The Kuroshio–Oyashio Transition Zone (KOTZ) serves as a vital dynamic interface between the warm Kuroshio Extension and the cold Oyashio Current. However, severe sea conditions with strong ocean currents, winds and waves pose challenges for sustained in situ observations of both oceanic and atmospheric variables. This paper introduces the China Kuroshio Extension Observatory (CKEO), a moored observatory program designed for long-term observations in the KOTZ. We provide a dataset of meteorological and oceanographic properties, including sea surface wind, air temperature, atmospheric pressure, relative humidity, sea surface temperature, sea surface salinity, ocean currents in the upper 100 m, and temperature profile in the upper 500 m. The CKEO, which began operations in 2019, provides a continuous air–sea observational dataset of the KOTZ to the scientific community and advances the understanding of multiscale physical processes in this region.

The South China Sea Meridional Overturning Circulation (SCSMOC), a key prominent component of the Pacific meridional overturning circulation, features two profound circulation cells (upper and deep cells) in the vertical direction. Variations in the SCSMOC play a significant role in regulating meridional heat transport within the SCS and influencing the broader Pacific Ocean water cycle. For instance, a weakened deep cell inhibits the upwelling of North Pacific Deep Water and hinders water cycling in the Pacific, whereas a strengthened upper cell intensifies northward oceanic heat transport, potentially affecting the climate of Eastern Asia. Using a high-resolution coupled climate model, we identify a strengthening trend of 0.04 Sv & centerdot;century-1 in the upper cell, equivalent to 3% of its mean transports during 1900-2100. In contrast, the deep cell weakens at a rate of 0.05 Sv & centerdot;century-1, representing a 20% reduction over the same period. The increased sea surface height difference between the northern and southern Luzon Strait-linked to weaker subtropical wind in a warming climate-leads to a stronger upper-layer inflow into the SCS, thereby intensifying the upper cell of the SCSMOC. In contrast, the more rapid freshening of the Pacific Ocean than the SCS diminishes the deep-layer meridional pressure difference in the Luzon Strait, resulting in a reduced deep inflow and a weakened deep cell of the SCSMOC. Our findings highlight the importance of long-term monitoring of the SCSMOC and comprehensive understanding of associated impacts.

The upper-layer circulation in the South China Sea (SCS) exhibits significant intraseasonal oscillation (ISO), influencing the regional ocean environment and climate. However, the evolution of this ISO under global warming and its underlying mechanisms remain poorly understood. Using a high-resolution Community Earth System Model, this study identifies a strengthening trend of 7.8% in the ISO intensity of the western boundary current (WBC) speed during 1901–2100. Further analysis reveals a 24% intensification of oceanic stratification, while basin-scale wind stress and its ISO show weakening trends of 10% and 18%, respectively. Quasi-geostrophic model experiments demonstrate that the ISO enhancement is primarily driven by intensified upper-ocean stratification, with the weakening wind field exerting a dampening effect. This amplified upper-layer circulation ISO is closely linked to increased sea surface temperature (SST) variability, suggesting higher intensity and frequency of marine heatwaves in the SCS. Furthermore, enhanced SST variability may amplify intraseasonal ocean heat release, potentially altering regional climate. This study elucidates the intensification mechanism of upper-ocean ISO in the SCS under global warming and its climatic impacts, providing new insights into the response of tropical marginal sea climate variability to a warming climate.

Ocean wave-current interactions are important physical processes at the sea surface, which can potentially cause extreme sea states under certain conditions. Usually, such interactions are more notable in regions with strong waves and background currents. In this study, focusing on the Kuroshio Extension, we used buoy-measured and altimeter-derived wave data to determine variations in wave properties with the background currents. Statistically, the wave height can be underestimated (overestimated) by approximately 4

Global-scale measurements of air-sea variables and associated boundary layer processes are crucial for determining ocean surface fluxes, understanding atmosphere-ocean interactions, validating remotely sensed data, and enhancing coupled model simulations. Traditional observation platforms like ships and moored buoys face limitations in capturing the spatial-temporal variabilities of air-sea interactions globally. Drifting and autonomous surface vehicles have emerged as promising complements for the air-sea interface observation. We introduce the drifting air-sea interface buoy (DrIB), a low-cost minibuoy designed to measure essential climate and ocean variables at the air-sea interface in a free-drifting way, while ensuring the stability of the buoy's attitude. It is capable of surface seawater and 3-m meteorological observations, including sea surface temperature, air pressure, temperature, humidity, and vector wind speed. By the end of 2022, over 74 DrIBs were tentatively deployed in the regions of the Kuroshio Extension, western Pacific, South China Sea, and Southern Ocean. Comparative data analyses with a moored buoy [Kuroshio Extension Observatory (KEO), an Ocean Climate Station operated by NOAA in the Kuroshio Extension] and ship-borne measurements prove the feasibility of DrIB's observation at the air-sea interface. The DrIB-KEO comparison experiment demonstrates statistical consistency across observation parameters (wind speed, air temperature, relative humidity, air pressure, and sea surface temperature), with correlation coefficients exceeding 0.95. DrIB demonstrates promising potential in delivering global air-sea interface variables and turbulent heat fluxes. Future regional and global deployments of DrIBs will enhance satellite remote sensing data validation and improve the study of meso-/frontal-scale air-sea interactions, advancing ocean-atmosphere coupled model simulations.

This study addresses the local scour problem of monopile foundations in the central Bohai Sea. This study integrates numerical simulations with experimental validation to conduct an in-depth analysis of the tidal current background, sediment transport, sediment sources, and scour characteristics over the past two decades. The analysis of ocean currents and sediment dynamics revealed that the monthly average tidal current speed in the majority of the study region is below 0.6 m·s−1, with annual seabed erosion and accretion changes within 0.02 m, exhibiting minimal variation. The annual erosion and accretion changes in the wind farm areas are less than 0.01 m. The analysis of local scour around monopile foundations indicates that approximately 80% of the scour occurs during the initial phase. A comparative analysis of collar protection effectiveness indicates that the collar can effectively reduce scour depth by 50%, thereby demonstrating significant protective effects. However, the prevailing trend of scouring remains unaltered, indicating that collar protection has inherent limitations in regulating early-stage scouring. The findings of this study provide a theoretical basis for the design and protection of monopile foundations in the central Bohai Sea and offer a valuable reference point for the scour protection of wind turbine foundations in similar regions.

The northern South China Sea has abundant frontal systems near coastal and island regions, which play crucial roles in regional ocean dynamics and ecosystem. While previous studies have established preliminary understanding of their spatial distribution, seasonal variability, and dynamic characteristics, the atmospheric response to these frontal systems remains poorly understood. This study integrates observations from a moored buoy deployed on the continental shelf of the South China Sea with satellite remote sensing data to analyze oceanic and atmospheric variations during frontal passage. The results reveal that the ocean front can not only induce pronounced oceanic changes characterized by significant cooling, saltiness, and surface current acceleration, but also exert substantial influence on the overlying atmosphere, with consistent decreasing trends in air temperature, humidity, and atmospheric pressure, all of which rapidly recovered following frontal retreat. Notably, when the front directly traversed the buoy location, diurnal temperature cycles were markedly suppressed, while turbulent heat flux and downfront wind-stress curl reached peak magnitudes. These findings demonstrate that ocean fronts and associated sea surface temperature gradients can trigger intense air–sea exchange processes at the ocean–atmosphere interface.

The Weather Research and Forecasting (WRF) model is employed to conduct numerical simulations and simulated acquisition of a 30-year (1993–2022) wind field dataset for the Bohai Sea. The simulated WRF wind field is subsequently used to drive the Simulating Waves Nearshore (SWAN) model, producing a corresponding wave field dataset for the same period in the Bohai Sea. Using these datasets, we analyzed the extreme value distributions of wind speed and significant wave height in the study area. The results reveal that both the annual mean wind speed and significant wave height exhibit a ring-like spatial pattern. The highest values are concentrated in the southern Liaodong Bay to the central Bohai Sea region, with a gradual radial decrease toward the periphery. Specifically, values decline from the center outward, from southeast to northwest, and from offshore to nearshore regions. The Gumbel extreme value distribution is applied to estimate 100-year return period extremes, yielding maximum wind speeds of 37 m/s and significant wave heights of 6 m in offshore areas. In nearshore regions, the 100-year return period wind speeds range between 20–25 m/s, while significant wave heights vary from 2 to 3 m. This study provides important scientific basis and decision-making reference for the design of offshore extreme conditions.

Volatile sulfur compounds, such as dimethyl sulfide (DMS), carbonyl sulfide (OCS), and carbon disulfide (CS2), have significant implications for both atmospheric chemistry and climate change. Despite the crucial role of oceans in regulating their atmospheric budgets, our comprehension of their cycles in seawater remains insufficient. To address this gap, a field investigation was conducted in the western North Pacific to clarify the sources, sinks, and biogeochemical controls of these gases in two different marine environments, including relatively eutrophic Kuroshio-Oyashio extension (KOE) and oligotrophic North Pacific subtropical gyre. Our findings revealed higher concentrations of these gases in both seawater and the atmosphere in the KOE compared to the subtropical gyre. In the KOE, nutrient-rich upwelling stimulated rapid DMS biological production, while reduced seawater temperatures hindered the removal of OCS and CS2, leading to their accumulation. Furthermore, we have quantitatively evaluated the relative contribution of each pathway to the source and sink of DMS, OCS, and CS2 within the mixed layer and identified vertical exchange as a potential sink in most cases, transporting substantial amounts of these gases from the mixed layer to deeper waters. This research advances our understanding of sulfur gas source-sink dynamics in seawater, contributing to the assessment of their marine emissions and atmospheric budgets.

Based on a submesoscale-resolving glider observation from April 25 to May 4, 2018, characteristics and underlying dynamics of submesoscale variability at the edge of an anticyclonic eddy shed from Kuroshio in the Northern South China Sea are explored in this study. Three underwater gliders traveled across the frontal zone and implemented ~ 300 dives, covering a horizontal distance of ~ 160 km and a vertical depth of ~ 500 m in 9 days. The character of k −2 slope for spectral potential energy and the strong lateral buoyancy gradient indicate frontogenesis-induced submesoscale motions on the eddy edge. Further analysis focusing on the potential vorticity and balanced Richardson number reveals the development of symmetric instability (SI), which is associated with the strong lateral gradient of buoyancy at the edge of the anticyclonic eddy in the late spring.

Oceanic mesoscale eddies influence air-sea interaction and atmosphere dynamics through ventilating heat and moisture upward. However, whether the sea surface temperature (SST) gradient on the eddy edge could affect the heat and moisture release is still unknown because of the limited observations and coarse-resolution climate models. Using high-resolution atmospheric simulations, this study compares the atmospheric response to the mesoscale (similar to 40 km) and submesoscale (similar to 4 km) SST gradients at the edge of an eddy. Results show that submesoscale SST gradient drives stronger surface heat and moisture fluxes, enhancing the vertical mixing intensity by 2-3 times within and above the marine atmospheric boundary layer. As a result, one local precipitation event is found to be an order of magnitude larger overlying the eddy. Our findings highlight the importance of resolving oceanic submesoscale features for accurately predicting atmosphere dynamics and precipitation over the ocean.

Submesoscale fronts, with horizontal scale of 0.1–10 km, are key components of climate system by driving intense vertical transports of heat, salt and nutrients in the ocean. However, our knowledge on how large the vertical transport driven by one single submesoscale front can reach remains limited due to the lack of comprehensive field observations. Here, based on high-resolution in situ observations in the Kuroshio-Oyashio Extension region, we detect an exceptionally sharp submesoscale front. The oceanic temperature (salinity) changes sharply from 14 °C (34.55 psu) to 2 °C (32.7 psu) within 2 km across the front from south to north. Analysis reveals intense vertical velocities near the front reaching 170 m day−1, along with upward heat transport up to 1.4 × 10−2 °C m s−1 and salinity transport reaching 4 × 10−4 psu m s−1. The observed heat transport is much larger than the values reported in previous observations and is three times as that derived from current eddy-rich climate models, whereas the salinity transport enhances the nutrients concentration with prominent implications for marine ecosystem and fishery production. These observations highlight the vertical transport of submesoscale fronts and call for a proper representation of submesoscale processes in the next generation of climate models.

The ocean issue has attracted the attention of governments all over the world. A comprehensive understanding of the ocean and making accurate predictions are the primary keys to addressing global issues, such as climate change and water circulation. Ocean observation is a primary means of understanding the ocean dynamic process and the energy and material cycle caused by it. It is crucial to strengthen the research and development of ocean observation technology and equipment by building an integrated three-dimensional ocean observation system. Therefore, implementing the "Transparent Ocean" strategy indicates the direction for the marine science and technology innovation of China. The Kuroshio extension sea area is one of the most active areas of ocean and atmospheric dynamic processes. Ocean multiscale dynamic processes and their interactions are the core link to maintaining the ocean energy balance. The energy cascade from the large to the small scales plays a crucial role in maintaining the balance of the ocean energy budget and determining the motion pattern of the ocean system. Therefore, multiscale research on multilayered ocean dynamic processes is of utmost significance for understanding the mechanism of the ocean energy cascade and the law of ocean evolution. However, due to the complex marine dynamic processes in the region, it is difficult for traditional large-scale airsea buoys to work continuously for a long time. Almost all mooring fixed-point observation systems are concentrated in tropical sea areas. The global middle-high-latitude sea area, especially the Kuroshio extension sea area, is still a "desert area" lacking long-term continuous observation. Currently, there is only one set of large-scale observation buoys (Kuroshio Extension Observatory, KEO) in the United States in this region under long-term operation. Against this background, Ocean University of China has been committed to developing a long-term series of integrated observation buoys in this area since 2017. The China Kuroshio Extension Observatory (CKEO) developed a series of buoys featuring a targeted design for the buoy body and a deep-water mooring system. This has enhanced the stability and reliability of buoys in an abominable sea state, thus enabling them to operate stably for a long time in the Kuroshio extension area of the Western Pacific Ocean. The buoy body is made of aluminum magnesium alloy and filled with closedcell foaming material to ensure that the buoy will not sink after being hit. The mooring system adopts a suspension structure that is applied to the navigation mark in the channel. A cantilever structure uses two stress points outside the body to ensure that the buoy is always in a relatively vertical state on the surface of the water. Buoy observation elements include meteorological, hydrology, biochemistry, and other multidisciplinary elements. The profile temperature and salinity observation data were transmitted to the surface buoy body by induction coupling. The lower end of the buoy platform connects the magnetic ring on the water to the data acquisition and processing system in the buoy body through the electric rotating ring. The power supply system adopts a combination of lead-acid batteries and solar panels commonly used in international far-reaching sea buoys, which can ensure the normal continuous operation of the integrated monitoring buoy system for at least one year. The first deployment was conducted in 2019. By 2022, this series of buoys will have been working steadily in the area for three years, obtaining a large quantity of data on hydrological, meteorological, and other environmental parameters. As shown by the analysis of the obtained data and the status of the recovered buoys, the equipment was basically in a normal state when under operation. The observation data were accurate, which has supported the research on scientific issues, such as air-sea energy exchange in the Kuroshio extension area. Thus, it contributed to developing the "Transparent Ocean" Three-dimensional Observation Network.

西北太平洋黑潮延伸体是全球海洋动力过程最复杂、对全球气候变化最敏感和全球海洋渔业产量最大的区域之一,然而,目前对该海区物理、生态及生地化循环等过程的认识仍受限于长期连续海洋观测资料的缺乏.本文回顾了国际上针对黑潮延伸体海区的相关观测情况和取得的主要进展,介绍了近年来我国在该区域观测系统的构建工作及取得的初步成果,包括构建了全球首个西北太平洋黑潮延伸体定点观测系统;发现黑潮延伸体海区海洋涡旋的平流效应对该海区模态水的总潜沉率贡献超过一半,所携带当地的模态水只需要一年半的时间就可到达海盆的西边界;基于潜标首次展示了黑潮延伸体区域3种不同类型次温跃层涡旋流速的直接观测结果,为开展其生成消亡机制及其全球次表层物质能量输运提供了重要的现场观测基础.最后,本文展望了今后观测系统的发展方向,即在跨圈层和多学科交叉方面发展成为我国在西北太平洋重要的深远海综合观测网络.这将为揭示多尺度物理-生物过程耦合、深海能量串级及其气候效应与深海碳循环等领域实现突破提供重要的观测支撑.

波浪能是世界上分布最广泛的可再生能源之一。海洋环境中波浪运动随机复杂且频率极低,这为海洋波浪能的高效收集利用提出挑战。设计了一种混沌平面摆式波浪能收集装置,其中混沌平面摆作为超低频随机波浪俘能机构,配合齿轮增速传递机构与电磁旋转机构实现波浪能收集装置的高功率输出。为更好响应浮标在海洋中的运动激励,对俘能机构进行动力学分析建模与优化。针对装置输出电压无规律且低频交流的特性,设计功率采样跟踪升压存储的电源管理电路。通过实验室测试与实际近海测试,装置能够对复杂波浪产生最大10 V的开路电压,最大输出功率约205 mW。海试中,4小时可将200 mAh锂电池电压由3.12 V充电至3.6 V,能够作为新能源海洋浮标低功耗传感器的可持续电源。

波浪观测是海洋观测的主要内容之一,对海浪的现场观测和深入研究对准确预报海浪具有十分重要的意义.本文设计了一种新型漂流式波浪浮标,采用高精度惯性导航模块作为测量元件,同时高频获取三轴加速度、角加速度、欧拉角、地磁数据,通过内置ARM处理器对测量数据进行波浪参数的采集和解算.浮标具有整体体积小、成本低的特点,既可以漂流观测,也可以定点锚系观测,能够实现对海浪的长期、大范围、高精度观测应用.本文通过该漂流式波浪浮标在2019年西北太平洋航次的观测应用,对西北太平洋黑潮延伸体海区和日本海区域海浪的有效波高、周期等波浪要素的时空变化特征进行了详细分析,取得了良好的测量结果.

本文利用MM5大气模型和HYCOM海洋环流模型,模拟研究了2002年飓风Isidore过境墨西哥湾后上层海洋的响应以及墨西哥湾常态水(Gulf common water,GCW)和湾流(Loop Current,LC)对飓风Isidore的不同响应.飓风Isidore穿过GCW区后,导致海表最大降温接近5℃,混合层深度由30m加深到70m,上层海洋损失热量较多,上层海洋的结构恢复时间较长;但在LC区,由于亚热带持续不断的高温、高速水体输运,该区域水体具有较深的混合层和较大的能量,虽然在飓风过程中损失了较多的热量,但仅造成2℃的海表面降温,上层海洋的结构恢复时间较短;此外,飓风过境后,在上层海洋激发近惯性震荡,在LC区可导致1.0m/s近惯性震荡流,能量可传播至1500m以深,但在GCW区,由于较浅的上混合层、较弱的流速和较强的层化结构,近惯性震荡运动影响深度较浅.

对安装于我国三亚海棠湾的X波段雷达设备及布放在该区域的“波浪骑士”浮标和波高仪进行了海浪比测试验,并且对所获得的现场海浪观测数据进行了分析.通过试验结果表明:X波段雷达观测海浪的方式基本可靠,能够有效捕捉到海浪的变化过程.

本文通过实验室实验的方法,对降雨对海面粗糙度以及风浪和涌浪成长的影响进行了初步的分析;用波面位移数据计算了海浪谱,初步讨论了降雨对波浪成长的影响.分析结果表明:在低风速时,降雨对波浪成长起抑制作用;而在高风速时,降雨对波浪成长起促进作用.其物理机制有待于进一步分析.

在内波以及其他的层结流体的实验中首先需要制备密度层结的流体,传统的双缸法只能制备密度均匀分层的层结流体.本文对传统的制备均匀层结盐水的双缸法进行改进,推导了制备任意密度剖面的层结盐水方法的理论公式以及实用数值计算方法,通过振荡圆柱实验对此方法的可行性进行了验证.