Physical properties, sedimentation rates, and accumulation rates of bottom sediments from the Laptev Sea collected during SPASIBA-91 Russian-French Program

Humidity and wet and dry bulk densities were determined for bottom sediments of the Lena River marginal filter within a 700 km section from the outer boundary of the river delta. Earlier determinations of suspended matter concentration in water, material and grain-size composition and age of sediments were made along the same section. Sediment matter fluxes (accumulation rates), their changes in space and time (about 14 ka) were inferred from measurements of physical parameters. A correlation was found between the physical parameters of bottom sediments and changes in the Lena river marginal filter including those caused by sea-level fluctuations.

Radiocarbon ages and average physical properties of sediment cores obtained during Icebreaker Oden cruise OSO0910

To date, understanding of ice sheet retreat within Pine Island Bay (PIB) following the Last Glacial Maximum (LGM) was based on seven radiocarbon dates and only fragmentary seafloor geomorphic evidence. During the austral summer 2009-2010, restricted sea ice cover allowed for the collection of 27 sediment cores from the outer PIB trough region. Combining these cores with data from prior cruises, over 133 cores have been used to conduct a detailed sedimentological facies analysis. These results, augmented by 23 new radiocarbon dates, are used to reconstruct the post-LGM deglacial history of PIB. Our results record a clear retreat stratigraphy in PIB composed of, from top to base; terrigenous sandy silt (distal glacimarine), pebbly sandy mud (ice-proximal glacimarine), and till. Initial retreat from the outer-continental shelf began shortly after the LGM and before 16.4 k cal yr BP, as a likely response to rising sea level. Bedforms in outer PIB document episodic retreat in the form of back-stepping grounding zone wedges and are associated with proximal glacimarine sediments. A sub-ice shelf facies is observed in central PIB and spans ~12.3-10.6 k cal yr BP. It is possible that widespread impingement of warm water onto the continental shelf caused an abrupt and widespread change from sub-ice shelf sedimentation to distal glacimarine sedimentation dominated by widespread dispersal of terrigenous silt between 7.8 and 7.0 k cal yr BP. The final phase of retreat ended before ~1.3 k cal yr BP, when the grounding line migrated to a location near the current ice margin.

Physical oceanography and ADCP measurements during METEOR cruise M71/3

Work on M71-3 aimed to answer the question whether phosphate loss and incomplete utilisation of nitrate on the one hand, or dinitrogen fixation on the other hand are responsible for unusual nutrient ratios in the water column of the eastern Mediterranean Sea. We investigated the reason for unusually depleted 15N/14N ratios in dissolved nitrate, suspended matter and surface sediments of that oligotrohic ocean basin. During a total of 18 days of ship time on R/V METEOR, Leg 3 OF M71 performed water column and surface sediment work in the eastern Mediterranean Sea (Heraklion-Istanbul). Stations will be aligned on one E-W and two N-S transects and sampled all major basins and water masses. On stations, CTD casts were obtained and water samples for nutrient concentrations were taken. These samples and those of suspended matter and surface sediment will be analysed for the stable nitrogen isotope composition of dissolved nitrate, suspended matter, and surface sediments. In addition, phytoplankton samples were be taken and experiments were be carried out to determine N2 fixation rates, genetic expressions of nitrogen fixation, and the composition of microbial and algal assemblages. One mooring of sediment traps (Ierapetra Deep) was be deployed and will be recovered in September 2007 to monitor changes in particle flux and its isotope signature over a seasonal cycle.

Oxygen isotope composition of benthic foraminifera ofthe Florida Street

We present a new method for the quantitative reconstruction of upper ocean flows for during times in the past. For the warm (T>5°C) surface ocean, density can be accurately reconstructed from calcite precipitated in equilibrium with seawater, as both of these properties increase with decreasing temperature and increasing salinity. Vertical density profiles can be reconstructed from the oxygen isotopic composition of benthic foraminifera. The net volume transport between two vertical density profiles can be calculated using the geostrophic method. Using benthic foraminifera from surface sediment samples from either side of the Florida Straits (Florida Keys and Little Bahama Bank), we reconstruct two vertical density profiles and calculate a volume transport of 32 Sv using this method. This agrees well with estimates from physical oceanographic methods of 30-32 Sv for the mean annual volume transport. We explore the sensitivity of this technique to various changes in the relationship between temperature and salinity as well as salinity and the oxygen isotopic composition of seawater.

Chemical composition of sediments and interstitial waters in the Gulf of California and Eastern Pacific

The book is devoted to study of diagenetic changes of organic matter and mineral part of sediments and interstitial waters of the Pacific Ocean due to physical-chemical and microbiological processes. Microbiological studies deal with different groups of bacteria. Regularities of quantitative distribution and the role of microorganisms in geochemical processes are under consideration. Geochemical studies highlight redox processes of the early stages of sediment diagenesis, alterations of interstitial waters, regularities of variations in chemical composition of iron-manganese nodules.