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271.
272.
The purpose of this study was to examine the structural changes that macrozoobenthic communities underwent as a result of the annual summer hypoxia at the northern part of Gamak Bay, Korea. During this study period, summer hypoxia occurred at the northern part of Gamak Bay in July. Under hypoxic conditions, both the number of species and population density decreased rapidly. Species diversity also manifested lower values during this hypoxic period. Faunal composition changed seasonally with Capitella capitata dominant at the hypoxic sites in spring but disappearing in summer. The health condition of the benthic faunal community assessed by the composition of functional groups within community also changed due to the summer hypoxia from a slightly polluted condition to a highly polluted condition. From these results it has been shown that the recent macrozoobenthic community structure in Gamak Bay has returned to a state similar to what it was before dredging works commenced. 相似文献
273.
Takashi Doi Michiaki Takano Kei Okamura Tamaki Ura Toshitaka Gamo 《Journal of Oceanography》2008,64(3):471-477
We present the results of a chemical survey at a submarine volcano, Teishi Knoll, obtained using a submersible in-situ Mn
analyzer (GAMOS) mounted on an autonomous underwater vehicle (AUV) platform. During this survey, high-resolution data of dissolved
Mn were obtained in three dimensions in nearly real time. The AUV enabled continuous detailed observations along a preprogrammed
pathway, which could not have been performed with conventional CTD hydrocasts. During this observation, anomalously high dissolved
Mn concentrations were obtained within the crater, corresponding to high water temperatures. The anomalies might be a hydrothermal
signature due to volcanic activity from the crater. 相似文献
274.
Nondimensionalization of variables enables us to treat experiment data much more simply and efficiently by decreasing the
number of variables. In some cases, trivial conclusions (which Kenney, 1982, called spurious self-correlation) result from
a formal application of dimensional analyses. In contrast, in some cases fully significant conclusions can be derived. We
first discuss how to construct nondimensional variables retaining the physical meanings of variables. We then propose simple
and efficient methods, especially the use of “spurious triangle (SpT)”, to discriminate between significant conclusions and
spurious self-correlations in the analysis of nondimensionalized variables. 相似文献
275.
The impact of the Alaskan Stream (AS) eddies on the chlorophyll a (chl-a) distribution in the central subarctic North Pacific
was investigated through analysis of chl-a and altimetry data from satellite observations. Altimetry observations provided
the locations of mesoscale eddies in time and space within the maps of chlorophyll distributions. The climatological chl-a
distributions averaged in the area and time showing presence of AS eddies suggested that AS eddies contributed significantly
to the chl-a distribution in the deep-sea region of the subarctic North Pacific. The chl-a distribution was closely related
to the AS eddies regardless of whether the eddy was located in or detached from the AS. A combination of two or three AS eddies
sometimes formed high chl-a concentration belts that injected chlorophyll and coastal nutrient-rich waters southward from
the Aleutian Islands far into the deep-sea region of the subarctic North Pacific. These results indicate that chl-a distribution
in the central subarctic North Pacific was strongly impacted by AS eddies. 相似文献
276.
Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan) 总被引:1,自引:0,他引:1
Kwang Bae Kim Yu-Shen Hsiao Jeong Woo Kim Bang Yong Lee Yi Kyun Kwon Chang Hwan Kim 《Marine Geophysical Researches》2010,31(4):285-298
The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived
free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s
(SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts
longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density
contrast of 10.25 g/cm3 between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check
points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry.
As a final result, we present an enhanced GGM bathymetry model by integrating all available data. 相似文献
277.
A pattern of slick streaks winding into a spiral, known as a spiral eddy, was identified in 5 images taken by the ERS-1/2
synthetic aperture radar (SAR) in Mutsu Bay (Japan); dynamic and kinematic models of these spiral eddies have been proposed.
Common characteristics of the five spiral eddies are: 1) an eddy diameter of about 15 km; 2) their location in the western
part of the bay; and 3) their cyclonic direction of rotation. Moreover, the wind conditions over the bay were common: prior
to acquiring the images, a strong easterly wind continued blowing for more than one day. The wind field on the bay is known
to be orographically steered and has strong windstress vorticity, which generates cyclonic circulation. The diameter and location
of the circulation simulated with a numerical ocean model corresponded well to those of the identified spiral eddies. Based
on these facts, we propose a dynamic model for the movement of a slick streak, and a kinematic model for the formation of
a spiral eddy. We have assumed calm air, a microlayer and seawater with a cyclonic circulation in the dynamic model. The balance
of forces is established in the microlayer among the frictional force from the seawater, the frictional force from the calm
air, the gravitational force, and the Coriolis force. As a result, the velocity vector of the microlayer deflects slightly
towards the center of the cyclonic circulation. We have assumed a point source of the microlayer in the kinematic model. The
shapes of a slick streak simulated with the models agree well with the identified patterns in the SAR images. 相似文献
278.
Faults with a well-defined strike direction that precisely coincides with the southern rift fault system occur in the study
area in southern Tenerife. This fault system was generated contemporaneously with a chain of cinder cones ~948 ka. Open fractures
in ignimbrites (~668 ka) and fossil beach deposits (~42 ka) of the El Médano area suggest that the rift-associated fault system
was seismically active in the aftermath of the initial volcanic activity (~948 ka) and is probably still active. A second
fault system striking perpendicular to the rift-related faults probably originates from a Holocene paleoearthquake of moderate
intensity. Earthquake-induced ground effects in fossil beach deposits within the study area are consistent with seismically
induced ground effects of several recent and well-documented earthquakes, as well as gravitational sliding triggered by an
intense earthquake in the Nicoya Peninsula of Costa Rica in 1990. Both, the rift-associated and the earthquake-induced fault
system, initially produced open fractures that were occupied by plants and subsequently stabilized by cementation, forming
conspicuous sediment structures in fossil beach deposits of the El Médano site in southern Tenerife. 相似文献
279.
Vinu Valsala 《Journal of Oceanography》2009,65(6):803-816
The spreading pathways of the Somali and Arabian coastal upwelled waters in the northern Indian Ocean are identified from
an ocean re-analysis data set of a single year using numerical passive tracers in a transport model. The Somali and Arabian
coastal upwelled waters are found to have entirely different spreading pathways in the northern Indian ocean. The former circulates
anticyclonically, is mixed vertically, and is advected to the eastern Indian Ocean along the north equatorial region; while
the later intrudes into the northern Arabian Sea, circulates anticyclonically and is advected to the south in the central
Arabian Sea and then to the eastern Indian Ocean. The seasonal surface mixing by strong monsoon winds and sheared currents
due to dominant eddies of the Somali region are found responsible for mixing 25% of Somali upwelled water with the subsurface
and affecting the resultant pathways. The effect of mixing is, however, found negligible in the case of Arabian coastal upwelled
water pathways. The seasonal reversal of circulation and eddy dominance during the southwest monsoon cause the Somali upwelled
water to spread over the northern Indian Ocean faster than the simultaneously upwelled Arabian coastal water. 相似文献
280.
Wataru Takahashi Hiroshi Kawamura Takuo Omura Ken Furuya 《Journal of Oceanography》2009,65(5):647-656
A multi-spectral classification scheme is proposed to identify water with red tide(s) using satellite ocean color imagery
obtained by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). The study area was the eastern Seto Inland Sea in Japan,
where serious red tides frequently occur. “Background Ocean Colors” (BOCs hereafter), or colors of water around a red tide
or those of the water before/after a red tide, are calculated as the monthly climatological average of normalized water-leaving
radiances (nLw) with 0.01 degree spatial resolution with SeaWiFS imagery. Criteria for detecting red-tide pixels are established
from analyses of characteristics of the nLws (in the 443, 490, 510, and 555 nm bands) anomalies from BOCs and the nLw spectra
together with the red-tide records in Osaka Bay. The proposed scheme can efficiently indicate the presence or absence of red
tides for independent match-ups with 83% accuracy. Additional validations of specific events indicate that the algorithm performed
well in the study area. These results suggest that the scheme is appropriate to detect red tides in the optically complex
coastal water of the eastern Seto Inland Sea. 相似文献