Responses of estuarine salinity and transport processes to sea level rise in the Zhujiang(Pearl River) Estuary

Understanding the changes of hydrodynamics in estuaries with respect to magnitude of sea level rise is important to understand the changes of transport process. Based on prediction of sea level rise over the 21st century, the Zhujiang（Pearl River） Estuary was chosen as a prototype to study the responses of the estuary to potential sea level rise. The numerical model results show that the average salt content, saltwater intrusion distance, and stratification will increase as the sea level rises. The changes of these parameters have obvious seasonal variations. The salt content in the Lingdingyang shows more increase in April and October（the transition periods）. The saltwater intrusion distance has larger increase during the low-flow periods than during the highflow periods in the Lingdingyang. The result is just the opposite in Modaomen. The stratification and its increase are larger during the low-flow periods than during the high-flow periods in Lingdingyang. The response results of transport processes to sea level rise demonstrate that：（1） The time of vertical transport has pronounced increase.The increased tidal range and currents would reinforce the vertical mixing, but the increased stratification would weaken the vertical exchange. The impact of stratification changes overwhelms the impact of tidal changes. It would be more difficult for the surface water to reach the bottom.（2） The lengthways estuarine circulation would be strengthened. Both the offshore surface residual current and inshore bottom residual current will be enhanced.The whole meridional resident flow along the transect of the Lingdingyang would be weakened. These phenomena are caused by the decrease of water surface slope（WWS） and the change of static pressure with the increase of water depth under sea level rise.

The relationship between tidal current field and sediment transport in the Huanghai Sea and the Bohai Sea

-Based on a two-dimensional numerical M2 tidal model of the Huanghai and Bohai Seas, sediment transport of particles with different sizes in the computational area is given. It is concluded that tidal currents play an important role in sediment transport and deposition in the Huanghai and Bohai Seas.

Low-frequency variability of the shallow meridional overturning circulation in the South China Sea

The low-frequency variability of the shallow meridional overturning circulation（MOC） in the South China Sea（SCS） is investigated using a Simple Ocean Data Assimilation（SODA） product for the period of 1900-2010. A dynamical decomposition method is used in which the MOC is decomposed into the Ekman, external mode, and vertical shear components. Results show that all the three dynamical components contribute to the formation of the seasonal and annual mean shallow MOC in the SCS. The shallow MOC in the SCS consists of two cells： a clockwise cell in the south and an anticlockwise cell in the north; the former is controlled by the Ekman flow and the latter is dominated by the external barotropic flow, with the contribution of the vertical shear being to reduce the magnitude of both cells. In addition, the strength of the MOC in the south is found to have a falling trend over the past century, due mainly to a weakening of the Luzon Strait transport（LST） that reduces the transport of the external component. Further analysis suggests that the weakening of the LST is closely related to a weakening of the westerly wind anomalies over the equatorial Pacific, which leads to a southward shift of the North Equatorial Current（NEC） bifurcation and thus a stronger transport of the Kuroshio east of Luzon.

Spatiotemporal characteristics of sea ice transport in the Baffin Bay and its association with atmospheric variability

Sea ice export through the Baffin Bay plays a vital role in modulating the sea ice cover variability in the Labrador Sea.In this study,satellite-derived sea ice products are used to obtain the sea ice area flux(SIAF)through the three passages in the Baffin Bay(referred to as A,B,and C for the north,middle,and south passages,respectively).The spatial variability of the monthly sea ice drift in the Baffin Bay is presented.The interannual variability and trends in SIAF via the three passages are outlined.The connection to several large-scale atmospheric circulation modes is assessed.Over the period of 1988-2015,the average annual(October to the following September)SIAF amounts to 555×10^(3) km^(2),642×10^(3) km^(2),and 551×10^(3) km^(2) through Passages A,B,and C,respectively.These quantities are less than that observed through the Fram Strait(FS,707×10^(3) km^(2))of the corresponding period.The positive trends in annual SIAF,on the order of 53.1×10^(3) km^(2)/(10 a)and 43.2×10^(3) km^(2)/(10 a)(significant at the 95%confidence level),are identified at Passages A and B,respectively.The trend of the south passage(C),however,is slightly negative(-13.3×10^(3) km^(2)/(10 a),not statistically significant).The positive trends in annual SIAF through the Passages A and B are primarily attributable to the significant increases after 2000.The connection between the Baffin Bay sea ice export and the North Atlantic Oscillation is not significant over the studied period.By contrast,the association with the cross-gate sea level pressure difference is robust in the Baffin Bay(R equals 0.69 to 0.71,depending on the passages considered),but relatively weaker than that over FS(R=0.74).

Estimation of water volume transports through the main straits of the East China Sea

The structure of current speed and the variability of volume transports of the Kuroshio in the Tokara-kaikyo and Osumi-kaikyo are discussed on the basis of data of KER in the period from 1977 to 1984. The average geostrophic transport through these two straits is estimated to be 24. 5×106 m3/s and only 1/12 of the transport is through the Osumi-kaiky5. Countercurrents on both sides of the Kuroshio trunk are observed in the Tokara-kaikyo. Calculation indicates that the average geostrophic current speed is less than the GEK current speed, systematically. On the basis of the current measurements, the northward transports through the Taiwan Strait in winter and summer are estimated to be 1. 05×106and 3. 16×106m3/s, respectively. From Chu's data (1976) the average transport of the Kuroshio flowing into the East China Sea passing through the passage east of Taiwan is about 29. 3×106m3/s. From Miita and Ogawa's data (1984) the average transport through the Tsushima-kaikyo is 3. 6×106m3/s. Thus the volume transports through the above four straits are roughly in balance, the total outflowing transport is slightly larger than the total inflowing transport. The possible reasons resulting in the difference of transports are also discussed.

Quantitative evaluation of air pollution in transport strategic environmental assessment:a case study based on uncertainty analysis and graphic information system technology

Although the impact of road transport on urban air quality has achieved a high profile in China,still greater attention is required as it has not yet been considered fully even in relation to the road network linking cities and urban areas. Strategic environmental assessment (SEA) is a systematic and comprehensive process for evaluating the environmental impacts of a policy,plan or program in publicly accountable decision-making. Air pollution has been recognized as a significant issue in most transport SEA practices. The Strategic Environmental Assessment of the Hubei Road Network Plan (2002-2020) (HRNP) was introduced as one of the World Bank's pilot SEA projects. An effective framework was developed to investigate the functional relationship between the road network and its potential air pollutant emissions. In this study,two indicators were identified:emission intensity/ inventory of pollutants and the spatial distribution of the most polluted areas. Because strategic actions are inherently nebulous and data quality is often disappointing,three alternative scenarios were employed to address uncertainties and data/scale issues. Calculations were made using emission models and results were analyzed with the help of statistical tools and the geographic information system (GIS). The results from the project implementation and the feedback from the World Bank have both shown that the proposed framework is effective in the transport SEA process.