This results in an unstable stratification of the ocean layer and deep water formation can occure. The opposite behaviour can be observed when sea ice melts. The additional freshwater causes the ocean to form a stable boundary layer. Ice concentration from passive microwave sensors Satellite passive microwave imagers are measuring the upwelling radiation from the ground. Current imagers deliver global coverage on a daily basis.
Measurements are independent of night and day.
The influence of the atmosphere is small in comparison to imagers operating in the infrared and visible regime of the spectrum. Satellite passive microwave imagers have provided this information for most of the past 20 years and are presently an integral part of operational monitoring programmes that will be continued into the foreseeable future. The potential of passive microwave data to observe sea ice distributions on a global scale is demonstrated with an animation of the annual cycle of ice concentration in the Antarctica. . For the trend analysis ice concentrations were averaged monthly. In order to remove the high seasonal variability, the climatological monthly mean was subtracted from the data to get the ice extend and icearea anomalies.