Using inverted echo sounders to measure dynamic height in the eastern equatorial Pacific during the 1982-1983 El Niño

Document Type

Article

Date of Original Version

1-1-1986

Abstract

We investigate the relationship between the dynamic height anomaly (ΔD) and roundtrip acoustic travel time (τ) measured by inverted echo sounders (IES) in the eastern equatorial Pacific. Salinity variations in the upper 50 m have little effect on τ but do affect surface dynamic height, ΔD0-2500. Consequently, in the eastern equatorial Pacific it is better to interpret τ as a record of dynamic height below 50 dbar, ΔD50-2500. The slope o f the calibration, derived from a regression of ΔD50-2500 with τ, is -60 dyn m s-1. This slopeis controlled mainly by the highly energetic El Niño signal, and is approximately 17% steeper than the simulated IES response to the first baroclinic mode. This difference may be explained by the significant second-vertical-mode component of El Niño, but is small since τ is relatively insensitive to the second vertical mode. As a result, purely first-mode signals (which are likely to dominate IES records because of the low second-mode sensitivity) will still be estimated will with the same calibration. © 1986.

Publication Title, e.g., Journal

Deep Sea Research Part A, Oceanographic Research Papers

Volume

33

Issue

7

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