支链GDGTs与黄土古温度重建:机遇与挑战

BRANCHED GDGTS AND LOESS PALEOTEMPERATURE RECONSTRUCTION:OPPORTUNITIES AND CHALLENGES

目前对全球古温度的理解主要基于海洋记录,由于缺乏可靠的陆地古温度指标,对陆地温度变化的认识较为有限,这限制了对全球变暖背景下,陆地温度变化规律和机制的深入理解。支链甘油二烷基甘油四醚类化合物(brGDGTs)是某些细菌微生物细胞脂膜中的四醚化合物,近20年来已成为广泛关注的陆地古温度计。该温度计一经推出,便在黄土古温度,特别是长时间尺度的古温度重建中发挥了重要作用。本研究首先回顾了brGDGTs温度计的发展历史,总结了近年来该温度计在细菌培养实验、现代过程调研、仪器分析方法、数据处理技术等方面的创新和进展。然后介绍了支链GDGTs在黄土古土壤剖面中不同时间尺度的古温度重建研究进展。黄土高原brGDGTs记录的陆地温度呈现明显的冰期-间冰期波动特征,表明太阳辐射和全球冰量对陆地温度变化重要的驱动作用;但与海洋温度相比,冰盛期-冰消期时段增温超前于海洋记录,推测陆地下垫面(植被、土壤湿度等)动态演化可能会对陆地温度变化起着重要的调控作用。最后多角度分析了brGDGTs陆地古温度重建面临的机遇和挑战。作为稀缺的陆地古温度计,brGDGTs为认识陆地温度变化规律和机制提供了难得的工具,但其确切生物来源、形成机制尚不明确。另外,全球黄土brGDGTs温度在变化趋势、周期和幅度上存在较大差异,且造成这种差异的原因还不清楚。为了应对这些挑战,应继续加强brGDGTs温度计的基础理论研究,明确其来源和形成机制,优化分析方法和校正模型。同时,结合现代观测和模拟研究,探究不同时间尺度下陆地下垫面(植被、土壤湿度等)与温度变化之间的反馈机制,进一步丰富我们对全球温度变化规律和机制的认识。

Currently,our understanding of global paleotemperatures is primarily based on marine records.Due to the lack of reliable terrestrial paleotemperature indicators,our knowledge of terrestrial paleotemperatures,crucial for our survival,is limited.This constraint hampers our understanding of the patterns and mechanisms of terrestrial temperature changes under the background of global warming.Branched Glycerol Dialkyl Glycerol Tetraether compounds(brGDGTs),synthesized by bacterial membrane lipids,have emerged as popular terrestrial paleothermometers in the past two decades,playing a significant role in long-term scale reconstructions,particularly in loess paleotemperature reconstructions.The paper first reviews the developmental history of brGDGTs temperature proxies,summarizing recent innovations and advancements in bacterial culture experiments,modern process surveys,instrumental analysis methods,and data processing techniques.It then introduces the progress of branched GDGT-based reconstructions of paleotemperatures at various time scales in loess paleosols.Records of terrestrial temperatures from brGDGTs on the Chinese Loess Plateau exhibit distinct glacial-interglacial fluctuations,indicating significant driving roles of solar radiation and global ice volume in terrestrial temperature changes.However,the temperature increases during the glacial maximum to deglaciation in led to that of marine records,suggesting that dynamic evolution of land surfaces(vegetation,soil moisture,etc.)may play an important regulatory role in terrestrial temperature changes.Finally,the article provides a multi-faceted analysis of the opportunities and challenges facing brGDGT-based reconstructions of terrestrial paleotemperatures.As a scarce tool for reconstructing terrestrial paleotemperatures,brGDGTs offer valuable records for understanding patterns and mechanisms of terrestrial temperature changes.Yet,uncertainties remain regarding their exact biological sources and formation mechanisms,and significant challenges persist in explaining the global variations in trends,cycles,and magnitudes of brGDGT-based temperatures in loess.To tackle these challenges,it is crucial to enhance the foundational theoretical research of brGDGT proxies,clarifying their exact sources and formation mechanisms,and optimizing analytical methods and calibration models.Additionally,integrating modern observational and simulation studies can help explore the feedback mechanisms between land surface properties(such as vegetation and soil moisture)and temperature changes at different time scales.This approach will further enrich our understanding of the patterns and mechanisms of global temperature variability.