Ocean bottom friction study from numerical modelling of sea surface height and SEASAT-ALT data

Tidal dissipation at the ocean floor has long been regarded as an adquated explanation to the behaviour of lunar orbit and Earth's rotation, although the actual mechanism involved is yet a fascinating research subject to date. The most common way to evaluate the dissipation is to find the rate of work done per unit surface by the current on the sea floor (Munk and Mac Donald 1960, Lambeck 1975). The success of this approach rely on the knowledge of the frictional coefficient which links the frictional force at the ocean floor, either quadratically or linearly, with the current velocity. Not only is the frictional coefficient important in this context, a variety of storm surge and tidal modelling problems also require a similar dissipation meachanism (Heaps 1969, Grace 1930, Stock 1976 etc.). The University of Manitoba, Center for Precambrian Studies Publication No. 089     

The role of oxyradicals in intracellular proteolysis and toxicity in mussels

Studies were performed on the common mussel, M. edulis L., to determine whether copper (Cu) exposure can affect the extent to which digestive cell proteins are oxidised and whether such oxidative damage is mediated by free radicals. Three age groups of mussels were exposed for 6 ^-days to environmentally realistic concentrations of Cu and then digestive gland homogenates were examined for evidence of protein carbonyl formation. Significant increases in carbonyls relative to untreated control mussels were seen for the youngest (2–4 year-old) and oldest (≥ 10 year-old) mussels only after exposure for 6 days, followed by recovery from exposure for a further 6 days. Untreated mussels also showed an age-related difference in protein oxidation, with a significantly lower concentration in the youngest animals (2–4 year olds). Copper did not affect the levels of modified tryptophan or tyrosine residues or the extent of total lipid peroxidation in digestive gland homogenate. Significant depletion of total vitamin E (a-tocopherol) was seen only in young and medium-aged mussels following exposure for 6 days. The levels of protein carbonyl groups were increased in digestive cell cytosol and lighter lysosomes but not in heavier lysosomes or digestive gland microsomes following 5 days exposure to Cu. Dihydrohodamine-123 was converted to fluorescent rhodamine-123 following sequestration into digestive cell lysosomes. The results suggest a link between the lysosomal sequestration of copper, a concomitant increase in the production of oxyradicals and the potential for intracellular oxidative damage, as well as an increased capacity for oxidative damage in older animals.     

Enzymatic determination of glucose in marine environments: Improvement and note of caution

Microheterotrophic glucose uptake kinetics (V_{max and [K + Sn] value)} and uptake velocities (v) based on natural glucose concentrations (S_n) suggested that glucose concentrations in the Sapelo Island estuary were overestimated by published enzymatic techniques. Glucose oxidase treatment of water samples before glucose measurement yielded results as much as 50% lower than when this step was omitted. Thin layer chromatography shows that glucose must be separated from other carbohydrates (e.g., fructose) which interfere with the glucose assay.     

Merged GLORIA sidescan and Hydrosweep pseudo-sidescan: Processing and creation of digital mosaics

We have replaced the usual band of poor-quality data in the near-nadir region of our GLORIA long-range sidescan-sonar imagery with a shaded-relief image constructed from swath bathymetry data (collected simultaneously with GLORIA) which completely cover the nadir area. We have developed a technique to enhance these pseudo-sidescan images in order to mimic the neighbouring GLORIA backscatter intensities. As a result, the enhanced images greatly facilitate the geologic interpretation of the adjacent GLORIA data, and geologic features evident in the GLORIA data may be correlated with greater confidence across track. Features interpreted from the pseudo-sidescan may be extrapolated from the near-nadir region out into the GLORIA range where they may nt have been recognized otherwise, and therefore the pseudo-sidescan can be used to ground-truth GLORIA interpretations. Creation of digital sidescan mosaics utilized an approach not previously used for GLORIA data. Pixels were correctly placed in cartographic space and the time required to complete a final mosaic was significantly reduced. Computer software for digital mapping and mosaic creation is incorporated into the newly-developed Woods Hole Image Processing System (WHIPS) which can process both low- and high-frequency sidescan, and can interchange data with the Mini Image Processing System (MIPS) most commonly used for GLORIA processing. These techniques are tested by creating digital mosaics of merged GLORIA sidescan and Hydrosweep pseudo-sidescan data from the vicinity of the Juan Fernandez microplate along the East Pacific Rise (EPR).     

Determination of heavy metals in fresh and sea waters of S. Rossore Park (PISA)

A study was performed in the Tyrrhenian Sea in front of S. Rossore Park (Pisa) to ascertain the degree of Cu, Pb, Cd and Cr pollution and to investigate whether the rivers flowing into the sea may be considered potential sources of seawater contamination. Owing to the variability of such a system, the research, covering a one-year period, involved five surveys on 13 selected sampling stations and two surveys following the floats along the river Arno and its plume. The results refer to the total concentration of the above metals in the water phase after filtration. The content of Cu, Pb and Cd was always found to be higher than in the reference station (about 8 km offshore), generally reaching maximum values around the mouths of the rivers. Concentrations exceeding the minimal risk concentration were observed in the case of Cd. As for Cr, its concentration was always below the detection limit of the analytical method used. Rivers thus appear to be the main sources of coastal metal pollution.By the samplings carried out along the river Arno and its plume (involving 3–5 km from the mouth), it was found that the dilution model represents the concentration pattern for Cu and Pb fairly well over a large range of salinity.     

洋中脊断裂模式

断层是岩石圈中的准面状脆弱带，是地球的脆性外带，是地震和构造应变集中发生的区域。要想研究断层是如何形成的，首先要了解不断有断层形成的洋中脊地区，然后深入研究对热液矿床和化能自养生物群落产生重大影响的洋脊断层体系。     

‘NO’ as a conservative tracer in the Weddell Sea

The salinity maximum of the Warm Deep Water advecting into the Weddell Sea lies about 200 m below the temperature maximum and an NO minimum. The NO minimum is horizontally as well as vertically resolved on two sections towards the eastern and southern coast of the Weddell Sea, one towards Cap Norvegia, the other towards the Filchner Ice Shelf, whereas the temperature and salinity maxima are horizontally resolved on the former section only. Thus NO is a valuable complementary tool in studying the boundary current along the coast of the Weddell Sea. The NO signal indicates a non-continuity within the boundary current, as the minimum in the downstream section (less than 480 μmol kg⁻¹ ) is deeper than the upstream one ( more than 490 μmol kg⁻¹). The temperature maximum as well as the NO minimum descend from a depth of about 400 m in the Cap Norvegia section to about 600 m in the Filchner Ice Shelf section, the salinity maximum being correspondingly lowered. A plot of NO vs. salinity shows a continuous mixing line between Warm Deep Water and the freshest part of the Winter Water interval, thus essentially displaying Winter Water as itself lying on a mixing line. This indicates that Warm Deep Water is being advected well into the winter surface layer.     

Magmatic evolution of the Easter microplate-Crough Seamount region (South East Pacific)

The Easter microplate-Crough Seamount region located between 25° S–116° W and 25° S–122° W consists of a chain of seamounts forming isolated volcanoes and elongated (100–200 km in length) en echelon volcanic ridges oriented obliquely NE (N 065°), to the present day general spreading direction (N 100°) of the Pacific-Nazca plates. The extension of this seamount chain into the southwestern edge of the Easter microplate near 26°30 S–115° W was surveyed and sampled. The southern boundary including the Orongo fracture zone and other shallow ridges (< 2000 m high) bounding the Southwest Rift of the microplate consists of fault scarps where pillow lava, dolerite, and metabasalts are exposed. The degree of rock alternation inferred from palagonitization of glassy margins suggests that the volcanic ridges are as old as the shallow ridges bounding the Southwest Rift of the microplate. The volcanics found on the various structures west of the microplate consist of depleted (K/Ti < 0.1), transitional (K/Ti = 0.11–0.25) and enriched (K/Ti > 0.25) MORBs which are similar in composition to other more recent basalts from the Southwest and East Rifts spreading axes of the Easter microplate. Incompatible element ratios normalized to chondrite values [(Ce/Yb)_N = 1–2.5}, {(La/Sm)_N = 0.4–1.2} and {(Zr/Y)_N = 0.7–2.5} of the basalts are also similar to present day volcanism found in the Easter microplate. The volcanics from the Easter microplate-Crough region are unrelated to other known South Pacific intraplate magmatism (i.e. Society, Pitcairn, and Salas y Gomez Islands). Instead their range in incompatible element ratios is comparable to the submarine basalts from the recently investigated Ahu and Umu volcanic field (Easter hotspot) (Scientific Party SO80, 1993) and centered at about 80 km west of Easter Island. The oblique ridges and their associated seamounts are likely to represent ancient leaky transform faults created during the initial stage of the Easter microplate formation ( 5 Ma). It appears that volcanic activity on seamounts overlying the oblique volcanic ridges has continued during their westward drift from the microplate as shown by the presence of relatively fresh lava observed on one of these structures, namely the first Oblique Volcanic Ridge near 25° S–118° W at about 160 km west of the Easter microplate West Rift. Based on a reconstruction of the Easter microplate, it is suggested that the Crough seamount (< 800 m depth) was formed by earlier (7–10 Ma) hotspot magmatic activity which also created Easter Island.