Articles | Volume 3, issue 2
Clim. Past, 3, 279–296, 2007

Special issue: Modelling late Quaternary climate

Clim. Past, 3, 279–296, 2007

  04 Jun 2007

04 Jun 2007

Results of PMIP2 coupled simulations of the Mid-Holocene and Last Glacial Maximum – Part 2: feedbacks with emphasis on the location of the ITCZ and mid- and high latitudes heat budget

P. Braconnot1, B. Otto-Bliesner2, S. Harrison3, S. Joussaume1, J.-Y. Peterchmitt1, A. Abe-Ouchi4, M. Crucifix5,6, E. Driesschaert6, Th. Fichefet6, C. D. Hewitt5, M. Kageyama1, A. Kitoh7, M.-F. Loutre6, O. Marti1, U. Merkel8, G. Ramstein1, P. Valdes3, L. Weber9, Y. Yu10, and Y. Zhao3 P. Braconnot et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, Unité mixte CEA-CNRS-UVSQ, Orme des Merisiers, bât. 712, 91191 Gif-sur-Yvette Cedex, France
  • 2National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, Colorado, USA
  • 3School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK
  • 4Center for Climate System Research, The University of Tokyo, Japan 277-8568 and FRCGC/JAMSTEC, Yokohama 236-0001, Japan
  • 5Met Office Hadley Centre, Fitzroy Road, Exeter EX1 3PB, UK
  • 6Université Catholique de Louvain, Institut d'Astronomie et de Géophysique Georges Lemaître, B-1348 Louvain-la-Neuve, Belgium
  • 7Meteorological Research Institute, Tsukuba, Ibaraki 305-0052, Japan
  • 8Universität Bremen, FB5 Geosciences, Geosystem modelling, P.O. Box 330 440, 28334 Bremen, Germany
  • 9Royal Netherlands Meteorological Institute, P.O.~Box 201, 3730 AE De Bilt, The Netherlands
  • 10LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, P.O. Box 9804, Beijing 100029, P. R. China

Abstract. A set of coupled ocean-atmosphere(-vegetation) simulations using state of the art climate models is now available for the Last Glacial Maximum (LGM) and the Mid-Holocene (MH) through the second phase of the Paleoclimate Modeling Intercomparison Project (PMIP2). Here we quantify the latitudinal shift of the location of the Intertropical Convergence Zone (ITCZ) in the tropical regions during boreal summer and the change in precipitation in the northern part of the ITCZ. For both periods the shift is more pronounced over the continents and East Asia. The maritime continent is the region where the largest spread is found between models. We also clearly establish that the larger the increase in the meridional temperature gradient in the tropical Atlantic during summer at the MH, the larger the change in precipitation over West Africa. The vegetation feedback is however not as large as found in previous studies, probably due to model differences in the control simulation. Finally, we show that the feedback from snow and sea-ice at mid and high latitudes contributes for half of the cooling in the Northern Hemisphere for the LGM, with the remaining being achieved by the reduced CO2 and water vapour in the atmosphere. For the MH the snow and albedo feedbacks strengthen the spring cooling and enhance the boreal summer warming, whereas water vapour reinforces the late summer warming. These feedbacks are modest in the Southern Hemisphere. For the LGM most of the surface cooling is due to CO2 and water vapour.