DEPTH DISTRIBUTION OF DELTA-C-13 OF DISSOLVED SIGMA-CO2 IN SEAWATER OFF EASTERN TAIWAN - EFFECTS OF THE KUROSHIO CURRENT AND ITS ASSOCIATEDUPWELLING PHENOMENON

This paper presents depth variations of dissolved O-2, Sigma CO2, alka linity, and delta(13)C of Sigma CO2 in seawater off eastern Taiwan. O- 2 decreases from an averaged surface value of approximately 4.6 ml l(- 1) to a minimum of about 2.0 ml l(-1) at a depth of 1000 m, and then i ncreases gradually to about 3.5 ml l(-1) near the seafloor. Sigma CO2 concentrations increase from typical values of 1900-2050 mu mol kg(-1) at the surface to 2100-2300 mu mol kg(-1) at depths of more than 1000 m, corresponding to an increase in alkalinity from about 2250 mu eq k g(-1) at the surface to 2450 mu eq kg(-1) in the bottom water. delta(1 3)C of Sigma CO2 at the surface averages about +0.25% and becomes ligh ter with increasing depth to approximately -1.0%. The observed depth d istributions of O-2, Sigma CO2, alkalinity and delta(13)C of Sigma CO2 , are thus similar to those reported in the open ocean and can be attr ibuted to O-2 utilization and CO2 production during organic decomposit ion. On a close examination, however, rates of O-2 decrease and Sigma CO2 and alkalinity increases are less profound than those observed in the open ocean, particularly in the Pacific. Furthermore, values of de lta(13)C measured are invariably lighter than those reported in the Pa cific. The discrepancy is attributed largely to the presence of the Ku roshio current and its associated upwelling phenomenon in the continen tal margin off eastern Taiwan. Copyright (C) 1996 Elsevier Science Ltd .