## 1aAO6. Observation of barotropic-tide relative vorticity in the northwest Atlantic.

### Session: Monday Morning, December 2

### Time: 11:35

**Author: Brian D. Dushaw**

**Location: A. P. L., Univ. of Washington, 1013 NE 40th St., Seattle, WA 98105-6698**

**Author: Bruce M. Howe**

**Location: A. P. L., Univ. of Washington, 1013 NE 40th St., Seattle, WA 98105-6698**

**Author: Peter F. Worcester**

**Location: Univ. of California, La Jolla, CA 92093-0213**

**Author: Bruce D. Cornuelle**

**Location: Univ. of California, La Jolla, CA 92093-0213**

**Author: Kurt Metzger**

**Location: Univ. of Michigan, Ann Arbor, MI 48109**

**Abstract:**

Time series of reciprocal ray travel times were obtained at 350-, 410-, and
670-km ranges in the western North Atlantic during the 1991--1992 Acoustic
Mid-Ocean Dynamics Experiment (AMODE). Transmissions were recorded for
approximately 300 days between six transceivers in a pentagonal array.
Barotropic current along each of the 15 propagation paths is derived from the
difference of reciprocal ray travel times, while ten independent estimates of
areal-averaged relative vorticity are found by integrating current around
triangles in the pentagonal array. The estimated tidal currents are highly
accurate, and tidal relative vorticity at the M[inf 2] frequency is detected.
This vorticity is induced primarily by the stretching of vortex lines by tidal
elevation. Harmonic constants (amplitude, phase) of M[inf 2] tidal vorticity are
about (4--8(plus or minus)2x10[sup -9] s[sup -1], 270(degrees)-320(degrees)(plus
or minus)20(degrees)), while harmonic constants of about (2--3x10[sup -9] s[sup
-1], 300(degrees)-340(degrees)) are predicted using the shallow-water equations.
The measured tidal harmonic constants are compared with those derived from a
global barotropic tidal model.

ASA 132nd meeting - Hawaii, December 1996