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1.
As part of the Microbial Exchanges and Coupling in Coastal Atlantic Systems (MECCAS) Project, crab larvae were collected in the shelf waters off Chesapeake Bay in June and August 1985 and April 1986. We conducted hydrographic (temperature, salinity, nutrients) and biological (chlorophyll, copepods) mapping in conjunction with Eulerian and Lagrangian time studies of the vertical distribution of crab larvae in the Chesapeake Bay plume. These abundance estimates are used with current meter records and drifter trajectories to infer mechanisms of larval crab dispersion to the shelf waters and recruitment back into Chesapeake Bay. The highest numbers of crab larvae were usually associated with the Chesapeake Bay plume, suggesting that it was the dominant source of crab larvae to shelf waters. Patches of crab larvae also were found in the higher salinity shelf waters, and possibly were remnants of previous plume discharge events. The distribution of crab larvae in the shelf waters changed on 1–2 d time scales as a consequence of both variations in the discharge rate of the Chesapeake Bay plume and local wind-driven currents. Downwelling-favorable winds (NW) intensified the coastal jet and confined the plume and crab larvae along the coast. In April during a downwelling event (when northwesterly winds predominated), crab zoeae were transported southward along the coast at speeds that at times exceeded 168 km d−1. During June and August the upwelling-favorable winds (S, SW) opposed the anticyclonic turn of the plume and, via Ekman circulation, forced the plume and crab larvae to spread seaward. Plume velocities during these conditions generally were less than 48 km d−1. The recruitment of crab larvae to Chesapeake Bay is facilitated in late summer by the dominance of southerly winds, which can reverse the southward flow of shelf waters. Periodic downwelling-favorable winds can result in surface waters and crab larvae moving toward the entrance of Chesapeake Bay. Approximately 27% of the larval crabs spend at least part of the day in bottom waters, which have a residual drift toward the bay mouth. There appears to be a variety of physical transport mechanisms that can enhance the recruitment of crab larvae into Chesapeake Bay. 相似文献
2.
Observations of the Mobile Bay, Alabama, plume during a flood event in April 1991 reveal significant differences in the current field on either side of a front associated with the buoyant plume. During a strong southeasterly wind, turbid, low salinity water from Mobile Bay was pushed through an opening in the west side of the ebb-tidal delta and moved parallel to the coast. A stable front developed between the low salinity water of the buoyant plume (11‰) and the high salinity coastal water (>23‰) that was being forced landward by the prevailing winds. Despite the shallow water depth of 6 m, measurements of currents, temperature, and salinity show large shears and density gradients in both the vertical and the horizontal directions. At a station outside of the buoyant plume, currents at 0.5 m and 1.5 m below the surface were in the same direction as the wind. Inside the plume, however, currents at 0.5 m below the surface were parallel to the coast, 45°, off the direction of the wind and the magnitude was 45% larger than the magnitude of the surface currents outside the plume. Beneath the level of the plume, the currents were identical to the wind-driven currents in the ambient water south of the front. Our observations suggest that the wind-driven surface currents of the ambient water converged with the buoyant plume at the front and were subducted beneath the plume. The motion of the ambient coastal surface water was in the direction of the local wind stress, however, the motion of the plume had no northerly component of motion. The plume also did not show any flow toward the front, suggesting a balance between the northerly component of wind stress and the southerly component of buoyant spreading. In addition, the motion of the plume did not appear to affect the motion of the underlying ambient water, suggesting a lack of mixing between the two waters. 相似文献
3.
Brent W. Ache Kristen M. Crossett Percy A. Pacheco Jeffery E. Adkins Peter C. Wiley 《Estuaries and Coasts》2015,38(1):151-155
Our nation’s coast is a complicated management area where no single delineation provides all of the demographic statistics needed to address the full range of policy and management issues. As a result, several different coastal delineations are currently being used, yielding a variety of US coastal population statistics. This paper proposes a simple model for generating and applying coastal population statistics at the national and regional level to increase consistency in coastal policy discussions and improve public understanding of coastal issues. The model includes two major components. The first component is “the population that most directly affects the coast,” represented by the permanent US population that resides in a standard suite of Coastal Watershed Counties, where land use and water quality changes most directly impact coastal ecosystems. The second component is “the population most directly affected by the coast,” represented by the permanent US population that resides in a standard suite of Coastal Shoreline Counties that are directly adjacent to the open ocean, major estuaries, and the Great Lakes, which due to their proximity to these waters, bear a great proportion of the full range of effects from coastal hazards and host the majority of economic production associated with coastal and ocean resources. 相似文献
4.
Physico-chemical parameters, major ion chemistry and isotope composition of surface and groundwaters were determined in forested
coastal catchments and adjacent coastal plains. Results showed obvious characterisation related to physical and hydrological
setting, and highly variable spatial differences reflecting the complexities of these areas. All these coastal waters are
dominated by Na–Cl and fall on a common dilution line; hydrochemical grouping is largely due to anionic differences (Cl, SO4 and HCO3), although Na and Mg ratios also vary. Six major hydrochemical facies were determined. For groundwaters, compositional differences
are largely related to aquifer material and level of confinement; for coastal groundwaters important are tidal effects and
proximity to the shoreline. Differentiation for surface waters is mainly by drainage morphology, flow regime plus proximity
to the coast. Connectivity between water bodies is reflected by minor base flow to catchment streams, including with flood
plain wetlands, but mostly occurs in low-lying zones where there is mixing of fresh and saline water within surface water
and subterranean estuaries, or by seawater intrusion enhanced by overuse. Oxygen and hydrogen isotopic data for confined and
semi-confined groundwaters along the coast indicates local recharge; fresh surface waters in the elevated catchments are shown
to be sourced further inland plus have experienced evaporation. 相似文献
5.
The distributions of particulate elements (Al, P, Mn, Fe, Co, Cu, Zn, Cd, and Pb), dissolved trace metals (Mn, Fe, Co, Cu, Zn, and Cd), and dissolved nutrients (nitrate, phosphate, and silicic acid) were investigated in the Gulf of the Farallones, a region of high productivity that is driven by the dynamic mixing of the San Francisco Bay plume, upwelled waters, and California coastal surface waters. Particulate metals were separated into >10 and 0.4-10 μm size-fractions and further fractionated into leachable (operationally defined with a 25% acetic acid leach) and refractory particulate concentrations. Dissolved metals (< 0.4 μm pore-size filtrate) were separated into colloidal (0.03-0.4 μm) and soluble (<0.03 μm) fractions. The percent leachable particulate fractions ranged from 2% to 99% of the total particulate concentration for these metals with Mn and Cd being predominantly leachable and Fe and Al being predominantly refractory. The leachable particulate Pb concentration was associated primarily with suspended sediments from San Francisco Bay and was a tracer of the plume in coastal waters. The particulate trace metal data suggest that the leachable fraction was an available source of trace metal micronutrients to the primary productivity in coastal waters. The dissolved trace metals in the San Francisco Bay plume and freshly upwelled surface waters were similar in concentration, with the exception of Cu and Co, which exhibited relatively high concentrations in plume waters and served as tracers of this water mass. The dissolved data and estimates of the plume dynamics suggest that the impact of anthropogenic inputs of nutrients and trace metals in the San Francisco Bay plume contributes substantially to the concentrations found in the Gulf of the Farallones (10-50% of estimated upwelled flux values), but does not greatly disrupt the natural stoichiometric balance of trace metal and nutrient elements within coastal waters given the similarity in concentrations to sources in upwelled water. In all, the data from this study demonstrate that the flux of dissolved nutrients and bioactive trace metals from the San Francisco Bay plume contribute to the high and relatively constant phytoplankton biomass observed in the Gulf of the Farallones. 相似文献
6.
The Burwood landfill, which serves the city of Christchurch, New Zealand, is situated on coastal sands underlain by a sequence
of aquifers and aquitards. Groundwater flow is toward the coast, located approximately 700 m from the landfill boundary. Shortly
after completion of the first phase of the landfill, an array of wells was installed to detect any contaminant from the landfill.
Leachate was detected in the wells closest to the landfill. A shallow electromagnetic (EM31) survey was carried out between
the landfill and the coast, in order to delineate any leachate plume that may be present. On the basis of the geophysical
results, a contaminant plume and buried channels connected to the coast were identified. Leachate flow initially occurs in
what is probably a channel or pair of channels. Downgradient, the plume spreads out to the north and south as it moves eastward
toward the coast. Using the geophysical results as a guide, a new set of wells was installed to confirm the presence of high
leachate concentrations. Pore-water sampling confirms the presence of a leachate plume.
Received, June 1998 /Revised, March 1999, January 2000/Accepted, January 2000 相似文献
7.
Atlantic herring (Clupea harengus) larvae have been collected for resource monitoring purposes in the Sheepscot River in mid-coastal Maine during October–February, for the past 20 years. During this period, the larval population in the river has typically peaked in October-early November and has been composed of larvae derived from August–September spawning in eastern Maine and New Brunswick waters and from September-early October spawning along the central Maine coast. Larvae from eastern coastal spawning areas are transported to the river by the prevailing westerly coastal current. The appearance of small (≤15 mm SL) larvae in the river during December and January 1985–1989 suggested an additional time and area of origin. Aging procedures based on enumeration of daily otolith increments showed the majority of these small larvae were spawned from mid October to mid November when spawning usually occurs in western Maine coastal waters and in the vicinity of Jeffreys Ledge. Comparison of back-calculated hatching dates for small larvae collected in the river with wind direction and velocity data from mid October through November suggested that larvae were transported eastward against a weakened Gulf of Maine coastal current to the Sheepscot River by complex wind-driven surface currents that occur off the western Maine coast in the fall. *** DIRECT SUPPORT *** A01BY059 00003 相似文献
8.
Atmospheric deposition of nitrogen: Implications for nutrient over-enrichment of coastal waters 总被引：8，自引：0，他引：8
Atmospheric deposition of nitrogen (AD-N) is a significant source of nitrogen enrichment to nitrogen (N)-limited estuarine and coastal waters downwind of anthropogenic emissions. Along the eastern U.S. coast and eastern Gulf of Mexico, AD-N currently accounts for 10% to over 40% of new N loading to estuaries. Extension of the regional acid deposition model (RADM) to coastal shelf waters indicates that 11, 5.6, and 5.6 kg N ha−1 may be deposited on the continental shelf areas of the northeastern U.S. coast, southeast U.S. coast, and eastern Gulf of Mexico, respectively. AD-N approximates or exceeds riverine N inputs in many coastal regions. From a spatial perspective, AD-N is a unique source of N enrichment to estuarine and coastal waters because, for a receiving water body, the airshed may exceed the watershed by 10–20 fold. AD-N may originate far outside of the currently managed watersheds. AD-N may increase in importance as a new N source by affecting waters downstream of the oligohaline and mesohaline estuarine nutrient filters where large amounts of terrestrially-supplied N are assimilated and denitrified. Regionally and globally, N deposition associated with urbanization (NOx, peroxyacetyl nitrate, or PAN) and agricultural expansion (NH4 + and possibly organic N) has increased in coastal airsheds. Recent growth and intensification of animal (poultry, swine, cattle) operations in the midwest and mid-Atlantic regions have led to increasing amounts of NH4 + emission and deposition, according to a three decadal analysis of the National Acid Deposition Program network. In western Europe, where livestock operations have dominated agricultural production for the better part of this century, NH4 + is the most abundant form of AD-N. AD-N deposition in the U.S. is still dominated by oxides of N (NOx) emitted from fossil fuel combustion; annual NH4 + deposition is increasing, and in some regions is approaching total NO3 − deposition. In receiving estuarine and coastal waters, phytoplankton community structural and functional changes, associated water quality, and trophic and biogeochemical alterations (i.e, algal blooms, hypoxia, food web, and fisheries habitat disruption) are frequent consequences of N-driven eutrophication. Increases in and changing proportions of various new N sources regulate phytoplankton competitive interactions, dominance, and successional patterns. These quantitative and qualitative aspects of AD-N and other atmospheric nutrient sources (e.g., iron) may promote biotic changes now apparent in estuarine and coastal waters, including the proliferation of harmful algal blooms, with cascading impacts on water quality and fisheries. 相似文献
9.
G. Curtis Roegner David A. Armstrong Barbara M. Hickey Alan L. Shanks 《Estuaries and Coasts》2003,26(4):1058-1070
We investigated the distribution of meroplankton and water properties off southern Washington and simultaneously measured time series of larval abundance and water properties in two adjacent estuaries, Grays Harbor and Willapa Bay. The cruise period, in late May 1999, coincided with large variation in the alongshore wind stress that caused dynamic change in the position of the Columbia River plume, coastal upelling and downwelling, and offshore phytoplankton production. In the coastal ocean, meroplankton groups responded differently to this wind event and the associated advection of water masses. Dungeness crab (Cancer magister) megalopae were largely indifferent to the wide salinity variation, and were found throughout the surveyed area in both plume and recently upwelled waters. Megalopae of kelp crab (Pugettia producta) and hermit crab (Pagurus spp). were more abundant in upwelled water and low numbers were caught in the plume water. Barnacle cyprids appeared to track the advective transport suggesting that they may be more passively dispersed. Within the estuaries, hydrography responded rapidly and synchronously to variation in wind stress. Intrusions of both plume and newly upwelled waters were detected at estuarine sites, depending on the type of water present at the coast, indicating a tight link between the estuaries and the coastal ocean in this region. A 90-d record ofC. magister megalopae abundance was made at 3 estuarine sites using light traps. The bulk of theC. magister recruitment was limited to a relatively brief period in late May through June. Within this window, megalopae occurred in distinct pulses of 3–5 d interspaced with periods of low or zero abundance.C. magister megalopae recruited to the estuaries over a wide range of wind forcing, and were transported into the estuary within varied water types. There were no periodic patterns indicative of spring-neap tidal variations in the abundance time series. Abundance was only weakly cross-correlated between the adjacent Grays Harbor and Willapa Bay estuaries, which contrasts with the more synchronous estuarine-coastal linkages measured for water properties. These results suggest the interaction of larval aggregation size in the ocean with estuary-ocean exchange processes likely controls patterns of estuarine recruitment. 相似文献
10.
Donald R. Gunderson David A. Armstrong Yun-Bing Shi Robert A. McConnaughey 《Estuaries and Coasts》1990,13(1):59-71
Extensive trawl surveys were conducted in two large estuaries (Grays Harbor and Willapa Bay) on the Washington coast during 1983–1987, and in adjacent areas of the open coast. These surveys have shown that both English sole and Dungeness crab rely heavily on these estuaries as nursery areas, although the pattern of utilization differs substantially. Juvenile migration patterns can show substantial interannual variability and can only be delineated by concurrent surveys in both coastal and estuarine areas, conducted over a period of several years. English sole eggs and Dungeness crab larvae are released in coastal waters. Larvae of both species transform to the benthic stage in both coastal and estuarine areas, but most English sole eventually migrate into the estuaries during the first year of life, even if initial settlement is along the open coast. By the time English sole have attained a length of 55 mm (TL), most of them are found in estuaries. English sole begin emigrating from the estuaries at about 75 mm, and few remain there during the second year of life. In contrast, Dungeness crab appear to remain in the area of initial settlement throughout the first year of life. Growth is substantially faster in estuaries where 0+ crab reach a mean size of about 40 mm carapace width (CW) by September, with those off the coast are only about 14 mm CW. Juveniles remain in the area of settlement over their first winter but, in contrast to English sole, most coastal 1+ crab immigrate to estuaries to join siblings that settled there the previous year. By September of the second year, crab at about 100 mm CW emigrate to the open coast where they reach maturity. Advantages to juvenile stages that reside in estuaries are discussed in terms of accelerated growth at higher temperatures and potentially greater food supplies than found nearshore along the coast. 相似文献
11.
Steven G. Morgan Jennifer L. Fisher Skyli T. McAfee John L. Largier Seth H. Miller Megan M. Sheridan Joseph E. Neigel 《Estuaries and Coasts》2014,37(5):1269-1283
The effectiveness of larval behavior in regulating transport between well-mixed, low-inflow estuaries and coastal waters in seasonally arid climates is poorly known. We determined the flux of an assemblage of benthic crustacean larvae relative to physical conditions between a shallow estuary and coastal waters on the upwelling coast of northern California (38°18′N, 123°03′W) from 29 to 31 March 2006. We detected larval behaviors that regulate transport in adjacent coastal waters and other estuaries for only two taxa in the low-inflow estuary, but they were apparent for taxa outside the estuary. Vertical mixing in the shallow estuary may have overwhelmed larvae of some species, or salinity fluctuations may have been too slight to cue tidal vertical migrations. Nevertheless, all larval stages of species that complete development in nearshore coastal waters were present in the estuary, because they remained low in the water column reducing seaward advection or they were readily exchanged between the estuary and open coast by tidal flows. Weak tidal flows and gravitational circulation at the head of the estuary reduced seaward transport during development for species that completed development nearshore, whereas larval release during nocturnal ebb tides enhanced seaward transport for species that develop offshore. Thus, nonselective tidal processes dominated larval transport for most species back and forth between the low-inflow estuary and open coastal waters, whereas in adjacent open coastal waters, larval behavior in the presence of wind-induced shear was more important in regulating migrations between adult and larval habitats along this upwelling coast. 相似文献
12.
Kuo-Chuin Wong 《Estuaries and Coasts》1999,22(2):194-205
The buoyant discharge from Delaware Bay forms two separate branches of residual outflow near the bay mouth, one along each shore. Upon exiting the bay, the branch along the Delaware shore turns right to form the southward flowing Delaware coastal current along the inner continental shelf off the Delaware, Maryland, and Virginia coasts. CTD and thermosalinograph, data collected at the mouth of Delaware Bay over two semidiurnal tidal cycles are used to examine the hydrographic distribution at the source region of the Delaware coastal current. In this region the buoyant source water of the coastal current, is largely detached from the shoreline and confined to the top 15 m of the water column over much of the tidal cycles. The core of the coastal current's source water, as defined by the point of salinity minimum, is located over the deep channel well offshore of the Delaware coast. The separation between this buoyant water and the more saline waters right along the Delaware coast and that in the central part of the bay mouth are marked by regions of high horizontal salinity gradients. The horizontal salinity gradients around the inshore and offshore boundaries of the source water of the coastal current are intensified during the flood tide, and clearly defined fronts (with a change of 3‰ over a distance of 150 m) are present at the offshore boundary near the end of the flood tide. The structure of the mean flow and the distribution of the brackish coastal current on the inner continental shelf contribute to the persistence of stratification in the source region off the Delaware shore throughout the ebb and flood tides. In contrast, the ebb-induced stratification in the region off the New Jersey shore is quickly destroyed with the onset of the flood current. 相似文献
13.
A method is introduced for issuing tsunami warnings in the Australian region based on numerical model output. The method considers
the maximum modelled wave amplitude within pre-defined coastal waters zones and uses this as a proxy for the potential impact
on the coast. A three-level stratified warning is proposed: (1) No threat, (2) Marine threat and (3) Land threat. This method
is applied to several case studies and the resulting warning characteristics are shown. While the method has its limitations,
it is a significant improvement over current operational warning strategies, which are typically based solely on the magnitude
of the earthquake and distance from the source. 相似文献
14.
大亚湾是国家重点开发的海湾，通过对其大量实测资料的综合分析和研究表明，大亚湾有9种底质类型，除沿岸及岛屿周围颗粒较粗外，湾内浅海区主要为粘土质粉砂和粉砂质粘土，工程地质条件较好。大亚湾目前底质总体污染较小，以轻微污染为主，但湾内水体交换能力差，污染易而治理难，应倍加保护。大亚湾潜在地质灾害包括活动性地质灾害因素和限制性地质条件，主要有海岸侵蚀、沙波、断层、不规则埋藏基岩、埋藏脊、航道沟、异常堆积区和陡坎等。 相似文献
15.
The coastal marine atmosphere adjacent to large urban and industrial centers is in general strongly impacted by pollution emissions, resulting in high loading of pollutants in the ambient air. Among the airborne substances are certain trace elements from a variety of emission sources that can serve as micronutrients to marine organisms in coastal waters. High concentrations of such elements in coastal air can result in enhanced air-to-sea deposition fluxes to coastal waters. They could also be transported over the open ocean, affecting the composition of the remote marine atmosphere and then ocean ecosystems. To provide better understanding of the extent of air-to-sea deposition processes on the New Jersey coast, a heavily polluted coastal region on the US East Coast, a synthesis of observation data was carried out for selected trace elements, including Fe, Cd, Cr and Cu, derived from measurements of both size-segregated and bulk aerosol particles, as well as precipitation around the New Jersey coast. The atmospheric input of Hg was also estimated based on measurement data. Results indicated that the total deposition fluxes of most trace elements were higher in Northern coastal NJ compared to Southern coastal NJ, reflecting the differences in the source strengths of these element emissions between the two coastal regions. Dry deposition processes were more significant for common dust-derived elements, particularly Fe and Al, compared with their wet deposition fluxes. However, the processes of precipitation scavenging appeared to be more important for the elements that were often enriched in fine particles including Zn, Cu, Pb and Ni. The removal of Hg from the ambient air was overwhelmingly dominated by atmospheric wet deposition. In the future, atmospheric measurements at more sites on the NJ coast should be performed simultaneously to reduce the spatial and temporal uncertainties associated with atmospheric deposition fluxes estimated in this study. 相似文献
16.
《Applied Geochemistry》2004,19(5):645-664
Sediment and water samples from 12 saline pans on the semi-arid west coast of South Africa were analysed to determine the origin of salts and geochemical evolution of water in the pans. Pans in the area can be subdivided into large, gypsiferous coastal pans with 79–150 g/kg total dissolved salt (TDS), small inland brackish to saline (2–64 g/kg TDS) pans and small inland brine (168-531 g/kg TDS) pans that have a layer of black sulphidic mud below a halite crust. The salinity of coastal pan waters varies with the seasonal influx of dilute runoff and dissolution of relict Pleistocene marine evaporite deposits. In contrast, inland pans are local topographic depressions, bordered on the north by downslope lunette dunes, where solutes are concentrated by evaporation of runoff, throughflow and groundwater seepage. The composition of runoff and seepage inflow waters is determined by modification of coastal rainfall by weathering, calcite precipitation and ion exchange reactions in the predominantly granitic catchment soils. Evaporation of pan waters leads to precipitation of calcite, Mg–calcite, dolomite, gypsum and halite in a distinct stratigraphic succession in pan sediments. Bicarbonate limits carbonate precipitation, Ca limits gypsum precipitation and Na limits halite precipitation. Dolomitisation of calcite is enhanced by the high Mg/Ca ratio of brine pan waters. Brine pan waters evolve seasonally from Na–Cl dominated brines in the wet winter months to Mg–Cl dominated brines in the dry summer months, when 5–20 cm thick halite crusts cover pan surfaces. Pan formation was probably initiated during a drier climate period in the early Holocene. More recent replacement of natural vegetation by cultivated land may have accelerated salt accumulation in the pans. 相似文献
17.
18.
Osman A. E. Abdalla Mubarik Ali Khalifa Al-Higgi Hilal Al-Zidi Issa El-Hussain Said Al-Hinai 《Hydrogeology Journal》2010,18(6):1437-1445
Seawater intrusion and its spreading rate are the challenging problems in over-pumped coastal aquifers of arid zones like the Batinah region of Oman. The study delineates the saline plume, identifies saline/freshwater zones, and estimates the migration rate of the plume in the Al Khabourah area of the Batinah coast. Time domain electromagnetic surveys, aided by vertical electrical sounding surveys, and seismic refraction methods have defined the locus of the saline/freshwater interface in the area. The current (2007) interface position, when compared with that determined during 2002, indicates a prominent recession in the saline plume and suggests an average annual recession rate of 120 m. This recession may be attributed mainly to the recharging dam of Wadi Al Hawasinah, constructed in 1995, and the enforcement of new water resources legislation. This study reveals the shielding role of the recharging dam to counter advancing saline intrusion. 相似文献
19.
The surface layers of the Bay of Bengal along the east coast of India exhibit intricate stratification owing to the differential
distribution of freshwaters. The winter (January–February) cooling of the salinity-induced stable layers results in the development
of thermal inversions that deteriorate toward the end of the season. The study focuses on the behavior of the thermal inversions
in the light of the variable stratification and the monsoon imposed reversing coastal current. To address the associated processes,
a three-dimensional Princeton Ocean Model is applied for the east coast of India, and numerical experiments carried out to
study the means by which the thermal inversions tend to perish with the passage of winter. The model domain with variable
curvilinear grid uses input fields that comprise realistic bathymetry and initial temperature/salinity conforming to winter/specified
stratification. The surface forcing comprises wind stress and diurnal pattern air–sea heat fluxes. The body forcing is derived
from the periodic tidal elevations at the open boundaries. It has been found that the thermal inversions tend to sustain as
the equator-ward flowing East India Coastal Current (EICC) traps the cool low saline waters between Paradip and Kakinada.
The current off Paradip is weak and variable and is not a part of EICC. Consequently, in the absence of replenishment of cool
and freshsurface waters, the temperature/salinity gradients get eroded steadily. No thermal inversions are noticed south of
Kakinada because of relatively weak current with diminished vertical salinity gradient. As the nature of stratification encountered
in the bay is highly variable due to diverse reasons, the behavior of internal waves under different stratification scenarios
is also addressed. Numerical experiments indicate that the energy/amplitude of the internal waves are comparable in the surface
layers for any stratification, where as it is certain orders exalted in the deeper waters of the strong stratification scenario.
Further, it is found that the energies and pattern of the temperature oscillations conform to the nature of mixed tide at
the corresponding latitude. The underneath stratification is found to be more responsible for the generation of internal waves compared to the local stratification. This implies that the body forcing emanating from below is the cardinal contributor for the generation of internal waves.
The numerical experiment with a flat and uniform bottom showing weak manifestation of internal waves endorses the same. This
connotes that the continental slopes are an effective generator of the internal waves and the energy flux conversion of the
barotropic tide to internal waves seems to be heavily dependent on the shoaling bottom. 相似文献
20.
Ocean processes are generally large scale on the U.S. Pacific Northwest coast; this is true of both seasonal variations and event-scale upwelling-downwelling fluctuations., which are highly energetic. Coastal upwelling supplies most of the macronutrients available for production, although the intensity of upwelling-favorable wind forcing increases southward while primary production and chlorophyll are higher in the north, off the Washington coast. This discrepancy could be related to several mesoscale features: the wider, more gently sloping shelf to the north, the existence of numerous submarine canyons to the north, the availability of Columbia River plume water and sediment north of the river mouth, and the existence of a semi-permanent eddy offshore of the Strait of Juan de Fuca. We suggest that these features have important effects on the magnitude and timing of macronutrient or micronutrient delivery to the plankton. These features are potentially important as well to transport pathways and residence times of planktonic larvae and to the development of harmful algal blooms. The coastal plain estuaries, with the exception of the Columbia River, are relatively small, with large tidal forcing and highly seasonal direct river inputs that are low to negligible during the growing season. Primary production in these estuaries is likely controlled not by river-driven stratification but by coastal upwelling and exchange with the ocean. Both baroclinic mechanisms (the gravitational circulation) and barotropic ones (lateral stirring by tide and, possibly, wind) contribute to this exchange. Because estuarine hydrography and ecology are so dominated by ocean signals, the coastal estuaries, like the coastal ocean, are largely synchronous on seasonal and event time scales, though, intrusions of the Columbia River plume can cause strong asymmetries between Washington and Oregon estuaries especially during spring downwelling conditions. Water property correlation increases between spring and summer as wind forcing becomes more spatially coherent along the coast. Estuarine habitat is structure not only, by large scale forcing but also by fine scale processes in the extensive intertidal zone, such as by solar heating or differential advection by tidal, curents. 相似文献