Metal – organic carbon interactions in Arctic permafrost: spatialization and meta-analysis

Details

Supervisors

Opfergelt, Sophie ; Thomas, Maxime

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

The northern permafrost’s extent covers 21 million km² which represents 22% of the Northern Hemisphere’s exposed land area. Within these 22%, it is estimated that 1460 to 1600 GT of organic carbon (OC) are stored. This estimation is yet growing as new research refines and adds new components to existing studies. With current climate change - occurring at a greater rate in the Arctic regions than the global average - there is a crucial need to further investigate the possible fates of this OC. A key element to consider in this regard concerns OC-mineral interactions. Among the mechanisms of OC-mineral interactions, OC complexation with metals is one of the main and constitutes a pool of OC that is not directly accessible to microbial decomposition. Here, we aim to use existing methods for quantifying OC stocks at the Arctic scale to (i) integrate new data for the total OC (TOC) stock estimation and (ii) provide a first assessment of the OC storage in the form of organometallic complexes at the Arctic scale. This method partitions OC in three pools, each of which is assessed using different methods: the surface (0-3m) pool using a database coupled with soil taxonomy, the Yedoma domain (deep ice-rich sediment deposit) through a bootstrapping method and the Deltaic alluvium (thick river sediments) whose stock of complexed OC is assessed from existing TOC data and general trends. Our calculations led to a count of 375 GT of OC stabilized in the form of complexes across the Arctic, subdivided into (i) 263 GT for the 0-3 m pool with peak concentrations in Canada and Russia, (ii) 89 GT within the Yedoma sediments (>3m) and (iii) roughly 23 GT in the deltaic alluviums (>3m). Overall, it implies that 23% of the TOC pool is stabilized within metals complexes in the Arctic, and that this carbon is not directly available for microbial decomposition. Further assessments are therefore required, particularly regarding the behavior of these complexes over time and under changing physico-chemical conditions induced by climate change. Our research highlights the crucial need to incorporate mineral-OC interactions into climate models to enhance the accuracy of future permafrost carbon emission predictions.