COMPARISON OF AIRBORNE ELECTROMAGNETIC ICE THICKNESS DATA WITH NOAA AVHRR AND ERS-1/SAR IMAGES/

Snow-plus-ice thickness and surface-ice roughness data collected by a helicopter-towed sensor package was used to identify surface-ice prope rties in March 1992 AVHRR and SAR images for the land-fast and mobile pack ice off the northern coast of Newfoundland. The sensor package co nsisted of an electromagnetic induction sensor and laser profilometer. Observed snow depths and ice thicknesses verified that snow-plus-ice thickness over undeformed ice can be obtained to an accuracy of +/-10 cm. Snow-plus-ice thickness and surface roughness data for flight sect ions covering several hundred kilometres indicated the change in pack ice properties seen in images from thin, smooth coastal ice and open w ater conditions to thick, rough consolidated offshore pack ice. Ice ch arts covering the same area showed similar variations in ice condition s based on AVHRR and fixed-wing reconnaissance data. In the ERS-1 SAR image, low backscattering coefficients were associated with large, smo oth coastal flees interspersed with areas of high backscatter indicati ng the presence of waves in open water areas. Backscattering coefficie nts were higher in the rubble areas near the inshore edge of the pack ice than in the interior of the pack ice itself. Distinguishing ice ty pes on the basis of tone alone in SAR imagery was found to be problema tic; however in combination with other remotely sensed data such as AV HRR data, SAR data will become more useful in distinguishing ice types .