Journal of Geoscience and Environment Protection | 2021
The Variability of Partial Pressure of Carbon Dioxide (pCO2) in a River-Influenced Coastal Upwelling System: A Case of the Northeast Pacific Coast
Abstract
The \nNortheast Pacific coastal ocean, as a typical river-influenced coastal \nupwelling system, is characterized by significant variability of sea surface \npartial pressure of carbon dioxide (pCO2, 1000 μatm). This \nstudy reviewed the pCO2 variability \nand its underlying controlling mechanism in this highly dynamic region by \nbringing together previous scientific findings and historical data. The large pCO2 variability reflects the complex interactions between physical processes \n(riverine input and coastal upwelling) and the biological responses to the nutrient transportation \nassociated with these physical processes, while temperature and air-sea \ngas exchange play a minor role in affecting pCO2. Both the \nriver water and upwelled subsurface water are characterized by higher \nconcentrations of pCO2 and nutrients when compared to the \ncoastal surface water. The presence of high chlorophyll-a and low pCO2 in river plumes and areas adjacent to upwelling locations showed the intense \nbiological CO2 uptake. The influences of riverine input and coastal \nupwelling 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 \nstrength of upwelling-favorable wind plays an important role in the pCO2 variability by affecting the intensity of coastal upwelling, with stronger wind \nspeed causing more intense upwelling. The long-term pCO2 increasing rate in the Northeast Pacific coast is observed to be lower than \nthat in the North Pacific open ocean.