When Tides Run Dry: Exploring an Overlooked Coastal Disturbance and Its Climate Connections.

Weakening polar temperature gradients are associated with increasingly persistent weather patterns, increasing the risk of extreme environmental events. While disturbances, such as marine heat waves, have received growing attention, others, including negative sea level anomalies, remain understudied. Prolonged and extreme low-water conditions can impose strong physiological stress on coastal organisms and alter community structure, yet such events lack a consistent operational definition, limiting their detection and assessment. Here, we define and quantify extreme negative sea level anomalies, termed Dry Tides, as anomalous (below the 10th percentile of historical records) and prolonged (> 5 days) water level depressions that restrict submersion of intertidal and shallow subtidal organisms. Using a global analysis of tidal gauge records from 25 locations, we show that Dry Tides occur worldwide but are most frequent and intense in microtidal and semi-enclosed systems. These events typically last one to 2 weeks, with extreme cases up to 97 days and reaching amplitude depressions of up to 37% of the local tidal range. Contrary to expectations based on trends in other climate-related disturbances, we detect no consistent increase in Dry Tide frequency or intensity over the past three decades, which, together with their dependence on tidal regime, suggests that Dry Tides arise from interacting physical drivers rather than a single cause. We discuss the ecological relevance of Dry Tides in light of existing ecological literature, provide tools for their identification using local tide-gauge databases, and highlight priorities for integrating physical and ecological observations to better assess their impacts under ongoing climate change.