Articles | Volume 9, issue 2
Clim. Past, 9, 935–953, 2013

Special issue: Progress in paleoclimate modelling

Clim. Past, 9, 935–953, 2013

Research article 09 Apr 2013

Research article | 09 Apr 2013

Climatic impacts of fresh water hosing under Last Glacial Maximum conditions: a multi-model study

M. Kageyama1, U. Merkel2, B. Otto-Bliesner3, M. Prange2, A. Abe-Ouchi4, G. Lohmann5, R. Ohgaito6, D. M. Roche1, J. Singarayer7, D. Swingedouw1, and X Zhang5 M. Kageyama et al.
  • 1LSCE/IPSL – Laboratoire des Sciences du Climat et de l'Environnement, UMR8212, CEA-CNRS-UVSQ – CE Saclay, L'Orme des Merisiers, Bat. 701, 91191 Gif-sur-Yvette Cedex, France
  • 2MARUM – Center for Marine Environmental Sciences, University of Bremen, Klagenfurter Strasse, 28334 Bremen, Germany
  • 3NCAR, National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, Colorado 80305, USA
  • 4AORI, Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8568, Japan
  • 5Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bussestr. 24, 27570 Bremerhaven, Germany
  • 6Japan Agency for Marine-Earth Science and Technology, Showa-machi 3173-25, Kanazawa, Yokohama, 236-0001, Japan
  • 7Department of Geographical Sciences, University of Bristol, University Road Bristol, BS8 1SS, UK

Abstract. Fresh water hosing simulations, in which a fresh water flux is imposed in the North Atlantic to force fluctuations of the Atlantic Meridional Overturning Circulation, have been routinely performed, first to study the climatic signature of different states of this circulation, then, under present or future conditions, to investigate the potential impact of a partial melting of the Greenland ice sheet. The most compelling examples of climatic changes potentially related to AMOC abrupt variations, however, are found in high resolution palaeo-records from around the globe for the last glacial period. To study those more specifically, more and more fresh water hosing experiments have been performed under glacial conditions in the recent years. Here we compare an ensemble constituted by 11 such simulations run with 6 different climate models. All simulations follow a slightly different design, but are sufficiently close in their design to be compared. They all study the impact of a fresh water hosing imposed in the extra-tropical North Atlantic. Common features in the model responses to hosing are the cooling over the North Atlantic, extending along the sub-tropical gyre in the tropical North Atlantic, the southward shift of the Atlantic ITCZ and the weakening of the African and Indian monsoons. On the other hand, the expression of the bipolar see-saw, i.e., warming in the Southern Hemisphere, differs from model to model, with some restricting it to the South Atlantic and specific regions of the southern ocean while others simulate a widespread southern ocean warming. The relationships between the features common to most models, i.e., climate changes over the north and tropical Atlantic, African and Asian monsoon regions, are further quantified. These suggest a tight correlation between the temperature and precipitation changes over the extra-tropical North Atlantic, but different pathways for the teleconnections between the AMOC/North Atlantic region and the African and Indian monsoon regions.