HR: 09:45h
AN: OS51A-06    [Abstracts]
TI: Subarctic Ocean-Bottom-Pressure Oscillation and Its Link to the Tropical Pacific ENSO-Related Mass Oscillation
AU: * Song, Y
EM: Tony.Song@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Zlotnicki, V
EM: vz@pacific.jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: The Gravity Recovery and Climate Experiment (GRACE) satellites have observed strong ocean bottom pressure (OBP) signals in the high-latitudes, but data has been only available since their launch in May 2002. Here we also use a non-Boussinesq ocean model to simulate the OBP from 1948 to 2004 using NCEP/NCAR reanalysis data. It is found that the OBP time-series, from both GRACE and the model, have pronounced interannual variability signals, closely correlating with the Nino3.4 SST index. Such OBP oscillating features have not been reported before. Specifically: 1) There is a strong north-south OBP oscillation between the subarctic and subtropical gyres in the North Pacific Ocean. The bottom pressure difference between the two gyres is found to lead the Ni¤o3.4 index by more than 12 months with a correlation of 0.52 at the 99% significant interval. 2) There is also a moderate east-west OBP oscillation in the tropical Pacific. Unlike the subarctic oscillation, the bottom pressure difference between the eastern (Ni¤o3.4 region) and the western tropical Pacific (warm-pool region) is in phase with the Niño 3.4 index with a correlation 0.82. These two observations indicate ENSO has a direct effect on oceanic mass redistribution. Vorticity analysis leads to the explanation of a possible link between the north-south subarctic mass oscillation and the east-west tropical mass oscillation, due to the presence of bottom pressure torques, that contribute to the vorticity balance in the same sense as the wind stress curl. The subarctic OBP oscillation tends to decrease/increase the western boundary currents, adding/removing water mass in the western Pacific, consequently altering west-east pressure gradient along the Equator, and is probably a contributor or barotropic response of the onset/demise of El Niño. The GRACE and model results have been cross-verified by available TOPEX/Poseidon data and in-situ measurements.
DE: 4255 Numerical modeling
DE: 4522 El Ni¤o
DE: 4532 General circulation
DE: 4576 Western boundary currents
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly