Dissolved iron (dFe) in boreal rivers may play an important role in primary production in high-latitude oceans. However, iron behavior in soils and dFe discharge mechanism from soil to the rivers are poorly understood. To better understand iron dynamics on the watershed scale, we observed the seasonal changes in dFe and Dissolved Organic Carbon (DOC) concentrations in the river as well as dFe concentration in soil pore waters in permafrost watershed from May to October. During snowmelt season, high dFe production (1.38–4.70 mg L${}^{-1}$) was observed in surface soil pore waters. Correspondingly, riverine dFe and DOC concentrations increased to 1.10 mg L${}^{-1}$ and 32.3 mg L${}^{-1}$, and both were the highest in the year. After spring floods, riverine dFe and DOC concentrations decreased to 0.15 mg L${}^{-1}$ and 7.62 mg L${}^{-1}$, and dFe concentration in surface soil pore waters also decreased to 0.20–1.28 mg L${}^{-1}$. In late July, riverine dFe and DOC concentrations increased to 0.33 mg L${}^{-1}$ and 23.6 mg L${}^{-1}$ in response to heavy rainfall. In August and September, considerable increases in dFe concentrations (2.00–6.90 mg L${}^{-1}$) were observed in subsurface soil pore waters, probably because infiltrated rainwater developed reducing conditions. This dFe production was confirmed widely in permafrost wetlands in valley areas. Overall, permafrost wetlands in valley areas are hotspots of dFe production and greatly contribute to dFe and DOC discharge to rivers, especially during snowmelt and rainy seasons.

Long-range transported dust across the North Pacific influences the climate by altering radiative forcing, affecting cloud properties as it acts as an ice nucleus, and impacting surface ocean biogeochemistry and carbon cycling through the supply of iron to the subarctic Pacific, a region characterized by high nutrients and low chlorophyll. Asian dust has for a long time been considered the dominant source of trans-Pacific dust; yet recent numerical simulations have revealed the frequent presence of Saharan dust in the upper troposphere over East Asia, highlighting its potential importance in North Pacific environments. However, owing to technical limitations in detecting diluted trans-Pacific Saharan dust and the lack of annual records identifying it over North America, the amount, frequency, and seasonality of Saharan dust transport across the North Pacific—as well as its climatic impact—remain unclear. To address this issue, we determined the provenance of trans-Pacific dust during 1985–1989 using scanning electron microscope–cathodoluminescence analysis of single quartz particles within an ice core from Mount Logan, southern Yukon Territory, Canada, combined with numerical simulations using the Integrated Massively Parallel Atmospheric Chemical Transport model. Ice core records showed that Asian dust is predominant during most seasons, whereas Saharan dust becomes dominant in winter. Numerical simulations showed that from spring to fall (1985–1989 averages), Asian dust accounted for 49–73% of the total deposition at Mount Logan, with notable Saharan contributions of 16–18%. In contrast, during winter, Saharan dust accounted for 44% of the deposition, primarily owing to a decrease in Asian dust deposition while Saharan dust deposition remained relatively high, thereby supporting the findings from Mount Logan records. Our results for the first time provide evidence of frequent transport of the Saharan dust across the North Pacific. Combined with the simulated vertical concentration of Saharan dust over the North Pacific, trans-Pacific Saharan dust may substantially influence high-altitude cirrus cloud formation and potentially affect North Pacific ecosystems through iron deposition. These findings indicate that Saharan dust over the North Pacific is considerably more significant than previously recognized.

The freshwater discharge from catchments along the Gulf of Alaska, termed Alaska discharge, is characterized by significant quantity and variability. Owing to subarctic climate and mountainous topography, the Alaska discharge variations may deliver possible impacts beyond the local hydrology. While short-term and local discharge estimation has been frequently realized, a longer time span and a discussion on cascading impacts remain unexplored in this area. In this study, the Alaska discharge during 1982–2022 is estimated using the Soil and Water Assessment Tool (SWAT). The adequate balance between the model complexity and the functional efficiency of SWAT suits the objective well, and discharge simulation is successfully conducted after customization in melting calculations and careful calibrations. During 1982−2022, the Alaska discharge is estimated to be 14,396 ± 819 m³⋅s⁻¹⋅yr⁻¹, with meltwater contributing approximately 53%. Regarding variation in the Alaska discharge, the interannual change is found to be negatively correlated with sea surface salinity anomalies in the Alaska Stream, while the decadal change positively correlates with the North Pacific Gyre Oscillation, with reasonable time lags in both cases. These new findings provide insights into the relationship between local hydrology and regional climate in this area. More importantly, we provide rare evidence that variation in freshwater discharge may affect properties beyond the local hydrology.