Unprecedented rate of coastal destruction predicted

(ORDO NEWS) — Scientists at Imperial College London have found that by 2100, the rate of destruction of rocky coasts and cliffs will be unprecedented due to rising sea levels and will increase by an order of magnitude, much more than previously predicted.

Due to rising sea levels, waves are expected to hit rocky coastlines with greater force, causing accelerated retreat of steep coasts.

To estimate the rate of this process over the past eight thousand years and predict what will happen in the next century, scientists calculated the concentrations of cosmogenic radionuclides in rock samples and combined these data with historical data on coastal retreat to calibrate the model that tracks the evolution of the coast.

The researchers analyzed rocks sampled from gently sloping rock surfaces at two sites in the UK – on the coast of Bideford Bay and on the outskirts of the seaside town of Scarborough, in the village of Sculby.

They determined the content of long-lived isotopes of beryllium-10 (Be10) at various distances from the coastline.

Be10 occurs on the surface of a rock as a result of nuclear reactions induced by cosmic rays, so counting this isotope in relation to other isotopes (beryllium-9, as well as the ratio of aluminum-26 and aluminum-27) shows how long the rocks were exposed by erosion.

To quantify the rate of coastal retreat, rocky bluff positions have been digitized from UK Ordnance Survey maps and recent aerial photographs.

The scientists then built a model that predicts the evolution of the rocky coastline to match both topographic data and radionuclide accumulation.

The model showed that coastal erosion is due to wave weathering, with the rate of coastal erosion nearly matching the rate of sea level rise, i.e. how fast the sea level is rising, not how high it is.

To predict the future rate of retreat of the rocky coastline, scientists turned to the RCP8.5 sea level rise scenario, which assumes that no efforts will be made to reduce carbon dioxide emissions, and sea levels will rise by one meter by 2100.

For Bideford, the model predicts a retreat rate of 5-13 times by 2100, and for Scalby, 2-6 times, to a maximum of 30 centimeters per year.

At the same time, the destruction takes on a tangible character in 2020 for Bideford and in 2030 for Sculby, where the rocks are likely to recede by at least 10-14 and 13-22 meters, respectively.

Predictions of accelerating rock retreat are at least twice as high as early estimates and increase by an order of magnitude from the long-term rate of rock retreat over the past 500 years. For both considered sites, the rate of coastal destruction will be unprecedented for 3-5 millennia.

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