HR: 10:40h
AN: OS22B-02 INVITED     [Abstracts]
TI: Equatorial Forcing of Annual SSH Signals off Western South America
AU: * Strub, P T
EM: tstrub@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, 104 COAS Admin Bldg Oregon State University, Corvallis, OR 97331-5503, United States
AU: Matano, R P
EM: rpm@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, 104 COAS Admin Bldg Oregon State University, Corvallis, OR 97331-5503, United States
AU: James, C
EM: corinne@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, 104 COAS Admin Bldg Oregon State University, Corvallis, OR 97331-5503, United States
AU: Palma, E D
EM: uspalma@criba.edu.ar
AF: Depto de Fisica, Universidad Nacional del Sur, Bahia Blanca, Argentina
AB: Results from previous modeling studies have shown that equatorial signals (ENSO) affect the interannual variability of the coastal ocean off western North America (the California Current). The specific case of the 1997- 98 El Niño is well documented with respect to the movement of the high sea surface height (SSH) signal from the equator to the California Current, using altimeter data. On the other hand, the annual cycle of SSH and circulation off western North America is thought to be controlled by the regional winds and heat fluxes at mid- latitudes. Off western South America (in the Humboldt Current), the connection between mid-latitude and equatorial coastal ocean is more direct than in the Northern Hemisphere. Both inter-annual and intra-seasonal signals at mid-latitudes (20°-30°S) have been traced to the equator. More recently, a semi- annual component of the seasonal cycle of the thermocline depth off northern Chile has been identified and hypothesized to originate at lower latitudes. In this study we use altimeter SSH and numerical models of the oceanic circulation off western South America to investigate the influence of equatorial dynamics on the annual cycle at mid-latitudes. A basin-scale numerical model of the circulation and SSH, forced by NCEP surface winds, is used to force regional models of ocean circulation off Peru and Chile, with boundary conditions that either include or exclude the basin-scale model's equatorial signals. Differences between the circulation off Peru and Chile under the two types of boundary conditions quantify the degree to which the seasonal cycles are controlled by distant forcing. In particular, a deep signal with a peak in austral winter appears to be driven by remote sensing, as is a shallow signal with a peak in austral summer. Altimeter and in situ data are used to verify the results.
DE: 4217 Coastal processes
DE: 4223 Descriptive and regional oceanography
DE: 4227 Diurnal, seasonal, and annual cycles (0438)
DE: 4512 Currents
DE: 4516 Eastern boundary currents
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly