Journal of Quaternary Science最新文献

Grain size is a proxy for climate and environmental change, and the results of grain size analyses can be used to infer the conditions and environment under which the sediments were formed. The eastern foothills of the Tai-hang Mountains in northern China are on the edge of the East Asian Summer Monsoon and are extremely sensitive to climate and environmental changes. Understanding the ecological changes in this region is vital for coping with future climate change and solving related climate and environmental problems. This study uses parametric grain size end-member analysis to discuss the depositional dynamics and ecological changes in the Middle Pleistocene of the Shijiazhuang JingXing YF profile. The results indicate that: (1) The OSL dates of the YF profile vary from 274 to 0.997 ka, and sedimentation began in the Middle Pleistocene. (2) The YF profile's sediments’ grain size is separated into four end elements: EM1 is the clay fraction produced by loam-forming action; EM2 and EM3 are long-distance transported fine silt and short-distance transported silt at low altitudes, representing the variation in East Asian Summer Monsoon intensity; EM4 represents the near-surface transported coarse silt fraction driven by East Asian Winter Monsoon power. (3) The grain size index reconstructed the paleoclimate of the Middle Pleistocene in the Shijiazhuang area, and it can be divided into four stages: 274–210 ka, the climate changed from cold to warm; 210–170 ka, was a warm period; 170–80 ka, the climate changed from warm to cold; and from 80–1 ka was a cold period. Multi-indicator comparisons show that the monsoon evolution recorded in the Middle Pleistocene YF loess-paleosol sequence is fundamentally consistent with changes in mid- to high-latitude solar radiation, and changes in solar radiation modulate that monsoon changes in East Asia.

Maritime glaciers on the southeastern Tibetan Plateau (SETP) are experiencing rapid mass loss, yet both current rates and future projections lack centennial-scale context. Here, we mapped the outlines of 2454 glaciers at their Little Ice Age (LIA) maximum (~1300–1700 CE) on the SETP and reconstructed their thickness. The results show that there has been a 21.5% reduction in area and a loss of 152.9 km³ of ice (130 Gt) since the LIA at a rate of 0.19–0.43 Gt year⁻¹. We estimated the long-term average mass balance of glaciers to be between −0.028 and −0.065 m water equivalent (w.e.) year⁻¹. The rate of change between 2000 and 2019 CE was 10 to 23 times higher than LIA maximum to 2000 CE, far exceeding any centennial-scale rates of change recorded elsewhere in the world. Locally, lake-terminating glaciers lost mass faster than land-terminating glaciers. Spatial trends in the rate of glacier mass loss and the extent of equilibrium-line altitude (ELA) changes on the SETP are influenced by glacier size, as well as the topography and climate of the study area. Glaciers in the lowland of river valleys such as the Yarlung Zangbo-Brahmaputra show slower mass loss and larger ELA changes. The significant spatial heterogeneity of glacier change suggests that glacier evolution is influenced by both regional and local factors.

The arid Central Asia has long demonstrated a correlation between human activity and climatic fluctuations, particularly during the Holocene. However, Late Holocene palaeoclimate records remain sparse, limiting our understanding of the dynamic relationship between climate variability and human civilization over the past millennium. This study based on peat sediment samples from the Zhaosu Basin on the northern slopes of the Western Tian Shan Mountains, China, reconstructs vegetation and climate changes over the past millennium by employing precise dating techniques and high-resolution pollen analysis. The results were as follows: (1) grasslands have consistently dominated the northern slopes of the Western Tian Shan over the last millennium, as evidenced by the prevalence of pollen types, such as Artemisia, Chenopodiaceae, and Poaceae. During the Medieval Climate Anomaly (MCA, 1046–1288 ad), frequently fluctuating Artemisia/Chenopodiaceae (A/C) ratios indicated a transition from warm–arid to warm–humid conditions. This trend shifted during the Little Ice Age (LIA, 1288–1476 ad), marked by increased Picea pollen and positive principal component analysis axis 2 scores, suggesting a cooler and wetter environment. Pollen concentrations of arborvitae and shrubs peaked during the LIA (1476–1606 ad), alongside high Picea content, signaling an intensified cold and wet climate. (2) Historical records correlate climate conditions with patterns of human habitation and development. The warm, humid climate during the MCA (1046–1288 ad) coincided with the Song Dynasty, fostering population growth and cultural development on both slopes of the Tian Shan region. Conversely, during the LIA (1288–1606 ad), cooling temperatures and frequent conflicts triggered significant migrations, particularly to the northern slopes, (i.e., during the Yuan-Ming period) where conditions were more favorable. The center of gravity of the population relocated to the northern slopes of the Tian Shan Mountains. This shift promoted agricultural advancements in later periods, despite the challenges posed by the harsher climate.

We analyzed a 2.38 m sediment core from Clear Pond, South Carolina, to reconstruct fire and effective moisture over the past 7500 years in a Pinus-Quercus forest. Our record of macroscopic charcoal, reconstructed precipitation isotopes from δ²H_n-alkane analysis, and other geochemical indicators provides a high-resolution record of the interplays between fire and effective moisture on the Atlantic Coastal Plain (ACP). Our work complements and updates an existing pollen and microscopic charcoal record from Clear Pond with additional analyses, including reconstructed effective moisture. δ²H_n-alkane values are indicative of soil moisture isotopic values, which are controlled by precipitation δ²H values and fractionation during evaporation and transpiration. Our results show that from ca. 7500–3670 cal yr bp, effective moisture was higher than modern conditions at Clear Pond, but fires were frequent. Our δ²H_n-alkane record of effective moisture indicates that conditions remained mesic from ca. 3670 cal yr bp until 2350 cal yr bp, but macroscopic charcoal data indicate that fires were much less frequent than before. This pattern is in opposition to several nearby records on the ACP, where much of this timespan was apparently somewhat dry with frequent fires. After ca. 2350 cal yr bp, effective moisture slightly increased, and frequent fires returned to the landscape. These conditions persisted until about ca. 860 cal yr bp, when δ²H-derived effective moisture values reached their most positive values, indicating xeric conditions, and charcoal data indicate a declining importance of fire on the landscape. Over the past 7500 years at Clear Pond, there is an apparent decoupling of reconstructed paleomoisture indicators and macroscopic charcoal records, which indicates that fire is not largely controlled by climate on the ACP and that landscape burning by Native Americans may be an important control on Holocene fire regimes at Clear Pond, especially from ca. 7500–2350 cal yr bp.