Articles | Volume 33, issue 2
https://doi.org/10.5194/npg-33-197-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/npg-33-197-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
21 Apr 2026
Research article |
| 21 Apr 2026
| 21 Apr 2026
Sandy beaches' chaos: shoreline-sandbar coupling inferred from observational time series
Univ Toulouse, Toulouse INP, CNRS, IMFT, Toulouse, France
Sylvain Mangiarotti
Université de Toulouse/UT-CNES-CNRS-IRD-INRAE, Centre d'Études Spatiales de la Biosphère, 18 avenue Édouard Belin, 31401 Toulouse, France
Salomé Frugier
LEGOS (CNRS-IRD-CNES-University of Toulouse), Toulouse, France
Laurent Lacaze
Univ Toulouse, Toulouse INP, CNRS, IMFT, Toulouse, France
Marcan Graffin
LEGOS (CNRS-IRD-CNES-University of Toulouse), Toulouse, France
Rafael Almar
LEGOS (CNRS-IRD-CNES-University of Toulouse), Toulouse, France
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Shorelines often change in rhythmic ways that cannot be explained by storms or climate cycles alone. Using global satellite observations, we show that a repeating two-year shoreline pattern emerges from interactions between seasonal wave activity and delayed shoreline adjustment. This hidden interaction transfers energy across timescales, creating previously overlooked variability, which matters for understanding and anticipating future coastal change.
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Shorelines often change in rhythmic ways that cannot be explained by storms or climate cycles alone. Using global satellite observations, we show that a repeating two-year shoreline pattern emerges from interactions between seasonal wave activity and delayed shoreline adjustment. This hidden interaction transfers energy across timescales, creating previously overlooked variability, which matters for understanding and anticipating future coastal change.
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Short summary
We studied how sandy beaches evolve by tracking the shoreline and offshore sandbars from satellites over many years. By rebuilding beach behavior directly from observations, we show that beaches follow organized but chaotic motion shaped by internal feedbacks. Beyond the seasonal rhythm imposed by waves, shorelines and sandbars exchange energy through the surf zone, producing repeated erosion and recovery cycles with limited predictability, explaining why beaches remain difficult to forecast.
We studied how sandy beaches evolve by tracking the shoreline and offshore sandbars from...
