Resonant Forcing of the Climate System in Subharmonic Modes

Pinault, Jean-Louis

doi:10.3390/jmse8010060

Cited by 6 publications

(13 citation statements)

References 36 publications

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“…He examined the idea of the modulated response of subtropical gyres to solar and orbital forcing, noting that a positive feedback loop amplifies the effects of the insolation gradient on the climate system and a resonance phenomenon occurs, filtering out some frequencies in favor of others. In another study, Pinault [56] demonstrated that the climate system in the Atlantic responds resonantly to solar and orbital forcing in several subharmonic modes. He advocated hypotheses on the evolution of the past climate, implicating the deviation between forcing periods and natural periods, according to the subharmonic modes and multi-frequency GRWs, including low frequencies.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Climate Variability Indices—A Guided Tour

et al. 2021

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The objective of this study is to provide a comprehensive review and characterization of selected climate variability indices. While we discuss many major climate variability mechanisms, we focus on four principal modes of climate variability related to the dynamics of Earth’s oceans and their interactions with the atmosphere: the El Niño–Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multi-decadal Oscillation (AMO). All these oscillation modes are of broad interest and considerable relevance, also in climate impact studies related to teleconnections, i.e., relationships between climate variations at distant locations. We try to decipher temporal patterns present in time series of different oscillation modes in the ocean–atmosphere system using exploratory analysis of the raw data, their structure, and properties, as well as illustrating the quasi-periodic behavior via wavelet analysis. With this contribution, we hope to help researchers in identifying and selecting data sources and climate variability indices that match their needs.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Climate Variability Indices—A Guided Tour

et al. 2021

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“…To ensure optimum stability of the dynamic system, each period is double or triple the previous period. Each of the subharmonic numbers corresponds to the number of revolutions that the GRW travels during a period [5]. The first 11 subharmonic numbers are 9 , whose periods are the product of the number of turns by 64, namely 64, 128, 256, 768, 1536, 3072, 6144, 12,288, 24,576, 49,152, and 98,304.…”

Section: Subharmonic Modesmentioning

confidence: 99%

“…The amplitude of GRWs according to the subharmonic modes n 1 = 2 0 to n 11 essentially results from the energy transfer mechanisms between coupled oscillators, relayed by intermediate forcing when the forcing period is close to the natural period of one of the GRWs [5,9].…”

Section: Subharmonic Modesmentioning

confidence: 99%

“…Morlet wavelet functions consist of a plane wave modulated by a Gaussian so that the scale and the period are confused [26]. The characteristic bands in which the filtering is performed according to the subharmonic numbers are given in [5,9]. Considering two adjacent bands, the filtered signal in the unified two bands is the sum of the filtered signals in each of the bands.…”

Section: Filtering Of Climatic Signals In Subharmonic Modesmentioning

confidence: 99%

“…Likewise, the modulation of obliquity induces a weak coupling with the mode n 10 since the MPT because of the significant deviation between both periods, 41 and 49 Ka, respectively. On the other hand, the forcing resulting from the modulation of precession whose period is nearly 25 Ka is intrinsically weak because of its low amplitude [5].…”

Section: Anharmonic and Subharmonic Modesmentioning

confidence: 99%

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Glaciers and Paleorecords Tell Us How Atmospheric Circulation Changes and Successive Cooling Periods Occurred in the Fennoscandia during the Holocene

Pinault¹

2021

JMSE

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Two major climatic phenomena that occurred during the Holocene are interpreted from the resonance in subharmonic modes of long-period Rossby waves winding around the North Atlantic gyre, the so-called gyral Rossby waves (GRWs). These are, on the one hand, the change in atmospheric circulation that occurred in the North Atlantic in the middle Holocene, and, on the other hand, the occurrence of abrupt cooling events more frequently than what is generally accepted. The amplitude of GRWs is deduced by filtering, within bands characteristic of various subharmonic modes, climate records from the Greenland ice sheet, pollen, and tree rings in northern Fennoscandia, and from two Norwegian glaciers in northern Folgefonna and on the Lyngen peninsula. While the subharmonic modes reflect the acceleration/deceleration phases of the western boundary current, an anharmonic mode is evidenced in the 400–450 year band. Abrupt cooling events of the climate are paced by this anharmonic mode while the western boundary current is decelerating, and the northward heat advection of air favors the melting of the pack ice. Then, the current of the northernmost part of the North Atlantic gyre cools before branching off to the north, which alters its buoyancy. On the other hand, according to high subharmonic modes, high-pressure systems prevailed over the North Atlantic in the first half of the Holocene while low-pressure systems resulted from baroclinic instabilities of the atmosphere dominate during the second half, favoring the growth of glaciers in Scandinavia by a better snowfall in winter and cooler summers.

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Solar and Anthropogenic Influences on Climate: Regression Analysis and Tentative Predictions

Stefani

2021

Climate

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The paper aims to quantify solar and anthropogenic influences on climate change, and to make some tentative predictions for the next hundred years. By means of double regression, we evaluate linear combinations of the logarithm of the carbon dioxide concentration and the geomagnetic aa index as a proxy for solar activity. Thereby, we reproduce the sea surface temperature (HadSST) since the middle of the 19th century with an adjusted R2 value of around 87 percent for a climate sensitivity (of TCR type) in the range of 0.6 K until 1.6 K per doubling of CO2. The solution of the double regression is quite sensitive: when including data from the last decade, the simultaneous occurrence of a strong El Niño and of low aa values leads to a preponderance of solutions with relatively high climate sensitivities around 1.6 K. If these later data are excluded, the regression delivers a significantly higher weight of the aa index and, correspondingly, a lower climate sensitivity going down to 0.6 K. The plausibility of such low values is discussed in view of recent experimental and satellite-borne measurements. We argue that a further decade of data collection will be needed to allow for a reliable distinction between low and high sensitivity values. In the second part, which builds on recent ideas about a quasi-deterministic planetary synchronization of the solar dynamo, we make a first attempt to predict the aa index and the resulting temperature anomaly for various typical CO2 scenarios. Even for the highest climate sensitivities, and an unabated linear CO2 increase, we predict only a mild additional temperature rise of around 1 K until the end of the century, while for the lower values an imminent temperature drop in the near future, followed by a rather flat temperature curve, is prognosticated.

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Resonant Forcing of the Climate System in Subharmonic Modes

Cited by 6 publications

References 36 publications

Climate Variability Indices—A Guided Tour

Climate Variability Indices—A Guided Tour

Glaciers and Paleorecords Tell Us How Atmospheric Circulation Changes and Successive Cooling Periods Occurred in the Fennoscandia during the Holocene

Solar and Anthropogenic Influences on Climate: Regression Analysis and Tentative Predictions

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