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1.
Kazuyuki Uehara Shin-Ichi Ito Hideo Miyake Ichiro Yasuda Yugo Shimizu Tomowo Watanabe 《Journal of Oceanography》2004,60(2):397-409
During November 2000–June 2002, both direct current measurements from deployment of a line of five moorings and repeated CTD
observations were conducted along the Oyashio Intensive observation line off Cape Erimo (OICE). All the moorings were installed
above the inshore-side slope of the Kuril-Kamchatka Trench. Before calculating the absolute volume transports, we compared
vertical velocity differences of relative geostrophic velocities with those of the measured velocities. Since both the vertical
velocity differences concerned with the middle three moorings were in good agreement, the flows above the continental slope
are considered to be in thermal wind balance. We therefore used the current meter data of these three moorings, selected among
all five moorings, to estimate the absolute volume transports of the Oyashio referred to the current meter data. As a result,
we estimated that the southwestward absolute volume transports in 0–1000 db are 0.5–12.8 × 106 m3/sec and the largest transport is obtained in winter, January 2001. The Oyashio absolute transports in January 2001, crossing
the OICE between 42°N and 41°15′ N from the surface to near the bottom above the continental slope, is estimated to be at
least 31 × 106 m3/sec.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
In order to examine the formation, distribution and transport of North Pacific Intermediate Water (NPIW), repeated hydrographic
observations along several lines in the western North Pacific were carried out in the period from 1996 to 2001. NPIW formation
can be described as follows: (1) Oyashio water extends south of the Subarctic Boundary and meets Kuroshio water in intermediate
layers; (2) active mixing between Oyashio and Kuroshio waters occurs in intermediate layers; (3) the mixing of Oyashio and
Kuroshio waters and salinity minimum formation around the potential density of 26.8σθ proceed to the east. It is found that Kuroshio water flows eastward even in the region north of 40°N across the 165°E line,
showing that Kuroshio water extends north of the Subarctic Boundary. Volume transports of Oyashio and Kuroshio components
(relative to 2000 dbar) integrated in the potential density range of 26.6–27.4σθ along the Kuroshio Extension across 152°E–165°E
are estimated to be 7–8 Sv (106 m3s−1) and 9–10 Sv, respectively, which is consistent with recent work.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Masachika Masujima Ichiro Yasuda Yutaka Hiroe Tomowo Watanabe 《Journal of Oceanography》2003,59(6):855-869
Oyashio water flowing into the Mixed Water Region (MWR) and the Kuroshio Extension region that forms North Pacific Intermediate
Water (NPIW) has been examined, based on four Conductivity-Temperature-Depth profiler (CTD)/Lowered Acoustic Doppler Current
Profiler (L-ADCP) surveys of water masses and ocean currents. There are two processes by which the Oyashio water intrudes
across the Subarctic Front (SAF): one is a direct cross-nearshore-SAF transport near Hokkaido along the western boundary,
and the other is a cross-offshore-SAF process. Seasonal variations were observed in the former process, and the transport
of the Oyashio water across SAF near Hokkaido in the density range of 26.6–27.4σθ was 5–10 Sv in spring 1998 and 2001, and 0–4 Sv in autumn 2000, mainly corresponding to the change of the southwestward Oyashio
transport. Through the latter process, 5–6 Sv of the Oyashio water was entrained across the offshore SAF from south of Hokkaido
to 150° in both spring 2001 and autumn 2000. The total cross-SAF Oyashio water transport contributing to NPIW formation is
more than 10 Sv, which is larger than previously reported values. Most of the Oyashio water formed through the former process
was transported southeastward through the Kuroshio Extension. It is suggested that the Oyashio intrusion via the latter process
feeds NPIW in the northern part of the MWR, mainly along the Subarctic Boundary and SAF.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Based on the surface drifters that moved out from the Sea of Okhotsk to the Pacific, the surface velocity fields of mean,
eddy, and tidal components in the Oyashio region are examined for the period September 1999 to August 2000. Along the southern
Kuril Island Chain, the Oyashio Current, having a width of ∼100 km, exists with velocities of 0.2–0.4 m s−1. From 40°N to 43°N, the Subarctic Current flows east- or northeastward with velocities of 0.1–0.3 m s−1, accompanied by a meandering Oyashio or Subarctic front. Between the Oyashio and Subarctic current regions, an eddy-dominant
region exists with both cyclonic and anticyclonic eddies. The existence of an eastward flow just south of Bussol' Strait is
suggested. The 2000 anticyclonic warmcore ring located south of Hokkaido was found to have a nearly symmetric velocity structure
with a maximum velocity of ∼0.7 m s−1 at 70 km from the eddy center. Diurnal tidal currents with a clockwise tidal ellipse are amplified over the shelf and slope
off Urup and Iturup Islands, suggesting the presence of diurnal shelf waves. From Lagrangian statistics, the single-particle
diffusivity is estimated to be ∼10 × 107 cm2s−1. 相似文献
5.
Yugo Shimizu Takanori Iwao Ichiro Yasuda Shin-Ichi Ito Tomowo Watanabe Kazuyuki Uehara Nobuyuki Shikama Toshiya Nakano 《Journal of Oceanography》2004,60(2):453-462
Six newly developed floats, which were set to drift on the 26.7 σθ isopycnal surface and to profile temperature, salinity and pressure above 1000 dbar once a week, were deployed in the Oyashio
and Kuroshio Extension (KE) in order to examine the circulation, formation site and time scale of newly formed North Pacific
Intermediate Water (NPIW). The floats were deployed in February or May 2001, and the data from their deployments to December
2002 are analyzed here. Four of the six floats were deployed near the KE axis at around the first meander crest, and they
moved eastward to 157°E–176°W at latitudes of 30°N–45°N. The other two floats deployed in the Oyashio water with low-potential
vorticity near the south coast of Hokkaido moved southward to reach the KE front and then moved eastward to the same region
as the first four floats. The temperature and salinity at 26.7 σθ measured by the profiling floats indicate that the source waters of NPIW, Oyashio and Kuroshio waters are drastically mixed
and modified in the mixed water region west of 160°E. The floats were separated into the three paths east of 160°E between
the Kuroshio Extension front and the north of Water-Mass front (nearly subarctic front). New NPIW is judged to be formed along
these three paths since the vertical profiles of temperature and salinity are quite smooth, having a salinity minimum at about
26.7σθ along each path. Kuroshio-Oyashio isopycnal mixing ratios of the new NPIW are 7:3, 6:4 and 5:5 at 26.7σθ along the southern, middle and northern paths, respectively. Potential vorticity converges to about 14–15 × 10−11 m−1s−1 along these paths. The time scale of new NPIW formation is estimated to be 1–1.5 years from the merger of Oyashio and Kuroshio
waters to the formation of the new NPIW.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Takanori Iwao Masahiro Endoh Nobuyuki Shikama Toshiya Nakano 《Journal of Oceanography》2003,59(6):893-904
In order to examine the formation, distribution and synoptic scale circulation structure of North Pacific Intermediate Water
(NPIW), 21 subsurface floats were deployed in the sea east of Japan. A Eulerian image of the intermediate layer (density range:
26.6–27.0σθ) circulation in the northwestern North Pacific was obtained by the combined analysis of the movements of the subsurface floats
in the period from May 1998 to November 2002 and historical hydrographic observations. The intermediate flow field derived
from the floats showed stronger flow speeds in general than that of geostrophic flow field calculated from historical hydrographic
observations. In the intermediate layer, 8 Sv (1 Sv ≡ 106 m3s−1) Oyashio and Kuroshio waters are found flowing into the sea east of Japan. Three strong eastward flows are seen in the region
from 150°E to 170°E, the first two flows are considered as the Subarctic Current and the Kuroshio Extension or the North Pacific
Current. Both volume transports are estimated as 5.5 Sv. The third one flows along the Subarctic Boundary with a volume transport
of 5 Sv. Water mass analysis indicates that the intermediate flow of the Subarctic Current consists of 4 Sv Oyashio water
and 1.5 Sv Kuroshio water. The intermediate North Pacific Current consists of 2 Sv Oyashio water and 3.5 Sv Kuroshio water.
The intermediate flow along the Subarctic Boundary contains 2 Sv Oyashio water and 3 Sv Kuroshio water.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Simulation of Formation and Spreading of Salinity Minimum Associated with NPIW Using a High-Resolution Model 总被引:1,自引:2,他引:1
A series of numerical experiments were conducted with a high-resolution (eddy-permitting) North Pacific model to simulate
the formation and spreading of the salinity minimum associated with the North Pacific Intermediate Water (NPIW). It was found
that two factors are required to simulate a realistic configuration of the salinity minimum: a realistic wind stress field
and small-scale disturbances. The NCEP reanalyzed wind stress data lead to better results than the Hellerman and Rosenstein
wind stress data, due to the closer location of the simulated Oyashio and Kuroshio at the western boundary. Small-scale disturbances
formed by relaxing computational diffusivity included in the advection scheme promote the large-scale isopycnal mixing between
the Oyashio and Kuroshio waters, simulating a realistic configuration of the salinity minimum. A detailed analysis of the
Oyashio water transport was carried out on the final three-year data of the experiment with reduced computational diffusivity.
Simulated transport of the Kuroshio Extension in the intermediate layer is generally smaller than the observed value, while
those of the Oyashio and the flow at the subarctic front are comparable to the observed levels. In the Oyashio-Kuroshio interfrontal
zone the zonally integrated southward transport of the Oyashio water (140–155°E) is borne by the eddy activity, though the
time-mean flow reveals the existence of a coastal Oyashio intrusion. In the eastern part (155°E–180°) the zonally integrated
transport of the Oyashio water indicates a southward peak at the southern edge of the Kuroshio Extension, which corresponds
to the branching of the recirculating flow from the Kuroshio Extension.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Masashi Kusakabe Andrey Andreev Vyacheslav Lobanov Igor Zhabin Yuichiro Kumamoto Akihiro Murata 《Journal of Oceanography》2002,58(5):691-701
Data from the R/V Mirai cruise (May–June 2000) have been examined to discover how mesoscale processes associated with eddy dynamics direct affect
the water masses, the distributions and the vertical fluxes of the dissolved oxygen, nutrients and dissolved inorganic carbon
in the western subarctic Pacific. Using maps of the temperature, salinity, dissolved oxygen, nutrients, chlorophyll and sea-air
pCO2 difference we show that the boundaries of the anticyclone eddies in the study region were composed of high productivity coastal
Oyashio water. The coastal waters were wrapped around the anticyclone eddies (thus creating a high productivity belt) and
intruded inside of them. Using SeaWifs data we demonstrate that temporal variations in the position and the strength of anticyclone
eddies advected the Kuril island coastal high productivity waters to the pelagic part, resulting in temporal variations of
the chlorophyll in the Oyashio region. Computed vertical fluxes of the dissolved oxygen (DO), inorganic carbon (DIC) and silicate
show that the anticylonic eddies in the Kuroshio-Oyashio Zone are characterized by enhanced vertical fluxes of the DO and
DIC between the upper (σθ = 26.7–27.0) and lower (σθ = 27.1–27.5) intermediate layer, probably due to the intrusions of the Oyashio waters into the eddies.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Ana Luisa Rosa Yutaka Isoda Kazuyuki Uehara Tomokazu Aiki 《Journal of Oceanography》2007,63(4):573-588
Hydrographic data and composite current velocity data (ADCP and GEK) were used to examine the seasonal variations of upper-ocean
flow in the southern sea area of Hokkaido, which includes the “off-Doto” and “Hidaka Bay” areas separated by Cape Erimo. During
the heating season (April–September), the outflow of the Tsugaru Warm Current (TWC) from the Tsugaru Strait first extends
north-eastward, and then one branch of TWC turns to the west along the shelf slope after it approaches the Hidaka Shelf. The
main flow of TWC evolves continuously, extending eastward as far as the area off Cape Erimo. In the late cooling season (January–March),
part of the Oyashio enters Hidaka Bay along the shallower part of the shelf slope through the area off Cape Erimo, replacing
almost all of the TWC water, and hence the TWC devolves. It is suggested that the bottom-controlled barotropic flow of the
Oyashio, which may be caused by the small density difference between the Oyashio and the TWC waters and the southward migration
of main front of TWC, permits the Oyashio water to intrude along the Hidaka shelf slope. 相似文献
10.
The mechanism by which nutrient is supplied to a warm-core ring (WCR) was investigated in order to understand the greater
productivity of WCR than that of the Kuroshio, where the WCR originattes. A single WCR was observed in January and May, 1997.
The thermostad (a layer of isothermal and isohaline water) of the WCR had different properties from January to May, the differences:
Δwater temperature: −0.698°C, Δsalinity: −0.048, Δsigma θ: +0.072, Δnitrite+nitrate-N: +1.83 μM, Δphosphate: +0.011 μM and
Δsilicate: +3.2 μM. We examined three possible mechanisms for nutrient supply to WCR in winter, namely: 1) inflow of the Oyashio
surface water into WCR; 2) isopycnal mixing with Oyashio water; 3) entrainment of the water below the WCR into the WCR. The
results were as follows: 1) When the decrease of salinity was due to the inflow of the Oyashio surface water, the increase
of nutrients (nitrite+nitrate-N, phosphate-P and silicate-Si) was estimated to be only 17–27% of the observed increase. 2)
When the decrease of salinity was due to isopycnal mixing, the increase of nutrients was estimated to be 30–42% of the observed
increase. 3) When the decrease of salinity in the WCR in May was due to entrainment of the water below the WCR in winter by
convection, the mixing depth was calculated be 620 m according to the salt budget. The increase of nutrients in this case
was calculated to be 82–95% of the observed increase. The main mechanism of nutrient supply to WCR was concluded to be due
to the entrainment of the water below the WCR by winter mixing.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
The annual transport of anthropogenic carbon (Canth) to the North Pacific Intermediate Water (NPIW) from the Western Subarctic Gyre (WSG) has been re-estimated by using newly
estimated Oyashio transport and Canth concentration, the latter calculated by the recently-established “ΔC*” method with some modifications. Estimated annual Canth transport through the nearshore Oyashio west of 146°E was 0.020 ± 0.010 GtC y−1, closely approximating the previous estimation based on a 1-D model calibrated with the CFC vertical distribution. The present
study, however, found that an additional 0.025 ± 0.010 GtC y−1 of Canth was transported into NPIW in the region east of 146°E. Total Canth transport, 0.045 GtC y−1, contributes about 35% of annual Canth accumulation of the whole temperate North Pacific.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
In this study we test Talley's hypothesis that Oyashio winter mixed-layer water (26.5–26.6σ θ) increases its density to produce the North Pacific Intermediate Water (NPIW) salinity minimum (26.7– 26.8σθ) in the Mixed Water Region, assuming a combination of cabbeling and double diffusion. The possible density change of Oyashio
winter mixed-layer water is discussed using an instantaneous ratio of the change of temperature and salinity along any particular
intrusion (R
l
). We estimate the range of R
l
DD
required to convert Oyashio winter mixed-layer water to the NPIW salinity minimum due to double diffusion, and then assume
double-diffusive intrusions as this conversion mechanism. A double-diffusive intrusion model is used to estimate R
l
DD
in a situation where salt fingering dominates vertical mixing, as well as to determine whether Oyashio winter mixed-layer
water can become the NPIW salinity minimum. Possible density changes are estimated from the model R
l
DD
by assuming the amount of density change due to cabbeling. From these results, we conclude that Oyashio winter mixed-layer
water contributes to a freshening of the lighter layer of the NPIW salinity minimum (around 26.70σθ) in the MWR. 相似文献
13.
Ryuichiro Inoue Jiro Yoshida Yutaka Hiroe Kousei Komatsu Kiyoshi Kawasaki Ichiro Yasuda 《Journal of Oceanography》2003,59(2):211-224
The mixing processes in the Mixed Water Region (MWR) that lead to changes in the properties of North Pacific Intermediate
Water (NPIW) have been studied using observational data sets obtained in May–June 1998. Neutral surfaces, the equation of
water mass conversion rate on neutral surfaces and the equation of vertical velocity across neutral surfaces have been used
to distinguish dominant processes by assuming the horizontal scale to be the streamer scale (under 100 km). The possibility
of double diffusive convection is also discussed in relation to the density ratio. These results may be summarized as follows:
(1) the difference between the potential density surface and the neutral surface may rise to −0.04 kg/m3 around the source water of NPIW; (2) horizontal diffusion causes strong modifications of the source water of NPIW; (3) the
density range within which strong modification of the source water of NPIW occurs becomes dense from the northern part of
MWR near the Oyashio Front to the southern part near the Kuroshio Front, and to the eastern part. Our modeling of these processes
shows that cabbeling has effects on the density increment of the source water of NPIW in the northern and southern part of
MWR. Double diffusive convection has effects on the density increment of the source water of NPIW, mainly in the northern
part of MWR. The possible density increment due to cabbeling in these areas is estimated to be 0.01≈0.03 kg/m3. The possible density increment due to double diffusive convection is 0.01≈0.03 kg/m3. The total density increment due to cabbeling and double diffusive convection amounts to 0.06 kg/m3.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Horizontal and meridional volume transports on timescales from intra-seasonal to interannual in the North Pacific subarctic
region were investigated using a reanalysis dataset for 1993–2001 that was constructed from an assimilation of the TOPEX altimeter
and in situ data into an eddy-permitting North Pacific ocean general circulation model. The barotropic flow is excited along east of
the Emperor Seamounts by the western intensification dynamics. The volume transport of this flow compensates for that across
the interior region east of the Seamounts below the summit depth of the Seamounts. The Oyashio, which is also considered as
a compensation flow for the transport in the whole interior region, includes baroclinic as well as barotropic components.
Baroclinic transports in the whole interior region exceed those in the western boundary region in the upper (200–1000 m) and
lower (2000–5000 m) layers, and the total transport is northward (southward) in the upper (lower) layer. These excesses of
the baroclinic transport are balanced by a vertical transport of the meridional overturn. The meridional overturn has a complementary
relation to the basin-scale baroclinic circulation in the North Pacific subactic region.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Hydrographic Structure and Transport of Intermediate Water in the Kuroshio Region off the Boso Peninsula, Japan 总被引:1,自引:1,他引:1
Kosei Komatsu Yutaka Hiroe Ichiro Yasuda Kiyoshi Kawasaki Terrence M. Joyce Frank Bahr 《Journal of Oceanography》2004,60(2):487-503
Hydrographic structure and transport of intermediate water were observed in the Kuroshio region south of Japan, focusing on
the 26.6–27.5σθ density in six cruises from May 1998 through September 2001. In the section off the Boso Peninsula where the Kuroshio exfoliates
eastward, the intermediate water was clearly clustered into three groups meridionally composed of the coastal water, the Kuroshio
water and the offshore water. Compared with the Kuroshio water characterized by warm, salty water transported by the Kuroshio,
the coastal and offshore waters significantly degenerated due to mixing with cold, fresh waters originated from the subarctic
region: the former was affected by alongshore spread of the coastal Oyashio and the latter by direct intrusion of the new
North Pacific Intermediate Water (NPIW) into the southern side of the Kuroshio current axis. Particularly the offshore water
showed higher apparent oxygen utilization (AOU) in layers deeper than 26.9σθ while it showed lower AOU in layers shallower than 26.9σθ, which indicated that colder, fresher and higher AOU water was distributed on the southeastern side of the Kuroshio in deeper
layers. In May 1998, the Oyashio-Kuroshio mixing ratio was estimated to be typically 2:8 for the offshore water on the assumption
of isopycnal mixing. Moreover, northeastward volume transport of the Kuroshio water was obtained from geostrophic velocity
fields adjusted to lowered acoustic Doppler current profiler (LADCP) data to yield 6.1 Sv at 26.6–26.9σθ and 11.8 Sv at 26.9–27.5 σθ.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
To examine whether the regime shift in 1998 that has been variously reported to have occurred in the oceanographic conditions
of the central and eastern North Pacific also occurred in the Oyashio region, western North Pacific, we compared data over
the period 1990–2003. Oceanographic conditions were compared before 1997 with those after 1998, using the A-line dataset (1990–2003) obtained by the oceanographic surveys of the Hokkaido National Fisheries Research Institute, Fisheries
Research Agency (HNFRI/FRA). Seasonal changes of the monthly-mean SST (as temperature in the surface layer) show a significant
increase in spring after 1998. After 1998, the mean concentration of chlorophyll a at the surface was higher in spring than that before 1997. This was more remarkable in the main current of the Oyashio. These
changes suggest that the spring phytoplankton bloom in the Oyashio region after 1998 was larger in magnitude and initiated
earlier. Consumption of nutrients during the spring bloom and standing stock of netplankton also shows a distinct difference
between the time period before 1997 and after 1998. These results support the occurrence of the regime shift around 1998 in
the Oyashio region. The changes of hydrographical conditions accompanying with the 1998 regime shift are discussed. The hydrographic
mechanism of enhancement of primary productivity during the spring phytoplankton bloom was not fully clarified, though. Results
in this study may support the usefulness of the A-line dataset for analysis of long-term variability in the western subarctic Pacific. 相似文献
17.
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
18.
Motohiko Kashima Shiro Imawaki Shin-Ichiro Umatani Hiroshi Uchida Yuji Hashibe Hiroshi Ichikawa Masao Fukasawa 《Journal of Oceanography》2003,59(3):291-301
Theoretically, the geostrophic approximation holds for the low-frequency flow field, but no detailed examination has been
done on how well the estimated geostrophic velocity corresponds with the observed velocity. Intensive surveys were carried
out during 1993–1995 in the Kuroshio and its recirculation regions south of Shikoku, Japan, including repeated hydrographic
surveys and direct current measurements at nominal depths of 700, 1500 and 3000 m. For these depth intervals, vertical differences
of estimated geostrophic velocity are compared with those of observed velocity. For the intermediate layer (between 700 and
1500 m depths), the slope of the regression line is 0.99, correlation coefficient is 0.98, and the root-mean-square of difference
from geostrophic balance is 2.8 cm/s which is close to the estimated error of 2.1 cm/s. For the deep layer (between 1500 and
3000 m depths), the corresponding values are 0.82, 0.93, 1.2 cm/s and 2.0 cm/s, respectively. The results indicate that the
estimated geostrophic velocity compares well with the observed velocity in these regions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
We measured the in situ primary production at four stations from the surface to 80 m off Sanriku in late May 1997. The depth-integrated
daily primary production in the upper 80 m was estimated to be 391, 468, and 855 mgC m−2d−1 in water from the Oyashio, and 336 mgC m−2d−1 in the warm-core ring. The variation in the primary production was primarily due to the variation in phytoplankton activity
(chlorophyll α-specific primary production). A combination of previous and present studies in water from the Oyashio and the
warm-core ring suggested that phytoplankton activity is proportional to light intensity between 12 and 50 Ein m−2d−1 which is close to the usual light condition (61–75 Ein m−2d−1) off Sanriku in May and June. Light may be a limiting factor for phytoplankton off Sanriku in late spring and early summer. 相似文献
20.
In order to examine the applicability of remotely-sensed ocean color for the estimation of phytoplankton biomass and primary
production in the Oyashio region, the western subarctic Pacific, vertical distributions of chlorophylla concentration and primary production were observed in April and May 1997. Spring bloom was observed in both April and May,
and the surface concentration of chlorophylla exceeded 40 mg m−3. The relationship between the standing stocks of chlorophylla within the layer from the sea surface to one optical depth (0–1/k layer) and the surface chlorophylla concentration is expressed as a Michaelis-Menten equation. The mean ratio of the standing stock of chlorophylla in the euphotic layer to that in the 0–1/k layer was 4.41, this ratio did not significantly differ from 4.61 which was obtained at homogeneous distribution of chlorophylla within the euphotic layer. These facts suggest that the distribution of chlorophylla could be assumed to be homogeneous in the euphotic layer during the spring bloom. Results of primary production measurements
by simulatedin situ method were compared with those by an algorithm with two variables; chlorphylla and non-spectral PAR. Daily primary production in the euphotic layer estimated by the algorithm varied in a range of 38–274%
of that estimated by incubation, although the primary productions by the algorithm agreed with those by the incubation at
a half of stations. Primary production within the euphotic layer calculated using simply the surface data was the same as
that estimated using vertical distribution of chlorophylla. These results show that the primary production in the euphotic layer may be estimated from the remote sensed measurements
during the spring bloom in the Oyashio region. 相似文献