scholarly journals Distorted Pacific–North American teleconnection at the Last Glacial Maximum

2020 ◽  
Vol 16 (1) ◽  
pp. 199-209 ◽  
Author(s):  
Yongyun Hu ◽  
Yan Xia ◽  
Zhengyu Liu ◽  
Yuchen Wang ◽  
Zhengyao Lu ◽  
...  
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
North American ◽  
Tropical Pacific ◽  
Glacial Maximum ◽  
Jet Stream ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Tropical Pacific ◽  
The Last Glacial

Abstract. The Pacific–North American (PNA) teleconnection is one of the most important climate modes in the present climate condition, and it enables climate variations in the tropical Pacific to exert a significant influence on North America. Here, we show climate simulations in which the PNA teleconnection was largely distorted or broken at the Last Glacial Maximum (LGM). The distorted PNA is caused by a split in the westerly jet stream, which is ultimately forced by the large, thick Laurentide ice sheet that was present at the LGM. Changes in the jet stream greatly alter the extratropical waveguide, distorting wave propagation from the North Pacific to North America. The distorted PNA suggests that climate variability in the tropical Pacific, notably El Niño–Southern Oscillation (ENSO), would have little direct impact on North American climate at the LGM.

scholarly journals Distorted Pacific-North American Teleconnection at the Last Glacial Maximum

2019 ◽  
Author(s):  
Yongyun Hu ◽  
Yan Xia ◽  
Zhengyu Liu ◽  
Yuchen Wang ◽  
Zhengyao Lu ◽  
...  
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
North American ◽  
Tropical Pacific ◽  
Glacial Maximum ◽  
Jet Stream ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Tropical Pacific ◽  
The Last Glacial

Abstract. The Pacific-North American (PNA) teleconnection is one of the most important climate modes in the present climate condition, and it enables climate variations in the tropical Pacific to exert significant impacts on North America. Here, we show climate simulations that the PNA teleconnection was largely distorted or broken at the Last Glacial Maximum (LGM). The distorted PNA is caused by a split of the westerly jet stream, which is ultimately forced by the thick and large Laurentide ice sheet at the LGM. Changes in the jet stream greatly alter the extratropical wave guide, distorting wave propagation from the North Pacific to North America. The distorted PNA suggests that climate variability in the tropical Pacific, notably, El Niño and Southern Oscillation (ENSO), would have little direct impact on North American climate at the LGM.

scholarly journals Northern Westerlies during the Last Glacial Maximum: Results from CMIP5 Simulations

2018 ◽  
Vol 31 (3) ◽  
pp. 1135-1153 ◽  
Author(s):  
Na Wang ◽  
Dabang Jiang ◽  
Xianmei Lang
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
Lower Troposphere ◽  
Glacial Maximum ◽  
Jet Stream ◽  
Last Glacial ◽  
The North ◽  
Poleward Shift ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract Based upon simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), the vertical and regional characteristics of the northern westerlies during the Last Glacial Maximum (LGM) are investigated in this study. At the Northern Hemispheric scale, all nine available models simulate a poleward shift of the 200-hPa jet, and eight models simulate an equatorward shift of the 850-hPa jet compared to the preindustrial period; these shifts are of approximately 2°–3° latitude for the arithmetic multimodel mean. The upper-tropospheric cooling in the tropics, possibly due to reduced latent heat release, is expected to account for the poleward shift of the 200-hPa jet through the thermal wind relationship. Changes in the midlatitude baroclinic instability in response to the amplified polar cooling are associated with the jet stream in the lower troposphere through anomalous eddy activity. In particular, the types of predominant baroclinic eddies are regionally dependent. The behavior of the 850-hPa jet over the North Pacific is steered by transient eddies and characterized by a southward displacement during the LGM. By contrast, the remarkable enhancement of the North Atlantic jet stream throughout the troposphere is associated with the notably increased stationary eddy momentum convergence, presumably due to the presence of the Laurentide ice sheet over North America. In comparison with the proxy records, although there is no observational evidence explicitly indicating changes of the upper-level northern westerlies, the simulated LGM 850-hPa westerly wind field is indirectly concordant with the reconstructed moisture conditions over the Mediterranean region and southwestern North America.

scholarly journals The Effects of the Laurentide Ice Sheet on North American Climate during the Last Glacial Maximum

2008 ◽  
Vol 41 (2) ◽  
pp. 291-299 ◽  
Author(s):  
A. J. Broccoli ◽  
S. Manabe
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
North American ◽  
Ice Sheet ◽  
Glacial Maximum ◽  
Laurentide Ice Sheet ◽  
Last Glacial ◽  
North American Climate ◽  
The Last Glacial Maximum ◽  
The Last Glacial

ABSTRACT A climate model, consisting of an atmospheric general circulation model coupled with a simple model of the oceanic mixed layer, is used to investigate the effects of the continental ice distribution of the last glacial maximum (LGM) on North American climate. This model has previously been used to simulate the LGM climate, producing temperature changes reasonably in agreement with paleoclimatic data. The LGM distribution of continental ice according to the maximum reconstruction of HUGHES et al. (1981) is used as input to the model. In response to the incorporation of the expanded continental ice of the LGM, the model produces major changes in the climate of North America. The ice sheet exerts an orographic effect on the tropospheric flow, resulting in a splitting of the midlatitude westerlies in all seasons but summer. Winter temperatures are greatly reduced over a wide region south of the Laurentide ice sheet, although summer cooling is less extensive. An area of reduced soil moisture develops in the interior of North America just south of the ice margin. At the same time, precipitation increases in a belt extending from the extreme southeastern portion of the ice sheet eastward into the North Atlantic. Some of these findings are similar to paleoclimatic inferences based on geological evidence.

Evidence of humans in North America during the Last Glacial Maximum

Science ◽  
2021 ◽  
Vol 373 (6562) ◽  
pp. 1528-1531 ◽  
Author(s):  
Matthew R. Bennett ◽  
David Bustos ◽  
Jeffrey S. Pigati ◽  
Kathleen B. Springer ◽  
Thomas M. Urban ◽  
...  
Keyword(s):  
North America ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial
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