Global peatland area and carbon dynamics in the near and long term future projected seamlessly from the LGM using a dynamic global vegetation model

Abstract:

Global peatlands are an essential part of the Earth system. They store a significant share of the global organic soil carbon. Most of this carbon was accumulated over the Holocene and peatlands continue to serve as carbon sinks to this day. Under climate change however, this might change. Peatlands might increase their sink in some regions and become sources in others^[1]. Increasing our knowledge about the possible future dynamics of peatlands thus is integral to better understand the resulting positive and negative feedbacks, which are still neglected by most climate models.

Here we present results from the LPX-Bern dynamic global vegetation model. A previously published transient simulation from the LGM to the present^[2] serves as the starting point to project into the future. For the slow-reacting system of peatlands, we thus explicitly capture the legacy of the transient evolution over 22,000 years.

For the projections, LPX is forced with climate output from 10 different CMIP6 models, chosen for optimal CMIP6 ensemble representation, and three scenarios ranging from low emission to high emission pathways. Climate is held constant for another 4000 years after 2100 CE or 2300 CE to determine the long term effects of climate change on peatlands. Simulations with constant present climate provide information about already committed changes. Differences between the ensemble members are used to estimate uncertainty. Factorial simulations allow for driver attribution.

With this, we provide an in-depth analysis of possible future global peatland dynamics and estimate the net feedback of these ecosystems.

^[1] Gallego-Sala et al. Latitudinal limits to the predicted increase of the peatland carbon sink with warming,Nat. Clim. Change, 8,907-913,2018

^[2] Müller, J. & Joos, F. Peatland area and carbon over the past 21 000 years – a global process based model investigation,Biogeosciences Disc.,in review,2020, https://www.biogeosciences-discuss.net/bg-2020-110/