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1.
Physical oceanographic data were collected during September 1975 at stations in the shallow water (max. depth 45 m) embayments of Salonica Bay and Thermaicos Gulf, and comparisons are made with data collected during other seasons. The distribution of temperature and salinity in the water column indicated the following features: fresh surface water predominantly related to river discharge; an intermediate water mass, apparently formed by mixing between the fresh and open sea waters; a thermocline, and deep bottom water open sea characteristics. The summer distribution of density in the surface and bottom waters, and the seasonal variation in the pattern of surface salinity, suggested an anti-clockwise water circulation throughout the embayments.  相似文献   

2.
A box model of Puget Sound   总被引：1，自引：0，他引：1  
A classical two-layer box model has been used to calculate volume transports and vertical exchange coefficients for the Main Basin of Puget Sound. High river flow (January–February) and low flow (August–September) calculations, using salinity and runoff observations, show that basically two estuarine types exist within the basin under both flow conditions. Admiralty Inlet, the north entrance to the Main Basin, is similar to a partially mixed estuary with vigorous tidal mixing, so that horizontal and vertical salinity gradients are similar in winter and late summer. Within the deep main basin, two layer transports are proportional to salinity stratification and the vertical exchanges are low. Calculated summer transports are about a factor of two smaller than winter transports for the Main Basin. Model transports agree quite well with daily net transports estimated from current meters. Flushing times calculated by the model also agree with volume replacement times calculated using current meter data and by methods using oxygen deficits in the lower layer.  相似文献   

3.
Winter thermohaline properties of the northern Adriatic are analysed here with the aim of getting a better insight into dense water formation on the shelf. The hydrographic parameters collected in February in the 1967–2000 interval at two stations, the first located close to the eastern shore (station 1), and the second positioned near the Po river mouth (station 2), are compared. Two types of winter hydrographic conditions are distinguished: type A when bottom salinity and density are higher at station 1 than at station 2 and type B when these parameters are higher at station 2 than at station 1. Type A is more likely to occur in warmer and type B in colder winters. Both A and B distribution types can occur in periods when the Adriatic is under the influence of very saline waters of Mediterranean origin. Interannual changes in density are, at both stations, more dependant on haline than on thermal variations. At both stations temperature was somewhat higher in the early seventies than during the eighties and nineties, while salinity and density were lower in the early seventies and early nineties than in other years of the analysed period. By comparing the 1967–2000 changes in hydrographic conditions in February to monthly values of northern Adriatic surface fluxes and Po river discharge rates, it is shown that winter thermohaline characteristics in the region depend on processes which occur much earlier, i.e. during the previous autumn and late in spring of the preceding year, and even during the previous winter, 12 months before.  相似文献   

4.
Polycyclic aromatic hydrocarbon (PAH) distributions and sources are characterized in 96 sediment samples from 24 210Pb-dated cores collected at locations in the greater Puget Sound. The highest PAH concentrations are found within a few kilometers of several sources including industrial facilities in northern Puget Sound, urban areas in central Puget Sound, and river systems draining coal-bearing strata. Regional patterns of combustion-derived PAH in surficial sediments indicate little atmospheric or waterborne exchange of PAH between different regions of the Sound. Significant subsurface maxima in combustion-derived PAH concentrations (210Pb dated at the 1950s) occur only in sediment cores collected near urban centers. Perylene apparently derives from erosion of a terrestrial source with little or no evidence of in situ production at depth in sediment cores. Coal fragments are carriers of a characteristic suite of alkylated phenanthrene, chrysene, and picene derivatives concentrated near river mouths in central and southern Puget Sound.  相似文献   

5.
Circulation in typical fjords is characterized by a shallow brackish layer at the surface over a deep long and narrow saltwater column. This surface layer is responsible for the outflow of water from the fjord and is important for flushing of the basin and water quality maintenance. The vertical structure of circulation and transport is known to be easily disrupted, and we postulate that the stability of fjordal circulation may also be vulnerable to impacts from anthropogenic alterations, such as floating structures, which could constrict the mixing and transport in the upper layers of the water column. First, using simplified fjord geometry and a three-dimensional finite volume coastal ocean model (FVCOM), a baseline examination of tidally averaged current profiles in basins with and without sills is presented. The response, varying from a partially mixed estuary regime to classical fjord conditions matches many fjord-like basins such as those in Puget Sound, Washington. The effect of surface obstruction on tidally averaged currents and residence times was then examined by incorporation of a narrow block in the surface layer of the model across the width of the simplified fjord channel such that normal velocity in the horizontal direction was forced to zero. This block approximated the presence of a floating bridge and was further tested using the geometry of Hood Canal, a fjordal sub-basin with a sill in Puget Sound. The results show that tidally averaged mean outflow under the influence of such a constraint at the water surface could be reduced significantly. In the case of Hood Canal, preliminary results indicate that the presence of the floating bridge might have increased the residence times in the basin by 8–13%, which could be an important factor affecting water quality.  相似文献   

6.
A one year long monthly sampling series at a fixed station was combined with a high-spatial resolution survey (May 2003) to investigate factors controlling zooplankton distribution in the south-eastern corner of the Bay of Biscay. Species abundance and gonad maturity for Calanoides carinatus and Calanus helgolandicus were estimated to clarify whether the observed spatial patterns were attributable to increased population growth or to mechanical accumulation. The two studies included distinct oceanographic regimes. The eastern corner of the grid was characterized by Adour river plume waters and the Cap Breton canyon, and the rest of the area by an alternating pattern of physical convergences and divergences. In the river plume, the zooplankton community diversity and abundances were highest in response to the nutrient enriched river plume waters and the submarine canyon. In the rest of the area, distribution and abundance patterns were the result of a combination of behaviour and physical transport.  相似文献   

7.
In the Central South Brazil Bight, a multispecific demersal trawl fishery is conducted by trawlers licensed for the industrial pink shrimp (Penaeus paulensis and Penaeus brasiliensis) fishery. In addition to the pink shrimp, many by-catch species have become increasingly valued in the last two decades. In spite of the importance of this multispecific fishery, the oceanographic characteristics of the inner continental shelf, onshore the 100 m isobath, are poorly known. In this paper we present, for the fist time, monthly oceanographic records taken from December 1995 to May 1997 with the R/V ‘Diadorim’ at two of the main fishing grounds of this region. Water temperature data showed the formation of a strong thermocline during summer, from November to April. This thermal gradient, due to the South Atlantic central water (SACW) intrusion that reaches these shallow waters, disappeared with the homogenization of the water column during autumn and winter, from May to September. This cold and low salinity water does not originate from local river discharges, but also represents an advection of sub-Antartic water mass. After this and during spring, a new thermocline develops, reaching its maximal expression from February to March. A maximal gradient was registered in February 1997, when the temperature dropped from 26°C at 7 m to 16°C at 14 m depth. This result shows that the SACW intrusion is a large-scale phenomenon that regularly influences the whole inner continental shelf up to 20 m. Demersal fishing grounds located in this area were covered during summer by a cold and nutrient-rich mass of water that resulted in an unusual maximum of chlorophyll a values near the bottom (30 m). The homogenization of the water column and the presence of another cold water mass during winter resulted in a strong semi-annual thermal cycle on the bottom. The role of this important oceanographic process in fishery production and dynamics deserves further investigation, but the data presented here show evidence for the importance of this phenomenon.  相似文献   

8.
The phenomenon of nutrient maximums at 70～200 m occurred only in the region of the Canada Basin among the world oceans. The prevailing hypothesis was that the direct injection of the low-temperature high-nutrient brines from the Chukchi Sea shelf (＜50 m) in winter provided the nutrient maximums. However, we found that there are five problems in the direct injection process. Formerly Jin et al. considered that the formation of nutrient maximums can be a process of locally long-term regeneration. Here we propose a regeneration-mixture process. Data of temperature, salinity, oxygen and nutrients were collected at three stations in the southern Canada Basin during the summer 1999 cruise. We identified the cores of the surface, near-surface, potential temperature maximum waters and Arctic Bottom Water by the diagrams and vertical profiles of salinity, potential temperature, oxygen and nutrients. The historical 129Ⅰ data indicated that the surface and near-surface waters were Pacific-origin, but the waters below the potential temperature maximum core depth was Atlantic-origin. Along with the correlation of nutrient maximums and very low oxygen contents in the near-surface water, we hypothesize that, the putative organic matter was decomposed to inorganic nutrients; and the Pacific water was mixed with the Atlantic water in the transition zone. The idea of the regeneration-mixture process agrees with the historical observations of no apparent seasonal changes, the smooth nutrient profiles, the lowest saturation of CaCO3 above 400 m, low rate of CFC-11 ventilation and 3H-3He ages of 8～18 a around the nutrient maximum depths.  相似文献   

9.
River plumes are the regions where the most intense river-sea-land interaction occurs, and they are characterized by complex material transport and biogeochemical processes. However, due to their highly dynamic nature, global river plume areas have not yet been determined for use in synthetic studies of global oceanography. Based on global climatological monthly averaged salinity data from the NOAA World Ocean Atlas 2009 (WOA09), and monthly averaged salinity contour maps of the East and South China Seas from the Chinese Marine Atlas, we extract the monthly plume areas of major global rivers using a geographic information system (GIS) technique. Only areas with salinities that are three salinity units lower than the average salinity in each ocean are counted. This conservative estimate shows that the minimum and maximum monthly values of the total plume area of the world’s 19 largest rivers are 1.72 × 10 6 km 2 in May and 5.38 × 10 6 km 2 in August. The annual mean area of these river plumes (3.72 × 10 6 km 2 ) takes up approximately 14.2% of the total continental shelves area worldwide (26.15 × 10 6 km 2 ). This paper also presents river plume areas for different oceans and latitude zones, and analyzes seasonal variations of the plume areas and their relationships with river discharge. These statistics describing the major global river plume areas can now provide the basic data for the various flux calculations in the marginal seas, and therefore will be of useful for many oceanographic studies.  相似文献   

10.
Extremely low summer sea-ice coverage in the Arctic Ocean in 2007 allowed extensive sampling and a wide quasi-synoptic hydrographic and δ18O dataset could be collected in the Eurasian Basin and the Makarov Basin up to the Alpha Ridge and the East Siberian continental margin. With the aim of determining the origin of freshwater in the halocline, fractions of river water and sea-ice meltwater in the upper 150 m were quantified by a combination of salinity and δ18O in the Eurasian Basin. Two methods, applying the preformed phosphate concentration (PO*) and the nitrate-to-phosphate ratio (N/P), were compared to further differentiate the marine fraction into Atlantic and Pacific-derived contributions. While PO*-based assessments systematically underestimate the contribution of Pacific-derived waters, N/P-based calculations overestimate Pacific-derived waters within the Transpolar Drift due to denitrification in bottom sediments at the Laptev Sea continental margin.Within the Eurasian Basin a west to east oriented front between net melting and production of sea-ice is observed. Outside the Atlantic regime dominated by net sea-ice melting, a pronounced layer influenced by brines released during sea-ice formation is present at about 30–50 m water depth with a maximum over the Lomonosov Ridge. The geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the Transpolar Drift.The ratio of sea-ice derived brine influence and river water is roughly constant within each layer of the Arctic Ocean halocline. The correlation between brine influence and river water reveals two clusters that can be assigned to the two main mechanisms of sea-ice formation within the Arctic Ocean. Over the open ocean or in polynyas at the continental slope where relatively small amounts of river water are found, sea-ice formation results in a linear correlation between brine influence and river water at salinities of about 32–34. In coastal polynyas in the shallow regions of the Laptev Sea and southern Kara Sea, sea-ice formation transports river water into the shelf’s bottom layer due to the close proximity to the river mouths. This process therefore results in waters that form a second linear correlation between brine influence and river water at salinities of about 30–32. Our study indicates which layers of the Arctic Ocean halocline are primarily influenced by sea-ice formation in coastal polynyas and which layers are primarily influenced by sea-ice formation over the open ocean. Accordingly we use the ratio of sea-ice derived brine influence and river water to link the maximum in brine influence within the Transpolar Drift with a pulse of shelf waters from the Laptev Sea that was likely released in summer 2005.  相似文献   

11.
Geochemical, sedimentological, and mineralogical data suggest that local geological and oceanographic conditions favor the formation of Fe, Ti, and Cr placer deposits near the mouths of some of the rivers on the Cyprus continental shelf. Generally, the deposits are associated with finer and better sorted sands to the west of the river mouths. This is a reflection of the prevailing water movements. Metallic ore minerals of the deposits have their source in the mafic and ultramific rocks of the Troodos ophiolite complex. Although the Ezousas and Xeropotamos areas display sedimentological patterns similar to those prevailing at locations where placer deposits are found, the distance of these beaches from the source rocks accounts for the lack of economic placers at these two sites.  相似文献   

12.
We here investigate the frequency and intensity of oscillations in oceanographic data within intraseasonal time scales using spectral analysis of surface wind and wave time-series data collected at off-island weather stations or moored buoys around Taiwan. Data from marine weather stations were used to trace atmospheric conditions, while we used buoy data to examine sea states. The spectra and wavelet scalogram of the wind fields revealed oscillations with a period of around 20–33 days, and the energy density of the wind field at the off-island stations was stronger than that at the data buoy stations. However, the wavelet scalogram of the wave height measured at the buoy stations was stronger than its associated wind field. This long-period oscillation is consistent with the wavelet scalogram of the wind field calculated from the off-island weather stations. About 20–33 day oscillations exist within intraseasonal variations, which are closely linked to the atmospheric environment and to wind and ocean wave fields. Oscillations with a period of 5–10 days are a pronounced feature over northeastern Taiwan waters during the winter season and can be interpreted as the wave pattern following synoptic weather systems.  相似文献   

13.
Through extensive field data collection and analysis efforts conducted since the 1950s, researchers have established an understanding of the characteristic features of circulation in Puget Sound. The pattern ranges from the classic fjordal behavior in some basins, with shallow brackish outflow and compensating inflow immediately below, to the typical two-layer flow observed in many partially mixed estuaries with saline inflow at depth. An attempt at reproducing this behavior by fitting an analytical formulation to past data is presented, followed by the application of a three-dimensional circulation and transport numerical model. The analytical treatment helped identify key physical processes and parameters, but quickly reconfirmed that response is complex and would require site-specific parameterization to include effects of sills and interconnected basins. The numerical model of Puget Sound, developed using unstructured-grid finite volume method, allowed resolution of the sub-basin geometric features, including presence of major islands, and site-specific strong advective vertical mixing created by bathymetry and multiple sills. The model was calibrated using available recent short-term oceanographic time series data sets from different parts of the Puget Sound basin. The results are compared against 1) recent velocity and salinity data collected in Puget Sound from 2006 and 2) a composite data set from previously analyzed historical records, mostly from the 1970s. The results highlight the ability of the model to reproduce velocity and salinity profile characteristics, their variations among Puget Sound sub-basins, and tidally averaged circulation. Sensitivity of residual circulation to variations in freshwater inflow and resulting salinity gradient in fjordal sub-basins of Puget Sound is examined.  相似文献   

14.
A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pollutants. It is focused on answering the following questions: (1) What role does the estuarine plume front in the winter play in affecting the pollutants transport and its distribution in the PRE? (2) What effect do the coastal currents driven by the monsoon have on the pollutants transport? The tracer experiment results show that: (1) the pollutant transport paths strongly depend on the circulation structures and plume frontal dynamics of the PRE and coastal waters; (2) during the summer when a southwesterly monsoon prevails, the pollutants from the four easterly river inlets and those from the bottom layer of offshore stations will greatly influence the water quality in Hong Kong waters, however, the pollutants released from the four westerly river-inlets will seldom affect the water quality of Hong Kong waters due to their transport away from Hong Kong; (3) during the winter when a northeasterly monsoon prevails, all pollutants released from the eight river gates will be laterally transported seaward inside the estuary and transport westward in the coastal waters along the river plume frontal zone. However, pollutants released from the surface layer of offshore stations near or east of the Dangan Channel will be carried into the coastal waters of Hong Kong by the landward component of the westward coastal current driven by the winter northeasterly monsoon. But the pollutants from the bottom layer of the offshore stations will be carried away from the offshore by the bottom flow driven by the northeasterly monsoon. This implies that only surface-released matter from offshore stations will affect the water quality of the coastal waters around Hong Kong during the winter when a northeasterly monsoon prevails.  相似文献   

15.
A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pollutants. It is focused on answering the following questions: (1) What role does the estuarine plume front in the winter play in affecting the pollutants transport and its distribution in the PRE ? (2) What effect do the coastal currents driven by the monsoon have on the pollutants transport? The tracer experiment results show that: (1) the pollutant transport paths strongly depend on the circulation structures and plume frontal dynamics of the PRE and coastal waters; (2) during the summer when a southwesterly monsoon prevails, the pollutants from the four easterly river inlets and those from the bottom layer of offshore stations will greatly influence the water quality in Hong Kong waters, however, the pollutants released from the four westerly river-inlets will seldom affect the water quality of Hong Kong waters due to their transport away from Hong Kong; (3) during the winter when a northeasterly monsoon prevails, all pollutants released from the eight river gates will be laterally transported seaward inside the estuary and transport westward in the coastal waters along the river plume frontal zone. However, pollutants released from the surface layer of offshore stations near or east of the Dangan Channel will be carried into the coastal waters of Hong Kong by the landward component of the westward coastal current driven by the winter northeasterly monsoon. But the pollutants from the bottom layer of the offshore stations will be carried away from the offshore by the bottom flow driven by the northeasterly monsoon. This implies that only surface-released matter from offshore stations will affect the water quality of the coastal waters around Hong Kong during the winter when a northeasterly monsoon prevails.  相似文献   

16.
Onega Bay waters are characterized by a high content of chromophoric dissolved organic matter (CDOM). The absorbance spectra and fluorescence intensity (excitation wavelength 455 nm, emission wavelength >680 nm) were used to assess the distribution of CDOM content in water filtered through a GF/F filter. The CDOM content at different points in Onega Bay showed more than a fourfold difference, as inferred from the measured values. The CDOM content in surface waters was, as a rule, higher than in the deeper horizons. A higher CDOM content was measured near the Onega River, near the middle part of the Onega shore, and near the Pomor shore opposite the town of Belomorsk. River runoff is the major source of CDOM in Onega Bay water. The CDOM chemical composition in Onega Bay waters was heterogeneous. The ratio of the fluorescence intensity to the absorbance value was higher near the mouths of rivers and in intensive mixing zones than in water characterized by high salinity. A highly significant linear correlation (R2 = 0.7825) between water salinity and CDOM fluorescence intensity was demonstrated. The contribution of fluorescent compounds to river runoff CDOM is substantially higher than the contribution to the composition marine CDOM.  相似文献   

17.
《Marine Chemistry》2001,73(1):37-51
Vertical profiles of 14C-uptake were acquired monthly from the mouths and landward stations of periodically anoxic Saanich Inlet and oxygenated Jervis Inlet, British Columbia, Canada from August 1985 to October 1989. Saanich Inlet (490 g C m−2 year−1) was 1.7 times more productive than Jervis Inlet (290 g C m−2 year−1) and primary production toward the mouths of both inlets was 1.4 times higher than at the landward stations. The elevated rates of primary production in Saanich Inlet may have been due to exchange with the nutrient-rich surface waters of the passages leading to the Pacific Ocean and the up-inlet gradients in both fjords also may have reflected relative nutrient supply. Sediment-trap results show enhanced fluxes of biogenic silica to the deep waters of Saanich Inlet; associated organic matter is likely to have caused a large oxygen demand. Combined with the high primary production and export flux, low rates of vertical mixing and particle-entrapment within the fjord, factors associated with weak estuarine circulation as well as weak winds and tides in Saanich Inlet, may also stimulate anoxia.Although in Jervis Inlet there is more stagnant water behind the sill and deep-water renewals appear to be less frequent than in Saanich Inlet, the deep sill allows degradation of a significant fraction of the sinking organic matter before the stagnant waters are reached, reducing the chances of oxygen depletion in the bottom waters.  相似文献   

18.
The effect of climate change on natural oyster recruitment has the potential to disrupt many of the ecosystem services oysters provide. Due to the temperature‐sensitivity of reproduction, oyster recruitment may shift as water temperatures rise. A biological imprint of climate change was revealed in a multi‐decadal time series of recruitment of non‐native Pacific oysters (Crassostrea gigas) in the main stem of Hood Canal, Washington, USA, extracted from historic fishery documents. Water in July and August warmed significantly from 1945 to 1995 (0.028 ± 0.004°C per year [±SE]) and accounted for an increase in Pacific oyster recruitment (7% per year, 0.028 ± 0.006 spat per year on log scale [±SE]); recruitment also strongly tracked inter‐annual variability in summer water temperature. Methods used to collect historical data were repeated in 2013–2015 when recruitment of both Pacific oysters and native Olympia oysters (Ostrea lurida) were recorded in main stem and lower Hood Canal. Both historic and modern data show large variation within and between years for temperature as well as recruitment. The modern data add information regarding spatial variation, in that recruitment patterns in the two regions of Hood Canal were decoupled. As temperatures continue to increase, non‐native Pacific oysters are likely to be favored over Olympia oysters, which recruit earlier at lower temperatures and presently contribute less than half of total oyster recruits. Future recruitment, however, may be limited by environmental factors other than temperature, a point indicated particularly in Hood Canal where many subtidal species already respond strongly to gradients in dissolved oxygen.  相似文献   

19.
We compiled and analyzed past time-series data to evaluate changes in oceanographic conditions and marine ecosystems near the Ieodo ocean research station (IORS) in the East China Sea (N 31°15??C33°45??, E 124°15??C127°45??) in relation to longterm changes in climate and global warming. The environment data we used was a depth-specific time-series of temperature and salinity for the water columns at 175 fixed stations along 22 oceanographic lines in Korean waters, based on bimonthly measurements since 1961 taken by the National Fisheries Research & Development Institute. As an indicator for the ecosystem status of the waters off Ieodo, we analyzed species composition in biomass of fishes caught by Korean fishing vessels in the waters near the IORS (1984?C2010) and summarized the data in relation to the environmental changes using canonical correspondence analysis (CCA). To detect step changes in the time-series of environmental factors, we applied a sequential t-test analysis of regime shift. Correspondence analysis detected a major shift in fish assemblage structure between 1990 and 1993: the dominant species was filefish during 1981?C1992, but chub mackerel during 1992?C2007. This shift in fish assemblage structure seemed to be related to the well-established 1989 regime shift in the North Pacific, which was confirmed again with respect to temperature in the Yellow Sea and the Korea Strait (but not in the waters off the IORS). In overall from 1984 to 2010, salinity was more important than water temperature in CCA, implying that the fluctuation of the Tsushima warm current is a most important force driving the long-term changes in fish assemblage structure in the waters off the IORS. Further multidisciplinary researches are required to identify oceanographic and biological processes that link climate-driven physical changes to fish recruitment and habitat range fluctuations.  相似文献   

20.
A combination of δ~(18)O and salinity data was employed to explore the freshwater balance in the Canada Basin in summer 2008.The Arctic river water and Pacific river water were quantitatively distinguished by using different saline end-members.The fractions of total river water,including the Arctic and Pacific river water,were high in the upper 50 m and decreased with depth as well as increasing latitude.In contrast,the fraction of Pacific river water increased gradually with depth but decreased toward north.The inventory of total river water in the Canada Basin was higher than other arctic seas,indicating that Canada Basin was a main storage region for river water in the Arctic Ocean.The fraction of Arctic river water was higher than Pacific river water in the upper 50 m while the opposite was true below 50 m.As a result,the inventories of Pacific river water were higher than those of Arctic river water,demonstrating that the Pacific inflow through the Bering Strait is the main source of freshwater in the Canada Basin.Both the river water and sea-ice melted water in the permanent ice zone were more abundant than those in the region with sea-ice just melted.The fractions of total river water,Arctic river water,Pacific river water increased northward to the north of 82°N,indicating an additional source of river water in the permanent ice zone of the northern Canada Basin.A possible reason for the extra river water in the permanent ice zone is the lateral advection of shelf waters by the Trans-Polar Drift.The penetration depth of sea-ice melted waters was less than 30 m in the southern Canada Basin,while it extended to 125 m in the northern Canada Basin.The inventory of seaice melted water suggested that sea-ice melted waters were also accumulated in the permanent ice zone,attributing to the trap of earlier melted waters in the permanent ice zone via the Beaufort Gyre.  相似文献   

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