Primary production and carbon export rates across the subpolar N. Atlantic Ocean basin based on triple oxygen isotope and dissolved O₂ and Ar gas measurements

Abstract

Gross photosynthetic O 2 production (GOP) rates in the subpolar North Atlantic Ocean were estimated using the measured isotopic composition of dissolved oxygen in the surface layer on samples collected on nine transits of a container ship between Great Britain and Canada during March 2007 to June 2008. The mean basin‐wide GOP rate of 226 ± 48 mmol O 2 m −2 d −1 during summer was double the winter rate of 107 ± 41 mmol O 2 m −2 d −1 . Converting these GOP rates to equivalent 14 C‐based PP ( 14 C‐PP eqv ) yielded rates of 1005 ± 216 and 476 ± 183 mg C m −2 d −1 in summer and winter, respectively, that generally agreed well with previous 14 C‐based PP estimates in the region. The 14 C‐PP eqv estimates were 1–1.6× concurrent satellite‐based PP estimates along the cruise track. A net community production rate (NCP) of 87 ± 12 mmol O 2 m −2 d −1 (62 ± 9 mmol C m −2 d −1 ) and NCP/GOP of 0.35 ± 0.06 in the mixed layer was estimated from O 2 /Ar and 17 Δ measurements (61°N 26°W) during spring bloom conditions in May 2008. Contrastingly, a much lower long‐term annual mean NCP or organic carbon export rate of 2.8 ± 2.7 mol C m −2 yr −1 (8 ± 7 mmol C m −2 d −1 ) and NCP/GOP of 0.07 ± 0.06 at the winter mixed layer depth was estimated from 15 years of surface O 2 data in the subpolar N. Atlantic collected during the CARINA program.