Classification and 3-D distribution of upper layer water masses in the northern South China Sea

Using the fuzzy cluster analysis and the temperature-salinity(T-S) similarity number analysis of cruise conductivity-temperature-depth(CTD) data in the upper layer(0–300 m) of the northern South China Sea(NSCS), we classify the upper layer water of the NSCS into six water masses: diluted water(D), surface water(SS),the SCS subsurface water mass(U_S), the Pacific Ocean subsurface water mass(U_P), surface-subsurface mixed water(SU) and subsurface-intermediate mixed water(UI). A new stacked stereogram is used to illustrate the water mass distribution, and to examine the source and the distribution of U_P, combining with the sea surface height data and geostrophic current field. The results show that water mass U_P exists in all four seasons with the maximum range in spring and the minimum range in summer. In spring and winter, the U_P intrudes into the Luzon Strait and the southwest of Taiwan Island via the northern Luzon Strait in the form of nonlinear Rossby eddies, and forms a high temperature and high salinity zone east of the Dongsha Islands. In summer, the U_P is sporadically distributed in the study area. In autumn, the U_P is located in the upper 200 m layer east of Hainan Island.

Wintertime Guangdong coastal currents successfully captured by cheap GPS drifters

This study introduces a type of self-developed, GPS-based, simple and cheap Surface Current Experiment(SUCE)drifters designated for observing surface coastal currents. By examining trajectories of six drifters deployed in the Daya Bay and the drifter-derived velocities, we conclude that such drifters are generally capable of capturing the characteristics of wintertime surface coastal currents along the Guangdong coast.

Analysis of temperature inversion in the Zhujiang River Estuaryin July 2015

This study investigates the temperature inversion phenomenon in the Zhujiang(Pearl) River Estuary(ZRE) using hydrological data collected in a summer cruise during July 6–17, 2015. The results suggest that temperature inversion occurred primarily near the salinity front, with an average temperature difference(ΔT) of 0.42°C between the inversion layer and the underlying water. The inversion layer was approximately 4 m thick on average, with an upper boundary at a depth of 1–6 m and a lower boundary at a depth of 3–10 m. Different mechanisms and dynamic processes were responsible for temperature inversion in different parts of the study area.(1) At the salinity front in the west of the ZRE, the measurements collected by CTD(conductivity,temperature, and depth) showed that the low-salinity water mass on the inner side of the front was approximately2°C cooler than the high-salinity water mass on the outer side. Temperature inversion occurred when the cooler low-salinity water overlapped the warmer high-salinity water near the front due to the driving force of the background flow.(2) Inversion layers occurred at the mouth of the Taiping waterway as a result of varying horizontal flow between two different water masses under the effects of tides and runoff.(3) To the southwest of Hong Kong, temperature inversion occurred due to the interaction of upwelling and the salinity front.

日本福岛核废水排海情景下海洋生态环境影响与应对

2011年3月11日,太平洋海底9级大地震产生的海啸引发日本福岛核事故[1].福岛核事故后,大量的放射性核素泄漏进入环境,并通过大气环流和海洋环流对全球许多地区造成一定的影响[2~6].福岛核事故后,日本制定了福岛核电站中长期退役计划(30~40年),开展受损反应堆退役与周边环境修复措施,其中核废水处理、核燃料移除、其他废物处理是中长期退役计划的三大关键环节[7].

Tide- and wind-driven variability of water level in Sansha Bay, Fujian, China

This study analyzes water-level variability in Sansha Bay and its adjacent waters near Fujian, China, using water-level data observed from seven stations along the coast and wind data observed from a moored buoy near Mazu Island. At super-to near-inertial frequencies, tides dominated the water-level variations, mainly characterized by semi-diurnal （prmafily M2, S2, and N2） and diurnal tides （primarily Kb O1）. The correlation coefficients between residual （non-tidal） water-level time series and the observed wind-stress time series exceeded 0.78 at all stations, hinting that the wind acting on the study region was another factor modulating the water-level variability. A cross-wavelet and wavelet-coherence analysis further indicated that （i） the residual water level at each station was more coherent and out-of-phase with the alongshore winds mostly at sub-inertial time scales associated with synoptic weather changes; and （ii） the residual water-level difference between the outer and inner bay was more coherent with the cross-shore winds at discrete narrow frequency bands, with the wind leading by a certain phase. The analysis also implied that the monsoon relaxation period was more favorable for the formation of the land-sea breeze, modulating the residual water-level difference.

Surface currents measured by GPS drifters in Daya Bay and along the eastern Guangdong coast

GPS-based surface drifters were used to investigate the surface currents in Daya Bay and along the eastern Guangdong coast in China.Surface current vectors were measured based on the GPS location and corresponding time information sent by drifters through the mobile phone network.The analysis of data from 120 drifters,deployed in late spring 2018 in the case-study region,shows that the drifters are generally capable of capturing the surface(tidal and residual)currents.The drifter trajectories suggest an anticlockwise surface current inside Daya Bay and a north-eastward current along the eastern Guangdong coast,where the coastal current along the eastern Guangdong coast is faster than that inside Daya Bay.The surface currents in the investigated region follow an irregular semidiurnal cycle due to the influence of the tidal current,while the currents inside Daya Bay are strongly affected by the topography.According to the harmonic analysis,an irregular semidiurnal type of tidal current is evident at a study grid inside Daya Bay,with an Eulerian residual current speed of 9.0 cm/s and a direction of 276°.The Lagrangian residual current outside Daya Bay moves north-eastward with a mean speed of 22 cm/s along the eastern Guangdong coast,while the current inside Daya Bay moves northward to the bay head with a mean speed of about 8.0 cm/s,which agrees well with the one reported in other literatures.