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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, C08004, doi:10.1029/2004JC002511, 2005

Upper ocean heat and freshwater budgets in the eastern Pacific warm pool

Hemantha W. Wijesekera

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA

Daniel L. Rudnick

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

Clayton A. Paulson

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA

Stephen D. Pierce

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA

W. Scott Pegau

Kachemak Bay Research Reserve, Homer, Alaska, USA

John Mickett

Applied Physics Laboratory, University of Washington, Seattle, Washington, USA

Michael C. Gregg

Applied Physics Laboratory, University of Washington, Seattle, Washington, USA

Abstract

This study focuses on upper ocean budgets of heat and freshwater, which yield estimates of net surface heat flux and rainfall minus evaporation. The budgets are based on a 19 day ship survey conducted as part of the Eastern Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System 2001 in September 2001. Underway measurements included temperature and salinity sections from an undulating platform, SeaSoar, and horizontal currents from an acoustic Doppler current profiler along a 146 × 146 km survey pattern centered near 10°N, 95°W in the eastern Pacific warm pool. Additional measurements from a second ship at the center of the survey pattern included radar backscatter from rainfall, air-sea fluxes, and vertical profiles of temperature, salinity, microstructure, and horizontal velocity. Satellite measurements of surface height, temperature, and rainfall were also analyzed. The heat budget of 20 and 25 m surface layers indicated that storage, advection, turbulent transport, and penetrative solar radiation were all significant components of the heat budget with a net surface cooling of 41 W m⁻² estimated as a residual, which agreed with atmospheric measurements (30 W m⁻²). The precipitation rate from the freshwater budget was 29 mm d⁻¹, which was in excellent agreement with in situ measurements on both ships and in good agreement with satellite estimates for the same period. Lateral transports of heat and salt were influenced by an anticyclonic eddy in the survey area, and it is suggested that anticyclonic eddies, which form near the Central American coast, may carry anomalously warm sea surface temperature toward the west and become preferential sites for heavy rainfall.

Received 28 May 2004; accepted 18 March 2005; published 11 August 2005.

Keywords: heat and freshwater budgets; eastern Pacific warm pool; air-sea interaction; warm eddies and convection; rainfall; Costa Rica dome.

Index Terms: 3339 Atmospheric Processes: Ocean/atmosphere interactions (0312, 4504); 4231 Oceanography: General: Equatorial oceanography; 4504 Oceanography: Physical: Air/sea interactions (0312, 3339); 4520 Oceanography: Physical: Eddies and mesoscale processes; 4572 Oceanography: Physical: Upper ocean and mixed layer processes.

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Citation: Wijesekera, H. W., D. L. Rudnick, C. A. Paulson, S. D. Pierce, W. S. Pegau, J. Mickett, and M. C. Gregg (2005), Upper ocean heat and freshwater budgets in the eastern Pacific warm pool, J. Geophys. Res., 110, C08004, doi:10.1029/2004JC002511.

Copyright 2005 by the American Geophysical Union.