El Niño controls the evolution of shorelines worldwide

Abstract

Coastal zones are fragile and complex dynamical systems that are increasingly under threat from the combined effects of anthropogenic pressure and climate change. Yet, the key environmental factors that drive regional coastline changes remain poorly quantified. Here, using global satellite derived shoreline positions from 2000 to 2017 and a variety of reanalysis products, we demonstrate that coastlines are under the influence of 3 main drivers: the sea-level, and also ocean waves and fluvial inputs. The relative contribution of each of the drivers vary across the global coastline, with about a third exhibiting a clear dominance of one of the drivers (60% for sea level, 30% for rivers and 10% for waves). Furthermore, by establishing that these environmental forcing are all substantially constrained by El Niño Southern Oscillation (ENSO) at interannual time scales, we derive a conceptual global model of yearly shoreline changes that integrates the complex and diverse planetary climate influence of ENSO on each of these 3 drivers. This model reproduces well the observed shoreline changes with a global correlation of 0.4 and up to 0.6 in the tropical belt. We believe it represents a new solid physical and mathematical framework for understanding ENSO-driven littoral hazards as well as an efficient yet simple approach for their prediction.