The changes of shoreline caused by human activities affect the kinematic characteristics of tidal wave in the propagation process. Based on the hourly tidal level data from five tidal stations in the Wenzhou Bay from 1984 to 2019, the temporal and spatial variation of tidal wave patterns in this area and deconstructed the contribution of major tidal clusters to the tidal asymmetry is analyzed in this study . The results show that the tidal patterns in Oujiang Estuary and Yueqing Bay, two semi-enclosed embayments of the Wenzhou Bay, are obviously different. The tidal symmetry of Oujiang Estuary is flood-dominant tide and the tidal asymmetry increases continuously in the upstream direction, whilst tide is ebb-dominant in Yueqing Bay. Moreover, the tidal asymmetry shows distinct seasonal variation. The skewness ($ \gamma $) reaches maximum in June to July and December to January in the Wenzhou Bay. The tidal asymmetry in this area is mainly controlled by the component groups such as M₂/M₄, M₂/S₂/MS₄ and M₂/N₂/MN₄. The skewness caused by nonlinear interactions from M₂/S₂/MS₄, M₂/N₂/MN₄, O₁/K₁/M₂ shows obvious seasonal variation. Since 2000, the tidal asymmetry of Wenzhou Bay has been decreasing, which is related to the frequent reclamation surrounding the Oujiang Estuary.

A dataset of the high water lines extracted from 113 Landsat images from 1986 to 2019 and the measured profile data from 2015 to 2019 were used to examine the middle-term to long-term shoreline process and driver at the embayment scale in this paper. The results show that the western and eastern beaches of the Qiwang Bay, which is separated by one small bedrock headland, have four and three different spatial characteristics, respectively. More than half of the shorelines behaved nonlinear in their variation trends. Thus, we use the Mann-Kendall method to solve the problem of the lack of basis for the division of time periods. In addition, the east breakwater resulted in the unstable embayment planform due to changing the position of the controlling “headland” and therefore the longshore sediment transport from west to east is the main driver of the most recent shoreline. And the intervening small bedrock headland also influenced the spatial variability of erosion and accretion at the Qiwang Bay. These findings will have important theoretical and practical significance for predicting further shoreline position and reducing the risk of shoreline erosion.

Estuarine morphologies play an important role on tidal asymmetry. A two-dimensional numerical model is established with the Humber Estuary, UK as a reference site. A series of simulations are designed to examine the effects of the estuary cross-section shape, planform and convergence on the development of tidal asymmetry, whilst maintaining the same tidal prism. Model results show that deeper channels result in the lag and enhancement of phase difference whilst shallower channels result in a decline in the maximum ebb-tide velocity and longer period of ebb tide, and the estuary tends to be flood-dominated; narrow tidal flat tends to favour ebb dominance while broad tidal flat tends to favour flood dominance. Flood dominance is strongest in the convergent and long estuary. In addition, narrowing the estuary width will enhance the residual flow velocity of the main channel but weaken the residual flow velocity of the tidal flat. With the increase in estuary convergence, the residual flow velocity of the main channel increases but decreases on the tidal flat, and strengthen the flood dominance of the tidal flat. This paper further improves the research on the influence of estuary landforms on tidal asymmetry, which has certain guiding significance for reclamation and coastal engineering.

The Yellow Sea presents unique topographic conditions, and the tidal wave movement in this area has unique characteristics. In this paper, Geostationary Ocean Color Imager (GOCI) inversion and Oregon State University (OSU) tidal current model are used to obtain the sea surface currents field in the Yellow Sea. Based on the unique tidal wave system in the sea area, the tidal wave interference area is proposed and identified, and then the currents field of GOCI inversion is extracted. And partition of two kinds of trend data usability evaluation, through the validation of the drifting buoy data evaluation. The results show that the sea surface currents field obtained by GOCI inversion and OSU tidal current model has a certain degree of reliability. The AME value of sea surface currents field velocity obtained by GOCI inversion is 0.77, and that obtained by OSU tidal model is 0.49. On the whole, the currents field data obtained by GOCI inversion and OSU tide model are reliable to a certain extent. In the central area of the Yellow Sea near the tidal wave interference area, the consistency between GOCI tidal currents data and OSU tidal currents data is better than that of OSU tidal currents data, and their AAE values are 48.45° and 63.10°, respectively. In the coastal area of the Yellow Sea far from the tidal wave interference area, the consistency between the OSU tidal currents data and the measured data is better than that of the GOCI tidal currents data in terms of velocity magnitude and direction.

Based on the sea surface temperature (SST), which is the most dominant environmental climate factor affecting the distribution of squid, the potential habitat changes of Ommastrephes bartramii in July to October in 1996−2005, 2021−2030, 2051−2060 and 2090−2100 are analyzed using maximum entropy (MaxEnt) model with the historical climate data from 1996 to 2005 and the projection climate data from RCP4.5 and RCP8.5 scenarios. The results show that the fishing grounds of O. bartramii performs a seasonal north-south migration. Meanwhile, as the seasonal north-south migration of O. bartramii may be affected by the suitable SST range in fishing season, with the feature climate change the potential habitat distribution of O. bartramii from July to September in 2021−2030, 2051−2060 and 2090−2100 will move northward and the suitable habitat area will increase compare to 1996−2005 under both scenarios of RCP4.5 and RCP8.0. Under scenario of RCP4.5, the potential most suitable habitat for O. bartramii will move northward by 1°−2° and the suitable habitat area will increase by 3%−13% by the end of the 21st century. Under scenario of RCP 8.5, the potential most suitable habitat for O. bartramii will move northward by 3°−5° and the suitable habitat area will increase by 42%−80% by the end of the 21st century.

Sea ice thickness is one of the main sea ice parameters. Automatic recognition of sea ice thickness in video is a significant component of sea ice parameters extraction. In this paper, the machine vision method based on Hough transform is used to recognize the surface contour of sea ice, so as to obtain the sea ice thickness parameters. According to the characteristics of sea ice image, the overall recognition process is divide into image edge recognition, approximate line segment recognition and sea ice contour segment group recognition. In the process of line segment identification, three parameters of line segment group including angle, length and spacing are established based on the geometric characteristics of sea ice. In order to verify the reliability of the method, this method is applied to analysis the field survey data of Xuelong icebreaker’s eighth Arctic expedition. The results show that the three parameters have the optimal threshold value. When it is lower than this value, increasing the threshold will increase the effective recognition rate; when it is higher than this value, increasing the threshold will increase the false recognition rate. The ice thickness recognition rate can reach more than 90% by using the optimal threshold. Therefore, the ice thickness identification method based on Hough transform can realize the real-time monitoring of sea ice thickness.

The change of fluvial suspended sediment concentration (SSC) to the sea directly reflects the effects of riverine anthropogenic activities and natural force. Based on long-term hydrological data at Tarbert Landing Station of the Mississippi River (MR), statistical means, such as percentile method and Mann-Kendall method are used to detect change process of SSC from the MR entering the Gulf of Mexico in recent 40 years, and associated possible influencing factors. The results show that: (1) SSC from the MR entering the Gulf of Mexico is characterized by a staged decline from 1976 to 2015, in the first stage from 1976 to 1987, the SSC is relatively high with an average value of 0.33 kg/m³; in the second stage from 1988 to 2015, the SSC is much lower with a mean value of 0.25 kg/m³. (2) The relationship between daily SSC and runoff of MR follows Gaussian distribution. Compared with the first stage (1976−1987), the rating curve between SSC and runoff in the second stage (1988−2015) is relatively flat, when the number of high daily SSC event over 0.60 kg/m³ reduces significantly. SSC increases with the runoff in low-action flows and reaches the maximum when the runoff approaches 20 000 m³/s, but decreases with the runoff thereafter. The rating curve between monthly SSC and water discharge of the MR exhibits “double-loop” shape during 1976−1987, but presents clockwise “single loop” with “sediment before water” during 1988−2015. (3) Flood diversion project construction and soil conservation measures dominate the fluvial SSC from the MR into the Gulf of Mexico. The construction of flood diversion engineering reduces the sediment source along the river channel, and the soil conservation measures repress the land erosion, which have combined to keep the SSC at a relatively low level. In addition, SSC in the MR presents minor response to extreme hydrological events.

In order to quantitatively study the sheltering effect between multiple ridges keel on sea ice drift, the laboratory experiment is carried out in a tank, which is 0.45 m deep. The shape of keel models is a triangle with 45° slope angle, 4 keel depths and 9 keel spacings are selected in the experiments. The variations of the front and back keel drag force and its ratio under wake effect is investigated. The drag force on the front keel is not affected by the back keel and keeps a linear relationship with the square of keel velocity; however, the drag force of back keel appears negative value (opposite direction) when the keel spacing is small. With the increase of the spacing the drag coefficient of the back keel first decreases and then increases to a constant. The variation of the ratio of drag forces between the front and back can be described by an exponential sheltering function, which is related to keel spacings and keel depths, and independent of keel velocity. Compared with the sheltering functions which are used in present sea ice models, the exponential formula is given and improves our understanding about sheltering function in sea ice dynamic model.

Atmospheric correction (AC) is the basis and premise of quantitative remote sensing of water column. The effects of different AC models on water depth inversion from the four aspects of AC model, AC model parameters, water component differences, and water depth inversion band combination are discussed in this paper. The research uses 6S, FLAASH, ACOLITE and QUAC four AC models, select continental, marine and urban aerosol patterns, and the shallow waters around the northwest side of Oahu Island and Shemya Island are used as the study area of clean water, while the shallow waters around Liaodong Shoal and Penang Strait are used as the study area of turbid water. AC is performed based on Landsat-8 multispectral images, and eight wavebands are used for bathymetric remote sensing inversion. The results show that: (1) all the four AC models can weaken the atmospheric influence on the water signal to some extent; the correction results of different models are somewhat different depending on the parameter selection and the components of the water column. And the peak reflectance of the two types of water column occurs in the blue and green bands, respectively. (2) The 6S model is more robust, and the bathymetric inversion results of this model are less volatile than the rest of the models due to the changes in the components of the water column. The water depth inversion results of the two aerosol models of the FLAASH have more obvious differences in turbid water, and the difference of MRE in shallow water of Liaodong Shoal is 7.9%; the ACOLITE model is significantly influenced by the water column type and has superiority and stability for turbid water, and the MRE is 5.6% lower than that of FLAASH. (3) The accuracy of multi-band water depth inversion is generally better than that of single-band, but there is no significant correlation between the accuracy of inversion and however, there is no significant correlation between the inversion accuracy and the number of bands; the combination of bathymetric inversion bands has different sensitivity to different study areas, the inversion accuracy of the three-band model is better in clean water, and the inversion accuracy of the four-band model is optimal in turbid water, and the MRE is reduced by 5.6% compared with the three-band model.

Tidal-current-asymmetry (TCA) influences sediment transport and geomorphologic changes. It is of paramount importance to understand the current asymmetry in this area in context of a long-term scale with consideration of development and protection of the coastal resources. The radial sand ridges (RSR) in the South Yellow Sea is patterned with strong tidal forcing and complex hydrodynamic environment. This paper simulated tidal current field in the RSR based on the Delft3D model and used combined harmonic analysis and skewness theory to analyze the spatial distribution of the TCA under varied shoreline conditions. The results show that peak-current-asymmetry (PCA) in the RSR is mostly flood-dominant and slack-water-asymmetry (SWA) also shows positive, meaning the flooding duration is shorter than the ebbing duration. Both the positively-dominant PCA and negatively-dominant SWA are mainly affected by the nonlinear interactions between the semidiurnal diurnal tides (M₂, S₂) and shallow water tides (M₄, MS₄). As the shoreline gradually moves towards sea during 1984 to 2014, although the nature of $ {\gamma }_{\mathrm{P}\mathrm{C}\mathrm{A}} $ remains, the magnitude of which increases by up to 25%. Meanwhile,$ {\gamma }_{\mathrm{S}\mathrm{W}\mathrm{A}} $ decreases by up to 20%, which intensifies its shorter-flooding-duration pattern in the core area of the RSR.