Thin sea ice identification in the Kara Sea using AMSR-E data

In this study we have examined the identification of polynyas in the Kara Sea region with AMSR-E radiometer data. We have utilized a threshold value of the spectral gradient of vertically polarized brightness temperatures between frequencies 89 GHz and 36 GHz. As a comparison, ice thickness defined from the surface temperature measured with MODIS, is used. In clear sky conditions the correspondence is good, 72 % of all thin ice pixels with a mean thickness up to 15 cm were correctly identified, and 3.4 % were mischaracterized as thin ice, when these, according to MODIS thickness charts, were thicker than 40 cm. The precise definition of the ice thickness, according to our study, was not possible, unlike reported in some previous studies.