Carbon isotope minima in the South Atlantic during the last deglaciation: evaluating the influence of air-sea gas exchange
Carbon isotope minima in the South Atlantic during the last deglaciation: evaluating the influence of air-sea gas exchange
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DOI：
10.1088/1748-9326/ab126f
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发表时间：
2019-05
影响因子：
6.7
通讯作者：
D. Lund;J. Hertzberg;M. Lacerra
中科院分区：
文献类型：
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作者：
D. Lund;J. Hertzberg;M. Lacerra
在Heinrich Stadial 1（HS1，14.5-17.5 kyr BP）和新仙女木（YD，11.6-12.9 kyr BP）期间，碳同位素极小值是大西洋中深度（1.5-2.5 km）普遍存在的特征，最有可能的驱动因素是大西洋经向翻转环流（AMOC）的崩溃。负碳同位素异常也发生在整个海洋和大气表面，但其与 AMOC 崩溃相关的时间和潜在驱动因素仍不清楚。在这里，我们使用来自两个巴西边缘岩心（位于水深 1.8 公里和 2.1 公里）的高分辨率底栖和浮游稳定同位素记录来评估 AMOC 变化与表面海洋 δ13C 信号之间的超前-滞后关系。在每种情况下，HS1 期间底栖 δ13C 的减少都会导致浮游 δ13C 减少 800 ± 200 年。由于记录基于相同的样本，因此相对时间受到岩心地层学的限制。我们的结果表明，AMOC 崩溃引发了一系列事件，这些事件在不到 1 kyr 的时间内通过海洋碳循环传播。浮游有孔虫和大气记录的直接比较表明，部分海洋表面 δ13C 信号可以通过与 13C 耗尽的大气的温度依赖性平衡来解释，其余部分则归因于生物生产力、来自深渊的碳输入或减少的海气平衡。
Carbon isotope minima were a ubiquitous feature in the mid-depth (1.5–2.5 km) Atlantic during Heinrich Stadial 1 (HS1, 14.5–17.5 kyr BP) and the Younger Dryas (YD, 11.6–12.9 kyr BP), with the most likely driver being collapse of the Atlantic Meridional Overturning Circulation (AMOC). Negative carbon isotope anomalies also occurred throughout the surface ocean and atmosphere, but their timing relative to AMOC collapse and the underlying drivers have remained unclear. Here we evaluate the lead-lag relationship between AMOC variability and surface ocean δ13C signals using high resolution benthic and planktonic stable isotope records from two Brazil Margin cores (located at 1.8 km and 2.1 km water depth). In each case, the decrease in benthic δ13C during HS1 leads planktonic δ13C by 800 ± 200 years. Because the records are based on the same samples, the relative timing is constrained by the core stratigraphy. Our results imply that AMOC collapse initiates a chain of events that propagates through the oceanic carbon cycle in less than 1 kyr. Direct comparison of planktonic foraminiferal and atmospheric records implies a portion of the surface ocean δ13C signal can be explained by temperature-dependent equilibration with a 13C-depleted atmosphere, with the remainder due to biological productivity, input of carbon from the abyss, or reduced air-sea equilibration.