The Brazil-Malvinas Confluence (BMC) may have a southward shift in a long time trend and many marine factors’ change may cause this drift. We analysis this phenomenon from two aspects: the changes of currents’ volume transport, and the winds’ alternation. Using the monthly mean flow field between 1993 and 2016 to calculate the cross-sectional water transport volume, the results show that the transport change trend of the Malvinas Current (MC) is decreasing and the transport change trend of the Brazil Current (BC) is increasing. The trajectory of the Argo buoy during 2014–2016 indicates that the MC’s water mainly comes from one of the three polar fronts of ACC (Antarctic Circumpolar Current) when passing through the Drake Passage: SAF (the Subantactic Front). Calculating and analyzing the transport of SAF, we find that the transport’s trend of SAF is lessened, which is an important reason caused the reduce of MC’s transport. We also find that the PF’s transport on the south SAF has incremental trend. Based on the monthly mean wind field data during year 1993–2016, we find that the prevailing westerly wind stress in the Southern Hemisphere is growing and moves toward to Antarctic which will make ACC contract to Antarctica. So we can explain that the transport of SAF reduces while the transport of PF increases. Therefore, it is found that the southward movement of the prevailing westerly winds in the Southern Hemisphere and the increase of BC transport are the reasons for the southward drift of BMC.

Based on the Okada model, nonlinear shallow water equation, and nested grid with high resolution, a real-time tsunami warning system of transoceanic-offshore-local is built for Wenzhou and Taizhou’s coastal region of Zhejiang Province. The grid resolution of the refined layer is 900 m. The tsunami warning system includes parallel numerical calculation module, visualization module based on Python 2D library (matplotlib), and product integration module which integrates all numerical graphical products on a web page by Python. Once an earthquake occurs, the system could complete the numerical calculation, visualization processing and graphic product integration within 10 minutes. Firstly, the system has been validated by the 2011 Japan tsunami with the magnitude of M _w 9.0. Then, the extreme potential tsunami from Nankai Trough and Okinawa Trough is simulated by the system in terms of tsunami amplitude and currents. The results show that the tsunami warning system can improve the efficiency and accuracy of tsunami early warning in the coastal region, and provide a scientific basis for tsunami early warning, disaster reduction and decision supporting.

The muddy coast has a large change in scouring and silting, and the beach profile is diverse. Firstly, according to the tidal range relationship between muti-temporal remote sensing watelines, the shape of the shoreline is automatically judged, and then the different functions are used to fit the profile. A new method of coastline remote sensing prediction based on self-adaptive profile morphology is constructed. The central muddy coast in Jiangsu has been empirically applied. The research shows that the concave-shaped erosion shore section, the slope-shaped gentle bank section and the upper convex-shaped siltation section use a three-exponential decay function, a linear function and a second-order polynomial function respectively to have a good profile fitting effect, using three waterlines. The absolute slope error of the profile obtained by data fitting is 0.20‰, –0.17‰, and 0.13‰, respectively, which is less than an order of magnitude than the measured average slope. When using the five waterlines data fitting to calculate the coastline, the error of the coastline plane position of the erosion shore section and gentle shore section are 6.5 m and –91.96 m, respectively, and the error is reduced by about 82.4% compared with the average slope method. Further consideration of seasonal changes in the beach, using the waterline data of the winter to calculate the coastline, has little effect on the erosion of the shore and the long section of the silt, but for the slope-shaped smooth section, the error is reduced by about 63.65%, so the use of winter waterline data has a higher shoreline projection accuracy than the season without distinction.

As a main carrier of nutrients and pollutants, total suspended matter (TSM) has a significant influence on water environment, especially on estuary water environment. The Ocean and Land Colour Instrument (OLCI) was onboard ESA Sentinel-3A satellite and launched in February 16, 2016, with fine spatial, temporal and spectral resolution. To find the best atmospheric correction method and TSM retrieval model for the application of OLCI in Hangzhou Bay (HZB), six atmospheric correction methods and eight TSM retrieval models were test based on in situ water color data collected from HZB on July 2017. In addition, the OLCI Level 2 product (e.g. TSM and inherent optical properties (IOP) data) was compared with in situ data to evaluate the accuracy and applicability of OLCI Level 2 product. The results show that the method of atmospheric correction based on ultraviolet wavelength (UVAC) and the TSM retrieval model based on band ratio have best performance. Specifically, the mean absolute percentage error (MAPE) of atmospheric correction in four match-up sites is 34.21%, 13.11%, 5.92% and 20.28%, respectively. In addition, the averaged MAPE of atmospheric correction in band Oa2 to Oa12 and Oa16 to Oa18 is 15.23%, and in band Oa4 to Oa10 is less than 8%. The band ratio (Oa16/Oa5) model has the best performance, with a MAPE of 16.49% and root mean square error (RMSE) of 50.92 mg/L in calibration stage, and a MAPE of 19.08% and RMSE of 19.29 mg/L in validation stage. However, the TSM and IOP product derived from C2RCC (case 2 regional coast colour) algorithm and the TSM product derived from OLCI Level 2 product has no linear relationship with in situ data. These results indicate that the above Level 2 product is unsuitable for HZB TSM and IOP remote estimation. Finally, the UVAC method and band ratio model are applied to OLCI imagery that is collected on July 23, 2017. Spatially, TSM shows a relative low value in the center of HZB and relative high value in the south and east part of HZB.

Mesoscale eddies are widely distributed in the ocean and play a significant role in the mixing and transporting of momentum and nutrients. Statistics suggest that more than 80% eddies’ lifetime are less than 1 month, belonging to the defined “short-life eddies” in this paper. This design adopt statistics and comparison, commit to having a earlier reasearch of global scale, short-life eddies. Results show that short-life eddies have a close correlation with ocean current. The most productive places for short-life eddies are those where warm and cold currents or two currents with opposite directions meet, and except in tropical areas of 30°S–30°N, the short-life eddies in other areas have a slight preference for cyclonic. Seasons with low temperature are favorable for short-life eddies in low latitudes, while seasons with high temperature are favorable in high latitudes. Short-life eddies tend to propagate westward in most of areas, however, they notable propagate eastward in eastward currents areas. Meridional deflection is quite messy, but with a tiny preference for equatorward and poleward deflections of cyclones and anticyclones, respectively. The distribution of average displacement and propagation velocity have similar regulation.

Analyses of grain size, organic carbon and biomarker have been carried out for the core ANT32-RB16C, in order to identify the source of organic matter and reconstruct the sedimentary environment since the Last Glacial Maximum in the western Ross Sea. From the bottom to the top within the core, sub-ice-shelf, pre-ice-shelf and open-marine sedimentary environments can be differentiated. The combined parameters of biomarker indicate that organic matter is mainly a mixed input of terrigenous and marine origin. During the Last Glacial Maximum (24.8–20 ka BP), under the influence of ice sheet and the current condition, the organic matter content was low and its source was associated mainly with a marine origin, with a relatively low plankton productivity. During the Last Deglaciation (20–11.7 ka BP), the organic matter released by the dissolution of the glaciers in the retreat process of the Ross Ice Shelf, caused the increase of terrestrial organic matter. During the Holocene, the content of organic matter increased significantly, together with the proportion of marine origin input. The number of prokaryotes such as bacteria increased, resulting in a greater degree of degradation of short-chain n-alkanes. The redox condition in the study area is mainly affected by the ice shelf and sea ice limitation, and has little relationship with the organic matter content and the high-oxygen Antarctic Bottom Water. In general, from the Last Glacial Maximum to the Last Deglaciation, the study area sedimentary environment was affected by the Ross Ice Shelf, and by the climate since the Holocene.

Aiming at the characteristics of SAR images on the ocean surface, the texture feature method based on gray level co-occurrence matrix is a common method for extracting oil spill information from the sea surface, but the complex information on the actual ocean surface makes the SAR image produce a dark spot area similar to the oil spill phenomenon. The false alarm rate is obtained when the oil feature information is extracted by the texture feature method, and the extraction precision of the oil spill information is reduced. Based on the RADARSAT-2 SAR quadratic polarization image, this paper proposes a texture feature recognition method based on SAR polarization ratio image to identify and extract the oil film on the sea surface. The results show that the texture feature recognition method based on SAR polarization ratio image can effectively and accurately extract the oil spill information on the sea surface. Compared with the texture feature recognition method of VV polarization image, the false alarm rate in the oil spill monitoring process is reduced by 17.96 %, the overall accuracy of oil spill monitoring reached 96.83%.

Sand waves are widely distributed in the world and have complex genesis. And multi-scale complex sand waves often overlap to form a complex sand wave geomorphology system, which makes it difficult to conduct quantitative research. To solve this problem, a practical Fourier analysis method is proposed in this paper, and Butterworth filter is designed to transform water depth data into frequency domain, and then decompose complex sand wave geomorphology into a series of single types of sand waves in different frequencies. Taking the complex sand wave geomorphology system of Taiwan Banks as an example, three spatial scales of sand waves are quantitatively decomposed, which are: giant sand waves (over 100 m in length, over 5 m in height), medium sand waves (wavelength of 5–100 m, wave height of 0.4–5 m) and sand ripples (wavelength less than 5 m, wave height less than 0.4 m). The quantitative analysis method of sand waves proposed in this paper is helpful to study the genesis and mechanism of sand waves in different scales, and is also of practical value to the safety assessment of marine engineering in sand wave fields.

Winter-to-winter recurrence (WWR) is an important persistence characteristic of large-scale sea surface temperature anomalies (SSTAs) in middle-high latitude, which is a unique phenomenon of the extratropical ocean. Its influence on extratropical climate change can not be ignored. WWR also exist in the atmosphere in the North Pacific Ocean, which could induce SSTAs WWR. In this paper, the WWRs of the air-sea system in the North Pacific are evaluated using the model output of 23 coupled models of CMIP in IPCC 4th assessment. Observational results show that, SSTAs WWR occurs over most of the basin of North Pacific, but the recurrence timing is in winter in the central and in fall in other regions. The atmospheric WWR is mainly located in central North Pacific, which is essential for the occurrence of the SSTAs WWR. Most of models can simulate the basinwide SSTAs WWR, but they can’t reproduce the geographical distribution of recurrence timing well. Compared with the SSTAs, little skill is shown in the WWR of the atmospheric circulation in most models. Moreover, the possible effect of the atmospheric WWR on the SSTAs WWR is not reflected in these coupled models. The coupling model has yet to be improved for simulating the atmospheric WWR in the North Pacific.

The statistical characteristics of rapid changes of different grade tropical cyclone intensity and path in the South China Sea are analyzed by the best track data set of tropical cyclones for 69 years from 1949 to 2017 compiled by Shanghai Typhoon Institute of China Meteorological Administrator. The results show that: (1) The change from a severe tropical storm to a typhoon, and from a typhoon to a severe typhoon, are the most frequent events of rapid intensity changes. Most tropical cyclones experience intensity change no more than twice. However, most of the rapid intensifying tropical cyclones occur mainly outside the South China Sea in the western Pacific, and the probability of rapid intensifying over the South China Sea is only 9.8%. (2) The duration of intensity maintenance has an important effect on rapid intensity changes for different grade tropical cyclones. It is the highest rapid change stage during the first 24 hours. Rapid intensity change to typhoon or above grade is easily to occur when the decreasing velocity of central pressure exceeds –12.0 hPa/(6 h). Moreover, the rapid intensifying of tropical cyclones is easily to occur in areas with high sea surface temperature. (3) The deflection of the tropical cyclone path in the South China Sea is mainly in the westbound path, in which the deflection of 5°–30° is the most common, accounting for 48.65% of the total number of tropical cyclones. However, According to the defined path mutation criterion, the probability of path sharp turning is only 15.13%. With the increase of tropical cyclone intensity, the frequency of path sharp turning in the South China Sea decreases rapidly, and the path sharp turning occurs mainly in the coastal area and the east-central region of the South China Sea. This work further refines and enriches the understanding of the intensity and path rapid changes of tropical cyclones in the South China Sea.