What is the benefit of high-resolution sea level anomaly datasets? A case study in the Bay of Biscay and New Caledonia regions based on Jason2-3, Saral/AltiKA and Sentinel3

Wavelength spectral analysis of alongtrack altimetric data helps to characterize the seasonal and spatial variability of the sea level anomaly (SLA) signal. It allows us to infer the nature of the surface dynamics (balanced vs unbalanced motion, internal waves). For such analyses, low resolution mode data sets (1 Hz, 6-7 km sampling) are classically used. At this stage there is a strong gap in terms of effective resolution between the 1 Hz along track products (40-70 km resolution) and what is expected from the data of the future SWOT mission. However, the finest spatial sampling is 20 Hz for Jason, and 40 Hz for SARAL/AltiKa. For these products, the main limitation to observe small mesoscale is the existence of a spectral “hump” and a larger noise level due to surface waves and other surface inhomogeneities within the radar footprint. The new concept of SAR mode altimeter as used in Sentinel 3 provides better precision and resolution capabilities. In the prospect of the SWOT mission, this paper focuses on high resolution (HR) datasets from the recent satellite missions based on regional analysis including Jason-2/3, SARAL/AltiKa, and Sentinel-3. At the present time, there is no HR-SLA datasets for all these missions and over the global ocean that are easily usable. In this poster we review different methods and options in the data processing to get HR-SLA. The ability of the different datasets and processing to provide information on the dynamics is illustrated in two contrasted regions: the Bay of Biscay located in the mid-latitudes NE Atlantic and the subtropical region south of New Caledonia in the tropics. The benefit of HR data is evident for scales up to 100 km. It illustrates both the gain brought by the Ka-band of Saral and the SAR mode of S3A over the Ku band of Jason and the benefit of the long time series of Jason data for the studies of internal tides. We emphasize the need to take into account the anisotropy and the very local nature of the ocean dynamics properties in order to assess regional dynamics.