Coastal Current Systems and the Movement and Expansion of Suspended Sediment from Changjiang River Estuary

This paper, with NOAA/AHHRR data for 2 years, discusses the expanding path and extent of suspended sediment from the Changjiang River, and the relationship between the suspended sediment expanding and coastal current systems by analyzing the thermal infrared imagery with the sediment imagery, which is acquired by correlating the atmosphere corrected AVHRR imagery with in-situ suspended sediment data. The coastal current systems affecting the sediment dispersal mainly include： the Taiwan Warm Current （TWC）, the Huanghai Sea Mixed Water （HSMW）, North Jiangsu near-shore current, and Zhejiang near-shore current etc. In winter, the current systems are stable. Their distribution affects the sediment from north Jiangsu expanding toward the Changjiang estuary in some degree .The front between Zhejiang coastal current and TWC blocks the expanding of sediment toward the sea. In the flood season, apart from the limitation by coastal current systems, the spatial and temporal distribution of suspended sediment is also affected by the runoff, which shows as the jet stream and fresh water. Spring and autumn are the transitional periods of the forming of expanding patterns of flood season and winter respectively. In addition, the re-suspended sediment caused by the wind wave may make the expanding range of near-shore sediment larger.

The Variability of Partial Pressure of Carbon Dioxide (pCO2) in a River-Influenced Coastal Upwelling System: A Case of the Northeast Pacific Coast

The Northeast Pacific coastal ocean, as a typical river-influenced coastal upwelling system, is characterized by significant variability of sea surface partial pressure of carbon dioxide (pCO2, <200 to >1000 μatm). This study reviewed the pCO2 variability and its underlying controlling mechanism in this highly dynamic region by bringing together previous scientific findings and historical data. The large pCO2 variability reflects the complex interactions between physical processes (riverine input and coastal upwelling) and the biological responses to the nutrient transportation associated with these physical processes, while temperature and air-sea gas exchange play a minor role in affecting pCO2. Both the river water and upwelled subsurface water are characterized by higher concentrations of pCO2 and nutrients when compared to the coastal surface water. The presence of high chlorophyll-a and low pCO2 in river plumes and areas adjacent to upwelling locations showed the intense biological CO2 uptake. The influences of riverine input and coastal upwelling thus mainly depend on the competing effect of high background pCO2 of river water and upwelled subsurface water vs. the biological dropdown of pCO2 resulting from the riverine- and upwelling-associated nutrient supplies. The strength of upwelling-favorable wind plays an important role in the pCO2 variability by affecting the intensity of coastal upwelling, with stronger wind speed causing more intense upwelling. The long-term pCO2 increasing rate in the Northeast Pacific coast is observed to be lower than that in the North Pacific open ocean.