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Increased ventilation age of the deep northeast Pacific Ocean during the last deglaciation


The rise in atmospheric carbon dioxide during the last deglaciation may have been driven by the release of carbon from the abyssal ocean1,2. This mechanism would require a poorly ventilated deep Pacific Ocean during the Last Glacial Maximum and enhanced exchange with the atmosphere during deglaciation. Here we use radiocarbon measurements of planktonic and benthic foraminiferal shells from a core collected at 2.7 km water depth in the northeast Pacific to estimate the ventilation age of deep waters using the projection age method. In contrast to the above scenario, we show that ventilation ages during the Last Glacial Maximum were similar to today. This suggests that this part of the Pacific was not an important reservoir of carbon during glacial times. During deglaciation, ventilation ages increased by 1,000 years, indicating a decrease in the ventilation rate, an increase in the surface water reservoir age in the Southern Ocean, or an influx of old carbon from another source. Despite the increased ventilation age during deglaciation, the deep northeast Pacific still had a higher 14C/C ratio than intermediate waters near Baja California3. We therefore conclude that the deep northeast Pacific was apparently not old enough to be the source of deglacial radiocarbon anomalies found shallower in the water column.

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Figure 1: Age model for W8709A-13PC showing planktonic (circles) and benthic (triangles) radiocarbon ages plotted versus depth in the core.
Figure 2: Stable isotope data, benthic–planktonic ages, and 14C ventilation ages for W8709A-13PC.
Figure 3: Summary of projection age estimates for the deep Pacific.
Figure 4: Time series of northeast Pacific Δ14C.


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We would like to thank J. Wilson, R. Sortor, and J. Hoffman for technical support. We are grateful to the Oregon State core laboratory for sample collection and archiving and the captain and crew of the R/V Wecoma for retrieving W8709A-13PC. This work was supported by the US National Science Foundation (A.C.M.) and the University of Michigan (D.C.L).

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D.C.L. and A.C.M. initiated the project. D.C.L. processed the sediment samples for foraminifera and D.C.L. and A.C.M. prepared the foraminifera for 14C dating. J.S. performed the radiocarbon analyses and initial data quality assessment. D.C.L. performed the ventilation age calculations and wrote the initial manuscript. Both A.C.M. and J.S. provided key editorial input during the writing process.

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Correspondence to David C. Lund.

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The authors declare no competing financial interests.

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Lund, D., Mix, A. & Southon, J. Increased ventilation age of the deep northeast Pacific Ocean during the last deglaciation. Nature Geosci 4, 771–774 (2011).

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