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Abstract Atmospheric deposition of aerosols transported from the continents is an important source of nutrient and pollutant trace elements (TEs) to the surface ocean. During the U.S. GEOTRACES GP15 Pacific Meridional Transect between Alaska and Tahiti (September–November 2018), aerosol samples were collected over the North Pacific and equatorial Pacific and analyzed for a suite of TEs, including Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb. Sampling coincided with the annual minimum in dust transport from Asia, providing an opportunity to quantify aerosol TE concentrations and deposition during the low dust season. Nevertheless, peak concentrations of “crustal” TEs measured at ∼40–50°N (∼145 pmol/m3Fe) were associated with transport from northern Asia, with lower concentrations (36 ± 14 pmol/m3Fe) over the equatorial Pacific. Relative to crustal abundances, equatorial Pacific aerosols typically had higher TE enrichment factors than North Pacific aerosols. In contrast, aerosol V was more enriched over the North Pacific, presumably due to greater supply to this region from oil combustion products. Bulk deposition velocity (Vbulk) was calculated along the transect using the surface ocean decay inventory of the naturally occurring radionuclide,7Be, and aerosol7Be activity. Deposition velocities were significantly higher (4,570 ± 1,146 m/d) within the Intertropical Convergence Zone than elsewhere (1,764 ± 261 m/d) due to aerosol scavenging by intense rainfall. Daily deposition fluxes to the central Pacific during the low dust season were calculated using Vbulkand aerosol TE concentration data, with Fe fluxes ranging from 19 to 258 nmol/m2/d.
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Concentrations, Solubility, and Deposition Fluxes of Aerosol Trace Elements in the Central Arctic During Winter and Spring: Results From the MOSAiC Expedition
Abstract Atmospheric deposition is an important pathway for delivering micronutrient and pollutant trace elements (TEs) to the surface ocean. In the central Arctic, much of this supply takes place onto sea ice during winter, before eventual delivery to the ocean during summertime melt. However, the seasonality of aerosol TE loading, solubility, and deposition flux are poorly studied over the Arctic Ocean, due to the difficulties of wintertime sampling. As part of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, aerosols collected during winter and spring (December–May) were analyzed for soluble, labile, and total TE concentrations. Despite low dust loading, mineral aerosol accounted for most of the variation in total Fe, Al, Ti, V, Mn, and Th concentrations. In contrast, soluble TE concentrations were more closely linked to non‐sea‐salt sulfate, and Fe solubility was significantly higher during Arctic winter (median = 6.5%) than spring (1.9%), suggesting an influence from Arctic haze. Beryllium‐7 data were used to calculate an average bulk deposition velocity of 613 ± 153 m d−1over most of the study period, which was applied to calculate seasonal deposition fluxes of total, labile, and soluble TEs to the central Arctic. Total TE fluxes (173 ± 145 nmol m−2 d−1for Fe) agreed within a factor of two or three with earlier summertime estimates, with generally higher wintertime concentrations offset by a lower deposition velocity. Cumulative seasonal deposition of total, labile, and soluble Fe to the central Arctic Ocean was calculated at 25 ± 21, 5 ± 3, and 2 ± 2 μmol m−2, respectively.
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- Award ID(s):
- 1753423
- PAR ID:
- 10647197
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Global Biogeochemical Cycles
- Volume:
- 39
- Issue:
- 10
- ISSN:
- 0886-6236
- Format(s):
- Medium: X
- Associated Dataset(s):
- View Associated Dataset(s) >>
- Sponsoring Org:
- National Science Foundation
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