North Atlantic Western Boundary Currents Are Intense Dissolved Organic Carbon Streams

Type Article
Date 2020-11
Language English
Author(s) Fontela Marcos1, 2, Pérez Fiz F2, Mercier Herle3, Lherminier Pascale4
Affiliation(s) 1 : Instituto de Investigaciones Marinas (IIM-CSIC), Vigo, Spain
2 : Centre of Marine Sciences (CCMAR), University of Algarve, Faro, Portugal
3 : Laboratoire d’Océanographie Physique et Spatiale, UMR 6523 CNRS-IFREMER-IRD-University of Brest, Plouzané, France
4 : Laboratoire d’Océanographie Physique et Spatiale, UMR 6523 CNRS-IFREMER-IRD-University of Brest, Plouzané, France
Source Frontiers In Marine Science (2296-7745) (Frontiers Media SA), 2020-11 , Vol. 7 , P. 593757 (10p.)
DOI 10.3389/fmars.2020.593757
Keyword(s) dissolved organic carbon, North Atlantic, carbon budget, carbon dioxide, biogeochemistry, Atlantic Meridional Overturning Circulation
Abstract

In the North Atlantic, there are two main western boundary currents related to the Atlantic Meridional Overturning Circulation (AMOC): the Gulf Stream flowing northward and the Deep Western Boundary Current (DWBC) flowing southward. Here we analyze data from the OVIDE section (GO-SHIP A25 Portugal-Greenland 40–60°N) that crosses the DWBC and the northward extension of the Gulf Stream, the North Atlantic Current. We show that North Atlantic western boundary currents play a key role in the transport of dissolved organic matter, specifically dissolved organic carbon (DOC). Revisited transports and budgets of DOC with new available data identify the eastern Subpolar North Atlantic (eSPNA) as an important source of locally produced organic matter for the North Atlantic and a key region in the supply of bioavailable DOC to the deep ocean. The East Greenland Current, and its upstream source the East Reykjanes Ridge Current on the eastern flank of the mid-Atlantic ridge, are export pathways of bioavailable DOC toward subtropical latitudes. The fast overturning and subsequent remineralization of DOC produced in the autotrophic eSPNA explains up to 38% of the total oxygen consumption in the deep North Atlantic between the OVIDE section and 24°N. Carbon budgets that do not take into account this organic remineralization process overestimates the natural uptake of carbon dioxide (CO2) from the atmosphere by one third. The inclusion of DOC transports in regional carbon budgets reconciles the estimates of CO2 uptake in the North Atlantic between model and observations.

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