摘要
基于末次冰盛期(LGM)至早全新世冰碛垄的^(10)Be暴露测年数据重建冰川退缩过程,对理解冰期-间冰期气候转型至关重要。针对单个地点冰碛序列保存不完整导致的北半球整体退缩过程不清晰的问题,本文集成4003个^(10)Be数据,建立了802条年龄范围介于26.5~10 ka之间的冰碛垄数据集,并划分为亚洲、欧洲、北美洲和格陵兰四个分区,分别计算各分区以及北半球数据集(不含格陵兰)的高斯组分。结果显示北半球层面存在八个冰川集中退缩时段,分别为(23.9±1.0)ka、(20.5±1.3)ka、(18.3±0.7)ka、(16.6±0.8)ka、(14.7±0.8)、(13.0±0.7)ka、(11.4±0.4)ka和(10.3±0.6)ka。前两次退缩主要响应北半球夏季太阳辐射增强,第三至第七次与大气CO_(2)浓度跃升有关,第八次受早全新世北半球夏季太阳辐射峰值影响。分区对比显示,约24 ka的退缩时段除北美和格陵兰外其他区域普遍存在,反映冰盖与山地冰川对气候变化的响应差异。其余时段区域差异主要源于冰碛垄暴露年龄误差和样本数量。本研究通过集成大量^(10)Be年龄数据重建LGM以来北半球冰川的演化过程,为该时期冰川-气候耦合模型及海平面变化机制提供了关键的地质数据约束。
Reconstructing glacier retreat from the Last Glacial Maximum(LGM)to the early Holocene using cosmogenic^(10)Be exposure dating of moraines is essential for understanding the climatic transition between glacial and interglacial periods.This period,spanning approximately 26.5~10 ka,is marked by major reorganizations in the global climate system,including rapid temperature shifts,fluctuations in atmospheric CO_(2),changes in ocean circulation,and variations in orbital forcing.These processes collectively shape ice sheet dynamics and in⁃fluence cryospheric feedbacks in the Northern Hemisphere.However,the fragmented preservation of moraine sequences at individual sites has hindered efforts to resolve the spatiotemporal patterns of glacier retreat on a con⁃tinental scale.Single-site records often fail to capture the timing and magnitude of broader deglacial trends.To overcome this limitation,this study compiled a comprehensive dataset of 4003 published^(10)Be exposure ages from 802 well-dated moraines spanning the period between 26.5 and 10 ka.The dataset encompassed a wide range of glacial settings and climates,offering a rare opportunity to conduct integrated regional and hemisphericscale analyses.The moraines were grouped into four major regions—Asia,Europe,North America,and Green⁃land—to enable comparative analysis.All^(10)Be exposure ages were recalculated using a consistent,globally aver⁃aged^(10)Be production rate and the LSDn(time-dependent)scaling scheme.This recalibration ensured inter-study comparability and minimized biases caused by inconsistent production rates or scaling methods across different studies.To resolve the temporal distribution of glacier retreat events,the Probabilistic Cosmogenic Age Analy⁃sis Tool(P-CAAT)was employed based on probability density estimation(PDE)of exposure ages.This meth⁃od identified statistically significant clusters of moraine ages by fitting the composite age distribution with multi⁃ple Gaussian components,enabling the identification of peak periods of moraine formation or abandonment.Gaussian component analysis was conducted independently for each region and for a combined Northern Hemi⁃sphere dataset excluding Greenland.The Greenland moraines were analyzed separately due to preservation pat⁃terns heavily constrained by the spatial extent and temporal evolution of the ice sheet margin,differing from oth⁃er regions.This analytical framework enabled the identification of eight statistically significant hemisphericscale glacier retreat episodes,centered at(23.9±1.0)ka,(20.5±1.3)ka,(18.3±0.7)ka,(16.6±0.8)ka,(14.7±0.8)ka,(13.0±0.7)ka,(11.4±0.4)ka,and(10.3±0.6)ka.The first two episodes occurring before 19 ka were primarily attributed to increases in Northern Hemisphere summer insolation due to orbital forcing.In contrast,the third through seventh episodes occurred after 19 ka and broadly coincided with abrupt increases in atmospheric CO_(2),indicating that greenhouse gas forcing became the dominant driver of glacier retreat.The final retreat episode around 10.3 ka aligned with the peak in summer insolation during the early Holocene.Regional comparison showed a high degree of synchronicity in retreat timing,although the earliest phase(~24 ka)was ab⁃sent from the Greenland and North American records,likely due to differing responses between ice sheet and mountain glacier systems.Some variability in the number or prominence of retreat episodes across regions could also be attributed to differences in sample density and uncertainties in exposure ages.This study represents one of the most extensive syntheses of^(10)Be moraine chronologies in the Northern Hemisphere to date.By integrating a large,globally distributed dataset and applying a standardized analytical workflow,this study improves the temporal resolution of deglacial patterns and provides critical geological constraints for climate-cryosphere inter⁃action models.The findings enhance the understanding of the timing and drivers of glacier retreat and have impli⁃cations for refining ice sheet reconstructions,glacial isostatic adjustment models,and past sea-level estimation.Moreover,the observed regional differences highlight the importance of glacier type,geographic context,and climate forcing in shaping the heterogeneous responses of ice masses to global climate change.
作者
郑超刚
张志刚
孔兴功
赵志军
ZHENG Chaogang;ZHANG Zhigang;KONG Xinggong;ZHAO Zhijun(School of Geography,Nanjing Normal University,Nanjing 210023,China;Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application,Nanjing 210023,China;Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing 210023,China)
出处
《冰川冻土》
2025年第4期875-886,共12页
Journal of Glaciology and Geocryology
基金
第二次青藏高原综合科学考察研究项目(2019QZKK0205)
国家自然科学基金项目(42071006)
中国科学院战略性先导科技专项(A类)项目(XDA20100300)资助。
