Catchment lithology controls net carbon balance along the Antarctic Peninsula

Climate-driven ecosystem change in Antarctica is reshaping carbon dynamics and influencing global climate. Under sustained warming, mobilization and reburial of organic carbon (OC) in coastal Antarctica may represent an important carbon sink, yet regional OC burial and oxidation remain poorly quantified. Here, we apply ramped pyrolysis/oxidation analysis and isotopic end-member mixing models to investigate sedimentary OC along two Western Antarctic Peninsula (WAP) fjords underlain by contrasting bedrock types. We show that the fjord underlain by sedimentary rocks exhibits ten-fold higher burial flux of petrogenic OC (OCpetro) than that dominated by volcanic rocks. We estimate burial fluxes of 6.1–8.8 Gg C yr−1 for biospheric OC (OCbio) and 0.3–3.1 Gg C yr−1 for OCpetro in WAP fjords, respectively, with regional OCbio burial likely exceeding OCpetro oxidation. Model simulations indicate that future ecosystem change may increase regional OC burial flux by 2–4 times, which is critical for predicting the long-term carbon-climate feedback. Thermochemical decomposition and carbon isotopes reveal lithological controls on petrogenic and biospheric organic carbon fluxes; while climate-driven ecosystem change may substantially enhance biospheric carbon sequestration in Antarctic fjords.