ZONATION OF NEAR-SURFACE DRAKE PASSAGE WATERS BASED ON

PAPARAZZO, F.E.; SCHLOSS, I.R.; ALDER, V.A.; ESTEVES, J.L.

BUENOS AIRES

Simposio; 4th OPEN SCIENCE CONFERENCE-SCAR; 2010

Scientific Committee on Antarctic Research

The objective of the present work was to study the near-surface expression of the different limits and zones previously defined for the Drake Passage. A pool of 382 nearsurface samples obtained during four summer-fall cruises (2001-2004) of the joint Argentinean-French “Argau” project on board the “Almirante Irizar” in the Drake Passage was analyzed. Nitrate, phosphate, silicate, temperature, salinity and chlorophyll-a data were considered in a Multivariate Discriminant Function Analysis (MDFA) to construct the discriminant matrix, and a random sample of 25% of these data was used to verify the model. The main near-surface detectable limits were the slope of the South American continental shelf (3,000 m isobath), the Polar Front and the Southern Antarctic Circumpolar Current Front. Variability was further interpreted upon dividing data into summer and fall. In summer, the MDFA showed a 90.6% of concordance between expected/observed zones (Wilks´ Lambda: 0.08; p<0.001) while the fall MDFA showed a 92.8% of concordance (Wilks´ Lambda: 0.03; p<0.001). Although the zones and limits were the same for both seasons, nitrate, silicate and chlorophyll-a ruled summer variations, whereas silicate, chlorophyll-a, temperature and salinity ruled fall variation. These results are expected to contribute to the understanding of biological processes such as primary production and species distribution in surface waters of the Drake Passage.