Modelling North-Atlantic water column respiratory CO2 production, vertical carbon flux, nutrient retention efficiency, and benthic respiration

Abstract

New North Atlantic rates of carbon-flux (Fc), oxygen utilization (OUR), and mineralization, when combined with new oceanographic concepts, can provide new insight into the dynamics of metabolic ocean biogeochemistry. Here, data from heliumtritium dating, advection-diffusion modeling, apparent oxygen utilization, respiratory electron transport activity (ETS), and three different types of sediment traps were used to calculate new metabolic-based rates. First, we used OUR to calculate CO2 remineralization (Jc) profiles. Jc, at 100m, ranged from 0.4 to 109 millimol CO2 m-3 yr-1and from 1000m, it ranged lower, from 0.001 to 4.3 millimol CO2 m-3 yr-1. Secondly, we used Jc to calculate carbon flux (Fc) profiles. These, plus measured Fc, ranged from 1.5 to 17.8 millimol C m-2 yr-1 at 100m and to 0.03 to 12.1 millimol C m-2 yr-1 at 1000m. Thirdly, integrating Jc from the bottom of the mixed layer to the seafloor yielded New Production (NP) and Export Production (E). The two are considered equal. We found a North Atlantic NP range of 0.07 to 23.3 mol C m-2 yr-1. Fourth, from the ratio, Jc/Fc, we calculated the nutrient retention efficiency (NRE = (Jc/Fc,)*100) that predicts future regenerated production. NRE is inversely related to carbon-flux transfer efficiency (Teff) and both NRE and Teff are related to b, the attenuation exponents of Jc and Fc. For a 50m water column centered at 125m, NRE ranged from 51 to 27% while Teff ranged from 49 to 73%. In a 50m water column at 1025m, NRE ranged, much lower, from 8 to 4 % while Teff ranged, much higher, from 92 to 96%. Fifth, benthic Jc was calculated, using different limits of integration, from Fc. It varied indirectly with water column NRE. For the North Atlantic, we found that benthic Jc ranged from 2.1 to 7040.0 millimol C m-2 yr-1.