© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Umling, N. E., Oppo, D. W., Chen, P., Yu, J., Liu, Z., Yan, M., Gebbie, G., Lund, D. C., Pietro, K. R., Jin, Z. D., Huang, K., Costa, K. B., & Toledo, F. A. L. Atlantic circulation and ice sheet influences on upper South Atlantic temperatures during the last deglaciation. Paleoceanography and Paleoclimatology, 34(6), (2019): 990-1005, doi:10.1029/2019PA003558.
Atlantic Meridional Overturning Circulation (AMOC) disruption during the last deglaciation is hypothesized to have caused large subsurface ocean temperature anomalies, but records from key regions are not available to test this hypothesis, and other possible drivers of warming have not been fully considered. Here, we present the first reliable evidence for subsurface warming in the South Atlantic during Heinrich Stadial 1, confirming the link between large‐scale heat redistribution and AMOC. Warming extends across the Bølling‐Allerød despite predicted cooling at this time, thus spanning intervals of both weak and strong AMOC indicating another forcing mechanism that may have been previously overlooked. Transient model simulations and quasi‐conservative water mass tracers suggest that reduced northward upper ocean heat transport was responsible for the early deglacial (Heinrich Stadial 1) accumulation of heat at our shallower (~1,100 m) site. In contrast, the results suggest that warming at our deeper site (~1,900 m) site was dominated by southward advection of North Atlantic middepth heat anomalies. During the Bølling‐Allerød, the demise of ice sheets resulted in oceanographic changes in the North Atlantic that reduced convective heat loss to the atmosphere, causing subsurface warming that overwhelmed the cooling expected from an AMOC reinvigoration. The data and simulations suggest that rising atmospheric CO2 did not contribute significantly to deglacial subsurface warming at our sites.
We thank H. Abrams, G. Swarr, and J. Watson for technical assistance. This work was funded by the U.S. National Science Foundation grant OCE15‐558341, the Investment in Science Fund at the Woods Hole Oceanographic Institution, and an Australian Research Council Future Fellowship (FT140100993). The data are included in the supporting information and are available online (https://www.ncdc.noaa.gov/paleo/study/26530).
Atlantic Meridional Overturning Circulation
South Atlantic temperatures
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