Global Warming and Soil Organic Carbon Stock Dynamics: Ice-Free Areas in Maritime and Peninsular Antarctica as Emerging Carbon Sinks

The Antarctic cryosphere is among the most climate-sensitive terrestrial ecosystems, yet the impacts of accelerated climate change on soil organic carbon (SOC) stocks and dynamics remain uncertain. Addressing these knowledge gaps is essential for refining global warming mitigation strategies, supporting Antarctic conservation, and improving environmental management. This study evaluates the potential effects of global warming on SOC stocks and dynamics under the Shared Socioeconomic Pathway (SSP) 1-2.6 scenario, which projects a 1.5°C temperature increase. Using an extensive Antarctic soil database with data from 2,800 observation sites, we integrate field-collected soil data, machine learning techniques, and climate projections for ice-free regions of Maritime and Peninsular Antarctica to predict SOC stocks and their variations within the 0–30 cm soil layer. Additionally, soil bulk density analysis was performed on 127 samples, enabling the development of a regression-based pedotransfer function to estimate bulk density for the remaining dataset, which was then incorporated into SOC stock modeling. This function was constructed based on easily measurable field variables, including pH, SOC content, and soil texture (sand, silt, and clay fractions). Our predictive SOC modeling utilized terrain attributes and bioclimatic variables from the CHELSA database, primarily focusing on temperature, precipitation, and net primary productivity. Model performance, assessed via the concordance correlation coefficient, yielded a median value of 0.54 across the 0–30 cm depth range. Climate change projections indicate an increase in SOC stocks, reaching approximately 359 ± 146 Mg under the SSP 1-2.6 scenario. Key environmental drivers of SOC stocks include net primary productivity, temperature, and precipitation, alongside soil properties such as effective depth, texture, bulk density, and topographic relief. Our findings suggest that ice-free regions of Maritime and Peninsular Antarctica may function as carbon sinks under a 1.5°C warming scenario. Regions with initially low SOC stocks are generally projected to experience an increase, while those with higher initial values may decline. In colder environments where SOC is in equilibrium, rising temperatures could destabilize this balance, leading to substantial carbon dioxide emissions. The extent of SOC sequestration potential depends on initial SOC content and soil depth, with most study sites exhibiting low SOC stocks, making an increase likely. Temperature and precipitation remain the primary regulators of estimated SOC stocks due to their direct link with net primary productivity. These insights contribute to understanding SOC dynamics in Antarctic ecosystems and their role in climate change feedback mechanisms.