What drives 20th century polar motion?

Adhikari, Surendra; Caron, Lambert; Steinberger, Bernhard; Reager, J. T.; Kjeldsen, Kristian K.; Marzeion, Ben; Larour, Eric; Ivins, E. R.

doi:10.1016/j.epsl.2018.08.059

Cited by 44 publications

(48 citation statements)

References 71 publications

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“…To suitably interpret the (l, m) = (2, ±1) symmetry, it is worth to note that according to our computations, the GIA-induced polar motion presently occurs at a rate of ∼1.4 deg/Myr (roughly corresponding to 15 cm/year on the Earth's surface) along the meridian ∼80 • W (roughly, towards the Hudson Bay). Such rate and direction of polar drift match well the astronomical observations in the course of last century (see e.g., Lambeck [4]) and with recent analyses about the causes of secular polar motion [66]. Performing a further run of SELEN 4 in which we have adopted the traditional rotation theory (see e.g., Spada et al [46]), we have verified that the (l, m) = (2, ±1) pattern ofĠ(ω) would be indeed much stronger, with a more than two-fold rate of polar drift of ∼3.5 deg/Myr in the same direction.…”

Section: Geoid Height and Absolute Sea-level Changesupporting

confidence: 88%

On Some Properties of the Glacial Isostatic Adjustment Fingerprints

Spada¹,

Melini²

2019

Water

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Along with density and mass variations of the oceans driven by global warming, Glacial Isostatic Adjustment (GIA) in response to the last deglaciation still contributes significantly to present-day sea-level change. Indeed, in order to reveal the impacts of climate change, long term observations at tide gauges and recent absolute altimetry data need to be decontaminated from the effects of GIA. This is now accomplished by means of global models constrained by the observed evolution of the paleo-shorelines since the Last Glacial Maximum, which account for the complex interactions between the solid Earth, the cryosphere and the oceans. In the recent literature, past and present-day effects of GIA have been often expressed in terms of fingerprints describing the spatial variations of several geodetic quantities like crustal deformation, the harmonic components of the Earth’s gravity field, relative and absolute sea level. However, since it is driven by the delayed readjustment occurring within the viscous mantle, GIA shall taint the pattern of sea-level variability also during the forthcoming centuries. The shapes of the GIA fingerprints reflect inextricable deformational, gravitational, and rotational interactions occurring within the Earth system. Using up-to-date numerical modeling tools, our purpose is to revisit and to explore some of the physical and geometrical features of the fingerprints, their symmetries and intercorrelations, also illustrating how they stem from the fundamental equation that governs GIA, i.e., the Sea Level Equation.

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Section: Geoid Height and Absolute Sea-level Changesupporting

confidence: 88%

On Some Properties of the Glacial Isostatic Adjustment Fingerprints

Spada¹,

Melini²

2019

Water

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“…(ii) It is argued that the coseismic effect accounts for a fraction of the overall secular plate tectonic effect, rather than being annihilated by the interseismic effect as assumed in the viewpoint of earthquake cycles given by Cambiotti et al (2016). Moreover, we raise the caveats in modeling the said tectonic contribution to SPD, whereof the results of Cambiotti et al (2016) roughly agree with the calculated coseismic results whereas those of Adhikari et al (2018) give the opposite in direction. By all accounts, the budget and understanding of the SPD excitation is not closed.…”

Section: Discussionsupporting

confidence: 58%

“…On the other hand, the recent work by Adhikari et al (2018) yielded the conclusion opposite to the above. They surmised that the tectonic contribution (mantle convection) is rather important; in fact it, now pointing toward Direction B in their version is potentially able to account for the significant shortage of the purported (or calculated and statistically preferred) GIA and environmental contribution (toward 15°E, orthogonal to Directions A and B) from the observed SPD (toward Direction B) during the twentieth century.…”

Section: Effects Of Tectonic Plate Motionsmentioning

confidence: 78%

“…More significantly, we shall argue that the coseismic contribution represents a certain portion of the total effect arising from the mass redistribution associated with the tectonic plate motions, rather than a transient effect to be annihilated by the interseismic motions in the long run as suggested by Cambiotti et al (). Cambiotti et al () in addition modeled and estimated the total contribution of the tectonic plate motions to SPD and obtained a tectonic SPD in Direction A, whereas Adhikari et al (), doing the same, obtained a tectonic SPD in the opposite Direction B instead. We shall raise the caveats of adopting such modeling in budgeting and interpreting the SPD, in particular when both seismic and aseismic contributions are involved.…”

Section: Introductionmentioning

confidence: 99%

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Seismic Effects on the Secular Drift of the Earth's Rotational Pole

Chun

Chao

2019

JGR Solid Earth

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Earthquake‐induced mass redistribution in the Earth excites the polar motion; its cumulative coseismic effect has been found to cause a secular polar drift (SPD) toward ~140°E longitude with strong statistical tendency. Here we find numerically the cumulatively coseismic effect in SPD since 1952 to be at the rate of ~0.75 mas/year (or ~2.3 cm/year), amounting to nearly 20% of the observed SPD that points to the opposite geographical direction and hence is significant in the pursuit of understanding the source budget of SPD. We further argue on theoretical and observational ground that such behavior reflects that of the overall plate tectonic motion and in fact accounts for a fraction of the latter over long term. The exact amount of the fraction is indeterminate until mass transport models of plate tectonics prove adequate. This viewpoint is in contrast to that of Cambiotti et al. (2016, https://doi.org/10.1093/gji/ggw077) which required the coseismic effect to get annihilated completely by the interseismic effect under their earthquake cycle decomposition of the velocity field at the faulting system.

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“…As far as the Indus, Gange, Brahmaputra, and Mekong are concerned, the basins have become wetter due to more intense monsoonal precipitation, and the contributions of snow-and ice-melt have become less relevant [2]. An unexpected consequence to changes in the HKKH water supply has been highlighted in recent studies by [3,4], where it was proposed that changes in the Earth's axis are related to water mass loss away from the Indian subcontinent and the Caspian Sea. The complex and irregular orography of the HKKH region means that accurately modelling and taking sufficient observations to survey the region adequately is rather difficult from ground level.…”

Section: Introductionmentioning

confidence: 99%

Water Pathways for the Hindu-Kush-Himalaya and an Analysis of Three Flood Events

Boschi¹,

Lucarini

2019

Atmosphere

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The climatology of major sources and pathways of moisture for three locales along the Hindu-Kush-Himalayan region are examined, by use of Lagrangian methods applied to the ERA-Interim dataset, over the period from 1980 to 2016 for both summer (JJA) and winter (NDJ) periods. We also investigate the major flooding events of 2010, 2013, and 2017 in Pakistan, Uttarakhand, and Kathmandu, respectively, and analyse a subset of the climatology associated with the 20 most significant rainfall events over each region of interest. A comparison is made between the climatology and extreme events, in the three regions of interest, during the summer monsoon period. For Northern Pakistan and Uttarakhand, the Indus basin plays the largest role in moisture uptake. Moisture is also gathered from Eastern Europe and Russia. Extreme events display an increased influence of sub-tropical weather systems, which manifest themselves through low-level moisture transport; predominantly from the Arabian sea and along the Gangetic plain. In the Kathmandu region, it is found that the major moisture sources come from the Gangetic plain, Arabian Sea, Red Sea, Bay of Bengal, and the Indus basin. In this case, extreme event pathways largely match those of the climatology, although an increased number of parcels originate from the western end of the Gangetic plain. These results provide insights into the rather significant influence of mid-latitudinal weather systems, even during the monsoon season, in defining the climatology of the Hindu-Kush-Himalaya region, as well as how extreme precipitation events in this region represent atypical moisture pathways. We propose a detailed investigation of how such water pathways are represented in climate models for the present climate conditions and in future climate scenarios, as this may be extremely relevant for understanding the impacts of climate change on the cryosphere and hydrosphere of the region.

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What drives 20th century polar motion?

Cited by 44 publications

References 71 publications

On Some Properties of the Glacial Isostatic Adjustment Fingerprints

On Some Properties of the Glacial Isostatic Adjustment Fingerprints

Seismic Effects on the Secular Drift of the Earth's Rotational Pole

Water Pathways for the Hindu-Kush-Himalaya and an Analysis of Three Flood Events

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