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首页> 外文期刊>Canadian Water Resources Journal >Climate reconstructions based on postglacial macrofossil assemblages from four river systems in southwestern Alberta
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Climate reconstructions based on postglacial macrofossil assemblages from four river systems in southwestern Alberta

机译：基于来自艾伯塔省西南部四个河流系统的冰川后化石组合的气候重建

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摘要

Following floods experienced in southwestern Alberta in June 2013, 36 palaeoenvironmental sediment samples were collected from the banks of four affected streams: the Kananaskis River, Highwood River, Tongue Creek and Jumping-pound Creek. The sampled layers were deposited during the Holocene, and provide evidence of riparian ecology in the region since the end of the last glacial interval. The samples were processed to extract sub-fossil macroremains (including seeds, fruits, and aquatic and terrestrial mollusc shells). Macrofossils are particularly useful for creating fine-resolution (site-specific) reconstructions. An innovative aspect of this study was the derivation of regional bioclimatic trends through time. This was achieved by applying a dual-layered weighted calibration function which incorporated the relative productivity of indicator taxa, their modelled climatic optima, and the influence of climate (temperature and precipitation) on their ecological niche. Optima and climatic influence values were calculated using the machine-learning maximum entropy environmental niche modelling tool, MAXENT, trained on global occurrence records for the taxa. This study aimed to address gaps in prior palaeoenvironmental research, allowing for a spatially explicit quantitative reconstruction of climate in the transitional foothill region near Calgary. Results indicated warm conditions immediately following glacial retreat, followed by an early to mid-Holocene cooling which coincided with the driest interval. Temperature and moisture regimes oscillated in the mid-Holocene, exhibiting the highest values for both parameters. Increased moisture was at least in part prompted by increased input from summer glacial meltwater (the result of higher summer temperatures) which added to the riparian water budget. The mid-to late Holocene, and up to modern times, showed a gradual decrease in both moisture and temperature, until stabilizing near the Holocene average.
机译：继2013年6月在艾伯塔省西南部发生洪水之后，从四个受影响河流（卡纳那斯基斯河，Highwood河，Tongue Creek和Jumping-pound Creek）的河岸采集了36个古环境沉积物样本。采样层是在全新世期间沉积的，并提供了自上次冰川期结束以来该地区河岸生态学的证据。对样品进行处理，以提取亚化石的宏观残留物（包括种子，果实，水生和陆生软体动物壳）。大型化石对于创建高分辨率（针对特定地点）的重建特别有用。这项研究的一个创新方面是随着时间的推移推导了区域生物气候趋势。这是通过应用双层加权校准函数实现的，该函数结合了指标分类单元的相对生产率，其模拟的气候最佳值以及气候（温度和降水）对其生态位的影响。使用机器学习的最大熵环境生态位建模工具MAXENT计算最佳和气候影响值，该工具在类群的全球发生记录中受过训练。这项研究旨在解决以前的古环境研究中的空白，从而在卡尔加里附近的过渡山麓地区实现空间明确的气候定量重建。结果表明，冰川退缩后立即出现了温暖的条件，然后是全新世早期至中期的冷却，这与最干燥的间隔相吻合。全新世中期的温度和湿度模式都发生了振荡，这两个参数均显示出最高值。水分增加至少部分是由于夏季冰川融水的投入增加（夏季气温升高的结果），这增加了河岸水的预算。全新世的中晚期至近现代，水分和温度均逐渐下降，直到稳定在全新世的平均值附近。

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