scholarly journals Crossover and peaks in the Pleistocene climate spectrum; understanding from simple ice age models

2019 ◽  
Vol 54 (3-4) ◽  
pp. 1801-1818 ◽  
Author(s):  
Peter Ditlevsen ◽  
Takahito Mitsui ◽  
Michel Crucifix
Keyword(s):  
Spectral Power ◽  
Ice Age ◽  
Compact Representation ◽  
Pleistocene Climate ◽  
Continuous Background ◽  
Quantitative Analyses ◽  
Self Similar ◽  
Different Origins ◽  
Scale Break ◽  
Narrow Bands

AbstractThe power spectrum provides a compact representation of the scale dependence of the variability in time series. At multi-millennial time scales the spectrum of the Pleistocene climate is composed of a set of narrow band spectral modes attributed to the regularly varying changes in insolation from the astronomical change in Earth’s orbit and rotation superimposed on a continuous background generally attributed to stochastic variations. Quantitative analyses of paleoclimatic records indicate that the continuous part comprises a dominant part of the variance. It exhibits a power-law dependency typical of stochastic, self-similar processes, but with a scale break at the frequency of glacial-interglacial cycles. Here we discuss possible origins of this scale break, the connection between the continuous background and the narrow bands, and the apparently modest spectral power above the continuum at these scales. We demonstrate that the observed scale break around 100 ka can have a variety of different origins and does not imply an internal time scale of correlation as implied by the simplest linear stochastic model.

Emergence of critical climate states during the Pleistocene

2021 ◽  
Author(s):  
Nicholas Golledge
Keyword(s):  
Dynamical Systems ◽  
Late Pleistocene ◽  
Dominant Frequency ◽  
Climate System ◽  
Ice Age ◽  
Early Pleistocene ◽  
Glacial Cycles ◽  
Pleistocene Climate ◽  
System Nodes ◽  
Systems Framework

<p>During the Pleistocene (approximately 2.6 Ma to present) glacial to interglacial climate variability evolved from dominantly 40 kyr cyclicity (Early Pleistocene) to 100 kyr cyclicity (Late Pleistocene to present). Three aspects of this period remain poorly understood: Why did the dominant frequency of climate oscillation change, given that no major changes in orbital forcing occurred? Why are the longer glacial cycles of the Late Pleistocene characterised by a more asymmetric form with abrupt terminations? And how can the Late Pleistocene climate be controlled by 100 kyr cyclicity when astronomical forcings of this frequency are so much weaker than those operating on shorter periods? Here we show that the decreasing frequency and increasing asymmetry that characterise Late Pleistocene ice age cycles both emerge naturally in dynamical systems in response to increasing system complexity, with collapse events (terminations) occuring only once a critical state has been reached. Using insights from network theory we propose that evolution to a state of criticality involves progressive coupling between climate system 'nodes', which ultimately allows any component of the climate system to trigger a globally synchronous termination. We propose that the climate state is synchronised at the 100 kyr frequency, rather than at shorter periods, because eccentricity-driven insolation variability controls mean temperature change globally, whereas shorter-period astronomical forcings only affect the spatial pattern of thermal forcing and thus do not favour global synchronisation. This dynamical systems framework extends and complements existing theories by accomodating the differing mechanistic interpretations of previous studies without conflict.</p>

scholarly journals ESD Ideas: Propagation of high-frequency forcing to ice age dynamics

2019 ◽  
Vol 10 (2) ◽  
pp. 257-260 ◽  
Author(s):  
Mikhail Y. Verbitsky ◽  
Michel Crucifix ◽  
Dmitry M. Volobuev
Keyword(s):  
Conservation Laws ◽  
High Frequency ◽  
Ice Sheet ◽  
Ice Age ◽  
Ice Flow ◽  
Age Dynamics ◽  
Nonlinear Character ◽  
Continuous Background ◽  
Ice Sheet Dynamics ◽  
Flow Conservation

Abstract. Palaeoclimate records display a continuous background of variability connecting centennial to 100 kyr periods. Hence, the dynamics at the centennial, millennial, and astronomical timescales should not be treated separately. Here, we show that the nonlinear character of ice sheet dynamics, which was derived naturally from the ice-flow conservation laws, provides the scaling constraints to explain the structure of the observed spectrum of variability.

scholarly journals Predicting Pleistocene climate from vegetation in North America

2007 ◽  
Vol 3 (1) ◽  
pp. 109-118 ◽  
Author(s):  
C. Loehle
Keyword(s):  
North America ◽  
Ice Age ◽  
Temperate Species ◽  
Eastern North America ◽  
Biogeographic Patterns ◽  
Free Zone ◽  
Low Co2 ◽  
Pleistocene Climate ◽  
Co2 Levels ◽  
Climate Indicator

Abstract. Climates at the Last Glacial Maximum have been inferred from fossil pollen assemblages, but these inferred climates are colder for eastern North America than those produced by climate simulations. It has been suggested that low CO2 levels could account for this discrepancy. In this study biogeographic evidence is used to test the CO2 effect model. The recolonization of glaciated zones in eastern North America following the last ice age produced distinct biogeographic patterns. It has been assumed that a wide zone south of the ice was tundra or boreal parkland (Boreal-Parkland Zone or BPZ), which would have been recolonized from southern refugia as the ice melted, but the patterns in this zone differ from those in the glaciated zone, which creates a major biogeographic anomaly. In the glacial zone, there are few endemics but in the BPZ there are many across multiple taxa. In the glacial zone, there are the expected gradients of genetic diversity with distance from the ice-free zone, but no evidence of this is found in the BPZ. Many races and related species exist in the BPZ which would have merged or hybridized if confined to the same refugia. Evidence for distinct southern refugia for most temperate species is lacking. Extinctions of temperate flora were rare. The interpretation of spruce as a boreal climate indicator may be mistaken over much of the region if the spruce was actually an extinct temperate species. All of these anomalies call into question the concept that climates in the zone south of the ice were extremely cold or that temperate species had to migrate far to the south. An alternate hypothesis is that low CO2 levels gave an advantage to pine and spruce, which are the dominant trees in the BPZ, and to herbaceous species over trees, which also fits the observed pattern. Thus climate reconstruction from pollen data is probably biased and needs to incorporate CO2 effects. Most temperate species could have survived across their current ranges at lower abundance by retreating to moist microsites. These would be microrefugia not easily detected by pollen records, especially if most species became rare. These results mean that climate reconstructions based on terrestrial plant indicators will not be valid for periods with markedly different CO2 levels.

scholarly journals Observations of HII Regions and Planetary Nebulae: the Infrared Emission Bands

1989 ◽  
Vol 135 ◽  
pp. 109-118
Author(s):  
Jesse D. Bregman
Keyword(s):  
Laboratory Data ◽  
Hii Regions ◽  
Infrared Emission ◽  
Spatial Behavior ◽  
Quality Data ◽  
High Quality Data ◽  
New Information ◽  
Different Origins ◽  
Single Material ◽  
Narrow Bands

Advances in infrared spectrometers and the theory that PAHs are responsible for the infrared emission bands have led to a wealth of new information in recent years. High quality data have shown many weak emission bands which are diagnostic of the material producing the bands. While correlations of the strengths of the narrow bands indicate that a single material can account for all of the narrow bands, independent spatial behavior of the narrow and broad components show that they have different origins. Predictions of the behavior of the spectra based on laboratory data have been confirmed observationally, strengthening the theory that PAH molecules are the origin of the infrared emission bands.

scholarly journals Oscillators and relaxation phenomena in Pleistocene climate theory

2012 ◽  
Vol 370 (1962) ◽  
pp. 1140-1165 ◽  
Author(s):  
Michel Crucifix
Keyword(s):  
Limit Cycle ◽  
Relaxation Oscillator ◽  
Homoclinic Orbits ◽  
Ice Age ◽  
Glacial Cycles ◽  
Stochastic Dynamical Systems ◽  
Pleistocene Climate ◽  
Stochastic Fluctuations ◽  
Earth’S Climate ◽  
Almost All

Ice sheets appeared in the northern hemisphere around 3 Ma (million years) ago and glacial–interglacial cycles have paced Earth's climate since then. Superimposed on these long glacial cycles comes an intricate pattern of millennial and sub-millennial variability, including Dansgaard–Oeschger and Heinrich events. There are numerous theories about these oscillations. Here, we review a number of them in order to draw a parallel between climatic concepts and dynamical system concepts, including, in particular, the relaxation oscillator, excitability, slow–fast dynamics and homoclinic orbits. Namely, almost all theories of ice ages reviewed here feature a phenomenon of synchronization between internal climate dynamics and astronomical forcing. However, these theories differ in their bifurcation structure and this has an effect on the way the ice age phenomenon could grow 3 Ma ago. All theories on rapid events reviewed here rely on the concept of a limit cycle excited by changes in the surface freshwater balance of the ocean. The article also reviews basic effects of stochastic fluctuations on these models, including the phenomenon of phase dispersion, shortening of the limit cycle and stochastic resonance. It concludes with a more personal statement about the potential for inference with simple stochastic dynamical systems in palaeoclimate science.

scholarly journals Vostok (Antarctica) ice-core time-scale from datings of different origins

2004 ◽  
Vol 39 ◽  
pp. 283-292 ◽  
Author(s):  
Andrey N. Salamatin ◽  
Elena A. Tsyganova ◽  
Vladimir Ya. Lipenkov ◽  
Jean Robert Petit
Keyword(s):  
Time Scale ◽  
Accumulation Rate ◽  
Ice Core ◽  
Ice Sheet ◽  
Monte Carlo Sampling ◽  
Age Dating ◽  
Ice Age ◽  
Sheet Flow ◽  
Glacier Ice ◽  
Different Origins

AbstractThree different approaches to ice-core age dating are employed to develop a depth–age relationship at Vostok, Antarctica: (1) correlating the ice-core isotope record to the geophysical metronome (Milankovich surface temperature cycles) inferred from the borehole temperature profile, (2) importing a known chronology from another (Devils Hole, Nevada, USA) paleoclimatic signal, and (3) direct ice-sheet flow modeling. Inverse Monte Carlo sampling is used to constrain the accumulation-rate reconstruction and ice-flow simulations in order to find the best-fit glaciological time-scale matched with the two other chronologies. The general uncertainty of the different age estimates varies from 2 to 6 kyr on average and reaches 6–15 kyr at maximum. Whatever the causes of this discrepancy might be, they are thought to be of different origins, and the age errors are assumed statistically independent. Thus, the average time-scale for the Vostok ice core down to 3350m depth is deduced consistent with all three dating procedures within the standard deviation limits of ±3.6 kyr, and its accuracy is estimated as 2.2 kyr on average. The constrained ice-sheet flow model allows, at least theoretically, extrapolation of the ice age–depth curve further to the boundary with the accreted lake ice where (at 3530m depth) the glacier-ice age may reach ∼2000 kyr.

scholarly journals Predicting Pleistocene climate from vegetation

2006 ◽  
Vol 2 (5) ◽  
pp. 979-1000
Author(s):  
C. Loehle
Keyword(s):  
Ice Age ◽  
Temperate Species ◽  
Tropical Mountains ◽  
Biogeographic Patterns ◽  
Free Zone ◽  
Low Co2 ◽  
Pleistocene Climate ◽  
Climate Simulations ◽  
Co2 Levels ◽  
Climate Indicator

Abstract. Climates at the Last Glacial Maximum have been inferred from fossil pollen assemblages, but these inferred climates are colder than those produced by climate simulations. Biogeographic evidence also argues against these inferred cold climates. The recolonization of glaciated zones in eastern North America following the last ice age produced distinct biogeographic patterns. It has been assumed that a wide zone south of the ice was tundra or boreal parkland (Boreal-Parkland Zone or BPZ), which would have been recolonized from southern refugia as the ice melted, but the patterns in this zone differ from those in the glaciated zone, which creates a major biogeographic anomaly. In the glacial zone, there are few endemics but in the BPZ there are many across multiple taxa. In the glacial zone, there are the expected gradients of genetic diversity with distance from the ice-free zone, but no evidence of this is found in the BPZ. Many races and related species exist in the BPZ which would have merged or hybridized if confined to the same refugia. Evidence for distinct southern refugia for most temperate species is lacking. Extinctions of temperate flora were rare. The interpretation of spruce as a boreal climate indicator may be mistaken over much of the region if the spruce was actually an extinct temperate species. All of these anomalies call into question the concept that climates in the zone south of the ice were very cold or that temperate species had to migrate far to the south. Similar anomalies exist in Europe and on tropical mountains. An alternate hypothesis is that low CO2 levels gave an advantage to pine and spruce, which are the dominant trees in the BPZ, and to herbaceous species over trees, which also fits the observed pattern. Most temperate species could have survived across their current ranges at lower abundance by retreating to moist microsites. These would be microrefugia not easily detected by pollen records, especially if most species became rare. These results mean that climate reconstruction based on terrestrial plant indicators will not be valid for periods with markedly different CO2 levels.

scholarly journals ESD Ideas: Propagation of high-frequency forcing to ice age dynamics

2018 ◽  
Author(s):  
Mikhail Y. Verbitsky ◽  
Michel Crucifix ◽  
Dmitry M. Volobuev
Keyword(s):  
Conservation Laws ◽  
Time Scales ◽  
High Frequency ◽  
Ice Sheet ◽  
Ice Age ◽  
Age Dynamics ◽  
Linear Character ◽  
Astronomical Time ◽  
Continuous Background ◽  
Ice Sheet Dynamics

Abstract. The observational records display a continuous background of variability connecting centennial to 100-ka periods. Hence, the dynamics at the centennial, millennial, and astronomical time scales should not be treated apart. Here, we show that the non-linear character of ice sheet dynamics, which was derived naturally from the conservation laws, provides the scaling constraints to explain the structure of the observed spectrum of variability.

scholarly journals The current situation and countermeasures for conservation of ancient and famous trees in Laoshan, Qingdao, China

2019 ◽  
Vol 49 (10) ◽  
Author(s):  
Xuliang Zhang ◽  
Lihua Wang ◽  
Zheng Liu ◽  
Tao Zheng ◽  
Yinghui Cao ◽  
...  
Keyword(s):  
Management Practices ◽  
Relevant Literature ◽  
Pests And Diseases ◽  
Large Numbers ◽  
Local Species ◽  
Quantitative Analyses ◽  
Qingdao City ◽  
Different Origins ◽  
Tourism Economy ◽  
Number Of Individuals

ABSTRACT: This study aimed to examined the characteristics of ancient and famous trees in Laoshan District, Qingdao City, Shandong Province, China, including species composition, number of individuals, origin, distribution, and age structure, to highlight the values of inheriting history and culture, improving urban environment, protecting regional biodiversity, promoting tourism economy and so on. The analyses was made through field surveys and quantitative analyses of statistical data and relevant literature, The main issues in their conservation are investigated and priority conservation measures are proposed. Results showed that there are 290 ancient and famous trees, comprising 42 species, 34 genera, and 26 families. These included four types of ancient and famous trees with different origins, namely religious trees planted by Buddhists, naturally preserved wild trees, trees with agricultural backgrounds for providing food or used as offerings, and exotic trees introduced from other places. There are relatively more local species and comparatively more elder trees. Ancient and famous trees are distributed in large numbers in Mountain Lao Scenic Area and many of them fall into temperate genera. Currently, ancient and famous tree conservation in Laoshan District is challenging because of issues such as habitat deterioration, severe effects of natural hazards, pests and diseases, weakening physiological function, and inadequate management. Based on all these analyses, countermeasures are proposed, which include regularly inspecting ancient and famous trees, restoring their habitats, reinforcing pest and disease controls, promoting studies on conservation technologies, improving management practices, increasing grants, and reforming the ownership system of ancient and famous trees.

Inventing the Formula of the Trees: A Solution of the Representation of Self Similar Objects

Fractals ◽  
1997 ◽  
Vol 05 (supp01) ◽  
pp. 51-64
Author(s):  
Erwin Hocevar ◽  
Walter G. Kropatsch
Keyword(s):  
Fixed Point ◽  
Fixed Points ◽  
Efficient Algorithm ◽  
Iterated Function Systems ◽  
Binary Image ◽  
The Self ◽  
Compact Representation ◽  
Iterated Function ◽  
Similar Images ◽  
Self Similar

Iterated Function Systems (IFS) seem to be used best to represent objects in the nature, because many of them are self similar. An IFS is a set of affine and contractive transformations. The union (so-called collage) of the subimages generated by transforming the whole image produces the image again - the self similar attractor of these transformations, which can be described by a binary image. For a fast and compact representation of those images, it would be desirable to calculate the transformations (the IFS-Codes) directly from the image that means to solve the inverse IFS-Problem. The solution presented in this paper will directly use the features of the self similar image. Subsets of the entire image and the subimage to be calculated are identified by the computation of the set difference between the pixels of the original and a rotated copy. The rotation and the scale factor of the transformation can be computed by the mapping of this two subsets onto each other, if the translation part - the fixed point - is predefined. The calculation of the transformation has to be repeated for each subimage. It will be proved, that with this method the IFS-Codes can be calculated for not convex, undistorted, and self similar images as long as the fixed point is known. An efficient algorithm for the identification of these fixed points within the image is introduced. Different ways to achieve this solutions are presented. In the conclusion the class of images, which can be coded by this method is defined, the results are pointed out, the advantages resp. the disadvantages of the method are evaluated, and possible ways to extend the method are discussed.

Sign in / Sign up

Export Citation Format

Share Document