Determination of the Redfield Remineralization Ratios Based on Neutral Surface Analysis of the New Global Data Set

NSF ('99), 36 months
 

PROJECT SUMMARY

Synthesis of primary nutrients by marine organisms and subsequent remineralization of organic matter is frequently represented by Equation 1

H₃PO₄ + alphaHNO₃ + betaCO₂ + gammaH₂O = C_betaH_zetaO_etaN_alphaP + phiO₂

where the coefficients are known as the "Redfield" ratios. Redfield ratios have been particularly useful in estimating the utilization of one nutrient from another and in deriving dynamically passive conservative tracers such as "NO" and "PO".  More recently PO₄*, C* and N* have been used to study air-sea oxygen fluxes, large scale mixing problems, anthropogenic CO₂ and nitrogen biogeochemistry.  The value of the ratios and their large scale variability are also important because they are a critical component in the application of computer models to study ocean biogeochemistry and global climate change.

The traditional P:N:C_org Redfield ratios of 1:16:106 were based on planktonic decomposition studies.  Recent studies have reevaluated the ratios.  Significant disagreement still exists, however. In large part the disagreement stems from various weaknesses in the approaches and in the overall quality and quantity of the data sets used.

The goal of this project is to redetermine the Redfield ratios of remineralization.  Specific improvements over previous efforts include the availability of a new global high quality nutrient data set and application of an optimal multi-parameter technique to determine endpoints.  The technique will be applied on approximately 20 neutral density layers in each ocean basin.   A significant improvement over previous work will be the inclusion of the recently completed global CO₂ survey results along with the new nutrient data.  In the analysis corrections for the potential bias caused by anthropogenic CO₂ invasion, nitrogen fixation and denitrification will be made.  Preliminary investigations have demonstrated that small systematic offsets exist in the nutrient data.  Therefore, prior to calculation of the Redfield ratios, a comprehensive global calibration of the nitrate, phosphate and silicate data sets will be completed.  The analytical procedures for this calibration have already been developed.  The results of this work will directly address specific research trajectory elements 1 and 2 outlined in the JGOFS SMP implementation plan and will benefit several collaborative efforts.
 

Robert M. Key
Princeton University
Program in Atmospheric and Ocean Sciences
Department of Geosciences, Guyot Hall
Princeton, NJ 08544-1003
tel: (609) 258-3595,3222
key@geo.princeton.edu
http://geo.princeton.edu/u_faculty/key.html

Christopher Sabine
Princeton University
Program in Atmospheric and Ocean Sciences
Department of Geosciences, Guyot Hall
Princeton, NJ 08544-1003
tel: (609) 258-6899
sabine@geo.princeton.edu
http://geo.princeton.edu/~sabine/index.html

Louis I. Gordon
College of Oceanic & Atmospheric Sciences
Oregon State University
104 Ocean Admin Bldg
Corvallis, OR 97331-5503
tel: (541) 737-2161
fax: (541) 737-2064
lgordon@oce.orst.edu
http://www.oce.orst.edu/faculty/gordon.html

Nicolas Gruber
Program in Atmospheric and Ocean Sciences
Department of Geosciences
Princeton University
Princeton, NJ 08544-1003
gruber@splash.Princeton.EDU
tel: 609-258-1314
fax: 609-258-2850
http://www.climate.unibe.ch/~gruber/index.html

C.W. Mordy
JISAO/PMEL
University of Washington