The Zhujiang River Mouth Basin is a petroleum-bearing basin with a high degree of exploration in the northern continental margin of the South China Sea, the analysis of fault characteristics is crucial to its basin evolution model and hydrocarbon accumulation mechanism. According to the high-resolution seismic data and drilling data, the fine seismic geological interpretation of the Kaiping Sag in the southwest of the basin is carried out. Based on the fault grade and scale, the fault structure type is divided into the first-level basin-controlled fault, the second-level sag-controlled fault and the third-level control fault based on the level and scale of faults belt fracture and four-level control ring fracture, identify “Y” shaped faults, stepped faults, and heart-shaped faults combination styles on the seismic section, identify three plane combinations of parallel, goose, and oblique based on the fault plane distribution Types of quantitative statistics of the fault strike characteristics show that under the action of the right-handed stress field, from the Eocene to the Early Miocene, the strike direction continued to rotate clockwise in the direction of NE→EW→NW, and the fracture activity gradually weakened. It is also believed that due to the impact of the Indian-Eurasian plate collision, the subduction and retreat of the Pacific plate and the continuous southward movement of the ancient South China Sea, the Zhujiang River Mouth Basin formes a typical extensional tensile stress field environment. It contributes to the development of three groups of faults in the near NE direction, the EW direction and the near-NW direction during the Eocene-Oligocene period. It provides an explanation and supplement to the geological structural characteristics of Kaiping Sag, and provides a reference for the development characteristics and genetic mechanism of the ocean-continent transition zone on the northern margin of the South China Sea.

Based on the analysis of the rare earth element (REE) geochemical characteristics and clay mineral assemblages of Core TS6 sediment samples in the southern area of Southwest Taiwan Basin, South China Sea, the provenance and characteristics of its changes, material transport mechanism of sediments in the study area over the last 19 ka (the last deglaciation) are discussed. The comprehensive analysis of provenance shows that the rivers in Taiwan are the main provenance of sediments in the study area. The rivers in the west of Taiwan contribute more than the rivers in the east, and the Zhujiang River also transports part of sediments to the study area. Due to the large differences on the types and contents of the main clay minerals in different provenance areas, it is judged that the illite and chlorite of the clay minerals in the study area are mainly provided by the rivers in Taiwan; the kaolinite is mainly provided by the Zhujiang River and the less content of montmorillonite is provided by Luzon Island in the southeast. Since the last deglacial period, the input of terrigenous materials in the study area has been gradually reduced under the control of sea level changes. The provenance changes reflected by the combination of clay minerals are mainly controlled by changes in climate and ocean currents, and the influence of multiple factors may be superimposed.

The radial sand ridges is a typical sedimentary accumulation body distributed off the coast of Jiangsu Province. Under the influence of the sediment supply of the Changjiang River and the Huanghe River as well as the coastal tidal current, the typical silty-muddy tidal flats are developed, and the sediment elements can record the important information of the environmental changes of the tidal flats. Three short core samples were collected in the tidal flat of radial sand ridges to establish a reliable chronological framework and geochemical element testing, and 14 elements with high X-ray fluorescence (XRF) core scanner analysis signal strength were selected for clustering and correlation method to extract environmental information. The sedimentary environment changes of the northern Jiangsu radial sand ridges under the influence of human activities and coastal environment changes in the past 100 years were studied. The results indicate that the contents of Si, Ca and Fe in the core sediments of typical tidal flat profile in this area are relatively high, and the contents of Si, Ca and Fe increasing from north to south, while the contents of Mn, Ba, Cu and Zn are low, and the little changes in contents at all profiles changes. In terms of vertical change, Si, Ca and Fe have the same vertical change trend, while Ni, Zn and S have the opposite change trend with Si, Ca and Fe in different sediment cores. Correlation and clustering analysis show that Si, Ca and Fe have high correlation, that is, they have similar geochemical behavior and consistent material source. In addition, it is negatively correlated with elements Ni, Cu and Zn, suggesting that these elements have different geochemical behaviors with the former. The sedimentary environment changes of the tidal flat are obvious and show different patterns in different regions in the northern Jiangsu radial sand ridges, and the material source, hydrodynamic environment and human activities are the main reasons leading to the change of the sedimentary environment.

The submarine topographic features and distribution types of the Xuande atoll in the Xisha Islands have important indications for the influence of regional geological structure, sea level rise and fall, and ocean hydrodynamics. In order to study the submarine topography and geomorphology of the Xuande atoll, we detailed survey in the Xuande atoll of the Xisha Islands, including side scan sonar, single-beam sounding, and surface sediment sampling. The results show that: (1) Xuande atoll is a type of incomplete atoll, with lagoon deposits in the middle, and four water channels with a water depth of about 60 m had been divided, namely, the gate of the Xishazhou at the northwest of the atoll, the “Red Grass Gate” of the Nanshazhou-Yongxing, the gap on the west side of the atoll, and the gap on the south side of the atoll; (2) according to the geomorphic features, the underwater geomorphic types of the Xuande atoll are divided into 3 grades and 11 types of grades classification systems. The dynamic geomorphology units such as sand waves and grooves in the study area show that the submarine features in the shallow water area of Xuande atoll are controlled by prevailing monsoons and wave sites. The tidal channel water body formed by the deep water entrance is the main factor shaping the dynamic geomorphology of the Xuande atoll lagoon area. There are six levels of underwater terraces on the seaward slope in the southeastern part of the study area. By comparing the characteristics of the coral reef terraces in the South China Sea, the genesis of the seaward slope terraces on the Xuande atoll is likely to be a combination of global sea level changes and crustal subsidence.

DNA barcoding technology is a tool for rapid and accurate species identification using short orthologous DNA sequence. In this study, both traditional morphology and DNA barcoding technology was used to accurately identify ichthyoplankton species in the Changjiang River Estuary and its adjacent waters. Morphological description was carried out at the same time. The results showed that in spring and summer of 2016 and summer of 2017, 55 species of ichthyoplankton were obtained, belonging to 9 orders and 19 families. Among them, there were 35 species of Perciformes at most. The seasonal variation of ichthyoplankton in fish group was not obvious, while there was significant seasonal variation in species. Only Coilia mystus, Engraulis japonius and Larimichthys polyactis appeared both in spring and summer. It was the first time to describe the morphological characteristics of Harpadon nehereus larva and juvenile. In addition, the quantifiable characters, fin development and melanin distribution of larvae and juvenile of Harpadon nehereus, Chelon affinis, Eleutheronema tetradactylum, Sillago japonica and Paraplagusia japonica, were described and drew. The research could provide a scientific basis for the study of fish nursery in estuaries, and also provide a new way for the accumulation of taxonomic data in the early stage of fish development.

Along with the global warming, the sea ice in the Arctic decreased rapidly, however the sea ice in the Antarctic has experienced a weak expansion. While many researchers are studying the mechanisms for this paradox in the Antarctic, the sea ice extent (SIE) began a rapid decline in 2016 and reached a record low in austral spring 2016. A rapid decrease of SIE anomaly occurred in December, with a 20.5% (2.13$ \times $10⁶ km²) reduction compared with the long-term (1981−2010) mean (10.41$ \times $10⁶ km²). It attracted a lot of attentions and scientists have investigated the causes of its occurrence from various aspects, such as the atmosphere circulations, the thermal state of the ocean, the polynya and so on. Their main results are summarized in this review. On the atmospheric aspect, the general circulation signals include a zonal height anomalies chain with wave number three during September and October, a Southern Annular Mode anomaly during November and December, and intensified cyclonic activity. The atmospheric zonal wave number three is modulated by the sea surface temperature anomalies in the tropical Pacific and Indian Ocean, and the Southern Annular Mode anomaly is mainly a result of downward weakening stratospheric polar vortex. On the ocean aspect, the upper ocean temperature is warmer than normal, and there is a large polynya in the Weddell Sea, which has the greatest area in the period of 1976−2016. However, it is difficult to identify the relative contributions of the external forcings of the climate system, the internal variability of the climate system, or their collaborative roles. We hope the summary can be useful to improve the understanding of the changes of Antarctic sea ice and its origins.

Antarctic sea ice plays an important role in the global climate system. In contrast to the rapid decrease in Arctic sea ice extent, Antarctic sea ice extent exhibits a gradually increasing trend before 2014, followed by an abrupt decline in the last four decades. A single large-scale atmospheric circulation cannot fully explain the long-term trend of Antarctic sea ice, and the coupling influence of ocean-atmosphere interactions has not been sufficiently investigated. Limited by the capabilities of remote sensing and numerical simulation, the Antarctic sea ice thickness and volume variations in the context of global change cannot be quantified precisely with currently available sea ice thickness and volume data. Moreover, the climate effects of Antarctic sea ice change require further investigation. Hence it is strongly urgent to develop a long-term and reliable Antarctic sea ice thickness data set to quantify the Antarctic sea ice volume change. Meanwhile, the influences of multi-climate modes and ocean-atmosphere coupling system on the Antarctic sea ice changes should be considered comprehensively.

The key regions for formation of the Antarctic Bottom Water occupied in the Indian sector of the Southern Ocean. The salinity change of the region has a profound influence on the global climate change. EN4 reanalysis-gridded data, measured seal data, WOD18 data combined with atmospheric reanalysis and sea ice concentration data were all used to explore the sea surface salinity changes in the Indian sector of the Southern Ocean and the response to large-scale circulation anomaly. The observation and reanalysis data both illustrated a significant positive surface salinity anomaly occurred in the Antarctic coast since 2008, especially in the Indian sector. The surface positive salinity anomaly was mainly centered in the Darnley Polynya and the north of Shackleton Ice Shelf. The high salinity shelf water expanded northward from the Antarctic coast and deepened. Meanwhile, the upwelling of Circumpolar Deep Water became increasingly distinct. Our study showed that this positive salinity anomaly was connected with the Antarctic Oscillation (AAO) and the Indian Ocean Dipole (IOD). During the positive AAO and IOD phases, the westerly wind enhanced significantly in the Indian sector and promoted the formation of sea ice, which increased surface salt flux. The significant negative wind curl and low pressure anomaly resulted in the upwelling of salty Circumpolar Deep Water and maintained the positive salinity anomaly. Additionally, increased locally zonal wind shear and enhanced evaporation were important factors as well.

The PHC, ECCO2, SODA, GECCO3 and CMIP6 data were used to analyze the horizontal distribution characteristics, seasonal variation and long-term trend of the Arctic Ocean heat content, and analyze the simulation ability of the CMIP6 models in this paper. The results show that the heat content of the Arctic Ocean shows obvious seasonal change, with the lowest in April and the highest in September. Under historical circumstances (1850−2014), compared with the observation and reanalysis data, the heat content of the upper 500 m of the CMIP6 models ensemble average (MME) is warmer in the Greenland Sea, colder in the Norwegian sea, Barents Sea and Eurasian Basin, while the whole water column heat content of MME is warmer in almost all regions of the Arctic Ocean, with the largest deviation in the Greenland Sea. CMIP6 models have a large deviation in the simulation of Arctic Ocean temperature profile, and the average temperature of MME is higher than the observation and reanalysis data at the depth of more than 1 000 m. In the future case (2015−2100), the simulation of ocean heat content of MME shows obvious Arctic Ocean warming, but most of the Chinese models show no obvious warming situation. BCC-CSM2-MR and BCC-ESM1 are poor in simulating the annual mean heat content of the Arctic Ocean, CIESM is poor in simulating the seasonal and interdecadal variations of ocean heat content, while FIO-ESM-2-0 is good in simulating the annual heat content of the upper 500 m, the seasonal and interdecadal variations of heat content of the Arctic Ocean.

The GPS radiosonde data obtained during the 6th to 9th Chinese National Arctic Research Expedition was used to analyze the spatial and temporal variation characteristics of boundary layer temperature inversions over the seasonal ice zone in Arctic. The results show that: (1) There were strong interannual and spatial changes in the temperature inversions. There were more strong inversions over the pack ice zone at high latitude. And the thickness of inversions and the temperature change through the inversions had a significant logarithmic relationship. (2) The main factors controlling inversion properties were various in different years. The differences in sea ice cover leaded to different characteristics of inversions. Surface melt, radiative cooling, multi-layer cloud and warm-air advection provided different degrees of contribution to inversions in different years. (3) There were different reasons over the open water and sea ice zone. Both surface melt and warm-air advection played a very important role in the formation of inversions in sea ice zone. However, radiative cooling was one of the main factors in the generation of inversions over the open water.