树轮记录的自公元 １２００年以来强火山喷发事件与 高亚洲南部河流源区气候水文变化的关联

Abstract

强火山喷发作为气候变化重要的外强迫因素，其所造成的气候环境效应一直是气候变化研究热点，而其对于流域水循环影响较少受关注。本文利用采自高亚洲南部河流源区麦吊云杉（Picea brachytyla）树轮样本，研制出一个长达885 a的树木年轮标准宽度年表。基于树轮气候响应分析结果，利用线性回归模型重建研究区自公元1200年上年11月至当年2月平均最低气温变化，重建方程方差解释量47.1%。该气温重建序列显示，研究区自公元1200年经历了8个冷期和9个暖期，包含有10个极冷年和23个极暖年。同时，该气温重建序列验证了自公元1200年来27次强火山喷发（VEI≥5）对于青藏高原东南部河流源区气候的影响，包括1257年Samalas和1815年Tambora等强火山喷发事件。该气温重建序列与相关河流径流数据对比结果表明强火山喷发在引起高亚洲南部河流源区气温出现明显下降的同时，也可能会进一步导致水循环减缓，使得高亚洲南部河流径流量出现减少。

Long-term climate proxy data is very important for understanding past climate changes and assess the influences of large volcanic eruptions. A total of 81 cores were taken from Picea brachytyla trees in the Zhujiaola Mountain(31°3'N, 96°58'E; 4277 m a.s.l.), Changdu city, southeastern Tibetan Plateau in June, 2020. All cores were air-dried prior to mounting and sanding, and prepared following standard dendrochronological techniques. And the CooRecorder 9.4 ring analyzer with accuracy of 0.01 mm was used to measure the tree-ring width of all cores. The quality of cross-dating was checked by using the COFECHA program. Finally, the standard chronology during 1135~2019 A.D. was developed by ARSTAN program for subsequent analysis. Climate-growth relationship analysis between tree ring width chronology and climate data showed that mean minimum temperature from November of previous year to current year February was the main factor controlling tree-ring growth in the Zhujiaola Mountain, southeastern Tibetan plateau, and the total precipitation from August of previous year to current year May states on the growth effect are significant. Mean minimum temperature from previous November to February since 1200 A.D. were then reconstructed based on the tree-ring width chronology using a simple liner regression model. The reconstruction explained 47.1% of the variance in the instrumental temperature records during the calibration period(1954~2019 A.D.). The reconstruction exhibits decadal to inter-decadal temperature variability, with cold periods occurring in 1206~1227, 1234~1332, 1356~1372, 1465~1548, 1588~1602, 1728~1832, 1899~1935 and 1947~1987, and warm periods in 1333~1355, 1373~1388, 1397~1464, 1549~1587, 1603~1634, 1643~1727, 1833~1898, 1936~1946 and 1988~2019. Meanwhile, the reconstruction contains ten extreme cold years(1474, 1504, 1534, 1757, 1789, 1793, 1817, 1968, 1972 and 1982) and twenty three extremely warm years(1407, 1410, 1412, 1422, 1423, 1424, 1448, 1673, 1674, 1682, 1683, 1694, 1698, 1700, 1701, 1702, 1706, 1708, 2000, 2013, 2015, 2016 and 2017). The temperature fluctuations of the reconstructed sequence were in accordance with other temperature reconstruction in the southeastern Tibetan plateau. All of above mentioned information demonstrated the reliability of reconstructed temperature. At the same time, the temperature reconstruction sequence verified the cooling effect after 27 large volcanic eruptions since 1200 A.D., including the large volcanic eruptions of Samalas in 1257 and Tambora in 1815. In addition, the comparison between the temperature reconstruction sequence and the related river runoff data shows that the strong volcanic eruption may cause significant decrease in the temperature of the river source area in Southern High Asia, and may further slowed down the water cycle, resulting in the decrease of river runoff in Southern High Asia.