Gunnar Spreen works at the University of Bremen, Germany, were his research group is developing new methods for satellite remote sensing of polar regions. A strong focus is on remote sensing of sea ice properties from microwave radiometers. Currently sea ice concentration, thin ice thickness and multiyear ice concentration data are produced on a daily basis in addition to melt pond fraction from optical sensors (www.seaice.uni-bremen.de and http://www.meereisportal.de). Satellite measurements are validated using ground-based and airborne field observations. Gunnar's main interest is improving remote sensing datasets and use them for a better understanding of climate processes in Polar Regions.