FY 2010
Basin-wide photosynthetic production rates in the subtropical and tropical Pacific Ocean determined from dissolved oxygen isotope ratio measurements
Juranek, L.W., and P.D. Quay
Global Biogeochem. Cycles, 24, GB2006, doi: 10.1029/2009GB003492 (2010) |
| We used the oxygen isotope anomaly (17Δ) to determine gross photosynthetic O2 production (GOP) on Pacific Ocean transits of a cargo ship between United States and Australia and New Zealand in August 2004 and February, August, and November 2005. The 17Δ approach yielded robust regional GOP averages of 98 ± 8, 200 ± 11, 115 ± 7, and 182 ± 32 mmol O2 m−2 d−1 for the northern subtropics, tropics, southern subtropics, and South Coral and Tasman Sea, respectively. When converted to 14C primary production (PP) rate equivalents, the 17Δ-based rates compare favorably with prior field data and indicate that satellite algorithms (i.e., vertically generalized productivity model (VGPM) and carbon-based model (CBM)) underestimate in situ rates by a factor of 1.3–3, with greatest underestimation in the tropics. We determined empirical relationships between chlorophyll, nitrate, and GOP that explain 81% of variance in observed GOP rates. Integrating over the Pacific basin from 30°N to 30°S (excluding coastal areas) yields a gross production of 37.3 Gt C yr−1 and a 14C PP equivalent of 20.3 Gt C yr−1, 1.3–1.8 × higher than the 11.4 and 15.9 Gt C yr−1 estimated by the VGPM and CBM, respectively. |
