Altimetric Mean Sea Surfaces - and inter-annual ocean variability (DNSC05-MSS)
Ole Andersen(1) , Anne Louise Vest(1) , and Per Knudsen(1)
Danish National Space Center,
Juliane Maries vej 30,
Dk-2100 COpenhagen O,
The central quantity bridging the geoid and the ocean circulation is the mean dynamic topography (MDT), which is the difference between the mean sea surface and the geoid. In a comparison between hydrodynamic derived MDT and synthetic derived MDT derived from the difference between the Mean sea surface and the geoid, the result depends of the quality of the different surfaces but also on the inter-annual ocean variability. In principle the mean sea surface used to derive the synthetic MDT should be the same period as used to average the hydrodynamic derived MDT.
Different global mean sea surfaces (CSR98, GSFC00, CLS-SHOM98, CLS01, KMS01) are based on different time-epoch for the T/P altimetry used in their derivation. Consequently, inter-annual ocean variability (like the major El-Nino event in 1997-1998) will be visible to a larger or smaller extend in these different MSS. (the MSS are actually quasi-stationary MSS).
We have investigated a method to model the effect of inter-annual ocean variability on the derived Mean Sea Surface. This way the derived mean sea surface can be made to include the inter-annual variability for a specific period (creating a quasi-stationary MSS over the selected period). From the 12 years of T/P altimetry the inter-annual ocean anomalies have been modeled using the averaged sea level height relative to the MSS and the long-term trend.
Evaluation of the available mean sea surfaces will be carried out in GOCINA study region in the Northern Atlantic region. An extended comparison will also be presented in the Arctic Ocean to demonstrate the impact of improved geoid and mean sea surface modeling to derived reliable synthetic Mean Dynamic topography.