Abstract. The importance of northern peatlands in the global carbon cycle has been
recognized, especially for long-term changes. Yet, the complex interactions
between climate and peatland hydrology, carbon storage, and area dynamics
make it challenging to represent these systems in land surface models. This
study describes how peatlands are included as an independent sub-grid
hydrological soil unit (HSU) in the ORCHIDEE-MICT land surface model. The
peatland soil column in this tile is characterized by multilayered vertical
water and carbon transport and peat-specific hydrological properties. The
cost-efficient version of TOPMODEL and the scheme of peatland initiation and
development from the DYPTOP model are implemented and adjusted to simulate
spatial and temporal dynamics of peatland. The model is tested across a
range of northern peatland sites and for gridded simulations over the
Northern Hemisphere (>30∘ N). Simulated northern
peatland area (3.9 million km2), peat carbon stock (463 Pg C), and peat
depth are generally consistent with observed estimates of peatland area (3.4–4.0 million km2), peat carbon (270–540 Pg C), and data compilations
of peat core depths. Our results show that both net primary production (NPP)
and heterotrophic respiration (HR) of northern peatlands increased over the
past century in response to CO2 and climate change. NPP increased more
rapidly than HR, and thus net ecosystem production (NEP) exhibited a
positive trend, contributing a cumulative carbon storage of 11.13 Pg C since
1901, most of it being realized after the 1950s.
Modelling northern peatlands area and carbon dynamics since the Holocene with
the ORCHIDEE-PEAT land surface model (SVN r5488)
