Impact of Changes to the Atmospheric Soluble Iron Deposition Flux on Ocean Biogeochemical Cycles in the Anthropocene

Research output: Contribution to journalArticle

Abstract

Iron can be a growth‐limiting nutrient for phytoplankton, modifying rates of net primary production, nitrogen fixation, and carbon export ‐ highlighting the importance of new iron inputs from the atmosphere. The bioavailable iron fraction depends on the emission source and the dissolution during transport. The impacts of anthropogenic combustion and land use change on emissions from industrial, domestic, shipping, desert, and wildfire sources suggest that Northern Hemisphere soluble iron deposition has likely been enhanced between 2% and 68% over the Industrial Era. If policy and climate follow the intermediate Representative Concentration Pathway 4.5 trajectory, then results suggest that Southern Ocean (>30°S) soluble iron deposition would be enhanced between 63% and 95% by 2100. Marine net primary productivity and carbon export within the open ocean are most sensitive to changes in soluble iron deposition in the Southern Hemisphere; this is predominantly driven by fire rather than dust iron sources. Changes in iron deposition cause large perturbations to the marine nitrogen cycle, up to 70% increase in denitrification and 15% increase in nitrogen fixation, but only modestly impacts the carbon cycle and atmospheric CO2 concentrations (1–3 ppm). Regionally, primary productivity increases due to increased iron deposition are often compensated by offsetting decreases downstream corresponding to equivalent changes in the rate of phytoplankton macronutrient uptake, particularly in the equatorial Pacific. These effects are weaker in the Southern Ocean, suggesting that changes in iron deposition in this region dominates the global carbon cycle and climate response.

Details

Authors
  • Douglas S. Hamilton
  • J. Keith Moore
  • Almut Arneth
  • Tami C. Bond
  • Ken S. Carslaw
  • Stijn Hantson
  • Akinori Ito
  • Jed O. Kaplan
  • Keith Lindsay
  • Lars Nieradzik
  • Sagar D. Rathod
  • Rachel A. Scanza
  • Natalie M. Mahowald
Organisations
External organisations
  • Cornell University
  • University of California, Irvine
  • Karlsruhe Institute of Technology
  • Colorado State University
  • University of Leeds
  • Japan Agency for Marine-Earth Science and Technology
  • University of Hong Kong
  • National Centre for Atmospheric Research
  • Pacific Northwest National Laboratory
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Geography
  • Oceanography, Hydrology, Water Resources
  • Meteorology and Atmospheric Sciences
Original languageEnglish
Article numbere2019GB006448
JournalGlobal Biogeochemical Cycles
Volume34
Issue number3
Publication statusPublished - 2020
Publication categoryResearch
Peer-reviewedYes