首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 673 毫秒
1.
The primary productivity in coastal water adjacent to the Kuroshio off Shimoda was measured as part of the International Biological Program. The total amount of chlorophylla in the euphotic zone varied widely from 20 mg/m2 to 60 mg/m2 throughout the year and the maximum values were measured in early summer. These values were higher than those in the Kuroshio but agreed with those in the Oyashio. Vertical differentiation of photosynthetic characteristics was well developed and it was strongly related to the stratification of the water column. The light-saturated photosynthetic rate of surface phytoplankton varied from 5.8 mg C/(mg chl.h) in May to 2.0 mg C/(mg chl.h) in January. These rates were higher than those in the Kuroshio. The daily primary production was estimated by the chlorophyll method. Highest value was 0.5–1.5 g C/(m2day) in early summer and the lowest was 0.2 g C/(m2day) in winter. The primary productivity in the coastal water studied accorded fairly well with that in the Oyashio.Contribution No. 239 from Shimoda Marine Biological Station. This study is part of JIBP project entitled Studies on the Dynamic Status of the Biosphere, a Special Research Project supported by the Ministry of Education.  相似文献   

2.
Thermohaline staircases off Cape Erimo, Hokkaido are described and their physical properties are compared with those in other seas. The mean fluxes for heat and salt across the interface induced by salt finger were estimated as 105 cal cm–2d–1, and 0.03 g cm–2d–1, respectively. These values were in the same order as those in Caribbean Sea. The effective eddy diffusivities were also in the same order as the Caribbean ones. This suggests that the double-diffusive convection plays on important role on the water mass conversions occurring in the interfrontal zone between the Oyashio and the Kuroshio Waters.  相似文献   

3.
Sea surface temperature (SST) has been measured in the south of Japan using a thermometer set up in the ferry boat to investigate the characteristics of the warm water intrudes into the coastal areas from the Kuroshio. Time series analysis was applied to the SST data with satellite images and hydrographic observation data from April 1987 to September 1989. The results indicate that the warm Kuroshio water intruded into the coastal areas on the Enshu-nada and the Kumano-nada Seas intermittently with periods of about 50 and 20 days associated with the fluctuation of the Kuroshio path and the Kuroshio frontal disturbance respectively. The intrusion with a 50-day period was dominant when the Kuroshio took a stationary small meander path (B- and C-types). The warm water spread to the west at 20 cm s–1, and was estimated to have a depth of 150 m at least and supply enough heat to make up the loss due to the evaporation in the coastal area. During the straight path of the Kuroshio, it was detected that the warm water intruded into coastal areas only with a 20-day period. The warm water that intrudes with a period of 20 days spreads to the west at 25 cm s–1 in a small scale.  相似文献   

4.
The oil pollution in the Izu Islands waters are observed as follows:
  1. Globules and lumps of oil were collected 2.56 g on the average in wet weight by each taw(174 m3) of a larval net at 389 stations, up to the maximum collection of more than 500 g.
  2. On the investigation of the Oshima—Torishima line (J1–J10), globules and lumps of oil were collected more at the south of the Kuroshio Current than at the north.
  3. In the coastal region (T1–T19) of Japan, many globules and lumps of oil were collected when a cold water mass was located at the west side of the Izu Islands, from south to east side of where the Kuroshio Current took a roundabout and closed near to the Bōsō peninsula (Aug. 1971, Jun. 1972, Aug. 1972), or when the Kuroshio Current took a roundabout the cold water mass which extended as far as Oshima from the coast of the Bōsō peninsula (Sept. 1971).
  相似文献   

5.
Dissolved copper concentrations in surface waters of the Bering Sea ranged from 106 to 882 ngl–1. Higher concentrations were found in continental shelf waters. In the northwestern North Pacific dissolved copper ranged from 54 to 140 ngl–1. Particulate copper concentrations varied regionally and seasonally from 6 to 79 ngl–1. Regionally averaged particulate copper concentrations decreased from 175 to 33g g–1 against an increase in suspended materials because of the dilution effects of biological fractions. Apparent sporadic increases in copper concentrations were found in the mixing area of the Kuroshio and the Oyashio waters. The feature is attributed to the lateral distribution of different water types rather than to the upwelling of deeper waters by eddies. In the same area west of 160E, waters with high concentrations of dissolved copper (96±9 ngl–1) were found. Their origin appears to be the continental shelf of the Bering Sea. In spite of intensive biological activity, a considerable fraction of copper added to shelf waters was transported to the area off Japan via the circulation in the Bering Sea and the Oyashio current.  相似文献   

6.
Direct current measurements of the branch current of the Kuroshio intruding into Sagani Bay were carried out during 1989–1990 in order to clarify the frequency characteristics of the eddies in the lee of Izu-Oshima Island, which are well recognized as cold water mass produced by upwelling. Satellite and ADCP (Acoustic Doppler Current Profiler) data indicated that current velocity in the eddy fluctuates with periods of 2–4 days and 6–8 days.When the Kuroshio branch current intruding into Sagami Bay from the western channel is weak and its velocity at the depth of 400 m is approximately 10 cm s–1, the 6–8 day period fluctuation is dominant. On the other hand, when the branch current strongly intrudes from the western channel with a velocity of approximately 20 cm s–1, the 2–4 day period fluctuation dominates. The relationship between the periods and velocities agrees well with theory based on laboratory experiments for a flow of a homogeneous fluid past a circular obstacle. These periods correspond to the time scale of appearance of the eddy caused by the intrusion of the Kuroshio branch current into Sagami Bay and Izu-Oshima Island.  相似文献   

7.
In situ measurements of the primary productivity of ice algae and phytoplankton were carried out in the fast ice area near Syowa Station (69°00S, 39°35E) during the austral spring and summer of 1983/84. Standing stock of ice algae reached a maximum of 45.1 mg chla m–2 in late October. Phytoplankton standing stock attained a value of 3.57 mg chla m–2 in mid-January. Primary production of ice algae in late October (7.64 mgC m–2 hr–1) was 14 times greater than that in mid-January (0.54 mgC m–2 hr–1). Production in the water column in mid-January (3.46 mgC m–2 hr–1) was 50 times greater than that in late October (0.07 mgC m–2 hr–1). These results indicate a substantial production by ice algae in the spring and by phytoplankton in the summer period.  相似文献   

8.
The statistical properties of shallow temperature inversions in the Pacific Ocean near Japan were investigated using data obtained from. BT observations. In the sea east of Honshu, the Kuroshio front forms the southern boundary of the area where temperature inversions are abundant. Though the occurrence frequency of the temperature inversion layers is very low in the sea south of Honshu, the path of the Kuroshio influences its regional distribution in this region also, and the high occurrence area shifts offshore when the large cold water mass is present off Enshu-nada. The magnitude of the inversion temperature differences in the sea south of Honshu is considerably smaller than that in the sea east of Honshu. The magnitude of inversion thickness has a clear tendency to increase from south to north in the sea east of Honshu, reflecting the higher occurrence frequency of large-scale thick inversion layers in the northern part under the influence of the sub-arctic water mass. The frequency distribution of the inversion thickness in each sub-region (1° square area) in the sea south of Honshu is very similar to that in the region just south of the Kuroshio front in the sea east of Honshu, suggesting that the inversion layers may be generated by similar mechanisms in the sea south of the Kuroshio front.  相似文献   

9.
Current path records of the Kuroshio off southern Japan have been examined for the period 1960–1977. Together with previously published results (S.Yoshida, 1961;Shoji, 1972) this evidence indicates that all major changes in the path of the Kuroshio off Cape Shiono were preceded by the formation of a small trigger meander off Kyushu and its downstream propagation to Cape Shiono. The periods of occurrence of these trigger meanders, most of which decay without propagating downstream, are documented. Small meanders off Kyushu occur throughout the year, but all of those which triggered changes off Cape Shiono were initially generated in the period January–April.Contribution No. 4 of the Pacific International Research Association.  相似文献   

10.
Time-series measurements of temperature, salinity, suspended matter and beam attenuation coefficient () were measured at four hour intervals for about two days in June/ July 1982 in the middle shelf region and the coastal region of the southeastern Bering Sea. Current meters were also moored at the same locations.Depth-time distributions of indicated that profiles of suspended matter resulted from a combined process of resuspension of underlying sediments and sinking of suspended particles. Average-values for all measurements for particles revealed that the upward transport of particles due to resuspension formed a boundary layer, with a thickness apparently related to scalar speed. The average-profiles of the particle volume concentration were assumed to result from a balance between the sinking and diffusive flux of particles under a steady state, and the upward fluxes were calculated. Within the boundary layer, values of the upward fluxes of particulate organic matter linearly decreased with the logarithm of distance from the bottom. Fluxes of organic carbon at the upper edge of the boundary layer were 0.375 gC·m–2·day–1 in the middle shelf region (18 m above the bottom, bottom depth=78m) and 0.484gC·m–2·day–1 in the coastal region (25 m above the bottom, bottom depth=33m), and fluxes of nitrogen in both regions were 0.067 gN·m–2·day–1. The flux of organic carbon obtained in the middle shelf region (18 m above the bottom) agreed approximately with the flux (0.416 gC·m–2·day–1) calculated by substituting primary production data into the empirical equation of Suess (1980).  相似文献   

11.
Primary productivity was measured byin situ method using13C in the offshore Oyashio region in the spring (May) and summer (September) of 1990. Most of the values were within the range of 0.1 to 4 gC 1–1 h–1 although a very large value, 7.96 gC l–1 h–1, was observed in summer. Most daily primary production fell within the range of 372 to 633 mgC m–2 d–1 although a very large value, 2,109 mgC m–2 d–1, was observed around the frontal area in summer. Chlorophylla (Chl.a) exceeded 1 g l–1 in many cases, and the maximum was 4.61 g l–1 in spring and 7.53 g l–1 in summer. Most primary productivity per unit Chl.a (photosynthetic assimilation ratio) was within the range of 0.1 to 3 gC gChl.a –1 h–1 although higher values, 3–6 gC gChl.a –1 h–1, were observed where small-size phytoplanktons (<2 m) were dominant. These results were compared with results obtained until now in the Oyashio region. The values beyond the range obtained so far in the offshore region were also observed in this study. Furthermore, it was pointed out that the size composition of phytoplankton community has significant influence on the results of Chl.a and photosynthetic assimilation ratio in the Oyashio region.  相似文献   

12.
The Algal Growth Potential (AGP) of water samples collected off Gamagori in Mikawa Bay was measured from May 1978 through February 1979, and the limiting nutrient was determined using regression analysis and enrichment bioassays. The surface and bottom water samples had AGP that produced increments of chemical oxygen demand (COD) of 2.1 mg l–1 and 3.1 mg l–1, respectively, on average. These values ofCOD correspond to 46% and 97% of the average COD values of the raw water samples at the surface and bottom, respectively. Seasonal changes of AGP showed a close correlation with those of dissolved inorganic nitrogen (DIN) concentration. Enrichment bioassays showed that DIN was the most deficient nutrient. The DIN:phosphate-phosphorus (PO4 3–-P) ratios and DIN: dissolved phosphorus (DP) ratios in the water samples were below the cellular N:P ratios of the natural algal populations. These results suggest that AGP was mainly limited by DIN concentration.  相似文献   

13.
Mercury, cadmium, arsenic, and antimony were analyzed in cores sampled on the Azores-Iceland Ridge. High values of 780 g · kg–1 for Hg, 1.7 g · g–1 for Cd, 87 g · g–1 for As, and 8.1 g · g–1 for Sb occur in the rift valley and transform faults. These enrichments, strictly linked to the ridge, could not have an allochtonous origin. A local hydrogenous flux may explain this phenomenon. These metallic enrichments may be connected to a hydrothermal activity extended between 43° N and 47° N.  相似文献   

14.
The activity of234Th (t 1/2=24.1 days) in dissolved, particulate and sediment trap samples was determined in the water column off southwestern Taiwan during 2–4 October, 1993. Vertical234Th fluxes measured by the free-floating sediment traps ranged from 363 to 2290 dpm m–2 d–1 in the upper 450 m. Th-234 fluxes predicted from the irreversible scavenging model concur with those measured by the sediment traps. Comparison of the residence times of particulate234Th and particulate organic carbon showed that their respective values differ by a factor of approximately 23, which suggests organic carbon is preferentially recycled relative to234Th in the euphotic zone.  相似文献   

15.
In the current study, low-background γ-spectrometry was employed to determine the 228Ra/226Ra activity ratio and 137Cs activity of 84 coastal water samples collected at six sites along the main island of Japan (Honshu Island) within the Sea of Japan, including the Tsushima Strait, and two other representative sites on Honshu Island (a Pacific shore and the Tsugaru Strait) at 1-month intervals in 2006.The 228Ra/226Ra ratio of coastal waters in the Sea of Japan exhibited similar patterns of seasonal variation, with minimum values during early summer (228Ra/226Ra = 0.6–0.8), maximum values during autumn (228Ra/226Ra = 1.5–3), and a time lag in their temporal changes ( 2.5 months and over  1300 km distance). However, the 2 other sites represented no clear periodic variation.In contrast to the positive correlation between 137Cs activity (0.6–1.7 mBq/L) and salinity (15–35), the 228Ra/226Ra ratio of coastal water samples from the Sea of Japan was not observed to correlate with salinity, and the increase in the 228Ra/226Ra ratio was not as marked (0.5–1; May–June 2004 and 2005) during the migration along Honshu Island. The input of land-derived water and/or the diffusion of radium from coastal sediments is unlikely to have affected the wide seasonal variation in the 228Ra/226Ra ratio observed in these water samples.The seasonal variation in the 228Ra/226Ra ratio recorded for the coastal waters of the Sea of Japan is considered to be mainly controlled by the remarkable changes in the mixing ratio of the 228Ra-poor Kuroshio and the 228Ra-rich continental shelf waters within the East China Sea (ECS). After passing through the Tsushima Strait, this water mass moves northeast along the coastline of the Sea of Japan as the Tsushima Coastal Branch Current (TCBC).  相似文献   

16.
Radii and angular velocities in the motions of drifting buoys deployed in the Kuroshio are estimated by fitting circles to the trajectories of two drifting buoys, one with a drogue at 300 m depth and the other at 800 m depth. The buoys were deployed in the Kuroshio where it was flowing counter-clockwise around the large cold water mass south of Honshu. The same technique was applied to two drifting buoys with drogues at 300 m depth placed in the Kuroshio where it flowed clockwise around Oshima Island in Sagami Bay. The centrifugal forces were 7% and 6% as large as the Coriolis forces in the Kuroshio around the cold water mass, and they were –56% and –42% as large as the Coriolis forces in the current around the Oshima Island. The temperature gradient observed in the Oshima-West Channel suggested that the pressure gradient there was smaller due to the centrifugal force acting against the Coriolis force than the pressure gradient to be balanced with the Coriolis force.  相似文献   

17.
From July to November, the thermocline which has strong temperature gradient (0.7C m–1) is formed in the bottom water of Beppu Bay, and it prevents the downward mixing of surface water. This has caused the bottom water of the basin to become depleted in oxygen, and in November the bottom water below about 60 m depth becomes anoxic. Accordingly manganese and iron are reduced and more soluble under the anoxic condition, those concentrations are high relative to surface water, and the maximums are 1,240g l–1 and 80g l–1. Under the anoxic condition, the flux of dissolved manganese from the sediment is about 10g cm–2 day–1.  相似文献   

18.
Primary productivity in the East China Sea and its adjacent area was measured by the13C tracer method during winter, summer and fall in 1993 and 1994. The depth-integrated primary productivity in the Kuroshio Current ranged from 220 to 350 mgC m−2d−1, and showed little seasonal variability. High primary productivity (above 570 mgC m−2d−1) was measured at the center of the continental shelf throughout the observation period. The productivity at the station nearest to the Changjiang estuary exhibited a distinctive seasonal change from 68 to 1,500 mgC m−2d−1. Depth-integrated primary productivity was 2.7 times higher in the shelf area than the rates at the Kuroshio Current. High chlorophyll-a specific productivity (mgC mgChl.-a−2d−1) throughout the euphotic zone was mainly found in the shelf area rather than off-shelf area, probably due to higher nutrient availability and higher activity of phytoplankton at the subsurface layer in the shelf area.  相似文献   

19.
The downward short- and long-wave radiation fluxes at the sea surface (S, L) were measured aboard the R/VHakuho Maru, University of Tokyo, for the period of 117 days on six cruises from 1981 to 1985 in the western North Pacific near Japan. The upward fluxes of short- and long-wave radiation (S, L) were calculated by Payne's (1972) table and the Stefan-Boltzmann's law, respectively. The sensible and laten heat fluxes (Q h ,Q e ) were also estimated from an aerodynamic bulk method.From April to August, the daily mean value ofS varied with the amplitude of 100200 Wm–2. The value ofS was estimated approximately 6% ofS in all seasons. The difference betweenL andL was so small that the net radiation flux (Q n ) was dominated byS. In addition, the net heat flux at the sea surface was also dominated byS due to small values ofQ h andQ e , and then the ocean was warmed at the rate of 111 Wm–2 in April and 63 Wm–2 in August in the Oyashio Area, and 132 Wm–2 in May and 164 Wm–2 in June in the Kuroshio Area, respectively.From September to March, a remarkable negative correlation between the day to day variation ofS and that ofL was observed except when an intense cold air outbreak occurred. It was found that the correlation was caused by the cloud climatological feature of the western North Pacific in this period.S was not a dominant factor in the net heat flux. The value ofQ h +Q e in the Kuroshio Area ranged from 260 Wm–2 to 630 Wm–2, much larger thanQ n which ranged from –8 Wm–2 to 92 Wm–2 in the leg mean values (each leg period was about 10 days). Then the ocean was cooled at the rate of –160–620 Wm–2 during this period. The net heat flux in the Kuroshio Area averaged over five legs from late November to February was –473 Wm–2. This value is 50100% larger than the climatological values reported so far.The temporal and spatial variability of radiation fluxes and heat fluxes during each leg was also discussed.  相似文献   

20.
Eutrophication has become an overwhelming phenomenon in the coastal environment off the Changjiang (Yangtze River) Estuary, illustrated by an increase in nutrient concentration, frequent red-tide events and hypoxia in near-bottom waters, while the open East China Sea Shelf and Kuroshio waters remain oligotrophic. Observations made in the Changjiang Estuary and the East China Sea in 1999–2003 cover a broad range of hydrographic and chemical properties. The concentration gradients of nutrients across the shelf indicate that high levels from land-sources are constrained to the coastal and inner-shelf region by the complex circulation regime. In surface waters, nutrient species gradually decrease from eutrophic coastal to oligotrophic open shelf waters, depending on the hydrographic stages of the Changjiang, although biological uptake and regeneration in the upper water column can produce patchy character of nutrient distribution. Taiwan Current Warm Water and Kuroshio Surface Water are devoid of nutrients. Remineralization of nutrient species takes place in the near-bottom waters in the inner-shelf following extensive bacterial demand for organic matter. Hence the burial efficiency is low with regard to the biogenic species, either allochthonous or autochthonous, or both. The Kuroshio Sub-surface Waters are rich in nutrients, and their incursion into the East China Sea can be tracked by salinity and temperature, reaching within water depth of 50–100 m at mid-shelf. Relative to shelf waters, the Kuroshio intrusion is characterized by high and DIP/DOP ratios. In the water column, the ratio of DIP/DOP to is higher than the Redfield P/N value, suggesting rapid regeneration of phosphorus relative to nitrogen in the East China Sea. The results of a box-model suggest that the East China Sea Shelf do likely not export substantial amounts of dissolved biogenic elements to the open Northwest Pacific Ocean.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号