Evolution of the seasonal temperature cycle in a transient Holocene simulation: orbital forcing and sea-ice 1Max Planck Institute for Meteorology, Hamburg, Germany
08 Nov 2011
2International Max Planck Research School for Earth System Modelling, Hamburg, Germany
Received: 19 January 2011 – Published in Clim. Past Discuss.: 03 February 2011 Abstract. Changes in the Earth's orbit lead to changes in the seasonal and meridional
distribution of insolation. We quantify the influence of orbitally induced
changes on the seasonal temperature cycle in a transient simulation of the
last 6000 years – from the mid-Holocene to today – using a coupled
atmosphere-ocean general circulation model (ECHAM5/MPI-OM) including a land
surface model (JSBACH).
Revised: 14 September 2011 – Accepted: 28 September 2011 – Published: 08 November 2011
The seasonal temperature cycle responds directly to the insolation changes
almost everywhere. In the Northern Hemisphere, its amplitude decreases
according to an increase in winter insolation and a decrease in summer
insolation. In the Southern Hemisphere, the opposite is true.
Over the Arctic Ocean, decreasing summer insolation leads to an increase in
sea-ice cover. The insulating effect of sea ice between the ocean and the
atmosphere leads to decreasing heat flux and favors more "continental"
conditions over the Arctic Ocean in winter, resulting in strongly decreasing
temperatures. Consequently, there are two competing effects: the direct
response to insolation changes and a sea-ice insulation effect. The sea-ice
insulation effect is stronger, and thus an increase in the amplitude of the
seasonal temperature cycle over the Arctic Ocean occurs. This increase is
strongest over the Barents Shelf and influences the temperature response over
We compare our modeled seasonal temperatures over Europe to paleo
reconstructions. We find better agreements in winter temperatures than in
summer temperatures and better agreements in northern Europe than in southern
Europe, since the model does not reproduce the southern European Holocene
summer cooling inferred from the paleo reconstructions. The temperature
reconstructions for northern Europe support the notion of the influence of
the sea-ice insulation effect on the evolution of the seasonal temperature cycle.
Citation: Fischer, N. and Jungclaus, J. H.: Evolution of the seasonal temperature cycle in a transient Holocene simulation: orbital forcing and sea-ice, Clim. Past, 7, 1139-1148, doi:10.5194/cp-7-1139-2011, 2011.