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961.
Dissolved aluminium and the silicon cycle in the Arctic Ocean 总被引:1,自引:0,他引:1
Concentrations of dissolved (0.2 µm filtered) aluminium (Al) have been determined for the first time in the Eurasian part of the Arctic Ocean over the entire water column during expedition ARK XXII/2 aboard R.V. Polarstern (2007). An unprecedented number of 666 samples was analysed for 44 stations along 5 ocean transects. Dissolved Al in surface layer water (SLW) was very low, close to 1 nM, with lowest SLW concentrations towards the Canadian part of the Arctic Ocean and higher values adjacent to and in the shelf seas. The low SLW concentrations indicate no or little influence from aeolian dust input. Dissolved Al showed a nutrient-type increase with depth up to 28 nM, but large differences existed between the different deep Arctic basins. The differences in concentrations of Al between water masses and basins could largely be related to the different origins of the water masses. In the SLW and intermediate water layers, Atlantic and Pacific inflows were of importance. Deep shelf convection appeared to influence the Al distribution in the deep Eurasian Basin. The Al distribution of the deep Makarov Basin provides evidence for Eurasian Basin water inflow into the deep Makarov Basin. A strong correlation between Al and Silicon (Si) was observed in all basins. This correlation and the nutrient-like profile indicate a strong biological influence on the cycling and distribution of Al. The biological influence can be direct by the incorporation of Al in biogenic silica, indirect by preferential scavenging of Al onto biogenic siliceous particles, or by a combination of both processes. From the slope of the overall Al–Si relationship in the intermediate water layer (AIDW; ~ 200–2000 m depth), an Al/Si ratio of 2.2 atoms Al per 1000 atoms Si was derived. This ratio is consistent with the range of previously reported Al/Si uptake ratio in biogenic opal frustules of diatoms. In the deepest waters (>2000 m depth) a steeper slope of the Al–Si relationship of 7.4 to 13 atoms Al per 1000 atoms Si likely results from entrainment of cold shelf water into the deep basins, carrying the signal of dissolution of terrigenous particles with a much higher Al:Si ratio of crustal abundance. Only a small enrichment with such crustal Al and Si component may readily account for the higher Al:Si slope in the deepest waters. 相似文献
962.
Taro Takahashi Stewart C. Sutherland Rik Wanninkhof Colm Sweeney Richard A. Feely David W. Chipman Burke Hales Gernot Friederich Francisco Chavez Christopher Sabine Andrew Watson Dorothee C.E. Bakker Ute Schuster Nicolas Metzl Hisayuki Yoshikawa-Inoue Masao Ishii Takashi Midorikawa Yukihiro Nojiri Arne Krtzinger Tobias Steinhoff Mario Hoppema Jon Olafsson Thorarinn S. Arnarson Bronte Tilbrook Truls Johannessen Are Olsen Richard Bellerby C.S. Wong Bruno Delille N.R. Bates Hein J.W. de Baar 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2075-2076
963.
An improved method of two-dimensional kinematical structural analysis of tides (the “method of the orbits”) is presented.
This method allows us to determine the parameters of the primary tidal waves shaping the observed tidal structure. The construction
of the vertical orbits for the individual tidal harmonics is performed along the horizontal coordinate axes; one of them is
oriented along the so-called “reactive azimuth,” which coincides with the direction of the tidal current at the instant of
the zero tidal level. In this case, the orbit parameters include information on the amplitude-phase relations of the interfering
waves and allow us to determine the angle of the waves crossing. The suggested method enables us to quantitatively describe
the mechanism of the tidal formation with oblique interference both close to the shore and in the open sea. We tested the
new method in two local zones of the White Sea (Morzhovets Island and in the vicinity of the entrance to Kandalaksha Gulf)
where the presence of rotating semidiurnal tidal currents evidences the significant role of oblique interference of tidal
waves. In these zones, the developed method made it possible to perform a detailed quantitative analysis of the local tide
structure caused by the M2 tidal wave, which plays the dominant role in the White Sea. The result describes the structure of the propagation of the
primary tidal waves better than the field of “pure” energy fluxes that was used earlier. 相似文献
964.
The proposed concept of the “marine coastal zone” (MCZ) is substantiated with considering the role of the neotectonics in
the formation and evolution of the corresponding morphologic system using the Antarctic Peninsula as an example. For this
purpose, the results of the immediate geologic-geomorphologic observations are correlated with an original schematic neotectonic
map compiled for the region in question. It is shown that neotectonic movements are responsible for the block structure of
the coastal zone representing its most stable element, which is complicated by subsequent regional exogenic coast-forming
processes with the glacial one being dominant. Other aspects of the marine coastal zone influenced by neotectonics are also
considered. A new (near-polar) type of the marine coastal zone is defined. 相似文献
965.
A discrete time-delay control (DTDC) law for a general six degrees of freedom unsymmetric autonomous underwater vehicle (AUV) is presented. Hydrodynamic parameters like added mass coefficients and drag coefficients, which are generally uncertain, are not required by the controller. This control law cancels the uncertainties in the AUV dynamics by direct estimation of the uncertainties using time-delay estimation technique. The discrete-time version of the time-delay control does not require the derivative of the system state to be measured or estimated, which is required by the continuous-time version of the controller. This particularly provides an advantage over continuous-time controller in terms of computational effort or availability of sensors for measuring state derivatives, i.e., linear and angular accelerations. Implementation issues for practical realization of the controller are discussed. Experiments on a test-bed AUV were conducted in depth, pitch, and yaw degrees of freedom. Results show that the proposed control law performs well in the presence of uncertainties. 相似文献
966.
Pradeep R. Nambisan 《Ocean Engineering》2009,36(2):158-167
A multi-variable adaptive autopilot for the dive-plane control of submarines is designed. The vehicle is equipped with bow and stern hydroplanes for maneuvering. It is assumed that the system parameters are not known, and the disturbance force is acting on the vehicle. Based on a back-stepping design approach, an adaptive control law is derived for the trajectory control of the depth and the pitch angle. To prevent singularity in the control law, the SDU decomposition of the high-frequency gain matrix is used for the design. In the closed-loop system, asymptotic tracking of the reference depth and pitch angle trajectories is accomplished. Simulation results are presented which show that the submarine performs dive-plane maneuvers in spite of the uncertainties in the system parameters and disturbance forces. 相似文献
967.
I. G. Granberg V. F. Kramar R. D. Kuznetsov O. G. Chkhetiani M. A. Kallistratova S. N. Kulichkov M. S. Artamonova D. D. Kuznetsov V. G. Perepelkin V. V. Perepelkin F. A. Pogarskii 《Izvestiya Atmospheric and Oceanic Physics》2009,45(5):541-548
The studies conducted in 1991–2004 by scientists of the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, and the Karpov Institute of Physical Chemistry yielded data on the structures of the surface air layer (to a height of 20 m) and both subinversion and inversion layers (to heights of from 800 m to 1 km), where arid aerosol is transported. One of the main objectives of the 2007 experiment was to record the space-vortex structures within a layer of 30–700 m that directly provide the removal and long-range transport of fine-dispersed (<5 µm) desert aerosol. This paper describes the organization of the Khar-Gzyr 2007 experiment (Black Lands, 2007) to study the convective removal of arid aerosol from desertificated lands, and it presents some data obtained from the remote sensing of the atmospheric boundary layer with a sodar network in the course of this experiment. The sodar network, which was developed to study a spatial structure of coherent vortices, included three identical minisodars (with carrier frequencies of 3.8 kHz) located at the apices of a triangle, each side of which was about 3.5 km, and a sodar (with a carrier frequency of 1.7 kHz). The vertical profiles of the three wind-velocity components and the characteristics of air temperature fluctuations were determined. The procedure of identifying coherent vortex structures is described. The variations in the vertical and horizontal wind-velocity components and the scales characteristic of such structures are estimated. 相似文献
968.
Laser line scan imaging and chirp sub-bottom profiling were used to detail the morphology of a submarine mud volcano and brine-filled crater at 652 m water depth in the northern Gulf of Mexico. The mud volcano has a relief of 6 m and a basal diameter of about 80 m. The feature comprises a central, brine-filled crater (253 m2) surrounded by a continuous bed of methanotrophic mussels (Bathymodiolus childressi) covering 434 m2 and a patchy bed covering an additional 214 m2 of the periphery. The brine pool was mostly <2 m deep, but there were two holes of >28 m and 12 m deep, respectively at the northern end of the pool which emitted continual streams of small clear bubbles. Sub-bottom profiles indicated three distinct strata beneath the present surface of the mud volcano. Integration of 17 profiles shows that the mud volcano has been built in at least three successive stages: the lowest stage deposited 35,400 m3, while the middle and upper stages deposited 7700 and 20,400 m3, respectively. Piston cores were taken at the northern edge of the mussel bed and a site ∼100 m southwest of the pool. Mussel and lucinid shells were recovered from the closer core, lucinid shells from the distant core. A mussel shell from 3.4 m sub-bottom had a Δ14C age of 16.2 ka. Mixture of modern carbon with “carbon dead” reservoir material would produce actual ages ∼2 ka less than the radiocarbon ages. 相似文献
969.
S.A. Barboza R. Alway T. Akpulat W.L. Esch P.J. Hicks Jr. M.L. Gerdes 《Marine and Petroleum Geology》2009
Hydrocarbon top seal analyses are particularly difficult in fluvial and marginal marine settings. Although these settings often contain beds comprised of a low-permeability, clay-rich lithology associated with high quality seals, their presence does not guarantee an effective seal because individual beds within the stratal unit may be laterally discontinuous. Lateral facies changes, truncation of fine-grained beds, or the presence of crevasse splays may provide cross-stratal migration pathways, reducing the effective sealing capacity to a magnitude less than the closure height. 相似文献
970.
F. Rodriguez Monreal H.J. Villar R. Baudino D. Delpino S. Zencich 《Marine and Petroleum Geology》2009
In the Altiplanicie del Payún area (Neuquen Basin, Argentina), immature source rock sections intruded by up to 600 m thick Tertiary laccoliths show full spectrum maturity aureoles over hundreds of meters from the contacts. Commercial oil accumulations (20–33°API) and oil shows are located along the entire column, both in sandstone/carbonate and fractured igneous reservoirs. A challenging numerical model that included the emplacement of the intrusive bodies, with extreme temperature ranges and unusually short calculation time steps, has been done with the aim to better understand hydrocarbon generation and migration processes related to these thermal anomalies. 相似文献