Observed storminess patterns and trends in the circum-Arctic coastal regime

Storm event statistics for the open-water season (June–October) were extracted from the terrestrial-based observational record throughout the circumpolar coastal regime over the period 1950–2000. The Barents/Norwegian and Kara regions exhibited an active spring/quiet summer signature typical of the mid-latitudes. The Kara and Laptev Sea regions had a strong June peak possibly associated with early sea ice breakup. The Chukchi sector exhibited large storm power values (defined as speed²*duration). Storm counts declined from 1950 to 1970, shifted rapidly from 1970 to 1974 to a level of greater mean activity and greater inter-annual variability, and declined after 1988.     

Palaeo-carbonate seep structures above an oil reservoir, Gryphon Field, Tertiary, North Sea

Petrographic and geochemical analyses performed on a North Sea core from the Gryphon Field reveal the presence of palaeo-degassing features surrounded by injected sandstones in the Eocene interval. The injected sandstones are oil-stained and poorly cemented by carbonate and quartz. ¹⁸O isotope analyses indicate that carbonate cementation occurred during shallow burial (likely less than about 300 m). Depleted ¹³C (around –30 V-PDB) carbonate cement suggests that bicarbonate was derived from the microbial oxidation of oil and gas. Late quartz overgrowths enclose oil present in the injected units. The tubular degassing conduits are composed of zoned cements and have ¹⁸O and ¹³C isotope values similar to the injected sandstones, indicating that oil and gas seepage induced the precipitation of authigenic carbonate in the shallow subsurface. Oil inclusions in inter- and intra-crystal cement sites in both injected sandstones and degassing conduits indicate that oil seepage was an ongoing feature at shallow burial. A proposed model involves oil and gas seepage and the formation of the degassing conduits, followed by a sand injection phase. It seems likely that oil and gas continued to leak towards the seabed by exploiting the network of permeable injected sandstones and the horizons of porous degassing features.     

New seismic data in the Mozambique Channel

This paper presents seismic reflection and refraction data from the Mozambique Channel, collected between 1971 and 1973. A deep sedimentary basin (up to 5 km of sediments) opens southwards to the Mozambique Basin, and is bounded to the east by the Davie Ridge and beyond by the marginal plateau of Malagasy. A continuous reflector (C), possibly of Cretaceous age, is identified between layers having seismic interval velocities of 2.4–2.8 km/s and 3.1–3.4 km/s. The deepest sediments have velocities of 4.5–4.9 km/s and overlie a layer with velocity 5.5 km/s, which may be volcanic in the north-east of the Channel.The crust occupying most of the Channel is probably pre-Cretaceous in age, and may be largely continental in nature. This is supported by subdued magnetic anomalies and the possibility of a continuous Karroo sedimentary section across the northern Channel. The oceanic crust of the Mozambique Basin may extend as far north as 24°S, into the western Channel only. The problem of the origin of the Mozambique Channel remains unresolved, although a long sedimentary history indicates that Malagasy may have separated from Mainland Africa prior to Karroo times. The Davie Ridge may possibly represent a relict strike-slip fault, which permitted movement along a north-south line.     

Particle-bound phosphorus along an urbanized coastal plain estuary

The distribution of particle-bound phosphorus in the suspended sediment of the Delaware Estuary was examined with a sequential chemical leaching technique. The phosphorus content of particles was highest in the tidal river (140–250 μmol g⁻¹) near major anthropogenic inputs. Despite this enrichment of river particles with phosphorus, suspended particles within the salinity gradient had a phosphorus content more similar to the world's average. Sequential chemical leaches revealed that particulate phosphorus was associated with organic matter, aluminum oxides, iron oxides, and apatite in all areas of the estuary. However, ‘excess’ particle-bound phosphorus in the tidal river was associated mainly with iron oxides (27%), aluminum oxides (23%), and organic matter (50%). Within the salinity gradient, particulate phosphorus associated with iron oxides, aluminum oxides, and apatite all decreased with increasing salinity. Estuarine mixing was simulated to determine whether the observed decreases in particle-bound phosphorus pools in field samples were due to release into solution. During simulated mixing, particulate phosphorus associated with iron and aluminum oxides decreased, but no change was observed in apatite-bound phosphorus. The results of the mixing study combined with the observed particle-bound phosphorus distributions suggest that phosphate concentrations along the Delaware Estuary may be partially ‘buffered’ by aluminum and iron oxide phases.     

Primary production and plankton stocks in the Pacific Ocean and their seasonal variation according to remote sensing and field observations

Data collected from 20 years of observations by the P. P. Shirshov Institute of Oceanology (about 250 comprehensive ecosystem stations) are summarized to evaluate the primary production and biomass of the principal groups of plankton in the Pacific Ocean. The stations were classified into geographical regions according to satellite determined criteria. The areas of these regions were evaluated according to CZCS data from 1978 to 1986. The total value of primary production was evaluated as 26·9 Gt C year⁻¹. Taking the “bottle effect” correction into account, this value may be as high as 45.6 Gt C year⁻¹. Total biomass values of phytoplankton (134 Mt C), bacteria (86 Mt C), protozoa (26 Mt C) and mesoplankton (184 Mt C) were also calculated. Seasonal variabilities of all these values were remarkably insignificant.     

Vertical and lateral transport of organic carbon and the carbon budget in Santa Monica Basin, California

The flux and compositions of solvent-extractable lipid fractions were measured in particulate matter collected periodically by moored sediment traps in the Santa Monica Basin from 1985–1988. The purpose was to assess the compositional changes during settling, the carbon dynamics in the basin and to estimate the impacts of energy-related by-products on the surface sediments. Sediment traps recorded consistently high lipid fluxes in the eastern slope relative to the central basin, reflecting elevated terrigenous carbon inputs possibly from land-based human activities. Generally, lipid fluxes decrease offshore but increase vertically with water depth below 500m, implying lateral transport of particles. The steep decline of flux in the top 500m of the water is related to the rapid decomposition and mineralization of the marine-derived cellular carbon compounds. Less than 5% of the marine lipid components reach the seabed. In contrast, preferential preservation of terrigenous lipid is clearly evident from the chemistry of deeper traps and surface sediments.The lateral transport of particles is reflected in the presence of higher plant-derived lignin phenols and sewage-derived coprostanol and epicoprostanol in the deep trap material as well as in surface sediment throughout the basin. Petroleum triterpanes characteristic of natural seepage also permeates through the entire basin. Based on the data collected from both the trap particulte matter and surface sediments, a carbon budget for the Santa Monica Basin has been constructed.     

Freezing as a method of sample preservation for the analysis of dissolved inorganic nutrients in seawater

It is often desirable or necessary to store collected seawater samples prior to analysis for dissolved inorganic nutrients. It is therefore important to establish preservation and storage techniques that will ensure sample integrity and will not alter the precision or accuracy of analysis. We have performed a series of experiments on the storage of nutrient samples collected at the oligotrophic North Pacific benchmark Station ALOHA, using both standard autoanalyses and low-level techniques. Our results reveal that for oligotrophic oceanic waters, the immediate freezing of an unfiltered water sample in a clean polyethylene bottle is a suitable preservation method. This procedure is simple, it avoids potentially contaminating sample manipulations and chemical additions, and it adequately preserves the concentrations of nitrate + nitrite, soluble reactive phosphate, and soluble reactive silicate within a single water sample.     

Nepheloid layers and internal waves over continental shelves and slopes

Theoretical and laboratory results indicate that bottom velocities within shoaling internal gravity waves intensify upslope approximately inversely proportional to the water depth. The elevated velocities (and bottom stresses) caused by shoaling and, possibly, breaking internal waves might explain the generation and maintenance of near-bottom nepheloid zones and attached turbid plumes that have been observed over certain continental shelves and slopes. This process is proposed as an explanation of zones of relatively low transmissibility that emanate from the upper continental slope near Newport submarine canyon off southern California.