Eight glacial cycles from an Antarctic ice core

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doi:10.1038/nature02599

Cited by 2,051 publications

(331 citation statements)

References 41 publications

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“…First, if the very modest increases in greenhouse gas concentrations 5000-8000 years ago drove significant increases in global mean temperature, it would imply that very high global heating would result from the present greenhouse gas concentrations. Furthermore, analyses of the change in solar radiation owing to orbital forcing suggest that the Earth is presently in an unusually long interglacial period and is not due to enter another ice age for at least 10 000 years without any increases in greenhouse gas emissions [45,46]. In addition, the variation of atmospheric CO 2 concentration through the Holocene can be explained by the natural dynamics of the carbon cycle [47,48].…”

Section: History Of the Human-environment Relationshipmentioning

confidence: 99%

The Anthropocene: conceptual and historical perspectives

Steffen

Grinevald

Crutzen

et al. 2011

Phil. Trans. R. Soc. A.

1,678

840

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The human imprint on the global environment has now become so large and active that it rivals some of the great forces of Nature in its impact on the functioning of the Earth system. Although global-scale human influence on the environment has been recognized since the 1800s, the term Anthropocene , introduced about a decade ago, has only recently become widely, but informally, used in the global change research community. However, the term has yet to be accepted formally as a new geological epoch or era in Earth history. In this paper, we put forward the case for formally recognizing the Anthropocene as a new epoch in Earth history, arguing that the advent of the Industrial Revolution around 1800 provides a logical start date for the new epoch. We then explore recent trends in the evolution of the Anthropocene as humanity proceeds into the twenty-first century, focusing on the profound changes to our relationship with the rest of the living world and on early attempts and proposals for managing our relationship with the large geophysical cycles that drive the Earth’s climate system.

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Section: History Of the Human-environment Relationshipmentioning

confidence: 99%

The Anthropocene: conceptual and historical perspectives

Steffen

Grinevald

Crutzen

et al. 2011

Phil. Trans. R. Soc. A.

1,678

840

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“…Radiative forcing of GHGs in (b) is from Ganopolski and Calov (2011). Antarctic dust is from Augustin et al (2004). Blue lines in (d, e) correspond to the baseline experiment ONE_1.0 and purple lines to experiment ONE_1.1, where meltwater flux into the Atlantic was scaled up by a factor of 1.1. model version (ONE_1.0) and model with 10 % enhanced meltwater flux (ONE_1.1) are essentially identical most of the time, except for glacial terminations.…”

Section: Experiments With One-way Coupled Climate-carbon Cycle Modelmentioning

confidence: 99%

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

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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 CO 2 variability. Here using the Earth system model of intermediate complexity CLIMBER-2 we performed simulations of the coevolution 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 CO 2 , 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 CO 2 evolution, especially during glacial terminations, are sensitive to the choice of model parameters. Specifically, we found two major regimes of CO 2 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 CO 2 concentration occurs at the beginning of the interglacial and CO 2 remains almost constant during the interglacial or even declines towards the end, resembling Eemian CO 2 dynamics. However, if the recovery of the AMOC occurs in the middle of the glacial termination, CO 2 concentration continues to rise during the interglacial, similar to the Holocene. We also discuss the potential contribution of the brine rejection mechanism for the CO 2 and carbon isotopes in the atmosphere and the ocean during the past glacial termination.

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“…Physical Features and 3-D Firn Structure of the Five Samples in Figure 6, Extracted From X-Ray Absorption Microtomography Data The initial formation of the physical layering at Dome Fuji is discussed in order to better understand the evolution of porous structure, fabric and density at depths deeper than $9.6 m. The initial formation of snow strata at and near the surface of the ice sheet has long been a topic of discussion [e.g., Alley, 1988;Dang et al, 1997;Li and Zwally, 2004;Paterson, 1994;Zhou et al, 2002]. On the plateau region around Dome Fuji, several pioneers [Endo and Fujiwara, 1973;Koerner, 1971;Shiraiwa et al, 1996] described the characteristics of the snow cover over a wide region including Dome Fuji and the Plateau Station ( Figure 1, 79°15 0 S, 40°30 0 E, 3624 m above sea level). On the basis of a number of 1-m and deeper snow pits, both Koerner [1971] and Shiraiwa et al [1996] reported that the annual layering observed in snow stratigraphy had two components; one generally consisted of a thin (0.3 -4.0 cm), hard, dense, fine-grained layer, often associated with a hoar layer and a bonded grain crust, while the other section was softer, less dense, coarse-grained, and more homogeneous.…”

Section: Qualitative Measure Of Permeabilitymentioning

confidence: 99%

Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close off

et al. 2009

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[1] The evolution of the structure of a 112.59 m long firn core recovered at Dome Fuji, East Antarctica, was investigated in order to improve understanding of firn densification and bubble formation processes, which are important for interpreting local insolation proxies used for astronomical dating of deep ice cores. Using selected samples, we measured physical properties including (1) the relative dielectric permittivities in both the vertical and horizontal planes, (2) the bulk density at a resolution of millimeters, (3) the three-dimensional geometric structure of pore space, and (4) crystal orientation fabrics. We found that the firn at Dome Fuji contains horizontal strata with thicknesses of several centimeters. Near the surface of the ice sheet, these strata are characterized by contrasting bulk density. Earlier field studies suggest that summer insolation causes densification of surface firn. Down to $30 m, density maxima exhibited a clear positive correlation with the strength of structural anisotropy and c axis clustering around the vertical. In contrast, the correlation is negative in deeper firn, confirming previous findings that initially less dense firn became denser than initially dense firn. In addition, numerous examples of textures indicating that deformation preferentially occurred in weaker layers were found. Moreover, the initially dense firn layers were more permeable for air near the bottom of firn. We propose a model linking firn properties with conditions for the gas transport processes near the bottom of firn. The model explains how stronger insolation can lead to bulk ice with a lower O 2 /N 2 ratio and smaller total gas content.Citation: Fujita, S., J. Okuyama, A. Hori, and T. Hondoh (2009), Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close off,

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Eight glacial cycles from an Antarctic ice core

Cited by 2,051 publications

References 41 publications

The Anthropocene: conceptual and historical perspectives

The Anthropocene: conceptual and historical perspectives

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

Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close off

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Eight glacial cycles from an Antarctic ice core

Cited by 2,051 publications

References 41 publications

The Anthropocene: conceptual and historical perspectives

The Anthropocene: conceptual and historical perspectives

Simulation of climate, ice sheets and CO&lt;sub&gt;2&lt;/sub&gt; evolution during the last four glacial cycles with an Earth system model of intermediate complexity

Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close off

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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