CoAuthors

Mattias Raynal (CLS, France); Florent Lyard (LEGOS, France)

Thanks to its current accuracy and maturity, altimetry is considered as a fully operational observing system dedicated to scientific and operational applications. In order to access the targeted ocean signal, altimeter measurements are corrected for several geophysical parameters among which the ocean tide correction is one of the most critical. Global ocean and loading tide models GOT and FES are operationally used in present altimeter GDRs. FES is a finite elements hydrodynamic model which assimilates altimeter and in situ data, while GOT model is build as an empirical adjustment based on altimeter data and a prior atlas (such as FES). These global ocean tide model are barotropic models; by essence they do not take into account the internal tide generation and propagation processes and they do not correct from the internal tides signature at the surface.
Indeed internal tides can have a signature of several cm at the surface with wavelength about 50-250 km for the first mode. The perspective of SWOT mission and high resolution ocean measurements make the correction of these small scale signals a challenge, as we need to be able to separate tides from other oceanic signals.
Several previous studies have shown the interest of altimeters to estimate this signal (Ray and Mitchum 1996-1997, Carrere et al. 2004, Ray and Zaron 2011). In this study we use the global altimeter database used in FES2012 model to perform a new estimation of the internal tides signatures at the global scale. The long time series available allow a better estimation of the amplitude and the variability of this signal. Three altimeter time series are considered (TPJ1J2, TPNJ1N and E1E2EN) and the baroclinic signal coherent with the four main barotropic tides (M2, N2, S2, K1) are estimated here. Perspectives of improvements of these analysis and the tests made to correct the internal tide signal signature are also presented.