Climate and the terrestrial biosphere: A numerical investigation of global environmental change

This thesis presents a set of numerical investigations of the interactions between the climate system and the terrestrial biosphere. The primary result of this work is the development of a simulation model of the terrestrial biosphere, DEMETER, which describes the terrestrial biosphere from both a structural (potential vegetation) and functional (primary productivity and carbon storage) perspective. Chapters 3 and 4 present the application of the DEMETER model to the natural, steady-state terrestrial biosphere associated with the modern climate. Chapter 3 emphasizes the construction and validation of the potential vegetation and primary productivity models, while Chapter 4 is primarily concerned with the terrestrial carbon model.; To explore the sensitivity of the terrestrial biosphere to changes in climate, DEMETER is applied to a paleoclimatic scenario of the mid-Holocene (6,000 years before present). In order to describe the climate of the mid-Holocene, a global climate model is altered to reflect the changes in earth's orbital parameters (the date of perihelion, tilt of rotational axis and orbital eccentricity) that are appropriate for the mid-Holocene. The results of these numerical experiments are presented in Chapter 5.; In Chapter 6, a global climate model is used to investigate the effects of changing boreal forest cover on the simulation of paleoclimates. The extent of boreal forest plays a key role in determining the albedo of high-latitude regions; forest, replacing tundra, masks the highly reflective snow cover. Two simulations are performed: one with the boreal forest held fixed to its modern distribution and one with the boreal forest distribution changed to represent the mid-Holocene. In the high latitudes, shifting the boreal forest further north results in temperature increases of approximately 4{dollar}spcirc{dollar}C in winter and 2{dollar}spcirc{dollar}C in summer.