Document Type

Article

Publication Date

2019

DOI

10.1029/2018rg000636

Publication Title

Reviews of Geophysics

Volume

58

Issue

1

Pages

e2018RG000636 (1-39)

Abstract

Scientists and engineers have observed for some time that tidal amplitudes at many locations are shifting considerably due to nonastronomical factors. Here we review comprehensively these important changes in tidal properties, many of which remain poorly understood. Over long geological time scales, tectonic processes drive variations in basin size, depth, and shape and hence the resonant properties of ocean basins. On shorter geological time scales, changes in oceanic tidal properties are dominated by variations in water depth. A growing number of studies have identified widespread, sometimes regionally coherent, positive, and negative trends in tidal constituents and levels during the 19th, 20th, and early 21st centuries. Determining the causes is challenging because a tide measured at a coastal gauge integrates the effects of local, regional, and oceanic changes. Here, we highlight six main factors that can cause changes in measured tidal statistics on local scales and a further eight possible regional/global driving mechanisms. Since only a few studies have combined observations and models, or modeled at a temporal/spatial resolution capable of resolving both ultralocal and large-scale global changes, the individual contributions from local and regional mechanisms remain uncertain. Nonetheless, modeling studies project that sea level rise and climate change will continue to alter tides over the next several centuries, with regionally coherent modes of change caused by alterations to coastal morphology and ice sheet extent. Hence, a better understanding of the causes and consequences of tidal variations is needed to help assess the implications for coastal defense, risk assessment, and ecological change.

Rights

© American Geophysical Union

"AGU allows authors to deposit their journal articles if the version is the final published citable version of record, the AGU copyright statement is clearly visible on the posting, and the posting is made 6 months after official publication by the AGU."

Original Publication Citation

Haigh, I. D., Pickering, M. D., Green, J. A. M., Arbic, B. K., Arns, A., Dangendorf, S., . . . Woodworth, P. L. (2020). The tides they are a-changin': A comprehensive review of past and future nonastronomical changes in tides, their driving mechanisms, and future implications. Reviews of Geophysics, 58(1), e2018RG000636. doi:10.1029/2018rg000636

ORCID

0000-0002-3679-5234 (Dagendorf)

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