Wednesday 24 August 2005

P4
1550-1710 hours

315
ARGO float observation of Antarctic Intermediate Water
Barker, Paul¹, Karsten, Richard¹, Freeland, Howard²
1 Acadia University, Wolfville, NS, Canada
2 Institute of Ocean Sciences
Author email: paul.barker@acadiau.ca
Antarctic Intermediate Water (AAIW) is the low salinity water mass found between 800 and 1000 metres depth throughout most of the southern hemisphere and in the northern hemisphere tropics of all oceans. AAIW is primarily formed in the southeast Pacific, where the densest and freshest of the circumpolar deep mixed layers exist. The formation process occurs largely in the austral winter when the cool atmospheric temperatures and deep mixed layers are conducive to deep convection. Observation of the formation of AAIW has been extremely limited due to the prohibitive weather conditions during the austral winter. To address this shortcoming 6 Canadian floats were deployed off southern Chile close to the formation region of AAIW in December 2002, there are now over 100 floats in the Southeastern Pacific Ocean. They are designed to drift at a depth of about 2000 metres, well below the maximum extent of the AAIW mass, and profile to the surface every 10 days. Following an ascent the floats transmit temperature and salinity observations via the satellites forming the Service ARGOs constellation and then return to the 'parking depth'. In this presentation, we present our initial analysis of the data from the Southern Pacific Ocean floats. The data includes a complete seasonal cycle allowing us to describe the hydrography of the region during the austral winter. And, we have also begun to identify water mass properties. We have determined the circulation pattern of AAIW in the South Pacific Ocean and are currently analysing how surface waters might waters might sink to depth to form AAIW.

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