HR: 0830h
AN: G21C-0277    [PDF]
TI: An inter-comparison of ocean tide loading estimates for Antarctica from models and GPS
AU: * King, M
EM: m.a.king@ncl.ac.uk
AF: School of Civil Engineering and Geosciences, University of Newcastle, Bedson Building, Newcastle Upon Tyne, NE17RU United Kingdom
AU: Clarke, P
EM: Peter.Clarke@newcastle.ac.uk
AF: School of Civil Engineering and Geosciences, University of Newcastle, Bedson Building, Newcastle Upon Tyne, NE17RU United Kingdom
AU: Allinson, C
EM: C.R.Allinson@ncl.ac.uk
AF: School of Civil Engineering and Geosciences, University of Newcastle, Bedson Building, Newcastle Upon Tyne, NE17RU United Kingdom
AB: We present ocean tide loading (OTL) estimates for Antarctica based on several numerical tide models and direct estimates from GPS observations. Accurate estimates of the ocean tides in the Antarctic region are difficult to obtain from numerical ocean tide models due to the lack of bathymetric information and direct tidal observations in the sub ice shelf regions in particular. Consequently, independent measurements, such as from GPS, with an extensive spatial distribution are extremely important to ensure geodetic and altimetric (e.g, IceSat) measurements are not biased by mismodelled OTL. We show that there are large variations in diurnal and semi-diurnal OTL estimates from nine numerical tide models in the regions of the very large Ross and Filchner-Ronne ice shelves. The standard deviations of the M$_{2}$, S$_{2}$, O$_{1}$, K$_{1}$ model estimates in these regions have a maximum of approximately 10, 5, 5 and 5 mm respectively for the real components and approximately 10, 5, 3 and 3 mm respectively for the imaginary components. These represent variations of up to 50% of the modelled load. Recent numerical tide models are in better agreement, although substantial variation still exists. In the non ice shelf regions the models are typically in agreement at the 1-2 mm level. We report on the impact of this mismodelling on ice sheet thinning rate estimates from GLAS measurements with the degraded IceSat orbit. In order to provide an external validation of the model estimates we estimated the eight major diurnal and semi-diurnal harmonic loading terms directly in our GPS analysis of data from $\sim20$ sites distributed mainly around the perimeter of the continent. By combining estimates from up to several thousand days at each site constituent amplitudes were determined with uncertainties generally less than 1 mm. Phase uncertainties are dependent on the constituent amplitude but are generally 5-20$\deg$. We compare these estimates with the modelled values and recommend optimal numerical tide models to be used in OTL computations for geodetic measurements in Antarctica.
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 1243 Space geodetic surveys
DE: 1249 Tides--Earth
SC: Geodesy [G]
MN: 2003 Fall Meeting