due to a poor understanding of chan

due to a poor understanding of changes in the soil thermal regime and liquid water content during the soil-freezing process.using an integrated approach combining in situ soil measurements, (PolSAR) and a remote-sensing-driven permafrost model. To better capture landscape variability in snow cover and its influence on the soil thermal reanalysis snow depth data using MODIS snow cover extent (SCE) observations.along the Alaska North Slope the observed and model-simulated zero-curtain periods were positively correlated with a MODISderived snow cover fraction (SCF) from September to October。examined the airborne profile along this transect in 2014 and 2015, which is sensitive to near-surface soil liquid water content and freeze–thaw status.On regional scales, the simulated zero curtain in the upper (< 0:4 m) soils showed large variability and was closelyassociated with variations in early cold-season snow cover.Areas with earlier snow onset generally showed a longerzero-curtain period; however, the soil freeze onset and zerocurtain period in deeper (> 0:5 m) soils were more closelylinked to maximum thaw depth. Our findings indicate that adeepening active layer associated with climate warming willlead to persistent unfrozen conditions in deeper soils, promoting greater cold-season soil carbon loss.