HR: 15:45h
AN: OS52K-06    [PDF]
TI: Decadal Variations of the Tropical Pacific Pycnocline Water Mass Properties
AU: * Zhang, D
EM: dongxiao.zhang@noaa.gov
AF: NOAA / Pacific Marine Environmental Laboratory and JISAO / University of Washington, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AU: McPhaden, M J
EM: michael.j.mcphaden@noaa.gov
AF: NOAA / Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AB: Some theoretical and modeling studies suggest that changes in water mass properties of the tropical Pacific pycnocline are responsible for the decadal modulation of ENSO and basin scale ENSO-like Pacific Decadal Variability. However, these studies are limited by the lack of observational evidence for possible water mass changes in the tropical Pacific pycnocline. In this study we investigate these changes using 50-years of hydrographic data formed by the combination of NODC World Ocean Database 2001, WOCE sections, some newly available Argo float profiles, and PMEL CTD data collected from ships servicing TAO moorings. Decadal time scale density compensated temperature anomalies are evident in the equatorial Pacific pycnocline with standard deviations of 7-year low-passed anomalies in the western, central, and eastern basins of 0.11, 0.08, and 0.23 \deg C respectively. The signature of the 1976/77 regime shift is visible in the eastern basin with positive anomalies in the 1980s and 1990s and negative anomalies before. These pycnocline anomalies are highly correlated with the SST anomalies, both of which show an approximate 0.8 \deg C increase from the 1970s to the 1990s. We will discuss the relative importance of advection from higher latitudes by the mean circulation of the subtropical cells vs local circulation changes and equatorial mixing processes in generating these equatorial pycnocline anomalies. We will also discuss the implications of these results for theories of Pacific decadal variability.
DE: 4215 Climate and interannual variability (3309)
DE: 4279 Upwelling and convergences
DE: 4283 Water masses
DE: 4504 Air/sea interactions (0312)
DE: 4522 El Ni¤o
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting