Passive microwave imagery of sea ice at 33 GHz

Abstract

Passive microwave (33 GHz) imagery has been examined to ascertain if changes in radiometric temperature can be used to detect and classify sea ice of varying age and thickness, and in various stages of formation, deformation, and weathering. The high-resolution imagery was compared with simultaneous aerial photography to allow for detailed correlation of surface features. The lowest radiometric temperatures were displayed by open water, new ice (presumably moist surface), and multiyear ice floes which suggested a history of high internal stress. The pattern of low radiometric temperatures in areas of multiyear ice suggest that internal stress may cause changes in crystal structure which result in lowered radiometric temperatures. The highest radiometric temperatures were displayed by thin ice (presumably without a wet surface), new ridges, and frozen melt ponds. The older thicker areas of first-year ice appeared to have lower radiometric temperatures than the thinner areas of first-year ice. Individual multiyear ice floes often displayed a wide range of radiometric temperatures. This variation has been attributed to changes caused by melting and erosional processes, and from stresses caused by ice floe collisions. Observations of microwave images of old ice floes indicate that they are somewhat transparent to microwave radiation, and that the primary source of the radiation is not from the surface but from within the ice column. © 1980.