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Title: Carbon isotope minima in the South Atlantic during the last deglaciation: evaluating the influence of air-sea gas exchange

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 oceanδ13C 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 benthicδ13C during HS1 leads planktonicδ13C 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 oceanδ13C signal can be explained by temperature-dependent equilibration with a13C-depleted atmosphere, with the remainder due to biological productivity, input of carbon from the abyss, or more » reduced air-sea equilibration.

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Environmental Research Letters
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Article No. 055004
IOP Publishing
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National Science Foundation
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