The fate of newly exposed carbon in the Arctic - controls on release to the atmosphere and transport to the ocean
EMSL Project ID
48039
Abstract
In the last 10 years the increasing heat of debate on how climate-change impacts to the Arctic will feed back to affect global temperatures has mirrored the arctic warming itself. Tremendous stores of organic carbon (C) frozen in permafrost soils have the potential to double the amount of C in the atmosphere on a timescale similar to human inputs because as soils warm and thaw the carbon they contain will be able to participate in the modern C cycle. As the permafrost thaws, water flow paths will be deeper and will bring previously frozen C into lakes and streams. But permafrost soils may not thaw quietly because melting ground ice is causing land-surface subsidence called “thermokarst failures” that release organic and mineral soil material to surface waters. Thus, both permafrost thawing and thermokarst failures will increase the amount of previously frozen dissolved organic matter (DOM) moving from soils into surface waters where the DOM can be exposed to sunlight. We found that photochemical reactions of permafrost DOM released from thermokarst failures produced CO2 and partially oxidized DOM that was readily respired by bacteria to CO2, and that this permafrost carbon was more susceptible to conversion to CO2 by sunlight and bacteria than expected based on our current understanding of the molecular features of DOM that control its susceptibility to photodegradation. Predictions of DOM degradation are based largely on bulk chemical characteristics, which fail to explain the high susceptibility of permafrost DOM to undergo degradation by sunlight and bacteria. This illustrates that we need to move beyond relying only on bulk characteristics to make predictions on the fate of carbon in permafrost soils. Thus, our objective is to use ultra-high resolution and molecular characterization of DOM compounds concurrent with field degradation experiments to obtain a predictive understanding of the relationship between DOM chemistry and its fate. We propose to use the high resolution mass spectrometry and NMR capabilities at EMSL which will provide a semi-quantitative assessment of the molecular composition of DOM. High resolution mass spectrometry provides the unique molecular formulas for components within the DOM assemblage, and solid state 13C-NMR will be used to evaluate shifts in major functional group distributions on a subset of isolated DOM. Using these techniques together will help constrain the chemical composition of DOM and how that composition relates to photochemical and biological reactivity. We will analyze a subset of key samples from a gradient of land-surface age and geochemical factors that represent arctic landscapes and influence the chemical composition and reactivity of soil carbon to demonstrate that our questions and approach will help frame a better answer of what role the Arctic will play in future climate change. Summer 2013 is our last chance to collect these samples as part of our NSF-funded study on the reactivity of permafrost DOM, and thus this analysis is a critical opportunity to characterize DOM at EMSL from samples that will have been analyzed for measures of photochemical and biological susceptibility to degradation to CO2 in the field.
Project Details
Project type
Limited Scope
Start Date
2013-08-12
End Date
2013-10-12
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members
Related Publications
Rose M. Cory, Collin P. Ward. 2020. "Assessing the prevalence, products, and pathways of dissolved organic matter partial photo-oxidation in arctic surface waters." Environmental Science: Processes & Impacts 22 (5):1214-1223. https://doi.org/10.1039/C9EM00504H