The Rotation of the Earth: A Geophysical Discussion

Munk, Walter; MacDonald, Gordon J. F.; Arons, A. B.

doi:10.1119/1.10629

Cited by 171 publications

(281 citation statements)

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“…This is especially the case as the variation in J 2 and polar wander are dependent upon completely independent elements of the Earth's moment of inertia tensor [e.g., Munk and Macdonald, 1960;Peltier and Luthcke, 2009]. In models of the GIA process, which are able to simultaneously fit these two rotational anomalies, variations in the elements of the moment of inertia tensor of the planet are determined by a specific model of time-dependent continental ice-sheet loading and of the depth-dependence of mantle viscosity.…”

Section: Discussionmentioning

confidence: 99%

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process?

Roy

Peltier

2011

Geophys. Res. Lett.

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Recent trends in the two primary anomalies in the rotational state of the planet are analyzed in detail, namely those associated with the speed and direction of polar wander and with the non‐tidal acceleration of the rate of axial rotation (via the measurement of the changing oblateness of the Earth's shape). It is demonstrated that a significant change in the secular trends in both of these independent parameters became evident subsequent to approximately 1992. It is suggested that both parameters might have come to be substantially influenced by mass loss from both the great polar ice sheets, and from the very large number of small ice‐sheets and glaciers that are also being influenced by the global warming phenomenon. The modern values for the secular drifts in those parameters that we estimate are appropriate to the period during which measurements have been made by the satellites of the Gravity Recovery and Climate Experiment (GRACE). These changes in secular rates might greatly assist in understanding why the GRACE‐inferred values of the time derivatives of the degree two and order one Stokes coefficients differ so significantly from those associated with Late Quaternary ice‐age influence.

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Section: Discussionmentioning

confidence: 99%

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process?

Roy

Peltier

2011

Geophys. Res. Lett.

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“…[11] The equatorial components of the atmospheric angular momentum (AAM) available for transfer to the solid [12] Here we consider only the excitation pressure term modified by the isostatic, inverted barometer (IB) response of the oceans [Munk and Mac Donald, 1960]. The IB effect of the ocean does not entirely cancel out the temporal atmosphere pressure variation over the ocean, but it adjusts the atmospheric surface pressure to the mean atmospheric surface pressure over the world oceans.…”

Section: Methodsmentioning

confidence: 99%

Patterns of atmospheric excitation functions of polar motion from high‐resolution regional sectors

2009

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[1] In this paper regional values of equatorial components of the atmospheric excitation function of polar motion, which are proportional to the equatorial components of angular momentum (AAM), were computed at high spatial resolution in 3312 equal-area sectors from the surface pressure fields of the NCEP-NCAR reanalyses in order to improve our knowledge of patterns of atmospheric excitation functions of polar motion. The inverted barometer (IB) model of oceanic isostatic adjustment is applied to readjust the effective atmospheric pressure fields. To identify the influence of different geographic regions of the atmosphere on the excitation of polar motion, correlations and covariances between these regional excitations values and either the global geodetic excitation function, determined from the geodetic observational data, or the atmospheric excitation functions, equivalent to the sum of such excitations in all regions, were computed in different spectral bands, from subseasonal to interannual period ones. The covariances show the regional contribution to the global excitation, whereas the correlations show an overall similar relationship. Furthermore, these analyses determine regional sources of polar motion excitation by surface pressure variations in the atmosphere in different spectral bands. The broad regions over Eurasia and North America were identified as principal atmospheric excitation sources for polar motion. The results revealed that atmospheric excitation over land regions in the northern middle latitudes, especially over Asia, is exceptionally strong, a point generally noted in previous studies, though without identifying detailed features. Over the Himalayan Mountains the covariance of local with global atmospheric excitation in the annual band forms a small minimum surrounded by larger values in a ring-like formation. For other terms, maxima of atmospheric excitation have a longitudinal formation mostly across the Eurasian continent. The atmospheric excitation of polar motion over the ocean is weak when subject to the IB correction, but it contains nevertheless a clear annual signal and is highly correlated with the annual oscillation of the global geodetic excitation function of polar motion.

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“…Much of the existing analysis in the literature [e.g., Jeffreys, 1916;Munk and Macdonald, 1960] treats the ocean as homogeneous N = 0, and for many purposes, this limit is sufficient. However, the ocean is almost everywhere stratified, and a theory of the response to atmospheric load of a stratified ocean should reduce properly to that for a homogeneous ocean where the limit is appropriate.…”

Section: P00zmentioning

confidence: 99%

Atmospheric loading and the oceanic “inverted barometer” effect

Wunsch¹,

Stammer²

1997

Reviews of Geophysics

352

241

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Abstract. The response of the ocean to fluctuating atmospheric pressure loads is reviewed in theory and in observations. Major theoretical issues lie primarily with oceanic boundary reflectivity and with rates of dissipation, generally. Analytical solutions for a stratified ocean show that a static ("inverted barometer") response is anticipated at all frequencies and wavenumbers not coincident with certain dispersion curves. Nonstatic behavior of two types is predicted: zero motion of the sea surface and a resonant response. Two types of resonance emerge. The first type corresponds to barotropic modes which are long gravity waves or Rossby waves at high and low frequencies, respectively. The second type excites internal modes, either gravity waves or Rossby waves depending on frequency, but modified from a conventional resonant response by the immediate juxtaposition in frequency/wavenumber space of the rigid-lid modes. The extent to which these actual resonances are generated is obscure owing to the same uncertainties about oceanic dissipation and scattering which affect all other forced oceanic motions, especially including the tides and other barotropic motions. Zero sea surface motion is predicted at frequencies and wavenumbers corresponding to "rigid-lid" modes. Observations support the wide applicability of the static response except in the tropics and in the western boundary current extension regions; there, the signal-to-noise ratios may be inadequate. The only other known clear nonstatic response occurs near 5 days in the Pacific and South Atlantic Oceans, indicative of a low-Q resonance in the former area and a forced nonresonant response in the latter, but there are remaining problems with these interpretations. INTRODUCTIONOceanic motions are a response directly, or indirectly through internal instabilities, to external forcing functions, including tides and a variety of atmospheric exchanges including momentum (wind stress) and buoyancy, and to pressure loading. Because of the immediate connection to oceanic vorticity dynamics, most attention has focused on responses to wind stress and, more recently, to those of buoyancy forcing.Until now, the reaction of the ocean to atmospheric pressure loading was of interest primarily to those studying tides and sea level variations in tide gauge records [e.g., Groves and Hannan, 1968] and the changes in the Earth's rotation owing to atmospheric fluctuations [e.g., Lambeck, 1980]. Most of the earliest work was directed at removing meteorological effects from tide gauge data to improve tidal forecasting and produce better mean sea level values for geodetic surveying. The advent of high-precision satellite altimetry has rendered the subject of much broader interest because of the global geographic coverage. Atmospheric forcing spans all observable frequencies and wavenumbers and varies geographically. The ocean in turn exhibits a wide variety of physical responses as a function of frequency, wavenumber, and geography; the ability to understand exactly how the oce...

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The Rotation of the Earth: A Geophysical Discussion

Cited by 171 publications

References 0 publications

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process?

GRACE era secular trends in Earth rotation parameters: A global scale impact of the global warming process?

Patterns of atmospheric excitation functions of polar motion from high‐resolution regional sectors

Atmospheric loading and the oceanic “inverted barometer” effect

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