Role of high-flow extremes in aquatic carbon export from peatlands

Peatland streams have repeatedly been shown to be highly supersaturated in gaseous carbon and export significant loads of both dissolved (DOC) and particulate (POC) organic carbon. Previous studies have shown that aquatic carbon export is strongly bias towards high flow events, which may become more frequent under predicted climate change scenarios. However, due to technical limitations and the lack of high flow representation in many regular spot sampling regimes, our understanding of high flow concentration dynamics is limited. Here we bring together 2 separate analyses of (i) the role of high-flow ‘extremes’ on DOC export based on long term (1993-2007) weekly spot samples across 7 UK upland streams, and (ii) stormflow CO2 dynamics across 5 headwater streams (UK, Sweden, Finland and Canada) using continuous, in-situ CO2 sensors. Catchment weighted DOC exports from the 3 peatland streams included in analysis (i) ranged from 16.9 to 28.0 g C m-2. Results showed 38.4%-44.9% of this DOC was exported during ‘extreme’ highs, which represented only 5% of time and 38.4%-40.6% of runoff. Although DOC export was greater from peatland streams, the proportion exported during ‘extreme’ events was similar across all 7 catchments. A comparison between the effects of storm intensity and duration on annual DOC export, and a seasonal breakdown of storm contributions, will also be presented. As well as quantifying the downstream export of CO2 during storm events (6%-33% of total CO2 export in 5% time), analysis (ii) will also consider high-resolution concentration responses across individual storms.