Time-series analysis of seasonal and interannual signals in the tide-gauge record

Author: Emma M. Hill, Rui M. Ponte and J.L. Davis
Date: 
December 1, 2006
Type: 
Presentation
Venue: 
AGU Fall Meeting, San Francisco
Citation: 

Hill, E.M., R.M. Ponte, and J.L. Davis, 2006. Time-series analysis of seasonal and interannual signals in the tide-gauge record, AGU Fall Meeting, San Francisco, December 2006.

Comparison of monthly mean tide-gauge time series to corresponding model time series based on a static inverted barometer (IB) for pressure-driven signals and a general circulation ocean model (OM) reveals that the combined model successfully reproduces seasonal and interannual changes in relative sea level at many stations. Removal of the OM and IB from the tide-gauge record produces residual time series with a mean global variance reduction of 53%. The OM is mis-scaled for certain regions, and 68% of the residual time series contain a significant annual signal after removal of the OM and IB from the tide-gauge data. Including OM admittance parameters and seasonal signal coefficients in a regression model for each station, with IB also removed, produces residual time series with mean global variance reduction of 71%. Examination of the regional improvement in variance caused by scaling the OM, including seasonal terms, or both, indicates weakness in the model at predicting sea-level variation for constricted ocean regions. The model is particularly effective at reproducing sea-level variation for stations in North America, Europe, and Japan. The RMS residual for many stations in these areas is 25--35 mm. Understanding the oceanographic signal in the tide-gauge time series is important for further analysis of non-secular and regionally differing sea- level variations. Understanding the ocean model's strengths and weaknesses will also allow for future improvements of the model.