Objective of the Research and Research Components
The ultimate objective of this study is the determination of the sea surface topography (SST) at local and regional scales along the coastlines of Canada. Due to the varying spatial information inherent in the different data sets and models under consideration, the multi-resolution analysis approach will be taken. The task is extremely challenging and involves multidisciplinary approaches, analyses and validation of heterogeneous data sets both historical and modern. It also involves space geodetic techniques (altimetry and LEO missions) and theoretical modelling of the dynamics of the oceans.
We will approach our study from two distinct perspectives namely, the “geodetic” and “oceanographic,” aiming at two independent SST determinations respectively and studying, understanding and resolving any discrepancies. Consequently, we will attempt to assimilate absolute sea surface tilts from geodetic determinations into the ocean models and conversely, use oceanographically determined slopes to constrain inverse methods of the geoid from geodetic methods. Finally, we will make a synthesis of the two approaches to build a composite model of the SST. Post-glacial rebound model displacements and an accurate geoid model will provide additional benchmark information and data. The link between satellite altimetry and the new LEO gravity missions as well as the development of a marine geoid model will be the subject of another Phase III project proposal entitled “Space gravimetry contributions to Earth monitoring.”
We propose to create a Canadian Satellite Altimetry Processing Centre (CSAPC), which will produce global oceanographic and geodetic products similar to those of the National Survey and Cadastre Denmark (KMS), Scripps Institution of Oceanography, and NOAA Laboratory for Satellite Altimetry. So far Canada has not explored such possibility although there is significant knowledge base with international recognition. What follows are the research components necessary to achieve the overall objective:
1. GPS on tide gauges and geodetic levelling:
- Separation of the crustal deformation and sea level variation signal using GPS, other in-situ geodetic measurements and existing hydrodynamic models.
2. Tide gauge and altimetry data filtering:
- Separatation of high frequency noise (coloured or other) from tide-gauge records that obscure crustal movement and other oceanographic signals.
3. Seaboard gravity data evaluation and integration:
- Seaboard gravity data complement land gravity measurements and contribute to the extension of the land geoid model to the coastal areas.
4. Satellite altimetry
- Altimetry and other mission data will be merged to compute an optimal high-resolution mean SSH along with its error characteristics. Creation of the CSAPC.
5. LEO gravity models
- The recent satellite missions (CHAMP and GRACE) and future GOCE will make possible the improvement of the oceanic geoid.
6. Ocean dynamic modeling and data assimilation
- Calculate seasonal mean sea levels with respect to an equipotential surface from ocean circulation models that have been forced with climatological salinity, temperature, and wind fields.