Hamburg 2009 – scientific programme

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UP: Fachverband Umweltphysik

UP 6: Kryosphäre I

UP 6.4: Talk

Thursday, March 5, 2009, 12:12–12:24, VMP 8 R206

Sea Ice Freeboard Estimates in the Weddell Sea from ICESat Laser Altimetry — •Markéta Pokorná, Gunnar Spreen, Stefan Kern, Lars Kaleschke, and Detlef Stammer — Institut für Meereskunde, Universität Hamburg

Antarctic sea ice studies are of big importance in order to understand their role in the climate system. Sea ice thickness can be derived from sea ice freeboard height, which is the part of the ice including snow above the waterline. Freeboard can be determined from laser altimetry. The Geoscience Laser Altimeter System (GLAS) mounted on NASA's ICESat satellite measures its distance to the Earth surface with centimeter accuracy. Knowing the height of the satellite relative to an Earth reference ellipsoid from orbit determination, the surface elevation relative to this ellipsoid can be derived. To obtain the sea ice freeboard the sea surface height (SSH) is subtracted from the derived surface elevation. SSH consists of geoid height plus dynamic topography and tides. An accurate geoid plays an important role in the determination of freeboard. The SSH is further approximated by the minimal residuals in the GLAS elevations which are associated with open water or thin ice areas between thick ice areas. This method is compared with quasi-coincident Synthetic Aperture Radar images and sea ice data from passive microwave sensors. Sea ice freeboard heights are estimated for austral fall 2005 and 2006 for the Weddell Sea.