Climate change impacts on wave and surge processes in a Pacific Northwest (USA) estuary

Abstract

Total water levels (TWLs) within estuaries are influenced by tides, wind, offshore waves, and streamflow, all of which are uniquely affected by climate change. The magnitude of TWL associated with various return periods is relevant to understanding how the hydrodynamics of a bay or estuary may evolve under distinct climate scenarios. A methodology for assessing the hydrodynamic response of a small estuary under major boundary condition perturbations is presented in this study. The coupled Advanced Circulation (ADCIRC) and Simulating Waves Nearshore (SWAN) model was used to simulate wave and water elevation conditions within Tillamook Bay, OR, USA for two long-term scenarios; 1979-1998 and 2041-2060. The model output provided multidecadal time series of TWLs for statistical analysis. Regional climate data from the North American Regional Climate Change Assessment Program (NARCCAP) were used to drive streamflow modeling (MicroMet/SnowModel/HydroFlow) and meteorological forcing within ADCIRC-SWAN. WAVEWATCH III, which was forced with global climate data from the Community Climate Science Model (CCSM, a contributing model to NARCCAP), was used to produce open boundary wave forcing. Latitudinal and seasonal gradients were found in TWLs associated with varying return periods for both the hindcast and forecast. Changes in TWLs from hindcast to forecast included the sea level rise component and were also modulated by changes in boundary conditions.

Projected wave conditions in the Eastern North Pacific under the influence of two CMIP5 climate scenarios

“…The latter observation is expected since a best-fit conditional relationship between H s and T p was imposed. The findings are consistent with previous studies that have assessed changes in conditionally-derived extreme T p (e.g., Cheng et al, 2015).…”

“…All winds were available as 10 m neutrally-stable fields and similar to many previous studies (Cheng et al, 2015;Dobrynin et al, 2012), no bias adjustments were made. It is noted here that Graham et al (2013) found marked improvement when applying wind bias adjustments to CMIP3 wind fields.…”

“…In coastal design applications, a conditional relationship is typically used (e.g. Cheng et al, 2015) to avoid the occurrence of physically unrealistic conditions. In this study, we evaluate changes of extreme T p and D m in both ways: as independent and conditionally-varying parameters.…”

Spatial and Temporal Variability in Tidal Range: Evidence, Causes, and Effects

“…The studies in Table 3 are focused on, or explicitly give results for, tidal amplitude changes. It should be noted that there are many more studies (e.g., [8,13,49]) that consider a more holistic approach to changing extreme water elevations, of which tides are a component. Studies that do not explicitly provide information on the changes to tidal amplitudes are not included in Table 3.…”

Improvements for the Western North Atlantic, Caribbean and Gulf of Mexico ADCIRC Tidal Database (EC2015)

“…Small-scale regional hydrodynamic models are widely used to study many varied physical processes such as sediment transport [1][2][3]; storm surge inundation [4][5][6]; real-time surge forecast systems [7][8][9][10]; sea level rise [11][12][13][14]; passive fish and larval transport, as well as coupled ecological behavior [15][16][17]; combined hydrologic and hydrodynamic processes [9,18]; passive transport of oil spills [19] and coupled hydrodynamic-marsh interactions with biological feedback [20]. Each of these complex applications requires reliable tidal boundary forcing in order to provide accurate results.…”