Alkenone δ13C as a Proxy for PastPCO2 in Surface Waters: Results from the Late Quaternary Angola Current
Alkenone δ13C as a Proxy for PastPCO2 in Surface Waters: Results from the Late Quaternary Angola Current
复制标题
烯酮 δ13C 作为地表水中过去 PCO2 的代表：晚第四纪安哥拉洋流的结果
DOI：
--
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
R. Schneider
中科院分区：
文献类型：
--
作者：
N. Andersen;P. Müller;G. Kirst;R. Schneider
二氧化碳是最重要的温室气体之一，由于人类活动，其在大气中的浓度正在增加。对于使用自然CO2动力学作为理解人为pCO 2上升的气候后果的关键，海洋由于其比大气大得多的碳库而发挥着重要作用。通过研究海洋沉积物有机质中稳定碳同位素的比值，有可能估算古代表层沃茨中CO2的分压。有机化合物C37：2烯酮，其唯一来源是自养海藻，被选为δ 13 C分析和其同位素组成用于重建过去20万年来在东部安哥拉盆地表层的PCO 2水平。除了古溶解CO2浓度的变化（[CO2（aq）] = ce），碳需求的影响，这取决于藻类的生长速度被认为是。在这里，C37：2烯酮（EP）的核心顶部沉积物从赤道和南大西洋的碳同位素分馏校准前工业[CO2（aq）]和磷酸盐浓度在表面沃茨。根据这些数据，计算反映细胞内碳需求的变量B =（25%-ep）* ce。该变量B与海水磷酸盐的环境浓度相关，并取决于生长速率。考虑到岩芯-顶部沉积物中的δ 15 N与现代表层沃茨中的磷酸盐浓度相关，将整体沉积物δ 15 N用作计算古代b值的替代参数。在此基础上，GeoB 1016-3的烯酮δ 13 C记录证明了过去20万年来大气二氧化碳的永久海洋来源。由于使用δ 15 N导出的b值而不是B =常数，安哥拉盆地在冰期似乎是比现在更强的CO2源。碧玉等人（1994年）报告了赤道太平洋中部的类似结果。这些观测结果表明，在冰期低纬度上升流地区的生产力提高是不是负责冰川大气中的CO2含量较低。
Carbon dioxide is one of the most important greenhouse gases which are increasing in atmospheric concentration due to human activities. For using natural CO2 dynamics as a key to understanding the climatic consequences of anthropogenic pCO2 rise, the ocean plays an important role due to its much larger carbon pool compared to the atmosphere. By studying the ratio of stable carbon isotopes in organic matter from marine sediments, it is possible to estimate the partial pressure of CO2 in surface waters during ancient times. The organic compound C37:2 alkenone, whose sole origin is from autotrophic marine algae, was chosen for δ13C analysis and its isotopic composition used to reconstruct past PCO2 levels in the surface layer of the eastern Angola Basin for the last 200,000 years. In addition to the variation of ancient concentrations of dissolved CO2 ([CO2(aq)] = ce), the effect of carbon demand which depends on algal growth rate was considered. Here to, carbon isotopic fractionation of C37:2 alkenones (ep) in core-top sediments from the equatorial and the South Atlantic was calibrated against pre-industrial [CO2(aq)] and phosphate concentrations in surface waters. From these data, a variable b = (25 %-ep)* ce which reflects intracellular carbon demand was calculated. This variable b correlates with the ambient concentration of seawater phosphate and depends on growth rates. The bulk sediment δ15N was used as a proxy parameter for calculating ancient b-values, taking into account that δ15N in core-top sediments is correlated to phosphate concentration in modern surface waters. On this basis, the alkenone δ13C record of GeoB 1016-3 documents a permanent oceanic source for atmospheric carbon dioxide during the last 200,000 years. As a consequence of using δ15N derived b-values instead of b = constant, the Angola Basin appears to have been an even stronger CO2 source during glacial periods than at present. Qualitatively similar results were reported by Jasper et al. (1994) for the central Equatorial Pacific. These observations suggest that enhanced productivity of low-latitude upwelling areas during glacial periods is not responsible for the lower CO2 content of the glacial atmosphere.