Bardsey – an island in a strong tidal stream: underestimating coastal tides due to unresolved topography
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Published:2020-11-09
Issue:6
Volume:16
Page:1337-1345
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ISSN:1812-0792
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Container-title:Ocean Science
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language:en
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Short-container-title:Ocean Sci.
Author:
Green J. A. Mattias,Pugh David T.
Abstract
Abstract. Bardsey Island is located at the western end of the Llŷn Peninsula in
northwestern Wales. Separated from the mainland by a channel that is some 3 km wide, it
is surrounded by reversing tidal streams of up to 4 m s−1 during spring
tides. These local hydrodynamic details and their consequences are
unresolved by satellite altimetry and are not represented in regional
tidal models. Here we look at the effects of the island on the strong tidal
stream in terms of the budgets for tidal energy dissipation and the
formation and shedding of eddies. We show, using local observations and a
satellite-altimetry-constrained product (TPXO9), that the island has a large
impact on the tidal stream and that even in this latest altimetry-constrained product the derived tidal stream is under-represented due to the
island not being resolved. The effect of the island leads to an
underestimate of the current speed in the TPXO9 data in the channel of up to
a factor of 2.5, depending on the timing in the spring–neap cycle, and the
average tidal energy resource is underestimated by a factor up to 14. The
observed tidal amplitudes are higher at the mainland than at the island, and
there is a detectable phase lag in the tide across the island; this effect
is not seen in the TPXO9 data. The underestimate of the tide in the TPXO9
data has consequences for tidal dissipation and wake effect computation and
shows that local observations are key to correctly estimating tidal energetics
around small-scale coastal topography.
Publisher
Copernicus GmbH
Subject
Cell Biology,Developmental Biology,Embryology,Anatomy
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