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Abstract

We present results of a storm surge simulation driven by the atmosphere of a climate model in which a catastrophic shutdown of the Atlantic Meridional Overturning Circulation (AMOC) is induced. Projections of change in the North Atlantic storm tracks in a warming world are highly uncertain and climate models show various responses. Atmospheric storms drive storm surges which are a major component of UK coastal flooding hazard, so it is important to ask how this process may be affected by climate change — not only what change is probable, but also what is possible? Our simulation is a contribution to answering that question. We also consider an ensemble simulation with a high-climate-sensitivity model under Representative Concentration Pathway 8.5 (RCP 8.5). We find significant simulated increases for some sites: up to about 0.4 metres increase (approximately 25%) in the expected annual maximum. In both the AMOC-collapse and the ensemble simulation, the largest projected increases appear at some west coast sites, associated with a growth in the strongest westerly winds. Projected changes on the south-east coast are smaller in the AMOC-collapse simulation and generally negative in the ensemble simulation, which exhibits a decrease in strong northerly winds in addition to the growth in westerlies. Overall, these increases due to atmospheric storminess change are smaller than the expected contribution from mean sea-level rise over the 21st century, but larger than the “high-end” changes due to atmospheric storminess change which were reported in UKCP18.