Characterization of the principal tidal current constituents on the Texas‐Louisiana shelf

Abstract

We analyzed 81 current meter records of varying lengths (3 to 30 months) to describe the principal diurnal (O1, K1, P1, and Q1) and semidiurnal (S2, M2, K2, and N2) tidal current constituents on the Texas‐Louisiana continental shelf. The Louisiana‐Texas Shelf Physical Oceanography Program (LATEX) had 81 current meters at 31 sites and varying depths from April 1992 to December 1994. The local inertial period range across the shelf (24.4 hours to 26.2 hours) and thermal diurnal cycling during the summer season make it difficult to estimate the diurnal tidal constituents. Dominant tidal modes on the shelf are K1, O1, and M2. Absolute and relative energy contained in each tidal constituent varies with shelf location. The northeast corner of the shelf, near Atchafalaya Bay, has the largest tidal currents with maximum surface current amplitudes (at 3 m depth) of about 9 cm s−1, while typical maximum tidal surface currents near the shelf break are between 1 and 2 cm s−1 for each of the K1, O1, and M2 components. In general, the surface tidal currents decrease in magnitude as water depth increases toward the shelf break, although the semidiurnal components are amplified more at midshelf locations than the diurnal components. Examination of tidal ellipses at different depths suggests that the M2 tide has less vertical structure, while the diurnal tides exhibit more shear, particularly at the more shallow locations. Sea surface height constituents estimated at five locations along the Texas‐Louisiana coast are in agreement with historical values.