CM2Mc-LPJmL v1.0: biophysical coupling of a process-based dynamic vegetation model with managed land to a general circulation model

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.

Earth beyond six of nine planetary boundaries

“…For climate change, the Potsdam Earth Model (POEM) [( 85 ) and the Supplementary Materials] is forced by increased atmospheric carbon dioxide levels (350, 450, and 550 ppm), and land system change is forced with land-use patterns representing different extents of tropical, temperate, and boreal forest cover (see the Supplementary Materials). As some biological processes take centuries to approach a steady state, we investigate changes in both the short (1988–2100) and the long term (2100–2770).…”

“…To examine differing scenarios of transgression of land system and climate change boundaries, we use the POEM [( 85 ) and the Supplementary Materials], which links models of atmospheric and ocean circulation with models of the marine (BLING) ( 94 ) and terrestrial biosphere (LPJmL5) [( 95 ) and the Supplementary Materials]. We study scenarios where each of these two planetary boundary dimensions are either fixed at the value of the boundary, a value in the zone of increasing risk, or a value in the high-risk zone.…”

Climate tipping point interactions and cascades: a review

“…One example of asynchronous coupling is when the atmosphere evolves with fixed vegetation cover and eventually the latter is updated to the equilibrium conditions of the former (Foley et al, 1998). However, despite being less computationally expensive, feedback mechanisms and thus tipping phenomena and cascades are better represented when dynamical (synchronous) coupling is implemented (Drüke et al, 2021;Fisher et al, 2018;Fyke et al, 2018;Bonan et al, 2003).…”

The long-term impact of transgressing planetary boundaries on biophysical atmosphere-land interactions

“…POEM (in the configuration of CM2Mc-LPJmL, Drüke et al, 2021b) is an Earth system model that combines the atmosphere and ocean model CM2Mc (Galbraith et al, 2011), which has a coarse spatial resolution and hence is relatively fast, with the dynamic global vegetation model (DGVM) LPJmL version 5 (LPJmL5, Schaphoff et al, 2018b;Von Bloh et al, 2018). https://doi.org/10.5194/egusphere-2023-2133 Preprint.…”

“…In this study, we analyze the combined impact of crossing the planetary boundaries for climate change (CC) and land system change (LSC), by applying the Potsdam Earth model (POEM, Drüke et al, 2021b), which includes a process-based representation of the biosphere's response to climate change. In particular POEM's advanced vegetation model component LPJmL (Schaphoff et al, 2018b) is able to realistically account for important processes connected to plant productivity, phenology, and mortality.…”