Peatland area and carbon over the past 21 000 years – a global process based model investigation

Abstract

<jats:p>Abstract. Peatlands are an essential part of the terrestrial carbon cycle and the climate system. Understanding their history is key to understand future and past land-atmosphere carbon fluxes. We performed transient simulations over the past 22 000 years with a dynamic global peat and vegetation model forced by Earth System Model climate output, thereby complementing data-based reconstructions for peatlands. Our novel results demonstrate a highly dynamic evolution with concomitant gains and losses of active peatland areas. Modelled gross area changes exceed net changes several fold, while net peat area increases by 60 % over the deglaciation. Peatlands expand to higher northern latitudes in response to warmer and wetter conditions and retreating ice sheets and are partly lost in mid-latitude regions. In the tropics peatlands are partly lost due to flooding of continental shelves and regained by non-linear interactions between temperature, precipitation and CO2. Large north-south shifts of tropical peatlands are driven by shifts in the position of the Inter Tropical Convergence Zone associated with the abrupt climate events of the glacial termination. Time slice simulations for the Last Glacial Maximum (LGM) demonstrate large uncertainties in modelled peatland extent (global range: 1.5 to 3.4 Mkm2) stemming from uncertainties in climate forcing. Net uptake of atmospheric CO2 through peatlands, modelled at 350 GtC since the LGM, includes decay from former peatlands. Carbon uptake would be misestimated, in particular during periods of rapid climate change and subsequent peatland area shifts, when considering only changes in the area of currently active peatlands. Our study highlights the dynamic nature of peatland distribution and calls for an improved understanding of former peatlands to better constrain peat carbon sources and sinks. </jats:p>

Expert assessment of future vulnerability of the global peatland carbon sink

“…Peatland C stocks and fluxes have yet to be incorporated into Earth System Models (ESMs), though they are beginning to be implemented in global terrestrial models [9][10] . As these models are moving towards the integration of permafrost dynamics, LULCC, and other disturbances such as fire, the absence of peatland C dynamics could lead to many problems in the next generation of models (Figure 1a).…”

The High-Elevation Peatlands of the Northern Andes, Colombia

“…Globally, peatlands are a major carbon stock, storing approximately one-third of the world’s soil carbon (450 Pg) in only 3% of the world’s continental area [ 19 , 20 ]. However, climate change and the changes in land use observed during the last 20 years have increased the vulnerability of peatlands to disturbances [ 21 , 22 , 23 , 24 ].…”

Distribution, nature and threats to soils of the Australian Alps: A review

“…2009; Gorham et al . 2012; Müller & Joos 2020). Peat soils store more SOC per ha than mineral soils, as they typically have higher carbon contents throughout the soil profile than their mineral counterparts.…”