Evaluation of Global Wave Climate Based on the JMA/MRI-AGCM Climate Change Projection

Abstract: In this study global wave climates for present and future climates are simulated with the WAM model, based on wind fields from the JMA/MRI-AGCM3.2 climate projection. The projected wave fields are analysed and compared for the two periods of 1979-2003 and 2075-2099, and climate change induced differences are identified. It is found that the wave climate is strongly dependent on latitude, with the largest waves, as well as most significant seasonal variations, located at the mid to high latitude regions. These areas are also where the climate induced changes from present to future climate are most noteworthy. The largest increases of significant wave height of approximately +5%, is experienced in the southern parts of the Indian, Pacific and Atlantic Oceans as well as in the Antarctic Ocean. The largest decreases are of the same order, and found to the northern Atlantic Ocean. In addition, a slightly smaller but widespread decrease is seen in the tropical storm affected region around Japan, in the western Pacific Ocean. In contrast to this reduction of the everyday wave climate, an evaluation of the annual maximum waves at this location indicates that the extreme wave climate might become more severe due to the projected climate change. In the central and lower parts of the mid latitude regions the projected wave climate remain fairly stable and show only minor changes between present and future climates. It is noted that the processes behind the everyday wave climate differ significantly from those causing extreme events, and that the phenomena should therefore be evaluated separately. Since this study focuses on the climate change induced effects on the wave climate under normal weather conditions, it is recommended that in future research evaluate the extremes in a more thorough manner. For that analysis using the full potential of the JMA/MRI-AGCM high-resolution wind fields output is recommended.