scholarly journals The role of orbital forcing, carbon dioxide and regolith in 100 kyr glacial cycles

2011 ◽  
Vol 7 (4) ◽  
pp. 1415-1425 ◽  
Author(s):  
A. Ganopolski ◽  
R. Calov
Keyword(s):  
Co2 Concentration ◽  
Orbital Forcing ◽  
Orbital Eccentricity ◽  
Glacial Cycles ◽  
Strongly Nonlinear ◽  
Ice Volume ◽  
The North ◽  
Nonlinear Responses ◽  
Continental Area

Abstract. The origin of the 100 kyr cyclicity, which dominates ice volume variations and other climate records over the past million years, remains debatable. Here, using a comprehensive Earth system model of intermediate complexity, we demonstrate that both strong 100 kyr periodicity in the ice volume variations and the timing of glacial terminations during past 800 kyr can be successfully simulated as direct, strongly nonlinear responses of the climate-cryosphere system to orbital forcing alone, if the atmospheric CO2 concentration stays below its typical interglacial value. The existence of long glacial cycles is primarily attributed to the North American ice sheet and requires the presence of a large continental area with exposed rocks. We show that the sharp, 100 kyr peak in the power spectrum of ice volume results from the long glacial cycles being synchronized with the Earth's orbital eccentricity. Although 100 kyr cyclicity can be simulated with a constant CO2 concentration, temporal variability in the CO2 concentration plays an important role in the amplification of the 100 kyr cycles.

scholarly journals The role of orbital forcing, carbon dioxide and regolith in 100 kyr glacial cycles

2011 ◽  
Vol 7 (4) ◽  
pp. 2391-2411 ◽  
Author(s):  
A. Ganopolski ◽  
R. Calov
Keyword(s):  
Nonlinear Response ◽  
Co2 Concentration ◽  
Orbital Forcing ◽  
Orbital Eccentricity ◽  
Glacial Cycles ◽  
Strongly Nonlinear ◽  
Ice Volume ◽  
The North ◽  
Continental Area

Abstract. The origin of the 100 kyr cyclicity which dominates ice volume variations and other climate records over the past million years remains debatable. Here, using a comprehensive Earth system model of intermediate complexity, we demonstrate that both strong 100 kyr periodicity in the ice volume variations and the timing of glacial terminations during past 800 kyr can be successfully simulated as the direct, strongly nonlinear response of the climate-cryosphere system to the orbital forcing alone, if the atmospheric CO2 concentration stays below its typical interglacial value. The existence of long glacial cycles is primarily attributed to the North American ice sheet and requires presence of a large continental area with exposed rocks. We show that the sharp peak in the power spectrum of ice volume at 100 kyr period results from the long glacial cycles being synchronized with the Earth's orbital eccentricity. Although 100 kyr cyclicity can be simulated with a constant CO2 concentration, temporal variability in the CO2 concentration plays an important role in the amplification of the 100 kyr cycles.

A Simple Model for Glacial Cycles and Impact of fossil fuel CO2 emissions

2020 ◽  
Author(s):  
Stefanie Talento ◽  
Andrey Ganopolski
Keyword(s):  
Fossil Fuel ◽  
Climate System ◽  
Total Carbon ◽  
Anthropogenic Emissions ◽  
Orbital Forcing ◽  
Glacial Cycles ◽  
Ice Volume ◽  
Global Mean Temperature ◽  
Physically Based ◽  
Linear Differential

<p>We propose a simple physically-based model of the coupled evolution of Northern Hemisphere (NH) landmass ice-volume, atmospheric CO<sub>2</sub> concentration and global mean temperature. The model only external forcings are the orbital forcing (maximum solar insolation at 65°N) and anthropogenic CO<sub>2</sub> emissions. The model consist of a system of 3 coupled non-linear differential equations, representing physical mechanisms relevant for the evolution of the climate system in time-scales longer than thousands of years.</p><p> </p><p>When forced by the orbital forcing only, the model is successful in reproducing the natural glacial-interglacial cycles of the last 800kyr, in agreement with paleorecords and simulations performed with the CLIMBER-2 Earth System Model of intermediate complexity. The model is successful in reproducing both the timing and amplitude of the glacial-interglacial variations, producing a correlation with paleodata of 0.75 in terms of NH ice-volume.</p><p> </p><p>For the next million years, we analyse the model results under different scenarios: the natural scenario (in which only orbital forcing is applied) and scenarios in which various magnitudes of fossil fuel CO<sub>2</sub> emissions are considered (in addition to the orbital forcing).</p><p> </p><p>When anthropogenic emissions are included the model shows that even fairly low CO<sub>2</sub> anthropogenic emissions (100 Pg or larger) are capable of affecting the next glacial inception, expected to occur in 120kyr from now, delaying large NH ice formation by 50kyr. Considering total carbon releases ranging between 1000 and 5000 Pg (a reasonable expectation of fossil fuel CO<sub>2</sub> emissions to occur in the next few hundred years) the temporal evolution of the climate system could be significantly different from the natural progression. Emissions larger than 3000 Pg could have long-lasting effects, being natural conditions not resumed even after 1 Million years have passed. In addition, emissions larger than 4000 Pg prevent glacial cycles in the next half million years.</p>

scholarly journals Glacial cycles and solar insolation: the role of orbital, seasonal, and spatial variations

2010 ◽  
Vol 6 (6) ◽  
pp. 2557-2591 ◽  
Author(s):  
R. K. Kaufmann ◽  
K. Juselius
Keyword(s):  
Late Quaternary ◽  
Explanatory Power ◽  
Spatial Variations ◽  
Glacial Cycles ◽  
Solar Insolation ◽  
Vector Autoregressive ◽  
Ice Volume ◽  
Seasonal And Spatial Variations ◽  
Summer Time

Abstract. We use a statistical model, the cointegrated vector autoregressive model, to evaluate the relative roles that orbital, seasonal, and spatial variations in solar insolation play in glacial cycles during the late Quaternary (390kyr – present). To do so, we estimate models of varying complexity and compare the accuracy of their in-sample simulations. Results indicate that variations in solar insolation associated with changes in Earth's orbit have the greatest explanatory power and that obliquity, precession, and eccentricity are needed to generate an accurate simulation of glacial cycles. Seasonal variations in insolation play a lesser role, while cumulative summer-time insolation has little explanatory power. Finally, solar insolation in the Northern Hemisphere generates the more accurate in-sample simulation of surface temperature while ice volume is simulated most accurately by solar insolation in the Southern Hemisphere.

scholarly journals Simulation of climate, ice sheets and CO<sub>2</sub> evolution during the last four glacial cycles with an Earth system model of intermediate complexity

2017 ◽  
Vol 13 (12) ◽  
pp. 1695-1716 ◽  
Author(s):  
Andrey Ganopolski ◽  
Victor Brovkin
Keyword(s):  
Carbon Cycle ◽  
Ice Sheets ◽  
Co2 Concentration ◽  
System Model ◽  
Model Parameters ◽  
Orbital Forcing ◽  
Earth System ◽  
Glacial Cycles ◽  
The Past ◽  
Paleoclimate Reconstructions

Abstract. In spite of significant progress in paleoclimate reconstructions and modelling of different aspects of the past glacial cycles, the mechanisms which transform regional and seasonal variations in solar insolation into long-term and global-scale glacial–interglacial cycles are still not fully understood – in particular, in relation to CO2 variability. Here using the Earth system model of intermediate complexity CLIMBER-2 we performed simulations of the co-evolution of climate, ice sheets, and carbon cycle over the last 400 000 years using the orbital forcing as the only external forcing. The model simulates temporal dynamics of CO2, global ice volume, and other climate system characteristics in good agreement with paleoclimate reconstructions. These results provide strong support for the idea that long and strongly asymmetric glacial cycles of the late Quaternary represent a direct but strongly nonlinear response of the Northern Hemisphere ice sheets to orbital forcing. This response is strongly amplified and globalised by the carbon cycle feedbacks. Using simulations performed with the model in different configurations, we also analyse the role of individual processes and sensitivity to the choice of model parameters. While many features of simulated glacial cycles are rather robust, some details of CO2 evolution, especially during glacial terminations, are sensitive to the choice of model parameters. Specifically, we found two major regimes of CO2 changes during terminations: in the first one, when the recovery of the Atlantic meridional overturning circulation (AMOC) occurs only at the end of the termination, a pronounced overshoot in CO2 concentration occurs at the beginning of the interglacial and CO2 remains almost constant during the interglacial or even declines towards the end, resembling Eemian CO2 dynamics. However, if the recovery of the AMOC occurs in the middle of the glacial termination, CO2 concentration continues to rise during the interglacial, similar to the Holocene. We also discuss the potential contribution of the brine rejection mechanism for the CO2 and carbon isotopes in the atmosphere and the ocean during the past glacial termination.

scholarly journals Orbital control on late Miocene climate and the North African monsoon: insight from an ensemble of sub-precessional simulations

2015 ◽  
Vol 11 (10) ◽  
pp. 1271-1295 ◽  
Author(s):  
A. Marzocchi ◽  
D. J. Lunt ◽  
R. Flecker ◽  
C. D. Bradshaw ◽  
A. Farnsworth ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Late Miocene ◽  
Global Climate ◽  
Co2 Concentration ◽  
Orbital Forcing ◽  
North African ◽  
African Monsoon ◽  
The North ◽  
Time Period ◽  
The Impact

Abstract. Orbital forcing is a key climate driver over multi-millennial timescales. In particular, monsoon systems are thought to be driven by orbital cyclicity, especially by precession. Here, we analyse the impact of orbital forcing on global climate with a particular focus on the North African monsoon, by carrying out an ensemble of 22 equally spaced (one every 1000 years) atmosphere–ocean–vegetation simulations using the HadCM3L model, covering one full late Miocene precession-driven insolation cycle with varying obliquity (between 6.568 and 6.589 Ma). The simulations only differ in their prescribed orbital parameters, which vary realistically for the selected time period. We have also carried out two modern-orbit control experiments, one with late Miocene and one with present-day palaeogeography, and two additional sensitivity experiments for the orbital extremes with varying CO2 forcing. Our results highlight the high sensitivity of the North African summer monsoon to orbital forcing, with strongly intensified precipitation during the precession minimum, leading to a northward penetration of vegetation up to ~ 21° N. The modelled summer monsoon is also moderately sensitive to palaeogeography changes, but it has a low sensitivity to atmospheric CO2 concentration between 280 and 400 ppm. Our simulations allow us to explore the climatic response to orbital forcing not only for the precession extremes but also on sub-precessional timescales. We demonstrate the importance of including orbital variability in model–data comparison studies, because doing so partially reduces the mismatch between the late Miocene terrestrial proxy record and model results. Failure to include orbital variability could also lead to significant miscorrelations in temperature-based proxy reconstructions for this time period, because of the asynchronicity between maximum (minimum) surface air temperatures and minimum (maximum) precession in several areas around the globe. This is of particular relevance for the North African regions, which have previously been identified as optimal areas to target for late Miocene palaeodata acquisition.

scholarly journals Sedimentology of the lower Serpukhovian (upper Mississippian) Mabou Group in the Cumberland Basin of eastern Canada: tectonic, halokinetic, and climatic implications

2015 ◽  
Vol 52 (12) ◽  
pp. 1150-1168 ◽  
Author(s):  
Pierre Jutras ◽  
Jason R. McLeod ◽  
John Utting
Keyword(s):  
Regional Climate ◽  
Orbital Forcing ◽  
Fault Activity ◽  
Eastern Canada ◽  
Third Order ◽  
Sea Levels ◽  
Ice Volume ◽  
The North ◽  
Arid Conditions ◽  
Basin Subsidence

The Visean–Serpukhovian transition in Atlantic Canada was marked by a general humidification of the climate as the region drifted towards equatorial latitudes. It also corresponds to a time when ice volume was increasing on Gondwana, which marked the end of Mississippian marine incursions in the region. Glacioeustatic fluctuations of greater magnitude are thought to have increased the response of the regional climate to third-order cyclicity from orbital forcing. In the Cumberland Basin, fluvial grey beds of the lower Serpukhovian Shepody Formation were deposited in sub-humid conditions during highstands, whereas red playa deposits of the same unit were deposited under semi-arid conditions during lowstands. Basin reconstruction suggests that this unit was sourced from the fault-bounded Cobequid and Caledonia highlands and deposited in two separate salt-withdrawal minibasins. This fluvial system was seemingly discharging to the north into the broad lake that deposited the contemporaneous Hastings Formation. A disconformity separates the Shepody Formation from mid-Serpukhovian red beds of the Claremont Formation and is tentatively associated with another increase in ice volume on Gondwana followed by a recrudescence of fault activity and basin subsidence. A prolonged time of aridity, floral crisis, non-deposition, deep weathering and karstification in late Serpukhovian to early Bashkirian times is contemporaneous with abundant glacial deposits in higher latitudes, suggesting that globally low sea levels may have been at play in creating a situation of greater continentality in the study area.

scholarly journals Sea ice as the glacial cycles’ Climate switch: role of seasonal and orbital forcing

2000 ◽  
Vol 15 (6) ◽  
pp. 605-615 ◽  
Author(s):  
Hezi Gildor ◽  
Eli Tziperman
Keyword(s):  
Sea Ice ◽  
Orbital Forcing ◽  
Glacial Cycles

Glaciation cycle models and their pullback attractors

2021 ◽  
Author(s):  
Keno Riechers ◽  
Niklas Boers ◽  
Michael Ghil ◽  
Takahito Mitsui
Keyword(s):  
Explanatory Power ◽  
Power Spectra ◽  
Climate System ◽  
Sustained Oscillation ◽  
Orbital Forcing ◽  
Pullback Attractors ◽  
Glacial Cycles ◽  
Ice Volume ◽  
The Earth ◽  
Dynamic Stochastic

&lt;p&gt;&lt;span&gt;The Pleistocene climate was dominated by alternating retreat and regrowth of massive ice sheets accompanied by large variations in the global mean temperature and sea level. Partial agreement between the power spectra of global ice volume proxies and high-latitude summer insolation provides evidence that quasi-periodic changes in the earth&amp;#8217;s orbital configuration affect the timing of glaciations and deglaciations. It remains, however, a topic of active debate whether the main cause of glacial cycles is an internal self-sustained oscillation of the climate system that merely phased locked, more or less, to orbital forcing or whether glacial cycles could not exist at all in the absence of orbital forcing. Furthermore, it is unclear whether past ice volume records should be regarded as the result of a purely deterministic process or as a randomly selected trajectory of a stochastic process. To study plausible paths of the earth&amp;#8217;s climate system given the orbital forcing, we compute the pullback attractors of several conceptual Pleistocene models. The results are confronted with the power spectra, as well as the time series of proxy records and conclusions will be drawn about the role of internal vs. forced variability and the possible contribution of stochastic processes to the mix of causes. We argue, moreover, that the explanatory power of either a deterministically chaotic or a dynamic-stochastic model cannot be assessed by comparing the model output to observations in the time domain alone.&lt;/span&gt;&lt;/p&gt;

The Inherited Past of the Broch: On Antiquarian Discourse and Contemporary Archaeology

2002 ◽  
Vol 24 (1) ◽  
pp. 1-20 ◽  
Author(s):  
ANDREW BAINES
Keyword(s):  
Material Culture ◽  
19Th Century ◽  
Academic Language ◽  
Contemporary Archaeology ◽  
The North

In reading archaeological texts, we expect to be engaged in a characteristically archaeological discourse, with a specific and recognisable structure and vocabulary. In evaluating the published work of 19th Century antiquarians, we will inevitably look for points of contact between their academic language and our own; success or failure in the identification of such points of contact may prompt us to recognise a nascent archaeology in some writings, while dismissing others as naïve or absurd. With this point in mind, this paper discusses the written and material legacies of three 19th Century antiquarians in the north of Scotland who worked on a particular monument type, the broch. The paper explores the degree to which each has been admitted as an influence on the development of the broch as a type. It then proceeds to compare this established typology with the author's experiences, in the field, of the sites it describes. In doing so, the paper addresses wider issues concerning the role of earlier forms of archaeological discourse in the development of present day archaeological classifications of, and of the problems of reconciling such classifications with our experiences of material culture.

Training of Village Teachers in Vilna Educational District in the 1860s and 1870s

2020 ◽  
Vol 58 ◽  
pp. 181-192
Author(s):  
Anna A. Komzolova
Keyword(s):  
Educational Reform ◽  
Rural Teachers ◽  
Cultural Brokers ◽  
The North ◽  
Central Russia ◽  
Russian Intelligentsia ◽  
Trained Teachers ◽  
The Village ◽  
North Western

One of the results of the educational reform of the 1860s was the formation of the regular personnel of village teachers. In Vilna educational district the goal was not to invite teachers from central Russia, but to train them on the spot by establishing special seminaries. Trained teachers were supposed to perform the role of «cultural brokers» – the intermediaries between local peasants and the outside world, between the culture of Russian intelligentsia and the culture of the Belarusian people. The article examines how officials and teachers of Vilna educational district saw the role of rural teachers as «cultural brokers» in the context of the linguistic and cultural diversity of the North-Western Provinces. According to them, the graduates of the pedagogical seminaries had to remain within the peasant estate and to keep in touch with their folk «roots». The special «mission» of the village teachers was in promoting the ideas of «Russian elements» and historical proximity to Russia among Belarusian peasants.

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