NOAA/WDS Paleoclimatology - Northwest Himalaya 576 Year Standardized Precipitation Index Reconstruction

Hydroclimatic variability driven by global warming in the climatically vulnerable cold semi-arid to arid northwest (NW) Himalaya is poorly constrained due to paucity of continuous weather records and annually resolved proxies. Applying a network of annually resolved tree-ring-width chronologies from semi-arid region of Kishtwar, Jammu and Kashmir, India, we reconstructed April-May standardized precipitation index extending back to A.D. 1439 (576 years). The reconstructed series is featured by the most conspicuous long-term droughts during the 15th to early 17th centuries followed by a general wetting, with 1984-2014 being the wettest interval in the past 576 years. The data, consistent with other independently developed tree-ring-based hydrological records from cold semi-arid to arid NW Himalaya and Karakoram, point to an increased regional wetting in the recent decades. Such an increased wetting might have led to the anomalous behaviour of glaciers in the NW Himalaya and Karakoram in contrast to the general receding trends in the central and eastern Himalaya.

受全球变暖影响的气候脆弱区——寒冷半干旱至干旱的喜马拉雅西北部（NW Himalaya），其水文气候变异性因连续气象记录匮乏、年分辨率代用指标稀缺，相关研究仍难以得到有效约束。本研究依托印度查谟和克什米尔斯奇特瓦尔半干旱区域的一套年分辨率树轮宽度年表网络，重建了可追溯至公元1439年（即576年历史）的4-5月标准化降水指数序列。该重建序列的显著特征为：15世纪至17世纪初经历了最为显著的长期干旱事件，随后整体进入湿润阶段，其中1984-2014年是过去576年中最为湿润的时段。本数据集与喜马拉雅西北部及喀喇昆仑地区寒冷半干旱—干旱区其他独立构建的树轮水文记录结果一致，均表明近几十年来该区域湿润程度显著增强。与喜马拉雅中东部冰川普遍退缩的趋势不同，这种湿润程度的增强可能是导致喜马拉雅西北部及喀喇昆仑地区冰川出现异常行为的重要原因。