ICE CORE RECORD ANALYSIS OF YOUNGER DRYAS-PREBOREAL TRANSITION USING ACETYLENE AND δ13C OF ATMOSPHERIC METHANE

The Younger Dryas-Preboreal Transition (YD-PB) marked a period of dramatic warming with numerous debates as to its causes and global effects. The changes to the global CH4 budget at this transition can be better understood through the use of stable carbon isotopes of CH4 relative to a standard (δ13C-CH4) to partition sources. Incorporating atmospheric acetylene concentrations, a byproduct of biomass burning with no other natural sources, allow us to better constrain fire emissions. Using C13 methane isotope and acetylene data from ice core measurements, a global picture of emissions from wetlands, biomass burning, and C3/C4 plant ratios was constructed. By splitting biomass burning into C3 and C4 fuel sources, it was possible to determine what floral ratio was necessary to match the methane isotope depletion throughout the warming event.

A slight dip and subsequent increase in δ13C-CH4 as temperatures rose suggest a fluctuation in a 13C-enriched CH4 source, specifically biomass burning, with a slight dip but then rapid increase alongside wetland emissions. Stable δ13C-CH4 values alongside an increase in total methane concentration seem to indicate a proportionate increase in both burning and wetland microbial sources. A further analysis of fire abundance from the acetylene record using known emission factors to distinguish between boreal and non-boreal burning points to a greater non-boreal wildfires both preceding and following the warming transition. Apportioning C3/C4 plant abundance seems to reveal little fluctuation. By studying changes associated with warming events such as the YD-PB we advance our understanding of potential universal effects from current global warming patterns.