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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. C8, 3248, doi:10.1029/2002JC001396, 2003

Sources of global warming of the upper ocean on decadal period scales

Warren B. White

Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California, USA

Michael D. Dettinger

United States Geological Survey, San Diego, California, USA

Daniel R. Cayan

United States Geological Survey, San Diego, California, USA

Abstract

Recent studies find global climate variability in the upper ocean and lower atmosphere during the twentieth century dominated by quasi-biennial, interannual, quasi-decadal and interdecadal signals. The quasi-decadal signal in upper ocean temperature undergoes global warming/cooling of ∼0.1°C, similar to that occurring with the interannual signal (i.e., El Niño–Southern Oscillation), both signals dominated by global warming/cooling in the tropics. From the National Centers for Environmental Prediction troposphere reanalysis and Scripps Institution of Oceanography upper ocean temperature reanalysis we examine the quasi-decadal global tropical diabatic heat storage (DHS) budget from 1975 to 2000. We find the anomalous DHS warming tendency of 0.3–0.9 W m⁻² driven principally by a downward global tropical latent-plus-sensible heat flux anomaly into the ocean, overwhelming the tendency by weaker upward shortwave-minus-longwave heat flux anomaly to drive an anomalous DHS cooling tendency. During the peak quasi-decadal warming the estimated dissipation of DHS anomaly of 0.2–0.5 W m⁻² into the deep ocean and a similar loss to the overlying atmosphere through air-sea heat flux anomaly are balanced by a decrease in the net poleward Ekman heat advection out of the tropics of 0.4–0.7 W m⁻². This scenario is nearly the opposite of that accounting for global tropical warming during the El Niño. These diagnostics confirm that even though the global quasi-decadal signal is phase-locked to the 11-year signal in the Sun's surface radiative forcing of ∼0.1 W m⁻², the anomalous global tropical DHS tendency cannot be driven by it directly.

Received 18 March 2002; accepted 7 March 2003; published 5 August 2003.

Index Terms: 3339 Meteorology and Atmospheric Dynamics: Ocean/atmosphere interactions (0312, 4504); 4572 Oceanography: Physical: Upper ocean processes; 7536 Solar Physics, Astrophysics, and Astronomy: Solar activity cycle (2162); 1620 Global Change: Climate dynamics (3309).

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Citation: White, W. B., M. D. Dettinger, and D. R. Cayan (2003), Sources of global warming of the upper ocean on decadal period scales, J. Geophys. Res., 108(C8), 3248, doi:10.1029/2002JC001396.

Copyright 2003 by the American Geophysical Union.