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91.
Following our previous study (Sugimoto and Hanawa, 2005b), we further investigate the reason why reemergence of winter sea
surface temperature anomalies does not occur in the North Pacific eastern subtropical mode water (NPESTMW) area, despite its
occurrence in the North Pacific subtropical mode water and North Pacific central mode water areas. We use vertical temperature
and salinity profiles of the World Ocean Circulation Experiment Hydrographic Program and Argo floats with high vertical and
temporal resolution, together with heat flux data through the sea surface. We point out first that one of the causes for non-occurrence
of reemergence is that the thickness of NPESTMW is very thin. In addition to this basic cause, two major reasons are found:
a vigorous mixing in the lower portion of NPESTMW and less heat input from the atmosphere in the warming season. Since, in
the lower portion of NPESTMW and deeper, the stratification is favorable for salt-finger type convection to occur compared
with the other mode water areas, vigorous mixing takes place. This is confirmed by both a large Turner Angle there and the
existence of staircase structures in vertical temperature and salinity profiles. From the viewpoint of heat input, the NPESTMW
area gradually gains heat in the warming season compared with other mode water areas. As a result, NPESTMW cannot be capped
so quickly by the shallow summer mixed layer, and water properties of NPESTMW are to be gradually modified, even in the upper
portion. 相似文献
92.
A geomorphological and statistical analysis of slope canyons from the northern KwaZulu-Natal continental margin is documented
and compared with submarine canyons from the Atlantic margin of the USA. The northern KwaZulu-Natal margin is characterized
by increasing upslope relief, concave slope-gradient profiles and features related to upslope growth of the canyon forms.
Discounting slope-gradient profile, this morphology is strikingly similar to canyon systems of the New Jersey slope. Several
phases of canyon incision indicate that downslope erosion is also an important factor in the evolution of the northern KwaZulu-Natal
canyon systems. Despite the strong similarities between the northern KwaZulu-Natal and New Jersey slope-canyon systems, key
differences are evident: (1) the concavity of the northern KwaZulu-Natal slope, contrasting with the ∼linear New Jersey slope;
(2) the relative isolation of the northern KwaZulu-Natal canyons, rather than the dense clustering of the New Jersey canyons;
and (3) the absence of strongly shelf-breaching canyons along the northern KwaZulu-Natal margin. In comparison with the New
Jersey margin, we surmise a more youthful stage of canyon evolution, a result of either the canyons themselves being younger
or the formative processes being less active. Less complicated patterns of erosion resulting from reduced sediment availability
have developed in northern KwaZulu-Natal. The reduction in slope concavity on the New Jersey margin may be the result of grading
of the upper slope by intensive headward erosion, a process more subdued—or less evident—on the KwaZulu-Natal margin. 相似文献
93.
The role of vitellogenin in the transport of organochlorines was investigated in Atlantic croaker (Micropogonias undulatus) by exposing them through the diet to o,p′-DDT at a concentration of 10.8 μg/100 g fish/day for 14 days or Aroclor 1254 (PCB) at a concentration of 0.5 mg/100 g fish/day for 30 days during gonadal recrudescence. Tissue samples were taken from the fish at various times after initial exposure, and o,p′-DDT and PCBs were extracted in acetonitrile and analyzed by gas chromatography. Analysis of the ovarian tissue collected 2 and 3 weeks from the start of exposure revealed that the o,p′-DDT concentration increases as the gonadosomatic index (GSI) increases (r2 = 0.63), with accumulation ranging from less than 1% to as much as 8% of the total dosage. Interestingly, o,p′-DDT did not accumulate in the testes during the same exposure period. Accumulation of PCBs was found to be 40 times higher in the ovaries than in the testes. Gel filtration of plasma from exposed females showed that o,p′-DDT elutes in the low density lipoprotein and vitellogenin fractions. Control plasma incubated with o,p′-DDT at 4 °C for 16 h followed by chromatography on Sepharose 6B gave similar results with an o,p′-DDT concentration of 0.6μg/mg protein in the vitellogenin fraction. Furthermore, both o,p′-DDT and PCBs were found to bind to purified croaker vitellogenin. These results suggest that lipoproteins, including vitellogenin, are involved in the transport and accumulation of organochlorines in the ovaries of exposed fish. 相似文献
94.
Valeria Mattiangeli Anthony W. Ryan Paul Galvin Jarle Mork & Thomas F. Cross 《Marine Ecology》2003,24(4):247-258
Abstract. Nine allozyme and two minisatellite loci were used to investigate potential genetic differentiation among three samples of Mediterranean poor cod, Trisopterus minutus capelanus, from the Gulf of Lion, the Tuscan Archipelago and the Aegean Sea. Both types of markers showed consistent results, with FST values of 0.0262 and 0.0296 (P < 0.0015, after Bonferroni correction for multiple tests) for allozymes and minisatellites, respectively. Allele frequency heterogeneity tests between pairs of samples showed a clear separation between the two western Mediterranean samples (Gulf of Lion, Tuscan Archipelago) and the eastern one (Aegean Sea). The results indicate that at least two reproductively isolated populations of poor cod occur in the Mediterranean. 相似文献
95.
96.
Shinya Magome Tomohiro Yamashita Takeshi Kohama Atsushi Kaneda Yuichi Hayami Satoru Takahashi Hidetaka Takeoka 《Journal of Oceanography》2007,63(5):761-773
Jellyfish patch formation is investigated by conducting a drifter experiment combined with aerial photography of a sustained
patch of the moon jellyfish in Hokezu Bay, Japan. Jellyfish patches are aggregations of individuals that are caused by a combination
of swimming (active influence) and advection by currents (passive influence). The drifter experiment involved the injection
of 49 drifters around a distinct surface patch of jellyfish within an area of approximately 300 m × 300 m. The drifters’ motion,
caused only by the passive influence, was recorded in a series of 38 aerial photographs taken over approximately 1 h. The
ambient uniform current field larger than the patch scale was estimated from the movement of the centroid position of drifters,
while the distribution of horizontal divergence and relative vorticity around the patch was estimated from the time-derivative
in areas of triangles formed by the drifters. The centroid positions of both drifters and patches moved stably toward the
bay head at different speeds. The difference vector between the patch and drifter centroids was directed to the sun, and was
opposite to the ambient current. The distributions of vorticity and divergence around patches exhibited inhomogeneity within
the patch scale, and the drifters in this nonuniform current field aggregated near the convergence area within 1 h. The results
suggest that horizontal patch formation is predominantly influenced by passive factors at the surface of Hokezu Bay. Furthermore,
the upward swimming against downwelling may make sustained patch in surface layer. 相似文献
97.
William C. Schwab Elazar Uchupi Robert D. Ballard Thomas K. Dettweiler 《Geo-Marine Letters》1989,9(3):171-178
SeaMARC side-scan sonographs and Argo video and photographic data suggest that the recent sedimentary environment of the floor
of the Tongue of the Ocean is controlled by an interplay of turbidity current flow from the south, sediment spill-over from
the carbonate platform to the east (windward side), and rock falls from the west carbonate escarpment (lee side). The spill-over
forms a sandy sedimentary deposit that acts as a topographic obstruction to the turbidity current flow from the south. This
obstruction is expressed by the westward migration of a northwest-southeast oriented turbidity-current-cut channel. 相似文献
98.
The wavemaking capability and energy absorbing characteristics of a single submerged body, constrained to move horizontally in a surge mode, are examined. The body possesses both a vertical axis of symmetry and a horizontal plane of symmetry and is ‘thin’ in the sense that the body draft is small compared to the length. The behaviour of a single body subject to a constraint being placed upon the amplitude of its displacement and the properties of an array of interacting identical devices are also discussed. 相似文献
99.
100.
Hideo Kawai 《Journal of Oceanography》2005,61(2):235-246
At present, the barotropic buoyant stability parameter has been derived from a vertical virtual displacement of a water parcel. The barotropic inertial stability parameter in the eccentrically cyclogeostrophic, basic current field was derived in 2003 from a horizontal cross-stream virtual displacement of a parcel. By expressing acceleration of a parcel due to a virtual displacement, which is arbitrarily sloping within a vertical section across the basic current, in terms of natural coordinates, we derived the vertical component of baroclinic buoyant stability parameter B
2
2, the horizontal component of baroclinic inertial stability parameter I
2
2, the baroclinic joint stability parameter J
2, its buoyant component B
2 and its inertial component I
2. B
2 is far greater than I
2
2, and when neglecting relative vorticity except for vertical shear, a downward convex curve of J
2 plotted against the slope of a virtual displacement follows a trend of B
2 curve. If a parcel displaces along a horizontal surface or an isopycnal surface, however, B
2 vanishes, and J
2 becomes equal to I
2. Actual parcel is apt to displace not only along the bottom slope, but also along the sea surface and an isopycnal interfacial surface, which is approximately equivalent to an isentropic surface, preferred by lateral mixing and exchange of momentum. Such actual displacement makes B
2 vanishing, and grants I
2 an important role. The present analysis of I
2 examining effects due to curvature and horizontal and vertical shear vorticities are useful in deepening our understanding of baroclinic instability in actual oceanic streams. 相似文献