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www.clim-past-discuss.net/7/809/2011/
doi:10.5194/cpd-7-809-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Strength of forest-albedo feedback in mid-Holocene climate simulations
1Max Planck Institute for Meteorology, Hamburg, Germany
2International Max Planck Research School on Earth System Modelling, Hamburg, Germany
3Meteorological Institute, University Hamburg, KlimaCampus, Germany
*now at: LSCE, Laboratoire des Sciences du Climat et l'Environnement, CEA-CNRS-UVSQ, UMR8212, Gif-Sur-Yvette, France
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 persumably 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.
We investigate this vegetation-climate interaction under mid-Holocene forcing with a comprehensive general circulation model (ECHAM5/JSBACH). We performed two sets of model simulations with either weak or strong reduction in surface albedo by snow-covered forest. The setup of simulations allowed us to calculate the pure contribution by the vegetation-climate interaction to the climate signal. Compared to the set with weak snow masking, the simulations with strong snow masking prevail a three times higher spring warming by 0.34 °C north of 60° N. The additional gain of forest is only 13%.
We show that the parameterisation of the albedo of snow leads to uncertainties in the temperature signal but does not explain the strong spring warming suggested by previous simulations. We rather suggest that studies with coarser resolved representation of vegetation than in ECHAM5/JSBACH overestimated the increase in forest at the mid-Holocene and thus the strength of the vegetation climate.
Discussion Paper (PDF, 1500 KB) Interactive Discussion (Closed, 7 Comments) Final Revised Paper (CP)
Notice on Discussion StatusCitation: Otto, J., Raddatz, T., and Claussen, M.: Strength of forest-albedo feedback in mid-Holocene climate simulations, Clim. Past Discuss., 7, 809-840, doi:10.5194/cpd-7-809-2011, 2011. Bibtex EndNote Reference Manager XML
