Snow specific surface area (SSA) calibration measurements during the ALERT2018 campaign

The IceCube is a commercial instrument manufactured by A2 Photonic Sensors that provides specific surface area (SSA). The IceCube measures hemispherical reflectance of a snow sample by illuminating it using a laser diode at a wavelength of 1310 nm. The reflectance is recorded as voltage using a signal-to-reflectance relationship. From the recorded reflectance, SSA is obtained using a radiative transfer model. To obtain reliable SSA values, a smooth surface of the snow sample is required. In some cases, e.g. for brittle depth hoar or large grains, it may be difficult to ensure a flat surface and instead hollows or out sticking grains may occur, increasing the uncertainty of the measurement. The IceCube instrument is calibrated first before each time it is used using six standards. These calibration measurements were obtained in connection to classical snow pits during the ALERT2018 campaign in May 2018 over the sea ice in the Lincoln Sea.