International Journal of Oceanography http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Numerical Modeling of Irregular Water Wave Transformation Tue, 12 Aug 2014 10:59:28 +0000 http://www.hindawi.com/journals/ijocean/2014/563467/ Propagation of irregular water wave from deep water to a shoreline has been numerically modeled. Linear and irregular waves are considered. Model equations govern effects of shoaling, refraction, and diffraction over a varying bathymetry. The model requires the input of the incoming directional random sea at the offshore boundary. Statistical energy dissipation model is incorporated to predict realistically energy losses due to wave breaking in surf zone. Unlike most of the previous models, this model can predict wave transformation in surf zone where energy dissipation and bottom friction must be taken into consideration. The model does not have the limitation of parabolic approximation models (PAM) that are valid only in case of weak refraction. Finite difference approximations have been used to solve the governing equation. The model results are compared with experimental data for directional random wave propagation over a submerged shoal. Good agreements between the model results and experimental data are shown. Applicability of the model to real coastal areas is shown by application to coastal areas along the Nile Delta Coast, Egypt. K. M. Fassieh, O. Fahmy, and M. A. Zaki Copyright © 2014 K. M. Fassieh et al. All rights reserved. Environmental Forcing of Red Tides in the Southern Benguela Mon, 16 Jun 2014 08:11:21 +0000 http://www.hindawi.com/journals/ijocean/2014/325321/ The Southern Benguela cape upwelling plumes have inshore wind shadows prone to red tides in late summer. Their intensity and coverage are estimated by satellite fluorescence measurements in the period 1997–2012 and qualified by in situ reports. High satellite fluorescence cases are identified at daily to seasonal time scales, and characteristics of the upper ocean and lower atmosphere are studied using third generation reanalyses. A dominant feature is easterly winds over the Cape Peninsula (34°S, 18°E) induced by a ridging anticyclone-coastal low weather pattern. Over Cape Columbine (33°S), there is a wind shadow with cyclonic wind and current shear. Composite atmospheric profiles reveal a 4°C temperature inversion near 500 m that traps a coastal wind jet >6 m/s below 200 m. The composite shelf oceanography shows a relic upwelling plume below 10 m overtopped by warmer water near the coast, providing the thermal stratification needed for biotic aggregation. Data from the IPSL5 coupled climate model over the period 1980–2080 indicates that environmental conditions favoring red tides may become more frequent. Mark R. Jury Copyright © 2014 Mark R. Jury. All rights reserved. Nonlinear Evolution Equations for Broader Bandwidth Wave Packets in Crossing Sea States Mon, 09 Jun 2014 09:02:44 +0000 http://www.hindawi.com/journals/ijocean/2014/597895/ Two coupled nonlinear equations are derived describing the evolution of two broader bandwidth surface gravity wave packets propagating in two different directions in deep water. The equations, being derived for broader bandwidth wave packets, are applicable to more realistic ocean wave spectra in crossing sea states. The two coupled evolution equations derived here have been used to investigate the instability of two uniform wave trains propagating in two different directions. We have shown in figures the behaviour of the growth rate of instability of these uniform wave trains for unidirectional as well as for bidirectional perturbations. The figures drawn here confirm the fact that modulational instability in crossing sea states with broader bandwidth wave packets can lead to the formation of freak waves. S. Debsarma, S. Senapati, and K. P. Das Copyright © 2014 S. Debsarma et al. All rights reserved. Microwave Emission and Scattering from Ocean Surface Waves in the Southern Beaufort Sea Mon, 10 Mar 2014 11:29:31 +0000 http://www.hindawi.com/journals/ijocean/2014/872342/ Estimates of the relationships between geophysical variables and microwave backscatter/emission are important for the evaluation of atmosphere-ocean interaction, as well as energy, and mass transfer across this interface. We evaluate ship-based passive microwave brightness temperatures at 37 and 89 GHz and active polarimetric backscatter at 5.5 GHz (C-band), as these relate to buoy-derived ocean wave parameters for distinct wave regimes in the southern Beaufort Sea. Microwave emission and backscatter are shown to be sensitive to the ocean surface physical roughness as defined by the significant wave height , compared to wind speed. The shows significant correlation with , with the strongest correlation for the H-polarization channel at 37 and 89 GHz. Active co- and cross- polarization ratios at 40° incidence angle are associated with , with the increase proportional to . The polarimetric coherence parameter at 20° also shows an inverse relationship with because of an expected decorrelation of complex returns with greater surface roughness. Mukesh Gupta, Randall K. Scharien, and David G. Barber Copyright © 2014 Mukesh Gupta et al. All rights reserved. Ocean Circulation and Water Mass Characteristics around the Galápagos Archipelago Simulated by a Multiscale Nested Ocean Circulation Model Tue, 11 Feb 2014 06:11:41 +0000 http://www.hindawi.com/journals/ijocean/2014/198686/ Ocean circulation and water mass characteristics around the Galápagos Archipelago are studied using a four-level nested-domain ocean system (HYCOM). The model sensitivity to atmospheric forcing frequency and spatial resolution is examined. Results show, that with prescribed atmospheric forcing, HYCOM can generally simulate the major El Niño events especially the strong 1997-1998 events. Waters surrounding the archipelago show a large range of temperature and salinity in association with four different current systems. West zones of Isabella and Fernandina Islands are the largest upwelling zones, resulting from the collision of the Equatorial Undercurrent (EUC) with the islands, bringing relatively colder, salty waters to the surface and marking the location of the highest biological production. Model results, which agree well with observations, show a seasonal cycle in the transport of the EUC, reaching a maximum during the late spring/early summer and minimum in the late fall. The far northern region is characterized by warmer, fresher water with the greatest mixed layer depth as a result of Panama Current waters entering from the northeast. Water masses over the remainder of the region result from mixing of cool Peru Current waters and upwelled Cold Tongue waters entering from the east. Yanyun Liu, Lian Xie, John M. Morrison, Dan Kamykowski, and William V. Sweet Copyright © 2014 Yanyun Liu et al. All rights reserved. Noisy Reverberation Suppression Using AdaBoost Based EMD in Underwater Scenario Tue, 04 Feb 2014 07:24:09 +0000 http://www.hindawi.com/journals/ijocean/2014/563780/ Reverberation suppression is a crucial problem in sonar communications. If the acoustic signal is radiated in the water as medium then the degradation is caused due to the reflection coming from surface, bottom, and volume of water. This paper presents a novel signal processing scheme that offers an improved solution in reducing the effect of interference caused due to reverberation. It is based on the combination of empirical mode decomposition (EMD) and adaptive boosting (AdaBoost) techniques. AdaBoost based EMD filtering technique is used for reverberation corrupted chirp signal to decrease the noisy components present in the received signal. An improvement in the probability of detection is achieved using the proposed algorithm. The simulation results are obtained for various reverberation times at various SNR levels. Kusma Kumari Cheepurupalli and Raja Rajeswari Konduri Copyright © 2014 Kusma Kumari Cheepurupalli and Raja Rajeswari Konduri. All rights reserved. Bounds on Biomass Estimates and Energetic Consequences of Ctenophora in the Northeast U.S. Shelf Ecosystem Wed, 29 Jan 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijocean/2014/851809/ Previous descriptions have noted that the stomach samples of spiny dogfish, Squalus acanthias, showed a major increase in the overall occurrence and hence implied abundance of Ctenophora. This apparent and persistent gelatinous zooplankton outbreak is increasingly more common in the world’s oceans. We briefly explore the energetic ramifications of ctenophores in the spiny dogfish diet, inferring that the presence of gelatinous zooplankton represents an ambient feeding strategy. Relative to other prey, ctenophores are not a high energy density prey item. However, given varying assumptions of the amount of ctenophores consumed, they may be an important staple in the diet of spiny dogfish. We also examine the utility of using spiny dogfish as a gelatinous zooplankton sampling device. Using five calculation methodologies, we provide bounds on potential abundance and biomass estimates of ctenophores in the Northeast U.S. shelf ecosystem. We then contextualize these findings relative to the implications for the Northeast U.S. and any large marine ecosystem. Michael D. Ford and Jason S. Link Copyright © 2014 Michael D. Ford and Jason S. Link. All rights reserved. Ecology of Interstitial Faunal Assemblage from the Beaches along the Coast of Kerala, India Thu, 23 Jan 2014 07:30:44 +0000 http://www.hindawi.com/journals/ijocean/2014/284979/ A quantitative and qualitative study of interstitial fauna and environmental variables was carried out on five selected sandy beaches of the west coast of India. Species of nine interstitial taxa abound the beaches. Nematodes, harpacticoid copepods, turbellarians, and polychaetes constituted the bulk of the population. The available energy in the beaches ranged from 0.2245 to 16.08 joules/mg and the grain size varied from 0.93 to 2.88. Organic matter correlated significantly with coarse sand (Pearson correlation ; ). Organic carbon, particle size, and dissolved oxygen determined the abundance and distribution of interstitial fauna as per multivariate BIOENV analysis. Shannon Wiener diversity index was maximum at Cherai (2.027) and minimum at Sakthikulangara (1.144) beach. The value of nematode/copepod ratio (/) indicated at Sakthikulangara beach validates the increased sensitivity of harpacticoids to environmental stress. Geetha Priyalakshmi and N. R. Menon Copyright © 2014 Geetha Priyalakshmi and N. R. Menon. All rights reserved. Intermonsoon Variation of Physical Characteristics and Current Circulation along the East Coast of Peninsular Malaysia Tue, 21 Jan 2014 00:00:00 +0000 http://www.hindawi.com/journals/ijocean/2014/527587/ Data from eight cruises spanning from 2002 to 2007 are used to investigate the seasonal changes in water characteristics and current circulation in southern South China Sea along the East Coast of Peninsular Malaysia. The surveys were made during two intermonsoon periods which are during March/April and September/October. In addition, monthly sea surface temperature from Moderate Resolution Imaging Spectroradiometer (MODIS) is used to provide wider coverage of spatial and temporal for seasonality study. Overall, the area shares different physical properties between the two seasons. During September/October temperature is lower and salinity is higher compared to the data during Mac/April/May. The current along the East Coast of Peninsular Malaysia also shows seasonality, with dominant current flow southward during Mac/April and northward during September/October. Mohd Fadzil Mohd Akhir, Nur Zurairah Zakaria, and Fredolin Tangang Copyright © 2014 Mohd Fadzil Mohd Akhir et al. All rights reserved. Modulation in Ocean Primary Production due to Variability of Photosynthetically Available Radiation under Different Atmospheric Conditions Sun, 05 Jan 2014 12:48:36 +0000 http://www.hindawi.com/journals/ijocean/2014/279412/ The rate of photosynthesis primarily depends on nutrients and photosynthetically available radiation (PAR) at sea surface. Several ship cruises were carried out to measure optical, biological, and atmospheric parameters in the Arabian Sea and their variability were studied. An analytical nonspectral photosynthesis-irradiance model was used to estimate euphotic primary production (EuPP) to study its variability during cruise periods. PAR was estimated using COART model using in situ measured aerosol optical depth (AOD) to compare with in situ measured PAR. In order to understand the variability of PAR under different types of aerosol and different aerosol loading, a simulation study was carried out using COART model. EuPP was estimated for various PAR values under different aerosol loading and cloud coverage conditions. Sensitivity analysis showed that for maritime, maritime polluted, and desert aerosols, the ratio PAR/PAR0AOD has attenuated to about 11–25%, whereas it has attenuated to 44% for urban aerosol type. PAR/PARclear  sky was reduced by ~57% for high aerosol loading and for overcast sky. The decrease in EuPP under various aerosol loading and cloud coverage was observed to depend on the photoadaptation parameter. EuPP/EuPPclear  sky was reduced by 38% for maximum maritime aerosol loading and for overcast sky. Madhumita Tripathy, Mini Raman, Prakash Chauhan, and Ajai Copyright © 2014 Madhumita Tripathy et al. All rights reserved. Assessing the Continuous Impact of Tributyltin from Antifouling Paints in a Brazilian Mangrove Area Using Intersex in Littoraria angulifera (Lamarck, 1822) as Biomarker Sun, 22 Dec 2013 09:33:54 +0000 http://www.hindawi.com/journals/ijocean/2013/769415/ Intersex is a sensitive biomarker of TBT exposure and effects in littorinid gastropods and described for the mangrove periwinkle Littoraria angulifera for the first time in this study. The objective was to describe the occurrence of intersex in L. angulifera, to propose the species as a sentinel organism to assess TBT contamination, and to characterize the contamination in mangroves. The study was carried out in 2009 by sampling at 20 stations near harbors and marinas and at a reference station on the coast of Espírito Santo Estate, Brazil. At the reference station, no intersex specimens were found, while at 20 sampling stations 51% of the females exhibited different degrees of intersex development, including the occurrence of functionally sterilized females. The highest incidence of intersex and greatest intersex intensities was found in areas close to marinas and shipyards indicating that vessel-related activities are still the main source of TBT contamination. L. angulifera collected from stations in areas with well-preserved mangroves was larger than specimens collected from other areas. These differences are attributed to environmental quality and not to occurrence of intersex. The results indicate that this region is still affected by TBT contamination and that L. angulifera has the required sensitivity to be used as a bioindicator. M. B. Costa, G. C. Zamprogno, F. C. Pedruzzi, G. B. Dalbem, and M. M. P. Tognella Copyright © 2013 M. B. Costa et al. All rights reserved. Towards Chip-Based Salinity Measurements for Small Submersibles and Biologgers Wed, 27 Nov 2013 08:24:24 +0000 http://www.hindawi.com/journals/ijocean/2013/529674/ Water’s salinity plays an important role in the environment. It can be determined by measuring conductivity, temperature, and depth (CTD). The corresponding sensor systems are commonly large and cumbersome. Here, a 7.5 × 3.5 mm chip, containing microstructured CTD sensor elements, has been developed. On this, 1.5 mm2 gold finger electrodes are used to measure the impedance, and thereby the conductivity of water, in the MHz frequency range. Operation at these frequencies resulted in higher sensitivities than those at sub-MHz frequencies. Up to 14 kΩ per parts per thousand salt concentration was obtained repeatedly for freshwater concentrations. This was three orders of magnitude higher than that obtained for concentrations in and above the brackish range. A platinum electrode is used to determine a set ambient temperature with an accuracy of 0.005°C. Membranes with Nichrome strain gauges responded to a pressure change of 1 bar with a change in resistance of up to 0.21 . A linear fit to data over 7 bars gave a sensitivity of 0.1185 /bar with an of 0.9964. This indicates that the described device can be used in size-limited applications, like miniaturized submersibles, or as a bio-logger on marine animals. Jonas Jonsson, Katarina Smedfors, Leif Nyholm, and Greger Thornell Copyright © 2013 Jonas Jonsson et al. All rights reserved. The Development of SONAR as a Tool in Marine Biological Research in the Twentieth Century Thu, 14 Nov 2013 13:17:16 +0000 http://www.hindawi.com/journals/ijocean/2013/678621/ The development of acoustic methods for measuring depths and ranges in the ocean environment began in the second decade of the twentieth century. The two world wars and the “Cold War” produced three eras of rapid technological development in the field of acoustic oceanography. By the mid-1920s, researchers had identified echoes from fish, Gadus morhua, in the traces from their echo sounders. The first tank experiments establishing the basics for detection of fish were performed in 1928. Through the 1930s, the use of SONAR as a means of locating schools of fish was developed. The end of World War II was quickly followed by the advent of using SONAR to track and hunt whales in the Southern Ocean and the marketing of commercial fish finding SONARs for use by commercial fisherman. The “deep scattering layer” composed of invertebrates and fish was discovered in the late 1940s on the echo sounder records. SONARs employing high frequencies, broadband, split beam, and multiple frequencies were developed as methods for the detection, quantification and identification of fish and invertebrates. The study of fish behavior has seen some use of passive acoustic techniques. Advancements in computer technology have been important throughout the last four decades of the twentieth century. John A. Fornshell and Alessandra Tesei Copyright © 2013 John A. Fornshell and Alessandra Tesei. All rights reserved. Characterization of the Boreal Summer Upwelling at the Northern Coast of the Gulf of Guinea Based on the PROPAO In Situ Measurements Network and Satellite Data Thu, 12 Sep 2013 12:04:00 +0000 http://www.hindawi.com/journals/ijocean/2013/816561/ The boreal summer upwelling along the northern coast of the Gulf of Guinea (GG) is characterized using new in situ sea surface temperature (SST) from onset sensor and satellite TRMM Microwave Imager (TMI) datasets. This study aims to encourage intensive in situ SST measurements at the northern coast of the Gulf of Guinea. It shows good agreement between daily in situ SST and TMI SST and similar coastal upwelling onset date, end date, and durations calculated using both datasets. Interannual evolution of the onset date at four stations along the northern coast of GG indicates that the upwelling can be initiated at one cape or simultaneously at both the cape of palms and the cape of three points. It can be also initiated eastward towards Cotonou or globally off all the northern coasts of GG. Nonsignificant trend is found on upwelling onset date and end date variability. Moreover, this study shows that SST is significantly warm or cold some years. Ocean conditions during these years are related to known physical processes. Yves K. Kouadio, Sandrine Djakouré, Angora Aman, K. Eugène Ali, Vamara Koné, and Elisée Toualy Copyright © 2013 Yves K. Kouadio et al. All rights reserved. Effects of Tidal Range Variability and Local Morphology on Hydrodynamic Behavior and Salinity Structure in the Caeté River Estuary, North Brazil Sun, 08 Sep 2013 14:00:58 +0000 http://www.hindawi.com/journals/ijocean/2013/315328/ Tidal influence and local morphology on circulation and salt transport are investigated in the Caeté river estuary, a well-mixed estuary along the north coast of Brazil. Velocity, temperature, and salinity data were collected in three different locations along the estuary’s main channel, over three single, 13 h tidal cycles. The aim of this study was to investigate the relationship between tidal distortion and salinity by using classical methods of comparison of three cross-channel circulation characteristics, as well as computation of salt flux and vertical mixing. Findings indicate a flood-ebb asymmetry in currents, due to the distinct funneling morphology of the estuary, with shallow marginal areas being dominant towards the estuary head, while both stratification and shear dominate near the estuary mouth. The tidal currents enhanced vertical diffusion in the mid- and lower reaches, explaining the prevailing weakly stratified conditions, while the dominant well-mixed conditions in the upper estuary are a result of a combination of stronger flood currents and negligible vertical saline gradient. The predominant downstream salt transport supports the conclusion that there is little accumulation of salt in the Caeté river estuary. In addition, findings indicate that tidal correlation and Stokes drift are important components in the upper estuary, while tidal correlation played an important role in the middle estuary, with fluvial discharge most important in the lower estuary. Geórgenes H. Cavalcante, David A. Feary, and Björn Kjerfve Copyright © 2013 Geórgenes H. Cavalcante et al. All rights reserved. Occurrence and Distribution of a Diatom-Diazotrophic Cyanobacteria Association during a Trichodesmium Bloom in the Southeastern Arabian Sea Tue, 06 Aug 2013 13:15:33 +0000 http://www.hindawi.com/journals/ijocean/2013/350594/ Symbiotic diatom-diazotrophic cyanobacteria association (DDA) of Rhizosolenia hebetata and Rhizosolenia formosa with endosymbiotic cyanobacteria Richelia intracellularis was noticed and documented for the first time during a bloom of the cyanobacterium Trichodesmium erythraeum in the oligotrophic shelf waters along Kochi and Mangalore transects, southeastern Arabian Sea (SEAS), during spring intermonsoon (April 2012). Although the host is frequently seen, the symbiont is rarely reported in the Indian EEZ. The presence of nitrogen-fixing symbiotic association of Rhizosolenia-Richelia along with Trichodesmium erythraeum highlights the significance of DDAs on the nutrient and energy budgets of phytoplankton in the oligotrophic environments of the Arabian Sea during spring intermonsoon. T. Jabir, V. Dhanya, Y. Jesmi, M. P. Prabhakaran, N. Saravanane, G. V. M. Gupta, and A. A. M. Hatha Copyright © 2013 T. Jabir et al. All rights reserved. Occurrence of Nitrogen Fixing Cyanobacterium Trichodesmium under Elevated pCO2 Conditions in the Western Bay of Bengal Mon, 22 Jul 2013 10:38:52 +0000 http://www.hindawi.com/journals/ijocean/2013/350465/ Recent studies on the diazotrophic cyanobacterium Trichodesmium showed that increasing CO2 partial pressure (pCO2) enhances N2 fixation and growth. We studied the in situ and satellite-derived environmental parameters within and outside a Trichodesmium bloom in the western coastal Bay of Bengal (BoB) during the spring intermonsoon 2009. Here we show that the single most important nitrogen fixer in today’s ocean, Trichodesmium erythraeum, is strongly abundant in high (≥300 μatm) pCO2 concentrations. N : P ratios almost doubled (~10) at high pCO2 region. This could enhance the productivity of N-limited BoB and increase the biological carbon sequestration. We also report presence of an oxygen minimum zone at Thamnapatnam. Earlier studies have been carried out using lab cultures, showing the increase in growth rate of T. erythraeum under elevated pCO2 conditions, but to our knowledge, this study is the first to report that in natural environment also T. erythraeum prefers blooming in high pCO2 concentrations. The observed CO2 sensitivity of T. erythraeum could thereby provide a strong negative feedback to rising atmospheric CO2 but would also drive towards phosphorus limitation in a future high CO2 world. Suhas Shetye, Maruthadu Sudhakar, Babula Jena, and Rahul Mohan Copyright © 2013 Suhas Shetye et al. All rights reserved. Marine Environmental Risk Assessment of Sungai Kilim, Langkawi, Malaysia: Heavy Metal Enrichment Factors in Sediments as Assessment Indexes Sun, 07 Jul 2013 14:01:00 +0000 http://www.hindawi.com/journals/ijocean/2013/482451/ Concentrations of Cd, Co, Pb, and Zn in riverbed sediments from six sampling stations along the Sungai Kilim, Langkawi, Malaysia, were determined by using the Teflon Bomb Digestion. From this study, the concentrations of heavy metals in riverbed sediments were found ranging between 6.10 and 8.87 μg/g dry weight for Co, 0.03 and 0.45 μg/g dry weight for Cd, 59.8 and 74.9 μg/g dry weight for Zn, and 1.06 and 11.69 μg/g dry weight for Pb. From the observation, these areas were polluted by domestic waste, aquaculture, and tourism activities. For clarity, enrichment factor index was used to determine the level of sediment contamination in the study area. From this study, the average EF value is a bit high for Cd () followed by Zn (), Pb (), and lastly, Co (). Based on the contamination categories, Cd was categorised as moderately enriched, while the rest of the metals studied were in deficient-to-minimally enriched by the anthropogenic sources. Jamil Tajam and Mohd Lias Kamal Copyright © 2013 Jamil Tajam and Mohd Lias Kamal. All rights reserved. Comparative Analysis of Sea Surface Temperature Pattern in the Eastern and Western Gulfs of Arabian Sea and the Red Sea in Recent Past Using Satellite Data Tue, 04 Jun 2013 12:10:47 +0000 http://www.hindawi.com/journals/ijocean/2013/501602/ With unprecedented rate of development in the countries surrounding the gulfs of the Arabian Sea, there has been a rapid warming of these gulfs. In this regard, using Advanced Very High Resolution Radiometer (AVHRR) data from 1985 to 2009, a climatological study of Sea Surface Temperature (SST) and its inter annual variability in the Persian Gulf (PG), Gulf of Oman (GO), Gulf of Aden (GA), Gulf of Kutch (KTCH), Gulf of Khambhat (KMBT), and Red Sea (RS) was carried out using the normalized SST anomaly index. KTCH, KMBT, and GA pursued the typical Arabian Sea basin bimodal SST pattern, whereas PG, GO, and RS followed unimodal SST curve. In the western gulfs and RS, from 1985 to 1991-1992, cooling was observed followed by rapid warming phase from 1993 onwards, whereas in the eastern gulfs, the phase of sharp rise of SST was observed from 1995 onwards. Strong influence of the El Niño and La Niña and the Indian Ocean Dipole on interannual variability of SST of gulfs was observed. Annual and seasonal increase of SST was lower in the eastern gulfs than the western gulfs. RS showed the highest annual increase of normalized SST anomaly (+0.64/decade) followed by PG (+0.4/decade). Neha Nandkeolyar, Mini Raman, G. Sandhya Kiran, and Ajai Copyright © 2013 Neha Nandkeolyar et al. All rights reserved. Numerical Modeling of the Interaction of Solitary Waves and Submerged Breakwaters with Sharp Vertical Edges Using One-Dimensional Beji & Nadaoka Extended Boussinesq Equations Tue, 28 May 2013 15:30:17 +0000 http://www.hindawi.com/journals/ijocean/2013/691767/ Using one-dimensional Beji & Nadaoka extended Boussinesq equation, a numerical study of solitary waves over submerged breakwaters has been conducted. Two different obstacles of rectangular as well as circular geometries over the seabed inside a channel have been considered in view of solitary waves passing by. Since these bars possess sharp vertical edges, they cannot directly be modeled by Boussinesq equations. Thus, sharply sloped lines over a short span have replaced the vertical sides, and the interactions of waves including reflection, transmission, and dispersion over the seabed with circular and rectangular shapes during the propagation have been investigated. In this numerical simulation, finite element scheme has been used for spatial discretization. Linear elements along with linear interpolation functions have been utilized for velocity components and the water surface elevation. For time integration, a fourth-order Adams-Bashforth-Moulton predictor-corrector method has been applied. Results indicate that neglecting the vertical edges and ignoring the vortex shedding would have minimal effect on the propagating waves and reflected waves with weak nonlinearity. Mohammad H. Jabbari, Parviz Ghadimi, Ali Masoudi, and Mohammad R. Baradaran Copyright © 2013 Mohammad H. Jabbari et al. All rights reserved. C-Band Polarimetric Coherences and Ratios for Discriminating Sea Ice Roughness Wed, 22 May 2013 10:58:25 +0000 http://www.hindawi.com/journals/ijocean/2013/567182/ The rapid decline of sea ice in the Arctic has resulted in a variable sea ice roughness that necessitates improved methods for efficient observation using high-resolution spaceborne radar. The utility of C-band polarimetric backscatter, coherences, and ratios as a discriminator of ice surface roughness is evaluated. An existing one-dimensional backscatter model has been modified to two-dimensions (2D) by considering deviation in the orientation (i.e., the slopes) in azimuth and range direction of surface roughness simultaneously as an improvement in the model. It is shown theoretically that the circular coherence () decreases exponentially with increasing surface roughness. The crosspolarized coherence () is found to be less sensitive to surface roughness, whereas the copolarized coherence () decreases at far-range incidence angles for all ice types. A complete validation of the adapted 2D model using direct measurements of surface roughness is suggested as an avenue for further research. Mukesh Gupta, Randall K. Scharien, and David G. Barber Copyright © 2013 Mukesh Gupta et al. All rights reserved. Predicting Sea Surface Temperatures in the North Indian Ocean with Nonlinear Autoregressive Neural Networks Tue, 30 Apr 2013 09:17:07 +0000 http://www.hindawi.com/journals/ijocean/2013/302479/ Prediction of monthly mean sea surface temperature (SST) values has many applications ranging from climate predictions to planning of coastal activities. Past studies have shown usefulness of neural networks (NNs) for this purpose and also pointed to a need to do more experimentation to improve accuracy and reliability of the results. The present work is directed along these lines. It shows usefulness of the nonlinear autoregressive type of neural network vis-à-vis the traditional feed forward back propagation type. Neural networks were developed to predict monthly SST values based on 61-year data at six different locations around India over 1 to 12 months in advance. The nonlinear autoregressive (NAR) neural network was found to yield satisfactory predictions over all time horizons and at all selected locations. The results of the present study were more attractive in terms of prediction accuracy than those of an earlier work in the same region. The annual neural networks generally performed better than the seasonal ones, probably due to their relatively high fitting flexibility. Kalpesh Patil, M. C. Deo, Subimal Ghosh, and M. Ravichandran Copyright © 2013 Kalpesh Patil et al. All rights reserved. Internal Solitary Waves in the Brazilian SE Continental Shelf: Observations by Synthetic Aperture Radar Wed, 27 Mar 2013 18:47:36 +0000 http://www.hindawi.com/journals/ijocean/2013/403259/ We present an analysis of internal solitary waves (ISWs) on the SE Brazilian continental shelf using a set of Envisat/ASAR satellite images. For the 17-month observation period, 467 ISW packets were detected. Most of observed solitons were associated to 4–6  wind. The number of ISW packets shows a seasonal signal with a peak in summer, with higher concentration in the outer shelf in all seasons, followed by midshelf during the summer. Propagation direction of ISWs was predominantly onshore with packets separated by typical internal tide wavelengths (~10–40 km). The highest values of the barotropic tidal forcing F are concentrated at the shelf break between 200 and 500 m isobaths. These characteristics suggest that ISWs are formed from nonlinear disintegration of internal tides generated at the shelf break that propagate shoreward as interfacial internal waves. No significant change in the number of ISWs from spring to neap tides was observed in spite of significant tidal current variation (60%). Even not being a region of strong tides, this study shows that ISWs are a frequent and widespread feature, possibly playing a significant dynamic role, affecting biological production, sediment dispersion, and transport. João A. Lorenzzetti and Fabian G. Dias Copyright © 2013 João A. Lorenzzetti and Fabian G. Dias. All rights reserved. Spatiotemporal Spectral Variations of AOT in India’s EEZ over Arabian Sea: Validation of OCM-II Sun, 02 Dec 2012 14:35:02 +0000 http://www.hindawi.com/journals/ijocean/2012/473162/ We report the results of sun-photometric measurements of Aerosol Optical Thickness (AOT) in India’s Exclusive Economic Zone (EEZ) over the Arabian Sea along with synchronous Ocean Color Monitor (OCM-II) derived AOT estimates during December 12, 2009–January 10, 2010. Relatively higher values of Angstrom exponent (α) around 1.2 near coast and 0.2–0.8 in the India’s EEZ, observed during the cruise period, indicate the presence of smaller particles near the coast due to anthropogenic activities; and larger particles in the India’s EEZ due to advection of pollutants from Indian subcontinent via long-range transport. Results related to α and its derivative reveal four different aerosol types (urban-industrial, desert-dust, clean-marine, and mixed-type) with varying fraction during the study period. Surface radiative forcing due to aerosols is found to be 20 W/m2 over India’s EEZ. OCM-derived AOTs showed good corroboration with in situ measurements with a correlation coefficient of about 0.95. A reasonably good correlation was also observed between AOT and wind speed (R = 0.6); AOT and relative humidity (R = 0.58). The concurrent MODIS AOT data also agree well with those observed by the OCEANSAT (OCM-II) satellite during the campaign period. C. P. Simha, P. C. S. Devara, S. K. Saha, K. N. Babu, and A. K. Shukla Copyright © 2012 C. P. Simha et al. All rights reserved. Elastic Properties of Natural Sea Surface Films Incorporated with Solid Dust Particles: Model Baltic Sea Studies Wed, 28 Nov 2012 16:54:10 +0000 http://www.hindawi.com/journals/ijocean/2012/638240/ Floating dust-originated solid particles at air-water interfaces will interact with one another and disturb the smoothness of such a composite surface affecting its dilational elasticity. To quantify the effect, surface pressure () versus film area () isotherm, and stress-relaxation (-time) measurements were performed for monoparticulate layers of the model hydrophobic material (of μm-diameter and differentiated hydrophobicity corresponding to the water contact angles (CA) ranging from 60 to 140°) deposited at surfaces of surfactant-containing original seawater and were studied with a Langmuir trough system. The composite surface dilational modulus predicted from the theoretical approach, in which natural dust load signatures (particle number flux, daily deposition rate, and diameter spectra) originated from in situ field studies performed along Baltic Sea near-shore line stations, agreed well with the direct experimentally derived data. The presence of seawater surfactants affected wettability of the solid material which was evaluated with different CA techniques applicable to powdered samples. Surface energetics of the particle-subphase interactions was expressed in terms of the particle removal energy, contact cross-sectional areas, collapse energies, and so forth. The hydrophobic particles incorporation at a sea surface film structure increased the elasticity modulus by a factor (1.29–1.58). The particle-covered seawater revealed a viscoelastic behavior with the characteristic relaxation times ranging from 2.6 to 68.5 sec. Adriana Z. Mazurek and Stanisław J. Pogorzelski Copyright © 2012 Adriana Z. Mazurek and Stanisław J. Pogorzelski. All rights reserved. Occurrence and Distribution of Polycyclic Aromatic Hydrocarbons in Water and Sediment Collected along the Harbour Line, Mumbai, India Sun, 04 Nov 2012 09:40:45 +0000 http://www.hindawi.com/journals/ijocean/2012/403615/ This study investigated the occurrence of polycyclic aromatic hydrocarbons (PAHs) in water and sediment samples collected along the harbour line, Mumbai, India. The ∑PAHs quantified in water and sediment samples were ranged from 8.66 ng/L to 46.74 ng/L and from 2608 ng/g to 134134 ng/g dry wt., respectively. Significantly high concentration of ∑PAHs was found in water samples of Sewri and sediment samples of Mahul (). PAH concentrations detected in the present study were several folds higher than the existing sediment quality criteria suggested by various statutory agencies. The PAH composition patterns in water and sediments suggest the dominance of high molecular weight compounds and indicate important pyrolytic and petrogenic sources. The occurrence of PAHs in the marine environment has attracted the attention of the scientific community as these compounds are frequently detected in seawater and sediments at increasing levels and can have adverse health effects on marine organisms and humans. PAH concentrations detected at Sewri-Mahul site were sufficiently high to pose a risk to marine organisms if they are exposed continuously to this concentration. Hence, continuous monitoring of the ecosystem is highly warranted. V. Dhananjayan, S. Muralidharan, and Vinny R. Peter Copyright © 2012 V. Dhananjayan et al. All rights reserved. Picoplankton Community Composition by CARD-FISH and Flow Cytometric Techniques: A Preliminary Study in Central Adriatic Sea Water Wed, 08 Aug 2012 08:29:26 +0000 http://www.hindawi.com/journals/ijocean/2012/909718/ Data concerning picoplanktonic community composition and abundance in the Central Adriatic Sea are presented in an effort to improve the knowledge of bacterioplankton and autotrophic picoplankton and their seasonal changes. Flow cytometry analyses revealed the presence of two distinct bacteria populations: HNA and LNA cells. HNA cells showed an explicit correlation with viable and actively respiring cells. The study of viability and activity may increase our knowledge of the part that contributes really to the remineralization and bacterial biomass production. Authotrophic picoplankton abundance, especially picocyanobacteria, was strongly influenced by seasonality, indicating that light availability and water temperature are very important regulating factors. In terms of total carbon biomass, the main contribution came from heterotrophic bacteria with a lower contribution from autotrophic picoplankton. CARD-FISH evidenced, within the Eubacteria domain, the dominance of members of the phyla Alphaproteobacteria, with a strong contribution from SAR11clade, followed by Cytophaga-Flavobacterium and Gammaproteobacteria. The bacterial groups detected contributed differently depending when the sample was taken, suggesting possible seasonal patterns. This study documents for the first time picoplankton community composition in the Central Adriatic Sea using two different approaches, FCM and CARD-FISH, and could provide preliminary data for future studies. Anita Manti, Paola Boi, Federica Semprucci, Rosaria Cataudella, and Stefano Papa Copyright © 2012 Anita Manti et al. All rights reserved. Bioaccumulation of Polycyclic Aromatic Hydrocarbons and Mercury in Oysters (Crassostrea rhizophorae) from Two Brazilian Estuarine Zones Tue, 31 Jul 2012 10:52:45 +0000 http://www.hindawi.com/journals/ijocean/2012/838320/ Nowadays, organisms are increasingly being used in biomonitoring to assess bioavailability and bioaccumulation of contaminants. This approach can use both native and transplanted organisms in order to accomplish this task. In Brazil, most of the studies related to bioaccumulation of contaminants in oysters deal with metals. The present work employs this kind of test in Brazilian coastal estuaries (Santos and Paranaguá) to evaluate total mercury and polycyclic aromatic hydrocarbon contamination in sediments and oysters (native and caged Crassostrea rhizophorae). The methodologies employed were based on known USEPA methods. Results have shown a significant contamination in Santos sediments and consequent bioavailability of organisms. Paranaguá sediments presented lower contamination in sediments, but native oysters were able to accumulate total Hg. The experiments done with caged oysters did not show significant bioaccumulation of Hg and PAHs in the Paranaguá site, but proved to be an excellent tool to assess bioavailability in the Santos estuary since they were able to bioaccumulate up to 1,600% of total PAH in the samples from the inner part of this estuary when compared to control organisms. Multivariate statistical analyses employed to these results have separated the sites evaluated and the most contaminated samples from the least contaminated. Ronaldo J. Torres, Augusto Cesar, Camilo D. S. Pereira, Rodrigo B. Choueri, Denis M. S. Abessa, Marcos R. L. do Nascimento, Pedro S. Fadini, and Antonio A. Mozeto Copyright © 2012 Ronaldo J. Torres et al. All rights reserved. Observation of Oceanic Eddy in the Northeastern Arabian Sea Using Multisensor Remote Sensing Data Tue, 24 Jul 2012 13:45:08 +0000 http://www.hindawi.com/journals/ijocean/2012/531982/ An oceanic eddy of size about 150 kilometer diameter observed in the northeastern Arabian Sea using remote sensing satellite sensors; IRS-P4 OCM, NOAA-AVHRR and NASA Quickscat Scatterometer data. The eddy was detected in the 2nd week of February in Indian Remote Sensing satellite (IRS-P4) Ocean Color Monitor (OCM) sensor retrieved chlorophyll image on 10th February 2002, between latitude 16°90′–18°50′N and longitude 66°05′–67°60′E. The chlorophyll concentration was higher in the central part of eddy (~1.5 mg/m3) than the peripheral water (~0.8 mg/m3). The eddy lasted till 10th March 2002. NOAA-AVHRR sea surface temperature (SST) images generated during 15th February-15th March 2002. The SST in the eddy’s center (~23°C) was lesser than the surrounding water (~24.5°C). The eddy was of cold core type with the warmer water in periphery. Quickscat Scatterometer retrieved wind speed was 8–10 m/sec. The eddy movement observed southeast to southwest direction and might helped in churning. The eddy seemed evident due to convective processes in water column. The processes like detrainment and entrainment play role in bringing up the cooler water and the bottom nutrient to surface and hence the algal blooming. This type of cold core/anti-cyclonic eddy is likely to occur during late winter/spring as a result of the prevailing climatic conditions. R. K. Sarangi Copyright © 2012 R. K. Sarangi. All rights reserved. Assessment of Longitudinal Gradients in Nematode Communities in the Deep Northern Gulf of Mexico and Concordance with Benthic Taxa Thu, 14 Jun 2012 10:30:09 +0000 http://www.hindawi.com/journals/ijocean/2012/903018/ Meiobenthic nematode assemblages were examined at 16 stations along two transects on the eastern and western boundaries of the deep northern Gulf of Mexico (dNGOM) at depths of 212–3000 m. The highest abundance (297 individuals 10 cm−2) and number of genera (71) occurred at stations near the Mississippi River delta. Number of genera decreased with increasing depth, and showed differences in community composition between the east and west regions. The dominant family, Comesomatidae, was represented by Sabatieria that was present at most shallow stations but absent at greater water depths. A significant difference in nematode feeding morphology was observed between depth groups but not between the two transects at different longitudes. Patterns of nematode community structure are congruent with harpacticoid copepods. Overall, the higher abundance and diversity of nematodes in the north-central Gulf of Mexico is consistent with findings of other benthic taxa and reflects organic material loading from the Mississippi River driving deep sea communities in the Gulf. The east-west gradient in composition of nematode communities suggests that nematode assemblages have well-defined distribution patterns similar to other meiobenthic taxa in the GOM but they are not aligned in the bathymetric zones observed in macrofauna, megafauna and demersal fishes. Jyotsna Sharma, Jeffrey G. Baguley, Paul A. Montagna, and Gilbert T. Rowe Copyright © 2012 Jyotsna Sharma et al. All rights reserved.