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Iron(II) variability in the northeast subarctic Pacific Ocean

journal contribution
posted on 2023-05-18, 19:29 authored by Christina SchallenbergChristina Schallenberg, Davidson, AB, Simpson, KG, Miller, LA, Cullen, JT
Distributions of dissolved iron (< 0.2 μm, dFe) and its reduced form, Fe(II), were measured during 3 cruises along Line P, a transect from the continental slope to the high nitrate, low chlorophyll (HNLC) northeast subarctic Pacific Ocean. Concentrations of Fe(II) ranged from below the detection limit (4.3 pM or less) to 330 pM, and dFe concentrations were as high as 3.6 nM. Maximum concentrations for both Fe(II) and dFe occurred in waters over the continental slope, with Fe(II) consistently increasing towards the bottom, consistent with Fe(II) supply from benthic sources on the continental shelf and slope. Low oxygen concentrations (~ 10 μM) and pH (~ 7.5) in the North Pacific oxygen deficient zone (ODZ) likely serve to stabilize Fe(II) and may contribute to enhanced dFe release from shelf and slope sediments via reductive dissolution. Concentration gradients along isopycnal surfaces indicate that Fe(II) is transported several hundred kilometers from the continental slope at depth, and there is evidence that episodic events may advect shelf-derived Fe(II) similar distances near the surface. Comparison of transport times and Fe(II) half-lives suggests that it is unlikely for pre-formed Fe(II) to be transported these distances, but that sedimentary particles advected off the shelf and slope may constitute a continuous source of Fe(II) both at depth and near the surface. At the offshore stations, the Fe(II) time series reveals deep local maxima that are transient in time and space and are consistent with a sporadic Fe(II) source, such as remineralization of sinking particles.

History

Publication title

Marine Chemistry

Volume

177

Issue

Part 1

Pagination

33-44

ISSN

0304-4203

Department/School

Institute for Marine and Antarctic Studies

Publisher

Elsevier Science Bv

Place of publication

Po Box 211, Amsterdam, Netherlands, 1000 Ae

Rights statement

© 2015 Elsevier

Repository Status

  • Restricted

Socio-economic Objectives

Measurement and assessment of marine water quality and condition

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