Space-time analysis of sea level in the North Atlantic from TOPEX/Poseidon satellite altimetry
Spatial and temporal sea level variability in the North Atlantic is investigated from Topex/Poseidon (T/P) altimetry data. Time series of sea level anomalies on a regular 5° grid are analysed. Non-linear denoising through thresholding in the wavelet transform domain is carried out for each series in order to remove noise while preserving non-smooth features. Principal Component Analysis (PCA) is used to obtain a spatio-temporal description of the sea level field. To avoid modal mixing and improve interpretation of the principal modes, PCA is implemented separately for seasonal and trend components of the sea level field obtained from a wavelet-based multiresolution analysis. The leading pattern of the seasonal field reflects the dominance of a stable annual cycle over the study area and the change in the seasonal regime approaching the equator with contribution of the semi-annual cycle and phaseshift in the annual cycle in the tropical Atlantic. The leading pattern of the trend field is a broad spatial pattern associated with North Atlantic Oscillation (NAO), reflecting the influence of atmospheric conditions on interannual sea level variability.
Keywordssatellite altimetry sea level change discrete wavelet transform PCA
Unable to display preview. Download preview PDF.
- AVISO (1996). User handbook merged TOPEX/POSEIDON Products, AVI-NT-02-101-CN ed 3.0, 1996Google Scholar
- Fernandes M. J., L. Bastos and M. Antunes (2003) Coastal Satellite Altimetry — Methods for Data Recovery and Validation, Proceedings of the 3rd Meeting of the International Gravity & Geoid Commission (GG2002), pp. 02–307, Tziavos, I. N. (Ed.), Editions ZITI.Google Scholar
- Hurrell, J. (1995). Decadal trend in the NAO: regional temperatures and precipitation. Science, 269, pp. 676–679Google Scholar
- Jollife, I. T. (2002). Principal Component Analysis, SpringerGoogle Scholar
- Marshall, J., Y. Kushnir, D. Battisti, P. Chang, A. Czaja, R. Dickson, J. Hurrell, M. McCartney, R. Saravanan, and M. Visbeck (2001). Review: North Atlantic climate variability: Phenomena, Impacts and Mechanisms. Int. Journal of Climatology, 21, pp. 1862–1898Google Scholar
- Percival, D. and A. Walden (2000). Wavelet methods for time series analysis, Cambridge University PressGoogle Scholar
- von Storch, H. and F. W. Zwiers (1999). Statistical Analysis in Climate Research, Cambridge University PressGoogle Scholar