Dissolved Organic Carbon in the North Atlantic Meridional Overturning Circulation.

Marcos Fontela,Maribel I García-Ibáñez,Dennis A Hansell,Fiz F Pérez,Herlé Mercier

doi:10.1038/srep26931

Abstract

The quantitative role of the Atlantic Meridional Overturning Circulation (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr−1). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr−1) is considerable and represents almost a third of the atmospheric CO2 uptake in the region.

Highlights

The Atlantic Meridional Overturning Circulation (AMOC) plays an active role in the cycling and storage of chemical species in the ocean[1,2] because it is an entrance portal for chemical tracers into the deep ocean due to water mass formation processes
The high [dissolved organic carbon (DOC)] of the surface waters of the OVIDE section (40°N–60°N) present no meridional trend (p-level = 0.91), which contrasts with the latitudinal gradient previously reported for a zonal section in the North Atlantic[20]
Since the OVIDE section crosses North Atlantic Current (NAC) branches with waters of different ages, the DOC features observed in surface correspond to the variability of the mode waters due to their formation processes instead of a latitudinal gradient (Fig. 2). [DOC] decreases with depth to values

Summary

Introduction

The Atlantic Meridional Overturning Circulation (AMOC) plays an active role in the cycling and storage of chemical species in the ocean[1,2] because it is an entrance portal for chemical tracers into the deep ocean due to water mass formation processes. DOC is the largest pool of organic matter in the ocean[14], playing an important role in ocean biogeochemistry It is produced in the euphotic zone by biological activity and can be exported, i.e. moved to the deep ocean, by physical processes where it is remineralized. The main objectives of the present work are (i) to estimate the DOC transport and budget in the eastern-SPNA, and (ii) to disentangle the role of the AMOC in the DOC cycle

Objectives

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Results

Conclusion