Neodymium isotopic composition (εNd) has enjoyed widespread use as a palaeotracer, principally because it behaves quasi-conservatively in the modern ocean. However, recent bottom water εNd reconstructions from the eastern North Atlantic are difficult to interpret under assumptions of conservative behaviour. The observation that this apparent departure from conservative behaviour increases with enhanced ice-rafted debris (IRD) fluxes has resulted in the suggestion that IRD leads to the overprinting of bottom water εNd through reversible scavenging. In this study, a simple water column model successfully reproduces εNd reconstructions from the eastern North Atlantic at the Last Glacial Maximum and Heinrich Stadial 1, and demonstrates that the changes in scavenging intensity required for good model-data fit is in good agreement with changes in the observed IRD flux. Although uncertainties in model parameters preclude a more definitive conclusion, the results indicate that the suggestion of IRD as a source of non-conservative behaviour in the εNd tracer is reasonable and that further research into the fundamental chemistry underlying the marine neodymium cycle is necessary to increase confidence in assumptions of conservative εNd behaviour in the past.

中文翻译：

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冰筏碎片作为 εNd 古示踪剂非保守行为的来源：来自简单模型的见解

钕同位素组成 (εNd) 已广泛用作古示踪剂，主要是因为它在现代海洋中表现出准保守性。然而，在保守行为的假设下，最近来自北大西洋东部的底水 εNd 重建难以解释。观察到这种明显偏离保守行为会随着冰筏碎片 (IRD) 通量的增加而增加，这导致建议 IRD 通过可逆清除导致底水 εNd 的叠加。在这项研究中，一个简单的水柱模型成功地再现了北大西洋东部末次盛冰期和 Heinrich Stadial 1 的 εNd 重建，并证明良好模型数据拟合所需的清除强度变化与观察到的 IRD 通量变化非常一致。尽管模型参数的不确定性排除了更明确的结论，但结果表明，将 IRD 作为 εNd 示踪剂中非保守行为来源的建议是合理的，有必要进一步研究海洋钕循环背后的基础化学，以增加对过去保守的 εNd 行为假设的信心。