Observation-constrained sensitivities of Arctic methane emissions to warming

Area of Science:

• Atmospheric Chemistry
• Climate Science
• Arctic Research

Background:

• The sensitivity of Arctic methane emissions to climate warming is not well understood.
• Long-term atmospheric methane measurements reflect integrated Arctic fluxes and transport.

Purpose of the Study:

• To investigate the trend in pan-Arctic methane emissions and attribute the changes to specific sources.
• To quantify the sensitivity of natural methane emissions to climate warming.

Main Methods:

• Analysis of long-term atmospheric methane (CH4) measurements to determine the "autumn zero crossing date" trend.
• Utilizing atmospheric delta 13C-CH4 (δ13C_CH4) observations to differentiate between biogenic and wildfire emissions.
• Calculating the rate of increase in methane emissions and their sensitivity to warming.

Main Results:

• The "autumn zero crossing date" in the pan-Arctic is advancing, indicating earlier methane build-up.
• Natural Arctic methane emissions increased at a rate of 0.14 ± 0.04 Tg CH4 y^-2 (1998-2020).
• Attribution revealed 0.08 ± 0.02 Tg CH4 y^-2 from natural biogenic sources and 0.06 ± 0.02 Tg CH4 y^-2 from wildfires.
• Natural emissions show a warming sensitivity of 3.1 ± 0.9 Tg CH4 y^-1 per °C, higher than previous estimates.

Conclusions:

• Arctic methane emissions exhibit a significant positive feedback to climate warming.
• Natural biogenic sources and wildfires are key contributors to the observed increase in Arctic methane.
• The higher warming sensitivity suggests a potentially larger role for Arctic methane in future climate change.