Net community production rates across the subtropical and equatorial Pacific Ocean estimated from air‐sea δ13C disequilibrium

Abstract

Rates of net community production (NCP) in the mixed layer were estimated using measurements of the 13C/12C of dissolved inorganic carbon (DIC) in surface waters of the subtropical and equatorial Pacific Ocean on samples collected during nine container ship cruises between California and Australia in 2004–2005. The rate of NCP in the surface mixed layer was determined from the magnitude of the air‐sea δ13C disequilibrium using mixed layer DIC and DIC13 budgets. The estimated NCP rates between 30°N and 30°S varied from 1.9 to 3.9 mols C m−2 a−1 with a mean value of 2.9 ± 0.8 mols C m−2 a−1. NCP rates in the equatorial ocean (3.4 ± 0.6 mols C m−2 a−1) were higher than in subtropical gyres (2.6 ± 0.6 mols C m−2 a−1). These rates of NCP were significantly higher than NCP rates previously estimated from DIC drawdown and satellite algorithms of productivity but consistent with NCP estimates from oxygen budgets and inverse models. In this region of the Pacific Ocean the estimated NCP rate was 3.6 Pg C a−1.