Deglacial Evolution of Atlantic Mid-Depth and Intermediate-Depth Water Variability

Abstract:

Deglacial variations in the Atlantic Meridional Overturning Circulation (AMOC) feature prominently in hypotheses of deglacial climate variability and atmospheric CO₂rise. However, there is lingering uncertainty in the glacial deepwater mass configuration (e.g. Gebbie, 2014) and deglacial AMOC variability is even more poorly understood. For example, the deglacial evolution of the contribution of northern and southern source waters to the middle and intermediate depths of the Atlantic is still vigorously debated. Here, we evaluate the evolution of subsurface Atlantic ventilation, emphasizing middle and intermediate depths, by comparing new and published records of water mass variability to output from transient model simulations designed to provide insight into the climatic and oceanographic effects of a dramatic reduction in the AMOC, such as apparently occurred during Heinrich Stadial 1 (Liu et al., 2009; Schmittner and Lund, 2014).

Gebbie, G. (2014), How much did Glacial North Atlantic Water shoal? Paleoceanography, 29, 190–209, doi: 10.1002/2013PA002557.

Liu, Z., B. Otto-Bliesner, F. He, E. Brady, R. Thomas, P. U. Clark, A. E. Carlson, J. Lynch-Stieglitz, W. Curry, E. Brook, D. Erickson, R. Jacob, J. Kutzbach, J., and J. Chen (2009), Transient climate simulation of last deglaciation with a new mechanism for Bølling-Allerød warming, Science, 325, 310-314.

Schmittner, A., and Lund, D. C. (submitted), Carbon Isotopes Support Atlantic Meridional Overturning Circulation Decline as a Trigger for Early Deglacial CO₂ rise Climate of the Past Discussions.