Glaciomarine sedimentation and bottom current activity on the north-western and northern continental margins of Svalbard during the late Quaternary

Palaeo-bottom current strength of the West Spitsbergen Current (WSC) and the influence of the Svalbard-Barents Sea Ice Sheet (SBIS) on the depositional environment along the northern Svalbard margins are poorly known. Two gravity cores from the southern Yermak Plateau and the upper slope north of Nordaustlandet, covering marine isotope stage (MIS) 1 to MIS 5, are investigated. Five lithofacies, based on grain size distribution, silt/clay ratio, content and mean of sortable silt (SS), are distinguished to characterise the contourite-dominated sedimentary environments. In addition, depositional environments are described using total organic carbon (TOC), total sulphur (TS) and calcium carbonate (CaCO₃) contents of sediments. Facies A, containing coarse SS, suggests strong bottom current activity and good bottom water ventilation conditions as inferred from low TOC content. This facies was deposited during the glacial periods MIS 4, MIS 2 and during the late Holocene. Facies B is dominated by fine SS indicating weak bottom current and poor ventilation (cf. high TOC content of 1.2–1.6%), and correlates with the MIS 4/3 and MIS 2/1 transition periods. With an equal amount of clay and sand, fine SS and high content of TOC, facies C indicates reduced bottom current strength for intervals with sediment supply from proximal sources such as icebergs, sea ice or meltwater discharge. This facies was deposited during the last glacial maximum. Facies D represents mass-flow deposits on the northern Svalbard margin attributed to the SBIS advance at or near the shelf edge. Facies E sediments indicating moderate bottom current strength were deposited during MIS 5 and MIS 3, and during parts of MIS 2. This first late Quaternary proxy record of the WSC flow and sedimentation history from the northern Svalbard margin suggests that the oceanographic conditions and ice sheet processes have exerted first-order control on sediment properties.     

An artificial neural network-based response surface method for reliability analyses of <Emphasis Type="Italic">c</Emphasis>-φ slopes with spatially variable soil

This paper presents an artificial neural network (ANN)-based response surface method that can be used to predict the failure probability of c-φ slopes with spatially variable soil. In this method, the Latin hypercube sampling technique is adopted to generate input datasets for establishing an ANN model; the random finite element method is then utilized to calculate the corresponding output datasets considering the spatial variability of soil properties; and finally, an ANN model is trained to construct the response surface of failure probability and obtain an approximate function that incorporates the relevant variables. The results of the illustrated example indicate that the proposed method provides credible and accurate estimations of failure probability. As a result, the obtained approximate function can be used as an alternative to the specific analysis process in c-φ slope reliability analyses.     

Experimental study of nonlinear behaviors of a free-floating body in waves

Nonlinear behaviors of a free-floating body in waves were experimentally investigated in the present study. The experiments were carried out for 6 different wave heights and 6 different wave periods to cover a relatively wide range of wave nonlinearities. A charge-coupled device (CCD) camera was used to capture the real-time motion of the floating body. The measurement data show that the sway, heave and roll motions of the floating body are all harmonic oscillations while the equilibrium position of the sway motion drifts in the wave direction. The drift speed is proportional to wave steepness when the size of the floating body is comparable to the wavelength, while it is proportional to the square of wave steepness when the floating body is relatively small. In addition, the drift motion leads to a slightly longer oscillation period of the floating body than the wave period of nonlinear wave and the discrepancy increases with the increment of wave steepness.     

The dependence of precipitation on wind direction over the Kuroshio front in the winter East China Sea

This study investigates atmospheric responses to the directions of surface wind over the Kuroshio front in the East China Sea, using wintertime satellite-derived data sets. Composite maps of sea surface temperature, wind speed, precipitation, turbulent heat flux, surface wind divergence, and the curl of wind vectors above the atmospheric boundary layer are depicted based on the classification of intense northeasterly (along the front) and northwesterly (across the front) winds over the East China Sea. When northeasterly winds prevail, considerable precipitation occurs on the offshore side of the Kuroshio front, in contrast to periods when northwesterly winds prevail. First, the northeasterly winds strengthen above the front because of the downward transfer of momentum from the fast-moving air at higher levels and/or an adjustment of sea level pressure over the oceanic front, although the process by which the influence of the Kuroshio penetrates beyond the marine atmospheric boundary layer remains unclear. Second, a cyclonic vortex forms above the marine atmospheric boundary layer (at 850-hPa height) on the offshore side of the front, and thereafter, surface wind convergence via Ekman suction (hence, enhanced precipitation) occurs over the East China Sea shelf breaks. The northeasterly winds blow over the East China Sea when the Aleutian Low retreats to the east and when high sea level pressure covers the northern Sea of Japan.     

Temporal variations in the current structure and volume transport of the Coastal Oyashio revealed by direct current measurement

Direct current measurements by a shipboard and bottom-mounted acoustic Doppler current profiler and concurrent hydrographic observations with a CTD were conducted off southeastern Hokkaido, Japan, between January and May 2005 to reveal temporal variations in the current structure and volume transport of the Coastal Oyashio (CO). The CO, which has a baroclinic jet structure with southwestward speeds exceeding 90 cm s^?1 and a width of 7–8 km, was associated with a surface-to-bottom density front and was formed on the offshore side of the shelf break. The volume transport of CO (T _CO) was estimated by integrating the fluxes of lower-density water that was trapped against the coast along the density front represented by the 26.2 σ _θ isopycnal line. This transport decreased monotonously from 0.79 Sv (1 Sv = 10⁶ m³ s^?1) in January to 0.21 Sv in March and subsequently to 0.12 Sv in May, possibly due to the decay of the East Sakhalin Current Water in the Okhotsk Sea. Accompanied by a decrease in T _CO, the location of the jet structure associated with the density front moved toward the coast while the maximum speed of the jet decreased and the tilt of the front became more horizontal. Consequently, more saline offshore Oyashio water flowed into the deep part of the shelf area, and the current structure altered from relatively barotropic in winter to baroclinic in spring. This study is the first to estimate the observed volume transport of the CO from direct current measurements.     

Radar-based collision avoidance for unmanned surface vehicles

Unmanned surface vehicles (USVs) have become a focus of research because of their extensive applications. To ensure safety and reliability and to perform complex tasks autonomously, USVs are required to possess accurate perception of the environment and effective collision avoidance capabilities. To achieve these, investigation into realtime marine radar target detection and autonomous collision avoidance technologies is required, aiming at solving the problems of noise jamming, uneven brightness, target loss, and blind areas in marine radar images. These technologies should also satisfy the requirements of real-time and reliability related to high navigation speeds of USVs. Therefore, this study developed an embedded collision avoidance system based on the marine radar, investigated a highly real-time target detection method which contains adaptive smoothing algorithm and robust segmentation algorithm, developed a stable and reliable dynamic local environment model to ensure the safety of USV navigation, and constructed a collision avoidance algorithm based on velocity obstacle (V-obstacle) which adjusts the USV’s heading and speed in real-time. Sea trials results in multi-obstacle avoidance firstly demonstrate the effectiveness and efficiency of the proposed avoidance system, and then verify its great adaptability and relative stability when a USV sailing in a real and complex marine environment. The obtained results will improve the intelligent level of USV and guarantee the safety of USV independent sailing.     

<Emphasis Type="Italic">H-M</Emphasis> bearing capacity of a modified suction caisson determined by using load-/displacement-controlled methods

This paper presents a series of monotonically combined lateral loading tests to investigate the bearing capacity of the MSCs (modified suction caissons) in the saturated marine fine sand. The lateral loads were applied under load- and displacement-controlled methods at the loading eccentricity ratios of 1.5, 2.0 and 2.5. Results show that, in the displacement-controlled test, the deflection-softening behavior of load-deflection curves for MSCs was observed, and the softening degree of the load-deflection response increased with the increasing external skirt length or the decreasing loading eccentricity. It was also found that the rotation center of the MSC at failure determined by the load-controlled method is slightly lower than that by the displacement-controlled method. The calculated MSC capacity based on the rotation center position in serviceability limit state is relatively conservative, compared with the calculated capacity based on the rotation center position in the ultimate limit state. In the limit state, the passive earth pressures opposite the loading direction under load- and displacement-controlled methods decrease by 46% and 74% corresponding to peak values, respectively; however, the passive earth pressures in the loading direction at failure only decrease by approximately 3% and 7%, compared with their peak values.     

Retardation of angular velocity of a rotating star due to mass loss

Variations of angular velocity of a rotating star on the upper main sequence due to mass loss driven by various mechanisms, like radiation, corpuscule ejection, and stellar wind, are examined. Expressions for the variations of angular velocity are derived by considering a model of a rotating star. The theoretical results show that the angular velocity decreaseswith time due tomass loss. The obtained results are applied to a hot fast-rotating star V1182 Aql (O9 V) and to Y Cyg (B0 V).     

The Air-Coastal Sea Chemical Exchange: A Case Study on the New Jersey Coast

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.