Annual Variability in Marine Particulate Trace Elements During the Hawaii Aerosol Time‐Series

Abstract The Hawaii Aerosol Time‐Series (HATS) was a coordinated effort to simultaneously monitor atmospheric and water column dust dynamics in the North Pacific Subtropical Gyre. Throughout 2022 and 2023, HATS measured the composition of water column particles and made complementary measurements of aerosol chemistry and deposition fluxes. Here we report the inventories, elemental composition, dust‐relative residence times, and internal dynamics of size‐fractionated marine particles at Station ALOHA from four expeditions between September 2022 and August 2023. Mixed layer inventories of lithogenic particulate elements (Al, Fe, and Ti) varied by factors of 9 and 5 in small (0.2–51 μm) and large (>51 μm) particles, respectively, and by factors of 3 and 2 through 300 m depth; much less than the factor of 25–42 variations of these elements observed in aerosols. Mixed layer residence times of small lithogenic particles, relative to dust fluxes, ranged from <1 day to 12 days and from 1 week to 6 months through 300 m, demonstrating persistent rapid packaging into large particles near the surface. Fractional lability of Fe and Al in marine particles ranged from 6% to 89% and 22%–80%, respectively, in the upper 200 m, with Fe showing greater variability across size fractions. Scavenged Fe was more abundant below 200 m than at the surface, coincident with longer particulate residence times and larger lithogenic inventories in the upper mesopelagic. Ti‐normalized lithogenic ratios of marine particles were mostly lower than the aerosol time‐series, suggesting loss of Fe and Al from minerals post‐deposition and/or unquantified lateral inputs of Ti‐rich material.