Description: Large oceanic changes occurred during the last transition from glacial to interglacial conditions (Termination I), which significantly affected pelagic and benthic environments. This study presents results of a quantitative investigation of benthic foraminifera at four sites distributed along a north-south transect across the northern North Atlantic with a high temporal resolution (k 200 years). Benthic foraminifera are examined in samples (1-2 cm sampling intervals) from four long sediment cores located in the southern Fram Strait, the Greenland-Iceland-Norwegian Sea (GIN Sea), and the Rockall Plateau. The most prominent species of benthic foraminifera include Oridorsalis nnlbolzatlls, Cibicidoides wl~ellerstoufi,C assidulina spp. group, P!jrgo rotalaria, Globocassidrrliiza sllbg-lobosa and tubes of agglutinated taxa. In each core, the climatic amelioration at Termination I is recorded to have occurred in two steps. A first INDAR maximum (INDividuals Accumulation Rate = ind/cm2 ky; GIN Sea: average 3,000-6,000 ind/cm2 ky, Rockall Plateau: average 150 ind/cm2 ky) is followed by a period of lower values. A second maximum reveals slightly lower values than the older maximum. Interglacial INDAR values average 700 ind/cm2 ky for the GIN Sea and 200 ind/cm2 ky on the Rockall Plateau. This is roughly twice that of typical glacial values. Meltwater events, identified by stable isotope data and sea-surface temperature reconstructions based on planktic foraminiferal transfer functions, are marked by an increase in endobenthic and opportunistic species. A decrease of reconstructed sea-surface temperatures appears synchronous with the relative INDAR minimum that occurs between the two INDAR maxima. The results indicate a close coupling of sea-surface processes to the benthic realm ("pelagic-benthic coupling") with a longitudinally variable strength. The climate signal at the Rockall Plateau revealed by the fossil benthic foraminifera shows a lower amplitude than that of the GIN Sea. The second, younger INDAR maximum is characterized by an increased abundance of epibenthic species at all core locations, suggesting extended lateral bottom currents. In comparison with various palaeo-climatological data sets, the variability of fossil benthic foraminiferal abundances in the GIN Sea show a distinct coherence with changes of atmospheric temperatures, sea-surface temperatures and the postglacial sea level rise. The variability of the benthic foraminiferal fauna is principally in phase with climate change events.

Description: This diploma thesis investigates variations in mixing ratios of very short lived substances (VSLS) during the DRIVE (Diurnal and Regional Variability of halogen Emissions) campaign in the tropical East Atlantic conducted during P399 2/3 from May to June 2010. The main focus lies on the diurnal and regional variability of three halocarbons influenced by meteorological factors at six 24 h stations. For this reason, regular ship measurements of temperature, wind, air pressure and humidity were complemented by radiosonde launches and air samples for the trace gas investigation. According to the radiosonde measurements a changeover between tropical and extra tropical air masses is observed at about 30° N. In contrast to the dominating trade wind regime with northeasterly winds, the ship cruise was mainly exposed to north-northwesterly winds with moderate weather conditions. In addition, the height of the atmospheric boundary layer is determined from the atmospheric profile, ranging from 500 m – 1700 m over open ocean. At coastal areas, especially at the Mauritanian upwelling, the boundary layer stays at the surface. For an evaluation of the wind measurements, wind speed and direction are compared to a high resolution ERA-Interim data set and, to NCEP/NCAR Reanalysis Project 1 Data (NNRP-1). In situ ship measurements show higher correlations for the wind speed (ERA-Interim: r = 0.91, NNRP-1: r = 0.79) than for the wind direction (ERA-Interim: r = 0.69, NNRP-1: r = 0.67). Recalculating the correlation coefficients for the same temporal resolution (6-hourly) results in an improvement of the correlations, indicating a good agreement between the observed and simulated wind. For the determination of potential source regions, the trajectory model HYSPLIT is used to investigate the origin of the observed air masses. The air mass history is analyzed 315 h backwards, indicating an air mass origin mainly above the North Atlantic during leg 2 but also above the Arctic Ocean during leg 3. During the 24 h stations close to the coast predominantly younger and local sources seem to influence the observed trace gas mixing ratios (mean CH2Br2/CHBr3 ratio: 0.4) with a partly strong dependency on the wind direction (r 〉 0.81). Especially the methyl iodide mixing ratios show a strong relation to air masses originating at the Banc d’Arguin National Park. In contrast to that, bromoform and dibromomethane show an increase of the mixing ratios connected to trajectories passing the coastal areas of Mauritania and Western Sahara. Increased mixing ratios of the observed trace gases concentrations with highest values of 8.9 ppt (bromoform), 3.31 ppt (dibromomethane) and 1.25 ppt (methyl iodide) are observed in combination with lowest boundary layer heights. With correlation coefficients of r = -0.90 (bromoform), r = -0.91 (dibromomethane) and r = -0.63 (methyl iodide) especially the mixing ratios of the longer lived bromocarbons seem to be strongly connected to the boundary layer height. However, the highest atmospheric bromoform mixing ratio of 9.8 ppt was not observed at the Mauritanian upwelling (leg 2), but close to Lisbon (leg 3) with the Rio Tejo as a potential source region. This implies the significance of regional sources as well as the consideration of the current lower atmospheric state for the variations of the VSLS mixing ratios

Description: Oxygen and carbon isotope measurements were carried out on tests of planktic foraminifers N. pachyderma (sin.) from eight sediment cores taken from the eastern Arctic Ocean, the Fram Strait, and the leeland Sea, in order to reconstruct Arctic Ocean and Norwegian-Greenland Sea circulation patterns and ice covers during the last 130,000 years. In addition, the influence of ice, temperature and salinity effects on the isotopic signal was quantified. Isotope measurements on foraminifers from sediment surface sampies were used to elucidate the ecology of N. pachyderma (sin.). Changes in the oxygen and carbon isotope composition of N. pachyderma (sin.) from sediment surface sampies document the horizontal and vertical changes of water mass boundaries controlled by water temperature and salinity, because N. pachyderma (sin.) shows drastic changes in depth habitats, depending on the water mass properties. It was able to be shown that in the investigated areas a regional and spatial apparent increase of the ice effect occurred. This happened especially during the termination I by direct advection of meltwaters from nearby continents or during the termination and in interglacials by supply of isotopically light water from rivers. A northwardly proceeding overprint of the "global" ice effect, increasing from the Norwegian-Greenland Sea to the Arctic Ocean, was not able to be demonstrated. By means of a model the influence of temperature and salinity on the global ice volume signal during the last 130.000 years was recorded. In combination with the results of this study, the model was the basis for a reconstruction of the paleoceanographic development of the Arctic Ocean and the Norwegian-Greenland Sea during this time interval. The conception of a relatively thick and permanent sea ice cover in the Nordic Seas during glacial times should be replaced by the model of a seasonally and regionally highly variable ice cover. Only during isotope stage 5e may there have been a local deep water formation in the Fram Strait.