Su, Zhan and Ingersoll, Andrew P. and He, Feng (2016) On the Abruptness of Bølling–Allerød Warming. Journal of Climate, 29 (13). pp. 4965-4975. ISSN 0894-8755. http://resolver.caltech.edu/CaltechAUTHORS:20160728-122027273
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Previous observations and simulations suggest that an approximate 3°–5°C warming occurred at intermediate depths in the North Atlantic over several millennia during Heinrich stadial 1 (HS1), which induces warm salty water (WSW) lying beneath surface cold freshwater. This arrangement eventually generates ocean convective available potential energy (OCAPE), the maximum potential energy releasable by adiabatic vertical parcel rearrangements in an ocean column. The authors find that basin-scale OCAPE starts to appear in the North Atlantic (~67.5°–73.5°N) and builds up over decades at the end of HS1 with a magnitude of about 0.05 J kg^(−1). OCAPE provides a key kinetic energy source for thermobaric cabbeling convection (TCC). Using a high-resolution TCC-resolved regional model, it is found that this decadal-scale accumulation of OCAPE ultimately overshoots its intrinsic threshold and is released abruptly (~1 month) into kinetic energy of TCC, with further intensification from cabbeling. TCC has convective plumes with approximately 0.2–1-km horizontal scales and large vertical displacements (~1 km), which make TCC difficult to be resolved or parameterized by current general circulation models. The simulation herein indicates that these local TCC events are spread quickly throughout the OCAPE-contained basin by internal wave perturbations. Their convective plumes have large vertical velocities (~8–15 cm s^(−1)) and bring the WSW to the surface, causing an approximate 2°C sea surface warming for the whole basin (~700 km) within a month. This exposes a huge heat reservoir to the atmosphere, which helps to explain the abrupt Bølling–Allerød warming.
|Additional Information:||© 2016 American Meteorological Society. Manuscript received 23 September 2015, in final form 30 March 2016. We thank Stefan Rahmstorf and three anonymous reviewers for insightful comments on the manuscript. We also thank editor Anthony Broccoli for the constructive suggestions. We thank Jess Adkins and Andy Thompson for helpful comments on the initial manuscript. This material is based upon work supported by the National Science Foundation under Grant AST-1109299. F.H. was supported by the U.S. NSF (AGS-1203430) and by the NOAA Climate and Global Change Postdoctoral Fellowship program, administered by the University Corporation for Atmospheric Research. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract DE-AC05-00OR22725.|
|Subject Keywords:||Circulation/ Dynamics; Conditional instability; Deep convection; Atm/Ocean Structure/ Phenomena; Bottom currents/bottom water; Physical Meteorology and Climatology; Paleoclimate; Models and modeling; General circulation models|
|Official Citation:||Zhan Su, Andrew P. Ingersoll, and Feng He, 2016: On the Abruptness of Bølling–Allerød Warming. J. Climate 29, 4965–4975, doi: 10.1175/JCLI-D-15-0675.1.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||28 Jul 2016 19:48|
|Last Modified:||28 Jul 2016 19:48|
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