Session 19: Palaeoclimate and Palaeoenvironment Since the Last Glacial Maximum – Linking Marine, Ice Core and Terrestrial Records

GFF ◽  
2004 ◽  
Vol 126 (1) ◽  
pp. 126-133
Keyword(s):  
Last Glacial Maximum ◽  
Ice Core ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Response of methane emissions from wetlands to the Last Glacial Maximum and an idealized Dansgaard–Oeschger climate event: insights from two models of different complexity

2013 ◽  
Vol 9 (1) ◽  
pp. 149-171 ◽  
Author(s):  
B. Ringeval ◽  
P. O. Hopcroft ◽  
P. J. Valdes ◽  
P. Ciais ◽  
G. Ramstein ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
General Circulation ◽  
Ice Core ◽  
Glacial Maximum ◽  
Ch4 Emissions ◽  
Last Glacial ◽  
Emission Models ◽  
Time Periods ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. The role of different sources and sinks of CH4 in changes in atmospheric methane ([CH4]) concentration during the last 100 000 yr is still not fully understood. In particular, the magnitude of the change in wetland CH4 emissions at the Last Glacial Maximum (LGM) relative to the pre-industrial period (PI), as well as during abrupt climatic warming or Dansgaard–Oeschger (D–O) events of the last glacial period, is largely unconstrained. In the present study, we aim to understand the uncertainties related to the parameterization of the wetland CH4 emission models relevant to these time periods by using two wetland models of different complexity (SDGVM and ORCHIDEE). These models have been forced by identical climate fields from low-resolution coupled atmosphere–ocean general circulation model (FAMOUS) simulations of these time periods. Both emission models simulate a large decrease in emissions during LGM in comparison to PI consistent with ice core observations and previous modelling studies. The global reduction is much larger in ORCHIDEE than in SDGVM (respectively −67 and −46%), and whilst the differences can be partially explained by different model sensitivities to temperature, the major reason for spatial differences between the models is the inclusion of freezing of soil water in ORCHIDEE and the resultant impact on methanogenesis substrate availability in boreal regions. Besides, a sensitivity test performed with ORCHIDEE in which the methanogenesis substrate sensitivity to the precipitations is modified to be more realistic gives a LGM reduction of −36%. The range of the global LGM decrease is still prone to uncertainty, and here we underline its sensitivity to different process parameterizations. Over the course of an idealized D–O warming, the magnitude of the change in wetland CH4 emissions simulated by the two models at global scale is very similar at around 15 Tg yr−1, but this is only around 25% of the ice-core measured changes in [CH4]. The two models do show regional differences in emission sensitivity to climate with much larger magnitudes of northern and southern tropical anomalies in ORCHIDEE. However, the simulated northern and southern tropical anomalies partially compensate each other in both models limiting the net flux change. Future work may need to consider the inclusion of more detailed wetland processes (e.g. linked to permafrost or tropical floodplains), other non-wetland CH4 sources or different patterns of D–O climate change in order to be able to reconcile emission estimates with the ice-core data for rapid CH4 events.

scholarly journals The influence of föhn winds on Glacial Lake Washburn and palaeotemperatures in the McMurdo Dry Valleys, Antarctica, during the Last Glacial Maximum

2017 ◽  
Vol 29 (5) ◽  
pp. 457-467 ◽  
Author(s):  
M.K. Obryk ◽  
P.T. Doran ◽  
E.D. Waddington ◽  
C.P. Mckay
Keyword(s):  
Last Glacial Maximum ◽  
Ice Core ◽  
Glacial Maximum ◽  
Mcmurdo Dry Valleys ◽  
Glacial Lake ◽  
Dry Valleys ◽  
Glacial Lakes ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractLarge glacial lakes, including Glacial Lake Washburn, were present in the McMurdo Dry Valleys, Antarctica, during the Last Glacial Maximum (LGM) despite a colder and drier climate. To address the mechanism capable of generating enough meltwater to sustain these large lakes, a conceptual model was developed based on the warming potential of infrequent contemporary föhn winds. The model suggests that föhn winds were capable of generating enough meltwater to sustain large glacial lakes during the LGM by increasing degree days above freezing (DDAF) and prolonging the melt season. A present-day relationship between infrequent summer föhn winds and DDAF was established. It is assumed that the Taylor Dome ice core record represents large-scale palaeoclimatic variations for the McMurdo Dry Valleys region. This analysis suggests that because of the warming influence of the more frequent föhn winds, summer DDAF in the McMurdo Dry Valleys during the LGM were equivalent to present-day values, but this enhanced summer signal is not preserved in the annually averaged ice core temperature record.

scholarly journals Response of methane emissions from wetlands to the Last Glacial Maximum and an idealized Dansgaard-Oeschger climate event: insights from two models of different complexity

2012 ◽  
Vol 8 (4) ◽  
pp. 3093-3142 ◽  
Author(s):  
B. Ringeval ◽  
P. O. Hopcroft ◽  
P. J. Valdes ◽  
P. Ciais ◽  
G. Ramstein ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
General Circulation ◽  
Ice Core ◽  
Circulation Model ◽  
Glacial Maximum ◽  
Ch4 Emissions ◽  
Last Glacial ◽  
Time Periods ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. The role of different sources and sinks of CH4 in changes in atmospheric methane ([CH4]) concentration during the last 100 000 yr is still not fully understood. In particular, the magnitude of the change in wetland CH4 emissions at the last glacial maximum (LGM) relative to the pre-industrial period (PI) as well as during abrupt climatic warmings or Dansgaard-Oeschger events of the last glacial period, is largely unconstrained. In the present study, we aim to understand the uncertainties related to the parameterization of the wetland CH4 emissions models relevant to these time periods by using two wetland models of different complexity (SDGVM and ORCHIDEE). These models have been forced by identical climate fields from low resolution coupled atmosphere-ocean general circulation model (FAMOUS) simulations of these time periods. Both emissions models simulate a large decrease in emissions during LGM in comparison to PI consistent with ice core observations and previous modeling studies. The global reduction is much larger in ORCHIDEE than in SDGVM (respectively −67 and −46%), and whilst the differences can be partially explained by different model sensitivities to temperature (i.e. Q10 values), the major reason for spatial differences between the models, is the inclusion of freezing of soil water in ORCHIDEE and the resultant impact on methanogenesis substrate availability in boreal regions. Besides, a sensitivity test performed with ORCHIDEE in which the methanogenesis substrate sensitivity to the precipitations is modified to be more realistic gives a LGM reduction of −36%. The range of the global LGM decrease is still prone to uncertainty and here, we underline its sensitivity to different process parameterizations. Over the course of an idealized D-O warming, the magnitude of the change in wetland CH4 emissions simulated by the two models at global scale is very similar at around 15 Tg yr−1, but this is only around 25% of the ice-core measured changes in [CH4]. The two models do show regional differences in emissions sensitivity to climate with much larger magnitudes of Northern and Southern tropical anomalies in ORCHIDEE. However, the simulated Northern and Southern tropical anomalies partially compensate each other in both models limiting the net flux change. Future work may need to consider the inclusion of more detailed wetland processes (e.g. linked to permafrost or tropical floodplains), other non-wetland CH4 sources or different patterns of D-O climate change in order to be able to reconcile emissions estimates with the ice-core data for rapid CH4 events.

Continental/Cordilleran ice interactions: a dominant cause of westward super-elevation of the last glacial maximum continental ice limit in southwestern Alberta, Canada

2001 ◽  
Vol 30 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Edward C. Little ◽  
Lionel E. Jackson ◽  
Thomas S. James ◽  
Stephen R. Hicock ◽  
Elizabeth R. Leboe
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

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.

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