共查询到20条相似文献,搜索用时 31 毫秒
1.
A simple estimation of light penetration in tidal flat sediments was developed using various sediment size fractions and their
attenuation rate of irradiance. The attenuation coefficients of the sediment size fractions of 63–125, 125–250, 250–500, 500–1000
μm and 1000–2000 μm were 8.10, 4.08, 2.92, 2.12 and 1.44 mm−1, respectively. Using the average attenuation coefficient of the particle size fractions in the sediment, the calculated attenuation
coefficient agreed well with the actual attenuation coefficient. The method presented gives a photo-parameter to predict productivity
in intertidal sediments, given only the particle size fraction. 相似文献
2.
We study the space and time variations of the concentration of chlorophyll in the Black-Sea coastal zone (near Katsiveli)
in summer 2001–2002. Typical vertical profiles of the pigments are presented. The relations between the concentration of chlorophyll
and the optical parameters of seawater (including the Secchi depth, sea reflectance, effective wavelength of the upwelling
radiation, and the vertical attenuation coefficient of light) are analyzed. The equations for the biological parameters of
seawater and its optical characteristics are presented.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 36–51, May–June, 2006. 相似文献
3.
Underwater light environment and photosynthetic accessory pigments were investigated in Ariake Bay in order to understand
how change of the pigments occurs in response to the tidal-induced changes in underwater light conditions. We hypothesize
that phytoplankton increases photo-protective pigments and decreases light-harvesting pigments under higher light condition
in the mixed layer caused by tidal cycle. Contribution rates of non-phytoplankton particles (a
nph
(400–700)) for light attenuation coefficient (K
d
) was highest (32–85%), and those of phytoplankton particles (a
ph
(400–700)), dissolved organic matter (a
g
(400–700)) and water were 6–32, 6–21 and 5–23%, respectively. Mean K
d
was higher during the spring tide (0.55 ± 0.23 m−1) than the neap tide (0.44 ± 0.16 m−1), and the K
d
difference was caused by the substances resuspension due to the tidal current. In contrast, ratios of photo-protective pigments
(diadinoxanthin and diatoxanthin) per chlorophyll a ((DD+DT)/Chl a) were higher during the neap tide (0.10 ± 0.03 mg mg-Chl a
−1) than the spring tide (0.08 ± 0.03 mg mg-Chl a
−1). And there was significant positive correlation between (DD+DT)/Chl a and mean relative PAR in the mixed layer ($
\overline {I_{mix} }
$
\overline {I_{mix} }
). Moreover, there was significant negative correlation between ratios of light-harvesting pigments (fucoxanthin) per Chl
a (Fuco/Chl a) and $
\overline {I_{mix} }
$
\overline {I_{mix} }
. These results suggested that phytoplankton in Ariake Bay increase photo-protective pigments and decrease light-harvesting
pigments in the higher light condition of less turbid, shallower mixed layer during neap tide than spring tide. 相似文献
4.
Geoacoustic and physical properties of carbonate sediments of the Lower Florida Keys 总被引:4,自引:0,他引:4
Near-surface sediment geoacoustic and physical properties were measured from a variety of unconsolidated carbonate sediments
in the Lower Florida Keys. Surficial values of compressional and shear speed correlate with sediment physical properties and
near-surface acoustic reflectivity. Highest speeds (shear 125–150 m s-1; compressional 1670–1725 m s-1) are from sandy sediments near Rebecca Shoal and lowest speeds (shear 40–65 m s-1; compressional 1520–1570 m s-1) are found in soft, silty sediments which collect in sediment ponds in the Southeast Channel of the Dry Tortugas. High compressional
wave attenuation is attributed to scattering of acoustic waves from heterogeneity caused by accumulation of abundant shell
material and other impedance discontinuities rather than high intrinsic attenuation. Compared to siliciclastic sediments,
carbonate sediment shear wave speed is high for comparable values of sediment physical properties. Sediment fabric, rather
than changes due to the effects of biogeochemical processes, is responsible for these differences. 相似文献
5.
A 2D numerical thermal model for transform continental margin evolution is presented that calculates thermally driven uplift
and subsidence profiles across the margin, for any margin segment assuming both regional and local isostasy. Lateral variations
in the magnitude of continental uplift along the transform are predicted. For a margin with a length of 900 km, with a spreading
rate of 1 cm yr-1, maximum continental uplift of 1300–1400 m is calculated, assuming local isostasy. Using a regional isostatic approximation,
maximum uplift is reduced substantially to 335–470 m, and the exact magnitude, location, and timing of the maximum effect
depends strongly on the assumption of a coupled or decoupled continent–ocean boundary. The length of time a margin point experiences
continent–ocean shearing prior to ridge passing is also shown to be very significant.
Received: 23 February 1995 / Revision received: 17 August 1995 相似文献
6.
We develop a semiempirical spectral model of penetrating irradiance taking into account the biooptical characteristics of
the Black Sea. The evaluation of the contributions of the principal optically active components to the total absorption of
light in the sea shows that, in the short-wave range (400–500 nm), light is mainly absorbed by the dissolved organic matter
(41–77%). The contribution of phytoplankton to the total absorption attains its maximum values (26–37%) in the abyssal part
of the sea in the period of spring blooming of diatoms. In the coastal waters, the absorption of light by suspended nonalgae
particles in summer is almost twice as intense (20–30%) as in the open sea (8–13%). The analysis of the sensitivity of our
model shows that the absorption of light by dissolved organic matter is more significant for the estimation of the photosynthetically
active radiation in the Black Sea than the concentration of pigments and backscattering of light by suspended particles. The
comparison of the results of model computations with the data of measurements of the underwater irradiance reveals high accuracy
of the proposed model. 相似文献
7.
A. Elverhøi H. Norem E. S. Andersen J. A. Dowdeswell I. Fossen H. Haflidason N. H. Kenyon J. S. Laberg E. L. King H. P. Sejrup A. Solheim T. Vorren 《Geo-Marine Letters》1997,17(2):119-125
Debris lobes with characteristic lengths, widths, and thickness of 30–200 km, 2–10 km, and 10–50 m, respectively, represent
the main building blocks of deep-sea fans along the Norwegian–Barents Sea continental margin. Their formation is closely related
to the input of clay-rich sediments to the upper continental slope by glaciers during periods of maximum ice advance. It is
likely that slide release was a consequence of an instability arising from high sedimentation rates on the upper continental
slope. The flow behavior of the debris lobes can be described by a Bingham flow model.
Received: 17 November 1995 / Revision received: 24 June 1996 相似文献
8.
A. S. Subrahmanyam K. S. R. Murthy S. Lakshminarayana M. M. Malleswara Rao K. Venkateswarlu T. C. S. Rao 《Geo-Marine Letters》1997,17(3):202-206
Magnetic data over the eastern continental margin of India and adjacent Bengal fan demarcate two major lineaments. A high
amplitude N–S-trending lineation of the Cauvery offshore Basin corresponds to the offshore fragment of the 80°E lineament
recorded onland. A N–S lineation of very high amplitude anomaly off Chilka lake considered as the possible northward extension
of the 85°E ridge delineated, hitherto in Bengal Fan. A subdued magnetic anomaly zone is demarcated seaward of the continent–ocean
boundary (COB) in the Bengal Fan. Over the northern Bengal Fan this zone is delineated east of 85°E lineation. This quiet
zone might have evolved during the Early Cretaceous period of normal magnetic polarity between M0 and 34 (120–84 Ma) anomalies.
Received: 6 April 1995 / Revision received: 3 September 1996 相似文献
9.
Bathymetry, satellite-derived gravity, and interpreted seismic reflection data across the northern Falkland/Malvinas Plateau
fossil continent–ocean transform rim may record the degree of mechanical coupling across the boundary after ridge–transform
intersection time. The rim comprises a broad microcontinental block in the east and a continental marginal fracture ridge
50–100 km wide elsewhere. Free-air gravity anomalies tentatively suggest that the fracture ridge is locked against oceanic
elastic lithosphere both to the north (Argentine Basin) and south (Central Falkland Basin).
Received: 18 January 1996 / Revision received: 25 March 1995 相似文献
10.
Lithospheric structure along the Queen Charlotte margin in western Canada: constraints from flexural modeling 总被引:1,自引:1,他引:1
The Queen Charlotte fault zone along the western margin of Canada, a right-lateral transform, is part of the boundary between
the Pacific and North America plates. Combining reflection and refraction surveys and flexural modeling, we place limits on
the amount of underthrusting of the Pacific plate beneath the North America plate. Results from our two-dimensional elastic
modeling suggest 10–15 km of underthrusting along the northern Queen Charlotte Islands, in agreement with the amount of underthrusting
inferred from plate motion models.
Received: 12 June 1995/Revision received: 9 December 1995 相似文献
11.
J.-P. Bouillin G. Poupeau E. Labrin C. Basile N. Sabil J. Mascle G. Mascle F. Gillot L. Riou 《Geo-Marine Letters》1997,17(1):55-61
Six sandstone blocks sampled during dives along the southern slope of the Ivory Coast–Ghana continental margin have been
studied using fission tracks in apatite and zircon. Measurements demonstrate that the rocks were heated above 120°C but below
390°C and cooled quickly. The ages of cooling recorded by the apatite crystals are 90 Ma in the western part of the margin,
and 80–70 Ma in the central and eastern part. Heating is interpreted by the heat liberation due to the friction along the
active transform fault and by the vicinity of an oceanic spreading center, which slipped along the margin. Cooling is interpreted
by two stages of denudation due to minor faults and landslides produced by the increasing of the bathymetric step between
the continental margin and the oceanic crust.
Received: 12 April 1995 / Revision received: 20 December 1995 相似文献
12.
G. H. Hong S. H. Kim C. S. Chung D.-J. Kang D.-H. Shin H. J. Lee S.-J. Han 《Geo-Marine Letters》1997,17(2):126-132
Recent sediment accumulation rates are 18–230 mg cm-2 yr-1 (0.02–0.2 cm yr-1) based on excess 210Pb activity profiles in the southwestern part of the East Sea (Sea of Japan). Assuming no mixing beneath surface mixed layers,
210Pb-derived sediment accumulation rates are 18–32 mg cm-2 yr-1 in the northern part of the Yamato Ridge and the Ulleung Basin, 29–136 mg cm-2 yr-1 in the Korea Plateau, and 230 mg cm-2 yr-1 in the southern shelf. These values generally agree with long-term sedimentation rates estimated from dated ash layers.
Received: 6 October 1995 / Revision received: 31 May 1996 相似文献
13.
Motohiko Kashima Shin-Ichi Ito Kaoru Ichikawa Shiro Imawaki Shin-Ichiro Umatani Hiroshi Uchida Takashi Setou 《Journal of Oceanography》2009,65(1):73-80
A quasiperiodic variation of 100–110 days in the Kuroshio path off Cape Ashizuri, resulting from the passage of small meanders,
was detected by observation with moored current meters during 1993–1995. TOPEX/POSEIDON altimeter data covering 9 years showed
that the quasiperiodic variation period was not persistent and modulated twice, with a ∼110-day period from mid-1993 to late
1996, a ∼150-day period from late 1996 to mid-1999, and a ∼110-day period from mid-1999 to late 2001. The quasiperiodic variations
of the Kuroshio path migration were contemporaneous with the quasiperiodic arrivals of mesoscale eddies from the east along
27–32°N over the same ∼110- and ∼150-day period quasiperiodic variations. The periodic arrivals of the eddies configure the
periodic variations of the Kuroshio path and its inter-annual modulation. 相似文献
14.
The southwest Newfoundland transform margin has been studied by deep seismic reflection and refraction. Lower crustal reflectivity
strengthens towards the margin, where there is a shear zone of thinned continental crust overplated with oceanic material.
The reflectivity may be due to shear fabrics in the crust. Crustal thinning probably took place by flow in the lower crust.
The Ungava transform margin has been less studied but has been explored and drilled. It appears more volcanic in character.
The north Baffin region has undergone a complex tectonic history and provides an example of the transition from continent–ocean
to continent–continent transform motion.
Received: 9 March 1995 / Revision received: 25 July 1995 相似文献
15.
As applied to the transparency meter installed in the hydrometeorological complex aimed at monitoring the Black-Sea coastal
waters, we show the possibility of evaluation of various characteristics of state of the marine medium according to the data
of measurements of the beam attenuation coefficient in two spectral regions: short-and long-wave. For this purpose, we use
biooptical relations established on the basis of the experimental data accumulated for the Black Sea.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 37–45, March–April, 2008. 相似文献
16.
Shuguo Cui Huaishan Liu Siyou Tong Jin Zhang Zhiqiang Wu Jinlong Wu 《Marine Geophysical Researches》2008,29(1):27-42
The upper 40 m of stratigraphy of the Yellow River (Huang He) subaqueous delta has been well documented, but the nature of
the underlying strata is currently unknown at high-resolution. To address this deficiency we used a Geopulse seismic system
to image shallow sedimentary deposits up to 120 m deep on the Yellow River delta. High-resolution seismic reflection images
were processed with a series of specific techniques (e.g. swelling attenuation, dynamic s/n filter; f-x deconvolution, predictive
deconvolution dipscan stack), and used with borehole data to investigate the Quaternary offshore sequences in the Yellow River
(Huang He) delta. Repetitive sequences were observed and interpreted as containing layers of transgressive and regressive
deposits. Six seismic transgressive and regressive cycles are identified. Unit M6F–C6F correlates with a relative sea-level rise (173–157 ka) and fall (231–173 ka), while Unit M5F–C5F is associated with a relative sea-level rise (124–100 ka) and fall (157–124 ka). Unit M4F–C4F spans a period of sea-level fall at 100–87 ka, followed by a rise at 87–76 ka. Unit M3F–C3F is a transgressive–regressive cycle dated as 76–58 ka. Unit M2F–C2F correlates with relative sea level fall at 58.2–36 ka and subsequent rise at 36–22 ka. Unit M1F–C1F was deposited during relative sea level fall (22–18 ka), followed by a rise, especially since 8.5 ka. 相似文献
17.
E. B. Shibanov 《Physical Oceanography》2005,15(3):192-202
We study the problem of the choice of initial approximation for the reflection and transmission coefficients in numerical
methods based on the principle of “interaction.” The disadvantages of the approximation of single scattering are demonstrated
and the regularities of propagation of light in media with strongly anisotropic scattering are analyzed. Semianalytic expressions
proposed for the evaluation of the initial approximation enable one to determine the characteristics of the light field in
plane-parallel media with relative errors of about 10−5 within the framework of the algorithm of “adding” of layers.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 62–72, May–June, 2005. 相似文献
18.
By the data of the surveys performed in 1976, 1983, and annually from 1995 to 2006, the successive transformations of the
ecosystem were traced in the Central and Southern Caspian Sea: from the anoxic conditions in 1933–1934 to the oxic state during
the low level period in 1978, then the hypoxia increase and accumulation of nutrients registered anew after 1995, and to the
hydrogen sulfide appearance in the near-bottom layers of the Southern Caspian Sea. Some irreversible changes in the silicon
distribution in the Central Caspian Sea were revealed (the concentration increase to 217 μM at the depth of 780 m, which considerably
exceeded the absolute values for the World Ocean). 相似文献
19.
The stratal architecture of the Gulf of Cádiz continental margin (SW Spain) has been analyzed by using single-channel, very
high-resolution seismic reflection profiles. An evolutionary scheme of asymmetrical depositional sequences is proposed that
was governed by the Late Pleistocene–Holocene sea-level fluctuations. Stratigraphic analysis defined 14 seismic units, that
are configured into two major type-1 depositional sequences related to 4th-order eustatic sea level changes (100–110 ka).
Within these sequences, minor asymmetrical depositional sequences have been recognized related to 5th-order eustatic cycles
(22–23 ka) superimposed and modulated by the regressive trends of 4th-order cycles. In 5th-order depositional sequences, the
forced regressive and lowstand deposits are volumetrically dominant. They cause the main progradation of the margin in such
a way that they form the margin structure almost entirely.
Received: 6 April 1995 / Revision received: 8 March 1996 相似文献
20.
Feeding Habits of the Mesopelagic Fish Gonostoma gracile in the Northwestern North Pacific 总被引:1,自引:0,他引:1
The diet of Gonostoma gracile, a numerically abundant mesopelagic fish in the Subtropical Region and the Transition Domain of the northwestern North Pacific,
was examined using 520 specimens collected during June–July 1988, June 1995 and November 1995. The prey included mainly copepods,
ostracods, amphipods and euphausiids. Copepods and ostracods were the most abundant, comprising approximately 70% of the total
diet. There was little evidence of an ontogenetic dietary shift; Pleuromamma copepods were the most abundant prey for all size classes of fish ranging from 19 to 116 mm in standard length. The size
range of prey increased with growth, but all fish sizes examined fed mainly on 1–4 mm long prey. Luminescent copepods and
ostracods were the most abundant prey, suggesting that G. gracile detects its prey visually.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献