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1.
Naoto Ebuchi 《Journal of Oceanography》2006,62(3):293-301
Marine surface winds observed by two microwave sensors, SeaWinds and Advanced Microwave Scanning Radiometer (AMSR), on the
Advanced Earth Observing Satellite-II (ADEOS-II) are evaluated by comparison with off-shore moored buoy observations. The
wind speed and direction observed by SeaWinds are in good agreement with buoy data with root-mean-squared (rms) differences
of approximately 1 m s−1 and 20°, respectively. No systematic biases depending on wind speed or cross-track wind vector cell location are discernible.
The effects of oceanographic and atmospheric environments on the scatterometry are negligible. Though the wind speed observed
by AMSR also showed agreement with buoy observations with rms difference of 1.27 m s−1, the AMSR wind speed is systematically lower than the buoy data for wind speeds lower than 5 m s−1. The AMSR wind seems to have a discontinuous trend relative to the buoy data at wind speeds of 5–6 m s−1. Similar results have been obtained in an intercomparison of wind speeds globally observed by SeaWinds and AMSR on the same
orbits. A global wind speed histogram of the AMSR wind shows skewed features in comparison with those of SeaWinds and European
Centre for Medium-range Weather Forecasts (ECMWF) analyses. 相似文献
2.
Turbidity limits gas exchange in a large macrotidal estuary 总被引:1,自引:0,他引:1
Gwenaël Abril Marc-Vincent Commarieu Aldo SottolichioPatrice Bretel Frédéric Guérin 《Estuarine, Coastal and Shelf Science》2009
In estuaries, the gas transfer velocity (k) is driven by a combination of two major physical drivers, wind and water current. The k values for CO2 in the macrotidal Gironde Estuary were obtained from 159 simultaneous pCO2 and floating chamber flux measurements. Values of k increased with wind speed and were significantly greater when water currents and wind were in opposing directions. At low wind speeds (<1 m s−1), k increased with water current velocities (0–1.5 m s−1) following an exponential trend. The latter was a good proxy for the Y-intercept in a generic equation for k versus wind speed in estuaries. We also found that, in this turbid estuary, k was significantly lower at high turbidity. The presence of suspended material in great concentrations (TSS > 0.2 g L−1) had a significant role in attenuating turbulence and therefore gas exchange. This result has important consequences for modeling water oxygenation in estuarine turbidity maxima. For seven low turbidity estuaries previously described in the literature, the slope of the linear regression between k and wind speed correlates very well with the estuary surface area due to a fetch effect. In the Gironde Estuary, this slope follows the same trend at low turbidity (TSS < 0.2 g L−1), but is on average significantly lower than in other large estuaries and decreases linearly with the TSS concentration. A new generic equation for estuaries is proposed that gives k as a function of water current velocity, wind speed, estuarine surface area and TSS concentration. 相似文献
3.
Assessment of nitrogen loading from the Kiso-Sansen Rivers into Ise Bay using stable isotopes 总被引:1,自引:0,他引:1
Ryo Sugimoto Akihide Kasai Kouichi Fujita Kenichi Sakaguchi Tomomi Mizuno 《Journal of Oceanography》2011,67(2):231-240
Concentrations of particulate organic nitrogen (PN), dissolved inorganic nitrogen (DIN), and their nitrogen isotope ratios
(δ
15N) in the Kiso-Sansen Rivers were determined from monthly observations over the course of a year to assess variations in the
form and sources of riverine nitrogen discharged into Ise Bay. The δ
15N values of NO3
− observed in the Kiso-Sansen Rivers showed a logarithmic decreasing trend from 8 to 0‰, which varied with the river discharge,
indicating mixing between point sources with high δ
15N and non-point sources with low δ
15N. The influence of isotope fractionation of in situ biogeochemical processes (mainly DIN assimilation by phytoplankton) on
δ
15N of NO3
− was negligible, because sufficient concentrations of NH4
+ for phytoplankton demand would inhibit the assimilation of NO3
−. A simple relationship between river discharge and δ
15N of NO3
− showed that the fraction of total NO3
− flux arising from point sources increased from 4.0–6.3% (1.1–1.8 tN day−1) during higher discharge (>600 m3 s−1) to 30.2–48.3% (2.6–4.1 tN day−1) during lower discharge (<300 m3 s−1). Riverine NO3
− discharge from the Kiso-Sansen Rivers can explain 75% of the variations in surface NO3
− at the head of Ise Bay over the year. 相似文献
4.
Ken Furuya Osamu Hasegawa Takashi Yoshikawa Satoru Taguchi 《Journal of Oceanography》1998,54(5):545-552
The light-saturated maximum value (P
B
max) and initial slope (α) of the photosynthesis-irradiance (P-E) curve were examined in a warm streamer, a cold streamer and
a warm core ring off the Sanriku area in the subarctic western North Pacific Ocean during an ADEOS/OCTS Sanriku field campaign
in early May 1997. BothP
B
max and α were within the ranges of temperate populations. A regional difference was apparent inP
B
max: populations in the warm streamer tended to show higher value ranging between 1.92 and 4.74 mgC (mgChla)−1h−1 than those in the cold streamer and the warm core ring (1.35–2.87 mgC (mgChla)−1h−1). A depth variation was also observed in α in both the warm streamer and the warm core ring: shallow populations tended to
have lower α than deep populations. The depth variations in bothP
B
max and α resulted in a lower light intensity of the light saturation in a deeper population than that of a shallower one. These
depth-related variations in the P-E parameters were likely a manifestation of “shade-adaptation” of photosynthesis. Photoinhibition
was not observed over in situ surface light intensity varying below ca 1600 μmol photon m−2s−1. Water-column primary productivity was biooptically estimated to be 233 to 949 mgC m−2d−1 using vertical distributions of the P-E parameters, chlorophylla, phytoplankton light absorption and underwater irradiance. Applicability of surface data sets for estimation of water-column
productivity is discussed. 相似文献
5.
Numerical study of baroclinic tides in Luzon Strait 总被引:6,自引:1,他引:5
The spatial and temporal variations of baroclinic tides in the Luzon Strait (LS) are investigated using a three-dimensional
tide model driven by four principal constituents, O1, K1, M2 and S2, individually or together with seasonal mean summer or winter stratifications as the initial field. Barotropic tides propagate
predominantly westward from the Pacific Ocean, impinge on two prominent north-south running submarine ridges in LS, and generate
strong baroclinic tides propagating into both the South China Sea (SCS) and the Pacific Ocean. Strong baroclinic tides, ∼19
GW for diurnal tides and ∼11 GW for semidiurnal tides, are excited on both the east ridge (70%) and the west ridge (30%).
The barotropic to baroclinic energy conversion rate reaches 30% for diurnal tides and ∼20% for semidiurnal tides. Diurnal
(O1 and K1) and semidiurnal (M2) baroclinic tides have a comparable depth-integrated energy flux 10–20 kW m−1 emanating from the LS into the SCS and the Pacific basin. The spring-neap averaged, meridionally integrated baroclinic tidal
energy flux is ∼7 GW into the SCS and ∼6 GW into the Pacific Ocean, representing one of the strongest baroclinic tidal energy
flux regimes in the World Ocean. About 18 GW of baroclinic tidal energy, ∼50% of that generated in the LS, is lost locally,
which is more than five times that estimated in the vicinity of the Hawaiian ridge. The strong westward-propagating semidiurnal
baroclinic tidal energy flux is likely the energy source for the large-amplitude nonlinear internal waves found in the SCS.
The baroclinic tidal energy generation, energy fluxes, and energy dissipation rates in the spring tide are about five times
those in the neap tide; while there is no significant seasonal variation of energetics, but the propagation speed of baroclinic
tide is about 10% faster in summer than in winter. Within the LS, the average turbulence kinetic energy dissipation rate is
O(10−7) W kg− 1 and the turbulence diffusivity is O(10−3) m2s−1, a factor of 100 greater than those in the typical open ocean. This strong turbulence mixing induced by the baroclinic tidal
energy dissipation exists in the main path of the Kuroshio and is important in mixing the Pacific Ocean, Kuroshio, and the
SCS waters. 相似文献
6.
Akira Masuda Tadao Kusaba Kenji Marubayashi Michiyoshi Ishibashi 《Journal of Oceanography》1999,55(2):289-305
The variability of the sea surface wind and wind waves in the coastal area of the Eastern Tsushima Strait was investigated
based on the hourly data from 1990 to 1997 obtained at a station 2 km off Tsuyazaki, Fukuoka. The annual mean wind speed was
4.84 m s−1, with strong northwesterly monsoon in winter and weak southwesterly wind in summer. Significant wave heights and wave periods
showed similar sinusoidal seasonal cycles around their annual means of 0.608 m and 4.77 s, respectively. The seasonal variability
relative to the annual mean is maximum for wave heights, medium for wind speeds, and minimum for wave periods. Significant
wave heights off Tsuyazaki turned out to be bounded by a criterion, which is proportional to the square of the significant
wave period corresponding to a constant steepness, irrespective of the season or the wind speed. For terms shorter than a
month, the significant wave height and the wave period were found to have the same spectral form as the inshore wind velocity:
white for frequencies less than 0.2 day−1 and proportional to the frequency to the −5/3 power for higher frequencies, where the latter corresponds to the inertial
subrange of turbulence. The spectral levels of wave heights and wave periods in that inertial range were also correlated with those of the inshore wind velocity, though the scatter was large.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Konstantin V. Lebedev Max Yaremchuk Humio Mitsudera Iwao Nakano Gang Yuan 《Journal of Oceanography》2003,59(6):751-763
A finite-difference quasigeostrophic (QG) model of an open ocean region has been employed to produce a dynamically constrained
synthesis of acoustic tomography and satellite altimetry data with in situ observations. The assimilation algorithm is based upon the 4D variational data interpolation scheme controlled by the model's
initial and boundary conditions. The data sets analyzed include direct and differential travel times measured at the array
of five acoustic transceivers deployed by JAMSTEC in the region of the Kuroshio Extension in 1997, Topex/Poseidon altimetry,
CTD soundings, and ADCP velocity profiles. The region monitored is located within the area 27.5°–36.5°N, 143°–155°. The results
of assimilation show that mesoscale variability can be effectively reconstructed by five transceivers measuring direct and
reciprocal travel times supported by relatively sparse in situ measurements. The misfits between model and data lie within the observational error bars for all the data types used in assimilation.
We have compared the results of assimilation with the statistical inversion of travel time data and analyzed energy balances
of the optimized model solution. Energy exchange between the depth-averaged and shear components of the observed currents
reveals a weak decay of the barotropic mode at the rate of 0.2 ± 0.7⋅10−5 cm2/s3 due to topographic interaction. Mean currents in the region are unstable with an estimate of the available potential energy
flux from the mean current to the eddies of 4.7 ± 2.3⋅10−5 cm2/s3. Kinetic energy transition has the same sign and is estimated as 2.8 ± 2.5⋅10−5 cm2/s3. Potential enstrophy is transferred to the mesoscale at a rate of 5.5 ± 2.7⋅10−18 s−3. These figures provide observational evidence of the properties of free geostrophic turbulence which were predicted by theory
and observed in numerical experiments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
I. B. Palymskii 《Izvestiya Atmospheric and Oceanic Physics》2009,45(5):646-653
The problem of the incompressible liquid convection between two horizontal planes heated on the underside is considered in
the three-dimensional statement. The horizontal boundaries are assumed to be free of tangential stresses and isothermal. The
calculated temporal spectrum of the temperature pulsations at the convection cell center at a supercriticality of 410 agrees
well with the experimental measurement result. The Bolgiano-Obukhov (BO), k
−11/5, k
−3, and k
−5, were obtain for the velocity pulsations. The Kolmogorov spectra k
−5/3 and k
−2.4 were obtained for the temperature pulsations. The presence of clearly identified spectra in the convective flow under study
allows this process to be characterized as developed turbulence. 相似文献
9.
Toshihiro Miyajima Yoshiyuki Tanaka Isao Koike Hiroya Yamano Hajime Kayanne 《Journal of Oceanography》2007,63(4):643-659
A Geographic Information System (GIS)-aided flow-tracking technique was adopted to investigate nutrient exchange rates between
specific benthic communities and overlying seawater in a fringing reef of Ishigaki Island, subtropical Northwestern Pacific.
Net exchange rates of NO3
−, NO2
−, NH4
+, PO4
3−, Total-N and Total-P were estimated from concentration changes along the drogue trajectories, each of which was tracked by
the Global Positioning System and plotted on a benthic map to determine the types of benthic habitat over which the drogue
had passed. The observed nutrient exchange rates were compared between 5 typical benthic zones (branched-coral (B) and Heliopora communities (H), seaweed-reefrock zone (W), bare sand area (S), and seagrass meadow (G)). The dependence of nutrient exchange
rates on nutrient concentrations, physical conditions and benthic characteristics was analyzed by multiple regression analysis
with the aid of GIS. The spatial correlation between nutrient exchange rates and benthic characteristics was confirmed, especially
for NO3
− and PO4
3−, which were usually absorbed in hydrographically upstream zones B and W and regenerated in downstream zones H and G. NO3
− uptake in zones B and W was concentration-dependent, and the uptake rate coefficient was estimated to be 0.58 and 0.67 m
h−1, respectively. Both nutrient uptake in zone W and regeneration in zone H were enhanced in summer. The net regeneration ratio
of NO3
−/PO4
3− in zone H in summer ranged 5.2 to 34 (mean, 17.4), which was somewhat higher than previously measured NO3
−/PO4
3− for sediment pore waters around this zone (1.1–8.5). Nutrient exchanges in zone S were relatively small, indicating semi-closed
nutrient cycling at the sediment-water interface of this zone. NH4
+ efflux from sediments was suggested in zone G. The data suggest that the spatial pattern of nutrient dynamics over the reef
flat community was constrained by zonation of benthic biota, and that abiotic factors such as nutrient concentrations and
flow rates, influenced nutrient exchange rates only in absorption-dominated communities such as zones B and W. 相似文献
10.
P. Jean-Baptiste A. Dapoigny M. Stievenard J. L. Charlou Y. Fouquet J. P. Donval J. M. Auzende 《Geo-Marine Letters》1997,17(3):213-219
Hydrothermal vent fields south of the Garret Fracture zone were sampled for the isotope composition of helium and oxygen
([18O]H2O/[16OH2O). The helium isotopes end-member (3He / 4He=8.3×R
a
and [4He]≈1.2–2.4×10-5 cm3 STP g-1) is quite similar to other known hydrothermal sites pointing to the homogeneous helium composition of the upper mantle. The
δ18O end-member value (δ18O≈0.5–0.6‰) confirms previous suggestions from other sites and from isotope modeling, that hydrothermal fluids are slightly
enriched in 18O relative to the ocean as a result of water–rock interactions at high temperature.
Received: 11 December 1995/Revision received: 20 December 1996 相似文献
11.
A high-frequency (1.2 MHz) four-beam Acoustic Doppler Current Profiler (ADCP) moored on the sea bottom was used for the direct
measurements of the turbulence parameters in the shallow (20 m) coastal zone of the eastern English Channel. The measurements
were as long as four tidal cycles during the period of the spring tide development. The measurements in the ocean and estimates
showed that the Reynolds stress variability coincided with the semidiurnal tide. Their maximum values during the flood phase
were approximately 1.5 Pa, while, during the ebb phase, they reached −1.2 Pa. The variations of the turbulence’s kinetic energy
(TKE) and the rate of its production (P) coincided with the period of the tidal harmonic M4. Their maximum values were found during the flood phase near the bottom, and they were approximately equal to 0.03 m2/s2 and 0.8 W/m3, respectively. These values decreased rapidly with the distance from the bottom. During the periods of low stagnant water,
the values of TKE and P in the water column decreased to the minimum values (2 × 10−3 m2/s2 and 3 × 10−5 W/m3, respectively), which coincided with the moment of the current’s reversal flow. The results demonstrated the dominating role
of the tidal motion, which controls the structure and intensity of the turbulence in the bottom layer, and revealed the characteristic
asymmetry of its distribution related to the nonlinear character of the tidal cycle. 相似文献
12.
Three ARGOS drift buoys were deployed in the Oyashio Current off the Kuril Islands near 45°N in fall, 1990, during a joint
Russia/Canada study of western boundary current dynamics in the Subarctic Pacific Ocean. We here report on one buoy deployed
within an anticyclonic warm core ring (WCR86B) which shows evidence of large amplitude inertial motions of near-diurnal frequency.
During its first week within the ring the buoy drifted with a mean azimuthal current speed of 0.40–0.45 m s−1 and a radius of rotation of 15–20 km. However, superimposed on the mean rotation of the ring at this time were “loops” of
near-diurnal period, radius 7–8 km and speeds exceeding 1 m s−1. During successive rotations the buoy spiraled outward, its mean period of rotation increased and the amplitude of the near-diurnal
motions decreased. The large motions are explained by inertial wave trapping and amplification within the extremely large
and weakly stratified eddy, wherein the negative vorticity of the eddy reduces the local inertial frequency to near-diurnal
frequency. We here suggest that either tidal or wind forcing may generate these high-amplitude “loop” motions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
Seasonal and interannual variations in physicochemical properties were investigated in the neritic area of Sagami Bay, Kanagawa,
Japan, from December 2000 to December 2005. Physicochemical properties (i.e. temperature, salinity, density, dissolved oxygen
and dissolved inorganic nutrient concentration) revealed clear seasonal variations, which were similar to each other during
all 5 years. Temperature, salinity and dissolved inorganic nutrients showed rapid, drastic variations within a few days and/or
weeks. These variations are related to sea levels, principally due to the shifting effects of the Kuroshio Current axis: they
were strongly affected by the Kuroshio Water and other waters, when sea level difference was greater than ca. 35 cm and lower
than ca. 15 cm, respectively. Temperature difference (DF
T
) increased with sea level difference, and the difference of salinity and dissolved inorganic nutrients (NH4
+-N, NO3
−+NO2
−-N, NH4
++NO3
−+NO2
−-N, PO4
3−-P and SiO2-Si) increased and decreased with DF
T
, respectively. All these correlations are significant. Total dissolved inorganic nitrogen (N), phosphate (P) and silicate
(Si) revealed seasonal variations in the ranges of 0.57–16.08, 0.0070–0.91 and 0.22–46.38 μM, respectively. From the regression equations between these elements allowed the following relation to be obtained; Si:N:P
= 14.8:13.4:1. Dissolved inorganic nutrients were characterized by Si and/or P deficiency, especially in the upper layer (0–20
m depth) during summer. Single and/or combined elements are discussed on the basis of potential and stoichiometric nutrient
limitations, which could restrict phytoplankton (diatom) growth as a limiting factor. 相似文献
14.
The seasonal abundance of the dominant dinoflagellate, Ceratium fusus, was investigated from January 2000 to December 2003 in a coastal region of Sagami Bay, Japan. The growth of this species
was also examined under laboratory conditions. In Sagami Bay, C. fusus increased significantly from April to September, and decreased from November to February, though it was found at all times
through out the observation period. C. fusus increased markedly in September 2001 and August 2003 after heavy rainfalls that produced pycnoclines. Rapid growth was observed
over a salinity range of 24 to 30, with the highest specific rate of 0.59 d−1 measured under the following conditions: salinity 27, temperature 24°C, photon irradiance 600 μmol m−2s−1. The growth rate of C. fusus increased with increasing irradiance from 58 to 216 μmol m−2s−1, plateauing between 216 and 796 μmol m−2s−1 under all temperature and salinity treatments (except at a temperature of 12°C). Both field and laboratory experiments indicated
that C. fusus has the ability to grow under wide ranges of water temperatures (14–28°C), salinities (20–34), and photon irradiance (50–800
μmol m−2s−1); it is also able to grow at low nutrient concentrations. This physiological flexibility ensures that populations persist
when bloom conditions come to an end. 相似文献
15.
In 1998–1999, beam attenuation coefficient (bac) profiles, suspended particulate matter (SPM) and particulate organic carbon (POC) concentrations were assessed during five
cruises in the Saronikos Gulf, eastern Mediterranean, Greece. SPM and POC concentrations (0.05–1.84 mg l−1 and 10.2–468.6 μg l−1, respectively) exhibited strong spatial and temporal variations, related to the different environmental characteristics of
various sectors of the gulf, including wind regime and biological productivity. The Elefsis and Keratsini bays, as well as
the area around Psyttaleia Island, showed the highest POC concentrations. The vertical distribution of POC at stations in
the western basin, as well as in the inner and outer Saronikos Gulf is characterised by higher POC concentrations in surface
waters, associated with higher biological activity. The wastewater treatment plant effluents discharged south of the Psyttaleia
Island are a major source of organic particles which directly influence the intermediate water layers, at least during the
stratification period. Assessments of relationships between bac and SPM or POC concentrations revealed a relatively strong correlation between bac and POC. An equation converting bac readings to POC concentration was established which can be applied to historical and/or future bac measurements, independently of season. POC concentrations estimated from calibrated continuous transmissometer readings were
used to estimate the standing stock of POC in the Saronikos Gulf, which varied between 6,110×106 and 13,450×106 g C during the period June 1998 to February 1999. 相似文献
16.
We have examined wind-induced circulation in the Sea of Okhotsk using a barotropic model that contains realistic topography
with a resolution of 9.25 km. The monthly wind stress field calculated from daily European Centre for Medium-Range Weather
Forecasting (ECMWF) Re-Analysis data is used as the forcing, and the integration is carried out for 20 days until the circulation
attains an almost steady state. In the case of November (a representative for the winter season from October to March), southward
currents of velocity 0.1–0.3 m s−1 occur along the bottom contours off the east of Sakhalin Island. The currents are mostly confined to the shelf (shallower
than 200 m) and extend as far south as the Hokkaido coast. In the July case (a representative for the summer season from April
to September), significant currents do not occur, even in the shallow shelves. The simulated southward current over the east
Sakhalin shelf appears to correspond to the near-shore branch of the East Sakhalin Current (ESC), which was observed with
the surface drifters. These seasonal variations simulated in our experiments are consistent with the observations of the ESC.
Dynamically, the simulated ESC is interpreted as the arrested topographic wave (ATW), which is the coastally trapped flow
driven by steady alongshore wind stress. The volume transport of the simulated ESC over the shelf reaches about 1.0 Sv (1
Sv = 106 m3s−1) in the winter season, which is determined by the integrated onshore Ekman transport in the direction from which shelf waves
propagate.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
M. deCastro M. Gmez-Gesteira R. Prego R. Neves 《Estuarine, Coastal and Shelf Science》2003,56(5-6):1055-1064
The wind-induced water exchange between the ria of Ferrol (NW Spain) and the adjacent shelf is analyzed by means of a three-dimensional hydrodynamic model (MOHID2000). Since thermohaline measurements indicate that the estuary can be considered vertically homogeneous a barotropic version of the model has been used. Real in situ wind measurements have been used for model calibration and further analysis. The approach to study the wind effect on water exchange through the ria strait consisted in subtracting the signal calculated with only tidal forcing (Ts) from the one with wind and tidal forcing (WTs). This shows the existence of a residual circulation, with water flowing in wind direction along surfaces layers and a counter current flowing in the opposite direction at bottom layers. The flux across the strait of Ferrol has shown to increase linearly on wind strength, with a correlation larger than 96% and reaching values close to 20 m3 s−1 under real wind forcing. 相似文献
18.
Franck Lartaud Laurent Emmanuel Marc de Rafelis Stephane Pouvreau Maurice Renard 《Geo-Marine Letters》2010,30(1):23-34
Compared to oxygen isotopes, the carbon isotope composition of biogenic carbonates is less commonly used as proxy for palaeoenvironmental
reconstructions because shell δ13C is derived from both dissolved inorganic (seawater) and organic carbon sources (food), and interactions between these two
pools make it difficult to unambiguously identify any independent effect of either. The main purpose of this study was to
demonstrate any direct impact of variable food supply on bivalve shell δ13C signatures, using low/high rations of a 13C-light mixed algal diet fed to 14-month-old (adult) cultured Japanese Crassostrea gigas under otherwise essentially identical in vitro conditions during 3 summer months (May, June and July 2003, seawater temperature
means at 16, 18 and 20 °C respectively) in experimental tanks at the Argenton laboratory along the Brittany Atlantic coast
of France. At a daily ration of 12% (versus 4%) oyster dry weight, the newly grown part of the shells (hinge region) showed
significantly lower δ13C values, by 3.5‰ (high ration: mean of −5.8 ± 1.1‰, n = 10; low ration: mean of −2.3 ± 0.7‰, n = 6; ANOVA Scheffe’s test, p < 0.0001). This can be explained by an enhanced metabolic activity at higher food supply, raising 13C-depleted respiratory CO2 in the extrapallial cavity. Based on these δ13C values and data extracted from the literature, and assuming no carbon isotope fractionation between food and shell, the
proportion of shell metabolic carbon would be 26 ± 7 and 5 ± 5% for the high- and low-ration C. gigas shells respectively; with carbon isotope fractionation (arguably more realistic), the corresponding values would be 69 ± 14
and 24 ± 9%. Both groups of cultured shells exhibited lower δ13C values than did wild oysters from Marennes-Ol éron Bay in the study region, which is not inconsistent with an independent
influence of diet type. Although there was no significant difference between the two food regimes in terms of δ18O shell values (means of 0.1 ± 0.3 and 0.4 ± 0.2‰ at high and low rations respectively, non-significant Scheffe’s test),
a positive δ13C vs. δ18O relationship recorded at high rations supports the interpretation of a progressive temperature-mediated rise in metabolic
activity fuelled by higher food supply (in this case reflecting increased energy investment in reproduction), in terms not
only of δ13C (metabolic signal) but also of δ18O (seawater temperature signal). Overall, whole-shell δ18O trends faithfully recorded summer/winter variations in seawater temperature experienced by the 17-month-old cultured oysters. 相似文献
19.
We used Argo float drift data to estimate average ocean currents at 1000 dbar depth from early 2000 to early 2010. Our estimates
cover the global oceans, except for marginal seas and ice-covered regions, at a resolution of 1 degree in latitude and longitude.
The estimated flow field satisfies the horizontal boundary condition of no flow through the topography, and is in geostrophic
balance. We also estimated the uncertainty in the average flow field, which had a typical magnitude of 0.03 ms−1. The uncertainty is relatively large (>0.03 ms−1 in both the zonal and meridional directions) near the Equator and in the Southern Ocean. The array bias, which is the bias
due to the horizontal gradient in the spatial density of the float data, is generally negligible, with an average magnitude
outside the equatorial region of 0.007 ms−1, becoming relatively large (>0.01 ms−1) only near the coastal regions. The measurement uncertainty is assumed to be spatially uniform and includes errors due to
the Argos positioning system, internal clock drift, unknown surface drift before submerging or after surfacing, and unknown
drifts during ascent and descent between the surface and the parking depth. We found that the overall uncertainty was not
sensitive to the assumed value of the measurement uncertainty (ɛ
m
)1/2 when (ɛ
m
)1/2 < 0.01 ms−1 but it increased with (ɛ
m
)1/2 for (ɛ
m
)1/2 > 0.01 ms−1. 相似文献
20.
Chiho Sukigara Toshio Suga Toshiro Saino Katsuya Toyama Daigo Yanagimoto Kimio Hanawa Nobuyuki Shikama 《Journal of Oceanography》2011,67(1):77-85
A profiling float equipped with a fluorimeter, a dissolved oxygen (DO) sensor, and temperature and salinity sensors was deployed
in the subtropical mode water (STMW) formation region of the North Pacific. It acquired quasi-Lagrangian, 5-day-interval time-series
records from March to July 2006. The time-series distribution of chlorophyll showed a sustained and sizable subsurface maximum
at 50–100 m, just above the upper boundary of the STMW, throughout early summer (May–July). The DO concentration in this lower
euphotic zone (50–100 m) was almost constant and supersaturated in the same period, becoming more supersaturated with time.
On the other hand, the DO concentration at 100–150 m near the upper boundary of the STMW decreased much more slowly compared
with the main layer of STMW below 150 m, even though oxygen consumption by organisms was expected to be larger in the former
depth range. The small temporal variations of DO in the lower euphotic zone and near the upper boundary of the STMW were reasonably
explained by downward oxygen transport because of large diapycnal diffusion near the top of the STMW. Assuming that the oxygen
consumption rate at 100–150 m was the same as that in the main layer of STMW and compensated by the downward oxygen flux,
the diapycnal diffusivity was estimated to be 1.7 × 10−4 m2 s−1. Nitrate transport into the euphotic zone by the same large diffusion was estimated to be 0.8 mmol N m−2 day−1. All of the transported nitrate could have been used for photosynthesis by the phytoplankton; net community production was
estimated to be 5.3 mmol C m−2 day−1. 相似文献