Oceans

Unmanned surface vehicles (USVs) have emerged as a new type of marine carrier platform and are attracting increasing attention in marine geological surveying owing to their flexibility, low observability and unmanned operation. This review systematically traces the development history and current status of USVs worldwide and in China and summarizes the state of the art of USV-based marine geological survey technology from three perspectives: autonomous control, sensor integration, and data transmission and processing. Two representative applications, seafloor topographic and geomorphological surveying and sub-seafloor geophysical exploration, are examined to illustrate engineering practice. Recent advances and technological trends are then outlined in terms of cross-domain collaborative operations, upgrading of core equipment, expansion of application scenarios and standardization. Remaining challenges are analyzed, including limited adaptability to complex environments, insufficient autonomous decision-making, data quality control and the low domestic production rate of core components, and future development directions are proposed. With continued technological progress, deeper research and improvement of the relevant survey standards, USVs are expected to mature into a stand-alone technical means for marine geological surveying.

The Pacific Decadal Oscillation (PDO) is the leading mode of North Pacific sea-surface temperature variability and exerts a profound influence on marine fisheries. Focusing on Larimichthys polyactis in the East China Sea (ECS), our analysis reveals a lagged effect of the PDO on the Larimichthys polyactis catch. The PDO–catch relationship for Larimichthys polyactis in the ECS is associated with three environmental factors: kuroshio intrusion transport (KIT), chlorophyll a (Chl a), and subsurface water temperature. These findings provide a scientific basis for integrating climate information into fisheries forecasting and adaptive management for the ECS.

Recent offshore hydrocarbon discoveries along the Senegalese–Mauritanian margin increase the need to quantify oil-spill risk under the highly dynamic circulation of the southern Canary Current upwelling system. We investigate seasonal pollutant dispersion along the Senegalese Grande Côte using Lagrangian particle-tracking experiments forced by outputs from the open-source hydrodynamical ocean model CROCO. The analysis focuses on the role of wind-driven circulation, Ekman transport, and upwelling variability in controlling cross-shore and alongshore transport pathways. Results show a strong seasonal coastal circulation variability. During the cold season (January–May), intensified northerly winds drive coastal upwelling and offshore Ekman transport, enhancing divergence of surface currents and promoting the export of particles away from the coast. This regime limits particle nearshore accumulation but favors broader offshore dispersion over the continental shelf. In contrast, during the warm season (June–September), weakened upwelling-favorable winds and the establishment of anticyclonic circulation north of the Cape induce onshore transport and coastal retention. Particle-release experiments reveal enhanced trapping and accumulation along the Grande Côte during this period. The Kayar region and the Cape Verde Peninsula exhibit relatively higher pollutant exposure during the cold season, whereas the inner continental shelf along the Grande Côte becomes particularly vulnerable during the warm season. These findings suggest that seasonal wind forcing and associated Ekman dynamics have a significant influence on the trajectories of oil spills. Incorporating this variability into contingency planning is essential, as the inner continental shelf of the Senegalese Grande Côte is a dynamically sensitive, high-exposure zone under the warm-season circulation regime.