New Tools for Gauging Estuarine Dynamics

Estuaries — vital nurseries for sea life in the Pacific Northwest — provide water filtration and habitat protection for the many species that live in and around them.

To better understand how climate change will alter the dynamics of tides, winds, ocean waves and stream flows in these critical ecosystems, a new tool was designed by a group of Oregon State University researchers, including Tiffany Cheng and David Hill. In a recent paper published in the Journal of Geophysical Research: Oceans, they introduce their new approach for assessing the complex hydrodynamics of Tillamook Bay, Oregon.

Assessing changes in Pacific Northwest estuaries is complicated by their unique characteristics. The region’s offshore wave climate is relatively strong. Also, extreme winds and precipitation are common, especially in the winter. Finally, there is substantial variability in precipitation events from year to year and decade to decade.

The paper describes a new method for calculating an estuary’s total water level. The researchers used a combined, or coupled, implementation of two models to simulate the wave and storm-surge statistics in Tillamook Bay for two periods, one historic (1979 to 1998) and one future (2041 to 2060). The coupled model incorporated data on tides (amplitudes and phases), winds (velocity components), sea-level surface pressure, offshore waves and stream flow (determined by weather, snowmelt and runoff).

The coupled model showed that breaking ocean waves are a primary driver of changes in total water levels.

A similar study is underway in Coos Bay, Oregon, which should provide additional insight into the potential evolution of Pacific coast estuaries in the 21st century.

Authors’ Caveats: The authors note several limitations of their study: (1) Only one global/regional climate model pairing was used; (2) the present coupled model does not account for several important processes (water temperature and upwelling, for instance); and (3) only one estuary was examined. These limitations were due, in large part, to a lack of computing resources.

Our Editorial Opinion: This paper illustrates a new, unique methodology for studying the impacts of climate change on estuaries. Even given its limitations, this methodology should be useful for projecting future flooding hazards in and along coastal waterways.

Citation: Cheng, T. K., D. F. Hill, J. Beamer, & G. Garc’ıa-Medina (2015), Climate change impacts on wave and surge processes in a Pacific Northwest (USA) estuary, J. Geophys. Res. Oceans120, 182–200. doi:10.1002/2014JC010268
Photo Caption: Google Earth map of Tillamook Estuary.

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