Modelling the impacts of future enhanced winter warming events on
subarctic ecosystems using LPJ-GUESS
Winter warming events (WWEs) are short-lasting events of unusually warm
weather, occasionally combined with rainfall, which can cause severe
ecosystem impacts by altering ground temperatures and water fluxes.
These impacts are generally overlooked in large-scale ecosystem models.
The frequency and intensity of WWEs will likely increase further in the
future. We used an ecosystem model, LPJ-GUESS, to investigate the
responses of four subarctic ecosystems to different levels of predicted
WWEs, and identify model gaps hindering accurate estimates of these
responses. In response to WWEs, the model simulated substantial ground
cooling (up to 2 °C in winter) in contrast to the observed warming,
leading to changes in biogeochemical fluxes often comparable in
magnitude to those from altered winter climatologies. The mismatch
between the modelled and the observed ground temperature changes may be
due to the 1) lacking surface energy balance, 2) daily timestep, and 3)
simplistic water retention scheme in LPJ-GUESS.