scholarly journals Glacial cycles and carbon dioxide: A conceptual model

2008 ◽  
Vol 35 (1) ◽  
Author(s):  
Andrew McC. Hogg
Keyword(s):  
Carbon Dioxide ◽  
Conceptual Model ◽  
Glacial Cycles

On the astronomical forcing of simple conceptual ice age models

2020 ◽  
Author(s):  
Gaëlle Leloup ◽  
Didier Paillard
Keyword(s):  
Conceptual Model ◽  
Climate Model ◽  
Ice Age ◽  
Early Pleistocene ◽  
Model Parameters ◽  
Ice Ages ◽  
Glacial Cycles ◽  
Orbital Parameters ◽  
Ice Volume ◽  
Astronomical Forcing

<p>Variations of the Earth’s orbital parameters are known to pace the ice volume variations of the last million year [1], even if the precise mechanisms remain unknown.<br>Several conceptual models have been used to try to better understand the connection between ice-sheet changes and the astronomical forcing. An often overlooked question is to decide which astronomical forcing can best explain the observed cycles.</p><p>A rather traditional practice was to use the insolation at a some specific day of the year, for instance at mid-july [2] or at the june solstice [3].<br>But it was also suggested that the integrated forcing above some given threshold could be a better alternative [4]. In a more recent paper, Tzedakis et al. [5] have shown that simple rules, based on the original Milankovitch forcing or caloric seasons, could also be used to explain the timing of ice ages.<br>Here we adapt and simplify the conceptual model of Parrenin and Paillard 2003 [6], to first reduce the set of parameters.<br>Like in the original conceptual model from [6], this simplified conceptual model is based on climate oscillations between two states: glaciation and deglaciation. It switches to one another when crossing a defined threshold. While the triggering of glaciations is only triggered by orbital parameters, the triggering of deglaciations is triggered by a combination of orbital parameters and ice volume. <br>Then, we apply the different possible forcings listed above and we try to adapt the model parameters to reproduce the ice volume record, at least in a qualitative way. This allows us to discuss which kind of astronomical forcing better explains the Quaternary ice ages, in the context of such simple threshold-based models.</p><p>[1] Variations in the Earth's Orbit: Pacemaker of the Ice Ages, Hays et al., 1976, Science
</p><p>[2] Modeling the Climatic Response to Orbital Variations, Imbrie and Imbrie, 1980, Science
</p><p>[3] The timing of Pleistocene glaciations from a simple multiple-state climate model, Paillard, 1998, Nature</p><p>[4] Early Pleistocene Glacial Cycles and the Integrated Summer Insolation Forcing, Huybers et al., 2006, Science</p><p>[5] A simple rule to determine which insolation cycles lead to interglacials, Tzedakis et al., 2017, Nature</p><p>[6] Amplitude and phase of glacial cycles from a conceptual model, Parrenin Paillard, 2003, EPSL.</p>

Southern Ocean upwelling, Earth’s obliquity, and glacial-interglacial atmospheric CO2 change

Science ◽  
2020 ◽  
Vol 370 (6522) ◽  
pp. 1348-1352
Author(s):  
Xuyuan E. Ai ◽  
Anja S. Studer ◽  
Daniel M. Sigman ◽  
Alfredo Martínez-García ◽  
François Fripiat ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Late Pleistocene ◽  
Atmospheric Carbon Dioxide ◽  
Global Climate ◽  
Nitrogen Isotope ◽  
Ice Ages ◽  
Glacial Cycles ◽  
Atmospheric Carbon ◽  
Carbon Dioxide Levels ◽  
The Antarctic

Previous studies have suggested that during the late Pleistocene ice ages, surface-deep exchange was somehow weakened in the Southern Ocean’s Antarctic Zone, which reduced the leakage of deeply sequestered carbon dioxide and thus contributed to the lower atmospheric carbon dioxide levels of the ice ages. Here, high-resolution diatom-bound nitrogen isotope measurements from the Indian sector of the Antarctic Zone reveal three modes of change in Southern Westerly Wind–driven upwelling, each affecting atmospheric carbon dioxide. Two modes, related to global climate and the bipolar seesaw, have been proposed previously. The third mode—which arises from the meridional temperature gradient as affected by Earth’s obliquity (axial tilt)—can explain the lag of atmospheric carbon dioxide behind climate during glacial inception and deglaciation. This obliquity-induced lag, in turn, makes carbon dioxide a delayed climate amplifier in the late Pleistocene glacial cycles.

scholarly journals Sediment yield over glacial cycles: A conceptual model

2021 ◽  
pp. 030913332199729
Author(s):  
Gilles Antoniazza ◽  
Stuart N Lane
Keyword(s):  
Conceptual Model ◽  
Sediment Yield ◽  
Future Research ◽  
Glacial Cycle ◽  
Glacial Cycles ◽  
Wide Range ◽  
Bedrock Erosion ◽  
Time Required ◽  
Glacier Advance ◽  
Sediment Export

The temporal variability in sediment export yield from glaciers over a timescale of multiple glacial cycles (e.g. 1 × 102 − 1 × 106 years) is of interest for a wide range of applications in glaciology, sedimentology, geomorphology, climatology and environmental engineering. However, the time required for the products of glacial erosion to be transferred through glaciated catchments and the extent to which glacially-conditioned sediment can be transiently stored within them are still poorly constrained and a matter of debate within the community. We propose a conceptual model of the variability in sediment exported from glaciers over multiple glacial cycles based on a literature review. Sediment yield is likely to be highly variable through a glacial cycle, notably between phases of glacier advance, retreat and re-advance due to changes in ice velocity and erosion rates, ice and meltwater transport capacity, and in glacially-conditioned sediment accessibility at the bed. Typically, early phases of glacier retreat and re-advance are expected to lead to the highest increase in sediment yield due to the ease with which the products of bedrock erosion can be accessed and reworked. In contrast, later phases of glacial (re)advance, once glacially-conditioned sedimentary sources become exhausted, may be characterized by intermediate rates of sediment export yield maintained through bedrock erosion. The latest phases of deglaciation, once glacially-conditioned sedimentary sources are either exhausted, stabilized or disconnected from active processes of sediment transfer, are likely to have the lowest rate of export. The conceptual model proposed in this paper fills a gap in the literature by developing a continuous pattern of sediment yield rate variability over the course of multiple glacial cycles, with wider implications for future research. However, its systematic applicability to various glacier settings and glaciations needs more field and modeling data to validate it.

Amplitude and phase of glacial cycles from a conceptual model

2003 ◽  
Vol 214 (1-2) ◽  
pp. 243-250 ◽  
Author(s):  
Frédéric Parrenin ◽  
Didier Paillard
Keyword(s):  
Conceptual Model ◽  
Glacial Cycles

scholarly journals Periodic orbits for a discontinuous vector field arising from a conceptual model of glacial cycles

Nonlinearity ◽  
2016 ◽  
Vol 29 (6) ◽  
pp. 1843-1864 ◽  
Author(s):  
James Walsh ◽  
Esther Widiasih ◽  
Jonathan Hahn ◽  
Richard McGehee
Keyword(s):  
Vector Field ◽  
Conceptual Model ◽  
Periodic Orbits ◽  
Glacial Cycles

scholarly journals Testing Hypotheses About Glacial Dynamics and the Stage 11 Paradox Using a Statistical Model of Paleo-Climate

2020 ◽  
Author(s):  
Robert K. Kaufmann ◽  
Felix Pretis
Keyword(s):  
Carbon Dioxide ◽  
Statistical Model ◽  
Critical Role ◽  
Model Performance ◽  
Sea Salt ◽  
Threshold Effects ◽  
Sample Period ◽  
Oceanic Circulation ◽  
Glacial Cycles ◽  
Glacial Dynamics

Abstract. To test hypotheses about glacial dynamics, the Mid-Brunhes event, and the stage 11 paradox, we evaluate the ability of a statistical model to simulate climate during the previous ~800 000 years. Throughout this period, the model simulates the timing and magnitude of glacial cycles, including the saw-tooth pattern in which ice accumulates gradually and ablates rapidly, without nonlinearities or threshold effects. This suggests that nonlinearities and/or threshold effects do not play a critical role in glacial cycles. Furthermore, model accuracy throughout the previous ~800 000 years suggest that changes in glacial cycles associated with the Mid-Brunhes event, which occurs near the division between the out-of-sample period and the in-sample period, are not caused by changes in the dynamics of the climate system. Conversely, poor model performance during MIS stage 11 and Termination V is consistent with arguments that the stage 11 paradox represents a mismatch between orbital geometry and climate. Statistical orderings of simulation errors indicate that periods of reduced accuracy start with significant reductions in the model's ability to simulate carbon dioxide, non-sea-salt sodium, and non-sea-salt calcium. Their importance suggests that the stage 11 paradox is generated by changes in atmospheric and/or oceanic circulation that affect ocean ventilation of carbon dioxide.

Electron Cytochemical Study of Carbon Dioxide Laser Effect on Rhesus Monkey Cornea

1974 ◽  
Vol 32 ◽  
pp. 224-225
Author(s):  
K. C. Tsou ◽  
J. Morris ◽  
P. Shawaluk ◽  
B. Stuck ◽  
E. Beatrice
Keyword(s):  
Carbon Dioxide ◽  
Electron Microscope ◽  
Rhesus Monkey ◽  
Carbon Dioxide Laser ◽  
Cytochemical Study ◽  
Laser Effect

While much is known regarding the effect of lasers on the retina, little study has been done on the effect of lasers on cornea, because of the limitation of the size of the material. Using a combination of electron microscope and several newly developed cytochemical methods, the effect of laser can now be studied on eye for the purpose of correlating functional and morphological damage. The present paper illustrates such study with CO2 laser on Rhesus monkey.

The Critical Point Drying Method Applied to Scanning Electron Microscopy of L-929 Cells

1970 ◽  
Vol 28 ◽  
pp. 278-279
Author(s):  
Charles TurnbiLL ◽  
Delbert E. Philpott
Keyword(s):  
Electron Microscopy ◽  
Carbon Dioxide ◽  
Surface Tension ◽  
Critical Point ◽  
Freeze Drying ◽  
Attractive Alternative ◽  
Crystal Formation ◽  
Critical Point Drying ◽  
Time Required ◽  
Scanning Electron

The advent of the scanning electron microscope (SCEM) has renewed interest in preparing specimens by avoiding the forces of surface tension. The present method of freeze drying by Boyde and Barger (1969) and Small and Marszalek (1969) does prevent surface tension but ice crystal formation and time required for pumping out the specimen to dryness has discouraged us. We believe an attractive alternative to freeze drying is the critical point method originated by Anderson (1951; for electron microscopy. He avoided surface tension effects during drying by first exchanging the specimen water with alcohol, amy L acetate and then with carbon dioxide. He then selected a specific temperature (36.5°C) and pressure (72 Atm.) at which carbon dioxide would pass from the liquid to the gaseous phase without the effect of surface tension This combination of temperature and, pressure is known as the "critical point" of the Liquid.

A global perspective of ground level, 'ambient' carbon dioxide for assessing the response of plants to atmospheric CO2

2001 ◽  
Vol 7 (7) ◽  
pp. 789-796 ◽  
Author(s):  
L. H. Ziska ◽  
O. Ghannoum ◽  
J. T. Baker ◽  
J. Conroy ◽  
J. A. Bunce ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ground Level ◽  
Global Perspective ◽  
Atmospheric Co2
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