The interplay between regeneration and scavenging fluxes drives ocean iron cycling

• Published in: Nature Communications
• Main Authors: Tagliabue, Alessandro, Bowie, Andrew, DeVries, Timothy, Ellwood, Michael, Landing, William M., Milne, Angela, Ohnemus, Daniel C., Twining, B.S., Boyd, Phillip
• Format: Article in Journal/Newspaper
• Language: English
• Published: Macmillan Publishers Ltd
• Subjects: Antarctic; The Antarctic; Pacific; Antarc*; Antarctic Climate and Ecosystems Cooperative Research Centre
• Online Access: http://hdl.handle.net/1885/206425; https://doi.org/10.1038/s41467-019-12775-5; https://openresearch-repository.anu.edu.au/bitstream/1885/206425/3/01_Tagliabue_The_interplay_between_2019.pdf.jpg

Despite recent advances in observational data coverage, quantitative constraints on how different physical and biogeochemical processes shape dissolved iron distributions remain elusive, lowering confidence in future projections for iron-limited regions. Here we show that dissolved iron is cycled rapidly in Pacific mode and intermediate water and accumulates at a rate controlled by the strongly opposing fluxes of regeneration and scavenging. Combining new data sets within a watermass framework shows that the multidecadal dissolved iron accumulation is much lower than expected from a meta-analysis of iron regeneration fluxes. This mismatch can only be reconciled by invoking significant rates of iron removal to balance iron regeneration, which imply generation of authigenic particulate iron pools. Consequently, rapid internal cycling of iron, rather than its physical transport, is the main control on observed iron stocks within intermediate waters globally and upper ocean iron limitation will be strongly sensitive to subtle changes to the internal cycling balance. This study was initiated during the visit of A.T. to the University of Tasmania (Australia), supported by a University of Tasmania Visiting Scholar award and by a European Research Council (ERC) grant under the European Union’s Horizon 2020 research and innovation programme (project ID 724289) to A.T. A.R.B. was supported by the Australian Research Council (FT130100037 and DP150100345) and the Antarctic Climate and Ecosystems Cooperative Research Centre. M.J.E (DP170102108) and P.W.B. (FL160100131 and DP170102108) were supported by the Australian Research Council. Collection of CLIVAR iron data used in this work was supported by three NSF OCE grants (0223378, 0649639, and 0752832).