青藏高原东南部海子山末次冰盛期到末次冰消期冰川事件及其气候驱动机制研究【封面文章】

Glacial events and climatic drivers from the Last Glacial Maximum to the Last Glacial Termination in the Haizishan area, southeastern Qinghai-Xizang Plateau【Cover】

关键词:  ¹⁰Be暴露测年  末次冰盛期  冰川事件  海子山  青藏高原东南部

Key words:  ¹⁰Be surface exposure dating  Last Glacial Maximum  glacial event  Haizishan area  the southeastern Qinghai-Xizang Plateau

摘要:

青藏高原东南部横断山腹地的海子山保存有丰富的第四纪冰川遗迹，为青藏高原古气候研究提供了良好的素材。然而，受限于高精度定年数据的缺乏，导致对该区第四纪，特别是末次冰盛期（Last Glacial Maximum，LGM）到末次冰消期（Last Glacial Termination，T1）的冰川演化的时空特征及规律仍不完全清楚，制约了对横断山脉乃至青藏高原该时期冰川演化气候驱动机制的深入理解。选取海子山南缘央英措冰川槽谷为研究区，重点对分布于该槽谷的三道冰碛垄中两道相对年轻的冰碛垄（M1和M2）开展野外地质地貌调查和¹⁰Be暴露测年研究，共获得15个暴露年龄，介于(16.5±1.4)— (73.9±4.8) ka。经统计分析剔除异常值后，冰碛垄M1和M2的平均沉积时代分别为(17.3±0.6) ka和(21.0±0.6) ka，对应T1和LGM。结合区域内已发表的LGM以来的¹⁰Be暴露年龄，厘定海子山自LGM到T1期间至少经历了四次主要冰川事件，分别对应LGM、LGM结束前后、Heinrich事件1和Bølling-Allerød暖期，反映出该区冰川从LGM到T1的阶段性退缩及最终消亡的演化过程。与气候记录综合对比发现，这四次冰川事件主要受控于区域夏季气温变化，而该温度变化与印度洋-西太平洋暖池海表温度的变化密切相关。

Abstract:

Background, aim, and scope The Haizishan (HZS) area, located in the hinterland of the Hengduan Mountains on the southeastern Qinghai-Xizang Plateau (QXP), preserves abundant well-preserved glacial landforms from Quaternary glaciations, offering valuable records of past climate. However, the lack of high-precision chronological constraints has hindered a comprehensive understanding of glacial dynamics from the Last Glacial Maximum (LGM) to the Last Glacial Termination (T1). This study aims to reconstruct the spatiotemporal pattern of glacier fluctuations in HZS and to clarify the dominant climatic factors responsible for these changes from the LGM to T1. Materials and methods We applied ¹⁰Be surface exposure dating to two moraines located in the Yangying Co Valley, at the southern margin of the HZS. Results The moraines yielded exposure ages of (21.0±0.6) ka and (17.3±0.6) ka (mean age). Discussion These results indicate two distinct phases of glacial events, corresponding to the LGM and T1, respectively. Combined with recalculated regional ¹⁰Be ages, four glacial events were identified in HZS during this period, occurring around (21.0±1.4)  ka (LGM; onset of glacier retreat), (19.0±0.4)  ka (the end of LGM; standstill or readvance), (16.9±0.9)  ka (Heinrich Stadial 1; standstill or readvance), and (14.7±0.7)  ka (Bølling-Allerød Interstadial; rapid deglaciation). These four glacier events reveal an evolutionary process of stepwise glacial retreat and final deglaciation. Comparison with multiple climate proxies indicates that regional summer temperature was the primary driver. These temperature changes closely track sea surface temperature (SST) variations in the Indo-Pacific Warm Pool (IPWP). Conclusions This study provides a robust glacial chronology for the HZS and reveals four major glacier events from the LGM to T1. The findings highlight the high sensitivity of glaciers in the southeastern QXP to regional summer temperature, which is linked to the SST in the IPWP. Recommendations and perspectives Reconstructing glacial histories is crucial for understanding Quaternary glaciation across the QXP. However, due to the region’s vastness, many areas remain undated. Therefore, further chronological investigations across more glaciated sectors of the QXP are essential.