Tidal analysis of Cryosat-2 data over ice-free regions of the Arctic Ocean
Event: 2018 Ocean Surface Topography Science Team Meeting
Session: Tides, internal tides and high-frequency processes
Presentation type: Type Poster
Until the launch of Cryosat-2 the only satellite altimeter data available to constrain tidal models in the northern latitudes above 72° were from sun-synchronous satellites. Although they give useful data for lunar tides, sun-synchronous satellites are of very little value for solar tides. Cryosat-2 is thus a valuable data source for improving tidal models. Its long 369-day orbit repeat implies the data must be analyzed differently from methods used for satellites with short repeat periods. The most straightforward method is to rely on analyzing heights relative to the mean sea surface (MSS). Whether MSS models are accurate enough is still an issue in some regions (especially high latitudes), but the latest and best MSS models do employ several years of Cryosat data, which clearly helps support use of the data for general oceanographic applications. Zaron (J. Phys. Oceanogr., 2018) recently showed the benefit of using Cryosat data in the Ross Sea, including over the Ross Ice Shelf; he used all three tracking modes and performed an initial analysis devoted to improving the MSS. Cancet et al. (Adv Space Res, 2018) have reported promising results with Cryosat data in the Arctic Ocean. In this paper, further tidal analyses of Cryosat and combined Cryosat and Envisat data are investigated, primarily in the high North Atlantic and Arctic Oceans. Performing tidal analyses of Cryosat data in regions where we already have high-quality Topex and Jason data, as well as ERS and Envisat data, allows us to compare and assess solutions. In general, the Cryosat tidal solutions are superior to ERS-Envisat tidal solutions, even for lunar tides, and for solar tides there is, of course, no comparison. While Cryosat gives sub-optimal sampling of the K2 tide, this can be overcome by employing the Munk-Cartwright response method, essentially tying K2 to the better-determined S2. Tidal analyses of altimetry reveal differences relative to existing Arctic Ocean tide models, mostly in expected locations (high-amplitude shelves), but validation is challenging owing to lack of high-quality in situ measurements.