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Dynamic fluctuations in sea surface temperature within the North Atlantic Ocean (NA-SST) exert a pivotal influence on global climate change. Yet, the specific impacts of these variations on the temperature shifts within the Qinling-Bashan Mountains (QBM) of China, remain to be fully elucidated. Furthermore, a debate surrounding the manifestation of the Little Ice Age (LIA) within the QBM is ongoing, primarily due to the scarcity of reliable, long-term, and high-resolution temperature records. To bridge these knowledge gaps, in this paper, we present a ∼ 250-year temperature reconstruction (Tmax 11 – 7) developed based on a tree-ring-width chronology from the QBM. The new reconstruction not only aligns with a local winter temperature reconstruction based on historical document evidence, but also reveals robust regional and hemispheric temperature signals. Intriguingly, the study shows that the warming trend observed in the QBM since the Industrial Era is less pronounced than that witnessed across China and the Northern Hemisphere. The Tmax 11 – 7 reconstruction provides a glimpse into the final stages of the LIA, highlighting a relatively colder 19 th century followed by a warmer 20 th century. Notably, the warming trend post-1970s remains within the bounds of the 250-year temperature framework. The research further uncovers that NA-SST has predominantly governed the QBM's temperature fluctuations over the past centuries, as evidenced by the tight positive correlation between Atlantic multidecadal Oscillation (AMO)/Atlantic multidecadal variability (AMV) and Tmax 11 – 7. However, this dominant influence of NA-SST was temporarily subdued between 1900 and 1930 CE due to the interference of Pacific Decadal Oscillation (PDO). This finding serves as a reminder that future temperature projections for the QBM must account not only for the primary role of NA-SST but also the modulating effects of the PDO. The study is essential for shaping effective environmental management and adaptation strategies in the region. • A ∼ 250-year temperature reconstruction is developed using tree rings from the QBM. • The QBM saw the last stage of the LIA and recent warming is within historical frame. • North Atlantic SST (NA-SST) played a positive and dominant role on QBM'S temperature changes. • Weakened NA-SST's impact on temperature in 1900–1930 CE was due to PDO's interference. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of the Little Ice Age (LIA) on the Tibetan Plateau (TP) is of critical importance for understanding the climate changes over the past millennium. However, the data associated with the extents and chronologies of TP LIA moraines are highly dispersed in literature. Lack of systematic integration of these data hampers us to further understand the nature of the LIA, especially from a perspective of whole TP. The paper reviews multiple types of dating on LIA moraines to examine the timing and nature of the LIA on the TP. These include ages of radiocarbon 14C, lichenometry, and cosmogenic radionuclide (CRN), by which we can cross-date the same or morphostratigraphically similar landforms. LIA moraines on the TP are usually present a few hundred to thousand meters beyond the contemporary glaciers. The morphological and stratigraphic evidence indicates multiple periods of glacier advance during the last millennium (LIA). At present, available chronology evidence allows to fully compare the timing of the LIA maximum extents. The glaciers reached and retreated from their LIA maximum extents by an asynchronous pattern between different parts of the TP. The majority of glaciers advanced to their LIA maximum extents at late-14th and early-14th century on the southern and northwestern TP, respectively. The glaciers retreated from their LIA maximum extents during 16th to early-18th, late-14th to early-15th and early-16th century on the southern, northwestern, and northeastern TP, respectively. In addition, the glacier advance period of late-18th to early-19th centuries and retreat period of late-19th century are common on the whole TP. Comparison with ice core records suggests that on the TP, the glacier fluctuations responded more strongly to temperature than to precipitation. By comparison of the LIA chronologies from a global perspective, this paper also concludes that the LIA maximum extents occurred commonly earlier on the TP than in North Atlantic and Southern Hemisphere regions, despite of the variability in the timing of LIA maximum extents on the TP and in the North Atlantic regions. Further, more chronology programs, especially in the central TP, are necessarily needed to improve our understanding of the LIA glacier fluctuations. [Copyright &y& Elsevier]

Reconstructing three-dimensional palaeoglacier surface, thickness, and volume provides useful information for quantifying palaeo-climate conditions during glacial stages and assessing the impact of glacier change on water resources. A glacial flowline model has been implemented in Excel and ArcGIS to reconstruct palaeoglaciers based on digital elevation models and geomorphic constraints, such as moraines and trimlines that represent the margins and local heights of palaeoglaciers, respectively. However, significant efforts are still needed in using these tools for palaeoglacier reconstruction, such as digitizing flowlines, adjusting shear stress, and deriving shape factors. This paper presents an automated method, PalaeoIce, to reconstruct palaeoglaciers using geomorphic constraints. Coded in python, PalaeoIce is an ArcGIS toolbox with a set of tools to generate glacial flowlines, optimize shear stress, derive shape factors, calculate ice thickness values along flowlines, and interpolate palaeo ice surfaces based on geomorphic constraints. The use of PalaeoIce is demonstrated using extant glaciers with measured thickness values and moraines/trimlines of the Little Ice Age (LIA) and Marine Isotope Stage (MIS) 2 in the eastern Tian Shan, China. The reconstructed ice thickness values of Glacier No. 1 in this area show a reasonable agreement with field measurements with 1.4 % and 5.4 % differences between measured and reconstructed mean ice thickness values using the two methods included in PalaeoIce: a revised ice thickness model for extant glaciers and a palaeoglacier reconstruction method based on glacier outlines, respectively. Two approaches are then illustrated for palaeoglacier reconstructions using two sets of geomorphic constraints: one with the fully reconstructed glacier outlines during the LIA, and the other with just the terminal moraine and limited trimlines during MIS 2. PalaeoIce can significantly improve the efficiency of palaeoglacier reconstructions and the understanding of the impact of glacier change on water resources. • An automated method, PalaeoIce, is presented for palaeoglacier reconstruction. • Tools are developed to create flowlines, modify DEM, and reconstruct palaeoglaciers. • Reconstructed ice thickness data are validated by field measurements in Tian Shan. • Target geomorphic features are of importance for palaeoglacier reconstruction. [ABSTRACT FROM AUTHOR]