Environmental characteristics of the Mandovi-Zuari estuarine system in Goa   总被引：1，自引：0，他引：1  

S.Z. Qasim  R. Sen Gupta 《Estuarine, Coastal and Shelf Science》1981,13(5):557-578

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Regional tectonic trends on the inner continental shelf off Konkan and Central West Coast of India     

M. V. Ramana 《Geo-Marine Letters》1986,6(1):1-5

Satellite imagery and offshore magnetic data were analysed to correlate regional tectonic elements on the inner continental shelf off Konkan and the adjacent Deccan plateau. Three statistically important lineament trends—N-S, WNW-ESE and ENE-WSW—that prevail on land are correlatable well with the offshore trends. This positive correlation suggests simultaneous deformation. The major magnetic lineament observed off Jaigad Bay, west coast of India, may be the extension of onshore lineaments. The correlation of both the offshore and onshore trends indicates that the fracture pattern of the crystalline basement has also controlled the offshore structural pattern.  相似文献   

Native aluminium (spherules and particles) in the Central Indian Basin sediments: Implications on the occurrence of hydrothermal events     

Sridhar D. Iyer  M.B.L. Mascarenhas-Pereira  B. Nagender Nath 《Marine Geology》2007,240(1-4):177-184

We have sampled particles of native aluminium (Al°) in two sediment cores from the Central Indian Basin (CIB). The cores are geographically separated but are located at the base of two seamounts. The native Al° particles occurring as grains and spherules, have an average Al content of  95% and are associated with volcanogenic–hydrothermal material. Morphologically and compositionally, the specimens are similar to those reported from the East Pacific Rise. After ruling out several processes for the presence of the native Al°, we hypothesize that during progressive melting of magma, a basaltic magma is produced which has high contents of reductants such as methane and hydrogen, and a low oxygen fugacity. During the upward migration of such magma, reduction to metallic aluminium and the formation of native Al° particles takes place.  相似文献   

Deep ocean fluxes and their link to surface ocean processes and the biological pump     

T. Rixen  M.V.S. Guptha  V. Ittekkot 《Progress in Oceanography》2005,65(2-4):240

Intense studies of upper and deep ocean processes were carried out in the Northwestern Indian Ocean (Arabian Sea) within the framework of JGOFS and related projects in order to improve our understanding of the marine carbon cycle and the ocean’s role as a reservoir for atmospheric CO₂. The results show a pronounced monsoon-driven seasonality with enhanced organic carbon fluxes into the deep-sea during the SW Monsoon and during the early and late NE Monsoon north of 10°N. The productivity is mainly regulated by inputs of nutrients from subsurface waters into the euphotic zone via upwelling and mixed layer-deepening. Deep mixing introduces light limitation by carrying photoautotrophic organisms below the euphotic zone during the peak of the NE Monsoon. Nevertheless, deep mixing and strong upwelling during the SW Monsoon provide an ecological advantage for diatoms over other photoautotrophic organisms by increasing the silica concentrations in the euphotic zone. When silica concentrations fall below 2 μmol l⁻¹, diatoms lose their dominance in the plankton community. During diatom-dominated blooms, the biological pathway of uptake of CO₂ (the biological pump) appears to be more efficient than during blooms of other organisms, as indicated by organic carbon to carbonate carbon (rain) ratios. Due to the seasonal alternation of diatom and non-diatom dominated exports, spatial variations of the annual mean rain ratios are hardly discernible along the main JGOFS transect.Data-based estimates of the annual mean impact of the biological pump on the fCO₂ in the surface water suggest that the biological pump reduces the increase of fCO₂ in the surface water caused by intrusion of CO₂-enriched subsurface water by 50–70%. The remaining 30 to 50% are attributed to CO₂ emissions into the atmosphere. Rain ratios up to 60% higher in river-influenced areas off Pakistan and in the Bay of Bengal than in the open Arabian Sea imply that riverine silica inputs can further enhance the impact of the biological pump on the fCO₂ in the surface water by supporting diatom blooms. Consequently, it is assumed that reduced river discharges caused by the damming of major rivers increase CO₂ emission by lowering silica inputs to the Arabian Sea; this mechanism probably operates in other regions of the world ocean also.  相似文献   

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin     

Chandralata Raghukumar  G. Sheelu  P. A. Loka Bharathi  Shanta Nair  C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.  相似文献   

Structure of the marine boundary layer over north western Indian Ocean during 1983 summer monsoon     

M. R. Ramesh Kumar  Y. Sadhuram  G. S. Michael  L. V. Gangadhara Rao 《Boundary-Layer Meteorology》1990,52(1-2):177-191

The spatial variability of the structure of the lower troposphere over the northwestern Indian Ocean for the period 12th July to 2nd September, 1983 has been studied using upper air data collected during the first scientific cruise of ORV Sagar Kanya.An analysis of thermodynamic structure and kinematics of the marine boundary layer for different zonal and meridional sections revealed the following features: (a) Temperature and humidity inversions were generally absent over the study area except over a few locations in the western region; (b) Large-scale subsidence was found over the central equatorial Indian Ocean; (c) The convective activity over the western Indian Ocean was found to be moderately suppressed as compared to the eastern region; (d) The zonal and meridional components of winds along the equator and 10° N zonal section exhibited a mirror-image-like distribution.  相似文献   

Chlorophyll modulation of mixed layer thermodynamics in a mixed-layer isopycnal General Circulation Model — An example from Arabian Sea and equatorial Pacific     

S. Nakamoto  S. Prasanna Kumar  J. M. Oberhuber  H. Saito  K. Muneyama  R. Frouin 《Journal of Earth System Science》2002,111(3):339-349

Western tropical Indian Ocean, Arabian Sea, and the equatorial Pacific are known as regions of intense bio-chemical-physical interactions: the Arabian Sea has the largest phytoplankton bloom with seasonal signal, while the equatorial Pacific bloom is perennial with quasi-permanent upwelling. Here, we studied three dimensional ocean thermodynamics comparing recent ocean observation with ocean general circulation model (OPYC) experiment combined with remotely sensed chlorophyll pigment concentrations from the Coastal Zone Color Scanner (CZCS). Using solar radiation parameterization representing observations that a higher abundance of chlorophyll increases absorption of solar irradiance and heating rate in the upper ocean, we showed that the mixed layer thickness decreases more than they would be under clear water conditions. These changes in the model mixed layer were consistent with Joint Global Ocean Flux Study (JGOFS) observations during the 1994-1995 Arabian Sea experiment and epi-fluorescence microscopy (EFM) on samples collected during Equatorial Pacific Ocean Climate Study (EPOCS) in November, 1988. In the Arabian Sea, as the chlorophyll concentrations peak in October (3 mg/m³) after the summer plankton bloom induced by coastal upwelling, the chlorophyll induced biological heating enhanced the sea surface temperature (SST) by as much as 0.6‡C and sub-layer temperature decreases and sub-layer thickness increases. In the equatorial Pacific, modest concentrations of chlorophyll less than 0.3 mg/m³ is enough to introduce a meridional differential heating, which results in reducing the equatorial mixed layer thickness to more than 20 m. The anomalous meridional tilting of the mixed layer bottom enhances off equatorial westward geostrophic currents. Consequently, the equatorial undercurrent transports more water from west to east. We proposed that these numerical model experiments with use of satellite andin situ ocean observations are consistent under three dimensional ocean circulation theory combined with solar radiation transfer process.  相似文献   

Hydrography of the eastern Arabian Sea during summer monsoon 2002     

D. Shankar  S. S. C. Shenoi  R. K. Nayak  P. N. Vinayachandran  G. Nampoothiri  A. M. Almeida  G. S. Michael  M. R. Ramesh Kumar  D. Sundar  O. P. Sreejith 《Journal of Earth System Science》2005,114(5):459-474

Hydrographic observations in the eastern Arabian Sea (EAS) during summer monsoon 2002 (during the first phase of the Arabian Sea Monsoon Experiment (ARMEX)) include two approximately fortnight-long CTD time series. A barrier layer was observed occasionally during the two time series. These ephemeral barrier layers were caused byin situ rainfall, and by advection of low-salinity (high-salinity) waters at the surface (below the surface mixed layer). These barrier layers were advected away from the source region by the West India Coastal Current and had no discernible effect on the sea surface temperature. The three high-salinity water masses, the Arabian Sea High Salinity Water (ASHSW), Persian Gulf Water (PGW), and Red Sea Water (RSW), and the Arabian Sea Salinity Minimum also exhibited intermittency: they appeared and disappeared during the time series. The concentration of the ASHSW, PGW, and RSW decreased equatorward, and that of the RSW also decreased offshore. The observations suggest that the RSW is advected equatorward along the continental slope off the Indian west coast.  相似文献   

Hydrothermal signature in ferromanganese oxide coatings on pumice from the Central Indian Ocean Basin     

Niyati G. Kalangutkar  Sridhar D. Iyer  Maria B. L. Mascarenhas-Pereira  B. Nagender Nath 《Geo-Marine Letters》2015,35(3):221-235

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Accumulation of sediment,organic matter and trace metals with space and time,in a creek along Mumbai coast,India     

Lina Fernandes  G.N. Nayak  D. Ilangovan  D.V. Borole 《Estuarine, Coastal and Shelf Science》2011,91(3):388-399

Two core sediment samples; one from inner part (ManI) and the other closer to the mouth (ManII); were collected from the intertidal regions of Manori, a tidally influenced creek near Mumbai, India. Both the cores were subjected to various geochemical analyses to determine parameters such as pH, sediment components, total organic carbon, total nitrogen, total phosphorus and selected metals viz., Fe, Mn, Cu, Pb, Co, Ni, Zn, Cr, Al, Ca and V. Analysis of ²¹⁰Pb activity was employed to assess the sediment deposition trend of the area. The data was further processed using factor and cluster analyses. The results indicate that the sediments from site ManI, had finer sediment composition, higher porosity, organic matter and metal contents but exhibited an erratic decline in ²¹⁰Pb activity downcore. Also ManI showed higher C:N ratio and enrichment factor values as compared to site ManII. The inner area (ManI) probably received a greater input of organic matter from the erosion of terrestrial matter as well as domestic and industrial discharge. Sediments from site ManII had typical marine organic matter composition (lower C:N ratio). The concentration of metals at this site was also low indicating the contents were getting diluted by freshwater and seawater mixing.  相似文献