Geoscientific Model Development Discussions www.geosci-model-dev-discuss.net 1991-9611 1991-962X 2 1 2009 10.5194/gmdd-2-507-2009 http://www.geosci-model-dev-discuss.net/2/507/2009/ http://www.geosci-model-dev-discuss.net/2/507/2009/gmdd-2-507-2009.html http://www.geosci-model-dev-discuss.net/2/507/2009/gmdd-2-507-2009.pdf 507 549 2009-05-14 Simulated pre-industrial climate in Bergen Climate Model (version 2): model description and large-scale circulation features O. H. Otterå oddho@nersc.no M. Bentsen I. Bethke N. G. Kvamstø Nansen Environmental and Remote Sensing Center, Thormøhlensgt. 47, 5006 Bergen, Norway Bjerknes Centre for Climate Research, Allégt. 55, 5007 Bergen, Norway Geophysical Institute, University of Bergen, Allégt. 70, 5007 Bergen, Norway The Bergen Climate Model (BCM) is a fully-coupled atmosphere-ocean-sea-ice model that provides state-of-the-art computer simulations of the Earth's past, present, and future climate. Here, a pre-industrial multi-century simulation with an updated version of BCM is described and compared to observational data. The model is run without any form of flux adjustments and is stable for several centuries. The simulated climate reproduces the general large scale circulation in the atmosphere reasonably well, except for a positive bias in the high latitude sea level pressures distribution. Also, by introducing an updated turbulence scheme in the atmosphere model a persistent cold bias has been eliminated. For the ocean part, the model drifts in sea surface temperatures and salinities are considerably reduced compared to earlier versions of BCM. Improved conservation properties in the ocean have contributed to this. Furthermore, by choosing a reference pressure at 2000 m and including thermobaric effects in the ocean model, a more realistic meridional overturning circulation is simulated in the Atlantic Ocean. 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