Eddy transport of heat and thermocline waters in the North Pacific: A key to interannual/decadal climate variability?

High-resolution XBT transects in the North Pacific Ocean, at an average lat itude of 22 degreesN, are analyzed together with TOPEX/Poseidon altimetric data to determine the structure and transport characteristics of the mesosc ale eddy field. Based on anomalies in dynamic height, 410 eddies are identi fied in 30 transects from 1991 to 1999, including eddies seen in multiple t ransects over a year or longer. Their wavelength is typically 500 km, with peak-to-trough temperature difference of 2.2 degreesC in the center of the thermocline. The features slant westward with decreasing depth, by 0.8 degr ees of longitude on average from 400 m up to the sea surface. This tilt pro duces a depth-varying velocity/temperature correlation and hence a vertical meridional overturning circulation. In the mean, 3.9 Sv (Sv equivalent to 10(6) m(3) s(-1)) of thermocline waters are carried southward by the eddy f ield over the width of the basin, balanced mainly by northward flow in the surface layer. Corresponding northward heat transport is 0.086 +/- 0.012 pW . The eddy field has considerable variability on seasonal to interannual ti mescales. For the 8-yr period studied here, eddy variability was the domina nt mechanism for interannual change in the equatorward transport of thermoc line waters, suggesting a potentially important forcing mechanism in the co upled air-sea climate system.