Seasonal Variations in Aerosol Trace Element Source Contributions and Deposition Fluxes to the North Pacific Subtropical Gyre

Abstract

Trace elements deposited in the marine environment affect ocean biogeochemistry in numerous, complex ways. This study quantifies seasonal aerosol trace element (TE) fluxes and evaluates their variability and potential sources over a 2‐year period in the North Pacific subtropical gyre (NPSG). We established the Hawaii Aerosol Time Series (HATS), which includes weekly integrated total suspended aerosol particle collections alongside sampling the cosmogenic radionuclide 7 Be. As a conservative tracer in the surface ocean, 7 Be can be used to estimate seasonal depositional fluxes of a suite of trace elements (Al, Co, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V, and Zn). An annually recurring bimodal pattern with two periods of increased dust deposition on the NPSG was observed in the spring and late summer/fall. The transport of Asian dust in the spring dominates the annual aerosol loading to the NPSG, with an average Fe flux of 2,312 nmol/m 2 /d in 2022 and 1680 nmol/m 2 /d in 2023. Changing molar ratios of Al:Ti indicate varying influence of aerosol sources over the year, particularly during the two periods of enhanced atmospheric loading. In the late summer and fall, local Hawaiian inputs may contribute important trace elements, such as Fe, Mn, and Co to the surface ocean. These flux patterns have important implications for surface ocean trace element availability and may influence microbial nutrient limitation, particularly for nitrogen‐fixing organisms. The HATS dataset is a novel contribution to TE studies in the region, providing a valuable framework for understanding atmospheric inputs to the oligotrophic ocean and their biogeochemical impacts.