Refining the alkenone-pCO(2) method I: Lessons from the Quaternary glacial cycles
Refining the alkenone-pCO(2) method I: Lessons from the Quaternary glacial cycles
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改进烯酮-pCO(2) 方法 I：第四纪冰川循环的教训
DOI：
10.1016/j.gca.2019.06.032
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发表时间：
2019
影响因子：
5
通讯作者：
Pagani Mark
中科院分区：
文献类型：
--
作者：
Zhang Yi Ge;Pearson Ann;Benthien Albert;Dong Liang;Huybers Peter;Liu Xiaoqing;Pagani Mark
烯烃- pco2法是重建新生代大气co2最常用的方法之一。该方法依赖于藻类光合作用过程中稳定碳同位素的分离（εp37:2）和生理标度参数b，该参数考虑了生长速度、细胞大小和膜通透性等生物因素。然而，晚更新世的烯酮衍生的二氧化碳记录与冰芯二氧化碳的相关性很差，这对经典模型提出了挑战，该模型认为大部分用于球石藻光合作用的二氧化碳是通过简单扩散获得的。在这项研究中，我们探讨了这个术语的性质和εp37:2 topco2变化敏感性的潜在模式。本文在南海（MD01-2392）和热带大西洋（ODP 668B）生成了两个新的εp37:2记录，并整理了其他已发表的冰期-间冰期旋回的εp37:2记录。利用εp37:2数据、海洋温度估计和冰芯二氧化碳，我们能够反向计算出相应的b值。在所有地点，冰期周期变化。b的最大值对应于间冰期的峰值，表明间冰期浮游植物生长速度比冰期更快或细胞尺寸更小。在冰期和间冰期之间εp37:2的变化范围（Δεp37:2）与生长条件的尺度一致，符合基于co2扩散的碳同位素分馏模型的预测。换句话说，εp37:2 topco2变化的敏感性在现代值较大的地方增加，这与由于假定b的稳定性而提出的少营养位点最适合烯烃- co2应用的建议相矛盾。利用每个地点的平均反算值，MD01-2392和ODP 668B的二氧化碳综合估计值——这两个地点有足够的Δεp37:2sensitivity——显示出与冰芯二氧化碳记录的广泛一致。
The alkenone-pCO2method is one of the most widely used approaches to reconstruct atmospheric CO2in the Cenozoic. The method depends upon fractionation of stable carbon isotopes during algal photosynthesis, expressed as εp37:2, and a physiological scaling parameter,b, that accounts for biological factors such as growth rate, cell size, and membrane permeability. Alkenone-derived CO2records for the late Pleistocene, however, are poorly correlated with ice core CO2, challenging the classic model that considers most of the CO2used for coccolithophore photosynthesis to be acquired through simple diffusion. In this study, we investigate the nature of thebterm and the underlying patterns of the sensitivity of εp37:2topCO2changes. We generated two new εp37:2records from the South China Sea (MD01-2392) and tropical Atlantic Ocean (ODP 668B) and compiled other published εp37:2records over glacial-interglacial cycles. Using the εp37:2data, ocean temperature estimates, and ice core CO2, we were able to back-calculate the corresponding values ofb. At all locations,bvaries over glacial cycles. The highest values ofbcorrespond to peak interglacial stages, indicating that the phytoplankton growth rate is faster or cell size is smaller during interglacials than during glacial periods. We further show that the range of εp37:2between glacial and interglacial conditions, Δεp37:2, scales with growth conditions, consistent with the predictions of the carbon isotope fractionation model based on CO2diffusion. In other words, the sensitivity of εp37:2topCO2changes increases where the modernbvalues are large, contradicting the recommendations that oligotrophic sites are the best for alkenone-CO2applications because of the presumed stability ofb. Using the average back-calculatedbvalue for each site, the compositepCO2estimates from MD01-2392 and ODP 668B – the two sites with adequate Δεp37:2sensitivity – show broad agreement with the ice core CO2record.