PMIP-carbon: towards a multi-models comparison of climate-carbon interactions at the Last Glacial Maximum

2020 ◽  
Author(s):  
Nathaelle Bouttes ◽  
Ruza Ivanovic ◽  
Ayako Abe-Ouchi ◽  
Hidetaka Kobayashi ◽  
Laurie Menviel ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Carbon Isotopes ◽  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Ice Cores ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Intercomparison Project ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>More and more climate models now include the carbon cycle, but multi-models studies of climate-carbon simulations within the Climate Model Intercomparison Project (CMIP) are limited to present and future time periods. In addition, the carbon cycle is not considered in the simulations of past periods analysed within the Paleoclimate Modelling Intercomparison Project (PMIP). Yet, climate-carbon interactions are crucial to anticipate future atmospheric CO<sub>2</sub> concentrations and their impact on climate. Such interactions can change depending on the background climate, it is thus necessary to compare model results among themselves and to data for past periods with different climates such as the Last Glacial Maximum (LGM).</p><p>The Last Glacial Maximum, around 21,000 years ago, was about 4°C colder than the pre-industrial, and associated with large ice sheets on the American and Eurasian continents. It is one of the best documented periods thanks to numerous paleoclimate archives such as marine sediment cores and ice cores. Despite this period having been studied for years, no consensus on the causes of the lower atmospheric CO<sub>2</sub> concentration at the time (around 180 ppm) has been reached and models still struggle to simulate these low CO<sub>2</sub> values. The ocean, which contains around 40 times more carbon than the atmosphere, likely plays a key role, but models tend to simulate ocean circulation changes in disagreement with proxy data, such as carbon isotopes.</p><p>This new project aims at comparing, for the first time, the carbon cycle representation at the Last Glacial Maximum from general circulation models and intermediate complexity models. We will explain the protocol and present first results in terms of carbon storage in the main reservoirs (atmosphere, land and ocean) and their link to key climate variables such as temperature, sea ice and ocean circulation. The use of coupled climate-carbon models will not only allow to compare changes in the carbon cycle in models and analyse their causes, but it will also enable us to better compare to indirect data related to the carbon cycle such as carbon isotopes.</p>

scholarly journals N2O Measurements on Air Extracted from Antarctic Ice Cores (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 222-222
Author(s):  
D. Zardini ◽  
D. Raynaud ◽  
D. Scharffe ◽  
W. Seiler
Keyword(s):  
Last Glacial Maximum ◽  
Ice Cores ◽  
Experimental Tests ◽  
Glacial Maximum ◽  
Recent Period ◽  
Air Samples ◽  
Last Glacial ◽  
Original Procedure ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A method has been developed for measuring N2O concentrations in the air extracted from the bubbles contained in ice cores. The air extraction is performed by cutting the ice into very small pieces with a rotating knife, in a controlled atmosphere. The N2O concentrations are measured by gas chromatography. The complete original procedure will be discussed, and the results of the different experimental tests given, with a discussion of the uncertainties.This method has been used to perform about 40 measurements on Antarctic ice samples. Ten air samples from the D57 core date approximately from the beginning of the seventeenth and twentieth centuries. The others were taken from the Dome C core and date from the Holocene and the period around the Last Glacial Maximum. The D57 results are in agreement with those of Pearman and others (1986), leading to a similar pre-industrial N2O level (270-290 ppb volume). Furthermore, our Dome C results suggest that during the Last Glacial Maximum atmospheric N2O content was not drastically different from the recent period.

scholarly journals Dust sources and deposition during the last glacial maximum and current climate: A comparison of model results with paleodata from ice cores and marine sediments

1999 ◽  
Vol 104 (D13) ◽  
pp. 15895-15916 ◽  
Author(s):  
Natalie Mahowald ◽  
Karen Kohfeld ◽  
Margaret Hansson ◽  
Yves Balkanski ◽  
Sandy P. Harrison ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Marine Sediments ◽  
Ice Cores ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Current Climate ◽  
Dust Sources ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Ice-sheet mass balance during the last glacial maximum

1997 ◽  
Vol 25 ◽  
pp. 145-152 ◽  
Author(s):  
Gilles Ramstein ◽  
Adeline Fabre ◽  
Sophie Pinot ◽  
Catherine Ritz ◽  
Sylvie Joussaume
Keyword(s):  
Last Glacial Maximum ◽  
General Circulation ◽  
Ice Sheets ◽  
Ice Sheet ◽  
General Circulation Models ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Intercomparison Project ◽  
The Last Glacial Maximum ◽  
The Last Glacial

In the framework of the Paleoclimate Modelling Intercomparison Project (PMIP), simulations of the Last Glacial Maximum (LGM) have- been performed. More than 10 different atmospheric general circulation models (AGCMs) have been used with the same boundary conditions: sea-surface temperatures prescribed by CLIMAP (1981), ice-sheet reconstruction provided by Peltier (1994), change in insolation, and reduced CO2 content. One of the major questions is to investigate whether the simulations of the LGM are in equilibrium with the prescribed ice-sheet reconstruction. To answer this question, we have used two different approaches. First, we analyze the results of a sel of LGM simulations performed with different versions of the Laboratoire de Meteorolo-gie Dynamique (LMD) AGCM and study the hydrologic and snow- budgets over the Laurcntide and Fennoscandian ice sheets. Second, we use the AGCM outputs to force an ice-sheet model in order to investigate its ability to maintain the ice sheets as reconstructed by CLIMAP (1981) or Peltier (1994).

scholarly journals High-resolution interpolar difference of atmospheric methane around the Last Glacial Maximum

2012 ◽  
Vol 9 (5) ◽  
pp. 5471-5508 ◽  
Author(s):  
M. Baumgartner ◽  
A. Schilt ◽  
O. Eicher ◽  
J. Schmitt ◽  
J. Schwander ◽  
...  
Keyword(s):  
High Resolution ◽  
Last Glacial Maximum ◽  
Methane Concentration ◽  
Ice Cores ◽  
Glacial Maximum ◽  
Atmospheric Methane ◽  
Before Present ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Reconstructions of past atmospheric methane concentrations are available from ice cores from both, Greenland and Antarctica. The difference observed between the two polar methane concentration levels is a valuable additional parameter which allows to constrain the geographical location of the responsible methane sources. Here we present new high-resolution methane records from the North Greenland Ice Core Project (NGRIP) and the European Project for Ice Coring in Antarctica (EPICA) Dronning Maud Land (EDML) ice cores covering Termination 1, the Last Glacial Maximum, and parts of the last glacial back to 32 000 years before present. Due to the high-resolution records the synchronisation between the ice cores from NGRIP and EDML is considerably improved and the interpolar concentration difference of methane is determined with unprecedented precision and temporal resolution. Relative to the mean methane concentration, we find a rather stable positive interpolar difference throughout the record with its minimum value of 3.7 ± 0.7 % between 21 900–21 200 years before present, which is higher than previously estimated in this interval close to the Last Glacial Maximum. This implies that Northern Hemisphere boreal wetland sources were never completely shut off during the peak glacial. Starting at 21 000 years before present, i.e. severval millenia prior to the transition into the Holocene, the relative interpolar difference becomes even more positive and stays at a fairly stable level of 6.5 ± 0.8 % during Termination 1. We hypothesise that the anti-correlation observed in the monsoon records from the Northern and Southern Hemispheres induces a methane source redistribution within lower latitudes, which could explain parts of the variations in the interpolar difference.

Was the Atlantic a predominantly Polar Ocean during the last glacial?

2020 ◽  
Author(s):  
Marleen Lausecker ◽  
Freya Hemsing ◽  
Thomas Krengel ◽  
Julius Förstel ◽  
Andrea Schröder-Ritzrau ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Cold Water ◽  
World Ocean ◽  
Ice Cores ◽  
Glacial Maximum ◽  
Global Ocean ◽  
Last Glacial ◽  
The Last Glacial

<p>The Last Glacial Maximum (LGM) is marked by significant cooling of the global ocean, which was recently estimated to 2.6°C using noble gases trapped in ice cores (1). This cooling is not equally distributed throughout the world oceans, since global ocean circulation models predict regional temperature anomalies during the LGM of up to 7°C (annually and zonally averaged) when compared to modern interior ocean temperature (2). The oceans deep interior thus became haline stratified (3) due to the drop in temperature to near freezing and the global increase in salinity from ice sheet growth. In contrast to a deepening of the modern thermocline as a result of anthropogenic global warming, cooling causes the thermocline to rise in the sub-tropics as more polar waters enter the mid-depth ocean.</p><p>Here we present glacial thermocline temperature reconstructions since the LGM based on the Li/Mg ratio in aragonite skeletons of precisely dated cold-water corals. Corals have been collected from 300-1000m water depths from sites in the northern and southern Atlantic (62°N to 25°S) and demonstrate synchronous 5 - 7°C glacial cooling, and a dramatic shoaling of the thermocline. Through the deglaciation the warming of the upper thermocline ocean occurs early in the southern hemisphere followed by fluctuating warming and thermocline deepening in the northern Hemisphere, which supports the oceanic climate seesaw proposed by Stocker and Johnson in 2003 (4). We thus propose dramatic changes in export of polar waters towards the Equator and augmented subsurface ocean stratification leading to a mostly polar Atlantic with a shallow permanent thermocline. This shoaling possibly increased the rate of nutrient recycling causing higher biological surface ocean activity and the cooling promoted carbon storage. During the glacial, we assume an atmospheric forcing, such as equatorward displacement of the Hadley circulation, to steer the glacial polar water advance as mid-depth boundary currents in the northern and southern hemisphere to effectively spread the cold water through the entire mid-depth Atlantic.</p><p>References:</p><ol><li>Bereiter et al.: Mean global ocean temperatures during the last glacial transition. Nature <strong>553</strong>, 39-44 (2018).</li> <li>Ballarotta et al.: Last Glacial Maximum world ocean simulations at eddy-permitting and coarse resolutions: do eddies contribute to a better consistency between models and palaeoproxies?, Clim. Past <strong>9</strong>, 2669-2686 (2013).</li> <li>Adkins et al.: The Salinity, Temperature, and d18O of the Glacial Deep Ocean. Science <strong>298</strong>, 1769-1773 (2002).</li> <li>Stocker and Johnsen: A minimum thermodynamic model for the bipolar seesaw, Paleoceanography <strong>18</strong>, 1087 (2003).</li> </ol>

A 3000-yr Annually Laminated Stalagmite Record of the Last Glacial Maximum from Hulu Cave, China

2015 ◽  
Vol 83 (2) ◽  
pp. 360-369 ◽  
Author(s):  
Fucai Duan ◽  
Jiangying Wu ◽  
Yongjin Wang ◽  
R. Lawrence Edwards ◽  
Hai Cheng ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Hydrological Cycle ◽  
Glacial Maximum ◽  
Solar Cycles ◽  
Last Glacial ◽  
The North ◽  
Annual Layer ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A high-resolution, annual layer-counted and 230Th-dated multi-proxy record is constructed from a stalagmite in Hulu Cave, China. These proxies, including δ18O, annual layer thickness (ALT), gray level (GL) and Sr/Ca, cover a time span of ~ 3000 yr from 21 to 24 ka. The physical proxies (ALT and GL) and the geochemical index (Sr/Ca), all primarily reflecting karst hydrological processes, vary in concert and their coherence is supported by wavelet analyses. Variations in the δ18O data agree with fluctuations in the ALT and Sr/Ca records on multi-decadal to centennial scales, suggesting that the Hulu δ18O signal is strongly associated with varying local rainfall amounts on short timescales. A monsoon failure event at ~ 22.2 ka correlates with a decrease in tropical rainfall, a reduction in global CH 4 and an ice-rafted event in the North Atlantic. This correlation highlights roles of the Asian monsoon and tropical hydrological cycle in modulating global CH 4, because the high-latitude emission was inhibited during the Last Glacial Maximum (LGM). Spectral analysis of the δ18O record displays peaks at periodicities of 139, 59, 53, 43, 30, 23 and 19"15 yr. The absence of typical centennial solar cycles may be related to muted changes in ocean circulation during the LGM.

Tropical paleoclimates at the Last Glacial Maximum: comparison of Paleoclimate Modeling Intercomparison Project (PMIP) simulations and paleodata

1999 ◽  
Vol 15 (11) ◽  
pp. 857-874 ◽  
Author(s):  
S. Pinot ◽  
G. Ramstein ◽  
S. P. Harrison ◽  
I. C. Prentice ◽  
J. Guiot ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Paleoclimate Modeling ◽  
Intercomparison Project ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Ice-sheet mass balance during the last glacial maximum

1997 ◽  
Vol 25 ◽  
pp. 145-152 ◽  
Author(s):  
Gilles Ramstein ◽  
Adeline Fabre ◽  
Sophie Pinot ◽  
Catherine Ritz ◽  
Sylvie Joussaume
Keyword(s):  
Last Glacial Maximum ◽  
General Circulation ◽  
Ice Sheets ◽  
Ice Sheet ◽  
General Circulation Models ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Intercomparison Project ◽  
The Last Glacial Maximum ◽  
The Last Glacial

In the framework of the Paleoclimate Modelling Intercomparison Project (PMIP), simulations of the Last Glacial Maximum (LGM) have- been performed. More than 10 different atmospheric general circulation models (AGCMs) have been used with the same boundary conditions: sea-surface temperatures prescribed by CLIMAP (1981), ice-sheet reconstruction provided by Peltier (1994), change in insolation, and reduced CO2 content. One of the major questions is to investigate whether the simulations of the LGM are in equilibrium with the prescribed ice-sheet reconstruction. To answer this question, we have used two different approaches. First, we analyze the results of a sel of LGM simulations performed with different versions of the Laboratoire de Meteorolo-gie Dynamique (LMD) AGCM and study the hydrologic and snow- budgets over the Laurcntide and Fennoscandian ice sheets. Second, we use the AGCM outputs to force an ice-sheet model in order to investigate its ability to maintain the ice sheets as reconstructed by CLIMAP (1981) or Peltier (1994).

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