The net GHG balance and budget of the permafrost region (2000-2020) from
ecosystem flux upscaling
Abstract
The northern permafrost region has been projected to shift from a net
sink to a net source of carbon under global warming. However, estimates
of the contemporary net greenhouse gas (GHG) balance and budgets of the
permafrost region remain highly uncertain. Here we construct the first
comprehensive bottom-up budgets of CO2, CH4, and N2O across the
terrestrial permafrost region using databases of more than 1000 in-situ
flux measurements and a land cover-based ecosystem flux upscaling
approach for the period 2000-2020. Estimates indicate that the
permafrost region emitted a mean annual flux of 0.36 (-620, 652) Tg
CO2-C y-1, 38 (21, 53) Tg CH4-C y-1, and 0.62 (0.03, 1.2) Tg N2O-N y-1
to the atmosphere throughout the period. While the region was a net
source of CH4 and N2O, the CO2 budget was near neutral with large
uncertainties. Terrestrial ecosystems remained a CO2 sink, but emissions
from fire disturbances and inland waters largely offset the sink in
vegetated ecosystems. Including lateral fluxes, the permafrost region
was a net source of C and N, releasing 136 (-517, 821) Tg C y-1 and 3.2
(1.9, 4.8) Tg N y-1. Large uncertainty ranges in these estimates point
to a need for further expansion of monitoring networks, continued data
synthesis efforts, and better integration of field observations, remote
sensing data, and ecosystem models to constrain the contemporary net GHG
budgets of the permafrost region and track their future trajectory.