Closing the Winter Gap—Year-Round Measurements of Soil CO2 Emission Sources in Arctic Tundra
Abstract
Non-growing season CO2 emissions from Arctic tundra remain a major uncertainty in forecasting climate change consequences of permafrost thaw. We present the first time series of soil and microbial CO2 emissions from a graminoid tundra based on year-round in situ measurements of the radiocarbon content of soil CO2 (Δ14CO2) and of bulk soil C (Δ14C), microbial activity, and temperature. Combining these data with land-atmosphere CO2 exchange allows estimates of the proportion and mean age of microbial CO2 emissions year-round. We observe a seasonal shift in emission sources from fresh carbon during the growing season (August Δ14CO2 = 74 ± 4.7‰, 37% ± 3.4% microbial, mean ± se) to increasingly older soil carbon in fall and winter (March Δ14CO2 = 22 ± 1.3‰, 47% ± 8% microbial). Thus, rising soil temperatures and emissions during fall and winter are depleting aged soil carbon pools in the active layer and thawing permafrost and further accelerating climate change.
- Publication:
-
Geophysical Research Letters
- Pub Date:
- March 2022
- DOI:
- 10.1029/2021GL097347
- Bibcode:
- 2022GeoRL..4997347P
- Keywords:
-
- carbon flux;
- permafrost;
- radiocarbon;
- respiration;
- winter;
- vulnerability