Elemental abundance and water content at DSDP Leg 86 Holes

X-ray fluorescence analyses of 1143 samples from Site 576 (32°21.4'N, 164°16.5'E) and 539 samples from Site 578 (33°55.6'N, 151°37.7'E) for the elements Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Ba, and S show consistent trends from Si-rich surficial deposits to dark brown clays rich in Mn, Fe, P, and Ti in early Cenozoic sections. These data sets form the basis for a detailed paleogeochemical stratigraphy of North Pacific "red" clays.

Inorganic geochemistry, epoch and water content in sediments at DSDP Hole 91-595A

This chapter summarizes the principal results of drilling at Deep Sea Drilling Project (DSDP) Site 595, where the Ngendei Seismic Experiment and the emplacement of DARPA's Marine Seismic System (MSS) were carried out. Background and objectives for this work are presented in the introductory chapter to this volume. Interpretation of the seismic experiment and drilling results are presented in subsequent parts of this volume. The chapter also provides a detailed operational summary of the successful deployment of the MSS during Leg 91.

Inorganic geochemistry, epoch and water content in sediments at DSDP Site 91-596

Originally, we had planned to piston core at Site 595 in order to meet the sedimentologic and biostratigraphic objectives outlined in the introductory chapter. However, consultation with our colleagues, Thomas Jordan and John Orcutt on board Melville, indicated that coring near the ocean bottom seismometer (OBS) array around Hole 595B could alter the programmed signal to noise ratio above which teleseisms trigger recording in the OBSs. They requested that we core no closer than about 8 km from three OBSs nearest Hole 595B, and selected a target for us about that distance to the west. Since a new beacon was required at this distance, a new site number, 596, was designated. Briefly, we planned to obtain oriented hydraulic piston cores to the top of the cherts, then core through the cherts using the extended core barrel (XCB) to basement. With improved recovery, we hoped to reach the sediment/basalt contact, and thus obtain a reliable biostratigraphic determination of the basement age. We planned to obtain at least one core in basement, perhaps more, with time permitting. We planned no geophysical program for the hole.

Sediment geochemistry and water trace metal concentration in Potter Cove

Recent rapid climate warming at the western Antarctic Peninsula (WAP) results in elevated glacial melting, enhanced sedimentary run-off, increased turbidity and impact of ice-scouring in shallow coastal areas. Discharge of mineral suspension from volcanic bedrock ablation and chronic physical disturbance is expected to influence sessile filter feeders such as the Antarctic soft shell clam Laternula elliptica ( King and Broderip, 1832). We investigated effects of sedimentary run-off on the accumulation of trace metals, and together with physical disturbance, the cumulative effect on oxidative stress parameters in younger and older L. elliptica from two stations in Potter Cove (King George Island, Antarctica) which are distinctly impacted by turbidity and ice-scouring. Fe, Mn, Sr, V and Zn concentrations were slightly higher in sediments of the station receiving more sediment run-off, but not enriched in bivalves of this station. The only element that increased in bivalves experimentally exposed to sediment suspension for 28 days was Mn. Concentration of the waste accumulation biomarker lipofuscin in nervous tissue was higher in L. elliptica from the "exposed" compared to the "less exposed" site, whereas protein carbonyl levels in bivalve mantle tissue were higher at the less sediment impacted site. Tissue metal content and lipofuscin in nervous tissue were generally higher in older compared to younger individuals from both field stations. We conclude that elevated sediment ablation does not per se result in higher metal accumulation in L. elliptica. Instead of direct absorbance from sediment particles, metal accumulation in gills seems to indicate uptake of compounds dissolved in the water column, whereas metals in digestive gland appear to originate from enriched planktonic or detritic food. Accumulation of cellular waste products and potentially reactive metals over lifetime presumably alters L. elliptica physiological performance with age and may contribute to higher stress susceptibility in older animals.

Over-determined charbonate chemstry dataset from different kinds of manipulation (TA, DIC) and water types (natural and artificial seawater)

The growing field of ocean acidification research is concerned with the investigation of organism responses to increasing pCO2 values. One important approach in this context is culture work using seawater with adjusted CO2 levels. As aqueous pCO2 is difficult to measure directly in small-scale experiments, it is generally calculated from two other measured parameters of the carbonate system (often AT, CT or pH). Unfortunately, the overall uncertainties of measured and subsequently calculated values are often unknown. Especially under high pCO2, this can become a severe problem with respect to the interpretation of physiological and ecological data. In the few datasets from ocean acidification research where all three of these parameters were measured, pCO2 values calculated from AT and CT are typically about 30% lower (i.e. ~300 µatm at a target pCO2 of 1000 µatm) than those calculated from AT and pH or CT and pH. This study presents and discusses these discrepancies as well as likely consequences for the ocean acidification community. Until this problem is solved, one has to consider that calculated parameters of the carbonate system (e.g. pCO2, calcite saturation state) may not be comparable between studies, and that this may have important implications for the interpretation of CO2 perturbation experiments.

Hydrography and water chemistry of the open Mediterranean Sea

On a cruise from the eastern into western Mediterranean Sea in November/December 1978 a total of 126 samples were collected from 8 vertical profiles and 7 coastal stations for trace metal analysis. The sampling, processing and analysis was performed under strict "clean room" conditions. The concentration of the open-sea samples are close to oceanic results gathered under similar conditions. The grand averages from all profiles (± st. dev. of the individual samples) of 0.40 ± 0.16 µg/l Zn, 17.4 ± 7.4 ng/l Cd, 0.21 ± 0.07 µg/l Cu, 0.21 ± 0.13 µg/l Mn and 0.25 ± 0.09 µg/l Fe indicate that a "metal problem" does not exist in the open Mediterranean. A biologically mediated deplition in surface waters or correlation with nutrients have not been observed under the conditions established on this cruise. This is probably due top low primary production and seasonal advection processes prevailing in this sea. The data for manganese show generally higher values in the surface layer (0-75 m) than in deep waters. This could evidently proved in the nearshore profile indicating a terrigenous source for manganese.

Cation exchange capacity and water content of ODP sites from Nankai

Pore fluid chlorinity lower than seawater is often observed in accretionary wedges and one of the possible causes of pore water freshening is the smectite to illite reaction. This reaction occurs during diagenesis in the 80-150°C temperature range. Low chlorinity anomalies observed at the toe of accretionary wedges have thus been interpreted as evidence for lateral fluid migration from inner parts of the wedge and the seismogenic zone. However, temperature conditions in Nankai Trough are locally high enough for the smectite to illite transition to occur in situ. Cation exchange capacity is here used as a proxy for smectite content in the sediment and the amount of interlayer water released during the smectite to illite reaction represents in average 12 water molecules per cation charge. Water and chloride budget calculations show that there is enough smectite to explain the chlorinity anomalies by in situ reactions. The shape of the pore fluid chlorinity profiles can be explained if compaction is also taken into account in the model. Lateral flow is not needed. This argument, based solely on chloride concentration, does not imply that lateral flow is absent. However, previous estimations of lateral fluid fluxes, and of the duration of transient flow events along the de.collement, should be reconsidered.

Isotopic signatures and mercury content of arctic char and their prey, and water chemistry of 18 arctic Canadian lakes

Concentrations of mercury (Hg) have increased slowly in landlocked Arctic char over a 10- to 15-year period in the Arctic. Fluxes of Hg to sediments also show increases in most Arctic lakes. Correlation of Hg with trophic level (TL) was used to investigate and compare biomagnification of Hg in food webs from lakes in the Canadian Arctic sampled from 2002 to 2007. Concentrations of Hg (total Hg and methylmercury [MeHg]) in food webs were compared across longitudinal and latitudinal gradients in relation to d13C and d15N in periphyton, zooplankton, benthic invertebrates, and Arctic char of varying size-classes. Trophic magnification factors (TMFs) were calculated for the food web in each lake and related to available physical and chemical characteristics of the lakes. The relative content of MeHg increased with trophic level from 4.3 to 12.2% in periphyton, 41 to 79% in zooplankton, 59 to 72% in insects, and 74 to 100% in juvenile and adult char. The d13C signatures of adult char indicated coupling with benthic invertebrates. Cannibalism among char lengthened the food chain. Biomagnification was confirmed in all 18 lakes, with TMFs ranging from 3.5 ± 1.1 to 64.3 ± 0.8. Results indicate that TMFs and food chain length (FCL) are key factors in explaining interlake variability in biomagnification of [Hg] among different lakes.

Two-way traveltimes of internal layers and ice thickness between Dome C - Vostok - Dome A

Chinese scientists will start to drill a deep ice core at Kunlun station near Dome A in the near future. Recent work has predicted that Dome A is a location where ice older than 1 million years can be found. We model flow, temperature and the age of the ice by applying a three-dimensional, thermomechanically coupled full-Stokes model to a 70 × 70 km**2 domain around Kunlun station, using isotropic non-linear rheology and different prescribed anisotropic ice fabrics that vary the evolution from isotropic to single maximum at 1/3 or 2/3 depths. The variation in fabric is about as important as the uncertainties in geothermal heat flux in determining the vertical advection which in consequence controls both the basal temperature and the age profile. We find strongly variable basal ages across the domain since the ice varies greatly in thickness, and any basal melting effectively removes very old ice in the deepest parts of the subglacial valleys. Comparison with dated radar isochrones in the upper one third of the ice sheet cannot sufficiently constrain the age of the deeper ice, with uncertainties as large as 500 000 years in the basal age. We also assess basal age and thermal state sensitivities to geothermal heat flux and surface conditions. Despite expectations of modest changes in surface height over a glacial cycle at Dome A, even small variations in the evolution of surface conditions cause large variation in basal conditions, which is consistent with basal accretion features seen in radar surveys.