SEA ICE LEADS AND POLYNYA DETECTION USING MULTI-MISSION ALTIMETRY IN THE GREENLAND SEA

摘要

In this study, we present two methods to detect open waterareas in the Greenland Sea based on altimetry measurements.For this purpose, high-frequency data fromENVISAT (pulse-limited altimeter) and Delay-Dopplerdata from CryoSat-2 are used. The radar echoes of bothmissions contain information about the reflectance of theoverflown surface area. For ENVISAT, we use an unsupervisedclassification approach to distinguish betweenwater and ice returns. The waveforms are the main inputfor the classification process. Training data from knownsurfaces are not necessary for our method. For CryoSat-2 SAR mode, an advanced approach is used in order toexploit the multi-look processing of the same resolutioncell from different look angles. We analyse the Range IntegratedPower, a side product providing additional informationabout the backscatter properties. All classificationresults are compared with pictures of imaging SAR satellitemissions (ALOS and Sentinel-1A). In order to takethe time lag between the two observation sets into account,a mean ice-motion is applied to the images. Thisensures realistic comparison results. The classificationapproach allows for an identification of open water (leadsand polynyas) in sea-ice regions and will help to improvesea level estimation in these regions.