Air-sea carbon fluxes and their controlling factors in the Prydz Bay in the Antarctic

The Prydz Bay in the Antarctic is an important area in the Southern Ocean due to its unique geographic feature. It plays an important role in the carbon cycle in the Southern Ocean. To investigate the distributions of carbon dioxide in the atmosphere and surface seawater and its air-sea exchange rates in this region, the Chinese National Antarctic Research Expedition (CHINARE) had set up several sections in the Prydz Bay. Here we present the results from the CHINARE - XVI cruises were presented onboard R/V Xuelong from November 1999 to April 2000 and the main driving forces were discussed controlling the distributions of partial pressure of carbon dioxide. According to the partial pressure of carbon dioxide distributions, the Prydz Bay can be divided into the inside and outside regions. The partial pressure of carbon dioxide was low in the inside region but higher in the outside region during the measurement period. This distribution had a good negative correlation with the concentrations of chlorophyll-a in general, suggesting that the partial pressure of carbon dioxide was substantially affected by biological production. The results also indicate that the biological production is most likely the main driving force in the marginal ice zone in the Southern Ocean in summer. However, in the Antarctic divergence sector of the Prydz Bay (about 64°S), the hydrological processes become the controlling factor as the sea surface partial pressure of carbon dioxide is much higher than the atmospheric one due to the upwelling of the high DIC CDW, and this made the outside of Prydz Bay a source of carbon dioxide. On the basis of the calculations, the CO₂ flux in January (austral summer) was -3.23 mmol/(m² · d) in the inner part of Prydz Bay, i.e., a sink of atmospheric CO₂, and was 0.62 mmol/(m² · d) in the outside part of the bay, a weak source of atmospheric CO₂. The average air-sea flux of CO₂ in the Prydz Bay was 2.50 mmol/(m² · d).