Physical modelling of the response of reef islands to sea-level rise

7 Sea-level rise and increased storminess are expected to destabilise low-lying reef 8 islands formed on coral reef platforms and increased flooding is expected to render them 9 uninhabitable within the coming decades. Such projections are founded on the assumption 10 that islands are geologically static landforms that will simply drown as sea-level rises. 11 Here we present evidence from physical model experiments of a reef island that 12 demonstrates islands have the capability to morphodynamically respond to rising sea 13 level through island accretion. Challenging outputs from existing models based on the 14 assumption that islands are geomorphologically inert, results demonstrate that islands not 15 only move laterally on reef platforms, but overwash processes provide a mechanism to 16 build and maintain the freeboard of islands above sea level. Implications of island 17 building are profound as it will offset existing scenarios of dramatic increases in island 18 flooding. Future predictive models must include the morphodynamic behaviour of islands 19 to better resolve flood impacts and future island vulnerability. 20