Strength of forest-albedo feedback in mid-Holocene climate simulations 1Max Planck Institute for Meteorology, Hamburg, Germany
28 Sep 2011
2International Max Planck Research School on Earth System Modelling, Hamburg, Germany
3Meteorological Institute, University Hamburg, KlimaCampus, Hamburg, Germany
*now at: LSCE, Laboratoire des Sciences du Climat et l'Environnement, UMR8212 – CEA-CNRS-UVSQ, Gif-Sur-Yvette, France
Received: 04 February 2011 – Published in Clim. Past Discuss.: 01 March 2011 Abstract. Reconstructions of the mid-Holocene climate, 6000 years before present,
suggest that spring temperatures were higher at high northern latitudes
compared to the pre-industrial period. A positive feedback between expansion
of forest and climate presumably contributed to this warming. In the presence
of snow, forests have a lower albedo than grass land. Therefore, the expansion
of forest likely favoured a warming in spring, counteracting the lower
insolation at the mid-Holocene.
Revised: 01 August 2011 – Accepted: 06 September 2011 – Published: 28 September 2011
We investigate the sensitivity of the vegetation-atmosphere interaction under
mid-Holocene orbital forcing with respect to the strength of the
forest-albedo feedback by using a comprehensive coupled atmosphere-vegetation
model (ECHAM5/JSBACH). We perform two sets of model
simulations: a first set of simulations with a relatively weak reduction of
albedo of snow by forest; and a second set of simulations with a relatively
strong reduction of the albedo of snow by forest.
We show that the parameterisation of the albedo of snow leads to
uncertainties in the temperature signal. Compared to the set with weak snow
masking, the simulations with strong snow masking reveal a spring warming
that is three times higher, by 0.34 °C north of 60° N. This
warming is related to a forest expansion of only 13%.
Citation: Otto, J., Raddatz, T., and Claussen, M.: Strength of forest-albedo feedback in mid-Holocene climate simulations, Clim. Past, 7, 1027-1039, doi:10.5194/cp-7-1027-2011, 2011.