东海海—气界面二氧化碳通量的季节变化与控制因素研究进展

Advances of Seasonal Variations and Controlling Factors of the Air-Sea CO_2 Flux in the East China Sea

通过对东海海—气界面二氧化碳(CO2)交换有关研究的总结,剖析了东海表层海水CO2分压(pCO2)的区域分布特征,探讨了海—气界面CO2通量(FCO2)的季节变化规律,诠释了影响海—气界面CO2转移的主要因素。结果表明,东海表层海水pCO2的区域分布具有明显的季节变化,可将其分为冬季、夏季、过渡季节(春季、秋季)3个时段。冬季西部近岸海域由于水体垂直交换强烈,造成表层水体pCO2较高,而中、东部陆架海域由于浮游生物的光合作用使得pCO2较低。夏季近岸河口海域由于陆源输入的影响导致pCO2较高,中、东部陆架海域受温跃层、长江冲淡水、浮游植物的综合作用pCO2较低。春季、秋季为过渡时段,表层海水pCO2分布变化剧烈,受控因素较为复杂。东海全年表现为大气CO2的净汇,其中冬、春、夏为碳汇,其海—气界面FCO2分别为(-6.68±6.93),(-4.94±0.80),(-3.67±1.09)mmol/(m2·d)。秋季表现为碳源,通量约为(1.50±8.37)mmol/(m2·d)。东海全年平均通量约为-3.16 mmol/(m2·d),共可吸收CO2约为6.92×106t C/a。不同季节海—气界面FCO2的年际变化凸显了人为因素的影响,近海富营养化加剧,三峡工程的运行都可能是造成东海冬季碳汇量减少、秋季碳源/汇格局转变的原因。

Spatial variations of the CO2 partial pressure（pCO2） in surface water,seasonal variations of the air-sea CO2 exchange flux（FCO2）,and major controlling factors of the CO2 transfer were reviewed based on the summary of CO2 exchange in the East China Sea（ECS）.Spatial distribution of pCO2 in the ECS underwent three different phases： the winter phase,the summer phase,and the transition phase（spring and autumn）.The western coastal area acted as CO2 source on account of vertical convection during the winter phase,whereas the shelf region acted as CO2 sink because of the phytoplankton activity.Estuary in the shallower shelf possessed high pCO2 for terrigenous input in the summer phase while the major shelf had low pCO2 under the comprehensive function of thermocline,Changjiang diluted water,and photosynthesis.During the transition phase in spring and autumn,the distribution of pCO2 varied dramatically and got complex controlling factors.The winter,spring,and summer could absorb atmospheric CO2 with the flux for（-6.68±6.93）,（-4.94±0.80）,（-3.67±1.09） mmol/（m2·d）,respectively,whereas the autumn could release CO2 with the flux for（2.64±7.06） mmol/（m2·d）.The ECS serves as a carbon sink with the annual air-sea CO2 flux for-3.16 mmol/（m2·d）,which equals to 6.92×106t C/a.Anthropogenic activities and the aggregative of eutrophication were the principal reason for the annual variation of CO2 flux probably.