Infrastructure protectionLower waves' impact on coastal communities uncertain
Coastal impacts of climate change studies have predominantly focused on the influence of sea-level rise and, until now, not focused on how changing wave conditions will impact the coastal zone in a changing climate. Scientists note, though, that waves are dominant drivers of coastal change in these sandy environments, and variability and change in the characteristics of surface ocean waves can far exceed the influences of sea-level rise in such environments. Since warmer oceans will see lower waves, the effect of warming on coastal communities is uncertain.
Climate scientists studying the impact of changing wave behavior on the world’s coastlines are reporting a likely decrease in average wave heights across 25 percent of the global ocean.
In some of the first climate simulations of modeled wave conditions, they also found a likely increase in wave height across 7 percent of the global ocean, predominantly in the Southern Ocean.
A CSIRO release reports that these findings are derived from a study which seeks to understand potential impacts on coasts from climate change driven wind-wave conditions. The study was published in Nature Climate Change.
Lead author, CSIRO researcher Dr. Mark Hemer, said that 20 percent of the world’s coastlines are sandy beaches which are prone to natural or man-made changes. It is estimated that 10 percent of these sandy coasts are becoming wider as they build seawards, 70 percent are eroding, and the remaining 20 percent are stable. Around 50 percent of Australia’s coast is sand.
“Waves are dominant drivers of coastal change in these sandy environments, and variability and change in the characteristics of surface ocean waves (sea and swell) can far exceed the influences of sea-level rise in such environments.
“If we wish to understand how our coasts might respond to future changes in climate then we need to try and understand how waves might respond to the projected changes in global atmospheric circulation seen as shifts in storm frequency, storm intensity and storm tracks,” Hemer stated.
Hemer explained that coastal impacts of climate change studies have predominantly focused on the influence of sea-level rise and, until now, not focused on how changing wave conditions will impact the coastal zone in a changing climate.
He said sea-level rise is likely to have considerable influence along much of the world’s coastlines.
With such poor understanding of how changes in waves and other coastal processes will also influence shoreline position, however, it is difficult to attribute a level of future risk to the coast under a warmer climate.
The study compared results from five research groups from Australia, the United States, Japan, Europe, and Canada. Each group used different modeling approaches to develop future wave-climate scenarios.
“While we find agreement in projected change in some parts of the world’s oceans, considerable uncertainty remains. We’re continuing to quantify the dominant sources of variation with the latest generation of climate models which will be used in the up-coming Intergovernmental Panel on Climate Change reports,” Hemer said.
He said climate is one of several mostly human-driven factors influencing coastline change.
— Read more in Mark A. Hemer et al., “Projected changes in wave climate from a multi-model ensemble,” Nature Climate Change 3 (13 January 2013): 471–76 (doi:10.1038/nclimate1791)
