Peng¹, Tsung-Hung, and Yuan-Hui Li²

¹NOAA/AOML, Ocean Chemistry Division, Miami, FL 33149, USA, Tel: 305-361-4399, Fax: 305-361-4392, E-mail: Tsung-Hung.Peng@noaa.gov and ²Department of Oceanography, University of Hawaii, Honolulu, HI 96822

Penetration of anthropogenic CO₂ in the oceans based on analysis of recent WOCE/JGOFS carbon data using the remineralization ratios obtained by the Three-End-Member Mixing Model

In a recent report (Li and Peng, 2002), a new three-end-member mixing model is used to obtain remineralization ratios of organic matter in the water column. Remineralization ratios (P/N/C_org/-O₂) of organic matter in the deep water column change systematically from the northern Atlantic to the Southern Oceans, then to the equatorial Indian and the northern Pacific oceans, more or less along the global ocean circulation route of deep water. For example, average remineralization ratios of organic matter for the northern Atlantic Ocean are P/N/C_org/-O₂ = 1/(16±1)/(73±8)/(137±7), and for the Southern Oceans 1/(15±1)/(80±3)/(133±5). Those values are similar to the traditional Redfield ratios of 1/16/106/138 for marine plankton, except for the low C_org/P ratio. Average remineralization ratios for the equatorial Indian Ocean are 1/(10±1)/(94±5)/(130±7), and for the northern Pacific Ocean 1/(13±1)/(124±11)/(162±11). The apparent low N/P ratio for both ocean basins suggests that organic nitrogen was converted partly into gaseous N₂O and N₂ by bacteria through nitrification/denitrification processes in a low-oxygen or reducing micro-environment of organic matter throughout the oxygenated water column. The actual N/P ratio of remineralized organic matter is probably around 15±1. In contrast, uniform remineralization ratios are assumed for almost all the current calculations using DC* method for the anthropogenic CO₂ inventory in the three major oceans (for example, Gruber et al., 1996; Gruber, 1998; Sabine et al., 1999 and 2002; and Feely et al., 2001). How much difference in anthropogenic CO₂ penetration into the ocean could be made if the new results of variable ratios are used? In this study, a new method, which is different from DC* method is developed for estimating the penetration of anthropogenic CO₂ into the ocean, specifically using the current variable remineralization ratios. For illustration, comparison of results based on HOT station north of Hawaii will be made between using uniform remineralization ratios and variable remineralization ratios.