Periodicities in mean sea-level fluctuations and climate change proxies: Lessons from the modelling for coastal management

Baker, R.; McGowan, S.A.

doi:10.1016/j.ocecoaman.2014.05.027

Cited by 14 publications

(2 citation statements)

References 88 publications

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“…As the choice of taper influences spectral estimates, tapers are to be selected with an objective to reduce spectral leakage (Riedel and Sidorenko, 1995), variance and to minimize local bias. Use of more numbers of tapers minimizes the variance in the spectral estimates (Baker and McGowan, 2014). The variance is inversely proportional to the number of tapers used.…”

Section: Multi-taper Methodsmentioning

confidence: 99%

Spectral analysis of wave elevation time histories using multi-taper method

Balaji

2015

Ocean Engineering

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Section: Multi-taper Methodsmentioning

confidence: 99%

Spectral analysis of wave elevation time histories using multi-taper method

Balaji

2015

Ocean Engineering

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“…11). These results are interesting both empirically and theoretically, since a Hausdorff dimension of D = 1.0801 can be de ned by computations of eigenvalues of z 2 + c where c is ¼. McMullen [27] derives a table of values for real quadratic polynomials of this form for a Julia Set divided by an expanding Markov partition. This is why the selection of quadratic regression is useful, since this dimension of a Julia Set appears to be imbedded into theoretical and empirical real quadratic polynomials in particular spectral periods.…”

Section: Hurst and Hausdorff Dimensionsmentioning

confidence: 99%

Exploring Quaternion Flipping of the Sun’s Magnetic Field in the Centennial Sunspot Record

Baker¹

2022

Preprint

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Sunspots are a major proxy for measuring the solar input into the Earth’s atmospheric dynamics. This paper explores whether sunspot evolution is underpinned by quaternion flipping in the 19th and 20th century sunspot histories. Quaternion flipping occurs when there is self-similarity in an R-matrix of sunspot cycles, where successive cycles evolve by rotating 1800 in a plane and the subsequent conjugation of subsequent cycles is in the reverse order. The historical sunspot record is partitioned according to quadratic clusters and significant periodicities in the spectral analysis, such as the 65.8 year signal. The flipping is then simulated by reversing the time axis between two adjoining ~ 66 year cycles in the sunspot record, producing an R3R2=-R4 quaternion flip, namely, between 1822–1888 and a reversed time series of 1976 − 1910. The Hausdorff dimensions and multi-taper spectral results for each flipped period are calculated in their entirety, where there was a 94.2% common spectral signal and 98.1% self-similarity. The R3R2=-R4 flip maintained a Hausdorff dimension of between 1.080 ± 0.025. The Hausdorff dimension of 1.081 is significant, since it generates a quadratic Julia set envelope of z2+c where c = ¼. For any values greater than 1.081, the Julia magnetic loops collapse and the quadratic point at z = ½ bifurcates into a pair of repelling fixed points off the real axis (that is, magnetic dipoles). This may explain the flipping in polarity after sunspot maximums and the self-similarity in frequencies between sunspot numbers and solar emissions. Further, there is a possibility that this centennial flipping can be traced from the Little Ice Age and the next phase is a centennial maximum mid-century. This research shows a fundamental relationship in a developing ‘fractal mechanics’ of solar emissions and the nature of its periodic input into the Earth’s atmospheric dynamics.

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A review of trend models applied to sea level data with reference to the “acceleration‐deceleration debate”

2015

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Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. This has motivated a number of authors to search for already existing accelerations in observations, which would be, if present, vital for coastal protection planning purposes. No scientific consensus has been reached yet as to how a possible acceleration could be separated from intrinsic climate variability in sea level records. This has led to an intensive debate on its existence and, if absent, also on the general validity of current future projections. Here we shed light on the controversial discussion from a methodological point of view. To do so, we provide a comprehensive review of trend methods used in the community so far. This resulted in an overview of 30 methods, each having its individual mathematical formulation, flexibilities, and characteristics. We illustrate that varying trend approaches may lead to contradictory acceleration‐deceleration inferences. As for statistics‐oriented trend methods, we argue that checks on model assumptions and model selection techniques yield a way out. However, since these selection methods all have implicit assumptions, we show that good modeling practices are of importance too. We conclude at this point that (i) several differently characterized methods should be applied and discussed simultaneously, (ii) uncertainties should be taken into account to prevent biased or wrong conclusions, and (iii) removing internally generated climate variability by incorporating atmospheric or oceanographic information helps to uncover externally forced climate change signals.

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Periodicities in mean sea-level fluctuations and climate change proxies: Lessons from the modelling for coastal management

Cited by 14 publications

References 88 publications

Spectral analysis of wave elevation time histories using multi-taper method

Spectral analysis of wave elevation time histories using multi-taper method

Exploring Quaternion Flipping of the Sun’s Magnetic Field in the Centennial Sunspot Record

A review of trend models applied to sea level data with reference to the “acceleration‐deceleration debate”

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