Project: Is There an Ocean Primary Production Paradox(OP3)?

NSF Award Abstract:

OCE-0221247

Primary production and remineralization in oligotrophic ocean waters like those around Bermuda are phenomena of central importance in the ocean carbon-cycle and figure prominently in climate change impact modeling. Geochemical constraints on primary production at Bermuda, characterized by annual and longer time-scales and based on three fundamentally different systems, lead to quantitatively consistent estimates of new, net community and export production. This agreement between the three types of primary production would at first seem to be expected on such time-scales, but leads to the basic "Redfield Paradox ": nutrients advected or mixed upward into the euphotic zone must carry with them an associated oxygen debt (AOU) and dissolved inorganic carbon sufficient to negate largely the observed seasonal photosynthetic oxygen buildup and carbon drawdown. An exhaustive consideration of various explanations and scenarios that can be offered fail to explain the observations -- a dilemma here referred to as the "Ocean Primary Production Paradox (OP3)".

A team of researchers at the Woods Hole Oceanographic Institution will re-examine the OP3 by simultaneously and definitively measuring all three geochemical systems over a period of three to four years. These three systems are, specifically, euphotic zone oxygen production, aphotic zone oxygen consumption, and nutrient flux-gauge determinations. The euphotic zone oxygen system will be constrained by the time-series measurement of the full suite of noble gases (He-Xe) plus O2 and N2,with emphasis on precision measurements of O2 and Ar (to 0.1%),the latter as a biogenic analog of oxygen. The other gases will be used to more completely constrain and refine the air-sea gas exchange and upper ocean model.

Aside from addressing fundamental problem in ocean biogeochemistry, this work is expected to have considerably broader impact in the field of ocean geochemistry by providing the oceanographic community with new sampling technology (the noble gas sampler) that can be used in a broad variety of biogeochemical problems. The design and expertise will be made freely available to those who request it.