Research project P4S/251/CRISP (Research action P4S)
Context
Arctic permafrost contains approximately 1,500 billion tons of organic carbon, equating to roughly half of the world's soil carbon stocks. Up to 70% of near-surface permafrost is projected to thaw by 2100. The resulting deepening of the active layer progressively exposes organic carbon previously locked by freezing temperatures, making them available for microbial decomposition and hydrological transport to rivers. Arctic rivers in the world’s northern hemisphere currently export 25–36 million tons of dissolved organic carbon (DOC) per year to the Arctic Ocean, but this figure is likely underestimated. Most monitoring programs shut down during autumn, cease entirely through winter and only restart late sprig, creating data gaps of 6 to 8 months. This is particularly problematic given that the shoulder seasons alone, spanning autumn freeze-up and spring ice break up, account for roughly 30% of annual DOC export. Furthermore, small catchments are underrepresented as they fall below satellite resolution and are excluded from most flux projections despite representing over 99% of Arctic river systems.
Another poorly understood factor is the formation of taliks. These patches of soil that remain unfrozen throughout winter may sustain hydrological connectivity and DOC export to rivers well beyond the typical thaw season. Their impact on carbon mobilisation remains largely unconstrained.
Objectives
CRISP pursues two complementary objectives:
The first objective is to quantify DOC export by rivers from late autumn through to early spring. By deploying autonomous seismic instruments at the Panguingue Creek catchment in Interior Alaska (USA), CRISP will provide continuous discharge record through the full winter season at a small permafrost watershed, combined with high-resolution geochemical characterisation of DOC sources.
The second objective is to understand the timing and mechanisms by which taliks enhance DOC export from soil to rivers. Seismic nodes buried in the ground at the Eight Mile Lake research site will track freeze-thaw transitions throughout winter and spring, and soil pore water sampled across seasons will reveal how talik formation alters the pathways and timing of carbon mobilisation.
Methodology
CRISP combines seismological and geochemical approaches. Seismic nodes installed for a year along the Panguingue Creek will record continuous ambient seismic noise generated by antropogenic and natural sources. Probabilistic Power Spectral Density (PPSD) data analysis of seismic noise will provide estimations of river discharge throughout the whole year, including quiet frozen winter conditions and violent spring freshet. River water samples will be analysed for major and trace elements, DOC, strontium isotopes (87Sr/86Sr), and water isotopes (δ2H and δ18O) to identify and quantify the sources contributing to riverine DOC.
In soils, seismic nodes buried around the Eight Mile Lake will monitor varying subsurface conditions for over a year across a gradient a permafrost degradation, from relatively shallow permafrost table down to depths where talik persists. Horizontal-to-Vertical Spectral Ratio (HVSR) analysis of ambient noise will track changes in seismic velocity associated with soil freezing and thawing, enabling continuous monitoring of the freezing front depth. Seismic monitoring will be paired with continuous recording of soil temperature, water content and electrical conductivity, alongside periodic pore water sampling at multiple depths (DOC, 87Sr/86Sr, δ2H and δ18O) to constrain DOC sources and fate throughout the year.
Geochemical analyses will be carried out at the partner’s (UCLouvain) facilities.
Impact & dissemination
CRISP will produce a unique high-resolution, full-year record of riverine DOC export from a small Arctic permafrost watershed, directly addressing a systematic gap in the carbon flux estimates used by Earth System Models. The project will improve understanding of how permafrost thaw alters the timing and magnitude of land-to-ocean carbon transfer, an information currently missing from permafrost feedback projections.
CRISP will demonstrate a transferable seismo-geochemical monitoring toolkit capable of operating autonomously through Arctic winter conditions, with potential for broader deployment across the pan-Arctic region.
CRISP’s unique fieldwork progress will be reported through videos and blogs on social media channels of the Royal Observatory of Belgium as well as through collaborations with Belgium schools, artists and public events. Scientific results will be disseminated through reports, conferences and publications.
