Redfield ratios of remineralization determined by nutrient data analysis

Abstract

A nonlinear inverse method is applied to nutrient data upon approximately 20 neutral surfaces in each of the South Atlantic, Indian, and Pacific basins, between 400 and 4000 m depth. By accounting for the gradients in nutrients due to the mixing of “preformed” concentrations of the major water masses, the nutrient changes due to biological activity are examined, and the time‐mean, basin‐wide Redfield ratios calculated. It is found that the P/N/Corg/−O2 ratios of nutrient regeneration between 400 and 4000 m (corrected for the effect of denitrification) are approximately constant with depth and basin, at a value of 1/16 ± 1/117 ± 14/170 ± 10. These ratios agree with those of fresh organic matter, suggesting that the flux of organic material to the deep ocean may be dominated by fast‐sinking matter produced by sporadic, high‐productivity events. Sedimentary denitrification reduces the N/P utilization ratio to 12 ± 2 between 1000 and 3000 m. In the Indian and Pacific basins the Corg/Cinorg regeneration ratio decreases from approximately 7 ± 3 at 400 m to 3 ± 1 at 1000 m and to 1 ± 0.5 at 4000 m, suggesting a significant amount of calcium carbonate dissolution above the calcite lysoclines in the Indian and Pacific oceans.

Decadal changes in the CaCO3 saturation state along 179°E in the Pacific Ocean

“…DnC T org was calculated as DnC T org = DAOU Χ g, where DAOU is the difference in apparent oxygen utilization (AOU) between the 1993 and 2007, and g is the C:O stoichiometric ratio. For g, we adopted the value 0.69 [Anderson and Sarmiento, 1994]. AOU is defined as the difference between the observed concentration of dissolved oxygen (DO) and the saturated DO concentration at a given potential temperature and salinity.…”

Anthropogenic CO2 in the Atlantic Ocean

“…The preformed alkalinity Alk ø is estimated from a multiple linear regression model using the conservative tracers salinity (S) and PO -02 -ro2:pPO4 [Broecker, 1974] as independent variables [Gruber et al, 1996]. The stoichiometric ratios determined by Anderson and Sarmiento [1994] are used throughout this study. These ratios P:N:C'org'O2 n /k •diseq • fi i --/kC•iseq,…”

“…This tracer is defined as PO• -PO4 -rp:o2 02 -1.95. I chose rp:o2 = 1/(-170) [Anderson and Sarmiento, 1994] rather than the Broecker et al [1991] original value of 1/(-175). The PO• end-members for each investigated isopycnal interval are shown in Table 2.…”

Dysaerobic conditions during Heinrich events 4 and 5: Evidence from phosphorus distribution in a North Atlantic deep-sea core

“…Molar TOC/P org in ambient glacial sediments (193 Ϯ 41; Fig. 5) provides values slightly higher than the Redfield ratio estimated for marine organic matter from nutrient data analysis (117 Ϯ 14; Anderson and Sarmiento, 1994). In our samples, TOC/P org generally displays lower values within HLs (148 Ϯ 30).…”