Saline thermokarst landscapes occur along the Alaskan coastline, where late-Pleistocene marine sediments were deposited when sea levels were higher compared to today. These deposits are particularly prone to thaw because salinity lowers the freezing point of porewater. This is critical in thermokarst lowlands as these landscapes store disproportionately large amounts of organic carbon and the presence of saline permafrost could lead to earlier and more extensive thaw than previously anticipated. In this study, we investigate representative thermokarst landforms along a land-to-sea transect on the Barrow Peninsula, Alaska. Our objectives are (1) to characterize the degradation state of organic carbon and (2) to assess the potential for greenhouse gas (GHG) production from these sediments. We address these aims through biogeochemical analyses, focusing on n-alkane biomarkers and aerobic incubation experiments. Our results show that unfrozen brackish and saline sediments beneath thermokarst lakes and a thermokarst lagoon exhibit stronger organic carbon degradation signals than permafrost and active layer sediments from undisturbed tundra, a drained and refrozen lake basin, and an unfrozen non-thermokarst lagoon. Although saline lake sediments produce less carbon dioxide (CO2) overall due to their lower total organic carbon (TOC) content, CO2 production normalized to TOC is substantially higher in the saline lake (92.1 mg C g−1 TOC) than in undisturbed tundra permafrost (43.6 mg C g−1 TOC), and nearly comparable to the active layer of the drained lake basin (99.3 mg C g−1 TOC). These findings highlight the high vulnerability of organic carbon stored in saline permafrost regions. While absolute CO2 production from saline sediments were measured to be low, their high carbon degradability suggests that potentially TOC-rich saline sediments could become a significant source of greenhouse gases under future thaw scenarios. Our results emphasize the importance of considering salinity as a key factor in permafrost carbon vulnerability assessments.