Evolution of waves and currents over a submerged laboratory shoal

The vertically-integrated effect of interaction between waves and wave-induced currents on wave transformation over a submerged elliptic shoal was investigated based on numerical simulations of the Vincent and Briggs experiment [Vincent, C.L., Briggs, M.J., 1989. Refraction- diffraction of irregular waves over a mound. Journal of Waterway, Port, Coastal and Ocean Engineering, 115(2), pp. 269–284.]. The numerical simulations were performed using two numerical wave-current model systems: one, a combination of the wave model SWAN and the current model SHORECIRC, and the other, a combination of the wave model REF/DIF and the same current model. A time-dependent, phase-resolving wave and current model, FUNWAVE, was also utilized to simulate the experiment. In the simulations, the developed wave-induced currents defocused waves behind the shoal and brought on a wave shadow zone that showed relatively low wave height distributions. For the breaking case of monochromatic waves, the wave heights computed using FUNWAVE showed good agreement with the measurements and the resulting wave-induced currents showed a jet-like velocity distribution in transverse direction. And the computed results of the two model combinations agreed better with the measurements than the computed results obtained by neglecting wave-current interaction. However, it was found that for the case in which transverse interference pattern caused by refracted waves was strong, REF/DIF-SHORECIRC did not correctly evaluate radiation stresses, the gradients of which generate wave-induced currents. SWAN-SHORECIRC, which cannot deal with the interference patterns, predicted a jet-like wave-induced current. For breaking random wave cases, the computed results of the two model combinations and FUNWAVE agreed well with the measurements. The agreements indicate that it is necessary to take into account the effect of wave-induced current on wave refraction when wave breaking occurs over a submerged shoal.     

Subtidal Marine Algal Community and Endangered Species in Dokdo and Ulleungdo,Two Oceanic Islands in the East Sea of Korea

Ocean Science Journal - Dokdo and Ulleungdo islands harbor diverse marine algae and are therefore uniquely well-suited for research on marine algae distribution and ecological changes. However,...     

Are Juvenile Manila Clam Ruditapes philippinarum Free from Perkinsus olseni Infection in Korean Waters?

Ocean Science Journal - As a suspension feeder, Manila clam Ruditapes philippinarum (A. Adams and Reeve 1850) plays a crucial role in the coastal soft bottom ecosystem in the temperate region,...     

Spatiotemporal Distribution of Dissolved Heavy Metals in Gyeonggi Bay,Korea

In this study, we investigated the spatial and temporal distribution of heavy metals and nutrients in Gyeonggi Bay, Korea, to determine their present statu     

Comparison of Turbulent Flows and Suspended Sediment Particle Motions Simulated around a Submerged Breakwater Using RANS and LES

Beach erosion is a serious problem that can be aggravated by human-made structures, and the modeling of breaking waves near the coast and around coastal st     

Deepening of Future Aleutian Low in Ensemble Global Warming Simulations with the Kiel Climate Model

We project changes of the Aleutian Low (AL) under global warming using ensemble simulations with a fully coupled ocean-atmosphere-sea ice model, the Kiel C     

A Novel Testing Apparatus for Hydromechanical Investigation of Rocks: Geo-Sequestration of Carbon dioxide

This paper presents the design, development and application of a new multi-phase high-pressure and elevated temperature rock hydromechanical testing apparatus for the investigation of reservoir and cap rock behaviour in carbon geo-sequestration projects. The triaxial apparatus is designed to support high confining stress, injection pressures and higher temperatures to imitate the natural thermo-hydro-geomechanical conditions of deep underground geological formations. The apparatus also includes an acoustic emission device for the study of the mechanical failure behaviour of rocks under compression. The apparatus is designed to support a range of different rock specimen sizes from 34 to 54?mm in diameter. Since sequestration projects involve the injection of supercritical carbon dioxide, which is extremely sensitive to temperature and pressure, and is highly corrosive in nature, special precautions were taken in the design and manufacture of the apparatus. The data acquisition system is powered and calibrated in accordance with each of the sensors and is guided by a series of in-house developed and commercial softwares for data storage and analysis. The methodology for conducting advanced testing on cap rock and reservoir rocks with the injection of water and supercritical CO₂ is presented with the appropriate theory. Some preliminary tests have been carried out on sandstone specimens sourced from the Melbourne region using the newly designed apparatus and the results are presented in this paper.     

Extreme Sr–Nd–Pb–Hf isotopic compositions exhibited by the Tinaquillo peridotite massif,Northern Venezuela: implications for geodynamic setting

An origin of the Tinaquillo Peridotite Complex in northern Venezuela, and a model for the tectonic framework of the boundary zone between the southern Caribbean Plate margin and the South American Plate (SAP) during Late Jurassic to Mid-Cretaceous time are developed using newly measured Sr, Nd, Pb and Hf isotopic compositions as well as major and trace element geochemistry for some hornblendite veins and their spinel peridotite host rocks. Depleted geochemical characteristics, principally major element concentrations, and Nd and Hf isotopes (e.g., ε_Nd = + 27; ε_Hf = +50; ca. 3.4 Ga-Nd model age) of the Tinaquillo peridotites suggest a genetic link between this complex and the Guiana Shield farther to the south within Venezuela. Scattered zones within the Tinaquillo peridotite were overprinted by what we interpret as channelized hydrous fluids (<∼3%) derived from the eastward-dipping subduction of the Farallon Plate beneath the SAP in the Late Jurassic, leading to modification of the original Sr, Nd and Hf isotopic compositions as well as the incompatible element concentrations. The hornblendite veins have Sr, Nd, Pb and Hf isotopic compositions, falling within the range of present-day Pacific/Atlantic MORB, but trace element abundance patterns with combinations of arc- and MORB-like characteristics. These results rule out the possibility of local melting of the host peridotites to produce magmas from which the hornblendite veins formed. We suggest that during inception of the westward-dipping subduction of the Protocaribbean Plate immediately following polarity reversal in the Mid-Cretaceous, melts infiltrated the mantle lithosphere and produced the veins.     

Origin and transport of sedimentary organic matter in the Yalujiang estuary,North China

The biogeochemistry of organic matter (OM) in a macrotidal estuary, the Yalujiang River, was studied during two cruises: the flood season in August 1994 and the dry season in April 1996. Surface sediments were collected in the riverine zone (RZ), the turbidity maximum zone (TMZ), and the marine zone (MZ). The molecular distribution of the n-alkanes and fatty acid series and bulk sediment characteristics, such as C:N and δ¹³C, were used to assess differences in OM source and transport from the river upstream to the marine end member. Higher C:N values typical for terrestrial sources were observed at the upper reach for both seasons. The δ¹³C of OM in surface sediments varied from −27.3‰ to −21.6‰ in the flood season and from −26.8‰ to −31‰ in the dry season. The concentrations of n-alkanes varied between 0.3–21.4 μg g⁻¹ and the variation of fatty acids was 4.8–32.9 μg g⁻¹. The data showed mixing of terrestrial and autochthonous OM in the middle and lower reaches. The distribution of lipids (n-alkanes and Carbon Preference Index) encountered in this study confirmed the importance of terrestrial OM in the sediment samples from degraded soil material. The distribution of fatty acids suggested important phytoplankton, zooplankton, and microbial signals (short-chain and unsaturated acids; ≤C₂₀). Branched fatty acids, such as the iso- and anteiso-C₁₅ and C₁₇ compounds, relfect bacterial contributions. All samples were characterized by a high proportion of mixture inputs in both seasons. A slight decreasing trend was observed with increasing salinity except for the highest percentage of mixed fatty acids in the TMZ of the flood season. Terrestrial fatty acids were approximately 20% in the flood season and 27–46% in the dry season. Differences in hydrological conditions and primary production between the TMZ, RZ, and MZ resulted in different OM distributions, which are reflected in the sources and degree of diagenesis of the sedimentary OM. Seasonal variation may be strongly influenced by hydrological characteristics rather than primary productivity and anthropogenic activities in the Yalujiang region.