Preprints
https://doi.org/10.5194/bgd-4-1241-2007
https://doi.org/10.5194/bgd-4-1241-2007
25 Apr 2007
 | 25 Apr 2007
Status: this preprint was under review for the journal BG but the revision was not accepted.

Observations of dissolved iron concentrations in the World Ocean: implications and constraints for ocean biogeochemical models

J. K. Moore and O. Braucher

Abstract. Analysis of a global compilation of dissolved iron observations provides insights into the controlling processes for iron distributions and some constraints for ocean biogeochemical models. The distribution of dissolved iron is consistent with the conceptual model developed for the scavenging of Th isotopes, whereby particle scavenging is a two-step process of scavenging mainly by colloidal and small particulates followed by aggregation and removal on larger sinking particles. Much of the dissolved iron (<0.4 μm) is present as small colloids (>~0.02 μm) and, thus, likely subject to aggregation and scavenging removal. Only the iron bound to soluble ligands (<~0.02 μm) is likely protected from scavenging removal. This implies distinct scavenging regimes for dissolved iron that appear consistent with the observational data: 1) high scavenging regime – where dissolved iron concentrations exceed the concentrations of strongly binding organic ligands; and 2) moderate scavenging regime – where dissolved iron is bound to both colloidal and soluble ligands. The removal rates for dissolved iron will be a function of biological uptake, number and size distributions of the colloidal and small particulate material, ligand dynamics, and the aggregation processes that lead to removal on larger particles.

Inputs from dust deposition and continental sediments are key drivers of dissolved iron distributions. The observations provide several strong constraints for ocean biogeochemical models: 1) similar deep ocean concentrations in the North Atlantic and North Pacific (~0.6–0.8 nM), and much lower deep ocean dissolved iron concentrations in the Southern Ocean (~0.3–0.4 nM); 2) strong depletion of iron in the upper ocean away from the high dust deposition regions, with significant scavenging removal of dissolved iron below the euphotic zone; and 3) a bimodal distribution in surface waters with peaks less than 0.2 nM and between 0.6–0.8 nM. We compare the dissolved iron observations with output from the Biogeochemical Elemental Cycling (BEC) ocean model. The model output was in general agreement with the field data (r=0.76, for depths 103–502 m), but at lower iron concentrations (<0.3 nM) the model is consistently biased high relative to the observations.

J. K. Moore and O. Braucher
 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
J. K. Moore and O. Braucher
J. K. Moore and O. Braucher

Viewed

Total article views: 2,739 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
922 1,750 67 2,739 52 49
  • HTML: 922
  • PDF: 1,750
  • XML: 67
  • Total: 2,739
  • BibTeX: 52
  • EndNote: 49
Views and downloads (calculated since 01 Feb 2013)
Cumulative views and downloads (calculated since 01 Feb 2013)

Cited

Saved

Latest update: 23 Apr 2024
Download
Altmetrics