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 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
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 variability 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 nearly
semi-annual dust pulses evident in the long-term data are described and
constrained. We look for evidence of shifts in total and seasonal
atmospheric dust abundances and in the onset timing of the dominant
spring/summer pulse, finding year-to-year variations but little evidence
for long-term trends. We observe significant and complex monthly
relationships between the Pacific Decadal Oscillation (PDO) index and
both dust and precipitation, offering new insights into the role of
timing for increased or diminished dust delivery. We observe that 2022
was among the dustiest years for the study domain in the preceding two
decades and, by contrast, that 2023 exhibited a significant early-spring
lull in dust.