Modeling Boreal Forest Expansion as a Driver of Accelerated Warming and Deglaciation following the Last Glacial Maximum

Abstract:

At the end of glacial periods, warmer temperatures induce ice sheet retreat, exposing the land surface for forest establishment. This transforms previously high albedo areas into dark, boreal needleleaf evergreen forest. The associated albedo change works to further increase surface temperatures locally, but it is unclear if the exaggerated warming from initial forest expansion and related vegetation-climate feedbacks could influence nearby near-surface climate enough to accelerate forest expansion beyond the orbitally-driven climate change. During the mid-Holocene, pollen records show rapid expansion of needleleaf evergreen forest in Alaska, west of the Laurentide Ice Sheet. Using a simplified reconstruction of this period, we use a global climate model to simulate the climate response to initial forest establishment, and subsequently apply the modified climate to nearby vegetation to determine if the initial forest expansion leads to more favorable growing conditions in the region. We isolate the effect of forest-driven forest expansion, examine various stages of forest succession, and explore the effect of improved plant functional type parameterization on the forest-climate feedback.