Inorganic carbon dynamics and air-ice-sea CO2 fluxes in the open and coastal waters of the Southern Ocean

• Main Author: Delille, Bruno
• Other Authors: Borges, Alberto, Ronday, François, FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: ULiège - Université de Liège 2006
• Subjects: Physical; chemical; mathematical & earth Sciences; Earth sciences & physical geography; Physique; chimie; mathématiques & sciences de la terre; Sciences de la terre & géographie physique; Southern Ocean
• Online Access: https://orbi.uliege.be/handle/2268/252964; https://orbi.uliege.be/bitstream/2268/252964/1/Delille%202006.pdf

Despite the fact that the Southern Ocean (S.O.) is a high nutrients-low chlorophyll area (HNLC), it acts as a significant sink for atmospheric CO2. We addressed the temporal and spatial variations of the frontal system of the Indian sector of the S.O. using remote sensing measurements of sea surface temperature (SST) and we present the first synoptic partitioning of the main physical-biogeochemical provinces. In the Crozet basin, if the signature of the fronts is well marked in the mesoscale distribution of the partial pressure of CO2 (pCO2), this latter hardly reflects the chlorophyll a (Chl a) distribution during the summer post-bloom period. Scaling in situ pCO2 measurements using remote sensing measurements of SST and Chl a, we assessed spring and summer air-sea flux of CO2 per physicalbiogeochemical province. Spring and summer air-sea CO2 fluxes in the Indian sector of the S.O. ranges from -0.048 PgC, to -0.057 PgC and -0.04 PgC in the North Subantarctic, South Subantarctic and Polar Frontal zones, respectively. A further collaborative effort was carried out applying a similar approach to the western Pacific sector of the S.O. Integrating CO2 fluxes over the year shows that this area acts as a sink for atmospheric CO2 of 0.08 PgC yr-1. Both studies provide lower estimates than the Takahashi et al. (Takahashi et al., 2002; Takahashi, 2003) climatology but corroborate (Metzl et al., 1999; Takahashi et al., 2002) the conclusions of inverse models, indicating that this climatology overestimates the CO2 sink in the S.O. (Gurney et al., 2004; Jacobson et al., 2005). We present a three years survey of pCO2 in Subantarctic coastal waters surrounding the Kerguelen Archipelago, with a particular attention on the role of Macrocystis giant kelp beds. Primary production of Macrocystis lasts from early spring to late autumn and is tightly linked to solar irradiance. Maximum net kelp community production can be as high as 15 gC m-2 d-1 at the solar irradiance climax. Such production strongly affects pCO2 within kelp bed. ...