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Revised predictions of long-period ocean tidal effects on Earth's rotation rateThe rotational response of Earth to long-period tidal forces, embodied in a 'zonal response function,' can be expected to vary with frequency because of variable contributions by the oceans, mantle, and core. The zonal response function has been estimated from 9 years of International Radio Interferometric Surveying (IRIS) universal time (UT1) data and compared with theoretical predictions, using a spherical harmonic tide model to compute the oceans' dynamic response, at semiannual, monthly, fortnightly, and 9-day lunisolar tidal frequencies. Different amounts of mantle anelasticity have been considered for both the oceanic and soild earth responses; predictions have been made assuming axial core-mantle coupling which is either complete or absent. Additionally, an extensive recalibration of the ocean model's frictional parameters was performed using constraints derived in part from Space92 polar motion data; zonal response function predictions have also been made employing this recalibrated ocean tide model. Our results indicate that any amount of core coupling can be ruled out at a fortnightly period and probably at a 9-day period, but not at a monthly period. Our results also suggest that the mantle responds purely elastically at a 9-day period but may behave increasingly anelastically at longer periods. A simple dispersive rule is postulated for periods ranging up to the 14-month Chandler wobble period.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Dickman, S. R.
(State University of New York, Binghampton, NY, United States)
Nam, Young S.
(University of Texas, Austin, TX United States)
Date Acquired
August 16, 2013
Publication Date
May 10, 1995
Publication Information
Publication: Journal of Geophysical Research
Volume: 100
Issue: B5
ISSN: 0148-0227
Subject Category
Accession Number
Funding Number(s)
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