scholarly journals Atmospheric CO2 Variations over the Last Climatic Cycle (160 000 Years), Deduced from the Vostok Ice Core, Antarctica (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 199-200 ◽  
Author(s):  
J.M. Barnola ◽  
C. Genthon ◽  
D. Raynaud ◽  
J. Jouzel ◽  
Ye.S. Korotkevich ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Sea Level ◽  
Time Resolution ◽  
Ice Core ◽  
Ice Age ◽  
Interglacial Period ◽  
High Latitudes ◽  
Last Interglacial ◽  
Isotope Record ◽  
Stable Isotope Record

This is a summary of the main CO2 results obtained from the Vostok core which have been presented in two papers recently published (Barnola and others 1987; Genthon and others 1987). Previous results of ice-core analysis have already provided valuable information on atmospheric CO2 variations associated with anthropogenic activities (Neftel and others 1985, Raynaud and Barnola 1985[a], Pearman and others 1986) and with climatic variations back to about 40 ka ago (Delmas and others 1980, Neftel and others 1982, Raynaud and Barnola 1985[b]). The Antarctic Vostok ice core provides a unique opportunity for extending the ice record of atmospheric CO2 variations over the last glacial–interglacial cycle back to the end of the penultimate ice age, about 160 ka ago. CO2 measurements were made at 66 different depth levels on the air enclosed in the 2083 m long core taken at Vostok Station. The air was extracted by crushing the ice, under vacuum, in a cold-room, and analysed by gas chromatography (Barnola and others 1983). The selected sampling corresponds to a time resolution between two neighbouring levels which range approximately from 2000 to 4500 years. The ages quoted in this abstract are based on the Vostok ice chronology given by Lorius and others (1985) and take into account the fact that the air is trapped in the firn well after snow deposition (between about 2500 and 4300 years after precipitation in the case of Vostok). The CO2 variations observed are compared directly with the changes in Antarctic temperature as depicted by the stable-isotope record of the Vostok ice (Jouzel and others 1988, this volume). Furthermore, a CO2-orbital forcing-climate interaction is suggested by spectral analysis of the CO2 and temperature profiles, which both show a concentration of variance around orbital frequencies. The temperature profile is clearly dominated by a 40 ka period (which can be related to the obliquity frequency) (Jouzel and others 1988, this volume), whereas the CO2 record exhibits a well-defined 21 ka peak (which can be related to the precession frequencies) and only a weak and doubtful 40 ka peak. To check the relative influence of CO2 and orbital forcings on the temperature at Vostok, we modelled the temperature signal deduced from the stable-isotope record of the ice as a response to CO2, Northern Hemisphere ice volume and local insolation forcings. The results indicate that more than 90% of the temperature variance can be explained by these three kinds of forcing and that the contribution of the CO2 radiative effect associated with an amplification factor (which should reflect the long-term feed-back mechanisms) lies between 27 and 85% of the explained variance. This approach stresses the important role that CO2 may generally have played in determining the Earth’s climate during the late Pleistocene. The most obvious feature of the Vostok CO2 record lies in its high correlation (r2 = 0.79) with the climatic record. The results obtained show high CO2 concentrations during warm periods (mean CO2 values of 263 ppm volume for the Holocene and 272 ppm volume for the last interglacial period) and low concentrations (between about 240 and 190 ppm volume) over glacial periods. Within the last glaciation, the CO2 concentrations are higher during the first part (mean CO2 value of 230 ppm volume between about 110–65 ka B.P.) than during the second part (203 ppm volume between 65–15 ka B.P.); the second part also indicates that climatic conditions were colder. Our results point to some limitation on the possible mechanisms driving the atmospheric CO2 variations and, in particular, the influence of some oceanic areas or of changes in sea-level (see, for example, Broecker and Peng 1986). The weak 41 ka cycle (this cycle seems to be a characteristic of the spectra of the proxy data for high latitudes) in our CO2 record suggests that high latitudes may not have a major influence on CO2 variations. Furthermore, the phase relationship between CO2 and the temperature variations indicates that at the beginning of the two deglaciations around 145ka B.P. and 15ka B.P., taking into account the time resolution of our profile, the CO2 increases roughly in phase with the Vostok temperature. As surface-temperature changes around Antarctica are expected to lead to changes in sea-level (see, for instance, CLIMAP Project Members 1984), our results suggest that the CO2 increase cannot lag the increase in sea-level and thus that this parameter cannot initiate the CO2 variation recorded at the beginning of those two deglaciations. Nevertheless, this does not rule out influence of variations in sea-level on atmospheric CO2 for other periods of interest, in particular during the last interglacial–glacial transition, where the CO2 lags the Vostok temperature.

scholarly journals Atmospheric CO2 Variations over the Last Climatic Cycle (160 000 Years), Deduced from the Vostok Ice Core, Antarctica (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 199-200
Author(s):  
J.M. Barnola ◽  
C. Genthon ◽  
D. Raynaud ◽  
J. Jouzel ◽  
Ye.S. Korotkevich ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Sea Level ◽  
Time Resolution ◽  
Ice Core ◽  
Ice Age ◽  
Interglacial Period ◽  
High Latitudes ◽  
Last Interglacial ◽  
Isotope Record ◽  
Stable Isotope Record

This is a summary of the main CO2 results obtained from the Vostok core which have been presented in two papers recently published (Barnola and others 1987; Genthon and others 1987).Previous results of ice-core analysis have already provided valuable information on atmospheric CO2 variations associated with anthropogenic activities (Neftel and others 1985, Raynaud and Barnola 1985[a], Pearman and others 1986) and with climatic variations back to about 40 ka ago (Delmas and others 1980, Neftel and others 1982, Raynaud and Barnola 1985[b]). The Antarctic Vostok ice core provides a unique opportunity for extending the ice record of atmospheric CO2 variations over the last glacial–interglacial cycle back to the end of the penultimate ice age, about 160 ka ago.CO2 measurements were made at 66 different depth levels on the air enclosed in the 2083 m long core taken at Vostok Station. The air was extracted by crushing the ice, under vacuum, in a cold-room, and analysed by gas chromatography (Barnola and others 1983). The selected sampling corresponds to a time resolution between two neighbouring levels which range approximately from 2000 to 4500 years. The ages quoted in this abstract are based on the Vostok ice chronology given by Lorius and others (1985) and take into account the fact that the air is trapped in the firn well after snow deposition (between about 2500 and 4300 years after precipitation in the case of Vostok). The CO2 variations observed are compared directly with the changes in Antarctic temperature as depicted by the stable-isotope record of the Vostok ice (Jouzel and others 1988, this volume).Furthermore, a CO2-orbital forcing-climate interaction is suggested by spectral analysis of the CO2 and temperature profiles, which both show a concentration of variance around orbital frequencies. The temperature profile is clearly dominated by a 40 ka period (which can be related to the obliquity frequency) (Jouzel and others 1988, this volume), whereas the CO2 record exhibits a well-defined 21 ka peak (which can be related to the precession frequencies) and only a weak and doubtful 40 ka peak. To check the relative influence of CO2 and orbital forcings on the temperature at Vostok, we modelled the temperature signal deduced from the stable-isotope record of the ice as a response to CO2, Northern Hemisphere ice volume and local insolation forcings. The results indicate that more than 90% of the temperature variance can be explained by these three kinds of forcing and that the contribution of the CO2 radiative effect associated with an amplification factor (which should reflect the long-term feed-back mechanisms) lies between 27 and 85% of the explained variance. This approach stresses the important role that CO2 may generally have played in determining the Earth’s climate during the late Pleistocene.The most obvious feature of the Vostok CO2 record lies in its high correlation (r2 = 0.79) with the climatic record. The results obtained show high CO2 concentrations during warm periods (mean CO2 values of 263 ppm volume for the Holocene and 272 ppm volume for the last interglacial period) and low concentrations (between about 240 and 190 ppm volume) over glacial periods. Within the last glaciation, the CO2 concentrations are higher during the first part (mean CO2 value of 230 ppm volume between about 110–65 ka B.P.) than during the second part (203 ppm volume between 65–15 ka B.P.); the second part also indicates that climatic conditions were colder.Our results point to some limitation on the possible mechanisms driving the atmospheric CO2 variations and, in particular, the influence of some oceanic areas or of changes in sea-level (see, for example, Broecker and Peng 1986). The weak 41 ka cycle (this cycle seems to be a characteristic of the spectra of the proxy data for high latitudes) in our CO2 record suggests that high latitudes may not have a major influence on CO2 variations. Furthermore, the phase relationship between CO2 and the temperature variations indicates that at the beginning of the two deglaciations around 145ka B.P. and 15ka B.P., taking into account the time resolution of our profile, the CO2 increases roughly in phase with the Vostok temperature. As surface-temperature changes around Antarctica are expected to lead to changes in sea-level (see, for instance, CLIMAP Project Members 1984), our results suggest that the CO2 increase cannot lag the increase in sea-level and thus that this parameter cannot initiate the CO2 variation recorded at the beginning of those two deglaciations. Nevertheless, this does not rule out influence of variations in sea-level on atmospheric CO2 for other periods of interest, in particular during the last interglacial–glacial transition, where the CO2 lags the Vostok temperature.

scholarly journals Greenland ice sheet contribution to sea level rise during the last interglacial period: a modelling study driven and constrained by ice core data

2013 ◽  
Vol 9 (1) ◽  
pp. 353-366 ◽  
Author(s):  
A. Quiquet ◽  
C. Ritz ◽  
H. J. Punge ◽  
D. Salas y Mélia
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Interglacial Period ◽  
Last Interglacial ◽  
Intergovernmental Panel ◽  
Orbital Configuration ◽  
Global Sea Level

Abstract. As pointed out by the forth assessment report of the Intergovernmental Panel on Climate Change, IPCC-AR4 (Meehl et al., 2007), the contribution of the two major ice sheets, Antarctica and Greenland, to global sea level rise, is a subject of key importance for the scientific community. By the end of the next century, a 3–5 °C warming is expected in Greenland. Similar temperatures in this region were reached during the last interglacial (LIG) period, 130–115 ka BP, due to a change in orbital configuration rather than to an anthropogenic forcing. Ice core evidence suggests that the Greenland ice sheet (GIS) survived this warm period, but great uncertainties remain about the total Greenland ice reduction during the LIG. Here we perform long-term simulations of the GIS using an improved ice sheet model. Both the methodologies chosen to reconstruct palaeoclimate and to calibrate the model are strongly based on proxy data. We suggest a relatively low contribution to LIG sea level rise from Greenland melting, ranging from 0.7 to 1.5 m of sea level equivalent, contrasting with previous studies. Our results suggest an important contribution of the Antarctic ice sheet to the LIG highstand.

Lacustrine stable isotope record of precipitation changes in Nicaragua during the Little Ice Age and Medieval Climate Anomaly

Geology ◽  
2013 ◽  
Vol 41 (2) ◽  
pp. 151-154 ◽  
Author(s):  
Nathan D. Stansell ◽  
Byron A. Steinman ◽  
Mark B. Abbott ◽  
Michael Rubinov ◽  
Manuel Roman-Lacayo
Keyword(s):  
Stable Isotope ◽  
Little Ice Age ◽  
Ice Age ◽  
Medieval Climate Anomaly ◽  
Climate Anomaly ◽  
Isotope Record ◽  
Precipitation Changes ◽  
Stable Isotope Record

scholarly journals Sensitivity of interglacial Greenland temperature and δ<sup>18</sup>O: ice core data, orbital and increased CO<sub>2</sub> climate simulations

2011 ◽  
Vol 7 (3) ◽  
pp. 1041-1059 ◽  
Author(s):  
V. Masson-Delmotte ◽  
P. Braconnot ◽  
G. Hoffmann ◽  
J. Jouzel ◽  
M. Kageyama ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Ice Core ◽  
Ice Sheet ◽  
Ice Cores ◽  
Interglacial Period ◽  
Orbital Forcing ◽  
Last Interglacial ◽  
Core Data ◽  
Climate Simulations ◽  
The Impact

Abstract. The sensitivity of interglacial Greenland temperature to orbital and CO2 forcing is investigated using the NorthGRIP ice core data and coupled ocean-atmosphere IPSL-CM4 model simulations. These simulations were conducted in response to different interglacial orbital configurations, and to increased CO2 concentrations. These different forcings cause very distinct simulated seasonal and latitudinal temperature and water cycle changes, limiting the analogies between the last interglacial and future climate. However, the IPSL-CM4 model shows similar magnitudes of Arctic summer warming and climate feedbacks in response to 2 × CO2 and orbital forcing of the last interglacial period (126 000 years ago). The IPSL-CM4 model produces a remarkably linear relationship between TOA incoming summer solar radiation and simulated changes in summer and annual mean central Greenland temperature. This contrasts with the stable isotope record from the Greenland ice cores, showing a multi-millennial lagged response to summer insolation. During the early part of interglacials, the observed lags may be explained by ice sheet-ocean feedbacks linked with changes in ice sheet elevation and the impact of meltwater on ocean circulation, as investigated with sensitivity studies. A quantitative comparison between ice core data and climate simulations requires stability of the stable isotope – temperature relationship to be explored. Atmospheric simulations including water stable isotopes have been conducted with the LMDZiso model under different boundary conditions. This set of simulations allows calculation of a temporal Greenland isotope-temperature slope (0.3–0.4‰ per °C) during warmer-than-present Arctic climates, in response to increased CO2, increased ocean temperature and orbital forcing. This temporal slope appears half as large as the modern spatial gradient and is consistent with other ice core estimates. It may, however, be model-dependent, as indicated by preliminary comparison with other models. This suggests that further simulations and detailed inter-model comparisons are also likely to be of benefit. Comparisons with Greenland ice core stable isotope data reveals that IPSL-CM4/LMDZiso simulations strongly underestimate the amplitude of the ice core signal during the last interglacial, which could reach +8–10 °C at fixed-elevation. While the model-data mismatch may result from missing positive feedbacks (e.g. vegetation), it could also be explained by a reduced elevation of the central Greenland ice sheet surface by 300–400 m.

scholarly journals Coupled regional climate–ice-sheet simulation shows limited Greenland ice loss during the Eemian

2013 ◽  
Vol 9 (4) ◽  
pp. 1773-1788 ◽  
Author(s):  
M. M. Helsen ◽  
W. J. van de Berg ◽  
R. S. W. van de Wal ◽  
M. R. van den Broeke ◽  
J. Oerlemans
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Regional Climate ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Interglacial Period ◽  
Temperature Record ◽  
Last Interglacial ◽  
Central Dome

Abstract. During the last interglacial period (Eemian, 130–115 kyr BP) eustatic global sea level likely peaked at > 6 m above the present-day level, but estimates of the contribution of the Greenland Ice Sheet vary widely. Here we use an asynchronously two-way-coupled regional climate–ice-sheet model, which includes physically realistic feedbacks between the changing ice sheet topography and climate forcing. Our simulation results in a contribution from the Greenland Ice Sheet to the Eemian sea level highstand between 1.2 and 3.5 m, with a most likely value of 2.1 m. Simulated Eemian ice loss in Greenland is dominated by the rapid retreat of the southwestern margin; two-thirds of the ice loss occurred south of 70° N. The southern dome survived the Eemian and remained connected to the central dome. Large-scale ice sheet retreat is prevented in areas with high accumulation. Our results broadly agree with ice-core-inferred elevation changes and marine records, but it does not match with the ice-core-derived temperature record from northern Greenland. During maximum Eemian summertime insolation, Greenland mass loss contributed ~ 0.5 m kyr−1 to sea level rise, 24% of the reconstructed total rate of sea level rise. Next to that, a difference of > 3 m remains between our maximum estimate of the Greenland contribution and the reconstructed minimum value of the global eustatic Eemian highstand. Hence, the Antarctic Ice Sheet must also have contributed significantly to this sea level highstand.

scholarly journals Moderate Greenland ice sheet melt during the last interglacial constrained by present-day observations and paleo ice core reconstructions

2016 ◽  
Author(s):  
P.M. Langebroek ◽  
K.H. Nisancioglu
Keyword(s):  
Sea Level ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Atmospheric Temperature ◽  
Lapse Rate ◽  
Interglacial Period ◽  
Last Interglacial ◽  
Temperature Lapse Rate

Abstract. During the last interglacial period (LIG, ~ 130–115 ka before present, ka = 1000 yr) summer temperatures over Greenland were several degrees higher than today. It is likely that the Greenland ice sheet (GIS) was smaller than today, contributing to the reconstructed sea-level highstand of the LIG. However, the range of simulated GIS melt is large, and the location of the melt is uncertain. Here, we use temperature and precipitation patterns simulated by the Norwegian Earth System Model (NorESM) to investigate the volume, extent and stability of the GIS during the LIG. Present-day observations of ice sheet size, elevation and stability, together with paleo elevation information from five deep ice cores, are used to evaluate our ensemble of GIS simulations. Accepted simulations indicate a maximum GIS reduction equivalent to a global mean sea-level rise of 0.8–2.2 m compared to today, with most of the melt occurring in the southwest. The timing of the maximum ice melt over Greenland is simulated between 124 and 122 ka. We furthermore suggest a preferred mean value for the basal sliding parameter, relatively high PDD factors and an average to high atmospheric temperature lapse rate based on training the SICOPOLIS ice sheet model to observations and available LIG proxy data.

scholarly journals Sensitivity of interglacial Greenland temperature and δ<sup>18</sup>O to orbital and CO<sub>2</sub> forcing: climate simulations and ice core data

2011 ◽  
Vol 7 (3) ◽  
pp. 1585-1630 ◽  
Author(s):  
V. Masson-Delmotte ◽  
P. Braconnot ◽  
G. Hoffmann ◽  
J. Jouzel ◽  
M. Kageyama ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Ice Core ◽  
Ice Sheet ◽  
Ice Cores ◽  
Interglacial Period ◽  
Orbital Forcing ◽  
Last Interglacial ◽  
Core Data ◽  
Climate Simulations ◽  
The Impact

Abstract. The sensitivity of interglacial Greenland temperature to orbital and CO2 forcing is investigated using the NorthGRIP ice core data and coupled ocean-atmosphere IPSL-CM4 model simulations. These simulations were conducted in response to different interglacial orbital configurations, and to increased CO2 concentrations. These different forcings cause very distinct simulated seasonal and latitudinal temperature and water cycle changes, limiting the analogies between the last interglacial and future climate. However, the IPSL-CM4 model shows similar magnitudes of Arctic summer warming and climate feedbacks in response to 2 × CO2 and orbital forcing of the last interglacial period (126 000 yr ago). The IPSL model produces a remarkably linear relationship between top of atmosphere incoming summer solar radiation and simulated changes in summer and annual mean central Greenland temperature. This contrasts with the stable isotope record from the Greenland ice cores, showing a multi-millennial lagged response to summer insolation. During the early part of interglacials, the observed lags may be explained by ice sheet-ocean feedbacks linked with changes in ice sheet elevation and the impact of meltwater on ocean circulation, as investigated with sensitivity studies. A quantitative comparison between ice core data and climate simulations requires to explore the stability of the stable isotope – temperature relationship. Atmospheric simulations including water stable isotopes have been conducted with the LMDZiso model under different boundary conditions. This set of simulations allows to calculate a temporal Greenland isotope-temperature slope (0.3–0.4 ‰ per °C) during warmer than present Arctic climates, in response to increased CO2, increased ocean temperature and orbital forcing. This temporal slope appears twice as small as the modern spatial gradient and is consistent with other ice core estimates. A preliminary comparison with other model results implies that other mechanisms could also play a role. This suggests that further simulations and detailed inter-model comparisons are also likely to be of benefit. Comparisons with Greenland ice core stable isotope data reveals that IPSL/LMDZiso simulations strongly underestimate the amplitude of the ice core signal during the last interglacial, which could reach +8–10 °C at fixed-elevation. While the model-data mismatch may result from missing positive feedbacks (e.g. vegetation), it could also be explained by a reduced elevation of the central Greenland ice sheet surface by 300–400 m.

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