The Lake Tian E Zhou (TEZ, an oxbow lake) was formed during the rerouting of the Changjiang River in 1972, with strong influences from the main river channel and flood events. Herein, a sediment core was collected from the Lake TEZ for the measurements of carbon isotopes and biomarkers, including stable carbon isotopes (δ¹³C), radiocarbon composition (∆¹⁴C), and lignin phenols, as well as lead-210 to reconstruct recent heavy flood events over the past 70 years. At the 24–26 cm interval, the sediment contained the highest OC%, TN%, and lignin phenols content, as well as significantly depleted ¹³C but enriched ¹⁴C, corresponding to the extreme flood event in 1998. In addition, statistics from t-test showed that lignin phenols normalized to OC (Λ8), the concentration of 3, 5-dihydroxy benzoic acid (3, 5-BD), and the ratio of p-hydroxy benzophenone to total hydroxyl phenols (PHB/HP) were all significantly different between the layers containing flood deposits and the layers deposited under normal non-flood conditions (p<0.05). These results indicate that the later three parameters are highly related to flood events and can be used as compelling proxies, along with sediment chronology, for hydrological changes and storm/flood events in the river basin and coastal marine environments.

Ciliates are important components in planktonic food webs, but our understanding of their community structures in different oceanic water masses is limited. We report pelagic ciliate community characteristics in three seas: the tropical West Pacific, the Bering Sea and the Arctic Ocean. Planktonic ciliate abundance had “bimodal-peak”, “surface-peak” and “DCM (deep chlorophyll a maximum layer)-peak” vertical distribution patterns in the tropical West Pacific, the Bering Sea and the Arctic Ocean, respectively. The abundance proportion of tintinnid to total ciliate in the Bering Sea (42.6%) was higher than both the tropical West Pacific (7.8%) and the Arctic Ocean (2.0%). The abundance proportion of small aloricate ciliates (10–20 μm size-fraction) in the tropical West Pacific was highest in these three seas. The Arctic Ocean had higher abundance proportion of tintinnids in larger LOD (lorica oral diameter) size-class. Proportion of redundant species increased from the Arctic Ocean to the tropical West Pacific. Our result provided useful data to further understand ecology roles of planktonic ciliates in different marine habitats.

Food differentiation among coexistent species in the field is important strategy for copepods to acquire materials and maintain population stabilization. In situ diet analysis of co-occurring six copepod species in coral waters of the Sanya Bay was conducted using a PCR protocol based on 18S ribosomal gene. Various prey organisms were uncovered, including dinoflagellate, diatom, green algae and plant, protozoa and metazoan. All these spatially co-existing six species showed different dietary diversity, with the food niche breadth (B) ranging from 1.00 (Temora turbinate in morning) to 10.68 (Calanopia elliptica in night). While food overlap between all these copepods were low, with the average value of the diet niche overlap index being approximately 0.09. Even temporally co-existing species sampled from the same time point fed on different groups of prey items with the food overlap index of 0.04 to 0.07 in midday and night but 0 in morning. As the most important dominant copepod in the Sanya Bay, Subeucalanus subcrassus seems to be capable to regulate its feeding, by exhibiting a rhythm of herbivorous feeding in midday and carnivorous feeding in morning and night, to better coordinate with other competitors for utilization of food resources. For most copepods, none of the prey items belonged to the dominant phytoplankton in the ambient water, indicating that copepod can better their survival by widening the choice of potential food resources in food limited environment. The dietary separation observed here might be important strategy for copepod to maintain population stabilization and thriving in the Sanya coastal waters.

China (herein referred as China’s mainland, and excluding Hong Kong, Macau and Taiwan) ranks as the world’s leading fishing nation, with approximately 11.1 million tons of domestic marine catch acquired in 2017. Marine fisheries resources in China are mainly exploited by its 11 coastal provinces and municipalities, and the development of fishing industry varies among them. However, few studies have examined the exploitation history of the 11 coastal provinces and municipalities. In this paper, we systematically quantified the exploitation history of marine fishery resources in China and then measured the vulnerability of the 11 coastal provinces and municipalities of China to a reduction in marine catches. Our analysis suggested that Chinese marine fisheries experienced rapid growth from the mid-1980s to the end of the 20th century, and this rapid increase in marine catches were mainly promoted by increased fishing effort. The total primary production required level amounted to approximately 80% of the average primary productivity in 2017, and Zhejiang, Fujian, Shandong, Hainan and Guangdong provinces were the main fishing provinces in China. By assessing three dimensions of vulnerability (exposure, sensitivity and adaptive capacity) to the impacts of a reduction in marine catches in the 11 coastal provinces and municipalities, we found that Hainan, Guangxi, Zhejiang and Fujian provinces had high or very high vulnerability, while the municipalities of Shanghai and Tianjin had low vulnerability. Identifying suitable adaptation policies and management plans based on the differences in vulnerability among coastal provinces is important in sustainable fisheries management.

An ensemble-based assimilation method is proposed for correcting the subsurface temperature field when nudging the sea surface temperature (SST) observations into the Max Planck Institute (MPI) climate model, ECHAM5/MPI-OM. This method can project SST directly to subsurface according to model ensemble-based correlations between SST and subsurface temperature. Results from a 50 year (1960–2009) assimilation experiment show the method can improve the subsurface temperature field up to 300 m compared to the quality-controlled subsurface ocean temperature objective analyses (EN4), through reducing the biases of the thermal states, improving the thermocline structure, and reducing the root mean square (RMS) errors. Moreover, as most of the improvements concentrate over the upper 100 m, the ocean heat content in the upper 100 m (OHT_100 m) is further adopted as a property to validate the performance of the ensemble-based correction method. The results show that RMS errors of the global OHT_100 m convergent to one value after several times iteration, indicating this method can represent the relationship between SST and subsurface temperature fields well, and then improve the accuracy of the simulation in the subsurface temperature of the climate model.

The ocean and land color instrument (OLCI) and synthetic aperture radar altimeter (SRAL) installed aboard the Sentinel-3 satellite have been in orbit for operational uses. In this study, data collected from Sentinel-3 are used to investigate internal waves in the South China Sea. An internal wave is detected using an OLCI image with a resolution of 300 m, and an analysis was performed with a quasi-synchronous moderate-resolution imaging spectroradiometer (MODIS) image. The opposite characteristics of OLCI and MODIS images of the same internal wave are explained by the critical angle in brightness reversals. The unique observational geometry of the OLCI image and its influence on observations of internal waves are discussed. The distribution of σ₀ and sea surface height anomalies (SSHAs) induced by internal waves are studied using SRAL records. The σ₀ records of SRAL occasionally show less sensitivity to the modulation of internal waves, which may be attributed to the observational geometry, while SSHAs show obvious variations. The synchronous pairing of OLCI images and SRAL records are analyzed to extract the three-dimensional sea surface signatures induced by internal waves. The analysis demonstrates that the profile of SSHAs in the surface shows an opposite phase to the profiles of internal waves in the ocean. The opposite phase relationship, observed in the remote sensing view, is also confirmed with a laboratory experiment.

The influences of tropical cyclone paths and shelf bathymetry on the inducement of extreme sea levels in a regional bay are investigated. A finite volume coastal ocean model (FVCOM) has been configured for the Gulf of Thailand-Sunda Shelf. A parametric wind model is used to drive the FVCOM. The contributions of the tropical cyclone characteristics are determined through a scenario-based study. Validation based on a historical extreme sea level event shows that the model can resolve the oscillation mechanism well. The intensification of severe storm surges in the region highly depends on four factors including phase propagation of the storm surge wave determined by the landfall position, funnel effect caused by locality of the coastline, and shelf bathymetry determined by the state of mean sea level and coastline crossing angle of the storm path. The coexistence of these factors can cause particular regions e.g. the Surat Thani Bay, inner Gulf of Thailand and Ca Mau Peninsular to experience a larger surge magnitude. These areas are found to be highly related to monsoon troughs that develop during the onset and early northeastern monsoon season (October–November).

A coupled ocean-ice-wave model is used to study ice-edge jet and eddy genesis during surface gravity wave dissipation in a frazil-pancake ice zone. With observational data from the Beaufort Sea, possible wave dissipation processes are evaluated using sensitivity experiments. As wave energy dissipated, energy was transferred into ice floe through radiation stress. Later, energy was in turn transferred into current through ocean-ice interfacial stress. Since most of the wave energy is dissipated at the ice edge, ice-edge jets, which contained strong horizontal shear, appeared both in the ice zone and the ocean. Meanwhile, the wave propagation direction determines the velocity partition in the along-ice-edge and cross-ice-edge directions, which in turn determines the strength of the along-ice-edge jet and cross-ice-edge velocity. The momentum applied in the along-ice-edge (cross-ice-edge) direction increased (decreased) with larger incident angle, which is favorable condition for producing stronger mesoscale eddies, vice versa. The dissipation rate increases (decreases) with larger (smaller) wavenumber, which enhances (reduces) the jet strength and the strength of the mesoscale eddy. The strong along-ice-edge jet may extend to a deep layer (> 200 m). If the water depth is too shallow (e.g., 80 m), the jet may be largely dampened by bottom drag, and no visible mesoscale eddies are found. The results suggest that the bathymetry and incident wavenumber (magnitude and propagation direction) are important for wave-driven current and mesoscale eddy genesis.

Using AVISO satellite altimeter observations during 1993–2015 and a manual eddy detection method, a total of 276 anticyclonic rings and 242 cyclonic rings shed from the Kuroshio Extension (KE) were identified, and their three-dimensional (3D) anomaly structures were further reconstructd based on the Argo float data and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) cruise and buoy data through an interpolation method. It is found that the cyclonic (anticyclonic) rings presented consistent negative (positive) anomalies of potential temperature; meanwhile the relevant maximum anomaly center became increasingly shallow for the cyclonic rings whereas it went deeper for the anticyclonic rings as the potential temperature anomaly decreased from the west to the east. The above deepening or shoaling trend is associated with the zonal change of the depth of the main thermocline. Moreover, the composite cold ring between 140° and 150°E was found to exhibit a double-core vertical structure due to the existence of mode water with low potential vorticity. Specifically, a relatively large negative (positive) salinity anomaly and a small positive (negative) one appeared for the composite cyclonic (anticyclonic) ring at the depth above and below 600 m, respectively. The underlying driving force for the temperature and salinity anomaly of the composite rings was also attempted, which varies depending on the intensity of the background current and the temperature and salinity fields in different areas of the KE region, and the rings’ influences on the temperature and salinity could reach deeper than 1 000 m on average.

The continental slope in the northern South China Sea (SCS) is rich in mesoscale eddies which play an important role in transport and retention of nutrients and biota. In this study, we investigate the statistical properties of eddy distributions and propagation in a period of 24 years between 1993 and 2016 by using the altimeter data. A total of 147 eddies are found in the continental slope region (CSR), including 70 cyclonic eddies (CEs) and 77 anticyclonic eddies (ACEs). For those eddies that appear in the CSR, the surrounding areas of Dongsha Islands (DS) and southwest of Taiwan (SWT) are considered as the primary sources, where eddies generated contribute more than 60% of the total. According to the spatial distribution of eddy relative vorticity, eddies are weakening as propagating westward. Although both CEs and ACEs roughly propagate along the slope isobaths, there are discrepancies between CEs and ACEs. The ACEs move slightly faster in the zonal direction, while the CEs tend to cross the isobaths with large bottom depth change. The ACEs generally move further into the basin areas after leaving the CSR while CEs remain around the CSR. The eddy propagation on the continental slope is likely to be associated with mean flow at a certain degree because the eddy trajectories have notable seasonal signals that are consistent with the seasonal cycle of geostrophic current. The results indicate that the eddy translation speed is statistically consistent with geostrophic velocity in both magnitude and direction.