ALBERT

Description: An abrupt lithofacies change between calcareous shale and noncalcareous shale occurs in strata deposited in the mid-Cretaceous Greenhorn Seaway in the southeastern corner of Montana. The facies were correlated lithostratigraphically using bentonites and calcarenites. The lithocorrelations were then refined using ammonites, foraminifera, and calcareous nannofossils. Twenty-five time slices were defined within the upper middle and lower upper Cenomanian strata. Biofacies analysis indicate that lithofacies changes record the boundary or oceanic front between two water masses with distinctly different paleoceanographic conditions. One water mass entered the seaway from the Arctic and the other from the Gulf of Mexico/Tethys. The microfauna and microflora permit interpretation of the environmental conditions in each water mass. At times when the front was near vertical, the two water masses were of the same density but of different temperatures and salinities.

Description: The holoplanktonic family Miraciidae (Copepoda, Harpacticoida) is revised and a key to the four monotypic genera presented. Amended diagnoses are given for Miracia Dana, Oculosetella Dahl and Macrosetella A. Scott, based on complete redescriptions of their respective type species M. efferata Dana, 1849, O. gracilis (Dana, 1849) and M. gracilis (Dana, 1847). A fourth genus Distioculus gen. nov. is proposed to accommodate Miracia minor T. Scott, 1894. The occurrence of two size-morphs of M. gracilis in the Red Sea is discussed, and reliable distribution records of the problematic O. gracilis are compiled. The first nauplius of M. gracilis is described in detail and changes in the structure of the antennule, P2 endopod and caudal ramus during copepodid development are illustrated. Phylogenetic analysis revealed that Miracia is closest to the miraciid ancestor and placed Oculosetella-Macrosetella at the terminal branch of the cladogram. Various aspects of miraciid biology are reviewed, including reproduction, postembryonic development, vertical and geographical distribution, bioluminescence, photoreception and their association with filamentous Cyanobacteria (Trichodesmium).

Description: The stomach contents of 723 Loligo vulgaris and 440 Loligo forbesi caught in the northwestern Spanish Atlantic waters have been examined. The diets of both species are described and compared. Loligo vulgaris shows 28 different types of prey belonging to four groups (Teleostei, Crustacea, Cephalopoda and Polychaeta) and Loligo forbesi 27 different types of prey belonging to three groups (Teleostei, Crustacea and Cephalopoda). Both species catch similar prey species but in different proportions. Cannibalism was observed in both species. Estimated prey sizes were smaller than squid sizes. No differences in feeding habits of males and females of both species were observed, but females seem to increase food intake during maturation. No significant changes were found in the diet of Loligo vulgaris within the size (DML) range studied (65–465 mm). Importance of cephalopods increased and importance of fish decreased in the diet of Loligo forbesi with growth (65–685 mm). Diet and food intake varied with seasons in both species. Diets of both squids were significantly different. Los contenidos estomacales de 723 Loligo vulgaris y 440 Loligo forbesi capturados en aguas de Galicia (Noroeste de España) fueron examinados. Se describe y compara la dieta de ambas especies. Se identificaron 28 tipos de presa diferentes en Loligo vulgaris que pertenecen a cuatro grupos (Teleostei, Crustacea, Cephalopoda y Polychaeta); y 27 tipos de presa en Loligo forbesi, pertenecientes a tres grupos (Teleostei, Crustacea y Cephalopoda). Ambas especies comen pres as similares, pero en proporciones diferentes. En ambas especies se observó canibalismo. La talla de las presas fue menor que la de los calamares. No se encontraron diferencias en la dieta entre machos y hembras en ambas especies, pero se observó que las hembras incrementan su tasa de ingestión durante la maduración. No se hallaron cambios significativos en la dieta de Loligo vulgaris en función de la talla (DML) dentro del rango de tamanos estudiado (65–465 mm). En Loligo forbesi, los cefalópodos aumentaron y los peces disminuyeron en importancia con la talla (65–685 mm DML). La dieta y la tasta de ingestión de ambas especies varió con la época del ano. Las dietas de ambas especies fueron significativemente diferentes entre sí.

Description: The zonal monsoon circulation south of India/Sri Lanka is a crucial link for the exchange between the northeastern and the northwestern Indian Ocean. The first direct measurements from moored stations and shipboard profiling on the seasonal and shorter‐period variability of this flow are presented here. Of the three moorings deployed from January 1991 to February 1992 along 80°30′E between 4°11′N and 5°39′N, the outer two were equipped with upward looking acoustic Doppler current profilers (ADCPs) at 260‐m depth. The moored and shipboard ADCP measurements revealed a very shallow structure of the near‐surface flow, which was mostly confined to the top 100 m and required extrapolation of moored current shears toward the surface for transport calculations. During the winter monsoon, the westward flowing Northeast Monsoon Current (NMC) carried a mean transport of about 12 Sv in early 1991 and 10 Sv in early 1992. During the summer monsoon, transports in the eastward Southwest Monsoon Current (SMC) were about 8 Sv for the region north of 3°45′N, but the current might have extended further south, to 2°N, which would increase the total SMC transport to about 15 Sv. The circulation during the summer was sometimes found to be more complicated, with the SMC occasionally being separated from the Sri Lankan coast by a band of westward flowing low‐salinity water originating in the Bay of Bengal. The annual‐mean flow past Sri Lanka was weakly westward with a transport of only 2–3 Sv. Using seasonal‐mean ship drift currents for surface values in the transport calculations yielded rather similar results to upward extrapolation of the moored profiles. The observations are compared with output of recent numerical models of the Indian Ocean circulation, which generally show the origin of the zonal flow past India/Sri Lanka to be at low latitudes and driven by the large‐scale tropical wind field. Superimposed on this zonal circulation is local communication along the coast between the Bay of Bengal and the Arabian Sea

Description: The effect of midlatitude and tropical internal wave variability on current profile measurements is investigated and quantified to yield practical error estimates. First, a data set of Pegasus current profiles from the tropical Atlantic (6°S to 6°N) is analyzed for their rms down/up differences, which are compared with predictions from Garrett‐Munk type internal wave theory and with statistics derived from current meter moorings in the same region. The agreement in terms of amplitudes and vertical distribution proves that most of those differences are due to internal waves and not instrumental errors. Nonetheless, this is the noise of the measurements, if low‐frequency motions are sought, and the errors can thus be quantified using the same internal wave theories. At midlatitudes the error variance is the usual 44(N/3 cph) cm2/s2 with some latitude dependence, and the effect of averaging in the vertical or summing several profiles (e.g., up and down) is estimated. The same is done for equatorial situations, where construction of a crude equatorial frequency spectrum for internal waves yields 77(N/3 cph)cm2/s2 for the error variance. Again, error reduction due to averaging is estimated.

Description: In laboratory investigations of the gas-phase OH initiated oxidation of dimethyl sulfide (DMS: CH3SCH3) at room temperature the formation of SO2, dimethyl sulfoxide (DMSO: CH3SOCH3), and OCS have been observed. A yield of 0.7±0.2% S was measured for OCS. These new results represent a hitherto unknown and quite considerable in situ atmospheric source of OCS. Based on the global DMS source strength as given in the literature and provided that the results from the laboratory study are valid under atmospheric conditions we estimate a contribution in the range 0.10 to 0.28 Tg (OCS) yr−1 from the gas-phase atmospheric photooxidation of DMS to the global OCS budget.

Description: The accuracy of the Darcy velocity, flux, and stream function computed from lowest-order, triangle-based, control volume and mixed finite element approximations to the two-dimensional pressure equation is considered. The control volume finite element method, similar to integrated finite difference methods and analogous to the interpolation of Galerkin finite element results over “control volumes,” is shown to yield a conservative velocity field and smooth streamlines. The streamlines and fluxes through the system computed with the control volume finite element approach are compared to those computed from the mixed finite element method, which approximates the pressure and velocity variables separately. It is shown that for systems with only moderate degrees of heterogeneity, the control volume finite element method is the more computationally efficient alternative; i.e., it provides more accurate flow results for a given number of unknowns. For more variable or discontinuous permeability fields, by contrast, such as sand/shale systems, the mixed finite element method is shown to approximate flow variables more accurately and more realistically than the control volume method with the same number of unknowns.

Description: Open-ocean deep convection is a littleunderstood process occurring in winter in remote areas under hostile observation conditions, for example, in the Labrador and Greenland Seas and near the Antarctic continent. Deep convection is a crucial link in the “Great Ocean Conveyor Belt” [Broecker, 1991], transforming poleward flowing warm surface waters through atmosphere-oceaninteraction into cold equatorward flowing water masses. Understanding its physics, interannual variations, and role in the global thermohaline circulation is an important objective of climate change research. In convection regions, drastic changes in water mass properties and distribution occur on scales of 10–100 km. These changes occur quickly and are difficult to observe with conventional oceanographic techniques. Apart from observing the development of the deep-mixed patch of homogeneous water itself, processes of interest are convective plumes on scales 〈1 km and vertical velocities of several cm s−1 [Schott et al., 1994] that quickly mix water masses vertically, and instability processes at the rim of the convection region that expedite horizontal exchanges of convected and background water masses [e.g., Gascard, 1978].

Description: The effect of dissolution from particulates into the supernatant solution in sediment trap sample cups has been measured for fatty acids. A mooring array with time series sediment traps was deployed in the northeast Atlantic Ocean (59°N, 21°W) for 14 months. Selected representative samples from the trap at 2200 m (poisoned with NaN3) were analyzed for total and free fatty acids in both the solution and particulate phase by means of gas chromatography‐mass spectrometry with an ion trap detector. The flux contribution of the dissolved total fatty acids (∑ DTFA) was found to be between 15 and 75% of the total flux (∑ TTFA, sum of the fluxes of total fatty acids in both particles and supernatants). Dissolved free fatty acids (∑ DFFA) represented 25–88% of the total flux of free fatty acids (∑ TFFA). Absolute concentrations of total and free fatty acids in both compartments are discussed in terms of the processes controlling the distribution between the two phases, for example, readsorption. Sample handling, poisoning, bacterial activity, and swimmers may also affect fatty acid distribution. Flux data (sum of particulate and dissolved fluxes) are presented for individual fatty acids. Also, the degree of dissolution of individual fatty acids is shown for one sample (dissolved fraction ranging between 16 and 98% of total flux).

Description: Biogenic particle fluxes from highly productive surface waters, boundary scavenging, and hydrothermal activity are the main factors influencing the deposition of radionuclides in the area of the Galapagos microplate, eastern Equatorial Pacific. In order to evaluate the importance of these three processes throughout the last 100 kyr, concentrations of the radionuclides 10Be, 230Th, and 231Pa, and of Mn and Fe were measured at high resolution in sediment samples from two gravity cores KLH 068 and KLH 093. High biological productivity in the surface waters overlying the investigated area has led to 10Be and 231Pa fluxes exceeding production during at least the last 30 kyr and probably the last 100 kyr. However, during periods of high productivity at the up welling centers off Peru and extension of the equatorial high-productivity zone, a relative loss of 10Be and 231Pa may have occurred in these sediment cores because of boundary scavenging. The effects of hydrothermal activity were investigated by comparing the 230Thex concentrations to the Mn/Fe ratios and by comparing the fluxes of 230Th and 10Be which exceed production. The results suggest an enhanced hydrothermal influence during isotope stages 4 and 5 and to a lesser extent during isotope stage 1 in core KLH 093. During isotope stages 2 and 3, the hydrothermal supply of Mn was deposited elsewhere, probably because of changes in current regime or deep water oxygenation. A strong increase of the Mn/Fe ratio at the beginning of climatic stage 1 which is not accompanied by an increase of the 230Thex concentration is interpreted to be an effect of Mn remobilization and reprecipitation in the sediment.

Description: Individual polychlorinated biphenyl (CB) congeners in adipose and whole blood tissues of a capacitor manufacture worker (occupational/accidental exposure) and of the general population were determined. Nondestructive sample cleanup and multidimensional gas chromatography-electron capture detection (MDGC-ECD) techniques were applied. Special attention was given to the toxicologically relevant congeners CB-77, CB-126, CB-169, CB-105, CB-114, CB-118, CB-156, CB-167, and CB-189 (IUPAC). Lipid-based tissue contents of sigma CBs were higher in the occupationally/accidentally exposed worker (adipose = 7,000 ng/g; whole blood = 11 ng/g) than in the general population (adipose = 300 ng/g; whole blood = 1.9 ng/g). Among the non-ortho Cl CBs, CB-77 was below detection limit (〈 1.0 pg/g). The contents of CB-126 for the capacitor manufacture worker were 2,000 and 3 pg/g, and in the general population were 100 and 2 pg/g for adipose and whole blood, respectively. The corresponding data for CB-169 were 3,500 and 4 for adipose and whole blood, respectively, in the exposed worker, and 40 and 2 for adipose and whole blood, respectively, in the general population. Congeners with highest contents were CB-153, CB-138, CB-180, CB-170, and CB-187. These congeners possess chlorine substitution patterns, making them resistant to metabolism. X/153 ratios suggest that both PB and 3-MC type cytochrome P-450 enzymes were induced in the exposed worker, as well as in the general population.

Description: The distribution of living (rose bengal stained) deep-sea benthic foraminifera was determined in the upper 20 cm of sediments of eight Soutar box cores taken from two depth transects (510-4515 m) in the thermospheric (〉 10°C) Sulu Sea. Despite the uniformity of bottom water temperatures, salinities, and dissolved oxygen levels below 1000 m, significant faunal differences exist at different depths in the low-oxygen (∼1.25 mL/L below 1000 m) basin. The shallowest site (510 m) is dominated (〉 10% of the calcareous fauna) by Cibicidoides, Uvigerina, (〉 150 µm) and Bolivina (〉 63 µm), while Siphonina is codominant with Cibicidoides and Uvigerina in the 1005-m core. The 2000-m cores are dominated by Cibicidoides, Gyroidinoides, and Oridorsalis, while Cibicidoides bradyi and Oridorsalis umbonatus dominate the 3000- and 4000-m cores. Infaunal assemblages of Valvulineria mexicana are found in the sediments of the 4515-m core. Relatively low bottom water oxygen values do not necessarily yield "typical low-oxygen taxa" such as Bolivina, Uvigerina, Chilostomella, Bulimina, and Globobulimina. Changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments. An examination of the vertical distributions of foraminiferal assemblages from the 〉 63-µm and 〉 150-µm fractions reveals that taxa have microhabitat preferences similar to those observed in other regions. Taxa found in the upper 0- to 1-cm interval (epifaunal) include Cibicidoides wuellerstorfi and Hoeglundina elegans, while taxa such as Chilostomella and Globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences. Cibicidoides bradyi and O. umbonatus live in sediment depths from 0- to 4-cm and have transitional preferences with both epifaunal and infaunal occurrences. Intrageneric differences in test morphologies, including pore distribution, rounded peripheries, and variable spire height, are observed in Cibicidoides and Gyroidinoides and are suggested to be related to microhabitat preferences. Vertical distributions of a number of taxa found in both the 63- to 150-µm and 〉 150-µm fractions are similar, suggesting that juveniles and adults live under similar microhabitat conditions. Ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies.

Description: Sources of near-surface oceanic variability in the central North Atlantic are identified from a combined analysis of climatology, surface drifter, and Geosat altimeter data as well as eddy-resolving math formula and math formula Community Modeling Effort North Atlantic model results. Both observational and numerical methods give a consistent picture of the concentration of mesoscale variability along the mean zonal flow bands. Three areas of high eddy energy can be found in all observational data sets: the North Equatorial Current, the North Atlantic Current, and the Azores Current. With increasing horizontal resolution the numerical models give a more realistic representation of the variability in the first two regimes, while no improvement is found with respect to the Azores Current Frontal Zone. Examination of the upper ocean hydrographic structure indicates baroclinic instability to be the main mechanism of eddy generation and suggests that the model deficiencies in the Azores Current area are related to deficiencies in the mean hydrographic fields. A linear instability analysis of the numerical model output reveals that instability based on the velocity shear between the mixed layer and the interior is also important for the generation of the mid-ocean variability, indicating a potential role of the mixed layer representation for the model. The math formula model successfully simulates the northward decrease of eddy length scales observed in the altimeter data, which follow a linear relationship with the first baroclinic Rossby radius. An analysis of the eddy-mean flow interaction terms and the energy budget indicates a release of mean potential energy by downgradient fluxes of heat in the main frontal zones. At the same time the North Atlantic Current is found to be supported by convergent eddy fluxes of zonal momentum.

Description: During three measurement campaigns on the Baltic and North Seas, atmospheric and dissolved methane was determined with an automated gas chromatographic system. Area-weighted mean saturation values in the sea surface waters were 113 ± 5% and 395 ± 82% (Baltic Sea, February and July 1992) and 126 ± 8% (south central North Sea, September 1992). On the bases of our data and a compilation of literature data the global oceanic emissions of methane were reassessed by introducing a concept of regional gas transfer coefficients. Our estimates computed with two different air-sea exchange models lie in the range of 11-18 Tg CH4 yr-1. Despite the fact that shelf areas and estuaries only represent a small part of the world's ocean they contribute about 75% to the global oceanic emissions. We applied a simple, coupled, three-layer model to numerically simulate the time dependent variation of the oceanic flux to the atmosphere. The model calculations indicate that even with increasing tropospheric methane concentration, the ocean will remain a source of atmospheric methane.

Description: Biogenic particle fluxes from highly productive surface waters, boundary scavenging, and hydrothermal activity are the main factors influencing the deposition of radionuclides in the area of the Galapagos microplate, eastern Equatorial Pacific. In order to evaluate the importance of these three processes throughout the last 100 kyr, concentrations of the radionuclides 10Be, 230Th, and 231Pa, and of Mn and Fe were measured at high resolution in sediment samples from two gravity cores KLH 068 and KLH 093. High biological productivity in the surface waters overlying the investigated area has led to 10Be and 231Pa fluxes exceeding production during at least the last 30 kyr and probably the last 100 kyr. However, during periods of high productivity at the up welling centers off Peru and extension of the equatorial high-productivity zone, a relative loss of 10Be and 231Pa may have occurred in these sediment cores because of boundary scavenging. The effects of hydrothermal activity were investigated by comparing the 230Thex concentrations to the Mn/Fe ratios and by comparing the fluxes of 230Th and 10Be which exceed production. The results suggest an enhanced hydrothermal influence during isotope stages 4 and 5 and to a lesser extent during isotope stage 1 in core KLH 093. During isotope stages 2 and 3, the hydrothermal supply of Mn was deposited elsewhere, probably because of changes in current regime or deep water oxygenation. A strong increase of the Mn/Fe ratio at the beginning of climatic stage 1 which is not accompanied by an increase of the 230Thex concentration is interpreted to be an effect of Mn remobilization and reprecipitation in the sediment.

Description: The current status of the Sverdrup theory for the initiation of plankton blooms is examined. A prescription is given for the computation of the Sverdrup critical depth, using recently-published algorithms for mixed-layer primary production and a generalised loss term. Using no further information, the intrinsic rate of increase of phytoplankton biomass in the mixed layer can also be found. This rate, compared against the local frequency of storm occurrence, provides an alternative criterion for the initiation of blooms. The Eulerian (bulk property) methods used to derive these results are contrasted with the Lagrangian Ensemble method. The Lagrangian approach provides one avenue to the elaboration of the Sverdrup criterion to include the effect of processes with characteristic timescales small compared to one day. The incidence of blooms in the apparent absence of vertical stratification is reviewed: it is concluded that these observations do not undermine the basic logic of the Sverdrup theory. However, they do provoke interest in a re-examination of the feedbacks between the physical and biological dynamics in the mixed layer: an example is given. Finally, suggestions are made for further work in this subject area.

Description: The main water masses in the northern Barents Sea are surface water, Arctic water, transformed Atlantic water, and cold bottom water. Using summer data from 1981 and 1982, the formation, distribution, modification and circulation of these water masses are discussed. Recent estimates show that about 2 Sv of Atlantic water enters the Barents Sea by the North Cape Current, balanced by a similar outflow through the strait between Novaya Zemlya and Frans Josef Land. Passing through the Barents Sea, Atlantic-derived water is modified by interaction with other water masses as well as with the atmosphere, and the end products are believed to be important contributors to the hydrographic structure of the Arctic Ocean.

Description: A coupled ocean-atmosphere GCM is being developed for use in seasonal forecasting. As part of the development work, a number of experiments have been made to explore some of the sensitivities of the coupled model system. The overall heat balance of the tropics is found to be very sensitive to convective cloud cover. Adjusting the cloud parameterization to produce stable behaviour of the coupled model also leads to better agreement between model radiative fluxes and satellite data. A further sensitivity is seen to changes in low-level marine stratus, which is under-represented in the initial model experiments. An increase in this cloud in the coupled model produces a small improvement in both the global mean state and the phase of the east Pacific annual cycle. The computational expense of investigating such small changes is emphasized. An indication of model sensitivity to surface albedo is also presented. The sensitivity of the coupled GCM to initial conditions is investigated. The model is very sensitive, with tiny perturbations able to determine El Niño or non-El Niño conditions just six months later. This large sensitivity may be related to the relatively weak amplitude of the model ENSO cycle.

Description: ECHO is a new global coupled ocean-atmosphere general circulation model (GCM), consisting of the Hamburg version of the European Centre atmospheric GCM (ECHAM) and the Hamburg Primitive Equation ocean GCM (HOPE). We performed a 20-year integration with ECHO. Climate drift is significant, but typical annual mean errors in sea surface temperature (SST) do not exceed 2° in the open oceans. Near the boundaries, however, SST errors are considerably larger. The coupled model simulates an irregular ENSO cycle in the tropical Pacific, with spatial patterns similar to those observed. The variability, however, is somewhat weaker relative to observations. ECHO also simulates significant interannual variability in mid-latitudes. Consistent with observations, variability over the North Pacific can be partly attributed to remote forcing from the tropics. In contrast, the interannual variability over the North Atlantic appears to be generated locally.

Description: Satellite-derived (Geosat altimetry) sea surface height anomalies for the period November 1986 to September 1989 were investigated in order to extract the dominant modes of climate variability in the tropical Pacific. We applied the technique of principal oscillation patterns and computed associated wind stress patterns for each mode. Four modes were identified. The first mode has a time scale of about 3 months and can be identified with the first baroclinic equatorial Kelvin wave mode, which is excited by intraseasonal wind variations over the western equatorial Pacific. The second mode has a time scale of about 6 months and describes the semiannual cycle in the tropical Pacific sea level. Equatorial wave dynamics appears to be crucial for this mode also. The third mode is the annual cycle which shows evidence of off-equatorial Rossby wave propagation. The fourth mode is associated with the El Niño/Southern Oscillation (ENSO) phenomenon. The ENSO mode is found to be consistent with the “delayed action oscillator” scenario.

Description: From March 11 to April 5,1994, the German research vessel Sonne mapped the largely uncharted offshore areas of the Tabarto-Feni island chain in the New Ireland Basin of Papua, New Guinea. The Epithermal Deposits Southwestern Pacific Ocean (EDISON) cruise was organized as part of a multidisciplinary program to study the regional tectonic setting of the Tabar-to-Feni chain, to document recent submarine volcanism, and to investigate seafloor hydrothermal activity on the submerged flanks of the volcanos. The New Ireland Basin occupies a forearcposition with respect to the formerly active Manus-Kilinailau arc-trench system and hosts a series of Pliocene to recent alkaline volcanos that are built on rifted Miocene sedimentary basement. Several of the volcanos have large, high-level porphyry stocks, and several have active geothermal systems, including gold-depositing hot springs and the giant Ladolam gold deposit on the island of Lihir.

Description: We report on a Pb‐Nd‐Sr isotope and rare earth study of Mid‐Atlantic Ridge (MAR) basalt glasses collected across the equatorial fracture zones from 7°S to 5°N (65 stations). The 1600‐km‐long profile reveals two mixing zones in the mantle that are isotopically distinct but cover the same range of (La/Sm)n ratios (0.3–2), with a gradational boundary between the Romanche and the Chain fracture zones. The potential mantle temperature profile inferred from Na2O content is also quite distinct. The north zone is dominated by a major, La/Sm and HIMU type Pb isotope anomaly centered at 1.7°N±300 km, which is flanked by two zones mildly radiogenic in Pb but depleted in light REE. A kinematic and evolutionary model describing the dispersion and interaction of the Sierra Leone plume with the asthenosphere and the MAR in the last 75 m.y. is proposed for this zone, which includes St. Paul and St. Peter's Rocks. In contrast, over the south zone the isotope/geochemical profiles are well correlated at all length scales and opposite in sign from the inferred potential mantle temperature profile and mean percent fusion. Broad negative gradients are observed between the Romanche and the Charcot fracture zones, superimposed by spikelike anomalies at the intersection with the eastern part of the Romanche and Chain transform faults, where cold plate edge effects prevail. The heterogeneous mantle model of Sleep [1984] and Langmuir and Bender [1984] is applicable to this zone, that is the volatile and radiogenic Pb‐rich lumps are preferentially melted during mantle decompression and passively sampled. The lumps may reflect the early dispersion of the St. Helena or Ascension mantle plumes under a thick lithosphere, followed by redistribution due to intense shearing, continental lithosphere delamination, and secondary mantle convection. The presence of a depleted asthenosphere unpolluted by plumes along the 400‐km‐long MAR segment between the Charcot and Ascension fracture zones is also apparent in the data.

Description: This paper describes the evolution of the former Tethys ocean in terms of successive positions of the involved plates, their boundaries, and the oceanic and continental elements they bore. Most of the past positions for the major continents are obtained from published data on the kinematics of the Atlantic and Indian oceans. As they do not cover the complete time span and area under study, additional solutions for the missing parts are proposed on the basis of paleomagnetic and geologic data. A revised reconstruction of Eastern Gondwana and a reappraisal of the early history of the Indian ocean is presented, as well as a discussion of the Pangea megashear concept which applies to the relations between Gondawa and Laurussia during latest Palaeozoic to Mid-Triassic times. Past positions of continental blocks, basins and associated plate boundaries within the now disappeared Tethys ocean, are determined through the kinematic inversion of the Alpine chains interpreted in terms of break-up, oceanic spreading and drift, subduction and collision. A quantitative solution is obtained by associating Eulerian rotation parameters to any relative displacement, computing their combination, then adjusting until a complete coherency through time and space is obtained. Our method puts emphasis on the former positions of the plate boundaries in the Tethys, and stresses the drastically different organisation of Tethys west and east of a fundamental triple junction located in its Mediterranean part. A symmetric Atlantic part of Tethys, governed by a mid-ocean diverging boundary, was thus linked eastwards to an asymmetric “Transit” part of Tethys where southern diverging boundaries and northern converging boundaries defined a Transit plate (or group of plates). Besides several reorganisations through southward shift of these boundaries, the successive (or coeval) transit plates systematically exhibited the same north-south asymmetry responsible for the northward migration of the various continental blocks they carried, which were successively detached from Gondwana to become accreted to Eurasia. The transit process, while an essential element of the Tethyan tectonic pattern, was not restricted to lifetime of Tethys, as it is still active nowadays and was already active during the Palaeozoic. Nevertheless, its association with the Atlantic Tethys diverging boundary is typical for the lifetime of Tethys, both constituting a “Tethys plate pattern”, in opposition to the present-day and to Hercynian “Anti-Tethys plate pattern” where a converging boundary is and was associated with the transit plate system. Two pre-eminent tectonic events, the Late Triassic switchover from the Anti-Tethys pattern to the Tethys pattern, and the Late Cretaceous switchover back to the Anti-Tethys pattern, decided birth and death of the Tethys ocean.

Description: Early Tertiary lithospheric breakup between Eurasia and Greenland was accompanied by a transient (∼3 m.y.) igneous event emplacing both the onshore flood basalts of the North Atlantic Volcanic Province (NAVP) and huge extrusive complexes along the continent‐ocean transition on the rifted continental margins. Seismic data show that volcanic margins extend 〉2600 km along the early Eocene plate boundary, in places underlain by high‐velocity (7.2–7.7 km/s) lower crustal bodies. Quantitative calculations of NAVP dimensions, considered minimum estimates, reveal an areal extent of 1.3×106 km2 and a volume of flood basalts of 1.8×106 km3, yielding a mean eruption rate of 0.6 km3/yr or 2.4 km3/yr if two‐thirds of the basalts were emplaced within 0.5 m.y. The total crustal volume is 6.6×106 km3, resulting in a mean crustal accretion rate of 2.2 km3/yr. Thus NAVP ranks among the world's larger igneous provinces if the volcanic margins are considered. The velocity structure of the expanded crust seaward of the continent‐ocean boundary differs from standard oceanic and continental crustal models. Based on seismic velocities this “volcanic margin” crust can be divided into three units of which the upper unit corresponds to basaltic extrusives. The regionally consistent velocity structure and geometry of the crustal units suggest that the expanded crust, including the high‐velocity lower crust which extends some distance landward of the continent‐ocean boundary, was emplaced during and subsequent to breakup. The volcanic margin crust was formed by excess melting within a wide zone of asthenospheric upwelling, probably reflecting the interaction of a mantle plume and a lithosphere already extending.

Description: Reflection seismic and borehole geophysical data place important constraints on the subsurface geometry of the Sudbury Structure, which is the site of the world's largest Ni‐Cu camp. Seismic reflections can be traced from outcrop within the Sudbury North Range to about 4.5 km depth beneath the center of the Sudbury Basin, where the layer thickens abruptly from 1 to 3 km. Further south the North Range norite can be followed to about 10 km depth beneath the South Range. Borehole studies show systematic variations of p‐ and s‐wave velocity, Poisson's ratio and density within the Igneous Complex. Quartz‐rich granophyre is distinguished from the norite and footwall rocks by relatively low Poisson's ratios (0.20–0.23 versus 0.23–0.25). These changes in physical rock properties define an important subdivision of the Igneous Complex, compatible with a simple model involving differentiation of melted crustal rock into dominantly felsic and mafic components. This study documents the importance of interlayering to the seismic reflection response of the crystalline crust.

Description: Results from borehole geophysical logs, full waveform sonic logs, VSP and laboratory core sample measurements indicate that lithologic variations within the Sudbury Igneous Complex (SIC) and footwall rocks are the primary cause of reflections observed regionally on the multi‐channel seismic reflection profiles. The effects of macroscopic fracturing and low‐grade alteration on the seismic response are only important to a depth of ∼ 320 m. The major lithologic units of the SIC and footwall rocks in the North Range of the Sudbury structure have contrasting physical properties: Felsic norite and quartz‐gabbro have higher Vp (∼ 6300 m/s) than granophyre (∼ 6000 m/s) due to their higher pyroxene content and the presence of quartz rather than calcic plagioclase in the granophyre. Velocities are higher (Vp ∼ 6500 m/s) within the brecciated footwall rocks due to an overall increase in mafic mineral content. The contrasting velocities and densities of these units imply that the granophyre/quartz‐gabbro contact and the SIC/footwall transition can be mapped regionally using seismic reflection methods. Subunits within these units are also highly reflective, consistent with the nature of the seismic data, but are likely discontinuous laterally.

Description: Site fidelity and dispersal of juvenile and sexually mature adults was investigated at the largest southern African gannetry on Bird Island, Algoa Bay, where a minimum of 65000 airs occupy approximatel 2 ha at a mean density of 2,85 nests per m2. Based on 512 ring recoveries and live retraps of known-aged birds of this colony, immature and non-breeding adult gannets dispersed widely along the coasts o Africa, reaching Maputo Bay (southern Mozambique) on the eastern side of the continent and the Namibian Skeleton Coast on the western side. Very few birds flew farther. There were conspicuously few ring recoveries at 400–500 km straight-line distance east from Bird Island, corresponding with the Pondoland coast in Transkei. A similar drop was observed in the west for the Tsitsikamma coast and the stretch of coast from Cape St. Blaize to Cape Infanta. In these regions reporting by members of the public is presumed to be low. either because the rocky coast is inaccessible or because of socioeconomic reasons. The geographical spread of the ring recoveries suggested a possible range contraction of the species between the 1950's and the period 1978–1993 but the nature of the data prevented a test of this hypothesis. No evidence was found that gannets from Bird Island breed or roost at other southern African colonies as a matter of habit. On the contrary, all survivors of post-fledgling dispersal eventually returned to their native colony, where they exhibited pronounced fidelity to the site where they hatched from the egg. Based on multiple retraps of 862 known-age individuals, 71.7 % of young adults took over vacant sites in the immediate vicinity of their original nest, 8,1% moved once but were faithful to their new site and in 20,2% of all cases faithfulness to the original site could not be shown. Moreover, in subsequent years edge birds did not vacate their sites to move towards the center, refuting the hypothesis that fringes are physically inferior breeding sites.

Description: The Romanche transform offsets the Mid‐Atlantic Ridge (MAR) axis by about 950 km in the equatorial Atlantic. Multibeam and high‐resolution multichannel seismic reflection surveys as well as rock sampling were carried out on the eastern part of the transform with the R/V Akademik Strakhov as part of the Russian‐Italian Mid‐Atlantic Ridge Project (PRIMAR). Morphobathymetric data show the existence on the northern side of the transform of a major 800‐km‐long aseismic valley oriented 10° to 15° from the active valley; it disappears about 150 km from the western MAR segment. The aseismic valley marks probably the former location of the Romanche transform (“PaleoRomanche”) that was active up to roughly 8–10 Ma, when the transform boundary migrated to its present position. A temporary microplate developed during the migration and reorientation of the transform. This microplate changed its sense of motion as it was transferred from the South American to the African plate. A prominent transverse ridge extends for several hundred kilometers parallel to the transform on its northern side, reaching its shallowest part (shallower by over 4 km than the predicted thermal contraction depth) in a zone opposite the eastern MAR axis/transform intersection (RTI). Flat‐top peaks on the summit of the transverse ridge are capped by acoustically transparent, weakly stratified, shallow water platfonn/lagunal/reef limestones. This limestone unit is a few hundred meters thick and overlies igneous basement. Evaluation of the seismic reflection data as well as study of samples of carbonates, ventifact basaltic pebbles and gabbroic, peridotitic and basaltic rocks recovered at different sites on the transverse ridge, suggest that (1) the summit of the transverse ridge was above sea level at and before about 5 Ma; (2) the transverse ridge subsided since then at an average rate 1 order of magnitude faster than the predicted thermal contraction rate; its summit was flattened by erosion at sea level during subsidence; (3) the transverse ridge is an uplifted sliver of lithosphere and not a volcanic constructional feature; and (4) transtensional and transpressional tectonics have affected the transverse ridge. Hypotheses on the origin of the Romanche transverse ridge include (1) lateral heat conduction across the RTI; (2) shear heating; (3) lithospheric flexure due to thermal stresses in the cooling lithosphere; (4) viscoelastic deformation of the lithosphere; (5) hydration/dehydration of mantle peridotites; and (6) longitudinal flow of melt and igneous activity across the RTI. These processes cannot by themselves explain the transverse ridge, although some of them could contribute to its formation to a small extent. Vertical tectonics due to transpressional and transtensional events related to a nonstraight transform boundary and to regional changes in ridge/transform geometry is probably the primary process that gave rise to the uplift of the transverse ridge and to its recent subsidence. Uplift may have been caused primarily by thrust faulting induced by transpression related to the oblique impact of the lithospheric plate against the former (PaleoRomanche) and the younger transform boundaries, before and during the transition to the present boundary. After migration of the transform boundary to its present position, transpression was replaced by transtension and by subsidence of the transverse ridge. An aseismic axial rift valley impacting against the transform valley about 80 km west of the present RTI suggests eastward ridge jumping that probably followed transform migration. Localized transtension or transpression due to bends in the orientation of the transform may have caused intense although localized vertical movements, such as those that formed an ultradeep (〉7800 m) pull‐apart basin along the transform valley.

Description: This article introduces a resampling procedure called the stationary bootstrap as a means of calculating standard errors of estimators and constructing confidence regions for parameters based on weakly dependent stationary observations. Previously, a technique based on resampling blocks of consecutive observations was introduced to construct confidence intervals for a parameter of the m-dimensional joint distribution of m consecutive observations, where m is fixed. This procedure has been generalized by constructing a “blocks of blocks” resampling scheme that yields asymptotically valid procedures even for a multivariate parameter of the whole (i.e., infinite-dimensional) joint distribution of the stationary sequence of observations. These methods share the construction of resampling blocks of observations to form a pseudo-time series, so that the statistic of interest may be recalculated based on the resampled data set. But in the context of applying this method to stationary data, it is natural to require the resampled pseudo-time series to be stationary (conditional on the original data) as well. Although the aforementioned procedures lack this property, the stationary procedure developed here is indeed stationary and possesses other desirable properties. The stationary procedure is based on resampling blocks of random length, where the length of each block has a geometric distribution. In this article, fundamental consistency and weak convergence properties of the stationary resampling scheme are developed.

Description: A large, discrete aggregation of squid was sampled at short intervals by means of jigging, midwater trawling and purse-seining. Differences among basic parameters of the population (e.g. length frequency) indicate that jigging is a more selective, and therefore biased, method of sampling than midwater trwaling or purse-seining. This has important consequences for stock assessments that take commercial catches into account. The selectivity curve indicates that squid of mantle lenghts (ML) 28-33cm are over-represented (in terms of the situation in the population) in fisheries conducted by jigging and that squid 〈26 and 〉34cm ML are under-represented if purse-seine results are considered to be representative of the population.

Description: The occurrence and distribution of dinoflagellate resting cysts in Recent sediments was investigated at 9 locations in Kiel Bight, Baltic Sea. The assemblage comprised 25 known cyst species and 4 unknown cyst types and is characterized by the dominance of Protoperidinium cf. divergens with a maximal abundance of 1695 living cysts/cm3 in the upper half centimeter. Cysts of the potentially toxic dinoflagellates of the Alexandrium excavatum/tamarense group and A. minutum were scarce. Micro-reticulate resting cysts of the toxic, unarmoured Gymnodinium catenatum, whose motile cell has not been recorded in Northern European waters, are reported for the first time from Recent sediments of the Baltic Sea. In the top 2-cm of sediment up to 1200 living dinoflagellate cysts/cm3 were found and the following trends were noted: Cysts were primarily associated with sediments dominated by mud, sandy stations exhibited the lowest cyst abundance. Highest cyst concentrations were found at the deepest stations and the small-scale vertical distribution ofcysts usually exhibited maximum concentrations below the sediment surface. Empty cysts constituted 16.5–64.0% of total cyst abundance. These results suggest that the spatial distribution of several cyst species is controlled by water circulation patterns. The wide distribution ofliving and empty cysts of Peridinium dalei, Protoperidinium denticulatum and P. punctulatum and corresponding germination experiments suggest that the motile forms, which have not previously been recorded in the area, are common members of the plankton community in the western Baltic Sea. The cysts of Gonyaulax polyedra, P. dalei and Protoceratium reticulatum exhibited a reduced length of processes compared to individuals from marine habitats.

Description: In situ caging experiments showed that both littorinid snails and gammarid amphipods exerted minimal effects on the suite of algae comprising the canopy of littoral fringe tide pools dominated by Fucus distichus. In the absence of grazers, the Fucus canopy was dramatically reduced by fatal endophyte infections. Among the 10dependent variables making up the algal species and forms at the substratum level below the canopy, 3 were highly affected by grazing. The germlings of F. distiehus were greatly reduced by littorinids. Gamrnarids also reduced germling cover, but were less effective. In addition, the two grazer guilds interactively reduced the cover of algae belonging to the Uniseriate functional form at the substratum level. Sheet/Tube form algae were reduced in cover only by littorinids. Other forms, including calcareous crusts, thalli of Chondrus crispus and 3 Cladophora species were unaffected by grazing. There was no indication of food resource partitioning between littorinids and gammarids.

Description: Optimum multiparameter (OMP) analysis is used to analyze mixing in the central water boundary of the tropical North Atlantic Ocean. Diapycnal mixing is found to be prevalent in the frontal region. OMP analysis shows that the mixing is unidirectional (South Atlantic Central Water is always mixed upward into North Atlantic Central Water) but cannot identify the process responsible for the observed diapycnal mixing. A histogram of stability ratios Rρ for all mixing lines shows Rρ values between unity and the value found in the parent water masses. It is suggested that this may indicate competition between isopycnal mixing and double diffusion. Double diffusive fluxes are likely to make a recognizable and significant contribution to diapycnal mixing between the Central Waters.

Description: The purpose of this special section in Paleoceanography is to present interdisciplinary approaches for contributing to the reconstruction of ocean circulation and its response to climate changes. A high-priority objective for understanding the causes and mechanisms of climate change is the monitoring of past ocean circulation and oceanic heat and nutrient transport. Lehman and Keigwin [1992] have shown that cooling, for example, during the younger Dryas event, may have culminated in a cessation of the oceans conveyor circulation. The cooling in the North Atlantic was apparently the result of reduced northward heat transport in the upper water masses of the North Atlantic conveyor belt. In contrast, intervals with a strong surface and deepwater circulation were marked by a high northward heat transport. For the understanding of the causes and the timing of such rapid,highfrequency events, marine records of high deposition ratecores are needed. These cores should provide evidence for changes in abyssal circulation and heat transport, as well as arecord of surface and deepwater characteristics. The sediment drifts of the North Atlantic and in other ocean basins are one of the major targets for the recovery of sediments with high deposition rates (〉10 cm/kyr) and for reconstructing the role of both intermediate and deepwater production in the conveyor belt, that is drawing low-latitude heat northward. We stress the need for international programs targeting high deposition rate areas on sediment drifts and sediment waves in order to understand (1) the evolution of the conveyor belt and (2) its dynamics and variability. The North Atlantic, where sediment drifts are concentrated, will provide ideal study areas with time resolutions comparable to those of ice core records but with records linked directly to the record of changing bottom water flow. Therefore one can address the changes in circulation, heat and carbon budget on high and ultrahigh resolution records.

Description: Exploratory measurements of a suite of anthropogenic halocarbon compounds (CCl4, CCl2FCClF2 (CFC-113), CH3CCl3, CCl3F (CFC-11)) were made using a new analytical technique on RV Meteor cruise 15 along 19°S (World Ocean Circulation Experiment (WOCE) Line A9)) in the Atlantic Ocean during February–March 1991. A separate analytical system was used to determine CCl2F2 (CFC-12) and CCl3F (CFC-11). A limited number of CFC-113 profiles indicated that it was undetectable below 400–500 m. The CCl4 data indicate that the entire Brazil Basin contains readily measurable levels of CCl4 (〉0.05 pmol kg−1), whereas the deep Angola Basin contains very low levels (≤0.02 pmol kg−1). Slightly higher levels were found close to the bottom in the deep Angola Basin: possibly an anthropogenic signature. In contrast, most of the deep Brazil Basin and all of the deep Angola Basin (〉1000 m) had undetectable levels of CFC-11, CFC-12, and CFC-113. Preindustrial levels of CCl4 in the atmosphere were therefore negligible (atmospheric mixing ratio 〈0.1 pptv). CCl4/CFC-11 ratios are used to estimate apparent ages and dilution factors for the North Atlantic Deep Water and Antarctic Bottom Water. Whereas CCl4/CFC-11/CFC-12 levels are internally consistent in deep waters, suggesting near-conservative behavior, there is evidence for very rapid removal of CCl4 in the thermocline. Removal rates suggest that in addition to neutral hydrolysis, some other loss pathway must be involved.

Description: Long-range global climate forecasts have been made by use of a model for predicting a tropical Pacific sea surface temperature (SST) in tandem with an atmospheric general circulation model. The SST is predicted first at long lead times into the future. These ocean forecasts are then used to force the atmospheric model and so produce climate forecasts at lead times of the SST forecasts. Prediction of the wintertime 500mb height, surface air temperature and precipitation for seven large climatic events of the 1970 1990s by this two-tiered technique agree well in general with observations over many regions of the globe. The levels of agreement are high enough in some regions to have practical utility.

Description: High-resolution benthic oxygen isotope and dust flux records from Ocean Drilling Program site 659 have been analyzed to extend the astronomically calibrated isotope timescale for the Atlantic from 2.85 Ma back to 5 Ma. Spectral analysis of the δ18O record indicates that the 41-kyr period of Earth's orbital obliquity dominates the Pliocene record. This is shown to be true regardless of fundamental changes in the Earth's climate during the Pliocene. However, the cycles of Sahelian aridity fluctuations indicate a shift in spectral character near 3 Ma. From the early Pliocene to 3 Ma, the periodicities were dominantly precessional (19 and 23 kyr) and remained strong until 1.5 Ma. Subsequent to 3 Ma, the variance at the obliquity period (41 kyr) increased. The timescale tuned to precession suggests that the Pliocene was longer than previously estimated by more than 0.5 m.y.

Description: Changes in permeability and porosity during shortening deformation of Carrara marble and hot-pressed calcite aggregates were measured under high pressure at room temperature using argon as pore fluid. At effective pressures of 30 and 50 MPa, the permeability of Carrara marble increased by up to 2 orders of magnitude with less than 2% strain during which the connected porosity increased by only 0.005. The permeability increased more slowly with further strain up to 18%, during which the connected porosity increased by a further 0.05 to 0.06. At effective pressures of 100 MPa to 200 MPa, these effects were much less marked. In hot-pressed calcite aggregates, deformed at an effective pressure of 50 MPa, the permeability increased by about 2 orders of magnitude after about 12% strain and an increase in connected porosity of about 0.03. Microstructural studies indicate that, in the coarse-grained Carrara marble specimens, both transgranular and grain boundary cracks are present after room temperature deformation. For a given strain, the average length and the linear density of transgranular cracks decrease with increasing effective pressure. In fine-grained, hot-pressed calcite aggregates, dilatancy is mainly due to opening of grain boundary cracks. The very marked increase in permeability with small strain at low effective pressure can be correlated with the proliferation of connected microcracks of relatively large apertures, deduced on the basis of theoretical models.

Description: The present study contributes new information on the cephalopods off Namibia, contains the first record of Ornithoteuthis volatilis (Sasaki, 1915) in the Atlantic, and adds records of six species in the Benguela Current and three species in Namibian waters. The presence of certain species seldom encountered in the Benguela Current has been confirmed. A compilation of the cephalopod fauna off Namibia had also been included, listing 65 species. Additional morphological data on Stoloteuthis leucoptera, Lycoteuthis lorigera, Architeuthis sp., Pholidoteuthis boschmai, Ornithoteuthis volatilis, Eledone nigra, and Graneledone sp. have been provided. The status of the genus Lycoteuthis has been reviewed in the light of the first collection of Lycoteuthis lorigera (Steenstrup, 1875) males in the Atlantic, and Lycoteuthis diadema (Chun, 1900) has been considered to be a synonym for Lycoteuthis lorigera

Description: During the years 1989–1993 an intensive collection of fishes from the aphotic zone (below 150 m) of the northern part of the Gulf of Aqaba was conducted. This survey recorded 69 fish species, 8 elasmobranchs, and 61 teleosts, belonging to 45 families. Fifteen species are endemic to the Red Sea: Mustelus mosis, Narcine bentuviai, Rhinobatos punctifer, Ophichthus echeloides, Rhynchoconger sp., Physiculus marisrubri, Ostichthys hypsipterygion sufensis, Pterygotrigla sp., Uranoscopus marisrubri, Parascolopsis sp.1 and sp. 2, Atrobucca geniae, Chromis pelloura, Samariscus sp., Thamnaconus modestoides erythraeensis. Eleven species are new records for the Red Sea: Gymnothorax johnsoni, Rhynchoconger sp., Synodus doaki, Pterygotrigla sp., Chelidoperca pleurospilus, Carangoides equula, Parascolopsis sp. 1 and sp. 2, Bodianus leucostictus, Paracaesio sordidus, and Samariscus sp. Two species, Cociella crocodilo and Parascolopsis eriomma, are first substantiated records for the Red Sea. None of the species recorded in this list is considered conventional deep-sea fishes. The ichthyofauna of the aphotic zone of the Gulf of Aqaba is composed of species of shallower origin.

Description: Current measurements from two consecutive yearlong deployments of three moored stations at the western end of the equator in the Atlantic, along 44°W, are used to determine the northwestward flow of warm water in the upper several 100 m and of the southeastward counterflow of North Atlantic Deep Water (NADW). Measurements from three acoustic Doppler current profilers (ADCPs) looking upward from 300 m toward the surface allowed calculation of a time series of upper layer transports over 1 year. Mean transport through the array for the upper 300 m is 23.8 Sv with an annual cycle of only ±3 Sv that has its maximum in June-August and minimum in northern spring. Estimated additional mean northwestward transport in the range 300–600 m is 6.7 Sv, based on moored data and shipboard Pegasus and lowered ADCP profiling. In the depth range 1400–3100 m a current core with maximum annual mean southeastward speed of 30 cm s−1 is found along the continental slope that carries an estimated upper NADW transport of 14.2–17.3 Sv, depending on the extrapolation used between the mooring in the core and the continental slope. This transport is higher than off-equatorial estimates and suggests near-equatorial recirculation at the upper NADW level, in agreement with northwestward mean flow found about 140 km offshore. Below 3100 m and above the 1.8°C isotherm, only a small core of lower NADW flow with speeds of 10–15 cm s−1 is found over the flat part of the basin near 1.5°N, clearly separated from the continental slope by a zone of near-zero mean speeds. Estimated transport of that small current core is about 4.5 Sv, which is significantly below other estimates of near-equatorial transport of lower NADW and suggests that a major fraction of lower NADW may cross the 44°W meridian north of the Ceara Rise. Intraseasonal variability is large, although smaller than observed at 8°N near the western boundary. It occurs at a period of about 1 month when it is dominant in the near-surface records and corresponds to earlier observations in the equatorial zones of all oceans and at a period of about 2 months when it is dominant at the NADW level and could be imported either from the north along the boundary or from the east along the equator. The existence of an annual cycle in the deep currents of a few centimeters per second amplitude, as suggested by high-resolution numerical model results, could neither be proven nor disproven because of the high amount of shorter-period variability.

Description: Hydrographic data of temperature, salinity, oxygen, nitrate, phosphate, and silicate at 81 stations with 435 samples on 3 sections between the Azores, the Grand Banks of Newfoundland, and the Bermuda Islands are used to determine the mixing of water masses by optimum multiparameter analysis over the depth range 100–1500 m. The method optimally utilizes all information from our hydrographic data set by solving an overdetermined set of linear mixing equations for all parameters using the method of least squares residuals. It is shown that the method gives quantitative information on the influence of the various water masses of the western North Atlantic. The Gulf Stream and the North Atlantic Current appear as broad bands transporting large amounts of Western North Atlantic Central Water at their warm flank. Western Subarctic Intermediate Water and Shelf Water supplied by the Labrador Current and containing significant amounts of Labrador Current Water are found on their inshore side. The area of the Azores front is found in the vicinity of the Comer Seamounts, where the uniform water mass distribution of the Sargasso Sea changes into a more complex structure that reflects the influence of water masses originating in the Labrador Sea. Small-scale structures, like eddies or Gulf Stream rings, are also detectable by this analysis method. Comparison with dynamic height analysis supports the circulation pattern of the North Atlantic Current as a continuation of the Gulf Stream, and of the southeastward flowing Azores Current originating in the area of the Southeast Newfoundland Rise.

Description: Measurements made with satellite-tracked buoys drogued in different layers between the sea surface and 30-m depth under homogeneous winter conditions in the North Sea allow analysis of the Ekman currents under a large variety of wind conditions. The experiment lasted from November 20, 1991, until February 29, 1992. The first 4 weeks of this period, during which the buoys stayed close together, are used to determine the Ekman stresses. The total current field is a superposition of barotropic currents due to sea level variations and Ekman currents. The classical Ekman theory is not able to describe properly the observed deflection of the currents to the right of the wind direction and their decay with depth. This deflection is 10° near the sea surface and increases to approximately 50° in 25-m depth. The relation between wind stress and the stress field in the interior of the water is given by a tensor, which describes the rotation and the variation of the stress with increasing depth. The concept of eddy viscosity is applicable, if a viscosity tensor is used to relate stress and vertical shear. The viscosity tensor is a function of the vertical coordinate only and is independent from the wind stress. It shows maximum values in 15- to 20-m depth and may be due to Langmuir circulation cells. Further studies are needed to determine the physics of this tensor. Its magnitude in the interior of the mixed layer exceeds 1000 cgs units. Consequently, Ekman currents are weak and may not be the dominant currents within the mixed layer.

Description: Tests on the effects of two herbivore groups (littorinid snails and gammarid amphipods), on algal succession in high intertidal tidepools dominated by Fucus distichus showed that the grazer groups exert different grazing pressures on the algae. The differences can be related to the feeding morphologies ofthe two grazer guilds. The scraping, microphagous littorinid snails prevent the establishment of both micro- and rnacroalgae at the microscopic level. The biting, macrophagous gammarid amphipods are ineffective at grazing microalgae and prostrate macroalgae from the substratum, but exert a considerable influence on the erect macroalgae which escape littorinid grazing. Despite differences in feeding mechanisms, the magnitude of the effect of the two grazer groups on the canopy cover of macroalgae is similar.

Description: A new species of Siboglinum is reported from off the Tejo mouth, Portugal. It was dredged from c. 1100 m. It resembles S. atlanticum and certain other species, in having paired white glandular stripes on the forepart. In the posterior trunk region we found small gram-negative internal symbiotic bacteria. All described species of the genus Siboglinum are equipped with a single tentacle, but one of our specimens bears two tentacles.

Description: Most atmospheric parameters relevant to microbe dissemination into the atmosphere, including aerial transport and deposition, can be monitored by temperature and humidity, aerosols, clouds, precipitation, and wind through current meteorological and other satellite systems. A wide range of these parameters are already extracted and distributed operationally on a regional or global basis like cloudiness, cloud height, cloud motion, winds, surface temperature and atmospheric temperature profiles, and precipitation estimates, Some of these products like cloud motion, winds, and temperature profiles enter weather forecast models for initialization purposes. These models predict the global state of the atmosphere (some include precipitation and cloudiness) quite reliably for several days. Thus, an important part of the necessary technical framework for global disease spread and transmission monitoring exists.

Description: During the ‘Meteor’ Expedition 13 in July and August 1990 to the northern part of the Norwegian Sea off west Spitsbergen, 7 stations with a depth of 2000 m or more were sampled with Agassiz trawl or hyperbenthos sledge, 14 more with a large box corer. Sponges were found at 6 of the trawl stations and in 2 box cores. A total of 19 species occurred, most of which were new to the area. Eight of the species were encountered more often than the other 11. Literature review and check of unpublished samples showed that by distribution, frequency of occurrence or abundance these species can be defined as the typical sponge association of the Norwegian and Greenland abyssal sea. This sponge association has a wide occurrence over the deep Norwegian-Greenland seas and parts of the Arctic basins. The analysis of substrate utilization of the 8 core species shows that all of them are able to colonize soft bottom, even some that previously had been considered to be dependent on hard substrate exclusively. Alternative substrate utilization and, in some species, the adoption of an infaunallife style are judged to be major reasons for the success of these species in the deep sea. The infaunal life style of the species Thenea abyssorum, Trichostemma sol and Tentorium semisuberites is documented and population structure data are given for the first time.

Description: Mesoscale fluctuations in the western tropical Atlantic are analyzed in Geosat altimetry sea surface height (SSH) and geostrophic velocity anomalies to investigate the role of eddies in the North Brazil Current (NBC) retroflection zone. The detachment of anticyclonic eddies from the NBC retroflection is observed during November through January, when the NBC retroflection into the North Equatorial Countercurrent (NECC) weakens and finally breaks down. These eddies are traced over more than 2 months between 50° and 60°W on their way toward the Caribbean, at average speeds of 15 cm s−1. In one case an apparent merger of two anticyclonic eddies occurs, one detached from the retroflection zone and one detached from the NECC. Cyclonic eddies are also observed but are generally less persistent. Mesoscale SSH variance just west of the retroflection increases by a factor of 2 from early summer to winter, mainly because of the anticyclonic eddies. Interhemispheric water mass transfer associated with the eddy flux out of the NBC retroflection may amount to an average transport of 3 Sv.

Description: Climatological data sets are used to estimate the amount of water changing temperature and salinity at the sea-surface owing to air-sea exchanges. Considering this conversion as a function of sea-surface temperature and salinity leads to the definition of a conversion vector, which represents mass sources and sinks for each water type. The vector representation shows graphically the way the shape of the temperature-salinity relation is driven at the surface by the air-sea heat and fresh water fluxes.

Description: Hydrographic observations from the Iberian Basin demonstrate the variability of water masses in upper and intermediate layers. The surveyed area embraces the internal front between water masses from higher latitudes and the Mediterranean outflow, exhibits several isolated Mediterranean eddy (meddy) structures at middepth, and displays the virtual source region for the Mediterranean Water (MW) tongue off the Portuguese continental slope. The description is enhanced by additional chlorofluoromethane measurements, which show anomalously high concentrations at middepth, due to mixing of MW with the overlying Atlantic waters in the Gulf of Cadiz. The geostrophic stream function shows several meddylike features that not only are remarkably extended in the depth range of the MW, but are also correlated with surface height anomalies.

Description: Nontransform offsets are a fundamental aspect of the offset geometry exhibited along the mid-oceanic ridge system, independent of spreading rate. Along the slow/intermediate opening (〈40 mm/y full rate) Mid-Atlantic Ridge these offsets of the ridge axis range in length from less than 10 km to approximately 30 km and vary in age offset from 0.5 to 2.0 m.y. The variable morphotectonic geometries associated with these discontinuities indicate that horizontal shear strains are accommodated by both extensional and strike-slip tectonism and that the geometries are unstable in time. In many cases, there appears to be an evolutionary relationship between transform fault boundaries and nontransform offsets as the result of prolonged differential asymmetric spreading between adjoining ridge segments. The finite element method is used to study the complex stress field associated with these small-offset discontinuities of ridges with slow (30 mm/y) and fast (100 mm/y) total opening rates. A plane stress plate model examines the variation in the horizontal tectonic stress field produced by offsets with different lengths and changes in the ratio of a ridge-normal tensile stress resisting plate separation to a shear stress resisting relative plate motion along the discontinuity. The predicted fault patterns based on the calculated stress field are compared with seafloor observations in terms of the morphotectonic patterns and evolution of nontransform offsets. For a slow spreading rate, the analysis shows that all structural geometries observed can be modeled by a range of offset lengths (5, 10, 20, 30, and 40 km) and by a ridge-normal stress 3 to 5 times greater than the discontinuity shear stress. These findings suggest that nontransform offsets are zones of mechanical weakness relative to the surrounding lithosphere. An offset length between 10 and 20 km is predicted to be the threshold length for maintaining a transform fault geometry. As inferred from ridge axis morphology, there seems to be a strong link between the magnitude of the stress ratio and the time varying magmatic activity along and between ridge segments. While our models are consistent with a weak discontinuity shear stress relative to the ridge-normal stress to explain the geometries of nontransform offsets of slow-spreading centers, a weaker ridge-normal stress to discontinuity shear stress most closely models the development of an overlapping spreading center geometry, the distinctive geometry of nontransform offsets of spreading centers opening at fast rates. This difference is attributed to magma supply along-axis, relatively continuous for fast-spreading centers and intermittent for slow-spreading centers, and a preexisting zone of mechanical weakness linked to the evolution of nontransform offsets from transform faults on slow-spreading centers.

Description: Three data types are compared in the low-current-velocity regime in the southeastern North Atlantic, between 12-degrees-N and 30-degrees-N, 29-degrees-W and 18-degrees-W: Geosat altimetric sea level and derived surface geostrophic velocities, shallow current meter velocities, and dynamic heights derived from hydrographic data from cruises 4, 6, and 9 of the research vessel Meteor. The four current meter daily time series, at depths around 200 m, were smoothed over 1 month; the altimetric geostrophic velocities were computed from sea surface slopes over 142 km every 17 days. The correlation coefficients between the current meter and altimetric geostrophic velocities range between 0.64 and 0.90 for the moorings near 29-degrees-N but between 0.32 and 0.71 for the two around 21-degrees-N; the associated rms discrepancies between the two measurement types range between 1.5 and 4.4 cm/s, which is 49% to 127% of the rms of the respective current meter time series. Dynamic heights relative to 1950 dbar for the months of November 1986 (d(M4)), November 1987 (d(M6)), and February 1989 (d(M9)) were computed from Meteor cruises 4, 6, and 9. Both dynamic heights and altimetric heights (h(M4), h(M6), h(M9)) were averaged over 1-degrees boxes for the duration of each cruise. Differences d(M4) - d(M6) and d(M9) - d(M6) were computed only at bins where at least one station from both cruises existed, Assuming that dynamic heights d in dynamic centimeters are equivalent to sea level h in centimeters, the standard deviation sigma of the differences ((h(M4) - h(M6)) - (d(M4) - d(M6))) and corresponding M9 - M6 values was 2.1 cm. This value (squared) is only 13% of the (5.8 cm)2 variance of the dynamic height differences and is indistinguishable from the 2.7- to 5.6-cm natural variability of sea level in the area expected between the times when the ship and the satellite sampled the ocean. The areally averaged discrepancy for M9 - M6 was only 0.7 cm, but the corresponding value for M4 - M6 was 5.2 cm. A systematic difference between the water vapor corrections used before and after July 1987 is responsible for the M4 - M6 difference. The average M4 - M6 discrepancy is only 0.1 cm using the Fleet Numerical Oceanography Center correction, with a standard deviation of 3.1 cm. In spite of the underlying differences in sampling and physics, including unknown barotropic components not included in our hydrographic dynamic heights, and in data errors, including water vapor, ionospheric, and orbital effects on the altimetry, consistent interannual changes of the mean sea level from the independently obtained altimetric and hydrographic data sets are obtained, and correlated seasonal changes in surface currents are observed with both altimetry and current meters.

Description: During the winter of 1988–1989 five acoustic Doppler current profilers (ADCPs) were moored in the central Greenland Sea to measure vertical currents that might occur in conjunction with deep mixing and convection. Two ADCPs were looking up from about 300 m and combined with thermistor strings in the depth range 60–260 m, two were looking downward from 200 m, and one was looking upward from 1400 m. First maxima of vertical velocity variance occurred at two events of strong cold winds in October and November when cooling and turbulence in the shallow mixed layer generated internal waves in the thermocline. Beginning in late November the marginal ice zone expanded eastward over the central Greenland Sea, reaching its maximum extent in late December. In mid-January a bay of ice-free water opened over the central Greenland Sea, leaving a wedge of ice, the “is odden,” curled around it along the axis of the Jan Mayen Current and then northeastward and existing well into April 1989. Below the ice a mixed layer at freezing temperatures developed that increased in thickness from 60 to 120 m during the period of ice cover, corresponding to an average heat loss of about 40 W m−2. Through brine rejection, mixed-layer salinity increased steadily, reducing stability to underlying weakly stratified layers (Roach et al., 1993). During the ice cover period, vertical currents were at a minimum. After the opening of the ice-free bay, successive mixed-layer deepening to 〉350 m occurred in conjunction with cooling events around February 1 and 15, accompanied by strong small-scale vertical velocity variations. Upward mixing of more saline waters of Atlantic origin during this phase reduced the stability further, generating a pool of homogeneous water of 〉50 km horizontal extent in the central Greenland Sea, preconditioned for subsequent convection to greater depths. Individual convection events were observed during March 6–16, associated with downward velocities at the 1400-m level of about 3 cm s−l. One event was identified as a plume of about 300-m horizontal scale, in agreement with recently advanced scaling arguments and model results, and with earlier similar observations in the Gulf of Lions, western Mediterranean. The deep convection occurred in the center of the ice-free bay; hence brine rejection did not seem necessary for its generation. Plume temperatures at 1400 m were generally higher than that of the homogeneous surface pool, suggesting entrainment of surrounding warmer waters on the way down. Mean vertical velocity over a period of convection events was indistinguishable from zero, suggesting that plumes served as a mixing agent rather than causing mean downward transport of water masses. However, different from the surface pool that was governed by mixed-layer physics, the water between 400 and 1400 m was not horizontally homogenized in a large patch by the sporadic plumes. Overall, and compared to results from the Gulf of Lions, convection activity in the central Greenland Sea was weak and limited to intermediate depths in winter 1988–1989.

Description: An analysis is presented of geostrophic volume transport across a zonal line along 28-degrees-N in the eastern Atlantic. The data are from an array of five moorings with 200-km spacing carrying temperature sensors and one current meter each for 1 or 2 years. Transport changes in the main thermocline relative to a fixed depth level are obtained by the use of temperature-salinity relationships. The transport variability is simulated by two propagating waves with first-order baroclinic mode structure. Solutions exist with annual and semi-annual periods and zonal wavelengths of 100-200 km and 300 km, respectively. Assuming quasi-geostrophic dynamics and using results on the Reynolds stress, the dominating waves of annual and semi-annual period are found to propagate to the southwest, with 45-degrees-60-degrees and 25-degrees to the south off the westward direction, respectively. Wave solutions with a 90-day period and a zonal wavelength of about 300 km are interpreted as an effect of barotropic waves arising due to horizontal temperature inhomogeneity. The propagation is about +/-25-degrees off the westward direction. In general, good approximations are obtained with the propagating wave simulations in the western and central part of the array, while large differences occur between observation and simulation close to the Canary archipelago. Possible causes for these differences are discussed.

Description: The proposal by Quay et al. [1992] that the time histories of 13C in atmospheric CO2 and oceanic ∑CO2 provide a constraint on the magnitude of uptake of fossil fuel CO2 by the ocean is examined. Our analysis suggests that, while the potential is there, the data base is too inaccurate to permit a distinction to be made among the carbon budgets currently on the table. Examples are given to demonstrate that the twenty or so percent uncertainties in the size of the effective exchange reservoir and in the magnitudes of the temporal changes in the 13C/12C ratio in atmospheric CO2 and ocean ∑CO2 are just too large to permit a reliable estimate of oceanic uptake of fossil fuel CO2. We conclude that tracer-verified ocean general circulation models offer much better estimates than that based on the 13C budget.

Description: We present a method for determining the δ180 of seawater in the deep ocean during the last glacial maximum from the measured δ180 values of deep sea pore fluids. Using data from Deep Sea Drilling Project (DSDP) site 576 in the Western Pacific, this method yields a glacial to interglacial change in δ180swof 1.010.25 0/00. This value for ~δ180sw is the first direct measurement of deep ocean 8180 for the last glacial maximum and avoids the problems of spatial and temporal variability of the δ180 of surface water implicit in previous determinations. More precise, higher resolution pore fluid measurements are required to improve this determination.

Description: The passive continental margin off east Greenland has been shaped by tectonic and sedimentary processes, and typical physiographic patterns have evolved over the past few million years under the influence of the late Cenozoic Northern Hemisphere glaciations. The Greenland ice shield has been particularly affected. GLORIA (Geological Long Range Inclined Asdic), the Institute of Oceanographic Sciences' (IOS) long-range, side-scan sonar, was used on a 1992 RV Livonia cruise to map large-scale changes in sedimentary patterns along the east Greenland continental margin. The overall objective of this research program was to determine the variety of large-scale seafloor processes to improve our understanding of the interaction between ice sheets, current regimes, and sedimentary processes. In cooperation with IOS and the RV Livonia, a high-quality set of seafloor data has been produced. GLORIA'S first survey of east Greenland's continental margin covered several 1000- × 50-km-wide swaths (Figure 1) and yielded an impressive sidescan sonar image of the complete Greenland Basin and margin (about 250,000 km2). A mosaic of the data was made at a scale of 1:375,000. The base map was prepared with a polar stereographic projection having a standard parallel of 71°.

Description: High‐resolution records of opal, carbonate, and terrigenous fluxes have been obtained from a high‐sedimentation rate core (MD84‐527: 43°50′S; 51°19;′E; 3269 m) by normalization to 230Th. This method estimates paleofluxes to the seafloor on a point‐by‐point basis and distinguishes changes in sediment accumulation due to variations in vertical rain rates from those due to changes in syndepositional sediment redistribution by bottom currents. We also measured sediment δ15N to evaluate the changes in nitrate utilization in the overlying surface waters associated with paleoflux variations. Our results show that opal accumulation rates on the seafloor during the Holocene and stage 3, based on 14C dating, were respectively tenfold and fivefold higher than the vertical rain rates, At this particular location, changes in opal accumulation on the seafloor appear to be mainly controlled by sediment redistribution by bottom currents rather than variations in opal fluxes from the overlying water column. Correction for syndepositional sediment redistribution and the improved time resolution that can be achieved by normalization to 230Th disclose important variations in opal rain rates. We found relatively high but variable opal paleoflux during stage 3, with two maxima centered at 36 and 30 kyr B.P., low opal paleoflux during stage 2 and deglaciation and a pronounced maximum during the early Holocene, We interpret this record as reflecting variations in opal production rates associated with climate‐induced latitudinal migration of the southern ocean frontal system. Sediments deposited during periods of high opal paleoflux also have high authigenic U concentrations, suggesting more reducing conditions in the sediment, and high Pa‐231/Th‐230 ratios, suggesting increased scavenging from the water column. Sediment δ15N is circa 1.5 per mil higher during isotopic stage 2 and deglaciation. The low opal rain rates recorded during that period appear to have been associated with increased nitrate depletion. This suggests that opal paleofluxes do not simply reflect latitudinal migration of the frontal system but also changes in the structure of the upper water column. Increased stratification during isotopic stage 2 and deglaciation could have been produced by a meltwater lid, leading to lower nitrate supply rates to surface waters.

Description: Seamount phosphorites have been recognized since the 1950s, but this is the first study to provide an in depth exploration of the origin and history of these widespread deposits. Representative samples from equatorial Pacific Cretaceous seamounts were analyzed for chemical, mineralogical, and stable isotope compositions. The phosphorites occur in a wide variety of forms, but most commonly carbonate fluorapatite (CFA) replaced middle Eocene and older carbonate sediment in a deep water environment (〉1000 m). Element ratios distinguish seamount phosphorites from continental margin, plateau, and insular phosphorites. Uranium and thorium contents are low and total rare earth element (REE) contents are generally high. REE ratios and shale‐normalized patterns demonstrate that the REEs and host CFA were derived from seawater. Strontium isotopic compositions compared with inferred Cenozoic seawater curves define two major episodes of Cenozoic phosphatization: Late Eocene/early Oligocene (39–34 Ma) and late Oligocene/early Miocene (27–21 Ma); three minor events are also indicated. The major episodes occurred at times of climate transition, the first from a nonglacial to glacial earth and the second from a predominantly glacial to warm earth. The paleoceanographic conditions that existed at those times initiated and sustained development of phosphorite by accumulation of dissolved phosphorus in the deep sea during relatively stable climatic conditions when oceanic circulation was sluggish. Fluctuations in climate, sealevel, and upwelling that accompanied the climate transitions may have driven cycles of enrichment and depletion of the deep‐sea phosphorus reservoir. As temperature gradients in the oceans increased, Antarctic glaciation expanded and oceanic circulation and upwelling intensified. Expansion and intensification of the oxygen minimum zone may have increased the capacity for midwater storage of phosphorus supplied by dynamic upwelling around seamounts; however, the bottom waters never became anoxic during the phosphogenic episodes. Fluctuations in the CCD and lysocline, CO2 fluxes, and changes in bottom water circulation and temperatures may have bathed the seamount carbonates in more corrosive waters which, coupled with increased supplies of dissolved phosphorus, promoted replacement processes. The late Eocene/early Oligocene phosphogenic episode recorded in seamount deposits is not matched by large phosphorite deposits in the geologic record, whereas the late Oligocene/early Miocene episode and middle Miocene event are matched by large deposits distributed globally. The seamount phosphorites are exposed at the surface of the seamounts and have been for most of the Neogene and Oligocene. The phosphorites do not show signs of etching that would indicate substantial undersaturation of seawater phosphate with respect to CFA. Mass balance calculations indicate that about 5.4–19 × 1012 g of P2O5 are locked up in equatorial Pacific seamount phosphorites. That amount is equivalent to about 2‐7 years of the present annual input from rivers.

Description: Measurements of opal preservation in deep sea sediment cores have been presented in three ways: the opal concentration as a fraction of total dry weight (%opaltot), the opal concentration normalized to calcite‐free dry weight (%opalcalcite‐free), and me opal accumulation rate (opal MAR). It is tempting to interpret changes in these indices as indicators of rates of biological production in past oceans. Based on theoretical constraints, we argue that in typical tropical and subtropical sediments, both %Opalcalcite‐free and opal MAR reflect a significant artifact of dilution by other phases. Thus the band of high %Opalcalcite‐free in the equatorial Pacific appears to be caused in large part by the high %Calcite in that region, rather than by high opal productivity. The best candidate for a reliable paleoproductivity proxy appears to be %Opaltot. Unfortunately, present‐day %Opaltot data from tropical and subtropical regions show little or no systematic trend with the rain rate of opal. Pore water silica concentration data reveal that the apparent pore water opal solubility is not constant but correlates regionally with the rain rate of opal to the seafloor. A model that treats opal as a single homogeneous phase with a single well‐defined solubility product predicts a strong dependence of opal concentration on rain rate (in stark contrast to the data), and a constant asymptotic pore water Si. Two models representing opal as multiple heterogeneous phases with different solubilities are able to reproduce the observed asymptotic pore water Si/rain rate relationship, but not the lack of rain rate trend in the opal concentration data. Only by assuming a systematic trend in the quality of opal (i.e., the solubility) as a function of opal production, can we reproduce the observed pattern of opal preservation. The implication of this study is that changes in opal preservation in the geologic record cannot simply be interpreted in terms of changes in surface ocean productivity until our understanding of opal diagenesis can be improved.

Description: A relation between creep rate at the surface trace of a fault, the depth to the bottom of the creeping zone, and the rate of stress accumulation on the fault is derived from Weertman's 1964 friction model of slip on a fault. A 5 ± 1 km depth for the creeping zone on the Hayward fault is estimated from the measured creep rate (5 mm/yr) at the fault trace and the rate of stress increase on the upper segment of the fault trace inferred from geodetic measurements across the San Francisco Bay area. Although fault creep partially accommodates the secular slip rate on the Hayward fault, a slip deficit is accumulating equivalent to a magnitude 6.6 earthquake on each 40 km segment of the fault each century. Thus, the current behavior of the fault is consistent with its seismic history, which includes two moderate earthquakes in the mid‐1800's.

Description: The cephalopod fauna of the Sea of Marmara was investigated during the years 1991-1992. Three species, Sepia orbignyana Ferussac, 1826; Rondeletiola minor Naef, 1912; and Todaropsis eblanae (Ball, 1841), are hereby recorded for the first time from the Sea of Marmara.

Description: Fertilizing capacity of spermatozoa collected from various storage sites in the male and female squids were examined by inseminated eggs in the presence or absence of gelatinous substances of the oviducal gland origin. Over 90% of the eggs were fertilized by the spermatozoa collected from the female's seminal receptacle regardless of the presence or absence of the gelatinous substance. Elevation of the chorion and the formation of perivitelline space was observed only in the jellied eggs. All jellyless eggs without perivitelline space died in 4 days after insemination. Spermatozoa collected from the spermatophore in the male's accessory gland could fertilize the majority of the eggs. On the other hand, those from the male's vas deferens could fertilize only 30–50% of both the jellied and jellyless eggs. It may be concluded from these experiments that the gelatinous substance of the oviducal gland origin has nothing to do with fertilization. However, it is essential for the elevation of the chorion and the formation of the perivitelline space. It may also be concluded that squid spermatozoa become fertile before they are transferred to the female's seminal receptacle.

Description: Mature males of Histioteuthis atlantica are described. They differ from immature animals mainly in the unique photophore pattern of the distal portion of the mantle, i.e. in the presence of densely set, lensless photophores. These photophores resemble those on H. elongata, but they are smaller and much more dense on male H. atlantica. The occurrence of the photophore pattern in approximately the same dense concentration on the dorsum as well as the ventrum is unique in the family Histioteuthidae.

Description: The high-resolution model of the wind-driven and thermohaline circulation in the Atlantic Ocean developed in recent years as a “community modeling effort” for the World Ocean Circulation Experiment is examined for the temporal and spatial structure of the deep equatorial current field and its effect on the spreading of North Atlantic Deep Water (NADW). Under seasonally varying wind forcing, the model reveals a system of basin-wide zonal currents of O(5 cm s−1), alternating east-west, and oscillating at an annual period. The current fluctuations are induced by the seasonal cycle of the wind stress in the equatorial Atlantic and show characteristics of long equatorial Rossby waves with westward phase propagation of about 15 cm s−1. The mean flow in the deep western tropical Atlantic is governed by a deep western boundary current (DWBC) with core velocities of more than 10 cm s−1. Only a small fraction of the DWBC branches off at the equator, with correspondingly low mean eastward currents of only about 1 cm s−1. Despite this weak advection along the equator, a well-developed salinity tongue is observed in the model, which is reminiscent of observed property distributions at the upper NADW level. The model evaluation indicates the salinity pattern to be a result of a balance between mean zonal advection and meridional diffusion of salt. The presence of the zonal current oscillations appears to have no significance for the existence of the salinity tongue.

Description: Seismically derived depth estimates to the top of the oceanic crust beneath the Hawaiian Islands indicate that the curvature of the deflected lithosphère is much larger than commonly believed. The conservative and model-independent curvature estimates exceed 10−7 m−1 and are comparable in magnitude to curvatures at trenches and outer rise systems. The depth estimates are used to constrain both two-dimensional (2-D) and three-dimensional (3-D) flexural models. The curvature constraints require a 2-D variable elastic thickness that decreases from 35 km in areas away from the volcanic load to 25 km directly beneath the load. In an attempt to understand the nature of the yielding beneath the Hawaiian Islands we introduce two new 3-D models. The first model combines a realistic yield strength based rheology with a new technique for 3-D flexure calculations in which the elastic plate thickness is curvature-dependent. The new variable rigidity model predicts an undeformed (mechanical) plate thickness of 44 km, decreasing to 33 km beneath the big island of Hawaii. The best-fitting mechanical thickness corresponds approximately to the depth to the 600 °C isotherm in 90-m.y.-old lithosphere. The second model uses a broken plate, but here the crack is oriented along the weak Molokai fracture zone rather than along the island chain trend. This unconventional flexure model can explain the observed asymmetry in the depth data across the fracture zone without requiring the excessively large elastic thickness of more conventional broken plate models. Both the proposed models imply that modeling with constant thickness plates may underestimate the true mechanical plate thickness by being unduly influenced by the weak zone beneath the seamounts.

Description: The beaks of 9,994 cephalopods of 61 species, obtained mainly from chick regurgitations of wandering albatrosses (Diomedea exulans L.) at Gough, Auckland, Antipodes, Prince Edward and Macquarie Islands and South Georgia, were used to specify and calculate the biomass of cephalopods consumed. Histioteuthidae were most important by numbers and biomass at Gough Island (in warmest seas), but Onycboteuthidae increasingly superseded them southwards; Kondakovia longimana formed 59 to 75% of biomass eaten at the three localities nearest the Antarctic Polar Front. Other important families were Octopoteuthidae, Cranchiidae, Architeuthidae (juveniles) and Ommastrephidae (South Georgia only). Most frequently eaten were Histioteuthis atlantica 13.7%, Galiteuthis glacialis 12.4%, H. eltaninae 12.0% and Kondakovia longimana 11.6%. Wandering albatrosses rearing chicks can forage at least to 3,000 km in a single foray, and may exploit an important food source about 1200 km from the nest (as in the probable commensalism of South Georgian birds with the Falkland Islands fishery). They feed, sometimes opportunistically, on cephalopods active or moribund at the surface, or discarded or lost by trawlers, cetaceans or seals. Vertically migrating cephalopods, especially bioluminescent species, are disproportionately frequent in their non-commensal diet, suggesting that they often feed at night.

Description: A link is proposed between the processes that led to the evolution of large species of squid and the highly variable, cyclic recruitment seen in squid fisheries. Maximum growth requires maximal feeding and minimal routine metabolism at optimum temperatures, which decrease as squid grow. Topographically induced upwelling zones, inshore of western boundary currents, provide productive environments with appropriate temperatures for all life stages. Most squid are small and live in the tropics or subtropics; locomotor constraints prevent them from swimming long distances. Long annual migrations to spawn upstream in current systems require short-lived squids to maximize rates of growth. Therefore, such systems provide the opportunity and a powerful selective advantage for large size and rapid growth. Increased fecundity and cannibalism provide additional directional selection for large individuals. Current systems show food production peaks (blooms); paralarval release must match these to increase survival. Because squid are semelparous, disruption of delicately balanced lifecycles by physical events can virtually annihilate stocks. Recovery probably requires that populations of large squid "re-evolve" from smaller, more-stable tropical populations of small squid. This recovery phase may extend the "down-side" of abundance cycles. Studies of squid/current systems have focused on western boundary currents, but the Illex complex also associates with eastern boundaries. Such populations are generally smaller than in larger systems, supporting the hypothesis, but more detailed comparisons are required.

Description: During a cruise in March 1988 dedicated to investigation of the marine resources of South Africa's continental slope, 62 species in 22 families of Cephalopoda were collected from the Cape Canyon and Cape Point Valley. Multivariate analysis revealed a clear distinction between cephalopods of the upper and lower continental slope in both benthic and epibenthic habitats. Todaropsis eblanae and Todarodes angolensis were indicator species for the upper slope benthic, from 300 to 500 m, but on the lower slope, in 700–900 m of water, they were replaced by Histioteuthis miranda and Opisthoteuthis agassizii. In the epibenthic, both upper and lower slopes were dominated by Abraliopsis gilchristi and Lycoteuthis ?diadema, but other species characteristic of the lower slope were the oceanic species Mastigoteuthis hjorti, Ctenopteryx sicula and Taonius sp. A. Cranchia scabra indicated the presence of oceanic water at stations 700–900 m deep. Other species of significance in the catches were Todarodes filippovae, Histioteuthis macrohista, Rossia enigmatica and Bathypolypus valdiviae. Species affinities indicate that the cephalopod fauna of the southern African continental slope includes the following zoogeographic components: southern African endemic, circum-Subantarctic species associated with Antarctic Intermediate Water, circum-global southern tropical/subtropical, tropical Indo-Pacific and cosmopolitan tropical/subtropical.

Description: Literature on trophic relationships in the Benguela ecosystem has stressed the importance of cephalopods as prey of groundfish. The groundfish community of the shelf and upper slope of southern Africa is dominated by the Cape hakes, and the results presented (1984–1991) confirm that both species of hake are important predators of cephalopods, especially taking into consideration the abundance of hake in the ecosystem. However, geographic, seasonal and species variability are evident in the patterns observed. The main prey species are Sepia spp. (predominantly Sepia australis), Loligo vulgaris reynaudii, Todaropsis eblanae and Lycoteuthis ?diadema. The last-named is an important food organism for fish. Its systematic status needs revision, however. Qualitative results of studies of cephalopod predation are also provided for kingklip and monkfish.

Description: Cephalopods of importance in the Benguela ecosystem include Loligo vulgaris reynaudii, Todarodes angolensis, Todaropsis eblanae, Lycoteuthis ?diadema, Sepia australis, Octopus spp. (up to three species) and Argonauta spp., and possibly also Ocythoe tuberculata and Rossia enigmatica. Species which may prove important as a result of further research are Lolliguncula mercatoris, Ommastrephes bartramii, Todarodes filippovae, Histioteuthis miranda and Abraliopsis gilchristi. "Importance" is defined on the basis of "survey abundance" (including commercial fisheries) and their trophic links with other organisms. Use of the latter criterion indicates that Sepia australis, Todaropsis eblanae and Lycoteuthis ?diadema are sufficiently abundant to be exploited by fisheries. Unknown factors are dispersal, availability and market considerations. The only examples of cephalopods feeding on commercial species of fish are Loligo v. reynaudii feeding on anchovy Engraulis capensis and Cape hakes Merluccius capensis and/or M. paradoxus in the southern Benguela and Todarodes angolensis preying on Cape hake in the northern Benguela. Such feeding is opportunistic and is not believed to threaten the fish stocks. Predators of cephalopods are mostly opportunistic, switching to other prey when cephalopods are not available. There is no evidence that such predators pose a threat to the Loligo fisheries. The opportunistic nature of cephalopods as prey and predators makes quantification of predation (in both directions) difficult. Data for such quantification are, as yet, unavailable.

Description: The results of ichthyoplankton surveys carried out by the Instituto Nacional de Pesca (INAPE) in the Argentine–Uruguayan Common Fishing Zone (AUCFZ) in summer 1980 and the winters of 1980–1982 are presented. In addition, the results of joint research with INIDEP, the Argentine and Japan Fisheries Agency, on larvae, juveniles and adults of the short-finned squid Illex argentinus carried out in winter 1989 are given, as are data obtained during the joint sardine and anchovy recruitment project carried out by R.V. Meteor in November/December 1989. The short-finned squid Illex argentinus is the most important cephalopod resource of the area, and an extended fishery is carried out on the Patagonian shelf and in the proximity of the Falkland Islands. The fishing season in the AUCFZ, for pre-spawning and spawning animals, extends from early autumn to winter (March–August). Abundance of rhynchoteuthion larvae (417–485 larvae·10 m−2) was greatest in winter in surface temperatures of 12,1–16,9°C and surface salinities of 34,8 – 35,2 × 10−3. The distribution of the larvae is related to the western boundary of the Brazil Current and the convergence front.

Description: The question whether the chokka squid Loligo vulgaris reynaudii resource can be managed effectively is examined in the light of developments in the fishery and knowledge of the resource gathered in recent years. The history of the fishery since its inception in 1985, management controls and the current state of knowledge of stock identity, distribution, seasonality and abundance, life cycle and population dynamics are reviewed as a background to a discussion of management alternatives. Long-term measures, such as fleet limitation, seasonal closures and de facto closed areas and size limits, all appropriate in the early stages of a fishery when knowledge is limited, should be replaced by more-flexible alternatives as knowledge improves. Methods of stock assessment, stock-recruitment studies and further basic biological analyses are recognized as being crucial to improving management methods. An explanation embracing physical oceanographic features and plankton productivity in the vicinity of the spawning grounds is advanced for the mechanisms underlying hatchling survival. The possible contribution of trophic studies to squid management is recognized. Effective management of the chokka squid resource is concluded to be possible provided that the specific areas needing attention be addressed by means of goal-orientated research. Rational, but not necessarily optimal, management decisions can, however, be made even in the absence of stock-recruitment data, by the employment of common-sense measures which generally include some form of effort control.

Description: The carbon isotopic composition of methane emitted by the Alaskan emergent aquatic plants Arctophila fulva, a tundra mid-lake macrophyte, and Carex rostrata, a tundra lake margin macrophyte, was −58.6 ± 0.5 (n=2) and −66.6±2.5 (n= 6) ‰ respectively. The methane emitted by these species was found to be depleted in 13C by 12‰ and 18‰, relative to methane withdrawn from plant stems 1 to 2 cm below the waterline. As the macrophyte-mediated methane flux represented approximately 97% of the flux from these sites, these results suggest the more rapid transport of 12CH4 relative to 13CH4 through plants to the atmosphere. This preferential release of the light isotope of methane, possibly combined with CH4 oxidation, caused the buildup of the heavy isotope within plant stems. Plant stem methane concentrations ranged from 0.2 to 4.0% ( math formula, 1.4; standard deviation (sd), 0.9; n=28) in Arctophila, with an isotopic composition of −46.1±4.3 ‰ (n = 8). Carex stem methane concentrations were lower, ranging from 150 to 1200 ppm ( math formula, 500; standard deviation, 360; n = 8), with an isotopic composition of −48.3±1.4‰ (n=3). Comparisons of the observed isotopic fractionations with those predicted from gas phase effusion and diffusion coefficients suggest a combination of one or both of these gas transport mechanisms with bulk (non-fractionationating) flow.

Description: The Multitracers Experiment studied a transect of water column, sediment trap, and sediment data taken across the California Current to develop quantitative methods for hindcasting paleoproductivity. The experiment used three sediment trap moorings located 120 km, 270 km, and 630 km from shore at the Oregon/California border in North America. We report here about the sedimentation and burial of particulate organic carbon (Corg) and CaCO3. In order to observe how the integrated CaCO3 and Corg burial across the transect has changed since the last glacial maximum, we have correlated core from the three sites using time scales constrained by both radiocarbon and oxygen isotopes. By comparing surface sediments to a two-and-a-half year sediment trap record, we have also defined the modern preservation rates for many of the labile sedimentary materials. Our analysis of the Corg data indicates that significant amounts (20–40%) of the total Corg being buried today in surface sediments is terrestrial. At the last glacial maximum, the terrestrial Corg fraction within 300 km of the coast was about twice as large. Such large fluxes of terrestrial Corg obscure the marine Corg record, which can be interpreted as productivity. When we corrected for the terrestrial organic matter, we found that the mass accumulation rate of marine Corg roughly doubled from the glacial maximum to the present. Because preservation rates of organic carbon are high in the high sedimentation rate cores, corrections for degradation are straightforward and we can be confident that organic carbon rain rate (new productivity) also doubled. As confirmation, the highest burial fluxes of other biogenic components (opal and Ba) also occur in the Holocene. Productivity off Oregon has thus increased dramatically since the last glacial maximum. CaCO3 fluxes also changed radically through the deglaciation; however, they are linked not to CaCO3 production but rather to changes in deepwater carbonate chemistry between 18 Ka and now.

Description: Digital hydrographic data combined with satellite thermal infrared and visible band remote sensing provide a synoptic climatological view of the shallow planktonic environment. This paper uses wind, hydrographic, and ocean remote sensing data to examine southwest monsoon controls on the foraminiferal faunal composition of Recent seafloor sediments of the northwestern Arabian Sea. Ekman pumping resulting in open-ocean upwelling and coastal upwelling create two distinctly different mixed layer plankton environments in the northwestern Arabian Sea during the summer monsoon. Open-sea upwelling to the northwest of the mean July position of the Findlater Jet axis yields a mixed layer environment with temperatures of less than 25°C to about 26.5°C, phytoplankton pigment concentrations between 1.5 and 5.0 mg/m³, and mixed layer depths less than 50 m. Convergence in the Ekman layer in the central Arabian Sea drives the formation of a mixed layer that is greater than 50 m thick, warmer than about 26.5°C, and has phytoplankton pigment concentrations generally below 2.0 mg/m³. Coastal upwelling creates an extremely eutrophic plankton environment that persists over and immediately adjacent to the Omani shelf and undergoes significant offshore transport only within topographically induced coastal squirts. The foraminiferal faunal composition of upper Pleistocene deep-sea sediments of the northwestern Arabian Sea are mainly controlled by vertical nutrient fluxes caused by Ekman pumping, not coastal upwelling. Transfer functions for late Pleistocene mixed layer depth, temperature, and chlorophyll have been obtained through factor analysis and nonlinear multiple regression between late summer mixed layer environment and Recent sediment faunal observations.

Description: This paper provides a detailed hydrographic climatology for the shallow northwestern Arabian Sea prior to and during the southwest monsoon, presented as multiple-year composite vertical hydrographic sections based on National Oceanographic Data Center historical ocean station data. Temperature and salinity measurements are used to infer the water masses present in the upper 500 m. The hydrographic evolution depicted on bimonthly sections is inferred to result from wind-driven physical processes. In the northwestern Arabian Sea the water mass in the upper 50 m is the Arabian Sea Surface Water. Waters from 50 to 500 m are formed by mixing of Arabian Sea Surface Water with Antarctic and Indonesian intermediate waters. The inflow of Persian Gulf Water does not significantly influence the hydrography of the northwestern Arabian Sea along the Omani coast. Nitrate has a high inverse correlation with temperature and oxygen in the premonsoon thermocline in the depth interval 50–150 m. During the southwest monsoon, coastal upwelling off Oman and adjacent offshore upward Ekman pumping alter the shallow hydrography.

Description: The results of ichthyoplankton surveys carried out by the Instituto Nacional de Pesca (INAPE) in the Argentine–Uruguayan Common Fishing Zone (AUCFZ) in summer 1980 and the winters of 1980–1982 are presented. In addition, the results of joint research with INIDEP, the Argentine and Japan Fisheries Agency, on larvae, juveniles and adults of the short-finned squid Illex argentinus carried out in winter 1989 are given, as are data obtained during the joint sardine and anchovy recruitment project carried out by R.V. Meteor in November/December 1989. The short-finned squid Illex argentinus is the most important cephalopod resource of the area, and an extended fishery is carried out on the Patagonian shelf and in the proximity of the Falkland Islands. The fishing season in the AUCFZ, for pre-spawning and spawning animals, extends from early autumn to winter (March–August). Abundance of rhynchoteuthion larvae (417–485 larvae·10 m−2) was greatest in winter in surface temperatures of 12,1–16,9°C and surface salinities of 34,8 – 35,2 × 10−3. The distribution of the larvae is related to the western boundary of the Brazil Current and the convergence front.

Description: The population size and breeding success of Emperor Penguins Aptenodytes forsteri at the Auster and Taylor Glacier colonies were estimated during the 1988 breeding season. At Auster a total of 10 963 pairs produced about 6350 fledglings for a breeding success of 58%. At Taylor Glacier about 2900 pairs raised 1774 fledglings for a breeding success of 61%. Fledglings left Taylor Glacier over a period of 33 days at a mean mass of 10.56 kg.

Description: This paper presents an idea on the possible structuring effect of hex actinellids on Antarctic sponge associations. To this end, information derived from underwater photography performed on the eastern Weddell Sea shelf is reported and original trawl data are presented. Underwater photography shows the existence of different sponge associations; species poor associations are connected to soft bottom, species rich associations exist on substrates characterized by bryozoan debris and especially sponge spicule mats. The trawl. catches show differences in the population structure of a hexactinellid sponge, Rassella racovitzae Topsent at two stations, distinguishable from each other by substrate structure. On average small and therefore probably young specimens were found on bryozoan debris, while a population with larger and probably older specimens was found on solid hexactinellid spicule mats. These observations form the basis for the hypothesis that hexactinellid sponges are a major biological structuring agent for Antarctic sponge associations; they colonize soft substrate and bryozoan debris dominated areas and subsequently change the quality of the substrate by spicule deposition. The ensuing spicule mats are a suitable settling ground for a large number of demosponge species dependent on hard substrates. Mass occurrences of hexactinellids are also found in areas other than Antarctica. The phenomenon recognized in the Weddell Sea probably occurs more widely spread.

Description: A method is proposed for cloud detection over sea using a single infrared channel of a high spatial resolution satellite radiometer. The method combines a spatial coherence test and an absolute threshold test for the temperature field. The threshold for the second test is automatically determined by a histogram analysis of data which were preselected by the coherence test. The coherence test used differs from the classical standard deviation test in the way of the test value computation: the weight of the pixel to be investigated is increased. A simulation shows that under conditions of low cloud cover this makes the proposed coherence test more sensitive than the standard deviation test. When applied to real data the test was also found to be very sensitive compared with visible and IR threshold tests. Cloud cover obtained by the whole method is finally compared with that resulting from the visible and IR histogram analysis procedure of Phulpin et al. This comparison indicates a high reliability of the proposed method.

Description: The diets of 20 species of smaller Odontoceti were investigated. The material was collected along the southern African coast between 1966 and 1990 and included 158 strandings, 29 animals killed incidentally and 49 animals caught under permit. In total, 57 species in 34 families of fish and 89 species in 24 families of cephalopods were identified from remains in the 236 stomachs investigated. Most Odontoceti fed on commercially unexploited cephalopods and fish, or on fish below commercially utilized sizes. However, the average sizes of anchovy and pilchard eaten by Delphinus delphis and Lagenorhynchus obscurus were larger than the sizes most frequently taken commercially. The species composition of the prey items reflected the onshore-offshore distribution (and possibly the foraging depths) of different Odontoceti. Tursiops truncatus and Cephalorhynchus heavisidii were closest to shore and D. delphis and L. obscurus over the continental shelf. The rest were distributed around the shelf-edge and just off the edge. A comparison of the stomach contents of stranded and non-stranded D. delphis, L. obscurus and C. heavisidii demonstrated that results from stranded animals are biased.

Description: Seafloor survey instruments are integral to the study of marine geology. Because understanding their resolution and limitations is critical, we compare how different survey systems represent the seafloor. Coincident data collected at the Galapagos propagator (GLORIA, SeaMARC II, Sea Beam, Deep-Tow, camera sled, and Alvin) allow comparisons of how well seafloor features (e.g., faults and volcanoes) observed and characterized in high resolution data are represented in lower resolution, coarser-scale data sets. Our reported values for the minimum sizes of detected and well-represented features show that practical geological resolutions are generally ∼2-10 times lower than theoretical resolutions; care must be taken in evaluating which system to use to address a particular problem.

Description: The community of benthic organisms in the lower zone of a rocky shore at Praia Rasa, Brazil is distinctly patchy in structure. We examined the hypothesis that two types of patch (a. red algal turf and b. colonial coelenterate) represent different temporal stages in the same successional trajectory. We made observations on a) the stability of patch boundaries, b) successional sequence in experimental clearings within both patch types and c) species composition through time in undisturbed patches. In most cases, the coelenterate overgrew the algae at the patch boundaries, thus showing a competitive asymmetry. In the successional sequence, diatoms were followed by ulvoid species. Thereafter, within clearings in the algal patches, a red algal turf was once more established over one year. In contrast, the mid successional period in clearings within the coelenterate patch was characterized by very low cover of sessile organisms. Colonization by red algal turfs and by the coelenterate colony is largely dependent on vegetative spread. Thus later succession is not predictable on the basis of time alone. Supply-side processes are clearly of equal importance. Therefore it cannot be stated without qualification that patches of red algal turfs and colonial coelenterate at Praia Rasa are part of the same successional sequence.

Description: A vertical mixing model was applied to a location off the west coast of the South Island, New Zealand, with the aim of simulating the seasonal cycle of temperature and mixed layer depth in the region. Observed weather data for 1973–89 were used to drive the model. Model results for sea temperature and mixed layer depth were compared to measurements from ships, moored temperature sensors, and satellites. The main features of the variations in temperature and mixed layer depth can be explained by the local meteorological forcing and vertical mixing, together with a general southward flow in the study area. Superimposed are short‐term variations which are obviously related to variable currents and the associated horizontal heat transport.

Description: Sea level variations and geostrophic circulation in the western tropical Atlantic are studied in an intercomparison of Geosat altimetry and the World Ocean Circulation Experiment community model effort high‐resolution model forced with climatological windstress. Overall, the annual cycles of geostrophic current fields of both products compare very well. Special comparison areas are the western North Equatorial Countercurrent (NECC) and the North Brazil Current (NBC) region. Meridional profiles of zonal velocity anomalies show a seasonal meridional migration of the NECC core centered at 5°N and a weaker eastward maximum during fall at 9°N in both products. The Geosat and model seasonal cycles of the NECC core velocity in the region 35°–45°W are highly correlated and agree with respect to the onset of eastward current acceleration and deceleration in May and December, respectively. Geosat time series from November 1986 to June 1989 show year to year differences, in particular an anomalous early NECC acceleration phase in 1987. In the NBC region 54°–58°W, flow anomalies from both Geosat and the model have two westward maxima, in March and June, which appear to be associated with eastward anomalies further offshore.

Description: Specimens of Siboglinum poseidon were collected by box coring and studied together with their undisturbed habitat. Occupied tubes occur in depse aggregations beneath the sediment surface directly at methane seep sites. Fertilized eggs develop into small larvae within the anterior transparent region of the tube. The oldest larvae observed in tubes measure c. 370 µm in length. It is concluded that released larvae develop in the sediment in the oxygenated top layer. Three tube types have been found: 1, the larval envelope; 2, the juvenile, transparent tube and 3, the ringed, adult tube. The smallest specimens recovered from the sediment measure c. 2 mm. They are complete with a tentacle, pyriform glands, bacteriocytes and juvenile opisthosoma. Some larvae were reared under laboratory conditions for 10 weeks. At that stage red blood becomes visible and a small tentacular bud is formed dorsally.

Description: Kanechlor-300, -400, -500 and -600, Phenoclor DP-3, -4, -5 and -6 and Sovol mixtures were analyzed for their chlorobiphenyl (CB) composition using high-resolution one-dimensional and multidimensional gas chromatography-electron capture detection (MDGC-ECD) techniques. The congener patterns of tested Kanechlor and Phenoclor mixtures resembled Aroclor 1016, 1242, 1254 and 1260. However, differences in the percentage contribution of minor constituents were noticed among these mixtures, which could be due to variations in the boiling-point fractionation of these commercial products. CB pattern of Sovol was different from the rest of the mixtures tested. It showed a composition in between ca. 30%, 40%, 50% and 60% overall chlorine levels. MDGC-ECD study showed the presence of hitherto unnoticed non-CB compounds coeluting with CBs in some commercial PCBs. The use of these mixtures as quantitation standards should be considered with caution. CB patterns of Sovol and a water extract of the Gulf of Finland matched closely, indicating a point source contamination to these waters.

Description: A series of field experiments has been made to determine the occurrence of small-scale surface motions that might enhance gas exchange by surface renewal. Out of 93 runs under natural conditions on open bodies of water, only 19 gave no indication of surface streaming within a few seconds. The data cover the wind speed range up to about 6 ms-1. Above 2 or 3 ms-1, predominately line structures were observed. This points to an important r6le of surface renewal in gas exchange.

Description: We use atmospheric and ice core data on the concentrations of nitrous oxide to estimate that the present global anthropogenic emissions are 7±1 tg/yr. If the atmospheric lifetime of N2O is a hundred years or more, this estimate is virtually independent of the actual lifetime. The natural sources are estimated to be about 15 tg/yr. We also find that nitrous oxide started increasing rapidly only during the last century. The trends over the last decade are extremely variable; over 3-year periods the trends have ranged from 0.5 ± 0.2 parts per billion by volume (ppbv/yr) to 1.2 ± 0.1 ppbv/yr. The average rate of increase is about 0.80 ± 0.02 ppbv/yr or 0.27 ± 0.01 %/yr (1977–1988). There is an indication that N2O may be increasing faster in recent years than during the middle 1970s by about 0.2 ± 0.1 ppbv/yr. It is likely that several small anthropogenic sources may be causing the present trends, all emitting between 0.1 and 1.5 Tg/yr.

Description: We used sediment traps to define the particulate fluxes of barium and organic carbon and investigate the use of barium as a proxy for ocean fertility. Strong correlations between Corg and Ba fluxes indicate a link between upper ocean biological processes and barium flux to the seafloor. The ratio of organic carbon to barium decreases systematically with water depth. Data from 10 sites indicate that organic debris settling from the 200-m depth has a Corg /Ba ratio of approximately 200. The systematic decrease in this ratio with increasing water depth results from the simultaneous decay of organic matter and uptake of Ba in settling particles. This behavior provides additional evidence that the formation of barite in oceanic particles is a consequence of decomposition/uptake in microenvironments rather than the secretion of barite by specific organisms. The decrease of the Corg/Ba ratio with depth is greatest in the North Pacific followed by the equatorial Pacific and is lowest in the western Atlantic. Since this spatial pattern is consistent with the variations in the deep-ocean barium contents which increase along the path of bottom water flow from the Atlantic to the North Pacific, it suggests that the particulate barium uptake and flux is enhanced by higher barium contents in the intermediate and deep waters of the ocean. Consequently, we have combined our particle flux data with existing water column Ba data to define an algorithm relating new productivity, dissolved barium contents, water depth, and particulate barium flux. This relationship provides a basis of applying barium flux measurements in sediments to estimating new production. In order to use barium as an indicator of productivity, it will be necessary to evaluate inputs from hydrothermal and aluminosilicate sources and xenophyophors. The application of a sequential leach procedure to the trap material indicates that 50-70% of the Ba in settling particles is in the form of barite and the remaining is adsorbed or bound to carbonates. Normative analysis demonstrates that in nearshore areas the contribution of barium from aluminosilicate sources can dominate that from biogenic inputs. It appears that normative estimates of biogenic barium contents can be made with accuracy if less than 50% of the Ba is associated with aluminosilicates; i.e., is of terrigenous origin. Since diagenetic mobilization of Ba can occur in reduced and suboxic sediments, highly productive nearshore areas also are likely to be inappropriate sites to use Ba measurements as productivity indicators. Comparisons between the rain rates of particulate Ba to the seafloor and the burial rate indicate that approximately 30% of the Ba rain is preserved. Although the preservation factor does not appear to be constant, it may be possible to predict the extent of preservation from an empirical relationship with the mass accumulation rate. These observations indicate that measurement of Ba burial fluxes in sediments can provide quantitative information on the paleoproductivity of the oceans. Joining the relationship between barium rain and burial with the barium and organic carbon algorithm, we make estimates of the new production in the northern California Current during the last 18,000 years. This calculation suggests that new production was at least a factor of 2 lower at this site during the last glacial maximum.

Description: The Guinea Dome is a permanent, quasi-stationary feature on the eastern side of the thermal ridge extending zonally across the tropical North Atlantic. The dome is a part of the large-scale near-surface flow fields associated with the North Equatorial Current, the North Equatorial Countercurrent and the North Equatorial Undercurrent. In the present study, historical and recently obtained hydrographic data are combined to investigate the thermohaline structure and geostrophic flow field in the vicinity of the dome. It is shown that the Guinea Dome exists throughout the year both in subthermocline and thermocline layers, that it has a corresponding cyclonic geostrophic flow, and that seasonal changes occur with respect to its vertical structure, horizontal extent, and position. The observational results are then compared with simulations from a general circulation model of the tropical Atlantic. A seven-year simulation forced by observed monthly winds is run to compute a monthly climatology. The model adequately simulates the Guinea Dome with respect to its structure, flow field, and seasonal variability.

Description: The North Pacific is a sea area of primary interest to Russia, which inherited key strategic interests of the former Soviet Union. But the North Pacific has also become an area of increasing resource exploitation activity. These factors lead to an even more active involvement in regional political relations. The article touches on a number of most urgent, controversial, and still unsolved issues faced today by the Russian Federation. The author concentrates on two major problems: the issue of international fisheries in the so‐called doughnut hole (located in the central Bering Sea), and the highly controversial questions of marine spaces delimitation between Russia on one side and Japan (which raises a more general political question of sovereignty over the four southernmost islands of the Kuril chain) and the United States on the other.

Description: Bottom-simulating reflectors (BSR) are observed commonly at a depth of several hundred meters below the seafloor in continental margin sedimentary sections that have undergone recent tectonic consolidation or rapid accumulation. They are believed to correspond to the deepest level at which methane hydrate (clathrate) is stable. We present a model in which BSR hydrate layers are formed through the removal of methane from upward moving pore fluids as they pass into the hydrate stability field. In this model, most of the methane is generated below the level of hydrate stability, but not at depths sufficient for significant thermogenic production; the methane is primarily biogenic in origin. The model requires either a mechanism to remove dissolved methane from the pore fluids or disseminated free gas carried upward with the pore fluid. The model accounts for the evidence that the hydrate is concentrated in a layer at the base of the stability field, for the source of the large amount of methane contained in the hydrate, and for BSRs being common only in special environments. Strong upward fluid expulsion into the hydrate stability field does not occur in normal sediment depositional regimes, so BSRs are uncommon. Upward fluid expulsion does occur as a result of tectonic thickening and loading in subduction zone accretionary wedges and in areas where rapid deposition results in initial undercconsolidation. In these areas hydrate BSRs are common. The most poorly quantified aspect of the model is the efficiency with which methane is removed and hydrate is formed as pore fluids pass into the hydrate stability field. The critical boundary in the phase diagram between the fluid-plus-hydrate and fluid-only fields is not well constrained. However, the amount of methane required to form the hydrate and limited data on methane concentrations in pore fluids from deep-sea boreholes suggest very efficient removal of methane from rising fluid that may contain less than the amount required for free gas production. In most fluid expulsion regimes, the quantity of fluid moved upward to the seafloor is great enough to continually remove the excess chloride and the residue of isotope fractionation resulting from hydrate formation. Thus, as observed in borehole data, there are no large chloride or isotope anomalies remaining in the local pore fluids. The differences in the concentration of methane and probably of CO2 in the pore fluid above and below the base of the stability field may have a significant influence on early sediment diagenetic reactions.

Description: Results are presented following a long-term study of the diet of the Cape gannet Morus capensis at Bird Island, Algoa Bay, examining 4 178 regurgitations representing 36 351 prey items collected during 12 breeding cycles from April 1979 to March 1991. In all, 32 teleost and two cephalopod species were recorded. The pelagic shoaling pilchard Sardinops ocellatus, anchovy Engraulis capensis and saury Scomberesox saurus scombroides were identified as the main prey species. The diet composition showed marked interannual fluctuations during the sampling period, which appear to be related to changes in the abundance of the main prey species. The relative abundance of pilchard, anchovy and saury was also found to change intra-annually, the first two species occurring more frequently in the diet during the breeding season and saury dominating the diet in the non-breeding season. These changes are thought to originate from temporal variation in the oceanographic regime within the foraging range of the gannets.

Description: Six species of skates were trawled commonly on the continental shelf off the Southern Cape during routine surveys of demersal fish between 1986 and 1990. Raja miraletus is a small skate found principally in shallow (〈50 m) water that feeds mainly on small crustaceans, such as mysids and macrurans. The large Raja alba occurs over most of the continental shelf, is a piscivore throughout its life and preys heavily on flatfish, especially Cynoglossus zanzibarensis. R. cf. clavata is ubiquitous on the shelf but most abundant between 50 and 150 m deep. Feeding predominantly on crustaceans, this skate switches from carids, penaeids and mysids when small to brachyurans and small benthic fish when larger. R. pullopunctata is found over a similar depth range but attains a much larger size. It eats small mysids and macrurans when small, but brachyurans and fish become more important in the diet with increasing size of the predator. R. wallacei is most commonly taken at depths of 80–〉200 m, feeds initially on small crustaceans, but switches to fish, including eels, as it grows. The small Cruriraja parcomaculata is found at the edge of the continental shelf and over the upper slope; it preys on small crustaceans, including mysids, isopods and macrurans. The distribution pattern of the skates and their prey suggest overlap in prey taken, the overlap being greatest in those species which feed on crustaceans. The large biomass of skates in the area suggests that they are an important component of the demersal faunal assemblage of the continental shelf there, and also that they may have a significant impact on the benthic fauna.

Description: Mediterranean salt lenses (meddies) are a dominant factor in the salt budget of the Atlantic at middepth. In spite of their important role, their juvenile migration has not yet been directly observed. For the first time, two RAFOS float trajectories show strong evidence of a meddy along the Iberian continental slope off Lisbon. Over six weeks we obtained drift observations from two levels (629, 847 dbar). Both instruments recorded a series of loops with an azimuthal speed O (30 cm s−1) at a radius of about 25 km. Relatively high propagation speeds of several centimeters per second indicate the meddy was probably carried along with the undercurrent of Mediterranean Water. The Tejo Plateau, a prominent feature of the continental slope and a natural obstacle for the spreading Mediterranean Water tongue, appears to act as a deflector for advected meddies possibly formed by interaction of the undercurrent with the canyon-rich topography farther south.