Since 2007, large-scale green tides dominated by Ulva prolifera consecutively bloomed in the Yellow Sea and caused great economic losses. The fouling U. prolifera on the Pyropia yezoensis aquaculture rafts in the Subei Shoal was regarded as the major source of the floating biomass. However, it was still unclear about the seed source of fouling green macroalgae attached on the rafts. In this study, the field surveys and the indoor experiments were conducted to reveal the source of propagules of the fouling green macroalgae on the rafts and to study the anti-fouling material for P. yezoensis aquaculture rafts which could possibly be a feasible strategy to control the green tides in the Yellow Sea. The results showed that (1) micro-propagules of several green macroalgal species, including U. prolifera, U. linza, U. compressa, U. flexuosa, and Blidingia sp. coexisted in the waters and sediments in the Subei Shoal and their proportion remarkably changed over time; (2) the bamboo poles with peeling treatment could significantly reduce the amount of U. prolifera micro-propagules attached. This study confirmed that the micro-propagules distributed in the Subei Shoal area were the precursors of the green tides, and provided a feasible method to control the Yellow Sea large-scale green tides at the beginning.

Global warming has caused Arctic sea ice to rapidly retreat, which is affecting phytoplankton, the primary producers at the base of the food chain, as well as the entire ecosystem. However, few studies with large spatial scales related to the Arctic Basin at high latitude have been conducted. This study aimed to investigate the relationship between changes in phytoplankton community structure and ice conditions. Fifty surface and 41 vertically stratified water samples from the western Arctic Ocean (67.0°–88°26′N, 152°–178°54′W) were collected by the Chinese icebreaker R/V Xuelong from July 20 to August 30, 2010 during China’s fourth Arctic expedition. Using these samples, the species composition, spatial distribution, and regional disparities of phytoplankton during different stages of ice melt were assessed. A total of 157 phytoplankton taxa (>5 μm) belonging to 69 genera were identified in the study area. The most abundant species were Navicula pelagica and Thalassiosira nordenskioeldii, accounting for 31.23% and 14.12% of the total phytoplankton abundance, respectively. The average abundance during the departure trip and the return trip were 797.07×10² cells/L and 84.94×10² cells/L, respectively. The highest abundance was observed at Sta. R09 in the north of Herald Shoal, where Navicula pelagica was the dominant species accounting for 59.42% of the abundance. The vertical distribution of phytoplankton abundance displayed regional differences, and the maximum abundances were confined to the lower layers of the euphotic zone near the layers of the halocline, thermocline, and nutricline. The species abundance of phytoplankton decreased from the low-latitude shelf to the high-latitude basin on both the departure and return trips. The phytoplankton community structure in the shallow continental shelf changed markedly during different stages of ice melt, and there was shift in dominant species from centric to pennate diatoms. Results of canonical correspondence analysis (CCA) showed that there were two distinct communities of phytoplankton in the western Arctic Ocean, and water temperature, ice coverage and silicate concentration were the most important environmental factors affecting phytoplankton distribution in the surveyed sea. These findings will help predict the responses of phytoplankton to the rapid melting of Arctic sea ice.

The unique survey in December 1998 mapped the entire western boundary area of the South China Sea (SCS), which reveals the three-dimensional structure and huge volume transport of the swift and narrow winter western boundary current of the SCS (SCSwwbc) in full scale. The current is found to flow all the way from the shelf edge off Hong Kong to the Sunda Shelf with a width around 100 km and a vertical scale of about 400 m. It appears to be the strongest off the Indo-China Peninsula, where its volume transport reached over 20×10⁶ m³/s. The current is weaker upstream in the northern SCS to the west of Hong Kong. A Kuroshio loop or detached eddy intruded through the Luzon Strait is observed farther east where the SCSwwbc no more exists. The results suggest that during the survey the SCSwwbc was fed primarily by the interior recirculation of the SCS rather than by the “branching” of the Kuroshio from the Luzon Strait as indicated by surface drifters, which is likely a near-surface phenomenon and only contributes a minor part to the total transport of the SCSwwbc. Several topics related to the SCSwwbc are also discussed.

In order to evaluate the assimilation results from a global high resolution ocean model, the buoy observations from tropical atmosphere ocean (TAO) during August 2014 to July 2015 are employed. The horizontal resolution of wave-tide-circulation coupled ocean model developed by The First Institute of Oceanography (FIOCOM model) is 0.1°×0.1°, and ensemble adjustment Kalman filter is used to assimilate the sea surface temperature (SST), sea level anomaly (SLA) and Argo temperature/salinity profiles. The simulation results with and without data assimilation are examined. First, the overall statistic errors of model results are analyzed. The scatter diagrams of model simulations versus observations and corresponding error probability density distribution show that the errors of all the observed variables, including the temperature, isotherm depth of 20°C (D20), salinity and two horizontal component of velocity are reduced to some extent with a maximum improvement of 54% after assimilation. Second, time-averaged variables are used to investigate the horizontal and vertical structures of the model results. Owing to the data assimilation, the biases of the time-averaged distribution are reduced more than 70% for the temperature and D20 especially in the eastern Pacific. The obvious improvement of D20 which represents the upper mixed layer depth indicates that the structure of the temperature after the data assimilation becomes more close to the reality and the vertical structure of the upper ocean becomes more reasonable. At last, the physical processes of time series are compared with observations. The time evolution processes of all variables after the data assimilation are more consistent with the observations. The temperature bias and RMSE of D20 are reduced by 76% and 56% respectively with the data assimilation. More events during this period are also reproduced after the data assimilation. Under the condition of strong 2014/2016 El Niño, the Equatorial Undercurrent (EUC) from the TAO is gradually increased during August to November in 2014, and followed by a decreasing process. Since the improvement of the structure in the upper ocean, these events of the EUC can be clearly found in the assimilation results. In conclusion, the data assimilation in this global high resolution model has successfully reduced the model biases and improved the structures of the upper ocean, and the physical processes in reality can be well produced.

The rip currents induced by waves off arc-shaped coastlines are seriously harmful to humans, but understanding of their characteristics is lacking. In this study, the FUNWAVE model was used to calculate the wave-induced currents in the Haller experiment and the ideal arc-shaped coast similar to Sanya Dadonghai, Hainan Province, China. The results showed that the FUNWAVE model has considerable ability to simulate the rip currents, and it was used to further simulate rip currents off arc-shaped coastlines to investigate their characteristics. The rip currents were found to be stronger as the curvature of arc-shaped coastline increased. Coastal beach slope exerts a significant influence on rip currents; in particular, an overly steep or overly mild slope is not conducive to creating rip currents. Furthermore, the rip currents were found to become weaker as the size of arc-shaped coast decreased. When the height and period of waves increase, the strength of rip currents also increases, and, in some cases, wave heights of 0.4 m may produce dangerous rip currents.

This study presents an analysis of the CTD data and the turbulent microstructure data collected in 2014, the turbulent mixing environment above the Atlantic Water (AW) around the Chukchi Borderland region is studied. Surface wind becomes more efficient in driving the upper ocean movement along with the rapid decline of sea ice, thus results in a more restless interior of the Arctic Ocean. The turbulent dissipation rate is in the range of 4.60×10^–10–3.31×10^–9 W/kg with a mean value of 1.33×10^–9 W/kg, while the diapycnal diffusivity is in the range of 1.45×10^–6–1.46×10^–5 m²/s with a mean value of 4.84×10^–6 m²/s in 200–300 m (above the AW). After investigating on the traditional factors (i.e., wind, topography and tides) that may contribute to the turbulent dissipation rate, the results show that the tidal kinetic energy plays a dominating role in the vertical mixing above the AW. Besides, the swing of the Beaufort Gyre (BG) has an impact on the vertical shear of the geostrophic current and may contribute to the regional difference of turbulent mixing. The parameterized method for the double-diffusive convection flux above the AW is validated by the direct turbulent microstructure results.

The Atlantic inflow in the Fram Strait (78°50′N) has synoptic scale variability based on an array of moorings over the period of 1998–2010. The synoptic scale variability of Atlantic inflow, whose significant cycle is 3–16 d, occurs mainly in winter and spring (from January to April) and is related with polar lows in the Barents Sea. On the synoptic scale, the enhancement (weakening) of Atlantic inflow in the Fram Strait is accompanied by less (more) polar lows in the Barents Sea. Wind stress curl induced by polar lows in the Barents Sea causes Ekman-transport, leads to decrease of sea surface height in the Barents Sea, due to geostrophic adjustment, further induces a cyclonic circulation anomaly around the Barents Sea, and causes the weakening of the Atlantic inflow in the Fram Strait. Our results highlight the importance of polar lows in forcing the Atlantic inflow in the Fram Strait and can help us to further understand the effect of Atlantic warm water on the change of the Arctic Ocean.

The present climate simulations of the mixed layer depth (MLD) and the subduction rate in the subtropical Northeast Pacific are investigated based on nine of the CMIP5 models. Compared with the observation data, spatial patterns of the MLD and the subduction rate are well simulated in these models. The spatial pattern of the MLD is nonuniform, with a local maximum MLD (>140 m) region centered at (28°N, 135°W) in late winter. The nonuniform MLD pattern causes a strong MLD front on the south of the MLD maximum region, controls the lateral induction rate pattern, and then decides the nonuniform distribution of the subduction rate. Due to the inter-regional difference of the MLD, we divide this area into two regions. The relatively uniform Ekman pumping has little effect on the nonuniform subduction spatial pattern, though it is nearly equal to the lateral induction in values. In the south region, the northward warm Ekman advection (–1.75×10^–7 K/s) controls the ocean horizontal temperature advection (–0.85×10^–7 K/s), and prevents the deepening of the MLD. In the ensemble mean, the contribution of the ocean advection to the MLD is about –29.0 m/month, offsetting the sea surface net heat flux contribution (33.9 m/month). While in the north region, the southward cold advection deepens the MLD (21.4 m/month) as similar as the heat flux (30.4 m/month). In conclusion, the nonuniform MLD pattern is dominated by the nonuniform ocean horizontal temperature advection. This new finding indicates that the upper ocean current play an important role in the variability of the winter MLD and the subduction rate.

In this study, the possible effects of subduction rate on global warming hiatus were investigated using Simple Ocean Data Assimilation (SODA) data. This study first analyzed the characteristics of the temporal and spatial distribution of global subduction rate, which revealed that the North Atlantic meridional overturning circulation region and the Antarctic Circumpolar Current region are the two main sea areas with great subduction variations. On this basis, four key areas were selected to explore the relationship between the local subduction rate and the global mean sea surface temperature. In addition, the reason for the variations in subduction rate was preliminarily explored. The results show good correspondence of the subduction of the key areas in the North Atlantic meridional overturning the circulation region and the Antarctic Circumpolar Current region to the global warming hiatus, with the former leading by about 10 years. The subduction process may be a physical mechanism by which the North Atlantic overturning circulation and the Antarctic Circumpolar Current act on the stagnation of global warming. Advection effect plays an important role in the variations in subduction in the key regions. In the Antarctic Circumpolar Current region, the magnitude of sea surface wind stress is closely related to the local changes in subduction.

The condensate and bunker oil leaked from the Sanchi collision would cause a persistent impact on marine ecosystems in the surrounding areas. The long-term prediction for the distribution of the oil-polluted water and the information for the most affected regions would provide valuable information for the oceanic environment protection and pollution assessment. Based on the operational forecast system developed by the First Institute of Oceanography, State Oceanic Administration, we precisely predicted the drifting path of the oil tanker Sanchi after its collision. Trajectories of virtual oil particles show that the oil leaked from the Sanchi after it sank is mainly transported to the northeastern part of the sink location, and quickly goes to the open ocean along with the Kuroshio. Risk probability analysis based on the outcomes from the operational forecast system for years 2009 to 2017 shows that the most affected area is at the northeast of the sink location.