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881.
D.A. Robertson 《新西兰海洋与淡水研究杂志》2013,47(2):129-136
Frostfish spawning, as indicated by the presence of planktonic eggs, was observed mainly in north‐eastern, but also in south‐western, New Zealand waters in spring to autumn. Spawning takes place in the afternoon in outer shelf waters 50–200 m deep, with surface temperatures and salinities between 17.5 and 22.0°C and 35.3 and 35.6‰ respectively. Egg and oil droplet diameters ranged from 1.65 to 1.75 mm and 0.40 to 0.43 mm respectively. 相似文献
882.
A limited survey was undertaken to determine the concentrations of copper, lead, and chromium in sediments of the upper Manukau Harbour, New Zealand. The concentrations of copper and chromium (33–70 and 70–107 μg g‐1 respectively) were of the same order of magnitude as those reported for other New Zealand harbours. However, lead concentrations (98–247 μg g‐1) were higher than those found for the other harbours. This may be a consequence of higher traffic densities in the surrounding area. 相似文献
883.
J. Christopher L’Esperance Bernard P. Boudreau Mark A. Barry Bruce D. Johnson 《Geo-Marine Letters》2013,33(1):75-81
Poisson’s ratio (static) appears as a parameter in models of soft-sediment geomechanical processes such as gas bubble formation and bioturbation, and in a number of practical applications, including acoustic imaging, but is rarely measured in soft near-surface (upper 20 cm) marine sediments. A new uniaxial apparatus was developed to assess Poisson’s ratios of cylindrical samples of soft cohesive sediments under finite-strain, unconfined, undrained conditions. No constraining membrane around the sample is necessary in the instrument. By monitoring the fluid level in a capillary, changes in sample volume can be determined to high precision (reproducibility). Measurements on reference materials, i.e., gelatine and polyurethane, also indicate high accuracy (veracity). For natural sediments from Nova Scotia, Canada, Poisson’s ratios range from 0.4951 to 0.5 with no indication of anisotropy; therefore, such sediments act as incompressible solids to short-term/small-magnitude stresses, as occur during bubble formation and infaunal movement. 相似文献
884.
Aristomenis P. Karageorgis Theodore D. Kanellopoulos Vasileios Mavromatis Christos L. Anagnostou Eleni Koutsopoulou Mark Schmidt Kosmas Pavlopoulos Efthymios K. Tripsanas Rolf O. Hallberg 《Geo-Marine Letters》2013,33(1):13-29
The Pagassitikos Gulf in Greece is a semi-enclosed bay with a maximum depth of 102 m. According to the present-day bathymetric configuration and the sea level during the latest Pleistocene, the gulf would have been isolated from the open sea, forming a palaeolake since ~32 cal. ka b.p. Sediment core B-4 was recovered from the deepest sector of the gulf and revealed evidence of a totally different depositional environment in the lowest part of the core: this contained light grey-coloured sediments, contrasting strongly with overlying olive grey muds. Multi-proxy analyses showed the predominance of carbonate minerals (aragonite, dolomite and calcite) and gypsum in the lowest part of the core. Carbonate mineral deposition can be attributed to autochthonous precipitation that took place in a saline palaeolake with high evaporation rates during the last glacial–early deglacial period; the lowest core sample to be AMS 14C dated provided an age of 19.53 cal. ka b.p. The palaeolake was presumably reconnected to the open sea at ~13.2 cal. ka b.p. during the last sea-level rise, marking the commencement of marine sedimentation characterised by the predominance of terrigenous aluminosilicates and fairly constant depositional conditions lasting up to the present day. 相似文献
885.
V. V. S. S. Sarma M. S. Krishna R. Viswanadham G. D. Rao V. D. Rao B. Sridevi B. S. K. Kumar V. R. Prasad Ch. V. Subbaiah T. Acharyya D. Bandopadhyay 《Journal of Oceanography》2013,69(1):45-55
A study on biogeochemical cycling in the west coastal Bay of Bengal was undertaken during the peak discharge period to understand the influence of enhanced stratification and primary production on the possible intensification of the oxygen minimum zone (OMZ). Our study reveals that oxygen concentrations were below the detection limits in the northwestern (NW) coastal Bay of Bengal between 100 and 500 m associated with strong stratification and high phytoplankton biomass. Such low oxygen concentrations have never been reported so far from the coastal Bay of Bengal. Despite the existence of an environment conducive to denitrification in the coastal Bay of Bengal, accumulation of neither secondary nitrite nor nitrous oxide (N2O) was observed. The absence of denitrification was reported to be caused by faster scavenging of organic matter and low bacterial respiration rates; in contrast, our results suggest that neither of these factors are potential reasons for the absence of denitrification in the coastal Bay of Bengal. 相似文献
886.
The currents in the Drake Passage are studied from the ADCP and CTD data acquired in a section across the Drake Passage in October-November of 2011 and from the satellite altimeter data. A complicated pattern of currents including eight jets of the Antarctic Circumpolar Current (ACC) and a system of slope and abyssal currents was found. The most interesting result is the discovery of several cyclonic and anticyclonic mesoscale eddies confined to the abyss. Some reasons explaining the generation of such eddies by the meandering of the ACC jets in the upper ocean layer are presented. 相似文献
887.
C. Langlais B. Barnier J.M. Molines P. Frauni D. Jacob S. Kotlarski 《Ocean Modelling》2009,30(4):270-286
The paper evaluates atmospheric reanalysis as possible forcing of model simulations of the ocean circulation inter-annual variability in the Gulf of Lions in the Western Mediterranean Sea between 1990 and 2000. The sensitivity of the coastal atmospheric patterns to the model resolution is investigated using the REMO regional climate model (18 km, 1 h), and the recent global atmospheric reanalysis ERA40 (125 km, 6 h). At scales from a few years to a few days, both atmospheric data sets exhibit a very similar weather, and agreement between REMO and ERA40 is especially good on the seasonal cycle and at the daily variability scale. At smaller scales, REMO reproduces more realistic spatio-temporal patterns in the ocean forcing: specific wind systems, particular atmospheric behaviour on the shelf, diurnal cycle, sea-breeze. Ocean twin experiments (1990–1993) clearly underline REMO skills to drive dominant oceanic processes in this microtidal area. Finer wind patterns induce a more realistic circulation and hydrology of the shelf water: unique shelf circulation, upwelling, temperature and salinity exchanges at the shelf break. The hourly sampling of REMO introduces a diurnal forcing which enhances the behaviour of the ocean mixed layer. In addition, the more numerous wind extremes modify the exchanges at the shelf break: favouring the export of dense shelf water, enhancing the mesoscale variability and the interactions of the along slope current with the bathymetry. 相似文献
888.
V. G. Bondur Yu. V. Grebenyuk K. D. Sabynin 《Izvestiya Atmospheric and Oceanic Physics》2009,45(5):598-607
Based on the results of analyzing the characteristics of currents and temperature measured in the water space of the Mamala
Bay (the Island of Oahu, Hawaii), we investigate the main properties of the field of short-period internal waves, which is
very complex. We focus on analyzing the spectral characteristics and orbit parameters for waves with a period of 20 minutes.
The results of investigations reveal two types of short-period internal waves for this area: intense and fast waves propagating
predominantly toward the ocean and weaker and slower waves propagating mainly toward the coast. Suppositions are made on how
these waves form: the strong and fast waves are likely to be caused by the decay of locally generated internal tides near
the shelf edge, while the weak and slow and very short waves seem to result from the specific interaction between the pycnocline
and strong tidal currents over a steep slope. 相似文献
889.
We analyze the statistical structure of the data of remote sensing of the fields of surface temperature and the concentration
of chlorophyll in the northwest part of the Black Sea with an aim to apply the method of optimal interpolation to the restoration
of the maps of these fields according to the restricted amounts of data. We determine the scales of smoothing for the selection
of the random components of the fields and estimate their difference from the statistical model uniform and isotropic over
the space correlation coefficients. The functions of spectral densities are constructed along various sections and the best
intervals of discretization of the fields required to perform the optimal interpolation with given accuracy are determined.
It is shown that the construction of the maps of fields under the conditions of controlled accuracy of reconstruction of their
values remains possible even if the amounts of the input satellite data are significantly decreased. We consider a procedure
of evaluation of the best possible amounts of data required for the use of the method of optimal interpolation. Some examples
of application of this procedure to the data of remote sensing of the fields of surface temperature and the concentration
of chlorophyll are presented. 相似文献
890.
An integral description of the propagation of steady-state perturbations of the heavy liquid surface
The system of equations of motion describing the gravity wave propagation in a perfect heavy liquid layer is transformed into
a new integral equation for the free surface elevations. In the limit cases, this integral equation describes the linear and
nonlinear periodic waves as well as the known types of solitary waves. In this case a dispersion equation arises because perturbations
of the second and higher orders of smallness are neglected. The integral equation allows for the propagation of invariable
surface perturbations of arbitrary forms if their spatial spectrum is concentrated near small wave numbers (compared to the
inverse wave amplitude). Several examples of solutions are presented. 相似文献