Spatiotemporal trends of aerosol provenance and trace metal concentrations in the northeast subarctic Pacific Ocean
Bibliographic record
Abstract
The long-range transport of naturally occurring and anthropogenic aerosols originating from Asian deserts and megacities, respectively, can have a significant impact on the biogeochemical cycling of metals in the Fe-limited, high nutrient-low chlorophyll (HNLC) region of the northeast (NE) subarctic Pacific Ocean. These aerosols can deposit essential (e.g., Fe) and possibly toxic (e.g., Cu) metals to surface waters; thereby affecting micronutrients' bioavailability, and ultimately primary productivity in this region. In this study, we aimed to determine the provenance and spatiotemporal trends of metal inputs from Asian aerosol outflows into the NE Pacific Ocean. To do so, we collected aerosols on six research cruises along the Line P transect (GEOTRACES GPpr07), across three seasons in four years. Lead isotopic composition signatures were less radiogenic (high 208 Pb/ 206 Pb; low 206 Pb/ 207 Pb) in winter and spring compared to summer, signifying a greater anthropogenic Asian source in the cooler seasons. Furthermore, aerosol metal content also revealed seasonality. For example, aerosols collected in March 2022 (winter) contained higher concentrations of the lithogenic metals Al, Ti, Fe, Mn and Co, the anthropogenic metals Cu, Cd and Pb, as well as the mixed-source metals Ni and V, in comparison to May 2021 (spring) and August 2021 (summer). The estimated annual atmospheric flux of Fe and Zn accounted for 13–27 % and 6–10 %, respectively, of the total flux to the surface mixed layer (i.e., vertical mixing plus atmospheric flux) at Ocean Station Papa (50°N, 145°W), while that of Cu accounted for 95–99 %. This study provides the first insight into the seasonal patterns and geochemical characterizations of long-range transported Asian aerosols along the Line P transect. Anthropogenic activities will likely increase the input of aerosol-derived metals from distant Asian sources into the NE Pacific Ocean in the coming years, influencing biogeochemical cycles in this Fe-limited oceanic region. • The role of Asian-derived aerosols in the NE Pacific HNLC region was investigated. • Enhanced long-range transport of anthropogenic Asian aerosols in winter and spring. • Increased metal concentrations in late winter aerosols than summer. • Highly variable aerosol metal concentrations within short timeframes. • Aerosol inputs to surface waters are notable for lithogenic Fe and anthropogenic Cu.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".