Large δ13C Gradients in the Preindustrial North Atlantic Revealed
Large δ13C Gradients in the Preindustrial North Atlantic Revealed
复制标题
工业化前北大西洋的δ13C大梯度被揭示
作者：
A. Olsen;U. Ninnemann
丢失的细节通常通过过去和现在碳同位素分布的差异来推断海洋环流的变化，但进行这种比较忽略了现代化石燃料燃烧已经改变了海洋碳同位素组成的事实。这反过来又掩盖了最近大规模水运动的细节。 Olsen 和 Ninnemann（第 658 页）纠正了北大西洋的这种效应，并表明碳同位素的自然分布具有更多细节，并且与水体分布明显相关。这些结果改变了现代气候变化背景下关于冰期-间冰期海洋变化的一些重要观点。北大西洋碳同位素的人类活动前分布为气候研究提供了正确的基线。有孔虫化石的碳同位素组成（13C/12C，表示为δ13C）是用于推断过去海洋通风变化的主要示踪剂，并以现代海洋δ13C分布为框架来解释其变化。然而，目前海洋 δ13C 分布被同位素轻的人为二氧化碳强烈覆盖。对北大西洋 (NA) 海洋 C-13 Suess 效应的校正表明，原始 NA δ13C 分布具有更丰富、更详细的结构，与水团分布的关系更明显。我们的研究结果修正了关于冰期-间冰期海洋 δ13C 差异的一些基本看法，并允许在现代气候变化的背景下理解古 δ13C 变化。
Lost Details Changes in ocean circulation are commonly inferred by differences between the distribution of carbon isotopes in the past and now, but making such comparisons neglects the fact that modern fossil fuel burning has modified the carbon isotopic composition of the ocean. This in turn obscures details about recent mass movement of water. Olsen and Ninnemann (p. 658) correct for this effect in the North Atlantic and show that the natural distribution of carbon isotopes has more detail and is clearly related to water mass distributions. The results change some important ideas about glacial-interglacial ocean variations within the context of modern climate variability. The preanthropogenic distribution of carbon isotopes in the North Atlantic provides a correct baseline for climate studies. The carbon isotopic composition (13C/12C, expressed as δ13C) of fossil foraminifera is the primary tracer used to infer changes in past ocean ventilation, and its variations are interpreted by using the modern oceanic δ13C distribution as a framework. However, the present ocean δ13C distribution is strongly overprinted by isotopically light anthropogenic carbon dioxide. A correction for this oceanic C-13 Suess effect in the North Atlantic (NA) shows that the pristine NA δ13C distribution has a richer and more detailed structure that is more clearly related to water mass distributions. Our results revise some fundamental perceptions regarding glacial-interglacial ocean δ13C differences and allow paleo-δ13C variations to be understood within the context of modern climate variability.