Argentine and French Austral Atlantic Ocean Project

Project Description
The main hypothesis of the ARGAU program is that the Southern Atlantic
Ocean would be the ocean reacting the faster and more intensely to the
climatic change induced by the anthropogenic atmospheric CO2
increase. To evidence these changes, ARGAU, a long term (10 years)
program based on oceanographic cruises (summer and winter, from Buenos
Aires to the Weddell Sea) onboard the Argentinean Icebreaker ?
Almirante Irizar ? is carried out. In order to describe, explain and
model the trend and variability of CO2 fluxes in this area at various
time scale, the physico-chemical characterization of the different
water masses is being studied together with the biological communities
present in the water column, within a multidisciplinary approach.

The first two cruises were carried out between 20 March and 14 May,
2000 (ARGAU Zero) and 2 January-15 April, 2001 (ARGAU 1). Different
frontal structures are revealed by sea surface temperature and sea
surface salinity gradients: The Patagonian frontal shelf, the
Antarctic Circumpolar Current and the Malvinas cyclonic current. The
results of both cruises suggest that major part of the southwest
Atlantic Ocean appears as a CO2 sink. The strongest sink areas were
found around the Antarctic Peninsula (at 68?W) with a DPCO2 of
-80ppm. This strong sink is correlated to the highest fluorimetric
signal and chlorophyll-a concentration (around 4 mg.m-3) and
relatively low nitrate and phosphate concentrations (10 and 0.8 ?g.l-1
respectively). This could be explained by a bloom of Dactyliosolen
antarcticus (Castracane). The second strong sink observed at 56.5?W
with a DPCO2 of -40ppm is associated to the coldest temperature
(-1.8?C).