Carbon emissions and radiative forcings from tundra wildfires in the Yukon-Kuskokwim River Delta, Alaska

• Main Authors: Moubarak, Michael, Sistla, Seeta, Potter, Stefano, Natali, Susan M., Rogers, Brendan M.
• Format: Text
• Language: English
• Published: 2022
• Subjects: Arctic; Yukon; Climate change; Kuskokwim; Tundra; Alaska
• Online Access: https://doi.org/10.5194/bg-2022-144; https://bg.copernicus.org/preprints/bg-2022-144/

Tundra environments are experiencing elevated levels of wildfire, and the frequency is expected to keep increasing due to accelerating climate change in the Arctic. Tundra wildfires can release globally significant amounts of greenhouse gasses that influence the Earth’s radiative balance. Here we develop a novel method for estimating carbon loss and the resulting radiative forcings of gaseous and aerosol emissions from 2015 tundra wildfires in the Yukon-Kuskokwim Delta (YKD), AK. We paired burn depth measurements using two vegetative reference points that survived the fire event — Sphagnum fuscum and Dicranum spp .— with measurements of local organic matter and soil carbon properties to estimate total ecosystem organic matter and carbon loss. We used remotely-sensed data of fire severity from Landsat 8 to scale our measured losses to the entire fire-affected area, with an estimated total loss of 2.04 Tg of organic matter and 0.91 Tg of carbon, and an average loss of 3.76 kg m -2 of organic matter and 1.68 kg m -2 of carbon in the 2015 YKD wildfires. To demonstrate the impact of these fires on Earth’s radiation budget, we developed a simple but comprehensive framework to estimate the radiative forcing from Arctic wildfires. We synthesized existing research on the lifetime and radiative forcings of gaseous and aerosol emissions of CO 2 , N 2 O, CH 4 , O 3 and its precursors, and fire aerosols. The model shows a net positive cumulative mean radiative forcing of 3.67 W m -2 using RCP 4.5 and 3.37 W m -2 using RCP 8.5 at 80 years post-fire, which was dominated by CO 2 emissions. Our results highlight the climate impact of tundra wildfires, which positively reinforce climate warming and increased fire frequency through the radiative forcings of their gaseous emissions.