Dissolved inorganic carbon, alkalinity, nutrient and oxygen seasonal and interannual variations at the Antarctic Ocean JGOFS-KERFIX site

JGOFS-KERFIX (KERguelen point FIXe) time-series station, located south of t he polar front in the Indian sector of the Antarctic Ocean, was occupied mo nthly between January 1990 and March 1995. Annual cycles of dissolved inorg anic carbon (DIC), total alkalinity (TALK), oxygen (O-2) and nutrients (nit rate, silicate, phosphate and ammonia) in the upper ocean are presented for this site. From seasonal drawdown of nutrients and DIG, we estimate a spri ng-summer net community production of 3.2 +/- 0.5 mol m(-2) and C/N/P ratio s of 100/16/1. The Si/N ratio varies between 1.8 and 3, suggesting low iron concentrations. The spring-summer biogenic silicon export derived from sil icate drawdown is 1.18 mol m(-2), consistent with model estimates of silica te export at this site. Seasonal and interannual variations of oxygen, nitr ate and DIC due to physical and biological processes are quantified using a simple month-to-month budget formulation, From these budgets, an annual ne t community production of 5.7 +/- 3.3 mol m(-2) yr(-1) is estimated, about twice the averaged spring-summer production, indicating that, at KERFIX, th ere is a positive net community production throughout the year. Air-sea CO2 fluxes show that KERFIX is a strong COL sink for the atmosphere of 2.4-5.1 mol m(-2) yr(-1) in 1993, depending on the gas exchange formulation used. A 2.1-3.3 mol m(-2) yr(-1) outgassing of O-2 is observed at KERFIX except i n 1993 and 1994 where a decreasing trend of temperature induces an increase of O-2 solubility. (C) Elsevier Science Ltd. All rights reserved.