Dissolved Organic Matter Composition in Waters Draining Permafrost Landscapes - a Circumpolar Synthesis
Abstract
The flux of dissolved organic matter (DOM) from terrestrial to freshwater aquatic and marine ecosystems represents an important component of the carbon (C) balance in Arctic and sub-Arctic watersheds. Recent warming and permafrost thaw have altered DOM fluxes in rivers, both through the release of old permafrost C and by shifting hydrologic transport and cycling of DOM in soils. The fate of DOM along the soil-river-ocean continuum is closely linked to its chemical composition, which governs photochemical and microbially mediated transformations and therefore C-cycle feedbacks to the atmosphere. Given the complexity of these issues, large uncertainties exist with respect to DOM fate under future warming and permafrost thaw. To better constrain DOM turnover and fate, we synthesized DOM composition data from 48 published studies and additional unpublished data from across the northern circumpolar permafrost region. Our database includes over 4000 water samples spanning different regions (North America, Eurasia), permafrost zones (continuous, discontinuous), site types (soils, rivers, lakes, ocean), and disturbances (i.e., thermokarst activity). DOM was characterized using a broad range of analytical approaches, including bulk dissolved organic carbon (DOC) and nitrogen concentrations, optical properties, chemical fractionation, and C isotopes (δ13C, Δ14C). Preliminary findings highlight broad spatial variation in DOM composition along the soil-to-ocean continuum, reflecting DOM processing as a function of transport time. DOC concentrations were highest in waters draining upland and peatland thermokarst features, but generally declined in larger downstream basins. While DOM age in ground ice and permafrost-thaw waters was old (> 10k y BP), DOM in streams and rivers was generally modern, likely reflecting the bio-lability and rapid turnover of permafrost C, as well as dilution of old DOM by young carbon inputs moving down the hydrologic network. We will present further analyses in the goal of identifying relationships between DOM composition and bio-lability across sites to generating robust decay functions for earth system modelers.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B42D..06O
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0486 Soils/pedology;
- BIOGEOSCIENCESDE: 0702 Permafrost;
- CRYOSPHEREDE: 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE