Rapid Increase in Geogenic CO2 Emissions from Antarctic Permafrost

Thawing permafrost can amplify climate change by releasing previously stored carbon, but observations of this feedback come mainly from the Arctic. Ice-free Antarctic terrains are generally regarded as minor CO₂ sources, although sub-permafrost brines and deep carbon reservoirs may support localized geogenic degassing. We report repeated soil CO₂ flux and soil-gas surveys in the Taylor Valley in 2020, 2023, and 2025. The mean flux increased from 1.73 to 9.49 g CO₂ m⁻² d⁻¹, the median from 1.20 to 6.70 g CO₂ m⁻² d⁻¹, the 90th percentile from 4.11 to 20.62 g CO₂ m⁻² d⁻¹, and the maximum from 11.36 to 72.99 g CO₂ m⁻² d⁻¹. Carbon isotope ratios of CO₂ and CH₄ are consistent with a substantial deep geogenic contribution and thermogenic or mixed signatures, with limited microbial influence at the highest flux sites. Geological and electrical-resistivity observations identify heterogeneous permafrost, brine-bearing horizons, and potential permeable pathways, but the available data do not establish whether permafrost thaw or subglacial drainage caused the temporal increase. Conditional scaling of the campaign-specific areal emission densities to the 4,500 km² ice-free area of the McMurdo Dry Valleys yields 1.14–15.90 Mt CO₂ yr⁻¹, whereas scaling to 21,745 km² of mapped Antarctic ice-free terrain yields 5.51–76.84 Mt CO₂ yr⁻¹, equivalent to a maximum of approximately 0.021 Pg C yr⁻¹. These calculations represent illustrative spatial-scaling scenarios rather than regional emission inventories or temporal forecasts. The observations demonstrate substantial, spatially focused geogenic degassing and motivate co-located thermal, hydrological, and geophysical monitoring.