Non-tidal oceanic excitation of nutation estimated from a barotropic ocean model

Author: A. Brzezinski, Rui M. Ponte and A.H. Ali
April 6, 2004
EGU General Assembly, Nice, France

Brzezinski, A., R.M. Ponte, and A.H. Ali, 2004. Non-tidal oceanic excitation of nutation estimated from a barotropic ocean model, EGU General Assembly, Nice, France, April 2004.

A new 7.5-year time series of ocean angular momentum with high temporal resolution (sampling interval 1 hour) calculated from a barotropic numerical model is used to study the influence of wind- and pressure-driven ocean signals on nutation. The only
significant contributions found are to the retrograde and prograde annual nutation waves, to the prograde semiannual wave and to the constant offset of the pole. The nontidal oceanic contributions are compared to the atmospheric influences derived
from the atmospheric angular momentum data. We perform detailed excitation balance of the prograde annual nutation excited by the Sun-synchronous S1 wave in the atmospheric and oceanic forcing, by taking into account the VLBI observation of
nutation. After removing the harmonic model from the excitation series, we consider separately the irregular remainders. An important question discussed here is how the dynamical response of the ocean to the atmospheric forcing differs within the
nutation frequency band from the two simple models applied so far, one assuming the "inverted barometer" response and the other one assuming the "rigid ocean" response.