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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. C5, 3144, doi:10.1029/1999JC000047, 2003

Carbon distribution, fluxes, and budgets in the subtropical North Atlantic Ocean (24.5°N)

G. Rosón

Facultad de Ciencias del Mar, Universidad de Vigo, Vigo, Spain

A. F. Ríos

Instituto de Investigacións Mariñas, Consejo Superior de Investigaciones Científicas, Vigo, Spain

F. F. Pérez

Instituto de Investigacións Mariñas, Consejo Superior de Investigaciones Científicas, Vigo, Spain

A. Lavín

Instituto Español de Oceanografía, Santander, Spain

H. L. Bryden

Southampton Oceanography Centre, Southampton, UK

Abstract

Hydrographic CO₂ system data obtained from World Ocean Circulation Experiment (WOCE) transatlantic zonal section A5 across 24.5°N and Florida Straits are described. By combining CO₂ measurements with hydrographic velocity calculations, the zonal and vertical variability of meridional fluxes of total alkalinity (TA), total dissolved inorganic carbon (TIC), and anthropogenic CO₂ (δC) are estimated. The resulting CO₂ fluxes are examined in four geostrophic mid-ocean zones as well as in the Gulf Stream flow through Florida Straits and in the surface ageostrophic Ekman flow. This method allows an estimate of the net budgets of these chemical species in the system considering together the Arctic and Atlantic Oceans north of 24.5°N. Taking into account the net flux contribution through Bering Strait, total meridional transports of chemical properties across 24.5°N latitude are also estimated. The slightly divergent net TA budget (−460 ± 200 kmol s⁻¹) suggests that the North Atlantic is a small alkalinity source. The divergent TIC budget (−2430 ± 200 kmol s⁻¹ or −0.92 ± 0.08 GtC yr⁻¹) suggests that the North Atlantic is a source of TIC and therefore a net sink for atmospheric CO₂. This value is twice as large as a previous estimation made from a poorly sampled section. Surprisingly, the North Atlantic Ocean appears to act as a net sink of anthropogenic CO₂ (+630 ± 200 kmol s⁻¹ or +0.24 ± 0.08 GtC yr⁻¹) and therefore a weak source of anthropogenic CO₂ to the atmosphere. Its main contributor is the intense northward flux in the Florida Current (+1280 ± 100 kmol s⁻¹). The calculations imply a divergent inorganic carbon budget of −3060 ± 200 kmol s⁻¹ or −1.16 ± 0.08 GtC yr⁻¹ in preindustrial times (TIC₂₇₈, when the molar fraction of CO₂ in the atmosphere was 278.2 ppm). This means that the North Atlantic would have had a 25% stronger divergence of TIC prior to the beginning of anthropogenic CO₂ penetration.

Received 10 August 1999; accepted 21 February 2003; published 14 May 2003.

Index Terms: 4806 Oceanography: Biological and Chemical: Carbon cycling; 4532 Oceanography: Physical: General circulation; 4283 Oceanography: General: Water masses; 1803 Hydrology: Anthropogenic effects.

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Citation: Rosón, G., A. F. Ríos, F. F. Pérez, A. Lavín, and H. L. Bryden (2003), Carbon distribution, fluxes, and budgets in the subtropical North Atlantic Ocean (24.5°N), J. Geophys. Res., 108(C5), 3144, doi:10.1029/1999JC000047.

Copyright 2003 by the American Geophysical Union.