304 resultados para Temperature measurements.


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We present rock magnetic data on 10 samples recovered from ODP Hole 843B. The 95-m.y.-old basalts have moderately high magnetization values, and Curie temperature measurements show that these basalts have undergone systematic low-temperature oxidation. High values for bulk coercivity indicate that the remanent magnetization is likely to be stable over geological time, and low viscous remanent magnetization coefficients measured for these samples argue that acquisition of viscous remanent magnetization is not likely to be geologically important in these samples. Unfortunately, formation of the Hole 843B crustal section at the beginning of the Cretaceous Normal Magnetic Superchron does not allow any simple test of the hypothesis that a substantial component of chemical remanent magnetization, in the direction of the field present during oxidation, is added soon after formation (Raymond and LaBrecque, 1987, doi:10.1029/JB092iB08p08077).

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We have studied the magnetic properties of 22 samples from DSDP Leg 83 to determine the origin of remanence and its relationship to such problems as the tectonic and chemical evolution of the section, the depth of the magnetized layer, and the applicability of magnetic properties of ophiolites to the marine crust. The magnitude of natural remanence has fairly typical values in the uppermost part of the section, falls two to three orders of magnitude in the transition zone, and returns to values slightly less than the upper part in the dike complex. This behavior reflects, for the most part, variations in the amount of magnetic minerals present. Directional behavior is highly variable throughout the section and often shows complexity even on the level of a single sample. Curie temperature measurements and preliminary opaque petrography indicate that the remanence is chemical in origin and probably involves a resetting of the original thermal remanent magnetization (TRM) direction. Selective destructive demagnetization of four breccia samples shows that the remanence of the clasts was acquired prior to consolidation and did not change significantly thereafter. There are also indications that some of the remanence may be carried by secondary magnetic phases. A comparison of these samples with comparable ophiolite rocks is equivocal, with similarities in remanence characteristics but differences in magnetic mineralogy. As for magnetic anomalies, the transition zone is too weakly magnetized to contribute significantly. The available data on the dike complex are inconclusive and their contribution is still open to debate.

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Earth's largest reactive carbon pool, marine sedimentary organic matter, becomes increasingly recalcitrant during burial, making it almost inaccessible as a substrate for microorganisms, and thereby limiting metabolic activity in the deep biosphere. Because elevated temperature acting over geological time leads to the massive thermal breakdown of the organic matter into volatiles, including petroleum, the question arises whether microorganisms can directly utilize these maturation products as a substrate. While migrated thermogenic fluids are known to sustain microbial consortia in shallow sediments, an in situ coupling of abiotic generation and microbial utilization has not been demonstrated. Here we show, using a combination of basin modelling, kinetic modelling, geomicrobiology and biogeochemistry, that microorganisms inhabit the active generation zone in the Nankai Trough, offshore Japan. Three sites from ODP Leg 190 have been evaluated, namely 1173, 1174 and 1177, drilled in nearly undeformed Quaternary and Tertiary sedimentary sequences seaward of the Nankai Trough itself. Paleotemperatures were reconstructed based on subsidence profiles, compaction modelling, present-day heat flow, downhole temperature measurements and organic maturity parameters. Today's heat flow distribution can be considered mainly conductive, and is extremely high in places, reaching 180 mW/m**2. The kinetic parameters describing total hydrocarbon generation, determined by laboratory pyrolysis experiments, were utilized by the model in order to predict the timing of generation in time and space. The model predicts that the onset of present day generation lies between 300 and 500 m below sea floor (5100-5300 m below mean sea level), depending on well location. In the case of Site 1174, 5-10% conversion has taken place by a present day temperature of ca. 85 °C. Predictions were largely validated by on-site hydrocarbon gas measurements. Viable organisms in the same depth range have been proven using 14C-radiolabelled substrates for methanogenesis, bacterial cell counts and intact phospholipids. Altogether, these results point to an overlap of abiotic thermal degradation reactions going on in the same part of the sedimentary column as where a deep biosphere exists. The organic matter preserved in Nankai Trough sediments is of the type that generates putative feedstocks for microbial activity, namely oxygenated compounds and hydrocarbons. Furthermore, the rates of thermal degradation calculated from the kinetic model closely resemble rates of respiration and electron donor consumption independently measured in other deep biosphere environments. We deduce that abiotically driven degradation reactions have provided substrates for microbial activity in deep sediments at this convergent continental margin.

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Plankton pump samples and plankton tows (size fractions between 0.04 mm and 1.01 mm) from the eastern North Atlantic Ocean contain the following shell- and skeleton-producing planktonic and nektonic organisms, which can be fossilized in the sediments: diatoms, radiolarians, foraminifers, pteropods, heteropods, larvae of benthic gastropods and bivalves, ostracods, and fish. The abundance of these components has been mapped quantitatively in the eastern North Atlantic surface waters in October - December 1971. More ash (after ignition of the organic matter, consisting mostly of these components) per cubic meter of water is found close to land masses (continents and islands) and above shallow submarine elevations than in the open ocean. Preferred biotops of planktonic diatoms in the region described are temperate shallow water and tropical coastal upwelling areas. Radiolarians rarely occur close to the continent, but are abundant in pelagic warm water masses, even near islands. Foraminifers are similar to the radiolarians, rarer in the coastal water mass of the continent than in the open ocean or off oceanic islands. Their abundance is highest outside the upwelling area off NW Africa. Molluscs generally outnumber planktonic foraminifers, implying that the carbonate cycle of the ocean might be influenced considerably by these animals. The molluscs include heteropods, pteropods, and larvae of benthic bivalves and gastropods. Larvae of benthic molluscs occur more frequently close to continental and island margins and above submarine shoals (in this case mostly guyots) than in the open ocean. Their size increases, but they decrease in number with increasing distance from their area of origin. Ostracods and fish have only been found in small numbers concentrated off NW Africa. All of the above-mentioned components occur in higher abundances in the surface water than in subsurface waters. They are closely related to the hydrography of the sampled water masses (here defined through temperature measurements). Relatively warm water masses of the southeastern branches of the Gulf Stream system transport subtropical and southern temperate species to the Bay of Biscay, relatively cool water masses of the Portugal and Canary Currents carry transitional faunal elements along the NW African coast southwards to tropical regions. These mix in the northwest African upwelling area with tropical faunal elements which are generally assumed to live in the subsurface water masses and which probably have been transported northwards to this area by a subsurface counter current. The faunas typical for tropical surface water masses are not only reduced due to the tongue of cool water extending southwards along the coast, but they are also removed from the coastal zone by the upwelling subsurface water masses carrying their own shell and skeleton assemblages. Tropical water masses contain much more shelland skeleton-producing plankters than subtropical and temperate ones. The climatic conditions found at different latitudes control the development and intensity of a separate continental coastal water mass with its own plankton assemblages. Extent of this water mass and steepness of gradients between the pelagic and coastal environment limit the occurrence of pelagic plankton close to the continental coast. A similar water mass in only weakly developed off oceanic islands.

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Arctic permafrost may be adversely affected by climate change in a number of ways, so that establishing a world-wide monitoring program seems imperative. This thesis evaluates possibilities for permafrost monitoring at the example of a permafrost site on Svalbard, Norway. An energy balance model for permafrost temperatures is developed that evaluates the different components of the surface energy budget in analogy to climate models. The surface energy budget, consisting of radiation components, sensible and latent heat fluxes as well as the ground heat flux, is measured over the course of one year, which has not been accomplished for arctic land areas so far. A considerable small-scale heterogeneity of the summer surface temperature is observed in long-term measurements with a thermal imaging system, which can be reproduced in the energy balance model. The model can also simulate the impact of different snow depths on the soil temperature, that has been documented in field measurements. Furthermore, time series of terrestrial surface temperature measurements are compared to satellite-borne measurements, for which a significant cold-bias is observed during winter. Finally, different possibilities for a world-wide monitoring scheme are assessed. Energy budget models can incorporate different satellite data sets as training data sets for parameter estimation, so that they may constitute an alternative to purely satellite-based schemes.

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The titanomagnetite oxidation state of "zero age" ocean floor basalts was investigated. For this purpose the oxidation parameter, z, of Hole 648B basalts was determined by SEM observation of "shrinkage cracks" in individual titanomagnetite grains and by Curie temperature measurements. A mean z-value of 0.1 has been deduced for the Hole 648B basalts. Assuming a linear relationship between titanomagnetite low-temperature oxidation state and age of the oceanic basalt, an age of 0.7 m.y. is deduced for Hole 648B.

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Variations in the strength of coastal upwelling in the South East Atlantic Ocean and summer monsoonal rains over South Africa are controlled by the regional atmospheric circulation regime. Although information about these parameters exists for the last glacial period, little detailed information exists for older time periods. New information from ODP Site 1085 for Marine Isotope Stages (MIS) 12-10 shows that glacial-interglacial productivity trends linked to upwelling variability followed a pattern similar to the last glacial cycle, with maximums shortly before glacial maxima, and minimums shortly before glacial terminations. During the MIS-11/10 transition, several periodic oscillations in productivity and monsoonal proxies are best explained by southwards shifts in the southern sub-tropical high-pressure cells followed by abrupt northwards shifts. Comparison to coeval sea-surface temperature measurements suggests that these monsoonal cycles were tightly coupled to anti-phased hemispheric climate change, with an intensified summer monsoon during periods of Northern (Southern) Hemisphere cooling (warming). The timing of these events suggests a pacing by insolation over precession periods. A lack of similar regional circulation shifts during the MIS-13/12 transition is likely due to the large equatorwards shift in the tropical convection zone that occurred during this extreme glaciation.

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In 1937 the "Meteor" performed the cruises of the first part of the "Deutsche Nordatlantische Expedition". This publication treats seven stations of three-day-anchoring occupied during that time, five of which are located on the shelf, one on the continental slope and one on a ridge between the Capverde islands. The Bohnecke current meter, an instrument developed for the expedition, is described briefly and it's accuracy studied by comparing the measurements of two instruments which operated simultaneously at the same depth. It is shown that it is very sensitive for movements of the anchored ship because of the very short measuring intervall (2 minutes). The influence of the ship's movements could not be eliminated completely, the mode of using the instrument at different depths being unsuitable for this. Considering the stratification the accuracy of it's representation by the mean temperature and salinity distributionis studied. It is shown that under certain conditions a distribution estimated from observed values gives more exact results. This especially applies to the TS-diagram. Station Meteor336, located on the shelf near Cape Juby, shows temperatures 4 °C less than the open ocean and so belongs to the area of upwelling. During the observation period, however, internal tides are prominent. The diurnal component is of considerable influence, the distinction from inertial oscillations (25.5 hours) not being possible, however. Station Meteor341, on the shelf off Spanish-Sahara, gives an excellent example of the movements in the centre of the area of upwelling. Changing it's direction by 45° at the beginning of the measurements, the wind causes a change of current direction at all depths which, after some inertial oscillations (period 28.3 hours), settles down to a final value. At the beginning and the end of the observations the current at the upper depths is directed off-shore, the angle between current and wind being 22°, while at the lower depths it is orientated towards the shore. The depth of the upper homogenous layer gives the origin of the water transported upwards When during the inertial oscillations the current goes offshore at all depths temporarily, a sudden disturbance occurs in the temperature measurements. Station Meteor311 is located similar to station Meteor341 but was occupied one month earlier. At that time the wind situation was unnormal, the usual wind direction of 45° occuring at the end of the station. Therefore an unnormally high vertical shear of current speed and direction has been observed, the current vector being directed off-shore at the surface and near the bottom, towards the coast inbetween. The TS-diagram shows that the bottom water is replaced first so that upwelling does not occur during observation time. The state reached at the end of the station does not seem to be stable. Station Meteor369, on the continental slope, is governed by internal waves. Besides the internal tide of 12.4 hours a wave of 6.5 hour period is observed, being possibly amplified by the large bottom slope. In 40 - 60 m depth, where the thermocline is located, a wave with 3.3 hour period is observed which is argued to be an internal boundary wave. Station Meteor334 is located on the shelf NW of the mouth of the Senegal river. A marked temperature stratification, associated with large disturbances, and nearly constant salinity have been found there. The current was going slowly towards S or SW in the upper 20 - 30 m, towards N underneath. At the boundary of the current systems intense turbulence developed,including as it seems a water type of less salinity which is transported from the Senegal river by the lower current. Station Meteor327, located at 100 m depth between two of the Capverde islands, shows oceanic characteristics. The semidiurnal tide is found mainly, the diurnal component having considerable influence. Furtheron an internal wave of 6 hour period is seen the maximum amplitude of which is moving slowly downwards. Two possibilities of explaining it are discussed. Station Meteor366 is found in the area of ceasing winds off the coast of upper Guinea. The temperature there depends strongly on the depth, the salinity being nearly constant. The currents are divided into an upper and a lower system with large variations in both of them. A change of wind direction of nearly 90° is supposed to be the reason. The variations in salinity accordingly are interpreted as the influence of fresh water outflow from land which is felt in a different way at different wind directions. In the last section the daily changes in air and water temperature are studied. The upwelling having large influence on these, a centre of the area of upwelling can be located at about 100 miles north of Cape Blanc (Station Meteor311). The semidiurnal tidal component is compared with previous results for the Atlantic Ocean yielding considerable differences for the direction and time of occurence of the current maximum which might be due to the topographical influences around the shelf.

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Ocean Drilling Program (ODP) Leg 190 was programmed to investigate deformational, diagenetic, and hydrologic processes and their interactions in the Nankai Trough accretionary prism. Site 1178 is the northernmost site in the Muroto Transect. Slope sediments and the underlying landward-dipping reflector zone were successfully cored. Temperature measurements and Cl concentrations in pore water indirectly indicate the presence of gas hydrate between 120 and 400 meters below seafloor (mbsf) at Site 1178, with the highest concentrations between 150 and 200 mbsf (Shipboard Scientific Party, 2001, doi:10.2973/odp.proc.ir.190.109.2001). Sedimentary structures show a broad range of deformation structures rich in fractures, suggesting active fluid circulation in the Nankai Trough prism. One of the objectives of Leg 190 was to clarify the interplay of various fundamental processes taking place in the Nankai Trough accretionary prism. Bacteria or prokaryotes in deep subsurface sediment play an important role for material transformation and circulation in an accretionary prism. Significant amounts of bacteria are detected in many of the samples examined (Shipboard Scientific Party, 2001, doi:10.2973/odp.proc.ir.190.109.2001). The type of organic matter in sediments is an important factor related to bacterial activity. To assist investigations on material circulation in deep subsurface sediments, the samples from Site 1178 were analyzed for geolipids (extractable organic matter). The basic data set is preliminarily compiled in the present report to show the types of organic matter and their concentrations in sediments from Site 1178.

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We report on wintertime data collected from Baffin Bay and northern Davis Strait, a major gateway linking the Arctic with the subpolar North Atlantic, using narwhals (Monodon monoceros) as an oceanographic sampling platform. Fourteen narwhals were instrumented with satellite-linked time-depth-temperature recorders between 2005 and 2007. Transmitters collected and transmitted water column temperature profiles from each dive between December and April, where >90% of maximum daily dive depths reached the bottom. Temperature measurements were combined with 15 helicopter-based conductivity-temperature-depth (CTD) casts taken in April 2007 across central Baffin Bay and compared with hydrographic climatology values used for the region in Arctic climate models. Winter temperature maxima for whale and CTD data were in good agreement, ranging between 4.0°C and 4.6°C in inshore and offshore Baffin Bay and in Davis Strait. The warm Irminger Water was identified between 57°W and 59°W (at 68°N) between 200 and 400 m depths. Whale data correlated well with climatological temperature maxima; however, they were on average 0.9°C warmer ±0.6°C (P < 0.001). Furthermore, climatology data overestimated the winter surface isothermal layer thickness by 50-80 m. Our results suggest the previously documented warming in Baffin Bay has continued through 2007 and is associated with a warmer West Greenland Current in both of its constituent water masses. This research demonstrates the feasibility of using narwhals as ocean observation platforms in inaccessible Arctic areas where dense sea ice prevents regular oceanographic measurements and where innate site fidelity, affinity for winter pack ice, and multiple daily dives to >1700 m offer a useful opportunity to sample the area.

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For the determination of water-soluble protein content of C. finmarchicus of the different stations the Qubit® Protein Assay Kit (Invitrogen) was used. Analysis was performed with extracts of 10 copepods. Working solution was prepared with Qubit® protein reagent and Qubit® protein buffer (1:200). 190 µL working solution was pipetted into each well of a micro plate and 10 µL of sample or Qubit® protein standard (0, 200 and 400 ng/µL) was added. Solutions were mixed and incubated for 15 min at room temperature. Measurements were conducted with a micro plate reader (TriStar LB 941, Berthold Technologies) at 485 nm excitation and 590 nm emission, using the software MikroWin2000 (Berthold Technologies).