Carbon Release from Melting Arctic Permafrost on the North Slope, AK: 12CO2 and 13CO2 Concentrations and Fluxes, and Their Relationship to Methane and Methane Isotope Concentrations Measured in August 2013

Abstract:

One of the most important uncertainties in climate change is the positive feedback mechanism associated with the melting Arctic. As the Arctic permafrost destabilizes, labile carbon stored in the permafrost is subject to respiration and methanogenesis, producing greenhouse gases CO₂ and CH₄. Understanding the timing and rate of this release is paramount to our long-term understanding of the global climate structure, yet the remote location of the North Slope logistically precludes widespread tower measurements, necessitating airborne measurements. Presented are ¹²C and ¹³C CO₂ concentration flux measurements taken via an aircraft at a height of 10-30m during mid to late August 2013 from the north slope of Alaska. The data show different regimes for CO₂ vs δ-¹³C over regions within a roughly 100km box, indicating heterogenous landscape with differing dominant biological processes. The data are compared to CH₄ measurements that were taken simultaneously, showing highly varying concentrations of CH₄ with several different archetypical relationships to the total CO₂ regimes. The relationship between CO₂, δ-¹³C CO₂, and CH₄ concentrations provide further insight into the biological processes occurring in the melting Arctic permafrost. The data show that the dominant uptake and emission processes change by time of day and location. While the CO₂ and isotopologue data alone indicates whether a region is dominant in respiration or photosynthesis, combining the data with CH₄ measurements provides insight into the provenance of the CH₄ as well as methanogenic biological pathways active on the North Slope, while mass balance between CH₄, CO₂ or δ-¹³C CO² determines whether the methane signature is from methanogenesis, natural hydrocarbon seeps, or methane flaring. The data show few if any cases for which increases in methane concentrations are accompanied by a deviation in CO₂ or δ-¹³C CO² that would indicate incomplete methane flaring or natural seeps.