scholarly journals Non-linear regime shifts in Holocene Asian monsoon variability: potential impacts on cultural change and migratory patterns

2015 ◽  
Vol 11 (5) ◽  
pp. 709-741 ◽  
Author(s):  
J. F. Donges ◽  
R. V. Donner ◽  
N. Marwan ◽  
S. F. M. Breitenbach ◽  
K. Rehfeld ◽  
...  
Keyword(s):  
Climate Change ◽  
Cultural Change ◽  
Asian Monsoon ◽  
Regime Shifts ◽  
Linear Regime ◽  
Continental Scale ◽  
Monsoon Variability ◽  
Non Linear ◽  
Monsoon System ◽  
Monsoon Dynamics

Abstract. The Asian monsoon system is an important tipping element in Earth's climate with a large impact on human societies in the past and present. In light of the potentially severe impacts of present and future anthropogenic climate change on Asian hydrology, it is vital to understand the forcing mechanisms of past climatic regime shifts in the Asian monsoon domain. Here we use novel recurrence network analysis techniques for detecting episodes with pronounced non-linear changes in Holocene Asian monsoon dynamics recorded in speleothems from caves distributed throughout the major branches of the Asian monsoon system. A newly developed multi-proxy methodology explicitly considers dating uncertainties with the COPRA (COnstructing Proxy Records from Age models) approach and allows for detection of continental-scale regime shifts in the complexity of monsoon dynamics. Several epochs are characterised by non-linear regime shifts in Asian monsoon variability, including the periods around 8.5–7.9, 5.7–5.0, 4.1–3.7, and 3.0–2.4 ka BP. The timing of these regime shifts is consistent with known episodes of Holocene rapid climate change (RCC) and high-latitude Bond events. Additionally, we observe a previously rarely reported non-linear regime shift around 7.3 ka BP, a timing that matches the typical 1.0–1.5 ky return intervals of Bond events. A detailed review of previously suggested links between Holocene climatic changes in the Asian monsoon domain and the archaeological record indicates that, in addition to previously considered longer-term changes in mean monsoon intensity and other climatic parameters, regime shifts in monsoon complexity might have played an important role as drivers of migration, pronounced cultural changes, and the collapse of ancient human societies.

scholarly journals Nonlinear regime shifts in Holocene Asian monsoon variability: potential impacts on cultural change and migratory patterns

2014 ◽  
Vol 10 (2) ◽  
pp. 895-975 ◽  
Author(s):  
J. F. Donges ◽  
R. V. Donner ◽  
N. Marwan ◽  
S. F. M. Breitenbach ◽  
K. Rehfeld ◽  
...  
Keyword(s):  
Climate Change ◽  
Cultural Change ◽  
Asian Monsoon ◽  
Regime Shifts ◽  
Nonlinear Regime ◽  
Robust Detection ◽  
Continental Scale ◽  
Monsoon Variability ◽  
Monsoon System ◽  
Monsoon Dynamics

Abstract. The Asian monsoon system has been recognised as an important tipping element in Earth's climate. In this work, we apply recurrence networks, a recently developed technique for nonlinear time series analysis of palaeoclimate data, for detecting episodes with pronounced changes in Asian monsoon dynamics during the last 10 ka in speleothem records from 10 caves covering the major branches of the Asian monsoon system. Our methodology includes multiple archives, explicit consideration of dating uncertainties with the COPRA approach and rigorous significance testing for the coexistence of monsoonal regime shifts at multiple locations to ensure a robust detection of continental-scale changes in monsoonal dynamics. This approach enables us to identify several epochs characterised by nonlinear regime shifts in Asian monsoon variability (8.5–8.0, 5.7–5.4, 4.1–3.6 and 2.8–2.2 ka BP), the timing of which suggests a connection to high-latitude Bond events and other episodes of Holocene rapid climate change (RCC). Interestingly, we also observe a previously unnoticed episode of significantly increased regularity of monsoonal variations around 7.3 ka BP, a timing that is consistent with the typical 1.0–1.5 ka return intervals of Bond events. A possible solar forcing of the detected nonlinear regime shifts in Asian monsoon dynamics is suggested by their co-occurence with pronounced minima and strong variability in solar activity. Drawing on a comprehensive review of the Holocene archeological record in the Asian monsoon realm, we find that these regime shifts partly coincide with known major periods of migration, pronounced cultural changes, and the collapse of ancient human societies. These findings indicate that also future transitions in monsoonal dynamics could induce potentially severe socio-economic impacts of climate change.

scholarly journals Cyclone trends constrain monsoon variability during late Oligocene sea level highstands (Kachchh Basin, NW India)

2013 ◽  
Vol 9 (5) ◽  
pp. 2101-2115 ◽  
Author(s):  
M. Reuter ◽  
W. E. Piller ◽  
M. Harzhauser ◽  
A. Kroh
Keyword(s):  
Sea Level ◽  
Asian Monsoon ◽  
Vertical Wind Shear ◽  
Monsoon Circulation ◽  
Late Oligocene ◽  
Monsoon Variability ◽  
Kachchh Basin ◽  
Storm Wave ◽  
Monsoon System

Abstract. Climate change has an unknown impact on tropical cyclones and the Asian monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin) as a recorder of tropical cyclone activity along the NW Indian coast during the late Oligocene warming period (~ 27–24 Ma). Proxy data providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system at the Oligocene–Miocene boundary. The vast shell concentrations are comprised of a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deeper to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished, each recording a relative storm wave base. (1) A shallow storm wave base is shown by nearshore molluscs, reef corals and Clypeaster echinoids; (2) an intermediate storm wave base depth is indicated by lepidocyclinid foraminifers, Eupatagus echinoids and corallinacean algae; and (3) a deep storm wave base is represented by an Amussiopecten bivalve-Schizaster echinoid assemblage. These wave base depth estimates were used for the reconstruction of long-term tropical storm intensity during the late Oligocene. The development and intensification of cyclones over the recent Arabian Sea is primarily limited by the atmospheric monsoon circulation and strength of the associated vertical wind shear. Therefore, since the topographic boundary conditions for the Indian monsoon already existed in the late Oligocene, the reconstructed long-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~ 26 Ma followed by a period of monsoon weakening during the peak of the late Oligocene global warming (~ 24 Ma).

scholarly journals Regime Shifts in Glacier and Ice Sheet Response to Climate Change: Examples From the Northern Hemisphere

2021 ◽  
Vol 3 ◽  
Author(s):  
Shawn J. Marshall
Keyword(s):  
Climate Change ◽  
Freezing Point ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Regime Shifts ◽  
Glacier Mass Balance ◽  
Polar Regions ◽  
Linear Temperature ◽  
Recent Climate ◽  
Non Linear

Glaciers and ice sheets are experiencing dramatic changes in response to recent climate change. This is true in both mountain and polar regions, where the extreme sensitivity of the cryosphere to warming temperatures may be exacerbated by amplification of global climate change. For glaciers and ice sheets, this sensitivity is due to a number of non-linear and threshold processes within glacier mass balance and glacier dynamics. Some of this is simply tied to the freezing point of water; snow and ice are no longer viable above 0°C, so a gradual warming that crosses this threshold triggers the onset of melting or gives rise to an abrupt regime shift between snowfall and rainfall. Other non-linear, temperature-dependent processes are more subtle, such as the evolution from polythermal to temperate ice, which supports faster ice flow, a shift from meltwater retention to runoff in temperate or ice-rich (i.e., heavily melt-affected) firn, and transitions from sublimation to melting under warmer and more humid atmospheric conditions. As melt seasons lengthen, there is also a longer snow-free season and an expansion of glacier ablation area, with the increased exposure of low-albedo ice non-linearly increasing melt rates and meltwater runoff. This can be accentuated by increased concentration of particulate matter associated with algal activity, dust loading from adjacent deglaciated terrain, and deposition of impurities from industrial and wildfire activity. The loss of ice and darkening of glaciers represent an effective transition from white to grey in the world's mountain regions. This article discusses these transitions and regime shifts in the context of challenges to model and project glacier and ice sheet response to climate change.

scholarly journals Cyclone trends constrain monsoon variability during Late Oligocene sea level highstands (Kachchh Basin, NW India)

2013 ◽  
Vol 9 (1) ◽  
pp. 583-613
Author(s):  
M. Reuter ◽  
W. E. Piller ◽  
M. Harzhauser ◽  
A. Kroh
Keyword(s):  
Tropical Cyclone ◽  
Sea Level ◽  
Asian Monsoon ◽  
Indian Monsoon ◽  
Late Oligocene ◽  
Third Order ◽  
Monsoon Variability ◽  
Kachchh Basin ◽  
Storm Wave ◽  
Monsoon System

Abstract. Important concerns about the consequences of climate change for India are the potential impact on tropical cyclones and the monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin) as an indicator of tropical cyclone activity along the NW Indian coast during the Late Oligocene warming period (~27–24 Ma). Direct proxies providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system in the Early Miocene. The vast shell concentrations comprise a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deep to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished each recording a relative storm wave base depth. (1) A shallow storm wave base is shown by nearshore mollusks, corals and Clypeaster echinoids; (2) an intermediate storm wave base depth is indicated by lepidocyclind foraminifers, Eupatagus echinoids and corallinaceans; and (3) a deep storm wave base is represented by an Amussiopecten–Schizaster echinoid assemblage. Vertical changes in these skeletal associations give evidence of gradually increasing tropical cyclone intensity in line with third-order sea level rise. The intensity of cyclones over the Arabian Sea is primarily linked to the strength of the Indian monsoon. Therefore and since the topographic boundary conditions for the Indian monsoon already existed in the Late Oligocene, the longer-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~26 Ma followed by a period of monsoon weakening during the peak of the Late Oligocene global warming (~24 Ma).

scholarly journals Continental vs. Global Niche-Based Modelling of Freshwater Species’ Distributions: How Big Are the Differences in the Estimated Climate Change Effects?

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 816
Author(s):  
Danijela Markovic ◽  
Jörg Freyhof ◽  
Oskar Kärcher
Keyword(s):  
Climate Change ◽  
Thermal Properties ◽  
Safety Margin ◽  
Thermal Response ◽  
Future Climate Change ◽  
Freshwater Species ◽  
Response Curves ◽  
Preferred Temperature ◽  
Continental Scale ◽  
Management Actions

Thermal response curves that depict the probability of occurrence along a thermal gradient are used to derive various species’ thermal properties and abilities to cope with warming. However, different thermal responses can be expected for different portions of a species range. We focus on differences in thermal response curves (TRCs) and thermal niche requirements for four freshwater fishes (Coregonus sardinella, Pungitius pungitius, Rutilus rutilus, Salvelinus alpinus) native to Europe at (1) the global and (2) European continental scale. European ranges captured only a portion of the global thermal range with major differences in the minimum (Tmin), maximum (Tmax) and average temperature (Tav) of the respective distributions. Further investigations of the model-derived preferred temperature (Tpref), warming tolerance (WT = Tmax − Tpref), safety margin (SM = Tpref − Tav) and the future climatic impact showed substantially differing results. All considered thermal properties either were under- or overestimated at the European level. Our results highlight that, although continental analyses have an impressive spatial extent, they might deliver misleading estimates of species thermal niches and future climate change impacts, if they do not cover the full species ranges. Studies and management actions should therefore favor whole global range distribution data for analyzing species responses to environmental gradients.

scholarly journals Non-Linear Thermoelectric Devices with Surface-Disordered Nanowires

Applied Nano ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 162-183
Author(s):  
Peter Markoš ◽  
Khandker Muttalib
Keyword(s):  
Thermodynamic Parameters ◽  
Power Output ◽  
Heat Current ◽  
Linear Regime ◽  
Thermoelectric Devices ◽  
Charge Current ◽  
Thermal Current ◽  
Surface Disorder ◽  
Non Linear

We reviewed some recent ideas to improve the efficiency and power output of thermoelectric nano-devices. We focused on two essentially independent aspects: (i) increasing the charge current by taking advantage of an interplay between the material and the thermodynamic parameters, which is only available in the non-linear regime; and (ii) decreasing the heat current by using nanowires with surface disorder, which helps excite localized phonons at random positions that can strongly scatter the propagating phonons carrying the thermal current.

scholarly journals Continent-wide tree fecundity driven by indirect climate effects

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
James S. Clark ◽  
Robert Andrus ◽  
Melaine Aubry-Kientz ◽  
Yves Bergeron ◽  
Michal Bogdziewicz ◽  
...  
Keyword(s):  
Climate Change ◽  
Species Distribution Models ◽  
Climate Condition ◽  
Distribution Models ◽  
The West ◽  
Climate Effects ◽  
Continental Scale ◽  
Demographic Rates ◽  
Species Abundances ◽  
Meta Analyses

AbstractIndirect climate effects on tree fecundity that come through variation in size and growth (climate-condition interactions) are not currently part of models used to predict future forests. Trends in species abundances predicted from meta-analyses and species distribution models will be misleading if they depend on the conditions of individuals. Here we find from a synthesis of tree species in North America that climate-condition interactions dominate responses through two pathways, i) effects of growth that depend on climate, and ii) effects of climate that depend on tree size. Because tree fecundity first increases and then declines with size, climate change that stimulates growth promotes a shift of small trees to more fecund sizes, but the opposite can be true for large sizes. Change the depresses growth also affects fecundity. We find a biogeographic divide, with these interactions reducing fecundity in the West and increasing it in the East. Continental-scale responses of these forests are thus driven largely by indirect effects, recommending management for climate change that considers multiple demographic rates.

scholarly journals Configuration and intercomparison of deep learning neural models for statistical downscaling

2020 ◽  
Vol 13 (4) ◽  
pp. 2109-2124 ◽  
Author(s):  
Jorge Baño-Medina ◽  
Rodrigo Manzanas ◽  
José Manuel Gutiérrez
Keyword(s):  
Climate Change ◽  
Deep Learning ◽  
Statistical Downscaling ◽  
Linear Models ◽  
Regional Climate ◽  
Added Value ◽  
Climate Conditions ◽  
Continental Scale ◽  
Spatial Features ◽  
Learning Techniques

Abstract. Deep learning techniques (in particular convolutional neural networks, CNNs) have recently emerged as a promising approach for statistical downscaling due to their ability to learn spatial features from huge spatiotemporal datasets. However, existing studies are based on complex models, applied to particular case studies and using simple validation frameworks, which makes a proper assessment of the (possible) added value offered by these techniques difficult. As a result, these models are usually seen as black boxes, generating distrust among the climate community, particularly in climate change applications. In this paper we undertake a comprehensive assessment of deep learning techniques for continental-scale statistical downscaling, building on the VALUE validation framework. In particular, different CNN models of increasing complexity are applied to downscale temperature and precipitation over Europe, comparing them with a few standard benchmark methods from VALUE (linear and generalized linear models) which have been traditionally used for this purpose. Besides analyzing the adequacy of different components and topologies, we also focus on their extrapolation capability, a critical point for their potential application in climate change studies. To do this, we use a warm test period as a surrogate for possible future climate conditions. Our results show that, while the added value of CNNs is mostly limited to the reproduction of extremes for temperature, these techniques do outperform the classic ones in the case of precipitation for most aspects considered. This overall good performance, together with the fact that they can be suitably applied to large regions (e.g., continents) without worrying about the spatial features being considered as predictors, can foster the use of statistical approaches in international initiatives such as Coordinated Regional Climate Downscaling Experiment (CORDEX).

Selection of models to describe the temperature-dependent development of Neoleucinodes elegantalis (Lepidoptera: Crambidae) and its application to predict the species voltinism under future climate conditions

2021 ◽  
pp. 1-9
Author(s):  
Hevellyn Talissa dos Santos ◽  
Cesar Augusto Marchioro
Keyword(s):  
Climate Change ◽  
Linear Model ◽  
Future Climate ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Temperature Dependent ◽  
Dependent Development ◽  
Degree Day ◽  
Non Linear ◽  
The Impact

Abstract The small tomato borer, Neoleucinodes elegantalis (Guenée, 1854) is a multivoltine pest of tomato and other cultivated solanaceous plants. The knowledge on how N. elegantalis respond to temperature may help in the development of pest management strategies, and in the understanding of the effects of climate change on its voltinism. In this context, this study aimed to select models to describe the temperature-dependent development rate of N. elegantalis and apply the best models to evaluate the impacts of climate change on pest voltinism. Voltinism was estimated with the best fit non-linear model and the degree-day approach using future climate change scenarios representing intermediary and high greenhouse gas emission rates. Two out of the six models assessed showed a good fit to the observed data and accurately estimated the thermal thresholds of N. elegantalis. The degree-day and the non-linear model estimated more generations in the warmer regions and fewer generations in the colder areas, but differences of up to 41% between models were recorded mainly in the warmer regions. In general, both models predicted an increase in the voltinism of N. elegantalis in most of the study area, and this increase was more pronounced in the scenarios with high emission of greenhouse gases. The mathematical model (74.8%) and the location (9.8%) were the factors that mostly contributed to the observed variation in pest voltinism. Our findings highlight the impact of climate change on the voltinism of N. elegantalis and indicate that an increase in its population growth is expected in most regions of the study area.

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