When GEOTRACES‐based synthesis efforts improve global iron-cycling understanding

Joint Science Highlight with US-Ocean Carbon & Biogeochemistry (US-OCB).

Authors of a recent paper published in Global Biogeochemical Cycles conducted a detailed study of the residence times of total and dissolved iron (Fe) in the upper layers (0-250m) of the global ocean. Using historical (1987-2007) and recent GEOTRACES data, they compiled an impressive data set comprising dissolved, filtered and trap-collected particulate Fe spanning different biogeochemical oceanographic provinces. They also used indirect isotopic approaches to calculate Fe export from the surface layers (e.g., based on thorium-234-uranium-238 disequilibrium). The study revealed that upper ocean residence times of total Fe consistently fell between 10 and 100 days, despite a broad range of total Fe inventories and ocean biogeochemical settings. Conversely, dissolved Fe residences times were longer and more variable, cycling on sub annual to annual time scales. In addition to these detailed insights on upper ocean Fe cycling, these new data sets will help constrain the rate constant for total Fe export, an important term for exploring links between ocean Fe cycling and the global carbon cycle in ocean biogeochemical models.

Figures (from Black et al, 2020): In-situ iron concentration and export (Ftot) estimates from numerous GEOTRACES efforts were combined with prior study results to constrain the residence time of iron in the upper ocean (diagonal lines, lower panel). Broad patterns in iron residence times emerged when contrasting coastal and open regions (pink vs. white), as well as with high and low latitude zones (black vs. white). Despite clear regional differences, however, the majority of residence times for total iron fell into a small range between 10 and 100 days.


Reference:

Black, E. E., Kienast, S. S., Lemaitre, N., Lam, P. J., Anderson, R. F., Planquette, H., Planchon, F., Buesseler, K. O. (2020). Ironing Out Fe Residence Time in the Dynamic Upper Ocean. Global Biogeochemical Cycles, 34(9). DOI: https://doi.org/10.1029/2020GB006592

Latest highlights

Science Highlights

Icebergs as sources of trace metals to the ocean: which impact?

Earth’s Ice Sheets are known to release significant quantities of lithogenic particles into the ocean every year, but how does this material affect trace metal availability in the ocean?

18.10.2021

Science Highlights

Microbial trace metal trafficking on marine particles

This study provides evidence for the processing of nine particulate trace metals in multiple manners by diverse microbial communities.

28.09.2021

Science Highlights

Volcanic emissions in the Southern Ocean: an efficient and unexpected source of iron for this remote area

This study suggests that volcanic emission can represent a significant source of bioavailable Fe to open ocean anaemic ecosystems.

20.09.2021

Science Highlights

Surprisingly heavy silicon isotopes in the surface and deep Arctic Ocean

Brzezinski and his colleagues report on a comprehensive study of the Arctic Ocean silicic acid concentrations and silicon isotopic composition…

14.09.2021

Rechercher