Effects of orbital forcing on atmosphere and ocean heat transports in Holocene and Eemian climate simulations with a comprehensive Earth system model 1Max Planck Institute for Meteorology, Hamburg, Germany
2International Max Planck Research School for Earth System Modelling, Hamburg, Germany
Received: 22 September 2009 – Published in Clim. Past Discuss.: 13 October 2009 Abstract. Orbital forcing does not only exert direct insolation effects, but also
alters climate indirectly through feedback mechanisms that modify atmosphere
and ocean dynamics and meridional heat and moisture transfers. We investigate
the regional effects of these changes by detailed analysis of atmosphere and
ocean circulation and heat transports in a coupled atmosphere-ocean-sea
ice-biosphere general circulation model (ECHAM5/JSBACH/MPI-OM). We perform
long term quasi equilibrium simulations under pre-industrial, mid-Holocene
(6000 years before present – yBP), and Eemian (125 000 yBP) orbital
boundary conditions. Compared to pre-industrial climate, Eemian and Holocene
temperatures show generally warmer conditions at higher and cooler conditions
at lower latitudes. Changes in sea-ice cover, ocean heat transports, and
atmospheric circulation patterns lead to pronounced regional heterogeneity.
Over Europe, the warming is most pronounced over the north-eastern part in
accordance with recent reconstructions for the Holocene. We attribute this
warming to enhanced ocean circulation in the Nordic Seas and enhanced
ocean-atmosphere heat flux over the Barents Shelf in conduction with retreat
of sea ice and intensified winter storm tracks over northern Europe.
Revised: 12 March 2010 – Accepted: 17 March 2010 – Published: 25 March 2010
Citation: Fischer, N. and Jungclaus, J. H.: Effects of orbital forcing on atmosphere and ocean heat transports in Holocene and Eemian climate simulations with a comprehensive Earth system model, Clim. Past, 6, 155-168, doi:10.5194/cp-6-155-2010, 2010.