We report sea-ice temperature and bulk salinity measurements as well as textural analysis from 33 first-year drift- and fast-ice stations sampled between November 2007 and June 2008 in the southern Beaufort Sea–Amundsen Gulf, Canadian Arctic, during the International Polar Year Circumpolar Flaw Lead (IPY-CFL) system study. We use this significant dataset to investigate the halo-thermodynamic evolution of sea ice from growth to melt. A strong desalination phase is observed over a small time window in the spring. Using calculated proxies of sea-ice permeability (brine volume fraction) and of the intensity of brine convection (Rayleigh number) we demonstrate that this phase corresponds to full-depth gravity drainage initiated by a restored connectivity of the brine network with warming in the spring. Most stations had a textural sequence typical of Arctic first-year ice, with granular ice overlying columnar ice. Unusual textural features were observed sporadically: sandwiched granular ice, platelet ice and draped platelet ice. We suggest that turbulence in leads and double diffusion in strong brine plumes following the refreeze of cracks are plausible mechanisms for the formation of these textures.

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We present temperature inversion characteristics during fog and nonfog conditions at three east Greenland coastal weather stations during Arctic melt seasons 1980–2016. For this purpose, we developed a novel automated method to extract fog‐top height (FTH) from Integrated Global Radiosonde Archive data, which is applicable to any fog thermodynamic profile and includes an improved interpolation of saturation between sounding levels. From the analysis of >22,000 melt‐season soundings we conclude that inversions occur 85–95% of the time, are predominantly elevated, and have median depths >200 m. Fog at high‐Arctic locations often penetrates the inversion layer, especially in the late melt season, and is commonly several hundred meters thick. At low‐Arctic locations fog is thinner and generally restricted to the mixed layer. Inversions during fog are deeper and stronger compared to nonfog conditions. This effect is more pronounced at higher latitudes, which we attribute to distinct local boundary layer conditions and large‐scale processes. The Integrated Global Radiosonde Archive‐extracted FTHs have a cumulative error of 56 m and are in reasonable agreement with retrievals from Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite cloud top data. The novel FTH extraction method can be applied to any polar sounding with >5 significant levels below 700 hPa and can be extended to boundary layer clouds other than fog, which represent the majority of cloud occurrence in the Arctic melt season. This study advances the understanding of interactions between low clouds and temperature inversions and improves retrieval of cloud geometrical thickness from radiosondes: both have important implications for the Arctic surface energy budget.

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Assumptions of linear lapse rates in regions prone to surface-based inversions can generate biases in the prediction of surface air temperature. Although studies of Arctic inversions are common, few regional studies of their characteristics exist in high-latitude regions with mountainous topography. To address this gap, vertical atmospheric temperature profiles for five sites in northwestern Canada were analysed using archived radiosonde data from 1990-2016. We present monthly, seasonal, and annual SBI characteristics including the occurrence of transient and persistent SBIs. A novel metric, surface-based inversion impact (SBI_imp), was developed by combining the traditional inversion characteristics of depth, strength, and frequency, and was used to quantify the impact of surface-based inversions on cooling the surface-air temperature. SBI_imp values of > 5°C yr^-1 and ~ 10°C winter^-1 occur locally. A weak linear relationship between sea ice coverage in the Beaufort Sea and SBIimp manifests across parts of the study area, though this relationship does not persist after detrending the datasets. Topographic analysis of areas surrounding each radiosonde location reveal highly variable SBI_imp in complex mountain areas and more consistent SBI_imp across areas of low relief. Our results can help interpret the role of inversions in climatic conditions maintaining cryospheric elements such as permafrost.