The role of the PMOC in modulating the deglacial shift of the ITCZ
Based on an energy-constraint framework, the effect of the Pacific meridional overturning circulation (PMOC) has been investigated on the meridional shift of the intertropical convergence zone (ITCZ). During Heinrich Event 1, the global ITCZ displaces southward in response to a shutdown of the Atlantic meridional overturning circulation (AMOC). However, the PMOC resumes and induces an enhanced northward meridional heat transport (MHT). Further analyses show that the resumption of the PMOC and its associated MHT can relieve the decrease of oceanic cross-equatorial heat transport by the collapsed AMOC and lower the compensating decline of atmospheric cross-equatorial meridional heat transport by 0.09PW, leading to an offset of the southward shift of the global ITCZ by 0.5°. Regionally the developed PMOC does not affect the southward movement of the Atlantic ITCZ much since the latter is dominated by the collapsed AMOC that induces the change of Atlantic MHT. In contrast, the PMOC-induced northward heat transport largely abates the hemispheric temperature contrast in the tropical Pacific and reduces the southward ITCZ shift by as much as 5° in the eastern Pacific.
KeywordsPMOC AMOC ITCZ Meridional heat transport Last deglaciation Bering Strait
WL is supported by NSF AGS-1249145. A portion of this study was supported by the Regional and Global Climate Modelling Program (RGCM) of the U.S. Department of Energy’s Office of Science (BER), Cooperative Agreement No. DE-FC02-97ER62402. This research used computing resources of the Climate Simulation Laboratory at the National Center for Atmospheric Research (NCAR), which is sponsored by the National Science Foundation; the National Energy Research Scientific Computing Center which are both supported by the Office of Science of the US Department of Energy. The National Center for Atmospheric Research is sponsored by the National Science Foundation.
- Ayliffe LK, Gagan MK, Zhao J-X, Drysdale RN, Hellstrom JC, Hantoro WS, Griffiths ML, Scott-Gagan H, Pierre ES, Cowley JA, Suwargadi BW (2013) Rapid interhemispheric climate links via the Australasian monsoon during the last deglaciation. Nat Commun 4. doi: 10.1038/ncomms3908
- Escobar J, Hodell DA, Brenner M, Curtis JH, Gilli A, Müller AD, Anselmetti FS, Ariztegui D, Grzesik DA, Pérez L, Schwalb A, Guilderson TJ (2012) A ~ 43-ka record of paleoenvironmental change in the Central American lowlands inferred from stable isotopes of lacustrine ostracods. Quat Sci Rev 37:92–104CrossRefGoogle Scholar
- He F (2011) Simulating transient climate evolution of the last deglaciation with CCSM3. Ph.D thesis, 171 pp., University of Wisconsin-MadisonGoogle Scholar
- Hu A, Meehl GA, Han W, Abe-Ouchi A, Morrill C, Okazaki Y, Chikamoto MO (2012a) The Pacific-Atlantic seesaw and the bering strait. Geophys Res Lett L03702, doi: 10.1029/2011GL050567
- Hu A, Meehl GA, Han W, Timmermann A, Otto-Bliesner B, Liu Z, Washington WM, Large W, Abe-Ouchi A, Kimoto M, Lambeck K, Wu B (2012b) Role of the bering strait on the hysteresis of the ocean conveyor belt circulation and glacial climate stability. Proc Natl Acad Sci 109:6417–6422. doi: 10.1073/pnas.1116014109 CrossRefGoogle Scholar
- Timmermann A, Krebs U, Justino F, Goosse H, Ivanochko T (2005) Mechanisms for millennial-scale global synchronization during the last glacial period. Paleoceanography 20: PA4008, doi: 10.1029/2004PA001090
- Yang H, Dai H (2014) Effect of wind forcing on the meridional heat transport in a coupled climate model: equilibrium response. Clim Dyn. doi: 10.1007/s00382-014-2393-0
- Yang H, Wang Y, Liu Z (2013) A modelling study of the Bjerknes compensation in the meridional heat transport in a freshening ocean. Tellus A 65: 18480. doi: 10.3402/tellusa.v65i0.18480