The use of pH and buffer intensity to quantify the carbon cycle in the ocean

pH of seawater is governed by the content of total carbon dioxide and ionic equilibria between hydrogen ion and various inorganic carbon species in seawater. Buffer intensity is defined as a measure of ability of seawater to accommodate addition of acid or base without appreciable pH change. It can be calculated from pH and total carbon dioxide of seawater. pH data in conjunction with buffer intensity can be used to quantify the carbon cycle in the ocean. The total amount of acid that has been released or consumed by any biogeochemical processes can be calculated from the change in pH multiplied by buffer intensity of seawater, dCH=d(βpH). This approach has been used to quantify the remineralization process in the Antarctic Intermediate Water in the South Pacific. Based on the observational data (pH, total carbon dioxide, O2 and nutrient measurements on P18 cruise), calculated elemental remineralization ratios are 173, 107 and 14.3 for O/P, C/P and N/P, respectively. The dissolution of calcium carbonate accounts for 21.5% of the total carbon released during the remineralization in the Antarctic Intermediate Water.