Marsh-Dominated Ocean Margins as a Source of CO2 to the Atmosphere and Open Oceans: A Field Study in the U.S. Southeastern Continental Shelf

最近对几个位于中高纬度地区的大型大陆架的研究表明，大气到海洋的二氧化碳转移显著。据推测，被吸收的二氧化碳被转移到开阔的海洋中。如果这一结论适用于全球，那么这样一个大陆架二氧化碳汇将对全球碳循环的研究非常重要。在这个项目中，乔治亚大学的研究人员将通过量化低至中纬度海洋边缘的海气二氧化碳通量来验证这一假设，美国东南大陆架（也称为南大西洋湾，SAB），那里的初步证据表明相反的（海气）二氧化碳通量。研究人员假设，SAB是向大气和开放海洋排放二氧化碳的来源，而这种二氧化碳的释放是由潮间带盐沼输出的有机碳（OC）的呼吸作用驱动的。表层二氧化碳分压和水柱总溶解无机碳（DIC）和碱度（Alk）的大陆架分布将通过覆盖整个南极大陆架的四个跨大陆架样带和一个沿岸样带以及五次季度巡航来确定。DIC向海输出通量将根据一个区域综合的超额DIC库存和由淡水平衡决定的陆架水停留时间来估计。在这一地区，流向公海的DIC通量预计将远远高于河流通量。以前很少尝试同时量化海气CO2通量和向公海输出的DIC，这将大大提高我们对海洋边缘在全球海洋碳循环中所起作用的理解。除了确定整个向海DIC通量外，该小组还将利用最近发表的SAB三维气候学模式和该地区正在进行的其他数值模式活动，更好地了解跨大陆架和沿岸流动携带的DIC通量的相对重要性。采用类似的方法，还将估算Alk和溶解有机碳的向海通量。更广泛的影响。该项目的结果有望提高我们对大气中人为二氧化碳命运的理解和预测能力。该项目还将以一些重要的方式促进涉及研究生、本科生和高中生的教学、培训和学习。

ABSTRACTOCE-0425153Recent studies in several large continental shelves located in mid-to-high latitude areas indicate significant air-to-sea CO2 transfer. Presumably the absorbed CO2 is transferred into the open ocean. If this conclusion is globally applicable, such a continental shelf CO2 sink would be very important in the study of global carbon cycling. In this project, researchers at the University of Georgia will test this hypothesis by quantifying air-sea CO2 fluxes in a low-to-mid latitude ocean margin, the U.S. Southeastern Continental Shelf (also known as the South Atlantic Bight, SAB), where preliminary evidence indicates an opposite (sea-to-air) CO2 flux. The researchers hypothesize that the SAB is a source of CO2 to the atmosphere and to the open ocean and that this CO2-release is driven by the respiration of organic carbon (OC) exported from intertidal salt marshes. Shelf-wide distributions of surface pCO2 and water column total dissolved inorganic carbon (DIC) and alkalinity (Alk) will be determined with four cross-shelf transects and one alongshore transect covering the entire SAB and through five quarterly cruises. The seaward export fluxes of DIC will be estimated based on an area-integrated excess DIC inventory and the shelf water residence time determined by freshwater balance. This DIC flux to the open ocean is expected to be much higher than the riverine flux in this area. The simultaneous quantification of air-sea CO2 flux and DIC export to the open ocean, which has rarely been attempted before, will significantly improve our understanding of the role that ocean margins play in the global ocean carbon cycle. In addition to the determination of overall seaward DIC flux, the team will also seek a better understanding of the relative importance of DIC fluxes carried by cross-shelf and alongshore flows by taking advantage of a recently published SAB 3-dimensional climatology model and other ongoing numerical model activities in this region. In a similar approach, seaward fluxes of Alk and dissolved organic carbon will also be estimated. Broader Impacts. The results of this project are expected to enhance our understanding and ability to predict the fate of anthropogenic CO2 in the atmosphere. This project will also promote teaching, training and learning in a number of important ways that involve graduate, undergraduate and high school students.