Unmanned aerial vehicle (UAV) remote sensing has distinct advantages of flexible use, no cloud interference, and high spatial-temporal resolution. Aim to explore UAV’s utilization potential in marine disaster monitoring, research ship was used as the UAV landing pad, and for the first time, based on the bi-temporal orthophotos acquired by the ship-borne UAV, the drift velocity of green-tide in the Yellow Sea was estimated. In addition, the velocity result extracted from satellite images was compared, and the influences of wind and tidal currents on green-tide drift were analyzed. The results show that: (1) the red-green-blue floating algae index (RGB-FAI) can extract green-tide patches from UAV-based RGB orthophotos with a high-accuracy (kappa coefficient=0.95); (2) the green-tidal speed of three sites estimated by UAV remote sensing are 0.26−0.44 m/s, and the drift direction changed significantly throughout the day; (3) the short-term drift of green-tide is forced by the wind and tidal current. The drift direction of the green-tide is basically consistent with the tidal current of M₂, at 1°−62° to the right of wind direction. The ability to estimate green-tidal velocity accurately from the ship-borne UAV images is expected to provide technical support for the precise prediction, warning and control of green-tide disaster.

The distribution and mixing behavior of chromophoric dissolved organic matter (CDOM) in the Changjiang River Estuary and adjacent areas were analyzed in March, July and October of 2019. Through discussing the salinity, absorption spectral slope S_275-295, absorption coefficient a_CDOM(355) and Chl a, it was shown that the terrestrial input and a_CDOM(355) had the highest value in July; a_CDOM(355) was affected by terrestrial input and phytoplankton production activities in March, and the value in March was higher than that in October in the Changjiang River Estuary low salinity area. In addition, in high-salt offshore regions, a_CDOM(355) was similar in March and July, and both were lower than that in October, these distribution of CDOM was mainly influenced by phytoplankton production activities. Four fluorescent components of CDOM were identified by EEMs-PARAFAC technique: one protein-like component C1 (280/330 nm) and three humic-like components C2 (300/350 nm), C3 (260/465 nm) and C4 (320/410 nm) respectively. Four fluorescent components declined from the inside to the outside of the Changjiang River Estuary in March, July and October. Affected by terrestrial input and phytoplankton production activities, the seasonal variation of the average fluorescence intensity from large to small was July, October and March. The fluorescence components of CDOM deviated from the theoretical dilution line in these three seasons. It showed that CDOM source (terrestrial input, sediment resuspension and on-site biological activities) and sink (adsorption of particulate matter, photodegradation and bacterial degradation) were complex and variable, revealing the non-conservative mixed behavior of CDOM in the Changjiang River Estuary.

Speciation and distribution of phosphorus have a direct effect on the primary production and marine biogeochemistry. However, the complex current dynamics in aquatic critical zones such as large river delta and coastal area result in variable characteristics of the phosphorus speciation and distribution that need in depth study. The content, distribution and influence factors of total particulate phosphorus (TPP), particulate inorganic phosphorus (PIP) and particulate organic phosphorus (POP) in the suspended particulate matter (SPM) in the Zhejiang coastal area off Changjiang Estuary were discussed based on the investigation from April to May (spring), July (summer) and September to October (autumn) in 2016. The results showed that the content ranged from 0.13 μmol/L to 66.13 μmol/L, with an average of 3.35 μmol/L for TPP, from 0.03 μmol/L to 34.19 μmol/L with an average of 1.97 μmol/L for PIP, and ranged from 0.06 μmol/L to 31.94 μmol/L with an average of 1.39 μmol/L for POP. PIP was the dominant (52.3%) form of particulate phosphorus in the Zhejiang coastal areas. The percentage of TPP in total phosphorus ranged from 19.3% to 97.7% in spring for surface samples. The spatial distribution patterns of TPP, PIP and POP contents were similar in spring and autumn, decreasing from the inner bay to offshore areas. The content of TPP was higher in areas where the SPM was higher while PIP and POP showed a positive correlation with SPM, indicating an influence from terrestrial input. The regression coefficient and slope between POP and chlorophyll a were significantly higher than that of PIP in the area with salinity above 28 and SPM below 20 mg/L in spring, indicating contributions from phytoplankton to POP accumulation.

In view of the effect of internal solitary waves on the seafloor when encountering the seabed slope during their travel, the dynamic response of different slopes to internal solitary waves should be different. This paper studies the dynamic response process of internal solitary waves of slopes with different angles by creating internal waves in a flume. The results show that the internal solitary waves passing over the shelf slope will cause the accumulation of excess pore water pressure in the slope sediments; under the same amplitude conditions, the dynamic response amplitude of the gentle slope sediments is larger than that of the steep slope sediments; as the amplitude increases, gentle slopes occur the degree of dynamic damage is greater than that of steep slopes; the accumulation and release of excess pore water pressure exist at the same time before the stability of slope sediments is destroyed, and the increase of the amplitude of internal solitary waves will aggravate the release of excess pore water pressure. The results will play a guiding role in the dynamic study of the failure of slope sediment under the action of internal solitary waves and the analysis of slope stability.

Wind not only drives the surface ocean circulations, but also provides the main source of kinetic energy for deep ocean movements. This study focuses on the wind energy input to the north part of the North Pacific, including wind energy input to surface wave, surface geostrophic currents and surface ageostrophic currents. Results based on SODA3 (2000–2016) data show that there are obvious seasonal wind energy input gateways, which are the Subpolar Gyre for spring and autumn, the Eastern Pacific for summer and the Kuroshio Extension for winter respectively. The winter gateway gains the most wind energy among the four seasonal gateways, which is about 3−5 times higher than others. Since the beginning of the 21st century, wind energy input in winter gateway has weakened significantly, while increased in spring gateway, but has not changed significantly in summer and autumn gateway. For the spatial distribution of the trend in the 17 years, wind energy input to the surface wave is mainly dominated by the wind field, while wind energy input to the surface geostrophic current and ageostrophic current is dominated by the flow field. These mechanical energy input results are important for further understanding the ocean circulations in the North Pacific.

Grain size, clay minerals and major and trace elements of surface sediment samples collected from the East Siberian Arctic Shelf are analyzed. Based on factor analysis and cluster analysis the study area is divided into four provinces, the main sediment sources of each province are discussed. The results show that province I covers the estuary area of the Kolyma River and the Indigirka River. The sediments are mainly composed of silt and sandy silt, and characterized by higher content of SiO₂, TiO₂, Zr and low content of other elements. The ratios of La/Th and Zr/Hf reach the maximum in the four sedimentary areas. Illite is dominant which accounting for 70% of the whole clay minerals. This area is strongly influenced by terrestrial sources from the Kolyma River and the Indigirka River. Province II is located in the middle of the East Siberian Sea, where the sediments are generally silt and mud. The content of MnO, Ba, and Ni are relatively higher. La/Th and Zr/Hf ratio are slightly lower than that in Province I. Clay minerals composition is similar to Province I. The sediments in this area are mainly fine-grained derived by rivers, which are also influenced by sea ice process. As the distance increasing offshore, the content of marine authigenic components begin to increase. Province III is located in the northern East Siberian Sea, and sediments there are mainly mud. Elements such as Al₂O₃, K₂O, V, Li reach the maximum value in this area. The La/Th and Rb/Th ratios are similar to those in the Province II. The content of illite is the lowest, semctite and kaolinite reach the maximum (>10%). Fine-grained sediments in this area are probably influenced by Atlantic waters and the Beaufort Gyre. Province IV is located in Chukchi Sea where the sediments consist of silt and sandy silt. Elements are characterized by higher contents of CaO, P₂O₅. The ratios of Rb/Th, La/Th and Zr/Hf are the minimum values, the content of chlorite reach peak (>20%). Sediments in this area are significantly influenced by the Pacific inflow water.

In this study, elemental and mineral compositions of three surface sediments collected from the South Atlantic Ridge affected by hydrothermal activities of various degrees were analyzed, and series of extraction experiments for carbonate phase, Fe-Mn oxide phase and insoluble residual phase were carried out. Mixed reagent of hydroxylamine hydrochloride (HH) with different concentrations and 25% acetic acid (HAc) were used to extract Fe-Mn oxide phase from the sample. In order to corroborate the reliability of the extracting methods, Ti/Nd and Ti/Pb ratios of the Fe-Mn oxide phase, rare earth elements (REE) patterns as well as δCe and δEu ratios of different chemical phase were used to determine that the ideal reagent conditions for extracting Fe-Mn oxide phase from three different types of hydrothermal sediments were all 0.5 mol/L HH in 25% acetic acid. The results show that the higher the degree of influence of hydrothermal activities, the higher the contents of Fe, Cu, Zn and other elements in the sediments, and the contents of Ca, Sr and Ba show an opposite trend. Manganese, Pb and REE are not significantly affected by hydrothermal activities. As the influence of hydrothermal activity increases, the proportion of Ca, Sr and Nd increases in the Fe-Mn oxide phase and decreases in the residual phase, while Mn, Co, Ni and Zn have an opposite trend, and the proportion of Cu increases in the carbonate phase and decreases in the residual phase. Lead is not affected by the influence strength of hydrothermal activity and mainly occurs in the Fe-Mn oxide phase. REE mainly occur in the residue state. The occurrence state of REE shows that the more significant influence by the hydrothermal activities of the sediments, the more enrichment of REE in the residual phase. And the chondrite-normalized REE patterns of the residual phase exhibit that the enrichment of light REE are less obvious. This study provides methods for extracting hydrothermal fractions and valuable geochemical data for further understanding of the characteristics of hydrothermal sediments and the effects of hydrothermal activities on the occurrence state of elements in the South Atlantic Ridge.

Based on the CTD data from the 28th, 29th and 31st Chinese Antarctic Expedition cruises, we calculated dissipation rate of turbulent kinetic energy by using Thrope scale method, and analyzed the distribution characteristics of the dissipation rate and the structure of water masses in the Prydz Bay and its adjacent waters. Results show that the subsurface dissipation rate intensity of turbulent kinetic energy in the first two cruises reach maximum on the shelf break of Prydz Bay. Moreover, we compared the distribution of water masses among the three cruises and found intrusion of the modified circumplar deep water into the shelf happened on the 28th and 29th cruises. The the modified circumplar deep water could reach the depth of 100 m and 200 m on the cruise of 28th and 29th, respectively, and can extend southward to 67.5°S. Furthermore, the distribution of subsurface dissipation rate of turbulent kinetic energy on the shelf break of Prydz Bay are well related to the structure of local water masses. Therefore, the intrusion of the modified circumplar deep water into the shelf could induce instability of the local waters, promote water exchange and finally enhance local turbulent mixing.

Paleoproductivity and environmental evolution since 34 ka BP in the southeastern Scotia Sea, Antarctica were reconstructed by the chronological analyses of biogenic opal (BSiO₂), organic nitrogen (N_org), TFe₂O₃ and organic nitrogen isotopes (δ¹⁵N_org) in Core DC-11. Changes in BSiO₂ and N_org contents are basically consistent with the Antarctic temperature, being higher in warm times. δ¹⁵N_org is coincident with the Antarctic sea ice, being greater and reflecting enhanced nitrate utilization in surface water during cold periods. From Last Glacial, Last Deglaciation to Holocene, paleoproductivity and environment changed significantly, and the millennial variability such as the Antarctic Cold Reversal (ACR) is prominent in the study area. Sea ice plays an important role in correlations between the climate, nutrients and paleoproductivity. The increase of sea ice during the glacial or cold periods caused stronger stratification of surface waters, weaker upwelling of deep waters and their dissolved nutrients to the surface ocean, and then resulted in enhanced nitrate utilization and lower paleoproductivity in surface water. Iron supply in the study area is sufficient in present-day and Holocene while it is excessive during Last Glacial and Last Deglaciation due to more developed dust, which is obviously different from that in the Subantarctic Zone.

The sediments in the hydrothermal field received a large amount of hydrothermal input, and their mineral compositions and geochemical spatial distribution characteristics are effective indicators for polymetallic sulfide exploration. Due to gravity, sediments in the mid-ocean ridge area are mainly distributed in low-lying and flat terrain areas. In order to explore the influence of topographical factors on the distribution of sediments in the hydrothermal field, this paper proposes a prediction method of sediment distribution trend in seafloor hydrothermal field based on topography data through ArcGIS, and analyzes the topographic data of Dragon Horn area on the Southwest Indian Ridge, including the extraction gravity transport direction of sediment, the estimation of sediment accumulation amount, the extraction of submarine ditch valley and the division of sediment source area. By comparison and verification with the interpretation results of the seafloor camera data of the study area, we found that the prediction results are in good agreement with the actual distribution range of the sediments in the study area, indicating that this method can effectively indicate the distribution of sediments in the submarine hydrothermal field under the influence of terrain to a certain extent. This method has certain guiding significance for the exploration of submarine sulfide minerals, and could provides a reference basis for the setting of sampling stations for seafloor sediments and the delineation of polymetallic sulfide mineralization prospects.