Evaluating global temperature calibrations for lacustrine branched GDGTs: Seasonal variability, paleoclimate implications, and future directions
Evaluating global temperature calibrations for lacustrine branched GDGTs: Seasonal variability, paleoclimate implications, and future directions
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DOI：
10.1016/j.quascirev.2023.108124
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发表时间：
2023-06
影响因子：
4
通讯作者：
Boyang Zhao;J. Russell;V. Tsai;A. Blaus;M. Parish;Jie Liang;A. Wilk;Xiaojing Du;M. Bush
中科院分区：
文献类型：
--
作者：
Boyang Zhao;J. Russell;V. Tsai;A. Blaus;M. Parish;Jie Liang;A. Wilk;Xiaojing Du;M. Bush
在湖泊沉积物中保存的支链甘油二烷基甘油四醚（brGDGTs）越来越多地被用来调查过去的陆地温度。brGDGT普遍存在于沉积环境中，保存完好，并且不同brGDGT中甲基的数量通常受温度控制。目前的brGDGT校准主要依赖于经验之间的相关性，不同的brGDGT在表层沉积物中的相对丰度和年均或暖季气温。由于温度的季节性差异和brGDGT产量随纬度的变化难以约束，这些方法可能会在全球温度校准中引入复杂性。在这里，我们报告新的brGDGT数据从整个热带地区，包括南美洲（n = 57），东非（n = 21），东南亚（n = 13），湖泊表层沉积物，并重新审视全球分布的brGDGT数据。我们发现一个统一的响应brGDGT的平均年气温在整个热带地区，尽管在不同地区的环境和地质条件的差异，突出温度的主导影响brGDGT分布。中高纬度沉积物中的brGDGT与热带沉积物中的brGDGT在性质上相似，但在数量上不同。我们发现，温度的季节性可以部分解释纬度的差异，这意味着需要纬度依赖brGDGT校准和/或改进的观测和模型，以限制brGDGT的季节性影响。将我们的新数据与之前发布的brGDGT数据相结合，我们开发并应用改进的温度校准。
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) preserved in lake sediments are increasingly used to investigate past terrestrial temperatures. brGDGTs are ubiquitous in sedimentary environments, well-preserved, and the number of methyl groups in different brGDGTs is generally controlled by temperature. Current brGDGT calibrations largely rely on empirical correlations between the relative abundances of different brGDGTs in surface sediments and either mean annual or warm season air temperatures. These approaches may introduce complications in global temperature calibrations due to differences in the seasonality of temperature and variations in brGDGT production with latitude that are difficult to constrain. Here, we report new brGDGTs data from lake surface sediments obtained throughout the tropics including South America (n = 57), East Africa (n = 21), and Southeast Asia (n = 13), and revisit globally distributed brGDGT data. We find a uniform response of brGDGTs to mean annual air temperature across the tropics despite differences in the environmental and geological conditions in different regions highlighting the dominant influence of temperature on brGDGT distributions. brGDGTs in mid- and high latitude sediment show a qualitatively similar but quantitatively different response to those in the tropics. We show that temperature seasonality can partially explain the latitudinal differences, implying the need for latitudinally-dependent brGDGT calibrations and/or improved observations and models to constrain seasonal effects on brGDGTs. Combining our new data with previously published brGDGT data, we develop and apply improved temperature calibrations.