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 data presented provides new information on the distribution of Antarctic squids and on the summer diet of the emperor penguins. The diet of 58 adult emperor penguins (Aptenodytes forsteri) on the fast ice of the Drescher Inlet, Vestkapp Ice Shelf (72°52′S, 19°25′W) in the eastern Weddell Sea was investigated. Prey consisted principally of squid, fish, krill, amphipods and isopods. Squids were identified by the lower beaks and allometric equations were used to estimate the squid biomass represented. Beaks occurred in 93% of the stomach samples. Each sample contained a mean of 27 beaks (range 1–206). Ninety-two percent of the squids could be identified by the lower beaks and belonged to four families (Onychoteuthidae, Psychroteuthidae, Neoteuthidae and Gonatidae). The most abundant squid was Psychroteuthis glacialis which occurred in 52 samples with lower rostral lengths (LRL) ranging from 1.4–7.2 mm. Forty-five samples contained Alluroteuthis antarcticus (LRL range 1.8–5.8 mm), 17 Kondakovia longimana (LRL range 4–12.1 mm), and four Gonatus antarcticus (LRL range 4.1–6.1 mm). In terms of biomass K. longimana was the most important species taken by the penguins comprising 50% of total estimated squid wet mass (245348 g) in 1990 and 48% in 1992 (154873 g). However, if only fresh beaks were considered for estimations of squid consumption, i.e. beaks that have been accumulated for not longer than 5–6 days in the stomachs, squid diet was of minor importance. Then total squid wet mass accounted for only 4809 g in 1990 and 5445 g in 1992 which implies that one penguin took c.30 g squid d−1 with P. glacialis and A. antarcticus being the most important by mass. The prey composition suggests that emperor penguins take squid at the steep slope regions of the eastern Weddell Sea.

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: During a study based on catches taken in the northern North Sea by selected Scottish fishing boats during 1985–1992, large numbers of the normally rare short-fin squid, Todaropsis eblanae (Cephalopoda: Ommastrephidae), were recorded in 1987 and 1990. Our findings, supported by data obtained from plankton/young fish surveys in 1988 and 1989, suggest that in northern waters Todaropsis eblanae generally mates and spawns during late summer and early autumn (June-November). Successful hatching events appear to occur during October-March, producing juvenile (stage I) squid in the early part of the year (January-June). Estimations of maximum male reproductive output and female fecundity were up to 130 spermatophores and ~28,000 eggs per individual, respectively.

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: 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 cause of decadal climate variability over the North Pacific Ocean and North America is investigated by the analysis of data from a multidecadal integration with a state-of-the-art coupled ocean-atmosphere model and observations. About one-third of the low-frequency climate variability in the region of interest can be attributed to a cycle involving unstable air-sea interactions between the subtropical gyre circulation in the North Pacific and the Aleutian low-pressure system. The existence of this cycle provides a basis for long-range climate forecasting over the western United States at decadal time scales.

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: 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: 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: The functional morphology of the buccal mass of 23 species of cephalopod (Octopoda, 4 species; Teuthoidea, 17; Sepioidea, 2) was investigated by gross dissection, histology and observations on fresh preparations. Cephalopod beaks lack a joint or articulation point. The jaws slide and rotate around an area rather than a fixed point. During closing the superior mandibular muscle (SMM) provides the force of a bite and the largest movement vector, whilst the inferior mandibular muscle (IMM) acts to retract the upper beak, causing shearing action. Dorsal portions of the lateral mandibular muscles (LMM) flex the upper beak walls outwards, probably to accomodate the backwards sweep of the radula and buccal palps during closing. To open the beaks, the ventral portions to the lateral mandibular muscles pull the rear lateral walls of the two beaks towards each other, moving the lower beak back relative to the upper. The buccal mass weighs more in decapods (0.65-4.34% of body weight) than octopods (0.49-0.77%). The weight difference is mainly accounted for by the size of the superior mandibular muscle. Beak shape and muscle volume are related. Increasing the size of the upper beak hood and lateral wall area results in larger SMM and LMM respectively Increasing hood size in the lower beak increases IMM size, and altering the angle by which the wings meet the lateral wall changes the volume of the SMM and LMM. To accomodate the decapod pointed upper rostrum, the lateral walls of the lower beak have shortened in length, whilst increasing in breadth and surface relief to maintain the area available for muscle insertion. In species with a lateral wall ridge or fold (e.g. Onychoteuthis) this may mark the insertion point of the LMM.

Description: Arm autotomy was induced in a living specimen of Metacrinus rotundus (Echinodermata: Crinoidea). An arm was autotomized at a ligamentary articulation known as a cryptosyzygy, following incision by scissors distal to the break point. Although sessile stalked crinoids cannot entirely escape from a predatory attack by arm autotomy and they do not have an active defense, arm autotomy at cryptosyzygies reduces damage and arm loss by effective distribution, and by minimizing trauma and facilitating subsequent regeneration. The paradigmatic distribution of cryptosyzygies in which arm loss is set at a minimum, compared with the actual distribution, shows that these two patterns are similar and that actual specimens successfully reduce arm loss by the effective distribution of cryptosyzygies. The crinoid branching pattern also affects arm loss, and two different paradigms are discussed: anti-predatory and harvesting. Arm branching patterns of various isocrinids have tended toward the anti-predatory configuration from the Jurassic to the Recent, suggesting that the isocrinids have coped with increased predation. Shallow-water comatulids generally adopt the anti-predatory paradigm in their branching pattern, whereas many deep-water, stalked crinoids adopt a harvesting paradigm, reflecting that shallow-water comatulids receive more predatory attacks than do deep-water crinoids.

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: 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: 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 stomachsof 23 striped dolphins (Stenella coeruleoalba Meyen, 1833, Cetacea), stranded along the Ligurian coast (western Mediterranean Sea), contained 32 species of cephalopods, crustaceans and fishes, totalling an estimated 2,723 prey specimens representing about 36 kg in weight. Cephalopods and bony fishes were equally important in the diet (50%). Todarodes sagittatus (34.5%) and Micromesistius poutassou (25.9%) were found to be the most important food species. Other species belonging to six cephalopod families, three crustacean families and nine bony fish families, contributed to the diet with variable numbers, weights, and occurrences, demonstrating the opportunistic character of striped dolphin feeding.

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: Samples of two loliginid squids Alloteuthis africana and A. subulata were collected from the continental shelf off the west Sahara in August-September 1987. Statoliths were taken from 124 specimens and processed using statolith ageing techniques. Statoliths of both species were very similar in shape. In the ground statolith, growth increments were examined and grouped into four growth zones distinguished mainly by the width of the increments. Age of adult mature males of both species did not exceed eight months, that of females six months. Alloteuthis africana grew faster than A. subulata in weight and, particularly, in length. At age 180 d the mantle of A. africana was twice as long and the body weight 1·2–1·5 times as large. Both species matured over a wide range of sizes and ages (from 120 to 180 d). The life span of A. africana and A. subulata hatching between January and May on the west Saharan shelf is about six months, much shorter than that of A. subulata in its northern temperate range.

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: Statoliths of Loligo gahi were sampled in the fishery region 45–47°S on the Patagonian shelf during September 1989. Peculiarities of the growth zones in the ground statoliths of adults are described. Maximum age of large maturing and mature females (130–160 mm of mantle length, ML) was estimated to be 325–345 d, that of large mature males (250–290 mm ML) ranged from 360 to 396 d. The squid Loligo gahi d'Orbigny, 1835, occurs in temperate shelf and upper slope waters of the Atlantic and Pacific coasts of South America and is caught commercially by the international fleet in the southern part of the Patagonian shelf within the Falkland Islands Interim Conservation Zone (FICZ) (Roper et al., 1984; Csirke, 1987). Occasionally, dense shoals of L. gahi appear in the fishery region 45–47°S off the Exclusive Economic Zone of Argentina (EEZA) and have been caught in significant numbers by trawlers at depths of 120–150 m in September-October (Chesheva, 1990). Loligo gahi is a medium sized loliginid; in Falkland waters males attain 350 mm ML, females 210 mm ML (Hatfield, 1991), while in the fishery region 45–47°S maximum size is 260 mm and 160 mm, respectively (Chesheva, 1990). Patterson (1988) revealed two Falkland spawning stocks of L. gahi of unclear status, spring-spawners and autumn-spawners (austral seasons) and pointed out that the life span of squid of each stock lasted ~1 y. Recently Hatfield (1991) used statoliths to elucidate Patterson's (1988) estimations of age and growth of Falkland stocks of L. gahi and confirmed the 1-y duration of L. gahi's life span.

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: 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: Outer membrane (OM), cytoplasmic membrane (CM) and intracytoplasmic membranes (ICM) from the halophilic phototrophic purple sulphur bacterium Ectothiorhodospira mobilis 9903 were purified and characterized. The three membrane fractions were significantly different in regard to protein profiles on SDS-PAGE, and to the composition of amino acids, fatty acids and lipids. The presence of lipoproteins, the occurrence of lyso-phosphatidyl-ethanolamine and an increased content of saturated and short-chain fatty acids are characteristic properties of the OM. CM and ICM fractions are different on the basis of buoyant density, of protein profiles and amino acid composition, and due to the presence of succinate dehydrogenase activity in CM. In addition, CM and ICM showed significant differences in pigment content and absorption spectra.

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: Long-range global climate forecasts were 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 seven large climatic events of the 1970s to 1990s by this technique are in good agreement with observations over many regions of the globe.

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: Within the Western Ross Sea, there are six emperor penguin colonies of widely different size that occur exclusively on sea ice. In 1990 a survey of all six sites, two by close overflights and four from the ground, showed that the breeding habitats were highly variable. The most important physical characteristics of these habitats appear to be stable fast ice, nearby open water, access to fresh snow, and shelter from the wind.

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: The groundmass of andesitic dykes at Sezaki, southwest Japan, has trachytic texture and contains microscopic shear zones. The shear zones comprise a conjugate pair formed by flattening of the solidifying dyke rock, probably caused by the magma pressure of the still molten part of the dyke. This pressure shortened the solidifying rock perpendicular to the dyke margins and caused it to extrude parallel to the magma flow direction. The groundmass shears indicate that locally the magma flowed 60° upward in the dykes. It is concluded that while groundmass shears are a useful indicator of flow direction in dykes, phenocryst alignment in dykes is strongly influenced by magma-pressure flattening and thus may be a poor indicator of flow direction.

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: Age and growth were estimated in the European squid, Loligo vulgaris, by examining growth increments in the statoliths of 203 specimens collected from off the French Mediterranean coast. Length and increment data were analyzed assuming that the increments were formed daily. The relationships between age and length showed that: growth rate varied considerably among individuals; growth was double exponential; the squids grew on average to 240 mm ML at 240 d from hatching, with a maximum of 350 mm at 240 d; the life span is probably about one year.

Description: Some of the limits to the use of serology to identify prey species in the digestive tracts of cephalopods have been evaluated. Cuttlefish, Sepia officinalis, were given meals of krill slurry (Euphausia superba). Protein extracts of contents from four regions of the digestive tract, stomach, caecum, digestive gland and intestine, were tested for prey antigenicity. Digestion times (loss of antigenicity) ranged from 1 to 8 h depending on sampling site. Stomach and caecum emptied rapidly, but meal antigenicity persisted longer in the digestive gland. The Sepia experiments provide a basis for interpretation of results from natural predation by cephalopods).

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: Samples of female lllex argentinus were taken from the catch of a Japanese squid jigging vessel on the Patagonian Shelf during March 1986. Morphometrics of the somatic and reproductive organ systems and the histological structure of the mantle in relation to maturation were examined. The data suggest that growth and maturation occur simultaneously during most of the time that lllex argentinus females are on the feeding grounds. In a squid of a ‘standard’ mantle length the whole body mass increases relative to mantle length during maturation and growth of the reproductive organs. This is accompanied by a small but significant decrease in the relative mass of the mantle, head and viscera whilst the mass of the digestive gland remains constant. Although mantle mass of a ‘standard’ female squid decreases relative to mantle length with maturity this is not associated with degeneration of the mantle muscles. Energy and nutrient resources for maturation are apparently derived from the squid's food, not from reserves, and during the course of maturation there is an increasing shift of emphasis from somatic growth to production of gonad and accessory reproductive organs.

Description: The timing of spawning and recruitment in the squid Loligo forbesi in Scottish waters is described on the basis of data from three sources: monthly samples of squid caught by commercial trawls (1986–1988), egg masses found by fishermen (1987–1991), and statistical data on animals caught by research trawls (1978–1987). Spawning females were present in samples from December to June, with peak spawning occurring in March. Most records of egg masses were from these months, but eggs were also found in August and September. These results suggest that there is an extended spawning season. Small squid (≤100 mm dorsal mantle length) were rarely present in commercial samples, but were recorded in research samples almost all year round. Thus there appears to be more or less continuous recruitment into the catchable population. The results of the present study are consistent with published data from other parts of the geographic range in that there is a regular seasonal peak in spawning, and spawning adults disappear from the population in summer. Further interpretation of the life-cycle of this species is not justified on the basis of current knowledge, and more information is needed on migrations, geographical variation, and lifespan in Loligo forbesi.

Description: Cephalopod remains from the stomachs of a Risso's dolphin (Grampus griseus Cuvier, 1812, Cetacea) entangled in a fishing net off the Ligurian coast (central Mediterranean Sea) include squids Ancistroteuthis lichtensteini, Histioteuthis bonnellii, H. reversa and Todarodes sagittatus and the sepiolid Heteroteuthis dispar. All these cephalopods live in oceanic water including water over the steep continental slope where Risso's dolphin is frequently sighted. Histioteuthis reversa contributed 78% of the cephalopods by number, 81% of the wet weight and 73% of the dry weight and calorific value. The total calorific value of the cephalopods represented by lower beaks was 17,300 kj.

Description: The stomach contents of 235 specimens of the squid Sthenoteuthis oualaniensis (4·3–36·5 cm mantle length, ML) were examined. A detailed list of 60 species of prey, comprising young and adult squid, is given together with their frequency of occurrence and proportional contribution. The size and number of each food item was investigated. Three ontogenetic size-groups of S. oualaniensis were distinguished: I, fry and young (4–10 cm ML), micronektonic epipelagic plankton-eaters; II, transient critical size group (10–15 cm ML), converting from feeding on planktonic crustaceans and fish larvae to myctophid fishes; III, medium-sized (adult) nyctoepipelagic nektonic predators (15–36·5 cm ML), feeding primarily on myctophids and secondarily on squid. Myctophids (genera Symbolophorus, Myctophum and Hygophum) were the most abundant prey in the diet of adult S. oualaniensis from different parts of its distribution.

Description: Samples of male Illex argentinus were taken from the catch of a Japanese squid jigging vessel on the Patagonian Shelf during March 1986 and an analysis was carried out on the morphometrics of the somatic and reproductive organ systems in relation to maturation. The data show that growth and maturation occurred simultaneously during most of the time that Illex argentinus males were on the feeding grounds over the southern Patagonian Shelf. In a squid of a ‘standard’ mantle length the whole body mass increased relative to mantle length during maturation and this could be attributed to the increase in mass of the reproductive and accessory reproductive organs. During maturation the mantle and digestive gland mass showed no significant change relative to mantle length. The mass of the head increased and the mass of the viscera decreased relative to mantle length. In male Illex argentinus, as in the female, the energy and nutrient resources for maturation are derived from the squid's food and during the course of maturation there is an increasing shift of emphasis from somatic growth to production of gonad and accessory reproductive organs. The proportional investment of body mass in reproductive and accessory reproductive organs predicted for a fully mature male Illex argentinus was less than half that of the female.