Periodic Reporting for period 4 - THAWSOME (THAWing permafrost: the fate of Soil Organic Matter in the aquatic Environment)
Periodo di rendicontazione: 2021-06-01 al 2022-09-30
Horizontal OC release either occurs via gradual thaw, slowly leaching OC into aquatic systems, or via abrupt thaw, where ground-ice melt causes destructive surface collapse and slumping of OC into aquatic systems. Both types of thaw facilitate decomposition of OC (generating GHG) but also re-bury OC into sediments (sequestering OC). The relative importance of decomposition versus burial is unknown.
In THAWSOME, we will combine a multi-scale approach combining detailed process-based field studies with up-scaling techniques on multiple levels: (i) observational, using large Arctic rivers as natural integrators, (ii) numerical, using a coupled hydrological-biogeochemical model, and (iii) spatial, using GIS-based analysis. Our objectives are to quantify, for the first time, decomposition of particulate OC from permafrost and to assess the fate of permafrost OC in the nearshore zone and the continental shelf.
THAWSOME will generate critically needed quantitative data on the amount of decomposition versus burial of permafrost OC, as well as qualitative insights into the processes that control this.
Our publication record is strengthening the realisation that in the scientific studies focusing on thawing and degrading permafrost, it is absolutely needed to include particulate matter. The research communities that study permafrost thaw are frequently NOT considering (aquatic) lateral transport, and the research community that does focus on lateral transport is frequently only focusing on dissolved matter. Our research has changed this.We also have highlighted the strong spatial heterogeneity of particulate matter degradation. In some systems, overwhelmed by abrupt and local thaw features, particulate matter may be a fairly conservative transport mode moving thawing organic matter from soils into debris tongues. In these systems, degradation and greenhouse gas release may be low. In other systems, where gradual but wide-scale thaw occurs, particulate matter is not so abundant but does degrade more quickly. Including particulate matter dynamics in aquatic systems surrounded by permafrost thaw can therefore either be an attenuating or a strengthening component in the generation of greenhouse gases.