Distinct moraine complexes are well-preserved at the headwaters of the Requ River valley on the southern slope of Bujia Gangri, the largest center of modern glaciation in the eastern Tanggula ...Mountains in western China. Dating these moraines is an important step in understanding glacial history, palaeoclimate, and landscape evolution in this region. Surface exposure dating using 10Be was done on twenty-three rock samples from large granitic boulders embedded in moraine crests were collected from the Yongqu River valley and the Daxiong River valley, two glaciated valleys at the headwaters of the Requ River valley. The moraines (MW1 and ME1) closest to the current glaciers in the west (main) and east (hanging) valleys of the Yongqu River valley were dated to 203 ± 51 a (n = 4) and 162 ± 58 a (n = 3); the inner four end moraines (MW3–1) and outer ones (MW3–2) of the third moraine complex (MW3) in the main valley date to 16.8 ± 1.8 ka (n = 3) and 20.7 ± 1.3 ka (n = 2); end moraines (ME2) near the mouth of the east valley and a high lateral moraine (MEL) on its east side date to 18.9 ± 3.0 ka (n = 4); and a high lateral moraine in the Daxiong valley (MDXL) dates to 18.6 ± 1.3 ka (n = 3). The dating results indicate that these moraines were formed during the Little Ice Age (LIA), the Heinrich 1 (H1) event period, and the global Last Glacial Maximum (LGMG). These glacial events are synchronous with those across the Tibetan Plateau (TP) and its surrounding mountains. Combining the palaeoclimatic and palaeoenvironmental proxies in the TP and its surroundings, we infer that the cooling during the LIA, H1, and LGMG was a main control for these glacial advances.
•A preliminary 10Be chronological framework since LGMG has been established in the eastern Tanggula Mountains.•Cooling during LIA, Heinrich 1 and LGMG glacial periods is the main determinant for palaeoglacier fluctuations.•A teleconnection between the North Atlantic cooling and palaeoglaciations since LGMG in the TP has been established.
Glacial landforms formed by multiple glaciations are well-preserved in the valleys around Karlik Mountain in the easternmost Tianshan range, Central Asia. These landforms are direct imprints of ...palaeoglaciers and represent important archives of past climatic and environmental conditions. Dating these landforms contributes to understanding the spatiotemporal variations of past glaciers and provides key information for reconstructing the palaeoclimate and palaeoenvironment in Central Asia. In this study, thirty-two boulder and bedrock samples were collected from two glaciated valleys on the southern slope of Karlik Mountain for terrestrial in situ cosmogenic nuclides (TCN) 10Be surface exposure dating. Based on the geomorphic relationships and dating results, the innermost MS1 moraine complex was deposited during the Little Ice Age (LIA); the MS2 moraine complex was formed during the Lateglacial; the MS3 moraine complex was deposited during the global Last Glacial Maximum (LGMG); the MS4 moraine complex, which is the largest moraine complex, is marine oxygen isotope stage (MIS) 4 in ages; and the MS5 moraine complex, which is only preserved at the interfluve ridges, has a similar age to MS4. The age of MS4 demonstrates that the largest local last glacial maximum (LGML) occurred during the early part of the last glacial cycle rather than during the LGMG. The MS4 and MS5 glacial complexes imply that a large ice cap with outlet valley glaciers developed on the whole of Karlik Mountain during MIS 4. These ages, combined with previous landform mapping and dating on the northern slope of the mountain, show that glacial advances since MIS 4 in this mountainous area were restricted to the valleys, rather than large ice cap scale, which is consistent with moraine records in the other valleys across the Tianshan range. The pattern and nearly synchronous timing of palaeoglacier fluctuations during the last glaciation in arid Central Asia imply that the main determinant for glacier fluctuations in this region has been changes in precipitation brought by the westerlies during periods of low temperature.
•Little Ice Age (LIA), Lateglacial, LGMG, mid-MIS3 and MIS 4 glacial events have been confirmed in Karlik Mountain.•A teleconnection between palaeoglaciations in eastern Tianshan range and the growth and decay of EISC has been established.•The changes in precipitation is the main determinant for palaeoglacier fluctuations in Tianshan range during cold periods.
The formation and evolution of permafrost in China during the last 20 ka were reconstructed on the basis of large amount of paleo-permafrost remains and paleo-periglacial evidence, as well as ...paleo-glacial landforms, paleo-flora and paleofauna records. The results indicate that, during the local Last Glacial Maximum (LLGM) or local Last Permafrost Maximum (LLPMax), the extent of permafrost of China reached 5.3×10
6
−5.4×10
6
km
2
, or thrice that of today, but permafrost shrank to only 0.80×10
6
−0.85×10
6
km
2
, or 50% that of present, during the local Holocene Megathermal Period (LHMP), or the local Last Permafrost Minimum (LLPMin). On the basis of the dating of periglacial remains and their distributive features, the extent of permafrost in China was delineated for the two periods of LLGM (LLPMax) and LHMP (LLPMin), and the evolution of permafrost in China was divided into seven periods as follows: (1) LLGM in Late Pleistocene (ca. 20000 to 13000−10800 a BP) with extensive evidence for the presence of intensive ice-wedge expansion for outlining its LLPMax extent; (2) A period of dramatically changing climate during the early Holocene (10800 to 8500−7000 a BP) when permafrost remained relatively stable but with a general trend of shrinking areal extent; (3) The LHMP in the Mid-Holocene (8500−7000 to 4000−3000 a BP) when permafrost degraded intensively and extensively, and shrank to the LLPMin; (4) Neoglaciation during the late Holocene (4000−3000 to 1000 a BP, when permafrost again expanded; (5) Medieval Warming Period (MWP) in the late Holocene (1000−500 a BP) when permafrost was in a relative decline; (6) Little Ice Age (LIA) in the late Holocene (500−100 a BP), when permafrost relatively expanded, and; (7) Recent warming (during the 20th century), when permafrost continuously degraded and still is degrading. The paleo-climate, geography and paleopermafrost extents and other features were reconstructed for each of these seven periods.
This paper presents new results of terrestrial cosmogenic nuclide dating of erratics in northern Poland. We report the first exposure ages of erratics located on the pre-Local Last Glacial Maximum ...and the Local Last Glacial Maximum moraines in Poland. Published radiocarbon ages are calibrated and used as a background indicator of the possible time window for the Local Last Glacial Maximum.
The terrestrial cosmogenic nuclide exposure ages presented in this study indicate that: (1) exposure ages of erratics located on the pre-Local Last Glacial Maximum moraines (15.9 ± 1.4 to 101.7 ± 8.5 ka) are not clustered around any specific time interval, (2) the age of the ice sheet retreat from the Local Last Glacial Maximum ice limit in western Poland is 20.7 ± 0.8 ka and the probable duration of the Local Last Glacial Maximum in western and central Poland is between ∼25 ka and ∼21 ka, (3) the age of the ice sheet retreat from the Local Last Glacial Maximum ice limit in eastern Poland is 17.3 ± 0.5 ka and the probable duration of the Local Last Glacial Maximum in eastern Poland is between ∼22 ka and ∼18 ka. Our results show that the Local Last Glacial Maximum ice limit in western and central Poland is probably ∼3 ka older than in eastern Poland.
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•A new set of 34 TCN exposure ages of erratics in northern Poland.•SIS retreat from the Leszno (Brandenburg) Phase at 20.7 ± 0.8 ka.•SIS retreat from the Poznań (Frankfurt) Phase at 17.3 ± 0.5 ka.•The Local LGM in western and central Poland (Leszno Phase) 25–21 ka.•The Local LGM in eastern Poland (Poznań Phase) 22–18 ka.
The Kawakawa/Oruanui tephra (KOT) is a key chronostratigraphic marker in terrestrial and marine deposits of the New Zealand (NZ) sector of the southwest Pacific. Erupted early during the Last Glacial ...Maximum (LGM), the wide distribution of the KOT enables inter-regional alignment of proxy records and facilitates comparison between NZ climatic variations and those from well-dated records elsewhere. We present 22 new radiocarbon ages for the KOT from sites and materials considered optimal for dating, and apply Bayesian statistical methods via OxCal4.1.7 that incorporate stratigraphic information to develop a new age probability model for KOT. The revised calibrated age, ±2 standard deviations, for the eruption of the KOT is 25,360 ± 160 cal yr BP. The age revision provides a basis for refining marine reservoir ages for the LGM in the southwest Pacific.
► Presents a new age of 25.4 cal ka for Kawakawa/Oruanui tephra. ► Applies Bayesian statistical modelling to quantify and reduce uncertainties. ► Refines age of critical datum for LGM climate comparisons in the Southwest Pacific.
We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S . This evidence includes feedback process ...understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density (PDF) for S given all the evidence, including tests of robustness to difficult‐to‐quantify uncertainties and different priors. The 66% range is 2.6‐3.9 K for our Baseline calculation, and remains within 2.3‐4.5 K under the robustness tests; corresponding 5‐95% ranges are 2.3‐4.7 K, bounded by 2.0‐5.7 K (although such high‐confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent, and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S , in particular using comprehensive models and process understanding to address limitations in the traditional forcing‐feedback paradigm for interpreting past changes.
The distribution of vegetation across glacial Sundaland and the underlying mechanisms have long been debated. We address this issue by comparing a compilation of vegetation reconstructions with ...climate simulations from the Community Earth System Model 2 (CESM2). A new n-alkane δ13C record derived from higher plants, covering the period from 21 to 5 cal ka BP in the southern South China Sea, is presented. This record, combined with previous pollen-based reconstructions, indicates that C3 forests dominated the outer-to-mid shelf regions of the northern Sundaland between the Last Glacial Maximum (LGM) and Heinrich Stadial 1, while open grasslands occupied the inner shelf region. A compilation of vegetation reconstructions shows a glacial contraction of lowland rainforests in longitudinal extent compared to the Holocene, especially in southern Sundaland. Furthermore, the previously proposed “savannah corridor” or “dry tropical forests” existed in the interior of Sundaland during the LGM, extending from the Malay Peninsula to the Lesser Sunda Islands. Modelling studies suggest that changes in the seasonality of precipitation, rather than mean annual rainfall, are more relevant to vegetation changes between the LGM and the Holocene. The glacial emergence of Sundaland caused an eastward shift of the ascending branch of the Walker Circulation and a substantial reduction in atmospheric convection activity over Southeast Asia, leading to a decrease in water availability during the dry season in both hemispheres. The enhanced water stress thus favors the expansion of open environments.
•Regional vegetation reconstructions are compared with hydroclimate simulations from the CESM2 model.•Glacial outer-middle continental shelf of northern Sundaland was covered by rainforests.•Savannah landscape or dry tropical forests occupied the glacial interior of Sundaland.•Enhanced dry-season water stress could account for glacial expansion of open environments.
The Last Glacial Maximum (LGM) is the period when global ice volume reached its maximum, the radioactive forcing well-defined and the climate in the quasi-equilibrium state. However, few proxy ...records have a temporal resolution high enough to capture detailed climate variabilities at this timescale. Here we reconstruct absolutely-dated and high-resolution δ18O and δ13C records from Shima Cave, central China, covering from 22.4 to 20.2 ka BP, with a temporal resolution of ∼14 years. Both δ18O and δ13C records show clear multicentennial-scale variations. Comparison with highly-resolved geological archives from the mid-to-low latitudes shows that multicentennial-scale changes are evident in the East Asian summer monsoon (EASM) and South American summer monsoon regions, but in antiphased relationship. Altogether six multicentennial-scale strong EASM periods are consistent with warmings in Greenland and northward movement of the jet stream over the Euro-Asia continent, and monsoon weakenings are linked with the ice-rafted debris peaks and Greenland cooling, indicating persistent influence of the North Atlantic climates on the EASM through shifts of the atmospheric circulations during the LGM.
•A high-resolution and well-dated East Asian summer monsoon history during the Last Glacial Maximum.•Multicentennial precipitation variability occurs in the low-latitude regions, with antiphased relationship in two hemispheres.•Multicentennial monsoon variabilities strongly coupled with North Atlantic climates through atmospheric circulations.
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