Clim. Past Discuss., 7, 2803-2833, 2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
Vegetation-climate interactions in the warm mid-Cretaceous
J. Zhou1, C. J. Poulsen1, N. Rosenbloom2, C. Shields2, and B. Briegleb2
1Department of Earth and Environmental Sciences, University of Michigan, USA
2National Center for Atmospheric Research, Boulder, Colorado, USA

Abstract. Vegetation-climate interactions are thought to have amplified polar warmth during past warm periods. Here, we explore the vegetation-climate interactions in the mid- Cretaceous using a fully coupled ocean-atmosphere general circulation model with a dynamic vegetation component. We run simulations with 1×, 10× and 16× preindustrial atmospheric CO2. Results show that forests expand from mid-latitudes to high latitudes as CO2 increases from 1× to 10× and 16×, mainly due to the CO2- induced warming. This expansion of mid-to-high latitude forests are largely supported by the distribution of mid-Cretaceous fossil woods and coal deposits. Globally, the presence of vegetation increases mean annual temperature and precipitation by 0.9 °C and 0.11mm day−1 relative to bare ground. High-latitude warming induced by the presence of vegetation (∼1.9 °C) is less than half of that reported in previous studies. The weaker warming here is mainly due to less pronounced albedo feedbacks, and to a less extent, reduced poleward heat transport via weakening of the meridional overturning circulation. Our results suggest that other mechanisms in addition to high atmospheric CO2 and high-latitude vegetation are required to maintain the polar warmth.

Citation: Zhou, J., Poulsen, C. J., Rosenbloom, N., Shields, C., and Briegleb, B.: Vegetation-climate interactions in the warm mid-Cretaceous, Clim. Past Discuss., 7, 2803-2833, doi:10.5194/cpd-7-2803-2011, 2011.
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