A new application of aerosol iron isotopes: tracing anthropogenic iron; an example of the North Atlantic Ocean

Science Highlights

8 October 2019

Conway and co-authors (2019, see reference below) present the first evidence that anthropogenic iron (Fe) from combustion sources is visible at the basin scale, using iron isotopic composition (δ56Fe) analysis of the soluble aerosol phases collected during GEOTRACES cruise GA03 in the North Atlantic Ocean. Off Sahara, soluble aerosol samples have near-crustal δ56Fe whereas those from near North America and Europe display δ56Fe values as light as −1.6‰. Coupled to aerosol deposition modeling these results reveal that soluble anthropogenic aerosol Fe flux to the global surface oceans is highly likely to be underestimated.

Figure: Tracing anthropogenic iron with iron isotopes (adapted from Conway et al., 2019). Panels a and b show that aerosols collected from near the Sahara have low solubility, a near-crustal iron isotope composition (beige circle) and a near-crustal Pb/Al composition (beige diamond). In contrast, those collected from near North America or Western Europe have very soluble iron, very light iron isotopes and are very enriched in Pb, indicating pollution from humans. When sampling points are overlain on output from dust modelling, it can be seen that the light iron isotopes correspond to where fossil fuel iron is expected to be important, and the crustal iron isotopes correspond to where natural dust iron is most important (panel c). Click on the image to view it larger.

Reference:

Conway, T. M., Hamilton, D. S., Shelley, R. U., Aguilar-Islas, A. M., Landing, W. M., Mahowald, N. M., & John, S. G. (2019). Tracing and constraining anthropogenic aerosol iron fluxes to the North Atlantic Ocean using iron isotopes. Nature Communications, 10(1), 2628. DOI: https://doi.org/10.1038/s41467-019-10457-w

Latest highlights

Organic matter export rates along a North-South Pacific Ocean section: what three estimating methods tell us

Quay and his colleagues present estimates of the organic matter export rate along the GEOTRACES GP15 cruise section.

East-West contrasting fate and anthropogenic inputs for dissolved trace metals in the Subarctic Pacific Ocean

Chan and co-authors report the full-depth distribution of dissolved nickel, copper, zinc, and cadmium in the North Pacific Ocean.

Comprehensive quantification of the rare earth element cycle in the northwest Pacific Ocean

Cao and co-authors investigate dissolved rare earth elements and the factors controlling their distributions in the northwest Pacific Ocean.

Iron and zinc isotopes disentangle the anthropogenic, natural and wildfire sources of aerosols over the North and Equatorial Pacific Ocean

Bunnell and co-authors analysed aerosol iron and zinc isotopic compositions along the North Pacific GEOTRACES GP15 section (Alaska-Tahiti).

Rechercher