Sea-level markers identified in ground-penetrating radar data collected across a modern beach ridge system in a microtidal regime

Sea-level rise has been related to global warming. The modern system on the northern coast of Anholt, Denmark, may well be analogous to other beach ridge systems formed in microtidal regimes and our results should have impact on estimation of past sea-level variation. Ground-penetrating radar data collected across the modern (<30 years old) berm, beach ridge and swale deposits resolve downlapping reflections interpreted to mark sea level at the time of deposition. Existing time series of sea-level data constrain actual sea-level variation. Nineteen readings of sea-level markers made along our profile fluctuate within -0.42 and 0.57 m above present mean sea level, consistent with 95% of the sea-level data. These fluctuations reflect tidal effects and meteorological conditions. Main data uncertainties are well-known and the sea-level markers may be identified with a high degree of confidence.