Khan Adam, Chen Feng, Saleem Sidra, Chen Youping, Zhang Heli, Bakhtiyorov Zulfiyor
Department of Botany, University of Lakki Marwat KP, Pakistan.
Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Institute of International Rivers and Eco-Security, Yunnan University, Kunming, China; Southwest United Graduate School, Kunming 650500, China; Key Laboratory of Tree-ring Physical and Chemical Research of the Chinese Meteorological Administration / Xinjiang Laboratory of Tree-ring Ecology, Institute of Desert Meteorology, Chinese Meteorological Administration, Urumqi 830002, China.
Sci Total Environ. 2024 Dec 15;956:177393. doi: 10.1016/j.scitotenv.2024.177393. Epub 2024 Nov 9.
Understanding long-term temperature variability in the Upper Indus Basin (UIB), northern Pakistan, and its driving mechanisms is challenging due to the scarcity of long observational records and available literature. In this study, we reconstructed a 651-year (1370-2020 CE) warm-season (March-September) temperature record using the tree-ring maximum latewood density (MXD) of blue pine (Pinus wallichiana). The reconstruction explains 57 % of the variance in actual temperature during the common calibration period (1972-2020 CE). Our analysis identified ten high-temperature periods (temperature > 20.9 °C) and nineteen low-temperature periods (temperature < 19.8 °C), with the coldest years being 1392, 1707, 1817, and 1837, and the warmest years being 2013, 2016, 2017, and 2018. Spatial correlation analysis reveals a significant positive correlation with field temperature, predominantly in neighboring regions, and a significant negative correlation with relative humidity and precipitation. Multi-taper spectral analysis shows inter-annual (1.9, 2.5, 2.7, 5.5 years) and interdecadal (11, 18, 23, 25, 40, 71 years) cycles, suggesting a potential linkage with the Atlantic Multidecadal Oscillation (AMO). The negative linkage between our reconstruction and the region's standardized Palmer Drought Severity Index (scPDSI) indicates that continued temperature increase could result in severe drought in northern Pakistan in the near future. During the 20th century, the UIB experienced two distinct warming phases: 1948-1970 CE and 1994-2020 CE. The warming rate during 1994-2020 CE was 0.5 °C higher, indicating unprecedented recent warming. The reconstructed temperature record also demonstrates a large-scale spatiotemporal signal and a strong connection with most recorded volcanic eruptions. These findings enhance our understanding of long-term temperature variability in the region, highlighting the significance of MXD in reconstructing past temperature patterns.
由于长期观测记录和现有文献稀缺，了解巴基斯坦北部印度河上游流域（UIB）的长期温度变化及其驱动机制具有挑战性。在本研究中，我们利用蓝松（Pinus wallichiana）的树轮最大晚材密度（MXD）重建了一个651年（公元1370 - 2020年）的暖季（3月至9月）温度记录。该重建解释了共同校准期（公元1972 - 2020年）实际温度变化的57%。我们的分析确定了10个高温期（温度>20.9°C）和19个低温期（温度<19.8°C），最冷年份为1392年、1707年、1817年和1837年，最暖年份为2013年、2016年、2017年和2018年。空间相关性分析显示与实地温度存在显著正相关，主要在邻近地区，与相对湿度和降水量存在显著负相关。多窗谱分析显示存在年际（1.9、2.5、2.7、5.5年）和年代际（11、18、23、25、40、71年）周期，表明可能与大西洋多年代际振荡（AMO）有关。我们的重建与该地区标准化帕尔默干旱严重指数（scPDSI）之间的负相关表明，持续升温可能在不久的将来导致巴基斯坦北部出现严重干旱。在20世纪，UIB经历了两个不同的变暖阶段：公元1948 - 1970年和公元1994 - 2020年。公元1994 - 2020年期间的变暖速率高出0.5°C，表明近期出现了前所未有的变暖。重建的温度记录还显示出大规模的时空信号以及与大多数记录的火山喷发的紧密联系。这些发现增进了我们对该地区长期温度变化的理解，突出了MXD在重建过去温度模式中的重要性。
