2017年春季长江口-东海连续体pCO_(2)的空间分布特征及其控制因素

Distributions and controlling factors of pCO_(2) in the Changjiang(Yangtze River)Estuary-East China Sea continuum in spring of 2017

厘清河口-陆架连续体的碳源/汇机制是认识海洋在“碳中和”中作用的重要基础。本研究基于2017年春季长江口-东海的走航CO_(2)分压(pCO_(2))及温、盐等资料,分区域阐述春季长江口-东海连续体pCO_(2)的空间分布格局,半定量解析水团分配、有机质生产及降解等过程对pCO_(2)的控制作用。结果表明:水团来源是决定春季长江口-东海连续体pCO_(2)分布及碳源/汇格局的主要因素,而有机质生产或者降解可强烈影响长江口-东海连续体碳源/汇格局。春季长江口门及浙江沿岸受长江径流影响而具有较高的pCO_(2),碳源强度可达5.36 mmol·m^(-2)·d^(-1);研究区域北部和东部分别受冲淡水及黑潮表层水的影响,表现为大气碳汇,北部碳汇强度为^(-1)5.44 mmol·m^(-2)·d^(-1)。2017年春季研究区域平均碳通量为-6.73 mmol·m^(-2)·d^(-1)。端元混合模型结果表明陆源有机质降解导致河口pCO_(2)增加了约200μatm,促使春季河口由大气CO_(2)的弱汇转变为碳源;陆架区域在仅考虑水团分配下同样为碳汇,而藻华过程进一步降低了pCO_(2)(下降144μatm),增强了其碳汇能力。

Controlling mechanism of air-sea carbon flux in estuary-shelf continuum is important for understanding the role of ocean in“carbon neutrality”goal of China.Based on underway sea surface partial pressure of CO_(2)(pCO_(2)),temperature and salinity in the Changjiang(Yangtze River)Estuary-East China Sea in spring of 2017,the spatial variations of pCO_(2)in four domains of the Changjiang Estuary-East China Sea continuum were presented.The roles of water mass sources,organic matter production and decomposition in controlling pCO_(2)were discussed semi-quantitatively.The results indicated that water mass sources were key factors in determining pCO_(2)and air-sea carbon flux in the Changjiang Estuary-East China Sea continuum.In addition,production and decomposition of organic matters also influenced pCO_(2)significantly.Influenced by Changjiang discharge,surface waters in the inner Changjiang Estuary and Zhejiang coast had relatively high pCO_(2),served as source of CO_(2)to atmosphere,with magnitude of 5.36 mmol·m^(-2)·d^(-1).The north and east of study area were influenced by the Changjiang Diluted Water,and Kuroshio Surface Water,respectively.While,they were both carbon sinks with magnitude of -15.44 mmol·m^(-2)·d^(-1) in the north study area.The average air-sea carbon flux in study area in spring of 2017 was-6.73 mmol·m^(-2)·d^(-1).End-member mixing model revealed that decomposition of organic matter increased pCO_(2)of the inner estuary by about 200μatm,which transferred the inner estuary from carbon sink to carbon source in spring;the shelf waters were carbon sink if water mass sources were considered only,while biological production decreased pCO_(2)(decreased 144μatm)further,and enhanced the carbon sink.