Nicolas Bouhier (Ifremer, France)

The GEOSAT 30th anniversary data set contains both Geodetic and Exact repeat mission sensor and geophysical data record that have been reprocessed using up to date retracking and corrections from the original Sensor's data record. This archive which covers more than five years period from march 1985 to December 1989, is of great interest to extend the altimetric climate record back to 1985 to cover more than thirty years.
The detection of icebergs using high rate altimeters waveforms analysis was first demonstrated by Tournadre et al (2008). The Altiberg project, funded by CNES (TOSCA/OSTST), following these studies , uses 9 altimeters from ERS1 to Altika to build a small icebergs data sets. The database is freely available at the CERSAT website http://cersat.ifremer.fr/data/products/catalogue, project altiberg.
The Geosat altimeter had technical characteristics relatively similar to the Topex one., Ku band, 1° antenna beamwidth, 10Hz high rate waveforms. Taking advantage of the availability of the reprocessed SGDR and GDR for the Geosat 30th anniversary the feasibility of the detection of icebergs using Geosat SGDRs was analyzed. The Geosat waveforms are a qulity good enough to allow the detection of icebergs( and also ships). The whole archive was processed and more than 6000 icebergs were detected (see figure). The monthly volume of ice on a reguar polar grid was also estimated to complete the Altiberg records. The global volume of ice transported by the small icebergs can now be analyzed over a 33 year period.