During the last 15 years a number of case studies of the `Odden' sea ice feature in the Greenland Sea has been carried out. The `Odden' ice feature is a rapidly varying peninsula (sometimes island) of ice in the central Greenland Sea. It varies in size from tens of 7 - 800 kilometers within a few days, and both formation and decay can be this rapid. Visual and infrared images from NOAA AVHRR have been used to study this variability for many years, but due to cloud cover detailed analysis of formation and decay have seldom been possible. Examples from several years will be shown. Passive microwave observations of the thermal microwave radiation from the surface have been carried out with the NIMBUS-5 ESMR, the NIMBUS-7 SMMR and the present SMM/I. With this technique it is possible to observe rapid variability, independent of cloud cover. Examples from several years will be given. Finally, ERS-1 SAR (Synthetic Aperture Radar) images has allowed detailed studies of limited areas within the `Odden' ice feature. Examples will be given. Conclusions as to the advantages and disadvantages of the different sensors and the synergy of using all of them will be drawn.