Multi­year sea level predictions for the Pacific Ocean

Axel Timmermann and Matthew Widlansky, University of Hawai‘i at Mānoa

High surf crashes over breakwater wall on tropical islandHigh surf, made more extreme with rising sea level, can cause increasing damage to infrastructure and ecosystems.

The islands of the tropical Pacific are particularly vulnerable to sea level changes, with rising ocean waters posing an existential threat to many low-lying islands and atolls. However, the rise of the sea is not a uniform process: climatic phenomena, such as the El Niño–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), complicate the picture, changing wind patterns and water concentrations across the Pacific Basin over time and overlaying the regular tidal patterns in complex ways. These climatic phenomena are projected to become stronger, causing a greater frequency of extreme high and low sea level events, which can damage or destroy coastal infrastructure and ecosystems. Accurate forecasting of these events would give local communities time to prepare and mitigate damage. However, modeling sea level variability on shorter time scales, to produce these forecasts, is non-trivial, due to the interaction of multiple climatic processes over a variety of spatial and temporal scales.

Map with scaled colors illustrate patches of higher sea level across the Pacific OceanAn example sea level anomaly forecast through July of 2017.

Our goal was to develop a sea level prediction system for the Pacific Islands on a seasonal time scale, using tide gauge and satellite data as well as new and existing prediction frameworks. The seasonal prediction system is now being presented graphically through an interactive website, allowing us to communicate sea level forecasts to stakeholders at monthly increments, for the next half year, across the Pacific Basin. In developing the forecasts, we incorporated improved models of climatic oscillations into the sea level models to assess the fluctuations they cause in sea level. In addition, we created hind-casts using data from approximately the last 35 years to validate the model outputs before producing forecasts for stakeholders. Our experimental monthly sea level forecasts for each of twelve island stations, along with interactive basin-wide maps can be found at

While the new seasonal sea level predictions are experimental, they help to fill the temporal gap between daily tides and decadal forecasts. This important information will provide a valuable resource for our stakeholders and other groups in the tropical Pacific when planning for increasingly frequent extreme sea level events in the future.

Quick Summary

      Climate change affects long-term sea levels but is also projected to increase the frequency of extreme sea level events over shorter time scales. Seasonal sea level projections can allow local stakeholders to effectively make near-term mitigation and adaptation plans.
      Our goal was to develop a sea level prediction system for the Pacific Islands using a variety of tidal and satellite data as well as climate models, and to assess the effectiveness of this new approach for forecasting sea level changes on a seasonal time scale.
      Government agencies, resource managers, and other stakeholders will be able to use these predictions immediately as part of short and medium term conservation and development planning. Forecasts are available at

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This project was supported by the Pacific Islands Climate Adaptation Science Center (Cooperative Agreement # G13AC00314 from the US Geological Survey). Contact Matthew Widlansky ( for more information on this project. To learn more about climate science at PI-CASC, contact David Helweg at or visit: