Secular trend of the Earth's rotation pole: Consideration of motion of the latitude observatories

Abstract

Secular polar motion has been recorded in ILS data over the past 75 years, an amount greater by a factor of ten than the 'true polar wandering' deduced from paleomagnetic data. In this work, the possibility that the secular trend is an observational artifact of the continental drift of the ILS stations is directly examined by consideration of several absolute plate velocity models earlier proposed by Minster et al.(1 974), Kaula (1 9 7 9 , and Solomon, Sleep & Richardson (1975). The assumptions underlying those models are discussed; in general, the absolute velocity models are more likely to be valid when geologically short timescales are considered.The corrections to the ILS data due to the stations' motion fail by an order of magnitude to explain the ILS trend; even by taking into account possible plate hyperactivity and non-rigidity, the corrections could explain no more than 30 per cent of the trend. The corrections are small because the absolute plate velocities of North America and Eurasia are small and primarily east-west. Consequently, the rotation pole is undergoing significant motion of its own relative to the surface of the Earth.The Kimura z term found by the ILS observations provides an independent means of estimating the relative motion between Eurasia and North America. It also contains other geophysical information; the 7.5-yr periodicity discovered by Naito & Ishii (1 974) may be widespread.Lastly, tectonically induced changes in the zenith direction, such as at Mizusawa, are probably too small to be detected, contrary to earlier proposals.

Glaciation‐induced perturbations in the Earth's rotation: A new appraisal

“…and the Earth's rotation generally assumed' that the observed signals [e.g., Curroll 1966; Dickman, 1977] were due exclusively to the rebound process, and the primary aim of these studies was to infer the radial pro- In the last few years, attempts to constrain the signal from ongoing melting events has continued to be 985 an active area of study. Trupin et al [1992].have considered, in detail, the contribution to both J2 and polar wander from the mass balance of sinall ice sheets and glaciers over the period [1965][1966][1967][1968][1969][1970][1971][1972][1973][1974][1975][1976][1977][1978][1979][1980][1981][1982][1983][1984].…”

Postglacial variations in the level of the sea: Implications for climate dynamics and solid‐Earth geophysics

“…The unambiguous connection between this polar wander and the GIA process was first established by Peltier [1982] and Wu and Peltier [1984], whose detailed theoretical analysis, since further generalized by Peltier and Jiang [1996a], showed that the initial analysis of the GIA effect provided by Munk and MacDonaM [1960] did not, in fact, rule out a significant ongoing wander due to this cause, as they had imagined, even though the surface mass load during the present interglacial period is very nearly time invariant. The analysis of the data by Dickman [1977] has now also been performed by many others, and their results are all compiled on Figure 12b. Also shown on Figure 12b is the result of an additional measurement based upon VLBI data by Carter et al [1986].…”

“…What is of greatest interest from the sea level perspective, however, as we shall see, is the slow secular drift of the pole upon which these oscillatory variations are superimposed. According to Dickman [1977] this "truepolar wander" is occurring at a rate near 0.95 ø per million years along the 76øW meridian as shown on the inset polar projection. The unambiguous connection between this polar wander and the GIA process was first established by Peltier [1982] and Wu and Peltier [1984], whose detailed theoretical analysis, since further generalized by Peltier and Jiang [1996a], showed that the initial analysis of the GIA effect provided by Munk and MacDonaM [1960] did not, in fact, rule out a significant ongoing wander due to this cause, as they had imagined, even though the surface mass load during the present interglacial period is very nearly time invariant.…”

Changes in rotation induced by Pleistocene ice masses with stratified analytical Earth models

“…This limits the concept of TPW to periods of about 100 Myr, and one should be careful not to misinterpret a redistribution of hot spots during plate reorganization periods as a "catastrophic turnover" of the rotation axis. Apart from this, there is evidence of TPW on both timescales of millions of years [Besse and Courtillot, 1991] and thousands of years [Dickman, 1977] Other uncertainties that accompany deriving radial viscosity profiles from rotational studies are the neglect of lateral viscosity variations and uncertainties in the load history of the Pleistocene ice models. There are reasons, however, that these will affect the results to a lesser extent.…”

“…The observational data considered in our analysis are taken from Dickman [1977] and McCarthy and Luzum hot spots is still a matter of debate, one could associate them with more or less stationary mantle convection patterns. This would imply that whenever a large change of the global convection pattern emerges, being accompanied by a large reorganization of the plates, then the concept of true polar wander becomes meaningless as the hot spot reference frame is destroyed or reorganized.…”