Earth Environment of the Last Glacial Age. Why Was the Atmospheric CO2 Concentration Low?

Abstract. A 2.5-dimensional climate model of intermediate complexity, CLIMBER-2, fully coupled with the GREMLINS 3-D thermo-mechanical ice sheet model is used to simulate the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle and to investigate the ice sheets responses to both insolation and atmospheric CO2 concentration. This model reproduces the main phases of advance and retreat of Northern Hemisphere ice sheets during the last glacial cycle, although the amplitude of these variations is less pronounced than those based on sea level reconstructions. At the last glacial maximum, the simulated ice volume is 52.5×1015 m3 and the spatial distribution of both the American and Eurasian ice complexes is in reasonable agreement with observations, with the exception of the marine parts of these former ice sheets. A set of sensitivity studies has also been performed to assess the sensitivity of the Northern Hemisphere ice sheets to both insolation and atmospheric CO2. Our results suggest that the decrease of summer insolation is the main factor responsible for the early build up of the North American ice sheet around 120 kyr BP, in agreement with benthic foraminifera δ18O signals. In contrast, low insolation and low atmospheric CO2 concentration are both necessary to trigger a long-lasting glaciation over Eurasia.

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Climatic Conditions for modelling the Northern Hemisphere ice sheets throughout the ice age cycle

Climate of the Past ◽

10.5194/cp-3-423-2007 ◽

2007 ◽

Vol 3 (3) ◽

pp. 423-438 ◽

Cited By ~ 101

Author(s):

A. Abe-Ouchi ◽

T. Segawa ◽

F. Saito

Keyword(s):

Mass Balance ◽

Ice Sheet ◽

Co2 Concentration ◽

Atmospheric Co2 ◽

Ice Age ◽

Lapse Rate ◽

Orbital Parameters ◽

Last Glacial ◽

Atmospheric Co2 Concentration ◽

The Last Glacial

Abstract. The ice sheet-climate interaction as well as the climatic response to orbital parameters and atmospheric CO2 concentration are examined in order to drive an ice sheet model throughout an ice age cycle. Feedback processes between ice sheet and atmosphere are analyzed by numerical experiments using a high resolution General Circulation Model (GCM) under different conditions at the Last Glacial Maximum. Among the proposed processes, the ice albedo feedback, the elevation-mass balance feedback and the desertification effect over the ice sheet were found to be the dominant processes for the ice-sheet mass balance. For the elevation-mass balance feedback, the temperature lapse rate over the ice sheet is proposed to be weaker than assumed in previous studies. Within the plausible range of parameters related to these processes, the ice sheet response to the orbital parameters and atmospheric CO2 concentration for the last glacial/interglacial cycle was simulated in terms of both ice volume and geographical distribution, using a three-dimensional ice-sheet model. Careful treatment of climate-ice sheet feedback is essential for a reliable simulation of the ice sheet changes during ice age cycles.

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Investigating the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle

Climate of the Past Discussions ◽

10.5194/cpd-5-1013-2009 ◽

2009 ◽

Vol 5 (2) ◽

pp. 1013-1053 ◽

Cited By ~ 1

Author(s):

S. Bonelli ◽

S. Charbit ◽

M. Kageyama ◽

M.-N. Woillez ◽

G. Ramstein ◽

...

Keyword(s):

Northern Hemisphere ◽

Climate Model ◽

Ice Sheets ◽

Ice Sheet ◽

Co2 Concentration ◽

Atmospheric Co2 ◽

Glacial Cycle ◽

Last Glacial ◽

Atmospheric Co2 Concentration ◽

The Last Glacial

Abstract. A 2.5-dimensional climate model of intermediate complexity fully coupled with a 3-dimensional thermo-mechanical ice sheet model is used to simulate the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle and to investigate the ice sheets responses to both insolation and atmospheric CO2 concentration. This model reproduces the main phases of advance and retreat of Northern Hemisphere ice sheets during the last glacial cycle, although the amplitude of these variations is less pronounced than those based on sea level reconstructions. At the last glacial maximum, the simulated ice volume is 52.5×1015 m3 and the spatial distribution of both the American and Eurasian ice complexes is in reasonable agreement with observations, with the exception of the marine parts of these former ice sheets. A set of sensitivity studies has also been performed to assess the sensitivity of the Northern Hemisphere ice sheets to both insolation and atmospheric CO2. Our results suggest that the decrease of summer insolation is the main factor responsible for the early build up of the North American ice sheet around 120 kyr BP, in agreement with benthic foraminifera δ18O signals. In contrast, low insolation and low atmospheric CO2 concentration are both necessary to trigger a long-lasting glaciation over Eurasia.

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Atmospheric CO2 concentration and millennial-scale climate change during the last glacial period

Nature ◽

10.1038/32133 ◽

1998 ◽

Vol 392 (6671) ◽

pp. 59-62 ◽

Cited By ~ 92

Author(s):

B. Stauffer ◽

T. Blunier ◽

A. Dällenbach ◽

A. Indermühle ◽

J. Schwander ◽

...

Keyword(s):

Climate Change ◽

Co2 Concentration ◽

Atmospheric Co2 ◽

Glacial Period ◽

Last Glacial Period ◽

Last Glacial ◽

Atmospheric Co2 Concentration ◽

The Last Glacial ◽

Millennial Scale

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Glacial CO<sub>2</sub> cycle as a succession of key physical and biogeochemical processes

Climate of the Past Discussions ◽

10.5194/cpd-7-1767-2011 ◽

2011 ◽

Vol 7 (3) ◽

pp. 1767-1795 ◽

Cited By ~ 2

Author(s):

V. Brovkin ◽

A. Ganopolski ◽

D. Archer ◽

G. Munhoven

Keyword(s):

Radiative Forcing ◽

Marine Biology ◽

Deep Ocean ◽

Co2 Concentration ◽

Atmospheric Co2 ◽

Glacial Cycle ◽

Minimum Concentration ◽

Carbon Cycle Model ◽

Last Glacial ◽

The Last Glacial

Abstract. During glacial-interglacial cycles, atmospheric CO2 concentration varied by about 100 ppmv in amplitude. While testing mechanisms that had led to the low glacial CO2 level could be done in equilibrium model experiments, an ultimate goal is to explain CO2 changes in transient simulations through the complete glacial-interglacial cycle. A computationally efficient Earth System model of intermediate complexity CLIMBER-2 is used to simulate global biogeochemistry over the last glacial cycle (126 kyr). The physical core of the model (atmosphere, ocean, land and ice sheets) is driven by orbital changes and reconstructed radiative forcing from greenhouses gases, ice, and aeolian dust. The carbon cycle model is able to reproduce the main features of the CO2 changes: a 50 ppmv CO2 drop during glacial inception, a minimum concentration at the last glacial maximum by 80 ppmv lower than the Holocene value, and an abrupt 60 ppmv CO2 rise during the deglaciation. The model deep ocean δ13C also resembles reconstructions from deep-sea cores. The main drivers of atmospheric CO2 evolve with time: changes in sea surface temperatures and in the volume of bottom water of southern origin controls atmospheric CO2 during the glacial inception and deglaciation, while changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycle, respectively. These feedback mechanisms could also significantly impact the ultimate climate response to the anthropogenic perturbation.

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Glacial CO<sub>2</sub> cycle as a succession of key physical and biogeochemical processes

Climate of the Past ◽

10.5194/cp-8-251-2012 ◽

2012 ◽

Vol 8 (1) ◽

pp. 251-264 ◽

Cited By ~ 66

Author(s):

V. Brovkin ◽

A. Ganopolski ◽

D. Archer ◽

G. Munhoven

Keyword(s):

Radiative Forcing ◽

Marine Biology ◽

Deep Ocean ◽

Co2 Concentration ◽

Atmospheric Co2 ◽

Glacial Cycle ◽

Minimum Concentration ◽

Carbon Cycle Model ◽

Last Glacial ◽

The Last Glacial

Abstract. During glacial-interglacial cycles, atmospheric CO2 concentration varied by about 100 ppmv in amplitude. While testing mechanisms that have led to the low glacial CO2 level could be done in equilibrium model experiments, an ultimate goal is to explain CO2 changes in transient simulations through the complete glacial-interglacial cycle. The computationally efficient Earth System model of intermediate complexity CLIMBER-2 is used to simulate global biogeochemistry over the last glacial cycle (126 kyr). The physical core of the model (atmosphere, ocean, land and ice sheets) is driven by orbital changes and reconstructed radiative forcing from greenhouses gases, ice, and aeolian dust. The carbon cycle model is able to reproduce the main features of the CO2 changes: a 50 ppmv CO2 drop during glacial inception, a minimum concentration at the last glacial maximum 80 ppmv lower than the Holocene value, and an abrupt 60 ppmv CO2 rise during the deglaciation. The model deep ocean δ13C also resembles reconstructions from deep-sea cores. The main drivers of atmospheric CO2 evolve in time: changes in sea surface temperatures and in the volume of bottom water of southern origin control atmospheric CO2 during the glacial inception and deglaciation; changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycle, respectively. These feedback mechanisms could also significantly impact the ultimate climate response to the anthropogenic perturbation.

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