Abstract. The contribution of cold season soil respiration to Arctic-boreal carbon cycle and potential feedbacks to global climate system remain poorly quantified, partly due to a poor understanding of the changes in the soil thermal regime and liquid water content during the soil freezing process. Here, we characterized the processes controlling active layer freezing in Arctic Alaska using an integrated approach combining in-situ observations, local scale (~ 50 m) longwave radar retrievals from NASA Airborne P-band polarimetric SAR (PolSAR), and a remote sensing driven permafrost model. To better capture landscape variability in snow cover and its influence on soil thermal regime, we downscaled global coarse-resolution (~ 0.5°) reanalysis snow data using finer scale (500 m) MODIS (MODerate resolution Imaging Spectroradiometer) snow cover extent (SCE) observations. The downscaled 1-km snow depth dataset captured fine-scale variability associated with local topography, and compared well with in-situ observations across Alaska, with a mean RMSE of 0.16 m and bias of −0.01 m in Arctic Alaska, which was used to drive the permafrost model. We also used the in-situ soil dielectric constant (ɛ) profile measurements to guide model parameterization of soil organic layer and unfrozen water content curve. Across a 2° latitudinal zone along the Dalton highway in the Alaska North Slope, the model simulated mean zero-curtain period was generally consistent with in-situ observations (R: 0.6 ± 0.2; RMSE: 19 ± 6 days), which showed mean zero-curtain periods of 61 ± 11 to 73 ± 15 days from depths of 0.25 m to 0.45 m. Along the same transect, both the observed and model simulated zero-curtain periods were positively correlated (R > 0.55, p
Sensitivity of active layer freezing process to snow cover in Arctic Alaska