Coastline topography and temporal trends in wave exposure.
Davies, Andrew1, Johnson, Mark*,1, 1 Queens University Belfast, Belfast, UK
ABSTRACT- Wave exposure is a textbook structuring factor for intertidal communities. Both climate variability (e.g., North Atlantic Oscillation, NAO) and climate change could therefore affect coastal systems through changes to wave exposure. In the absence of direct measurements of exposure over long periods of time, we used historical wind data in a cartographic exposure model to examine the temporal patterns and spatial scales of variation in wave exposure at 400 sites around Strangford Lough, Northern Ireland. Average annual wind speeds over a 31 year period did not show any significant increase or any correlation with the NAO. Hindcast time series from individual sites were, however, highly divergent. The predicted exposure could vary between a positive or negative relationship with time or the NAO across relatively small spatial scales. Coastline topography, by determining fetch distances, can therefore filter a broad scale signal into a complex pattern of small-scale variability. These results imply that the effects of climatic forcing on wave exposure are likely to be focussed on relatively small areas, while an adjacent stretch of coastline may not experience any temporal change in forcing.
Key words: exposure, climate, topography, fetch
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