A Group for High Resolution Sea Surface Temperature (GHRSST) Level 4 sea surface temperature analysis produced daily on an operational basis by the Danish Meteorological Institute (DMI) using an optimal interpolation (OI) approach on a regional 0.03 degree grid. The analysis is based upon nighttime GHRSST L2P skin and subskin SST observations from several satellites over the North and Baltic Seas. The sensors include the Advanced Very High Resolution Radiometer (AVHRR), the Advanced Along Track Scanning Radiometer (AATSR), the Spinning Enhanced Visible and Infrared Imager (SEVIRI), the Advanced Microwave Scanning Radiometer-EOS (AMSRE) and the Moderate Resolution Imaging Spectroradiometer (MODIS) on Aqua. An ice field from the Swedish and Finnish ice services is used to mask out areas with ice.