Archive

Internal waves occur frequently in Andaman Sea, and the study of its internal waves is the hotspot of ocean research today. In this study, more than 3 000 Terra/Aqua MODIS, GF-1, Landsat-8 and Sentinel-1 satellite remote sensing images covering the entire Andaman Sea from 2013 to 2016 were analyzed to obtain spatial and temporal distribution and wave direction feature of internal waves in the Andaman Sea. The statistical result shows that internal waves can be observed by the remote sensing mostly in four areas: north of Sumatra Island, middle of the Andaman Sea, north of the Andaman Sea and west of Nicobar Islands. The internal waves with a relative large spatial scale in northern Sumatra and middle of the Andaman Sea are more active in the Andaman Sea. No internal waves in the deep sea and the gradually changing bathymetric gradients areas of the Andaman Sea have been observed by the remote sensing. The distribution of observed internal waves is similar each year from 2013 to 2016 in the Andaman Sea. Internal waves can be observed in the Andaman Sea all through the year, most in February to April (hot season), next in August and September (rainy season), A minimum number of internal waves are observed in June, however, this may be caused by the small amount of clear optical images in rainy season in the Andaman Sea, it needs to further prove by using more remote sensing images. From the directions distribution, most internal waves propagate to the coast. Internal waves propagate eastward or southeastward in north of Sumatra Island and middle of the Andaman Sea, southeastward or southwestward in eastern Andaman Island. In addition, we found some internal waves propagate from the Andaman Sea to the Bay of Bengal.

The South Atlantic Ocean (SAO) connects the North Atlantic, Indian and Southern Oceans. The variability of SAO Ocean Heat Content (OHC) would improve our understandings of the heat redistribution among global ocean basins in a warming climate. In is study, we analyze the spatial and temporal variability of the upper-layer OHC of SAO from European Centre for Medium-Range Weather Forecasts Ocean Reanalysis System 4 data sets and temperature data sets of Institute of Atmospheric Physics of the Chinese Academy of Sciences. Using empirical orthogonal function (EOF) analysis, the OHC of upper 700 m in the Southern Atlantic shows a basin wide warming during the past 60 years. This warming trend is even more apparent and have longer fluctuation cycle with a deeper integration depth for OHC. Correlation analysis shows that leading EOF mode of SAO OHC is dominated by decadal or longer time scale variabilities, with a 9-12 years leading of AMO, suggesting SAO OHC contribute to the North Atlantic climate variation. The SAO OHC-AMO correlation increases with the increased OHC integration depth while SAO OHC-PDO correlation decreases. Besides, it is found that variation of OHC in the whole basin is positively correlated with variation of thermocline depth, and the variation of OHC reflects the dynamical fluctuation in the thermocline.

Wave set-up and wave-induced current are the significant dynamics for sediment transport, geomorphology and pollutant diffusion in estuaries, however, researches were rare under remote typhoon conditions in the Changjiang Estuary. In this study, we focused on the spatial distribution of wave set-up and wave-induced current under a remote typhoon named “Sanba” by a coupled 3-D model of typhoon-wind, tide and wave. The results showed that the radiation stress and wave set-up increased when wave propagated from the typhoon eye to coast due to wave energy dissipations, the maximum value of wave set-up could reach up to 0.05~0.20 m, which was 15%~22% of the total water level rise induced by typhoon. The along-shore current generated by wave were about 0.05~0.20 m/s, and could reach up to 15%~50% of storm-induced current. It implied that a remote typhoon could have significant influence on wave set-up and wind-induced current. The research could provide the basis for calculation of return period water level and current, sediment transport, geomorphological evolution of subaqueous delta and so on.

In this study, a numerical model based on TELEMAC-2D was developed for the Pacific Ocean and the China Seas to simulate the propagation of the tsunami wave of the Honshu (Japan) tsunami event on March 11^th, 2011. After validated against in-situ observation data from buoys, the influence of this event on the Yueqing Bay was investigated. By using a spectrum analysis, the amplitudes and phases of the resonance waves in the Yueqing Bay were found with the dominating periods of 240 min, 180 min and 103 min. A regional model driven by a white-noise-like boundary condition further elucidated the property of the natural oscillation at these periods, further supporting the finding of the three resonance modes. Moreover, the white-noise-driven model suggested that maximum amplitudes would appear both in the upper bay and at the bay mouth when tsunami disasters occurred. The conclusion of this paper can be instructive for disaster management and reduction of local governance.

Using RAM (Range dependent Acoustic Model) model which was based on parabolic equation algorithm and combined Argo floats with multi-satellite data, effects of typhoon on acoustic propagation characteristics for incomplete deep-sound channel(3 000 m) and complete deep-sound channel(5 500 m) were researched. Results show that the influence of typhoon on sea water is confined in surface layer, which is characterized by the thickening of the mixed-layer, zero temperature gradient and positive sound speed gradient in the mixed-layer. At a certain depth below the mixed-layer, the water temperature increases, and the corresponding sound speed increases. When the sound source is placed in the mixed-layer, sound propagation in sea surface layer will be affected, the surface waveguide sound propagation and leakage modes appear in both incomplete and complete deep-sound channels. When the source is under the mixed layer, typhoon makes the convergence zone close to the sound source under the condition of incomplete deep-sound channel.Under the condition of complete deep-sound channel, the disturbance of typhoon on the location of convergence zone is not obvious, but the flip depth of the sound wave increases nearly 500 m.

Space-borne Synthetic Aperture Radar (SAR) has become one of the new methods for the research of the offshore wind energy resources remote sensing. In this study, progress on the study of offshore wind energy resources remote sensing by space-borne SAR has been reviewed. Especially both the technology and application of the offshore wind energy resources remote sensing, and also the offshore wind turbine wake remote sensing by space-borne SAR are mainly introduced. Meanwhile, we discuss some issues in the present of the studies on the offshore wind energy resources remote sensing by SAR and the research orientation in future.

Higher demand of coastal large-scale projects defense capacity should be put forward together with the frequent marine disaster (MD) such as storm tide. This study investigated the design standard and status quo of Guangxi Beihai Port Shibuling Harbor Project in the coastal defense project (CDP), analyzed the design standard and parameters of storm surge and ocean waves, and evaluated the MD defense capacity of each section by comparing the right theoretical CDP elevations with the measured ones. Results show that evaluation result of extreme high tide level in consideration of sea level is equivalent to the preliminary design value. Theoretical results of waveheight in the north direction are greater than the designed values. The measured minimum elevation in both wharf sections and other CDP ones are lower than the evaluation values considering the wave run-up impact, which carries some risks. Some requisite measures should be immediately adopted to deduct MD risk.

Based on the topographical data of Liaohe Estuary in recent 50 years, the subaqueous delta evolution of Liaohe Estuary was studied by using GIS methods. The research results are showed as follows:The outer edge of the subaqueous delta of Liaohe Estuary(the western and southern edges of Geligangzi Shoal, the western and southern edges of Xitan Shoal) experienced a relatively erosion progress and the eastern edges of Geligangzi Shoal experienced a accumulation progress and the eastern head of the southern part of Geligangzi Shoal had moved northward and eastward.The Nearshore Shoal between the two river mouths experienced a process from accumulation to stability, and the shoal had eroded partially north of East Trough. Because of Geligangzi Shoal moving eastward, East Trough at east of Geligangzi Shoal had became narrow, and the deep water between Geligangzi Shoal and Xitan Shoal appeared a trend of widening and becoming shallow. The decrease of incoming sediments from Liaohe River was the main cause for the erosion of the outer edges of the subaqueous delta. The erosive sediment transport up to the estuary under the action of wave and flow was the main cause for the siltation of east edge of Geligangzi Shoal and East Trough became shallow and narrow. The impact of the artificial reclamation of the nearshore beach on the evolution of the underwater delta was worthy of attention.

When the submarine cable passes through the hard bottom seabed, covering the concrete interlocking mattress can effectively protect it. According to the measured hydrological data in the sea area of the state grid corporation of 500 kV submarine cable project, two methods were used to study the stability of the concrete interlocking mattress under the extreme flow. Based on function analysis of the mechanical balance, it is found that when the bottom length of the concrete block is fixed, there is an extreme height. At this time the concrete block laid on seabed is the most stable, and also the flow velocity that can be resisted is the largest. Through numerical simulation, the three-dimensional flow characteristics of concrete interlocking mattress in current were studied. After comparing the force situation of different shape concrete blocks, it is found that when the edge of the concrete block is rounded, the flow structure around the edge can be changed, and the stability of the concrete block can be strengthened in general. Although the current velocity in the sea area of the state grid corporation of 500 kV submarine cable project is large, the conventional size of 0.4 m×0.4 m×0.3 m blocks can resist the impact of the current and protect the submarine cable.

Due to the necessity of construction, it is proposed to adjust the dike line of Jiuxi reach of Qiantang River. Jiuxi is one of the well-known tidal bore scenic spots of Qiantang River, and the tidal bore is an important natural landscape resource in this reach. In order to mitigate the impact of dike line adjustment on the tidal bore landscape, a three-dimensional SCHISM tidal bore model based on finite element/finite volume method was established, which reproduced the phenomenon of Jiuxi tidal bore. Three comprehensive evaluation indexes were put forward, namely, the height of tidal bore, the length of shoreline with significant bore height and the area with significant height of bore, and the impact of levee adjustment on tidal bore was evaluated. The study has reference significance for other projects to evaluate the tidal bore landscape of Qiantang River.

The northern South China Sea, located in tropical and subtropical areas,is one of the important fishing grounds along the coast of China and has abundant fishery resources. Phytoplankton are the basic link in the marine food chain, change in their community structure will directly or indirectly influence fishery resources. According to the survey data in May 2015, the structure characteristics of phytoplankton community and its relationship with environmental factors were analyzed. The results showed that a total of 378 species (excluding the unidentified species) belonging to 4 phyla were identified, including 209 species of diatoms, 157 species of dinoflagellate, 9 species of cyanobacteria and 3 species of chromophyte. The dominant species were Proboscia alata,Proboscia alata f. gracillima,Thalassiothrix frauenfeldii,Pseudo-nitzschia pungens,Eucompia zoodiacus and Chaetoceros lorenzianus.The dominant species differed obviously among sections, only Thalassiothrixfrauenfeldii was dominant along four sections. The phytoplankton abundance ranged from 0.63×10⁴ cells/m³ to 1 430.04×10⁴ cells/m³, with an average of 76.20×10⁴ cells/m³. Diatoms were overwhelmingly dominant in phytoplankton community, which abundance ranged from 0.3×10⁴ cells/m³ to 1 420.39×10⁴ cells/m³, with an average of 72.89×10⁴ cells/m³, accounting for 95.66%. Dinoflagellate abundance ranged from 0.03×10⁴ cells/m³ to 23.78×10⁴ cells/m³, with an average of 2.71×10⁴ cells/m³, accounting for 3.56%. Shantou section (H) had the highest abundance, with an average of 250.01×10⁴ cells/m³, followed by Zhanjiang section (D), with an average of 99.48×10⁴ cells/m³. The low abundances were found in the Pearl River Estuary (F), Shanwei (G) and Yangjiang (E) sections, with an average of 11.67×10⁴ cells/m³, 10.61×10⁴ cells/m³ and 9.23×10⁴ cells/m³, respectively. High-abundance areas were mainly occurred at inshore stations in the Shantou (H) and Zhanjiang (D) sections. Overall, the phytoplankton Shannon-Wiener diversity index was high, ranged from 1.06 to 5.56,with an average of 3.99, indicating that the community structure of phytoplankton was relatively stable in the northern South China Sea in spring. Redundancy analysis showed that temperature, salinity and phosphate were the main environmental factors associated with the phytoplankton community structure in the northern South China Sea. Spearman's rank correlation analysis showed that abundances of phytoplankton, diatoms and dinoflagellates were negatively correlated with temperature. The results showed that the species composition, abundance distribution and dominant species composition of phytoplankton were different from section to section. Phytoplankton distribution was characterized by high nearshore and low offshore,and water temperature and salinity were the main environmental factors affecting its distribution in the continental shelf of the northern South China Sea in spring.