Influence of East Asian Continental Emissions on Marine Atmospheric Chemistry and Ocean Ecosystems in the Northwest Pacific

With the acceleration of global economic development and urbanization, the impacts of anthropogenic emissions on the Earth system have intensified. East Asia, as one of the most densely populated and economically active regions in the world, emits substantial amounts of particulate matter into the atmosphere. Influenced by the prevailing westerlies and the East Asian monsoon, these particles are transported downwind to the Northwest Pacific, exerting significant effects on marine atmospheric composition and ocean ecosystems in this region.

Focusing on key marine atmospheric nutrients including iron (Fe) and nitrogen (N), this study employs a multi-platform approach encompassing satellite remote sensing, in situ Argo floats, shipborne observations, and atmospheric chemical transport modeling to investigate the contribution of East Asian continental aerosol outflow to nutrient supply and the subsequent ocean response. A central highlight of this work is quantifying anthropogenic contributions to atmospheric Fe and N over the Northwest Pacific in recent years.

First, by integrating shipborne online measurements (2021–2022) of multiple atmospheric metals with a positive matrix factorization (PMF) model, we developed a high-time-resolution source apportionment framework for marine atmospheric metals including Fe. This approach provides the first observation-based quantification of contributions from several anthropogenic sources to marine atmospheric Fe and soluble Fe at hourly resolution. The results showed land anthropogenic emissions contributed substantially to atmospheric soluble Fe, accounting for 57% in the open Northwest Pacific during spring and increasing to 62% in summer. These results were further cross-validated against advanced Fe isotope–based source apportionment, yielding strong agreement (R² = 0.94).

Second, for atmospheric nitrogen, shipborne sampling combined with nitrogen isotope analysis revealed sharp spatial gradients in atmospheric nitrate concentrations and sources from the Chinese marginal seas to the open Northwest Pacific. Coupled with an atmospheric chemical transport model, we further quantified the flux and temporal variability of multiple nitrogen species transported from East Asia to the Northwest Pacific during 2005–2019 and assessed the response of marine atmospheric nitrogen deposition to emission reductions in recent years in East Asia. These findings provide novel insights into the important impacts of land-derived emissions on ocean ecosystems, particularly anthropogenic sources, in shaping biogeochemical processes in downwind oceanic regions and advance our understanding of land–ocean interactions under anthropogenic perturbations.