Ruo-Shan Tseng

Ship routing utilizing strong ocean currents

From the Surface Velocity Program (SVP) drifter current data, a detailed and complete track of strong ocean currents in the north-western Pacific is provided using the bin average method. The focus of this study is on the Kuroshio, the strong western boundary current of the North Pacific flowing northward along the east coast of Taiwan and then turning eastward off southern Japan. With its average flow speed of about 2 knots, the Kuroshio can significantly increase the ship’s speed for a “super-slow-steaming” container ship travelling at speeds of 12 knots between the ports of Southeast Asia and Japan. By properly utilizing knowledge of strong ocean currents to follow the Kuroshio on the northbound runs and avoid it on the return trip, considerable fuel can be saved and the transit time can be reduced. In the future, the detailed Kuroshio saving-energy route could be built into electronic chart systems for all navigators and shipping routers.

Use of Global Satellite Altimeter and Drifter Data for Ocean Current Resource Characterization

In this chapter, a general overview and characterization of ocean current resources for potential power generation in the global oceans are presented. They are based on analysis of two relatively long data sets of surface drifter-observed mixed-layer current and the satellite altimeter-derived surface geostrophic current. Spatial and temporal variations of the four most prominent western boundary currents—the Kuroshio, Mindanao, Gulf Stream, and Agulhas currents—and their available mean undisturbed ocean power densities are discussed. Several potential sites for ocean current power generation in the North Pacific , South China Sea, and Oceania are identified based on a criterion formulated by combining the frequency with which the ocean currents occur, the magnitudes of their speed, the water depths at which they occur, and their distances from the shore.

Effect of Cylindrically Shaped Atoll on Westward-Propagating Anticyclonic Eddy—A Case Study

Mesoscale anticyclonic eddies occasionally propagate westward across the Dongsha atoll situated on the continental slope in the northern South China Sea (SCS). Satellite observations of this phenomenon are used to identify eddy weakening and deforming. Stronger anticyclonic eddies are weakening within a distance of 30-120 km from the atoll. A weaker anticyclone with an eddy diameter of 120 km, a sea-level slope of 8.3 × 10-8, a Reynolds number of 17, and a slow moving speed (2.5 km/d) in the SCS can be split into two smaller eddies.

Application of Satellite Remote Sensing on the Tuna Fishery of Eastern Tropical Pacific

Tuna fishery is a major fishery in Taiwan, as in many other countries. Most of the tuna studies were based on the fish catch data, and their main subjects are related to the maximum sustainable yield of tuna. Both in managing the tuna fishery by the authorities (to maintain the size of standing stock), and in maximizing the catch per unit effort (CPUE) by fishing boats, one must know what are preferred oceanographic conditions to tuna. After analyzing tuna catch data from a few experimental fishing boats in the eastern tropical Pacific Ocean, we reached the following conclusion: (1) For predicting the fishing ground of tuna, using the mean distribution of sea surface temperature (SST) or ocean color is not better than making no-prediction, i.e. using the mean distribution of tuna catch. (2) CPUE of Big Eye tuna is higher in regions of SST in 26°C∼28°C, surface Chlorophyll a concentration around 0.2 mg/m3, surface current speed above 0.15 m/s, or higher sea surface height (SSH). Because all the marine environmental parameters may change quickly with time or in space, satellite remote sensing data can provide the near real time observation for timely predictions of tuna fishing ground in the vast ocean.

Global Energy-saving Map of Strong Ocean Currents

This study provides a global, detailed, and complete energy-saving map of strong ocean currents from the absolute geostrophic velocities calculated from satellite altimetry data, with the focus on the strong Western Boundary Currents (WBCs) in the global ocean. Theoretically, the WBCs with speeds of 2–3 knots can reduce fuel consumption by 25–50% for vessels at a sailing speed of 6 knots. The fuel savings are greater for a lower sailing speed than for a higher sailing speed. For about 1·8 million motorised fishing vessels with a lower ship speed, strong currents can evidently save fuel, time and money. Since global fishing vessels generate roughly 130 million tonnes of CO2 per annum (FAO, 2012), effective utilisation of the energy-saving map could significantly reduce CO2 emissions from ship operations.