Climatic signals in the Chinese loess record for the Last Glacial: The influence of northern high latitudes and the tropical Pacific

2006 ◽  
Vol 154-155 ◽  
pp. 128-135 ◽  
Author(s):  
Guangjian Wu ◽  
Baotian Pan ◽  
Hongshan Gao ◽  
Qingyu Guan ◽  
Dunshen Xia
Keyword(s):  
Tropical Pacific ◽  
High Latitudes ◽  
Chinese Loess ◽  
Last Glacial ◽  
Climatic Signals ◽  
The Tropical Pacific ◽  
The Last Glacial

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 Timing and structure of the Younger Dryas event and its underlying climate dynamics

2020 ◽  
Vol 117 (38) ◽  
pp. 23408-23417
Author(s):  
Hai Cheng ◽  
Haiwei Zhang ◽  
Christoph Spötl ◽  
Jonathan Baker ◽  
Ashish Sinha ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
North Atlantic ◽  
Time Scale ◽  
Asian Monsoon ◽  
Younger Dryas ◽  
Tropical Pacific ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial

The Younger Dryas (YD), arguably the most widely studied millennial-scale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon-Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard–Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ∼11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ∼11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic–Asian Monsoon-Westerlies directionality of climatic recovery.

Thermodynamic Scaling of the Hydrological Cycle of the Last Glacial Maximum

2012 ◽  
Vol 25 (3) ◽  
pp. 992-1006 ◽  
Author(s):  
William R. Boos
Keyword(s):  
Water Vapor ◽  
Last Glacial Maximum ◽  
Climate Models ◽  
Hydrological Cycle ◽  
High Latitudes ◽  
Last Glacial ◽  
The Tropics ◽  
The Last Glacial Maximum ◽  
Circulation Changes ◽  
The Last Glacial

Abstract In climate models subject to greenhouse gas–induced warming, vertically integrated water vapor increases at nearly the same rate as its saturation value. Previous studies showed that this increase dominates circulation changes in climate models, so that precipitation minus evaporation (P − E) decreases in the subtropics and increases in the tropics and high latitudes at a rate consistent with a Clausius–Clapeyron scaling. This study examines whether the same thermodynamic scaling describes differences in the hydrological cycle between modern times and the last glacial maximum (LGM), as simulated by a suite of coupled ocean–atmosphere models. In these models, changes in water vapor between modern and LGM climates do scale with temperature according to Clausius–Clapeyron, but this thermodynamic scaling provides a poorer description of the changes in P − E. While the scaling is qualitatively consistent with simulations in the zonal mean, predicting higher P − E in the subtropics and lower P − E in the tropics and high latitudes, it fails to account for high-amplitude zonal asymmetries. Large horizontal gradients of temperature change, which are often neglected when applying the scaling to next-century warming, are shown to be important in large parts of the extratropics. However, even with this correction the thermodynamic scaling provides a poor quantitative fit to the simulations. This suggests that circulation changes play a dominant role in regional hydrological change between modern and LGM climates. Changes in transient eddy moisture transports are shown to be particularly important, even in the deep tropics. Implications for the selection and interpretation of climate proxies are discussed.

Early Holocene presences of Norway spruce (Picea abies L. Karst.) at high latitudes in Norway and Sweden: the genetic story of up to 9550 year old spruce clones in the Scandinavian mountains

2020 ◽  
Author(s):  
Kevin Nota ◽  
Laura Parducci
Keyword(s):  
Picea Abies ◽  
Norway Spruce ◽  
Last Glacial Maximum ◽  
Genetic Research ◽  
Melting Curve ◽  
Glacial Maximum ◽  
High Latitudes ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p><span>The survival of boreal trees in ice-free cryptic refugia’s at high latitudes during the Last Glacial Maximum has been subjected to a long-standing debate. Norway spruce (</span><span><em>Picea abies</em></span><span> L. Karst) is generally believed to have recolonised Scandinavia from the east. Spruce appears for the first time in the pollen assemblages in central Sweden around 3000 years before present (yr BP), however, a growing body of macrofossil and genetic evidence suggested that spruce might have survived in ice-free areas around the Norwegian shore or closer to the Weichselian ice sheet than previously thought. These satellite populations may have contributed to the recolonisation of Scandinavia from the west and may be ancestors to the ancient (up to 9550-year-old) but still living clonal spruce trees occurring today in the Scandinavian mountains (e. g. Old Tjikko and Old Rasmus). Genetic research has shown that modern </span><span><em>P. abies </em></span><span>contain two sequence variants for the maternal inherited mitochondrial mh05 fragment across its Eurasian distribution, of which one is unique to Scandinavia. The Scandinavian variant shows the highest frequency in western Scandinavia and its modern distribution suggests that it was already present before the last glacial period. The Scandinavian variant was also detected in lake sediment dating back to 10300 yr BP at Trøndelag in Central Norway (63°N).</span></p><p><span> We are using sensitive melting curve qPCR assay and high-throughput sequencing to detect the presence of the Scandinavian variant in several sediment cores covering Scandinavia and north-east & southern Russia. So far, the qPCR melting curve assay detected the Scandinavian variant in peat sediment from northern Finland (~52,000 – 42,000 yr BP), in lake sediments in central Sweden and central Norway (~10,000 – 900 yr BP) and in southern Sweden (~12000 – 11000 yr BP), which is far earlier than currently believed. Additional lakes are being processed and samples positive for the Scandinavian variant will be sequenced to confirm sequence identity. We are also conducting population genetic analysis of the ancient clonal spruce stands to see how these trees are related to the modern spruce forest and weather they have contributed to the recolonization of Scandinavia. The results of this study will increase our understanding of the post glacial colonisation of </span><span><em>P. abies</em></span><span> in Scandinavia after the Last Glacial Maximum.</span></p>

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