The storage pressure and reconstruction of the mesostructure of gas-bearing sediments are key factors in the study of shallow gas geohazards. Using an industrial CT scanning test system, vertical rotational (SR) scanning is used, with the position of the microfocus X-ray source fixed and the sample rotated at a constant speed of 360° along the XY plane, with a set rotation step of 0.3° per second, the gas-bearing samples in the reactor are pressurized to 2 MPa, 4 MPa, and 6 MPa, taking into account the best resolution of the sample imaging, the best detection range and other. The results show that the slices and reconstructed images obtained from the CT scan have good experimental results; the greyscale values of small bubbles increase when pressurized to 2 MPa; the overall greyscale values of gas increase significantly when pressurized to 6 MPa; the number of bubbles decrease with increasing bubble radius during the pressurization process; the pressurization process lead to local changes in the solid-liquid-gas phase, which show that the volume of pore gas and pore water changes more than that of the soil skeleton. The overall change is greater than that of the soil skeleton, and the microscopic local location will have a greater rise or decrease. When the gas content at different locations rises and dominates, it will drive the reduction of pore water and the movement of the soil skeleton.

Using in-situ hydrographic observations from January to December 2017, 3D thermohaline structure and seasonal variation in the Zhanjiang Bay is investigated in this study. The results show that: (1) In 2017, the annual mean temperature is 23−27℃, the mean salinity is 19−27, the mean potential density is between 11−17 kg/m³, and the mean buoyancy frequency (N²) is about 7×10⁻⁵−5×10⁻³ s⁻² in the Zhanjiang Bay. The vertical structure and horizontal distribution of N² are similar to that of the temperature, while the distributions of potential density and salinity are similar. (2) The temperature has significant seasonality with the highest value in summer, followed by autumn, and the lowest in winter. The maximum temperature difference between winter and summer reaches 15℃, while the seasonal mean of the salinity varies slightly. The ebb and flood have less influence on temperature and salinity, comparing with their seasonal variations. The thermocline is the strongest in summer with the maximum gradient reaches 0.7℃/m at 10 m, whereas it shallows to 5 m in spring and fall, and the water well mixed in winter. The halocline is prominent in summer and fall, with the maximum gradient 1.1 m⁻¹. The seasonal variation of the thermohaline in the upper layer and lower layer are consistent. (3) For the horizontal distribution, the temperature decreases and the salinity increases from the bay head, the mid bay, the bank region, the shoal region to the bay mouth. The average temperature difference between the bay head and the bay mouth is 2.3℃, and the salinity difference is 2.7. The temperature-salinity (θ-S) diagram shows banding distributions with one end as the low-temperature and high-salinity water in the bay mouth, one end as the high-temperature and low-salinity water in the bay head, and the other water masses are between them. Different bands are shown in different seasons.

Numerous engineering projects show that beach nourishment is a common method against coastal erosion. Beach nourishment is an artificial process of adding sediment to a beach to increase beach width and protect it from erosion. In this paper, a 1D numerical model for beach profile was established and verified by the results of physical model experiment. In addition, the rates of profile change to equilibrium profile on different positions and different sand volume schemes were calculated, and the efficiency was compared and analyzed. To analyze the protection effects of beach nourishment, the profiles in nourishment schemes and no nourishment schemes after storm condition were compared. It turned out that when the nourishment volume was large the efficiency of bar nourishment under the calm condition was higher than of berm nourishment, and the nourishment effect under the storm condition was better. This study has important implications to save construction costs and raise working efficiency during the practical nourishment engineering. In the meantime, it sheds light on evaluating the effect of beach nourishment.

Using the direct observation data of the MSS90L turbulence profiler obtained in the summer cruise of the Changjiang River Estuary scientific investigation and experimental study (NORC2019-03-02) in July 2019, in this paper, the distribution of the turbulent kinetic energy dissipation rate ε and the vertical turbulent diffusion coefficient Kz are calculated and analyzed. The turbulent kinetic energy dissipation rate is 1.72×10⁻¹⁰ W/kg to 2.95×10⁻⁵ W/kg, and the vertical turbulent diffusion coefficient is 3.24×10⁻⁷ m²/s to 4.55×10⁻² m²/s. The distribution of the turbulent kinetic energy dissipation rate and the vertical turbulent diffusion coefficient are similar, both of which are the strongest in the upper layer, the next in the bottom layer and the weakest in the middle layer. In the upper layer, due to wind stress, the turbulent kinetic energy dissipation rate and vertical turbulent diffusion coefficient are larger; the stratification is stronger at the thermocline, which suppresses the dissipation of turbulent kinetic energy and vertical turbulent mixing. The secondary circulation of the salinity front will promote the separation of the low salt water mass, and the vertical circulation caused by the front will enhance the turbulent mixing of the ocean. The energy exchange between the low salt water mass and the outside world is less, and the turbulent kinetic energy dissipation rate is weaker. There are obvious upwelling and downwelling in the Changjiang River Estuary, which are produced by the secondary circulation of the front; the existence of upwelling and downwelling promotes the dissipation of turbulent kinetic energy and turbulent mixing.

Tropical cyclone disaster is one of the most serious natural disasters, and its impact mainly depends on the center location and the intensity. Monitoring the location and the intensity of tropical cyclones is of great significance for improving the accuracy of tropical cyclone forecast and for reducing the impact of tropical cyclone disasters. In this paper, the characteristics of the HY-2B scatterometer wind field, as well as its divergence and curl, are analyzed. It is found that the divergence or curl of the wind field near the cyclone center shows remarkable signatures, such that a new method is proposed to identify the cyclone center, and then the results are compared with the conventional method. Moreover, a method for estimating the size of the tropical cyclone is introduced to evaluate the cyclone intensity. Finally, the remote sensing data of Typhoon Francisco and Typhoon Bualoi are used to verify the proposed methods. The results show that the difference between the cyclone center position determined by the scatterometer and the one of the optimal path is generally less than 20 km. Meanwhile, the determined wind radii correspond well with the development of the tropical cyclone.

The radionuclides ⁷Be, ²¹⁰Po and ²¹⁰Pb transported by the atmosphere can be used as important tracers for studying the material deposition flux of the Arctic Ocean’s atmosphere, modern ocean sedimentation and the transport of materials into the sea ice. They have been widely used in the study of air mass movement, soil erosion, and particle circulation processes in water systems. This paper reports the activities of ⁷Be, ²¹⁰Po and ²¹⁰Pb in the surface snow of the high-latitude ice floes of the Arctic Ocean in 2018. The activity concentrations of ⁷Be, ²¹⁰Po and ²¹⁰Pb are 33.6−632.68 mBq/L, 36.2−87.5 mBq/L, and 30.9−194.49 mBq/L, respectively. The activity concentrations of ⁷Be and ²¹⁰Pb in the surface snow of the Arctic Ocean are lower than those in the mid-latitude continental areas. The results show that the activity concentrations of ⁷Be in snow increased with the increase of latitude. The activity ratio of ²¹⁰Po/²¹⁰Pb ranged from 0.70 to 1.48 (with an average of 0.93), ²¹⁰Po is almost in equilibrium with ²¹⁰Pb. It indicates that the age of the surface snow is “older”.

In order to explore the effects of low temperature stress on the expression of genes related to lipid synthesis and catabolism in cobia (Rachycentron canadum), the experiment set up a normal temperature group (30.5±1.0)°C and a low temperature group (20.0±0.5)°C, and used real-time fluorescent quantitative PCR (qRT-PCR) to analyze the expression levels of 5 target genes in liver, muscle and intraperitoneal fat (IPF). The results showed that at 1 d, the expression of carnitine palmitoyl transferase-1 and hormone-sensitive lipase genes of liver, carnitine palmitoyl transferase-1, hormone-sensitive lipase and monoacylglycerol lipase genes of muscle were up-regulated (p<0.05), acetyl-CoA carboxylase and fatty acid synthase genes of liver, muscle and 5 lipid metabolism related genes of IPF were significantly down-regulated (p<0.05); at 4 d, the expression of carnitine palmitoyl transferase-1, hormone-sensitive lipase and monoacylglycerol lipase genes of liver, and hormone-sensitive lipase, monoacylglycerol lipase, acetyl-CoA carboxylase, fatty acid synthase genes of muscle and carnitine palmitoyl transferase-1, hormone-sensitive lipase, monoacylglycerol lipase, acetyl-CoA carboxylase genes of IPF were up-regulated (p<0.05), acetyl-CoA carboxylase and fatty acid synthase gene of liver were down-regulated (p<0.05); at 7 d, the expressions of carnitine palmitoyl transferase-1, hormone-sensitive lipase, monoacylglycerol lipase, acetyl-CoA carboxylase genes of liver and IPF, and hormone-sensitive lipase, monoacylglycerol lipase, acetyl-CoA carboxylase genes of muscle were up-regulated (p<0.05), carnitine palmitoyl transferase-1 gene of muscle and fatty acid synthase genes of liver were down-regulated (p<0.05). The results showed that cobia responded to low temperature stress by inhibiting lipid synthesis and metabolism, promoting lipid hydrolysis in the liver and muscle, and inhibiting the lipid hydrolysis of IPF in the early stage of low temperature stress; in the late period of low temperature stress, cobia lipid synthesis and catabolism were significantly increased, and the main tissue that used fatty acids to provide energy was transformed from the liver and muscle to liver and IPF.

Based on the outputs of eight earth system models involved in the Coupled Model Intercomparison Project Phase 6 (CMIP6), this study assessed the simulation skill of the Southeast Indian subantarctic mode water (SEISAMW) of these models by comparing with observations. Moreover, this study investigated the projected long-term trends in subduction rate, volume and properties of the SEISAMW under medium and high greenhouse gas emission scenarios (i.e., SSP245, SSP585). The results show that the CMIP6 models generally have produced artificially greater mixed layer depth and smaller upper layer potential density in comparison with those of the Argo observation. Consequently, the simulated SEISAMW in the CMIP6 models are generally with larger subduction rate and smaller potential density. Meanwhile, the subduction regions of the SEISAMWs show significant differences among the analyzed CMIP6 models, which are attribute to lateral induction in the mixed layer. Furthermore, in the historical, SSP245 and SSP585 outputs, the SEISAMWs show consistent decreasing trends in subduction rate and volume, increasing trend in temperature, and decreasing trends in salinity and potential density. The long-term trends of the SEISAMWs are largest under SSP585 scenario, followed by the SSP245 scenario and historical simulation. The projected trends of SEISAMW can be explained by the following mechanism: the temperature and freshwater flux in the southeastern Indian Ocean upper layer tend to increase under enhanced radioactive forcing, resulting in shoaling in mixed layer and flattening of the mixed layer gradient. As a result, the trends of SEISAMWs in subduction rate, volume and water properties show larger values in accordance with stronger radioactive forcing.

Data measured by ultrasonic anemometer moored at a fixed platform near Maoming City, Guangdong Province from February 15 to May 8, 2012 has been used to analyze turbulence within wave boundary layer. The results confirmed that under swell conditions, there are areas obviously affected by swell in the cospectrum and Ogive curves. Furthermore, the sign change of wave-induced Reynolds stress is related to wave age. This paper presents the statistical distribution of the sign reversal of the Reynolds stress caused by the waves in the along-wind and cross-wind directions with wave age. In addition, this paper extracts the wave-induced Reynolds stress τ_swell based on cospectrum method, and compares it with the wave-induced Reynolds stress τ_*swell calculated by traditional method. The results show that the value of τ_swell is 2−3 orders of magnitude larger than that of τ_*swell, which indicates that the traditional method significantly underestimates the wave-induced Reynolds stress, and the traditional method needs to be improved.

Numerous random wave trains are simulated based on the JONSWAP spectrum using the Longuet-Higgins wave model, and then extreme waves are investigated based on the wave trains with stable probabilities of freak waves. The probabilities of freak waves are smaller than those of based on Rayleigh distributions. With the spectra narrower, the probability of freak waves increases. During the fixed times, the frequency of freak waves obeys the Poisson distribution and time intervals satisfy exponential distribution. The most probable occurrence frequency of freak waves decrease and intervals of freak waves are longer with the spectra wider. Wave groups are discriminated based on wavelet spectra and their characteristics are analyzed. There are no more than four freak waves in wave groups. The probability of wave groups containing merely one freak wave is the largest. Numbers of freak waves in wave groups are increasing with the spectral narrower. Furthermore, time lengths of wave groups containing freak waves satisfy Generalized extreme value distribution (GEV distribution), and with spectra narrower, the most probable lengths of the wave groups increase.