Abstract
Abstract. The terrestrial biosphere is exposed to land-use and climate change, which not only affects vegetation dynamics but also changes land–atmosphere feedbacks. Specifically, changes in land cover affect biophysical feedbacks of water and energy, thereby contributing to climate change. In this study, we couple the well-established and comprehensively validated dynamic global vegetation model LPJmL5 (Lund–Potsdam–Jena managed Land) to the coupled climate model CM2Mc, the latter of which is based on the atmosphere model AM2 and the ocean model MOM5 (Modular Ocean Model 5), and name it CM2Mc-LPJmL. In CM2Mc, we replace the simple land-surface model LaD (Land Dynamics; where vegetation is static and prescribed) with LPJmL5, and we fully couple the water and energy cycles using the Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modeling System (FMS). Several improvements to LPJmL5 were implemented to allow a fully functional biophysical coupling. These include a sub-daily cycle for calculating energy and water fluxes, conductance of the soil evaporation and plant interception, canopy-layer humidity, and the surface energy balance in order to calculate the surface and canopy-layer temperature within LPJmL5. Exchanging LaD with LPJmL5 and, therefore, switching from a static and prescribed vegetation to a dynamic vegetation allows us to model important biospheric processes, including fire, mortality, permafrost, hydrological cycling and the impacts of managed land (crop growth and irrigation). Our results show that CM2Mc-LPJmL has similar temperature and precipitation biases to the original CM2Mc model with LaD. The performance of LPJmL5 in the coupled system compared to Earth observation data and to LPJmL offline simulation results is within acceptable error margins. The historical global mean temperature evolution of our model setup is within the range of CMIP5 (Coupled Model Intercomparison Project Phase 5) models. The comparison of model runs with and without land-use change shows a partially warmer and drier climate state across the global land surface. CM2Mc-LPJmL opens new opportunities to investigate important biophysical vegetation–climate feedbacks with a state-of-the-art and process-based dynamic vegetation model.
Highlights
Human activities, including land-use change and fossil fuel emissions, alter the climate and lead to profound changes in the components of the Earth system and their interactions
We introduce the biophysical coupling of water and energy fluxes resulting from vegetation dynamics as simulated by the adapted whole-ecosystem Lund– Potsdam–Jena managed Land (LPJmL5) dynamic global vegetation models (DGVMs) (Schaphoff et al, 2018b; Von Bloh et al, 2018) with the Geophysical Fluid Dynamics Laboratory (GFDL) coupled model CM2 (Milly and Shmakin, 2002) in a coarse-resolution setup called CM2Mc (Galbraith et al, 2011)
We couple LPJmL5 to the Climate Model 2 (Anderson et al, 2004, CM2) framework developed at the Geophysical Fluid Dynamics Laboratory (GFDL) including the Modular Ocean Model 5 (MOM5) in a lower-resolution configuration
Summary
Human activities, including land-use change and fossil fuel emissions, alter the climate and lead to profound changes in the components of the Earth system and their interactions. Increasing managed land for agriculture and other human activities reduces natural vegetation cover and changes how energy, water and carbon are exchanged between land, atmosphere and ocean. A functioning biosphere ensures stable energy, carbon and water cycles; the atmospheric composition and radiative forcing are maintained. While plants sequester carbon dioxide (CO2), they contribute to water cycling, albedo and roughness length, influencing the exchange of energy on multiple timescales
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