Hydrothermal-hydrological conditions control water dissolved organic carbon of the central Qinghai-Xizang Plateau permafrost regions

Study region The Beiluhe Basin in the interior of the Qinghai-Xizang Plateau (QXP), a high-altitude permafrost region sensitive to climate warming. Study focus Dissolved organic carbon (DOC) is a primary pathway for terrestrial carbon transfer to aquatic ecosystems. Compared to the Arctic, the coupling mechanisms between active layer hydrothermal processes and DOC in different water components in the interior QXP remain poorly understood. This study investigates DOC dynamics in streams, thermokarst lakes/ponds, and groundwater from 2020 to 2023. By integrating meteorological data, soil hydrothermal conditions, and groundwater level and temperature, we analyze the regulatory mechanisms of hydrothermal conditions and active layer thawing on DOC export across different water components. New hydrological insights for the region Results reveal a distinct asynchronous response mechanism. Thermokarst lakes/ponds act as early responders, peaking in DOC during the thaw initiation period driven by surface flushing. Conversely, streams and groundwater act as late responders, reaching maximum DOC concentrations in the post-thaw period due to the lagged release of deep soil carbon caused by active layer deepening. This vertical hydrothermal lag of the active layer and water level fluctuations regulate hydrological connectivity and DOC transport pathways. These findings are essential for accurately simulating the carbon cycle and predicting climate feedback effects in the QXP permafrost region.