Core Eigenmodes and their Impact on the Earth’s Rotation

Abstract Changes in the Earth’s rotation are deeply connected to fluid dynamical processes in the outer core. This connection can be explored by studying the associated Earth eigenmodes with periods ranging from nearly diurnal to multi-decadal. It is essential to understand how the rotational and fluid core eigenmodes mutually interact, as well as their dependence on a host of diverse factors, such as magnetic effects, density stratification, fluid instabilities or turbulence. It is feasible to build detailed models including many of these features, and doing so will in turn allow us to extract more (indirect) information about the Earth’s interior. In this article, we present a review of some of the current models, the numerical techniques, their advantages and limitations and the challenges on the road ahead.

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Reconciling past changes in Earth’s rotation with 20th century global sea-level rise: Resolving Munk’s enigma

Science Advances ◽

10.1126/sciadv.1500679 ◽

2015 ◽

Vol 1 (11) ◽

pp. e1500679 ◽

Cited By ~ 24

Author(s):

Jerry X. Mitrovica ◽

Carling C. Hay ◽

Eric Morrow ◽

Robert E. Kopp ◽

Mathieu Dumberry ◽

...

Keyword(s):

Sea Level ◽

20Th Century ◽

Outer Core ◽

Ice Age ◽

Earth’S Rotation ◽

Momentum Exchange ◽

Earth's Rotation ◽

Isostatic Adjustment ◽

Eclipse Observations ◽

Global Sea Level

In 2002, Munk defined an important enigma of 20th century global mean sea-level (GMSL) rise that has yet to be resolved. First, he listed three canonical observations related to Earth’s rotation [(i) the slowing of Earth’s rotation rate over the last three millennia inferred from ancient eclipse observations, and changes in the (ii) amplitude and (iii) orientation of Earth’s rotation vector over the last century estimated from geodetic and astronomic measurements] and argued that they could all be fit by a model of ongoing glacial isostatic adjustment (GIA) associated with the last ice age. Second, he demonstrated that prevailing estimates of the 20th century GMSL rise (~1.5 to 2.0 mm/year), after correction for the maximum signal from ocean thermal expansion, implied mass flux from ice sheets and glaciers at a level that would grossly misfit the residual GIA-corrected observations of Earth’s rotation. We demonstrate that the combination of lower estimates of the 20th century GMSL rise (up to 1990) improved modeling of the GIA process and that the correction of the eclipse record for a signal due to angular momentum exchange between the fluid outer core and the mantle reconciles all three Earth rotation observations. This resolution adds confidence to recent estimates of individual contributions to 20th century sea-level change and to projections of GMSL rise to the end of the 21st century based on them.

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The Excess Secular Change in the Obliquity of the Ecliptic and its Relation to the Internal Motion of the Earth

International Astronomical Union Colloquium ◽

10.1017/s0252921100028281 ◽

1971 ◽

Vol 9 ◽

pp. 171-181

Author(s):

Shinko Aoki ◽

Chuichi Kakuta

Keyword(s):

Coupling Coefficient ◽

Internal Motion ◽

Secular Change ◽

Earth’S Rotation ◽

View Point ◽

Earth's Rotation ◽

A Value ◽

The Earth ◽

Fluid Core

AbstractCriticisms of the senior author’s paper (1967) are examined, and it is found that there still seems to be a possibility that the cause of the excess secular change is in the mantle-core coupling. Part II is devoted to an improvement of the previous result (Aoki, 1969) using a model of the elastic mantle and fluid core. In order to give the observed value of excess secular change of the obliquity, a value of the coupling coefficient of the Earth’s rotation is 3.5 times larger than Rochester’s (1968) value is required. This is not impossible from the geophysical view-point. In fact, if we take into account Hide’s argument (1969), then the coupling coefficient will be much larger than the present geophysical value.

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Flow in the fluid core and Earth’s rotation

Earth Rotation: Solved and Unsolved Problems ◽

10.1007/978-94-009-4750-4_17 ◽

1986 ◽

pp. 241-258 ◽

Cited By ~ 6

Author(s):

C. Gire ◽

J. L. Mouël

Keyword(s):

Earth’S Rotation ◽

Earth's Rotation ◽

Fluid Core

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Zonal and tesseral harmonic perturbations of an artificial satellite

Symposium - International Astronomical Union ◽

10.1017/s0074180900105625 ◽

1966 ◽

Vol 25 ◽

pp. 323-325 ◽

Cited By ~ 1

Author(s):

B. Garfinkel

Keyword(s):

Angular Velocity ◽

Spherical Harmonics ◽

Artificial Satellite ◽

Compact Form ◽

Earth’S Rotation ◽

Earth's Rotation ◽

Secular Variations ◽

Tesseral Harmonics

The paper extends the known solution of the Main Problem to include the effects of the higher spherical harmonics of the geopotential. The von Zeipel method is used to calculate the secular variations of orderJmand the long-periodic variations of ordersJm/J2andnJm,λ/ω. HereJmandJm,λare the coefficients of the zonal and the tesseral harmonics respectively, withJm,0=Jm, andωis the angular velocity of the Earth's rotation. With the aid of the theory of spherical harmonics the results are expressed in a most compact form.

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