Subglacial and Seabed Topography, Ice Thickness and Water Columm Thickness in the Vicinity of Filchner-Ronne-Schelfseis, Antarctica

The seabed morphology beneath the ice shelf is dominated by a slope down towards the interior of the continent. Deep troughs, possibly glacially deepened, run beneath the eastern and weatern sides of the ice shelf and cross the continental shelf. An area of small water column thickness to the north-west of Berkner Island suggests that extensive grounding could occur after a relatively small change in the ice shel

Improved determination of sea surface heights close to the Australian coast from ESR-2 satellite radar altimetry

The homogeneous and repeated data coverage over coastal regions from satellite radar altimetry is one important data source for oceanographic and geodetic applications. However, the sea surface heights (SSH) extracted from the altimeter data are often in error close to the coast, due in part to the complex nature of echoes returned from rapidly varying coastal topographic surfaces (both land and sea) and the generally rougher sea state. This paper presents improved SSH results derived from ERS-2 altimeter waveform data (two cycles of 35-day repeat orbit, March to May 1999) near the Australian coast using a coastal retracking system. This system was developed based upon a systematic and comprehensive analysis of return waveforms. Central to the system is the use of two retracking techniques: the iterative least squares fitting and the threshold retracking algorithms. Using the AUSGeoid98 geoid grid as a quasi-independent ground reference and comparing with a broad contaminated distance of ∼10 km obtained from a previous study before retracking, the use of the retracking system is able to reduce this contaminated distance to ∼5 km. However, improved SSH data cannot be recovered by waveform retracking less than ~5 km from the coastline due to predominant land returns in the waveform range window

Post-processing Altimeter Data Towards Coastal Applications and Integration into Coastal Models

International audienceAltimetry missions in the last 16 years (TOPEX/Poseidon, ERS-1/2, GFO, Jason-1 and ENVISAT) and the recently-launched Jason-2 mission have resulted in great advances in deep ocean research and operational oceanography. However, oceanographic applications using satellite altimeter data have become very challenging over regions extending from near-shore to the continental shelf and slope (Cipollini et al. 2008). In these regions, intrinsic difficulties in the corrections (e.g., the high frequency ocean response to tidal and atmospheric loading, the mean sea level, etc.) and issues of land contamination in the radar altimeter and radiometer footprints result in systematic flagging and rejection of these data. Forthcoming altimeter missions (SARAL/AltiKa, SWOT, Sentinel-3, etc.) are designed to be better-suited for use in the coastal ocean. However, a number of studies have dealt with the problem of re-analysing, improving and exploiting the existing archive to monitor coastal dynamics. The early encouraging results (Vignudelli et al. 2005; Bouffard et al. 2008, Birol et al. submitted J Mar Syst 2009) support the need for continued research in coastal altimetry, with the opportunity of providing input and recommendations for future missions.This chapter reviews the current status of the X-TRACK processing application (Roblou et al. 2007), whose objectives are to improve both the quantity and quality of altimeter sea surface height (SSH) estimates in coastal regions by reprocessing a posteriori (the standard Geophysical Data Records) (GDR) as delivered by operational centres, i.e. by improving the post-processing stage. Latest improvements on along-track spatial resolution (high rate data streams and removal of large-scale errors) that promise improved monitoring of coastal dynamics are also detailed. In addition, with a view to integrating coastal-oriented altimeter datasets into models for coastal ocean state analysis, methodologies for matching models with observations are discussed