Great Barrier Reef: wave stopper

Scientists from the University of Southampton have concluded that the Great Barrier Reef is a truly effective wave absorber.

The largest coral reef system on Planet Earth extends 2,300 kilometers along the coast of Queensland, in Australia. It is a World Heritage Site since 1981.

A study led by five scientists proved that, despite large gaps between the reefs, the Great Barrier Reef dramatically reduces wave height landward of the coral line.

"There was no evidence that in less porous areas wave heights are lessened. This is because individual reefs, like islands, cast a 'wave shadow' over a large area, so that a matrix of individual reefs is remarkably efficient at reducing waves," explains Shari Gallop, researcher at the University of Southampton.

The porosity level is much lower in the north - where the continental shelf is narrow, and there is extensive reef flats - than it is in the south where the shelf reaches up to 300 kilometers wide, and there are extensive lagoons.

Scientists used a 16-year record of satellite altimeter measurements of wave heights to reach relevant conclusions. It was also proved that landward of the reefs, waves are mostly related to local winds rather than offshore wave conditions.

The study will have an impact on wave modelling near reef systems because models that consider individual reefs only may underestimate the wave reduction potential of a full reef matrix.

"It is of critical importance to know the potential impacts of climate change effects, such as sea level rise and variations in wave conditions, on wave attenuation and current circulation on the Great Barrier Reef. This will aid in the sustainable management of this natural wonder and the surrounding marine national park," adds Roshanka Ranasinghe, professor of Climate Change Impacts and Coastal Risk at the Australian National University.

In the future, scientists will investigate the wave attenuation characteristics over the reef in more detail, using sophisticated numerical modelling.