The Accuracy of Tide-Gauge Measurements at Subtidal Frequencies

Abstract

The accuracy of subinertial sea level, as measured by tide gauges in the Southern California Bight, is investigated. Sea level differences formed from tide gauges separated by less than 50 km are examined. The observed differences give an upper bound an errors in the sea level data, provided errors at each station are uncorrelated with each other and with the true sea level signal. Sea level measurements at the San Diego and La Jolla tide gauges are also compared with simultaneous bottom pressure measurements made on the shelf 25 km north of San Diego. Both comparisons sunset that rms errors in tide-gauge measurements of sea level are order 1.5 cm. Approximately half the observed error variance has time scales of 1 month and is due, in part, to inaccuracies in determining reference levels.