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[1] Multiyear climate variations influence North Pacific storm intensity and resultant variations in wave energy levels. The timing of these decadal fluctuations and strong El Niño's have had a strong influence on long-term trends. Here we investigate variations in the North Pacific wave power, P W , determined from WAVEWATCH III (WW3) wave model significant wave height, Hs, and peak period data forced by NRA-1 winds spanning the 1948-2008 epoch. Over the entire hindcast, upward trends in Hs and P W , especially in winter, are observed over much of the North Pacific, strongly influenced by an apparent storm intensification after the mid-1970s regime shift. Heightened P W is concentrated in particular regions of the basin, and is associated with increased wave activity during the warm phase of the Pacific Decadal Oscillation (PDO). Wave power events, P E , defined as episodes when Hs exceeded the 90th percentile threshold for at least 12 h, exhibit significant upward trends along much of the U.S. Pacific coast during winter months. Importantly, the hindcast exhibits a recent decrease in P W across much of the North Pacific, in contrast to the long-term increase of P W and Hs. This recent decrease is associated with the prevalent PDO cool phase that developed after the late 1990s. Variability and intensification of coastal P W and P E have important practical implications for shoreline and beach erosion, coastal wetlands inundation, storm-surge flooding, and coastal planning. These considerations will become increasingly important as sea level rises.

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources. gathering end maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB qontrol number. Arlington, VA 22217-5660 SPONSOR/MONITOR'S REPORT "NUMBER(S)12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release, distribution is unlimited. SUPPLEMENTARY NOTES 14.AASTRACTit is a major challenge to determine whether bias in operational global wave predictions is predominately due to the wave model itself (intemal error) or due to eaors in wtinOd forcing (an external error). Another challenge is to characterize bias attributable to errors in wave model physics (e.g., input, dissipation, and nonlinear transfer). In this study, hindcasts and an evaluation methodology are constructed to address these challenges. The bias of the wave predictions is evaluated with constderation of the bias of four different wind forcing fields [two of which are supplemented with the NASA Quick Scatterometer (QuikSCAT) measurements]. It is found that the accuracy of the Fleet Numerical Meteorology and Oceanography Center's operational global wind forcing has improved to the point where it isMuIlikely to be the primary source of error in the center's global wave model (WAVEWATCH-I]I). The hindcast comparisons are specifically designed to minimize systematic errors from numerics and resolution. From these hindcasts, insight into the physics-related bias in the global wave model is possible: comparison to in situ wave data suggests an overall positive bias at northeast Pacific locations and an overall negative bias at northwest Atlantic locations. Comparison of frequency bands indicates a tendency by the model physics to overpredict energy at higher frequencies and underpredict energy at lower frequencies. ABSTRACTIt is a major challenge to determine whether bias in operational global wave predictions is predominately due to the wave model itself (internal error) or due to errors in wind forcing (an external error). Another challenge is to characterize bias attributable to errors in wave model physics (e.g., input, dissipation, and nonlinear transfer). In this study, hindcasts and an evaluation methodology are constructed to address these challenges. The bias of the wave predictions is evaluated with consideration of the bias of four different wind forcing fields [two of which are supplemented with the NASA Quick Scatterometer (QuikSCAT) measurements]. It is found that ...

[1] The turbulent Reynolds stresses in the upper layers of the ocean interact with the vertical shear of the Stokes drift velocity of the wave field to extract energy from the surface waves. The resulting rate of dissipation of wind waves in the global ocean is about 2.5 TW on the average but can reach values as high as 3.7 TW, making it as important as the dissipation of wave energy in the surf zones around the ocean margins. More importantly, the effect of Stokes dissipation is felt throughout the mixed layer. It also contributes to Langmuir circulations. Unfortunately, this wave dissipation mechanism has hitherto been largely ignored. In this note, we present a preliminary estimate of the Stokes dissipation rate in the global oceans based on the results of the WAVEWATCH III model for the year 2007 to point out its potential importance. Seasonal and regional variations are also described. Citation: Kantha, L., P. Wittmann, M. Sclavo, and S. Carniel (2009), A preliminary estimate of the Stokes dissipation of wave energy in the global ocean, Geophys.