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Introduction

Research of global climate change due to greenhouse effects on the earth’s environment is changing from understanding phenomena to impact assessment, mitigation and adaptation strategies for future development of human society. Sea-level rise has been observed at a rate of 1.7 mm ± 0.3 mm/yr from 1870 to 2004 and a significant acceleration of sea-level rise was observed in the last ten years (Church and White, 2006). The major source of the sea-level rise is thermal expansion of sea water temperature increase, thus the sea-level rise is a static side issue of climate change influence. Sea-level rise greatly impacts human activity near the coastal zone (IPCC, 2007) and simply exacerbates the vulnerability of coastal regions to other physical processes (e.g. storm surges, storm waves). Another direct influence of sea-level rise is the inundating of low level coastal areas which is of concern.

On the other hand, ocean waves and storm surges of future climate are also expected to change characteristics from the present climate and are the dynamic side issue of climate change. It is necessary to seriously consider the impacts of these dynamic phenomena for coastal disaster prevention and reduction, if extreme weather events will become stronger than those in the present climate. For example, the North Atlantic observed wave data shows 5 cm/yr increase of annual maxima for the last 40 years (Wang and Swail, 2002). The wave hindcasts in the Atlantic Ocean show more significant wave height increase in the region off the Canadian coast and the northwest of Ireland but less significant change in the North Sea and in the region off the Scandinavian coast (Wang and Swail, 2002). In addition, long-term changes of storm waves and surges are important for infrastructures near the coastal zone. For example, a coastal breakwater design is basically determined by the wave pressure of the maximum wave condition, the so-called design wave, for durable period and the wave pressure is proportional to the wave height. Moreover, coastal erosion is another critical issue, where more than 70% of sandy beaches around the world are presently erosional. Equilibrium condition of coastal beach profile depends on seasonal or annual wave height, period and direction. The projection of future change on coastal erosion is insufficient due to information deficiencies on changes in waves and coastal currents. Therefore, future ocean wave climate change will have significant impacts on extreme and daily coastal environments. These influences will be at greatest risk at coastal areas, especially in the heavily populated mega delta regions of East, South-East and South Asia. The future coastal environmental changes give a big influence to these regions, directly.

The future wave climate projection has been conducted by a few researchers (e.g. Hemer et al., 2006). These studies have shown an increase in wave height due to increased wind speeds associated with mid-latitude storms in many regions of the mid-latitude oceans. Zhang et al. (2004) and Wang and Swail (2006) made statistical projections of global wave height from the empirical relationships between sealevel pressure and significant wave height. Furthermore, the dynamical regional wave climate projections has been carried out in Europe and North America but there is no dynamical global wave climate projection at present. This study projects future wave climate and analyzes differences between present and future ocean wave climate models based on the high-resolution atmospheric General Circulation Model (GCM) developed by the Japanese Meteorological Research Institute and Japan Meteorological Agency (MRI-JMA) and the global wave model. The averaged and extreme ocean wave climate changes on both global and regional scales are discussed.

This project is part of Innovative Program of Climate Change Projection for the 21st Century which is supported by Japanese government.

Collaborators

  • Tomya Shimura, DPRI
  • Hajime Mase, DPRI
  • Tomohiro Yasuda, DPRI
  • Sota Nakajo, DPRI

Research period

This project started in 2008 and supported by Innovative Program of Climate Change Projection for the 21st Century supported by Japanese government.

Results

Direct projection of sea surface wind and wave climate change

Following netcdf data set are one of our results based on the latest version of MRI/JMA AGCM model. If you want to know in detail please ask me directly. These data set are basically free but please refer to following references when you use the data set.

Hs

  • Annual averaged data
  • 50 years return period data

U10

References

  1. Mori, N., T. Yasuda, H. Mase, T. Tom and Y. Oku (2010) Projection of extreme wave climate change under the global warming, Hydrological Research Letters, Vol.4, pp.15-19. (doi:10.3178/hrl.4.15)