Why Are Waves Getting Taller?

The world’s largest waves are growing even taller than ever before, according to a new study carried out by researchers at the University of Melbourne and Hasanuddin University in Makassar, Indonesia. By collating the data collected for more than three decades, the team behind the study were able to determine that waves had grown by up to 30cm or more since 1985.

Although the authors of the study were reluctant to prescribe a definitive explanation for the growth in wave height, they did indicate that it was most likely caused by faster wind speeds in the area. This itself is believed to be brought on by the increased incidence of extreme weather phenomena caused by manmade climate change. While faster wind speeds could potentially boost a thriving renewable energy economy through the work of offshore wind farms, they could spell serious danger for coastal communities.

The highest of the high

The Southern Ocean is notorious for the violence of its storms and the excessive height of its waves; just last year, the largest wave ever recorded was noted at a staggering 78 feet high. The new study from Australia and Malaysia pored over datasets stretching back 33 years to find whether those waves had increased in that period and found alarming results.

The body of data had been collected by satellites, which recorded the height of waves in the area by sending pulses of energy down to Earth and recording the amount of time it took for them to be reflected back. The shorter the time, the higher the wave. Meanwhile, other instruments are capable of measuring the reflectivity of the surface of the water, which gives insight into how fast wind speeds are at the time as well.

Minimising discrepancies

Unfortunately, this latter dataset was confused somewhat due to the fact that different satellites can deliver differing estimates on wind speed. To try to eliminate these discrepancies as much as possible, the team cross-referenced the original data against that provided by an independent network of buoys on the surface of the water, to gain as precise a reading on wind speed as they could.

Their findings showed that average wind speeds all over the world have increased by between 1cm/s to 2cm/s. However, the top 10% of wind speeds in the Southern Ocean showed a much more pronounced increase of up to 5cm/s. This, in turn, had a knock-on effect on wave heights in the area; while average wave heights have grown by just 0.3cm/year, the top 10% have leapt up by 1cm/year. Over the 33-year period, that equates to an increase of 33cm.

Climate change the culprit?

As our ability to predict extreme weather events continues to improve, so too does our knowledge about what may be causing them. It’s impossible to say with certainty that climate change is behind the faster wind speeds found in the Southern Ocean, but the authors believe it is the most likely explanation. “These are the secondary effects of climate change, not the obvious ones like sea level rise,” explains Ian Young, the physical oceanographer from the University of Melbourne who worked on the study. “This is where a lot of the research emphasis is now being placed.”

Regardless of the cause, faster winds and higher waves could spell trouble for coastal communities which already suffer from damaging storms. If climate change is allowed to continue unchecked, it’s likely that the storms will only become more harmful going forwards.