This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Tide levels can vary by almost a meter across a single bay, according to a new study that uses decades of satellite images to measure tides at the scale of individual beaches. Researchers at Technische Universität München and the University of Oxford have led the development of a new technique that can estimate tides along the coast at intervals of just 100 meters (330 feet).
This provides a level of local detail that is difficult to capture using existing tide gauges and satellite measurements. The study was published today (Aug. 25) in Communications Earth & Environment. Accurate information about tide levels is important for everything from modeling coastal flood risk and planning navigation to understanding how tides are changing as sea levels rise.
But up to now, our ability to measure tides has been severely limited. Observations from tide gauges are restricted to individual locations, whereas conventional satellite measurements using radar have limited coverage close to shore, with a resolution typically in the region of tens of kilometers. The new approach instead uses satellite photographs of shorelines provided by the Landsat program, run by NASA and the U.S.
This provides the longest continuous space-based record of Earth's land. Crucially, the researchers did not measure the height of the sea directly from the photographs. Instead, the technique uses the beach itself like a giant ruler.
As the tide rises and falls, the waterline moves up and down the sloping beach. Satellite images record where that waterline sits, and, using the slope of the beach, the researchers can translate this movement into changes in sea level. By analyzing measurements of shorelines bordering the Pacific Ocean collected over more than 40 years, the researchers could identify the characteristic repeating rhythms of the tides.
Once these tidal patterns have been identified for a particular location, they can be used to predict the tide there at different points in the past or future and potentially investigate how those patterns are changing over time. Applying the method across countries bordering the Pacific Ocean enabled the researchers to estimate tides for every 100-meter (330-foot) segment of coastline studied. In New Zealand's South Taranaki Bight, for instance, the technique revealed differences in tidal height of almost 1 meter across the approximately 90-kilometer-long (56-mile-long) bay.
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