An Observational Estimate of Inferred Ocean Energy Divergence.pdf

1 An Observational Estimate of Inferred Ocean Energy Divergence Kevin E. Trenberth and John T. Fasullo email: trenbert@ National Center for Atmospheric Research1 P. O. Box 3000 Boulder, CO 80307 6 June 2007 J. Phys. Oceanogr 1 The National Center for Atmospheric Research is sponsored by the National Science Foundation. 2 Abstract Monthly net surface energy fluxes (FS) over the oceans are computed as residuals of the atmospheric energy budget using top-of-atmosphere (TOA) net radiation (RT) and the complete energy budget tendency and divergence for the atmosphere (??FA). The focus is on TOA radiation from ERBE (February 1985 to April 1989) and CERES (March 2000 to May 2004) combined with results from two atmospheric reanalyses and three ocean datasets that enable a comprehensive estimate of uncertainties. An analysis of FS departures from the annual mean and the implied annual cycle in “equivalent ocean energy content” is compared with directly observed ocean energy content (OE) and tendency (δOE/δt) to reveal the inferred annual cycle of divergence (??FO). In the extratropics, FS dominates δOE/δt although supplemented by ocean Ekman transports that enhance the annual cycle in OE. In contrast, in the Tropics, ocean dynamics dominate OE variations throughout the year in association with the annual cycle in surface wind stress and the North Equatorial Current. An analysis of the regional characteristics of the first joint Empirical Orthogonal Function (EOF) of FS, δOE/δt, and ??FO is presented, and the largest sources of uncertainty are attributed to OE. The mean and annual cycle of zonal mean global ocean transports is estimated and compared with observations. Agreement is reasonable except in the North Atlantic, where transports from the transects are greater than the estimates presented here - a difference that exceeds the uncertainty bounds established herein. 3 1. Introduct