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Evidence for Excitation of Polar Motion by Fortnightly Ocean TidesThe second-degree zonal tide raising potential, which is responsible for tidal changes in the Earth's rotation rate and length-of-day, is symmetric about the polar axis and hence can excite the Earth's polar motion only through its action upon nonaxisymmetric features of the Earth such as the oceans. Ocean tidal excitation of polar motion in the diurnal and semidiurnal tidal bands has been previously detected and examined. Here, the detection of ocean tidal excitation of polar motion in the long-period tidal band, specifically at the Mf' (13.63-day) and Mf (13.66-day) tidal frequencies, is reported. Spectra of the SPACE94 polar motion excitation series exhibit peaks at the prograde and retrograde fortnightly tidal periods. After removing effects of atmospheric wind and pressure changes, an empirical model for the effect of the fortnightly ocean tides upon polar motion excitation is obtained by least-squares fitting periodic terms at the Mf and Mf' tidal frequencies to the residual polar motion excitation series. The resulting empirical model is then compared with the predictions of two hydrodynamic ocean tide models.
Document ID
19990014560
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Gross, Richard S. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Hamdan, Kamal H. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Boggs, Dale H. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Date Acquired
August 19, 2013
Publication Date
July 1, 1996
Publication Information
Publication: Geophysical Research Letters
Volume: 23
Issue: 14
ISSN: 0094-8534
Subject Category
Oceanography
Report/Patent Number
Paper 96GL01596
Distribution Limits
Public
Copyright
Other