Multivariate Climate Extremes and Their Impacts on Arctic Land–Atmosphere Carbon Exchange under Future Climate Change

Rapid warming of the Arctic is increasingly being linked to climate extremes such as heat waves, droughts, and wildfires, which are fundamentally altering the functioning of ecosystems, the dynamics of the carbon cycle, and the interactions between land and atmosphere in the Arctic. Increasing evidence suggests that high-latitude extreme events rarely occur in isolation but are frequently embedded within compound climate extremes. These multivariate events can strongly modify land surface states, through changes in soil moisture, vegetation structure, surface energy balance, and fire disturbance, and thereby influence carbon exchanges between the land and atmosphere. However, the extent to which compound climate extremes amplify or modulate Arctic carbon-cycle extremes in the future remains poorly constrained.

In this study, we investigate how compound climate extreme events shape the evolution of Arctic carbon-cycle extremes under future Arctic warming. Using large ensemble simulations with the Community Earth System Model version 2 (CESM2), which has demonstrated skill in representing Arctic climate processes, fire dynamics, and fire-weather interactions, we assess the evolution of extreme events in gross primary productivity, ecosystem respiration, and net ecosystem carbon balance throughout the 21st century. A multivariate statistical framework is applied to explicitly characterise compound extremes involving fire activity, heat waves, and droughts, and to qualify and quantify their combined impacts on land-atmosphere carbon flux variability in the Arctic. By linking compound climate drivers to ecosystem carbon responses, this work advances our understanding of how land surface conditions regulate extreme carbon-cycle behaviour in a rapidly changing Arctic.