding production by up to a factor of 4 suggest that sediment redistribution processes, linked to variations in bottom water current velocity, played the major role in controlling the radionuclide and biogenic barium deposition during isotope stages 5e and 1. The correction for sediment focusing makes the ‘true’ vertical paleoproductivity rates, deduced from the fluxes of proxy tracers like biogenic barium, much lower than previously estimated. Very low 230Thex0 concentrations and fluxes during isotope stage 6 were probably caused by rapid deposition of older, resedimented material, delivered to the Weddell Sea continental slopes by the grounded ice shelves and contemporaneous erosion of particles originating from the water column.

Description: High resolution 230Thex and 10Be and biogenic barium profiles were measured at three sediment gravity cores (length 605–850 cm) from the Weddell Sea continental margin. Applying the 230Thex dating method, average sedimentation rates of 3 cm/kyr for the two cores from the South Orkney Slope and of 2.4 cm/kyr for the core from the eastern Weddell Sea were determined and compared to δ18O and lithostratigraphic results. Strong variations in the radionuclide concentrations in the sediments resembling the glacial/interglacial pattern of the δ18O stratigraphy and the 10Be stratigraphy of high northern latitudes were used for establishing a chronostratigraphy. Biogenic Ba shows a pattern similar to the radionuclide profiles, suggesting that both records were influenced by increased paleoproductivity at the beginning of the interglacials. However, 230Thex0 fluxes (0 stands for initial) exceeding production by up to a factor of 4 suggest that sediment redistribution processes, linked to variations in bottom water current velocity, played the major role in controlling the radionuclide and biogenic barium deposition during isotope stages 5e and 1. The correction for sediment focusing makes the ‘true’ vertical paleoproductivity rates, deduced from the fluxes of proxy tracers like biogenic barium, much lower than previously estimated. Very low 230Thex0 concentrations and fluxes during isotope stage 6 were probably caused by rapid deposition of older, resedimented material, delivered to the Weddell Sea continental slopes by the grounded ice shelves and contemporaneous erosion of particles originating from the water column.

Description: Stable isotope records, and sedimentological and organic-geochemical investigations of marine sediments from the east Greenland Sea at 70°N provide important information about glacial-interglacial variations of paleoenvironments through the last 225 kyr.The oxygen isotope records established on the planktonic foraminifer N. pachyderma sin. show some excursions from the global climate pattern, probably due to local/regional overprint by meltwater supply. The cold, low-saline East Greenland Current and fluctuations in sea-ice covering were a crucial element controlling the carbonate production in the subsurface/surface water column in the east Greenland Sea over the last 225 kyr. The beginning of Termination Ia is AMS 14C dated at about 15.8 kyr B.P. and interpreted as a Greenland Ice Sheet meltwater signal. The stage 2/3 boundary is dated at about 25 kyr B.P. The timing of the onset of the last deglacial meltwater event is about 800 years earlier than that of the Barents Shelf Ice Sheet meltwater signal recorded in the Fram Strait.Several major pulses of increased supply of coarse-grained terrigenous material by glacio-marine processes occurred during the last 225 kyr. The supply of coarse-grained ice-rafted debris at the East Greenland continental slope reached maximum values during the last glacial maximum (stage 2/Weichselian, 15-19 kyr B.P.).The drastic climatic change and the gradual retreat of continental ice masses/glaciers during the last deglaciation (Termination I) are clearly documented in the marine sedimentary sequences from shelf and upper slope environments. This process resulted in distinctly decreased supply and deposition of ice-rafted debris in the open shelf-upper slope environments. During Termination I, the sea-ice cover also decreased, causing an increase in surface-water productivity, indicated by increased organic carbon and biogenic opal deposition.

Description: To use the scientific resource of marine data effectively the information system PANGAEA was developed. The system guarantees longtime storage of the data in consistent formats and provides easy access for the scientific community via World Wide Web or a system specific client software with high functionality. The system is able to store data together with raw data, evaluated data and all related meta-information necessary for their understanding. The system provides standardized import and export routines, easy access with uniform retrieval functions, and tools for the visualization of data. The system is designed as a network with client/server technology providing access and data exchange through the Internet.The great variety of parameters, methods, calibrations and interpretations used in paleoenvironmental reconstruction, as well as the modification of established methods, are major obstacles to the integrative use of data sets in a common system. The challenge of managing these heterogenic and dynamic data was met in PANGAEA through a highly flexible data model consisting of a relational data structure in combination with specialized server software generating an object-oriented view of the data.The simplified data structure reflects the standard processing steps for paleo-data. Lists including standardized meta-information are connected to the main data fields: different projects working in the field of paleoceanography carry out expeditions for sampling. During a cruise at a number of locations different samples may be taken or measurements made. At distinct points/intervals the medium to be investigated (e.g. sediment, water or ice) is subsampled or measured for different requirements. From each sample one or more analytical data points will be produced which can be found on the DATA level, with the related meta-information. The combination of the DATA, 'Parameter' and 'Method' fields is the essential part of the model, which allows the definition and storage of new, unique parameters by the user at any time. The middleware allows the user to retrieve complex data matrices, e.g. time slices.The main server runs SYBASE as the database management software. The client software for access to the server was written in 4th Dimension (ACI); the WWW-client software is written in JAVA. 4D provides tools for the design of a graphical user interface and allows optional compilation of the front end software code for the different operating systems found in personal computers (MacintoshOS, Windows).For the geographical presentation of data the tool PanMap was developed, which is either directly connected to the database front end or can be used as a stand-alone application. PanMap can be called directly by the user to draw sampling sites in a geographical context after selecting the required data set by the retrieval tool. Sites can be labelled with meta-data as well as analytical data. The PanPlot tool has a similar link to the database as PanMap and allows the user to plot data versus depth or time. The software is avialable on http://www.pangaea.de/Software/