Numerical Simulation Study Of Surface Carbon Dioxide Partial Pressure And Carbon Dioxide Flux At The Sea-air Interface In The East China Sea

Since the industrial revolution,the concentration of CO₂ in the atmosphere has continued to rise.The ocean,as a weak alkali system,absorbs carbon dioxide from the atmosphere.However,the continental shelf sea is not only affected by the open sea,but also affected by terrestrial sources and human activities,leading to complex and variable biochemical activities.Therefore,whether a specific coastal ocean is a source or a sink of CO₂ is not straightforward to determine.Different shelf seas should be studied individually.The East China Sea is dominated by the continental shelf.Its nutrient sources are diverse,resulting in higher productivity.Therefore,studying the distribution of carbon parameters in the East China Sea has important scientific significance and social importance.Historical data indicate that the nutrients transported by the Changjiang River runoff have a significant impact on the East China Sea ecosystem and indirectly play an important role in the carbon cycle.But there are fewer studies on it on the interannual scale and seasonal scale.This paper mainly uses the simulation of a three-dimensional physical-biological coupled model from 1997 to 2016 to explore the distribution of p CO₂ and surface CO₂ flux,f CO_2,in the East China Sea.The diffusion pattern of fresh water from the Changjiang River was also investigated.Changjiang diluted water spreads to the northeast in summer,and spreads southward along the coast in winter.The sea surface salinity will decrease.At the same time,the nutrients also carried by runoff are mainly distributed in the waters off the Changjiang estuary and its concentration decreases rapidly from west to east.The input of the Changjiang diluted water makes the ecological process more complicated.Both the surface p CO₂ and the sea-air f CO₂show obvious seasonal changes.In coastal waters,both p CO₂ and f CO₂ are high throughout the year,and then rapidly decreased from west to east.The research shows that surface p CO₂ is mainly affected by sea surface temperature(SST)and total carbon(TCO₂).Sea surface salinity(SSS)and total alkalinity(TALK)also have certain impact on p CO₂.Except for the high p CO₂ area near the Changjiang River Estuary,the surface p CO₂ is the lowest in spring,and the distribution is relatively uniform.In summer,affected by the Changjiang diluted water,p CO₂ is low in the central water and high in the open sea.The spatial distribution in autumn is similar to that of summer.In winter,except for the South Yellow Sea Coast,p CO₂ high in other sea areas.The distribution of f CO₂ is similar to p CO₂,but it is also affected by the 10m wind at the sea surface.In addition,due to the increase in atmospheric CO₂ concentration year by year,the absolute value of the difference between air and sea p CO₂ has increased,and the absolute value of f CO₂ has an increasing trend from 1997to 2016.The region of 28^oN-34^oN,119^oE-125^oE is selected to quantitatively calculate the average value of f CO₂.The result indicates that this area is a weak source of atmospheric CO₂throughout the year.More specifically,the area is a sink of atmospheric CO₂ during spring and summer,a source of atmospheric CO₂ during winter and autumn.