The source and accumulation of anthropogenic carbon in the U.S. East Coast.

Li, Xinyu; Wu, Zelun; Ouyang, Zhangxian; Cai, Wei-Jun · Sci Adv · 2024

Where this comes from

Abstract

The ocean has absorbed anthropogenic carbon dioxide (C<sub>anthro</sub>) from the atmosphere and played an important role in mitigating global warming. However, how much C<sub>anthro</sub> is accumulated in coastal oceans and where it comes from have rarely been addressed with observational data. Here, we use a high-quality carbonate dataset (1996-2018) in the U.S. East Coast to address these questions. Our work shows that the offshore slope waters have the highest C<sub>anthro</sub> accumulation changes (ΔC<sub>anthro</sub>) consistent with water mass age and properties. From offshore to nearshore, ΔC<sub>anthro</sub> decreases with salinity to near zero in the subsurface, indicating no net increase in the export of C<sub>anthro</sub> from estuaries and wetlands. Excesses over the conservative mixing baseline also reveal an uptake of C<sub>anthro</sub> from the atmosphere within the shelf. Our analysis suggests that the continental shelf exports most of its absorbed C<sub>anthro</sub> from the atmosphere to the open ocean and acts as an essential pathway for global ocean C<sub>anthro</sub> storage and acidification.