The Hawaii Dust Regime: Patterns and Variability in Aerosol Mineral Dust From MERRA-2 at Station ALOHA and the Hawaii Aerosol Time-Series

Abstract

The transport and delivery of low-abundance, bioactive trace elements to the surface ocean by aerosol mineral dust is a major planetary control over marine primary production and hence the global carbon cycle. Variations in the concentration of atmospheric dust have established links to global climate over geologic timescales and to regional biogeographic shifts over seasonal timescales. Constraining atmospheric dust variability is thus of high value to understanding oceanographic systems, especially vast, constitutively low-nutrient subtropical gyre ecosystems and high-nutrient/low-chlorophyll ecosystems where availability of the trace element iron is a dominant ecological control. Here we leverage the MERRA-2 reanalysis product to examine over four decades of surface-level atmospheric mineral dust concentrations in a domain of the subtropical North Pacific centered at Ocean Station ALOHA. This study region has been sampled regularly since the mid-1980s and was the site of the Hawaii Aerosol Time-Series (HATS) project in 2022–2023. Two unequal semi-annual periods of elevated dust evident in the long-term results are described and constrained. We look for evidence of shifts in total and seasonal atmospheric dust abundances or in the timing of the onset of the dominant spring/summer dusty period, finding year-to-year variations but little evidence for long-term trends. We observe significant but complex relationships between the Pacific Decadal Oscillation (PDO) index and both dust and precipitation. The 2022 calendar year was among the dustiest years for the study domain in the preceding two decades and, by contrast, 2023 exhibited a significant early spring lull in dust.