Evaluation of tandem TOPEX/Poseidon-Jason data in the Newfoundland offshore
Fisheries and Oceans Canada,
80 East White Hills Road,
A1C 5X1, St. John's,
We have investigated sea level and surface currents features over the Newfoundland Shelf and Slope using the tandem TOPEX/Poseidon (T/P) and Jason altimetry data (2002-2003). The consistency and error characteristics of T/P and Jason measurements are examined not only in terms of sea level and cross-track current anomalies but also with respect to current anomalies at crossovers and the Labrador Current transport. Nominal absolute currents are constructed by adding the altimetric geostrophic current anomalies to an annual-mean model circulation field. The comparison of the sea level and cross-track current anomalies from January to July 2002 shows overall good agreement between T/P and Jason, with correlation coefficients different from zero at the 5% significance level at almost all locations for sea level and at most locations for currents. Errors are estimated to be 2.5 cm for sea level and 10 cm/s for cross-track current anomalies. Analyses of the current variability at crossovers indicate approximate agreement of T/P and Jason measurements, except for the Northeastern Newfoundland Shelf and Slope probably due to the ice presence during the period. Model-altimetry combined absolute currents are used to estimate near-surface transport associated with the shelf-edge Labrador Current, showing good correlation between T/P and Jason estimates and strong seasonal changes. The cross-track geostrophic current anomalies from September 2002 to December 2003 are used to calculate the root-mean-square (rms) current variability at crossovers and to derive the shelf-edge Labrador Current. The interleaved T/P and Jason observations can better capture the spatial distribution of shelf and slope circulation variability.