Newfoundland Basin sea-level variability from TOPEX/POSEIDON altimetry and inverted echo sounder ‐ bottom pressure measurements

Abstract

A collaborative deep-sea study of the North Atlantic Current in the Newfoundland Basin by the University of Rhode Island and the Bedford Institute of Oceanography took place during 1993‐1995. The study included an array of three collocated bottom pressure sensors and inverted echo sounders (PIES) which spanned a 320-km cross section of the North Atlantic Current. The bottom-moored inverted echo sounders measure full-depth acoustic travel time and provide an estimate of geopotential height. The sum of the geopotential height and the depth equivalent of bottom pressure gives an estimate of sea-level height. Time variations in PIES sea level are compared with measurements by the TOPEX/POSEIDON (T/P) altimetric satellite during the 22-month time period from August 1993 to July 1995. The three sites show remarkably different baroclinic structures, energy levels, and space-time characteristics. Time scales are such that 86‐95% of the sub-inertial period sea-level variability at the three sites is not aliased by the approximately 10-day T/P repeat period sampling. The T/P spatial sampling, however, is insufficient for mapping the mesoscale variability. The PIES and T/P sea-level time series were highly correlated for two cases where the nearest T/P measurement points were within 15‐30 km of the PIES site. A third site with the closest T/P measurement nearly 100 km removed was essentially uncorrelated with any T/P measurements. Parametric space‐time correlation models based on the T/P and PIES sea-level measurements are developed for each site to quantify the limitations of the T/P sampling. These examples illustrate the requirement for multi-satellite altimetric missions to provide more complete spatial coverage in this and similar western boundary current regions.