Calcareous nannofossils of ODP Leg 107 holes

This paper summarizes the nannoplankton biostratigraphy and the paleoenvironmental interpretations obtained from Leg 107 in the Tyrrhenian Sea. Marine sediments are ranging in age from late Tortonian to Recent. The Mediterranean as a semiclosed adjacent sea of the Atlantic is strongly controlled by paleoceanographic changes in the Atlantic which are related to the global climatic evolution. This influence of the Atlantic is more pronounced in the western than in the eastern Mediterranean. The occurrence of sapropels and sapropelic layers also in the western Mediterranean was shown for the first time.

Pliocene-Pleistocene stable isotope record of ODP Site 107-653

Planktonic foraminiferal oxygen and carbon isotope analyses from Tyrrhenian Sea Ocean Drilling Program (ODP) Site 653 provide a continuous record of the Pliocene-Pleistocene paleoceanographic history of the Mediterranean. Long-term trends in oxygen isotopes primarily reflect changes in global climatic conditions, with a more local or regional signal superimposed on this record. For example, significant enrichments in 18O due to decreases in surface water temperature and/or increases in continental ice volume occurred at 3.1, 2.7, 2.1, 1.6, and 0.4 Ma. In contrast to most open-ocean results, the early Pliocene 6lsO record of Site 653 exhibits high-amplitude fluctuations indicative of very unstable climatic conditions in this region. Another unique aspect of this Mediterranean d18Orecord is the pronounced cooling at the Pliocene/Pleistocene boundary. The carbon isotope record for Site 653 also exhibits high-amplitude variability throughout the Pliocene-Pleistocene. This variability most probably reflects changes in the carbon isotopic composition of the source of Mediterranean surface waters.

Pleistocene-Pliocene strontium-isotope ratios of ODP Site 107-653 (Table 1)

Strontium isotopic determinations were made on samples from the Pliocene-Pleistocene sequence recovered at ODP Hole 653A, the proposed "deep-sea type section" for the Mediterranean region. Biostratigraphic correlations can be combined with the patterns of variations in the 87Sr/86Sr values to delineate the following: (1) the earliest Pliocene (MP11 to basal MP12 zones) is distinguished by fluctuations in the ratio, probably related to the unstable paleoceanographic conditions following the Zanclean flooding and initial in-filling of the Mediterranean after the Messinian desiccation, (2) during most of the Pliocene between approximately 4.5 and 2.4 Ma (MP12 to MP15 zones) the 87Sr/86Sr values remain relatively constant, producing a plateau in the strontium isotope-depth curve for this period, and (3) beginning at approximately 2.4 Ma (across the MP15/MP16 boundary) and continuing into the latest Pleistocene, the 7Sr/86Sr values increase significantly but show fluctuations that have both positive and negative slopes. The presence of a plateau in the curve generated for the Mediterranean type section duplicates in greater detail the late Neogene results reported by DePaolo (1986, doi:10.1130/0091-7613(1986)14<103:DROTNS>2.0.CO;2). The virtual lack of change in the ratio between 4.5 and 2.4 Ma essentially eliminates strontium isotopes as a high-resolution correlation method for this period. The fluctuations in the ratio beginning at 2.4 Ma may be a reflection of major climatic changes occurring in the latest Pliocene-Pleistocene. The relationship between glacial-interglacial cycles and seawater 87Sr/86Sr values suggested by DePaolo (1986) and Capo and DePaolo (1987) is uncertain but should be tested as significant increases and decreases in 87Sr/86Sr of seawater have apparently occurred since 2.4 Ma.

Particle size of Saharan dust in the Atlantic Ocean, from October 2012 to November 2013

Mineral dust has a large impact on regional and global climate, depending on its particle size. Especially in the Atlantic Ocean downwind of the Sahara, the largest dust source on earth, the effects can be substantial but are poorly understood. This study focuses on seasonal and spatial variations in particle size of Saharan dust deposition across the Atlantic Ocean, using an array of submarine sediment traps moored along a transect at 12° N. We show that the particle size decreases downwind with increased distance from the Saharan source, due to higher gravitational settling velocities of coarse particles in the atmosphere. Modal grain sizes vary between 4 and 33 µm throughout the different seasons and at five locations along the transect. This is much coarser than previously suggested and incorporated into climate models. In addition, seasonal changes are prominent, with coarser dust in summer, and finer dust in winter and spring. Such seasonal changes are caused by transport at higher altitudes and at greater wind velocities during summer than in winter. Also the latitudinal migration of the dust cloud, associated with the Intertropical Convergence Zone, causes seasonal differences in deposition as the summer dust cloud is located more to the north, and more directly above the sampled transect. Furthermore, increased precipitation and more frequent dust storms in summer coincide with coarser dust deposition. Our findings contribute to understanding Saharan dust transport and deposition relevant for the interpretation of sedimentary records for climate reconstructions, as well as for global and regional models for improved prediction of future climate.

Global compilation of benthic data sets I

Approaches to quantify the organic carbon accumulation on a global scale generally do not consider the small-scale variability of sedimentary and oceanographic boundary conditions along continental margins. In this study, we present a new approach to regionalize the total organic carbon (TOC) content in surface sediments (<5 cm sediment depth). It is based on a compilation of more than 5500 single measurements from various sources. Global TOC distribution was determined by the application of a combined qualitative and quantitative-geostatistical method. Overall, 33 benthic TOC-based provinces were defined and used to process the global distribution pattern of the TOC content in surface sediments in a 1°x1° grid resolution. Regional dependencies of data points within each single province are expressed by modeled semi-variograms. Measured and estimated TOC values show good correlation, emphasizing the reasonable applicability of the method. The accumulation of organic carbon in marine surface sediments is a key parameter in the control of mineralization processes and the material exchange between the sediment and the ocean water. Our approach will help to improve global budgets of nutrient and carbon cycles.

(Table 2, Page 106-107) Composition of the HCl-soluble fraction in Barents Sea iron-manganese deposits

Ferromanganese concretions from ten stations in the Barents Sea have been analysed for 24 elements. The deposits occur as discoidal and flat concretions and as coatings, in the latter case on lithified or detrital material or as extensive pavements on the Svalbard shelf. The concretions are compositionally similar to Baltic concretions but differ considerably from deep-ocean nodules, particularly in Cu, Ni and Co contents. Statistical analyses reveal distinct correlations between Mn, Na, Ba, Ni and Cu; the Mn-rich coatings showed enrichment of Mo, Zn and possibly Co in a Mn-phase. The iron phase holds high concretions of P and As. Two iron-rich concretions with high contents of P, Ca, Sr, Y, Yb and La were found east and northeast of Spitsbergen Banken, probably indicating upwelling of nutrient-rich, cold polar water along the Svalbard shelf.

Biochemical investigation of multicorer sediment profile PS74/107-2

To detect and track the impact of large-scale environmental changes in a the transition zone between the northern North Atlantic and the central Arctic Ocean, and to determine experimentally the factors controlling deep-sea biodiversity, the Alfred- Wegener-Institute for Polar and Marine Research (AWI) established the deep-sea long-term observatory HAUSGARTEN, which constitutes the first, and until now only open-ocean long-term station in a polar region. Virtually undisturbed sediment samples have been taken using a video-guided multiple corer (MUC) at 13 HAUSGARTEN stations along a bathymetric (1,000 - 4,000 m water depth) and a latitudinal transect in 2,500 m water depth as well as two stations at 230 and 1,200 m water depth within the framework of the KONGHAU project. Various biogenic sediment compounds were analyzed to estimate the input of organic matter from phytodetritus sedimentation, benthic activities (e.g. bacterial exoenzymatic activity), and the total biomass of the smallest sediment-inhabiting organisms (size range: bacteria to meiofauna).