Observations of the Labrador Sea eddy field

This paper is an observational study of small-scale coherent eddies in the Labrador Sea, a region of dense water formation thought to be of considerable importance to the North Atlantic overturning circulation. Numerical studies of deep convection emphasize coherent eddies as a mechanism for the lateral transport of heat, yet their small size has hindered observational progress. A large part of this paper is therefore devoted to developing new methods for identifying and describing coherent eddies in two observational platforms, current meter moorings and satellite altimetry. Details of the current and water mass structure of individual eddy events, as they are swept past by an advecting flow, can then be extracted from the mooring data. A transition is seen during mid-1997, with long-lived boundary current eddies dominating the central Labrador Sea year-round after this time, and convectively formed eddies similar to those seen in deep convection modeling studies apparent prior to this time. The TOPEX / Poseidon altimeter covers the Labrador Sea with a loose “net” of observations, through which coherent eddies can seem to appear and disappear. By concentrating on locating and describing anomalous events in individual altimeter tracks, a portrait of the spatial and temporal variability of the underlying eddy field can be constructed. The altimeter results reveal an annual “pulsation” of energy and of coherent eddies originating during the late fall at a particular location in the boundary current, pinpointing the time and place of the boundary current-type eddy formation. The interannual variability seen at the mooring is reproduced, but the mooring site is found to be within a localized region of greatly enhanced eddy activity. Notably lacking in both the annual cycle and interannual variability is a clear relationship between the eddies or eddy energy and the intensity of wintertime cooling. These eddy observations, as well as hydrographic evidence, suggest an active role for boundary current dynamics in shaping the energetics and water mass properties of the interior region.     

Regional development in the United States during the 1980s: population redistribution and economic restructuring

The reduction of the rate of growth of the Brazilian population from 3% in the 1960s to 2% by 1993 resulted from a significant reduction of fertility. According to the 1986 national maternal-child health and family planning survey (PNSMIPF) results, 43.3% of women were using some type of contraception: 65.6% of married or cohabiting women. Women relied most on sterilization (17.2%), followed by oral contraceptives (OCs) (17%), the rhythm method (2.8%), the condom (1.1%), and others (5.2%). Only in the south was OC use more prevalent (28.5%) than sterilization (12.2%). The proportion of sterilization reached 27.8% in the north/center-east urban regions. In urban areas sterilization averaged 18.7% vs. 12.7% in rural areas. 26.9% of currently married women in the age range of 15-44 years had been sterilized. A 1990 international estimation indicated that the proportion of sterilization amounted to 36.9% in China, 30.95 in India, 29.7% in Brazil, 47.6% in South Korea, 30.4% in Thailand, and 36.5% in the Dominican Republic. The 1986 PNSMIPF survey also indicated that sterilized women were better informed than other women about contraception. 75% of the former had used OCs, 5% had used the diaphragm, 3% the IUD, 30% the condom, and 35% coitus interruptus at one time or other. The sterilized women had an average of 1.7 more children than those who were using other methods of contraception. 48.6% of women were sterilized before the age of 30, when they had had an average of 3.6 children. 66.6% of the sterilized women who had given birth before the age of 20 had 4 or more live births as compared to 5.9% of sterilized women aged 30 with the same number of children. 47% of women without any schooling were using some kind of contraception vs. 77% of those who had completed secondary school. A multivariate analysis also showed that the age of the mother, the number of live births, the educational status of the mother, and family income were positively correlated with sterilization.     

The partial molar volume, thermal expansivity, and compressibility of H2O in NaAlSi3O8 liquid: new measurements and an internally consistent model

The molar volumes of 19 hydrous albitic liquids (1.9 to 6.1 wt% H₂O^total) were determined at one bar and 505–765 K. These volume data were derived from density measurements on hydrous glasses at 298 K, followed by measurements of the thermal expansion of each glass from 298 K to its respective glass transition temperature. The technique exploits the fact that the volume of a glass is equal to that of the corresponding liquid at the limiting fictive temperature (T _f′), and that T _f′ can be approximated as the temperature near the onset of the rapid increase in thermal expansion that occurs in the glass transition interval. The volume data of this study were combined with available volume data for anhydrous, Na₂O-Al₂O₃-SiO₂ liquids to derive the partial molar volume (±1) of the H₂O component in an albitic melt at ∼565 K and one bar. To extend the determination of to higher temperatures and pressures, the molar volumes of the hydrous albitic liquids determined in this study were combined with those measured by previous authors at 1023–1223 K and 480–840 MPa, leading to the following fitted values (±1) at 1673 K and one bar: (±0.46)×10⁻³ cm⁻³/mol-K, and dVˉ ^H ₂ ^{O total} /dP=−3.82 (±0.36)×10⁻⁴ cm³/mol-bar. The measured molar volumes of this study and those of previous authors can be recovered with a standard deviation of 0.5%, which is within the respective experimental errors. There is a significant difference between the values for derived in this study as a function of temperature and pressure and those obtained from an existing polynomial, primarily caused by the previous absence of accurate density measurements on anhydrous silicate liquids. The coefficients of thermal expansion (=4.72×10⁻⁴/K) and isothermal compressibility ( _T =1.66×10⁻⁵/bar) for the H₂O component at 1273 K and 100 MPa, indicate that H₂O^total is the single most expansive and compressible component in silicate liquids. For example, at 1473 K and 70 MPa (conditions of a mid-ocean ridge crustal magma chamber), the presence of just 0.4 wt% H₂O will decrease the density of a basaltic liquid by more than one percent. An equivalent decrease in melt density could be achieved by increasing the temperature by 175 degrees or the decreasing pressure by 230 MPa. Therefore, even minor quantities of dissolved water will have a marked effect on the dynamic properties of silicate liquids in the crustal environment. Received: 20 August 1996 / Accepted: 15 March 1997     

Remote spectroscopic identification of carbonaceous chondrite mineralogies: Applications to Ceres and Pallas

High-resolution spectroscopic observations of asteroids Ceres and Pallas have been obtained in the 1.0- to 2.6-μm region. Combined with previous spectralmeasurements at other wavelengths, this work presents the broadband spectral reflectances of these asteroids over the 0.4 to 3.6-um region. This extended coverage permits new analyses of the surface mineralogies of these objects. Using laboratory comparison spectra of meteorites and mixtures of terrestrial minerals, the surfaces of Ceres and Pallas are consistent with mixtures of opaques and hydrated silicates, such as are found in types C1 and C2 meteorites. This research emphasizes the importance of the 3-um spectral region for studying by remote methods the relationship of carbonaceous chondrite mineralogies to asteroid surfaces.     

Upper limits to trace constituents in Jupiter's atmosphere from an analysis of its 5-μm spectrum

A high-resolution (0.6 cm^?1) spectrum of Jupiter at 5 μm recorded at the Kuiper Airborne Observatory is used to determine upper limits to the column density of 19 molecules. The upper limits to the mixing ratios of SiH₄, H₂S, HCN, and simple hydrocarbons are discussed with respect to current models of Jupiter's atmosphere. These upper limits are compared to expectations based upon the solar abundance of the elements. This analysis permits upper limit measurements (SiH₄), or actual detections (GeH₄), of molecules with mixing ratios with hydrogen as low as 10^?9. In future observations at 5 μm the sensitivity of remote spectroscopic analyses should permit the study of constituents with mixing ratios as low as 10^?10, which would include the hydrides of such elements as Sn and As as well as numerous organic molecules.     

Geochemistry and Rb–Sr geochronology of a ductile shear zone in the Orlica-Śnieżnik dome (West Sudetes, Poland)

Amphibolite-facies orthogneisses of the Orlica-vnie™nik dome in the West Sudetes (Poland) show a local continuous transition from weakly deformed augen gneisses to finely laminated mylonites. Field evidence indicates that ductile shearing developed pre- or syntectonically to a migmatization event. Bulk-rock compositions of variably deformed samples yield no indications for deformation- and/or fluid-enhanced element mobility and redistribution. ⁸⁷Rb-⁸⁶Sr geochronology (biotite, phengite, whole rock) places time constraints on the deformation process and the post-orogenic cooling history. Phengite- and biotite-whole-rock pairs yield Rb-Sr ages of 340 to 334 Ma and 335 to 294 Ma, respectively, independent of the degree of deformation. The weighted mean of phengite-whole-rock pairs indicates an age of 337.4DŽ.3 Ma. Combining most of the biotite-whole-rock data yields a weighted mean age of 328.6dž.4 Ma. Because of their different closure temperatures for the Rb-Sr system, these differences are interpreted to date cooling after a thermal event. Direct dating of the deformation is not possible, but the cooling history record defines a minimum age for the development of ductile shearing and the last migmatization event. These time constraints provide evidence for the initiation of crustal collapse during or immediately following peak metamorphic conditions. The results of this study further document the importance of Variscan metamorphism in the Orlica-vnie™nik dome.     

Occurrence of naphthalenesulfonates and their condensates with formaldehyde in a landfill leachate and their transport behavior in groundwater of the Upper Rhine Valley, Germany

. Naphthalenesulfonates and their condensation products with formaldehyde are manufactured in the chemical industry for broad application as tanning agents, dispersing agents, and as superplasticizers for concrete. With the disposal of waste they have found their way into the aquatic environment. Five monomeric naphthalenesulfonates and a group of dimeric sulfonated naphthalene-formaldehyde condensates (SNFC) were identified in the leachate and in groundwater observation wells downstream in the plume of the Karlsruhe-West landfill, situated in the Upper Rhine Valley in southwest Germany. For the main monomer of technical SNFC products, 2-naphthalenesulfonate (2-NS), the concentration in the leachate was 170 µg l^–1, which decreased to 9.5 µg l^–1 at a distance of about 300 m from the boundary of the landfill. In the Merdingen tracer test field, the transport of these compounds was studied under more controlled conditions in two tracer experiments with (1) two model compounds, and (2) a technical SNFC product and uranine as a reference tracer. In these experiments, the monomeric naphthalenesulfonates and the SNFC with n=2 behave as conservative tracers. Thus, the findings of the landfill study were supported by these results. Higher molecular SNFC were strongly retarded, which is attributed to adsorption to soil particles. The results of the second tracer experiment suggest a degradation of 2-NS and 2,6-naphthalenedisulfonate (2,6-NDS) after adaptation of the microorganisms in the groundwater aquifer as a consequence of the first tracer experiment.     

Streams in the Harz National Parks (Germany) — a hydrochemical and hydrobiological evaluation

Between 1995 and 2001, 16 measuring points at small and medium sized brooks in the Harz National Parks were sampled. The samples have been evaluated by means of hydrochemistry and macroinvertebrate biology. Although nearly all streams are largely uncontaminated by oxygen-consuming substances, they are settled only by a small number of macroinvertebrate species. There is a clear correlation between this number and pH. The reduction in species number with decrease of pH is mainly caused by the absence of most Ephemeroptera, some Coleoptera and Trichoptera. Comparing biological evaluation of acidity with physico-chemical measurements, a unacceptable underestimation was found. The reason could be that different sensitivities to acidification between regional populations seem to exist.

Despite of the low species number, there is a very specific macroinvertebrate fauna that emphasizes the conservation value of the Harz National Parks.     

Food-web manipulation of drinking water reservoirs with salmonids: vertical distribution of prey and predator

In a novel biomanipulation experiment salmonids were used as a tool to improve water quality. The manipulation was initiated in spring 2000 as a response to non-point sources of phosphorus in a drinking water reservoir in Saxony, Germany. Salmonids (brown trout, Salmo trutta forma lacustris) were chosen as predators as the reservoir has a large hypolimnic water body and surface temperatures rarely exceed 20 °C. The vertical distributions of prey fish and brown trout were analysed with a fleet of vertical gill nets set in the pelagic zone of the reservoir. Consumption of brown trout was estimated by means of a bioenergetic model and the diet analyses of the trout. While the dominant planktivore (roach, Rutilus rutilus) was caught almost exclusively in the epilimnion during the stratification period trout were caught mainly below a depth of 10 m. Diet analysis revealed that the trout performed vertical migrations to consume food in the epilimnic layer, as an important food component were adult terrestrial and aquatic insects. The amount of fish in the food increased strongly with the size of the brown trout. The consumption estimate suggested that the trout had consumed 2-3% of the total roach stock during the study period (May-November 2000) of the first year of biomanipulation. We conclude that in general salmonids are suitable for food-web manipulation in deep reservoirs, but the stocked fish should be as large as possible (> 300 mm) and the proportion of large trout (> 500 mm) should be as high as possible.