HR: 14:00h
AN: OS43A-01    [Abstracts]
TI: Spin-up of South Pacific Subtropical Gyre Freshens and Cools the Upper Layer of the Eastern South Pacific Ocean
AU: * Schneider, W
EM: wschneid@udec.cl
AF: Universidad de Concepción, Departamento de Oceanografía and Centro de Investigación Oceanográfica en el Pacifico Sur-Oriental, COPAS, Chile, Barrio Universitario S/N, Cabina 9, Cassila 160-C, Concepción, Chile
AU: Fukasawa, M
EM: fksw@jamstec.go.jp
AF: Institute of Observational Research for Global Change, IORGC, Japan Agency for Marine- Earth Science and Technology, JAMSTEC, Japan, 2-15 Natsushima, Yokosuka 237-0061, Japan
AU: Garcés-Vargas, J
EM: jgarces@udec.cl
AF: Universidad de Concepción, Departamento de Oceanografía and Centro de Investigación Oceanográfica en el Pacifico Sur-Oriental, COPAS, Chile, Barrio Universitario S/N, Cabina 9, Cassila 160-C, Concepción, Chile
AU: Bravo, L
EM: lbravo@copas.udec.cl
AF: Universidad de Concepción, Departamento de Oceanografía and Centro de Investigación Oceanográfica en el Pacifico Sur-Oriental, COPAS, Chile, Barrio Universitario S/N, Cabina 9, Cassila 160-C, Concepción, Chile
AB: The general circulation in the South Pacific Ocean is dominated by the subtropical gyre, which manifests itself through elevated mean dynamic topography at its center. Gyre circulation consists of the westward South Equatorial Current, a narrow poleward western boundary current, the East Australian current, the eastward South Pacific Current streaming along the South Tropical Front (centered at around 40°S in the western ocean basin and at 30-35°S in the eastern basin), and the Humboldt Current System, a broad equatorward eastern boundary current, (in the literature, also referred to as the Peru/Chile Current) (Tomczak and Godfrey 1994; Levitus 1982; Reid 1986). The volume transport of upper water (700 m) between the Pacific coast of South America and the East Pacific Rise amounted to 18 Sv across 32.5°S (WOCE section P06) and 14 Sv across 17°S (WOCE section P21) (Tsimplis et al. 1998), emphasizing the importance of equatorward transport by this eastern boundary current system. This boundary current also plays a vital role in the fresh water budget by advecting fresher Subantarctic Surface Water northward thus forming Eastern South Pacific Transition Water (Emery and Meincke 1986). Here, temperature and salinity from the upper 200 m of the water column in the South Pacific Ocean were compared basin wide along 32°30'S between 2003 and 1992, based on two vertically and horizontally high resolution hydrographic repeat-sections involving 227 station pairs (WOCE, BEAGLE). Additionally, the seasonal cycles of the upper water column temperature and salinity between 90- 140°W and 30-35°S were established utilizing more than 1500 ARGO profiles from 2003 to 2006. The surface waters (0-200 m) of the eastern South Pacific Ocean, on average and seasonally adjusted, were clearly fresher in 2003 by 0.14 PSU. The seasonally adjusted, depth integrated temperature was 0.25°C colder in the same region. We further concluded a spin-up of the South Pacific subtropical gyre circulation since the fading of the 1997/98 El Niño, as referred from observations of satellite-born mean sea level anomalies, caused by intensified wind stress over the South Pacific. We relate the observed temperature and salinity changes in the eastern South Pacific to a spin-up of the subtropical gyre circulation caused by intensified winds.
DE: 4500 OCEANOGRAPHY: PHYSICAL
DE: 4513 Decadal ocean variability (1616, 1635, 3305, 4215)
DE: 4516 Eastern boundary currents
DE: 4532 General circulation (1218, 1222)
DE: 4572 Upper ocean and mixed layer processes
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly