OCEANIC SIGNALS IN OBSERVED MOTIONS OF THE EARTHS POLE OF ROTATION

Motion of the Earth's pole of rotation relative to its crust, commonly referred to as polar motion, can be excited by a variety of geophysic al mechanisms(1), In particular, changes in atmospheric wind and mass fields have been linked to polar motion over a wide range of timescale s, but substantial discrepancies remain between the atmospheric and ge odetic observations(1-4). Here we present results from a nearly global ocean model which indicate that oceanic circulation and mass-field va riability play important roles in the excitation of seasonal to fortni ghtly polar motion. The joint oceanic and atmospheric excitation provi des a better agreement with the observed polar motion than atmospheric excitation alone. Geodetic measurements may therefore be used to prov ide a global consistency check on the quality oi simulated large-scale oceanic fields.