DOI: 10.17603/ds2-59cy-n043
title: El Niño-Southern Oscillation and Pacific Decadal Oscillation drive seasonal and interannual shoreline position anomalies in the U.S. Pacific Northwest sandy beaches, in Coastal Erosion Hazard Monitoring in the U.S. Pacific Northwest

description: This project investigates the causal relationships between major Pacific Basin climate variability modes, i.e., the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO), and shoreline position dynamics along the U.S. Pacific Northwest sandy beaches, spanning approximately 750 km of Oregon and Washington coastline. Leveraging four decades (1984-2024) of high-resolution satellite-derived shoreline observations from Landsat missions, the research employs advanced statistical methods, including Convergent Cross Mapping (CCM), a novel causal inference technique applied for the first time to coastal morphology, to move beyond correlation-based analyses and establish directional causal linkages between climate drivers and coastal change. Key findings of this project demonstrate that strong El Niño years are characterized by erosion across 75.1% of the analysed beach extents, while strong La Niña years exhibit predominantly accretional behavior across 73.4% of the analysed beach extents, with both ENSO and PDO exerting statistically significant driving control on interannual shoreline variability, particularly affecting alongshore sediment transport patterns, and water level fluctuations playing a critical complementary role alongside wave energy variations. This comprehensive dataset can be reused for a wide range of applications, including coastal hazard vulnerability assessments, climate impact projections, morphodynamic (shoreline) model calibration and validation, long-term coastal management planning, and comparative studies of teleconnections between large-scale climate patterns and regional coastal responses. The project is unique in its spatial and temporal resolution—covering 40 years (1984-2024) across 750 km of coastline with over 10,000 transects at 50-meter alongshore spacing—its application of causal inference methods to coastal geomorphology, its explicit resolution of littoral cell-scale dynamics including cross-shore migration, beach rotation, and breathing modes, and its simultaneous quantification of both ENSO and PDO influences on seasonal and interannual timescales within a morphologically complex and hydrodynamically challenging coastal region previously excluded from global-scale analyses. The primary audience includes coastal scientists and geomorphologists, climate researchers investigating teleconnections and Earth system dynamics, coastal engineers and managers interested in erosion mitigation and adaptation strategies, environmental planners developing climate resilience policies, and graduate students and researchers seeking high-quality, long-term coastal datasets for advancing understanding of climate-driven coastal change processes. The research based on this project has been accepted for publication and is being prepared for final production in PNAS Nexus under the title "ENSO and PDO drive shoreline position anomalies in the U.S. Pacific Northwest."