Description: A total of 131 current meter records of between 6 and 24 month duration are analysed to describe the deep flow field of the eastern North Atlantic from 19° to 54°N and from the Continental Slope to the Mid Atlantic Ridge. Mean flows are weak and may be statistically indeterminate in some records and locations, but appear to indicate cyclonic circulations around the Iberia and Porcupine abyssal plains with a generally southward flow along the Mid Atlantic ridge and a deep northward slope current (where measurements exist) along the eastern boundary. The deepest inflow to the north-eastern basin that has been identified to date takes place through the Discovery Gap of 〉4,700 m sill-depth at 37° 25′N 15° 45′W in the Azores-Portugal ridge. South of that ridge, observations are sparse and no systematic circulation is yet evident. These observations are discussed in relation to recent geostrophic estimates of the deep circulation.

Description: Water samples and suspended matter taken in the Atlantis-II Deep area (Red Sea) during the expedition SO-2 (with RV “Sonne”) in November 1977 were investigated for chemical composition. Only slight changes have been found for most components since 1966. A strong decrease of the Cu content (from 100–500 μg kg−1 according to Brooks et al., 1969, to values below 1 μg kg−1) has, however, become evident. Comparison between theoretical concentrations in the intermediate brine layers (resulting when using the lower or the upper homothermal layers, respectively, as end members of mixing processes with Red Sea deep water) and the concentrations measured prove that precipitation and resolution processes have considerable influence on the concentrations found in solution. Components strongly involved in such processes are: iron, manganese, copper, oxygen, sulfate, and silica, as could be shown from comparison of theoretical and measured concentration profiles along the water column. Investigations of the metals suspended in the brine confirm these processes. Compared to 1971/1972, the Cu and Zn values in suspension (preferring the southwestern basin at that time) are clearly reduced — thus being in agreement with the recently lowered hydrothermal activity. Remarks on the hypothetical composition of the unknown hydrothermal brine discharging into the deepest basin are also included.

Description: Plastically deformed quartzites from the Betic Movement Zone (Betic Cordilleras, Spain) exhibit microstructures indicative of crystal plasticity on a mineral grain scale. Quartzites with dynamically recrystallized grain sizes larger than 10 μm have strong crystallographic preferred orientations, narrow grain boundaries, little creep damage, and an inverse proportionality of dislocation density and grain size. Mylonites with grain sizes smaller than 10 μm have low crystallographic preferred orientations, wide grain boundaries (up to 1000 Å), abundant creep damage, and decreasing dislocation density with diminishing grain size. This is thought to reflect a clear-cut shift in deformational regimes from dislocation creep to superplastic flow at 10 μm grain size. Superplasticity can be acquired by quartzites which suffer dynamic recrystallization to grain sizes smaller than 10 μm during an initial dislocation creep stage. Dislocation motion is the major accomodating mechanism for strain incompatibilities that arise during grain-boundary sliding in the mylonites.It seems reasonable to estimate flow stresses from unbound dislocation densities and dynamically recrystallized grain sizes in the tectonite specimens. In the mylonites, dynamically recrystallized grain size probably reflects the stress magnitude before the shift in deformational mechanisms, and an estimate for late stage stresses is provided by unbound dislocation densities. In both deformational regimes the flow strength appears to depend on the extent of dynamic recrystallization.

Description: Hydrographic data from two cruises in the Canary Basin (Meteor 57, July 1981; Poseidon 86, April 1982) are analysed with respect to current distribution and lateral heat flux in the Azores-Madeira region. The first part of the data base consists of long transects of XBT and G.E.K. measurements between Cape Finisterre (North West Spain) and the northern Canary Basin, where several year-long current meter records exist. Further information is obtained by thermosalinograph surface data and by expendable current profilers (XCP). Geostrophic currents are derived from XBT profiles, using the tight temperature-salinity relationship in the depth range of the Warmwassersphäre. The results compare well with the G.E.K. and XCP current observations. The second part consists of CTD data from an eddy resolving, box-shaped CTD survey (500 × 500 km2) centered at the mooring location (33°N, 22°W), The observations are supplemented by satellite-buoy trajectories. Horizontal parameter distribution is shown in terms of objectively contoured maps. Bands of spatially enhanced energetic structures, seen in the long transects are further resolved by the box survey as a deep jet-like current system cross the Canary Basin in a west-east direction. Associated with this Azores Current is a frontal zone with near-surface temperature and salinity steps of order 2 K and 0.3 practical salinity units. The dynamic topography field can be decomposed into a linear background field, a Rossby wave and a mesoscale eddy field. We find that major contributions to the meridional eddy heat flux are confined to the vicinity of the Azores current frontal zone. It is shown that the principal balance in the temperature equation is between heating by the mean horizontal advection terms and cooling by the eddy flux divergence.

Description: A primitive equation equatorial model has been developed to study climate variability due to wind and thermodynamic forcing in an equatorial region. The model basin extends from 30° S to 30° N and zonally over 140°, has a variable horizontal resolution (50–800 km) and 13 vertical levels. Experiments are performed with observed annual cycle as well as 32 years of observed bimonthly wind data. A preliminary analysis of these experiments shows that the model is capable of simulating the basic pattern of annual as well as interannual variability of the Pacific Ocean. In particular, the model response shows evidence of the major El Niños which occurred between 1947 and 1978.

Description: Small-volume (ca. 0.6 km3) pyroclastic flow deposits at Laacher See contain lithic breccias and two types of ground layers that differ significantly in their structure and composition from the main body of flow units. Lithic breccia bodies, up to 3.5 m thick, containing up to 85 weight% lithic blocks, occur locally at various distances from the vent. The deposition of these breccias was apparently governed by the strong influence of paleomorphology on the dynamics of the pyroclastic flows. The breccias were deposited at three main changes in bottom gradient along the path of the pyroclastic flows. The accumulation of large lithics is explained: (a) by compression of flows on the rising bottom close to the vent; (b) by thinning of flows accelerating over a steep incline; (c) by deceleration of the pre-concentrated lower part of flows in hydraulic jumps; and (d) possibly by a stationary vortex at the inner bend of a valley curvature. Poorly sorted lithic-rich ground layers, laterally highly variable in internal structure and composition, are restricted to marginal regions of the pyroclastic flow deposits within deep and narrow valleys. They are interpreted as having formed due to the extreme roughness of the valley walls, enforcing irregular turbulent flow and intense fluidization of the flow head, in which density-dominated segregation of lithics occurred. Wellsorted lapilli-rich ground layers of constant lateral thickness were probably generated by a more regularly moving, less intensely fluidized head of pyroclastic flows in which size-dominated segregation was effective but density-segregation was minor. A model of the temporal and longitudinal evolution of a flow head is proposed. Close to the vent, the head is exclusively erosive. With increasing distance, erosive power declines and erosion is paralleled by ground layer formation under strong fluidization. Further from the vent, the head ceases to erode while fluidization is still sufficient for ground layer formation. When fluidization declines to a level ineffective for segregation, ground layers terminate while the head advances and only terminates when plug-flow dominates.

Description: Molluscan fossils collected from shallow water marine sediment across NW Europe and nearby Arctic regions have been analysed for the extent of isoleucine epimerization (DL ratio) in indigenous protein residues. The DL ratios confirm that essentially all ‘classical’ Eemian sites from NW Europe are of the same age, and are correlative with the type locality near Amersfoort in the Netherlands; shells from interglacial marine sediment beneath the type Weichselian till in Poland also correlate with the type Eemian site. DL ratios in Holsteinian marine shells (0.29) are substantially higher than in their Eemian counterparts (0.17); ‘Late Cromerian’ shells yield even higher ratios (0.46). DL ratios in late glacial shells (0.06) and Middle Weichselian shells (0.09) permit differentiation from modern (0.01) and last interglacial material. Based on the position of the Matuyama-Brunhes boundary and the differences in DL ratios, the Eemian must correlate with isotope substage 5e, whereas the Holsteinian is most likely substage 7c, possibly stage 9 but certainly younger than stage 11. Intra-Saalian warm periods may be terrestrial equivalents of the younger substages of stage 7. Extensive pre-Eemian marine sediments along the SW coast of Denmark previously correlated with the Holsteinian are shown to be of ‘Late Cromerian’ age. The underlying till there is the first widespread evidence of a pre-Elsterian till in NW Europe. DL ratios in molluscs from last interglacial sites along the Arctic coast of the USSR, the Arctic Islands and eastern Greenland are substantially lower than in their European counterparts due to their low thermal histories. The combined mid- and high-latitude data are used to develop a predictive model for the expected DL ratio in any of several moderate epimerization-rate taxa for last interglacial sites with mean temperatures between −20 and +15°C. Not all sites could be unambiguously assigned to an established interglacial. The Fjøsanger (Norway) and Margareteberg (Sweden) sites previously thought to be Eemian, yield DL ratios higher than in secure nearby Eemian material. It is yet unresolved whether these are aberrant sites or if they predate the last interglacial. In situ shoreline deposits encountered in borings in SW Belgium and in exposures on the Belgium coastal plain contain molluscs that yield DL ratios intermediate between secure Eemian and Late Weichselian ratios, raising the possibility that a late stage 5 high-sea-level event attained near-modern levels in the southern North Sea basin. Resolution of these uncertainties is the focus of future work.

Description: The potential vorticity profile in the seasonal pycnocline can be predicted from the surface buoyancy and momentum fluxes by means of the Lagrangian correlation of seasonally varying mixed-layer depth and density. Water flows geostrophically from the seasonal pycnocline into the permanent pycnocline, through the sloping surface of depth D defined by the annual maximum depth of the mixed layer. Potential vorticity flows into the permanent pycnocline where U(D)· ∇D ≤W(D) and vice versa. A theory is given for the regional variation of D, and methods of determining D from hydrographic data are reviewed. This physical understanding of potential vorticity sources and sinks makes it possible to reformulate ventilated thermocline models in terms of flux rather than density boundary conditions, and guides the design of coupled models of ocean—atmosphere circulation. It leads to formulae for water-mass formation and the nutrient balance in the seasonal boundary layer.

Description: The concentrations of nine rare earth elements (REE) La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb, have been determined in mixed species assemblages of foraminifera tests taken from Atlantic Ocean sediment core tops. Reductive cleaning techniques have revealed that REE are present in three phases in foraminifera tests collected from sea floor sediments; REE included in the foraminiferal calcite matrix (termed lattice REE), REE associated with an authigenic FeMn-rich phase adsorbed onto the surface of the test following the death of the organism (termed coating REE) and REE associated with alumino-silicate detritus (termed detrital REE) which commonly infills the test chambers after burial in the sediment. The concentrations of REE in the nondetrital (lattice plus coating) and lattice phases have been measured in this study. Approximately 90% of the REE measured in the non-detrital phase reside in the coating phase, the remainder being present in the lattice phase. These data have been used to investigate the relationship between the distribution of dissolved REE in the ocean and in the coating and lattice phases. In addition to the REE the concentrations of Mn, Fe, Cu, Al and PO4 have been measured as an aid to characterisation of the various phases.