The late December 2024 North Pacific swells on South American coasts

In late December 2024, intense swells originating from persistent weather systems in the North Pacific Ocean impacted the Pacific coasts of South America. This study investigates their source, propagation, and impacts along the South American coastlines, placing the event within a broader climatological context. The analysis spans between December 15th, 2024, and January 15th, 2025, with a focus on extreme swells occurring in late December. To assess the event at both regional and local scales, we integrate data from tide gauges, wave buoys, wave hindcasts, and anecdotal evidence from online media. Our findings indicate that these swells were extreme both in terms of the wind source and wave characteristics throughout the Pacific Ocean. A latitudinal decay in wave heights near the source was accompanied by a progressive increase in peak periods due to frequency dispersion, reaching nearly 25 s on the west coast of South America. While sea-level records generally exhibited small non-tidal residuals, a few tide gauges experienced unusually large anomalies attributed to local conditions. The event caused four casualties in Ecuador and Chile, alongside widespread flooding, severe infrastructure damage, beach erosion, and port closures. The most impacted areas were sites with no or partial shelter to northwestern swells, where the natural protection from prevailing southwestern swells had historically supported tourism, industry, and fisheries. Our results highlight that, while these long-period swells are highly predictable, their impacts remain unavoidable due to the increasing exposure of coastal communities.