Global ocean circulation and mass fields and the Earth’s variable rotation

Author: Rui M. Ponte, D. Stammer and C. Wunsch
November 5, 2002
WOCE and Beyond, San Antonio

Ponte, R.M., D. Stammer, and C. Wunsch, 2002. Global ocean circulation and mass fields and the Earth’s variable rotation, WOCE and Beyond, San Antonio, November 2002.

Advances in modeling and observational capabilities occurring in recent years as part of the WOCE legacy have made possible the realistic determination of the ocean circulation and mass fields on a global scale. With the ability to calculate these time varying fields came the opportunity to study globally integrated quantities such as ocean angular momentum (OAM). Global estimates of sea level, density, and horizontal currents are used to show that improved OAM estimates are being obtained from advanced ocean state estimation methods. Comparisons with independent Earth rotation data demonstrate the good quality of OAM estimates and reveal the importance of OAM variability in explaining observed signals in length of day and polar motion. The equatorial components of OAM are particularly relevant for the planet's rotation budget and can account for a major part of the Chandler and seasonal wobble excitation, thus providing an answer to a long standing unsolved problem in geophysics. Results point to the value of combining satellite altimetry and gravity data, Earth rotation data, and ocean models to address various oceanographic and geodetic research questions in the future.