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

1988 ◽  
Vol 10 ◽  
pp. 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.

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 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.

Mineral aerosols: a comparison of the last glacial maximum and preindustrial Holocene

2000 ◽  
Vol 37 (5) ◽  
pp. 751-767 ◽  
Author(s):  
M C Reader ◽  
I Fung ◽  
N McFarlane
Keyword(s):  
Last Glacial Maximum ◽  
Mineral Dust ◽  
Ice Cores ◽  
Glacial Maximum ◽  
Dust Aerosol ◽  
Climate Modelling ◽  
Polar Ice ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A passive mineral dust aerosol model based on source strengths deduced from polar ice core dust concentrations is introduced into the Canadian Centre for Climate Modelling and Analysis (CCCma) second-generation atmospheric general circulation model (GCMII) and used to compare features of the fine particle mineral dust aerosol in a last glacial maximum (LGM) simulation to those of a preindustrial Holocene (MOD) dust simulation. The resulting dust optical thickness is 8-16 times greater over most of the globe during the LGM. The model displays several seasonal characteristics observed in present-day satellite observations of dust, such as the summer maximum over the Arabian Sea and the seasonal north-south shift of the Sahara-Sahel plume. Both of these features are also present in the LGM simulation, though there are some noticeable differences in seasonal variation of dust between the last glacial maximum and the preindustrial Holocene. Since the simulated dust lifetimes are very similar for the MOD and LGM climates, it seems that increased LGM dust lifetime is not the major reason for the observed increase in dust concentration in polar ice cores during the LGM relative to the present.

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

2012 ◽  
Vol 9 (10) ◽  
pp. 3961-3977 ◽  
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 ◽  
Before Present ◽  
Concentration Difference ◽  
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 represents a valuable constraint on the geographical location of the 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 of the 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 relative 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, as suggested from previous bipolar methane concentration records. Starting at 21 000 years before present, i.e. several millennia 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 thus find that the boreal and tropical methane sources increased by approximately the same factor during Termination 1. We hypothesise that latitudinal shifts in the Intertropical Convergence Zone (ITCZ) and the monsoon system contribute, either by dislocation of the methane source regions or, in case of the ITCZ, also by changing the relative atmospheric volumes of the Northern and Southern Hemispheres, to the subtle variations in the relative interpolar concentration difference on glacial/interglacial as well as on millennial time scales.

Reconstructions of the past distribution of Testudo graeca mitochondrial lineages in the Middle East and Transcaucasia support multiple refugia since the Last Glacial Maximum

2021 ◽  
pp. 10-17
Author(s):  
Oguz Turkozan
Keyword(s):  
Middle East ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Testudo Graeca ◽  
Last Glacial ◽  
The Past ◽  
Precipitation Seasonality ◽  
Multiple Refugia ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A cycle of glacial and interglacial periods in the Quaternary caused species’ ranges to expand and contract in response to climatic and environmental changes. During interglacial periods, many species expanded their distribution ranges from refugia into higher elevations and latitudes. In the present work, we projected the responses of the five lineages of Testudo graeca in the Middle East and Transcaucasia as the climate shifted from the Last Glacial Maximum (LGM, Mid – Holocene), to the present. Under the past LGM and Mid-Holocene bioclimatic conditions, models predicted relatively more suitable habitats for some of the lineages. The most significant bioclimatic variables in predicting the present and past potential distribution of clades are the precipitation of the warmest quarter for T. g. armeniaca (95.8 %), precipitation seasonality for T. g. buxtoni (85.0 %), minimum temperature of the coldest month for T. g. ibera (75.4 %), precipitation of the coldest quarter for T. g. terrestris (34.1 %), and the mean temperature of the driest quarter for T. g. zarudyni (88.8 %). Since the LGM, we hypothesise that the ranges of lineages have either expanded (T. g. ibera), contracted (T. g. zarudnyi) or remained stable (T. g. terrestris), and for other two taxa (T. g. armeniaca and T. g. buxtoni) the pattern remains unclear. Our analysis predicts multiple refugia for Testudo during the LGM and supports previous hypotheses about high lineage richness in Anatolia resulting from secondary contact.

Sign in / Sign up

Export Citation Format

Share Document