Air‐sea CO2 fluxes above the stratified oxygen minimum zone in the coastal region off Mexico. Issue 5 (14th May 2014)

• Record Type: Journal Article
• Authors: Franco, Ana C.; Hernández‐Ayón, J. Martín; Beier, Emilio; Garçon, Veronique; Maske, Helmut; Paulmier, Aurelien; Färber‐Lorda, Jaime; Castro, Rubén; Sosa‐Ávalos, Ramón
• Is Part Of: Journal of geophysical research. Volume 119:Issue 5(2014:May)
• Page Start: 2923
• Page End: 2937
• Publication Date: 2014-05-14
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2013JC009337
• Languages: English
• ISSNs: 2169-9275

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Oxygen minimum zones (OMZs) are important sources of CO<sub>2</sub> to the atmosphere when physical forces bring subsurface water with high dissolved inorganic carbon (DIC) to the surface. This study examines, for the first time, the influence of the OMZ of the coastal North Eastern Tropical Pacific off Mexico on surface CO<sub>2</sub> fluxes. We use variations in the oxycline depth and subsurface water masses to discern physical oceanographic influences. During two cruises, in November 2009 and August 2010, DIC and total alkalinity (TA) measurements were used to estimate pCO<sub>2</sub> and air‐sea CO<sub>2</sub> fluxes. At the OMZ layer, Subtropical Subsurface Water (StSsW) was found to have high pCO<sub>2</sub> values (1290 ± 70 μatm). Due to strong vertical stratification, however, the relationship between ΔpCO<sub>2</sub> at the air‐sea interface and the oxycline/StSsW upper limit depth was weak. During November, the region was a weak source of CO<sub>2</sub> to the atmosphere (up to 2.5 mmol C m<sup>−2</sup> d<sup>−1</sup>), while during August a range of values were observed between −4.4 and 3.3 mmol C m<sup>−2</sup> d<sup>−1</sup>). Strong stratification (>1200 J m<sup>−3</sup>) prevented subsurface mixing of water from the OMZ to the upper layer; particularly in November 2009 which was during an El Niño event. Results suggest that advection of surface water masses, reinforced by strong vertical stratification, controlled surface pCO<sub>2</sub>, and air‐sea CO<sub>2</sub> fluxes.</p> </abstract>