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A new radiolarian transfer function for the pacific ocean and application to fossil records: Assessing potential and limitations for the last glacial-interglacial cycle
Global and Planetary Change ( IF 3.9 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.gloplacha.2020.103186
Iván Hernández-Almeida , Demetrio Boltovskoy , Svetlana B. Kruglikova , Giuseppe Cortese

Abstract Climatic and oceanographic processes in the Pacific Ocean have global implications. Reliable sedimentary proxies in this region are thus necessary to understand the magnitude of past climate variability. Radiolarian assemblages are of particular relevance in some regions of the Pacific Ocean where other proxies are either poorly preserved or are biased towards a specific season. Previously published radiolarian-based transfer functions in the Pacific Ocean did not cover some regions, such as the Western Pacific marginal seas or high-latitude Southwestern Pacific. Filling these gaps in sample distribution and using a thorough methodology for finding the most important variable for radiolarian assemblages in surface sediment are both essential steps in quantitative studies. In this study, we use published radiolarian census counts from 801 core-tops distributed across the Pacific Ocean, to investigate which environmental factors drive the assemblages. We harmonized taxonomically the modern microfossil dataset, and using multivariate statistical analyses, we determined that sea surface temperature at 10 m (SST10) is the most important variable influencing the changes observed in the radiolarian assemblages. The calibration method weighted-mean modern analogue technique with five analogs (WMAT-K5) corrected for autocorrelation using a cut-off distance of 500 km, showed a performance of R2cv = 0.83; RMSEP = 3.8 °C. This calibration method was then applied to taxonomically harmonized radiolarian census counts from 31 cores located in the Bering Sea, Western Pacific marginal seas, and Southwest and Eastern Equatorial Pacific, with some of these records covering at least the last 165 ka. We assessed the analogue quality and significance of the downcore SST10 reconstructions in all of them. We found that temperatures at 10 and 200 m were the most significant variables for the fossil assemblages. Finally, we compare the temperature reconstructions to previously published radiolarian-based SST estimates for the same cores, or to other SST records based on other methodologies. We find some differences between our new temperature estimates compared to existing ones, in particular in the Eastern Equatorial Pacific. Comparison to other methods in the Japan and Bering Sea and Sea of Okhotsk show that radiolarian-based reconstructions provide robust temperature estimates compared to biogeochemical methods, which showed SST overestimation during glacial periods.

中文翻译:

一种新的太平洋放射虫传递函数及其在化石记录中的应用:评估最后一次冰期-间冰期循环的潜力和局限性

摘要 太平洋的气候和海洋过程具有全球影响。因此,该地区可靠的沉积代理对于了解过去气候变化的幅度是必要的。放射虫组合在太平洋的某些地区特别重要,在这些地区,其他代表要么保存不佳,要么偏向于特定季节。之前发表的基于放射虫的太平洋传递函数并未涵盖某些区域,例如西太平洋边缘海或高纬度西南太平洋。填补样本分布中的这些空白并使用彻底的方法来寻找表层沉积物中放射虫组合的最重要变量,都是定量研究的重要步骤。在这项研究中,我们使用来自分布在太平洋的 801 个核心顶部的已发布的放射虫普查计数,来调查哪些环境因素驱动了这些组合。我们在分类学上统一了现代微化石数据集,并使用多变量统计分析确定 10 m 处的海面温度 (SST10) 是影响放射虫组合中观察到的变化的最重要变量。使用 500 公里截止距离校正自相关的五个类似物(WMAT-K5)的校准方法加权平均现代模拟技术,表现出 R2cv = 0.83 的性能;RMSEP = 3.8 °C。然后将该校准方法应用于位于白令海、西太平洋边缘海以及西南和东赤道太平洋的 31 个核心的分类统一的放射虫普查计数,其中一些记录至少涵盖了最近的 165 ka。我们评估了所有这些下核 SST10 重建的模拟质量和重要性。我们发现 10 米和 200 米处的温度是化石组合最重要的变量。最后,我们将温度重建与先前发布的基于放射虫的相同核心的 SST 估计值或基于其他方法的其他 SST 记录进行比较。我们发现我们的新温度估计与现有温度估计之间存在一些差异,特别是在东赤道太平洋。与日本、白令海和鄂霍次克海的其他方法的比较表明,与生物地球化学方法相比,基于放射虫的重建提供了可靠的温度估计,生物地球化学方法显示冰期期间 SST 被高估。
更新日期:2020-07-01
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