Mid-Holocene NAO: A PMIP2 model intercomparison

R. Gladstone (1) , I. Ross (1) , P.J. Valdes (1) , A. Abe-Ouchi (2) , P. Braconnot (3, 4) , S. Brewer (5) , M. Kageyama (3, 6) , A. Kitoh (7) , A. Legrande (8) , O. Marti (3, 4) , R. Ohgaito (9) , B. Otto-Bliesner (10) , W. R. Peltier (11) , G. Vettoretti (11)

1 School of Geographical Sciences [Bristol]
2 CCSR - Center for Climate System Research [Kashiwa]
3 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
4 MERMAID - Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics
5 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
6 CLIM - Modélisation du climat
7 MRI - Meteorological Research Institute [Tsukuba]
8 GISS - NASA Goddard Institute for Space Studies
9 JAMSTEC - Japan Agency for Marine-Earth Science and Technology
10 NCAR - National Center for Atmospheric Research [Boulder]
11 Department of Physics [Toronto]

The mid‐Holocene (6000 years before present) North Atlantic Oscillation (NAO) from nine models in the Paleoclimate Modeling Intercomparison Project Phase 2 is studied, primarily through principal component analysis of winter time North Atlantic sea level pressure (SLP). Modeled mid‐Holocene NAO and mean SLP show small changes compared to pre‐industrial control runs, with a shift in mean state towards a more positive NAO regime for three of the models. Modeled NAO variability shows little change, with a small increase for some models in the fraction of time spent in the NAO‐negative phase during the mid‐Holocene. Proxy based reconstructions of the NAO indicate a more positive NAO regime compared to present day during the mid‐ Holocene. We hypothesise that there was a small NAO+ like shift in mean state during the mid‐Holocene.

Domaines: Climatologie

R. Gladstone, I. Ross, P.J. Valdes, A. Abe-Ouchi, P. Braconnot, et al.. Mid-Holocene NAO: A PMIP2 model intercomparison. Geophysical Research Letters, 2005, 32 (16), ⟨10.1029/2005GL023596⟩. ⟨hal-02931809⟩