Climate change could alter the impact of waves on 50% of the world's coasts

The rise in sea level is not the only way climate change will affect the coastline. Our research, published today in Nature Climate changeThe discovery of a warming planet will also change the waves of the ocean on more than 50% of the world's coasts.

If the climate warms by more than 2 beyond preindustrial levels, southern Australia may see longer waves and further south likely to alter the stability of the coastline.

Scientists are looking at how the waves have shaped our shorelines – forming beaches, spits, lagoons and marine caves – to determine the appearance of the coast in the past. This is our guide to understanding past sea levels.

But often, this research assumes that if the sea level can change, the wave conditions remain the same. This same hypothesis is used to determine the influence of climate change on future coasts. We take into account the future rise in sea level, but we do not know the effect of future changes on the waves that shape the coastline.

Changing waves

The waves are generated by surface winds. Our changing climate will result in changes in global wind patterns (and in turn a change in rainfall patterns, for example by changing the El Niño and La Niña regimes). Likewise, these wind changes will change the conditions of global ocean waves.

In addition to these weather-related wave changes, sea-level rise can alter the way waves move from deep water to shallow water, as well as other changes in coastal depths, such as affected reef systems.

Recent research has analyzed 33 years of wind and wave recordings from satellite measurements and has shown that the average wind speed has increased by 1.5 meters per second and the wave height by 30 cm, an increase 8% and 5% respectively compared to this relatively brief history. record.

These changes have been most pronounced in the Southern Ocean, which is important because the waves generated in the Southern Ocean are spreading in all the ocean basins and moving as far north as up to the present time. at the latitude of San Francisco.

The rise in sea level is only half of the story

Given these historical changes in ocean wave conditions, we looked at how expected future changes in atmospheric circulation, in a warmer climate, would alter wave conditions around the world.

As part of the Coordinated Ocean Wave Climate Project, ten research organizations partnered to examine various global wave models in various future climate scenarios, to determine how waves could change in the future. to come up.

Although we have identified some differences between different studies, we found that if the goal of the Paris 2 agreement was maintained, changes in wave structure would likely remain within the bounds of natural climate variability. .

However, in a status quo climate, where warming continues in line with current trends, the models agreed that we could see significant changes in wave conditions on 50% of the world's coasts. These changes have varied by region.

Less than 5% of the world's coastline is likely to see increasing wave height. These include the southern coasts of Australia and segments of the Pacific Coast of South and Central America.

On the other hand decreases in wave height, forecasts for about 15% of the world's coasts can also modify coastal systems.

But to describe only waves in height is like describing an orchestra simply by the volume at which it plays.

Some areas will see that the wave height remains the same, but their length or frequency changes. This can lead to more force on the coast (or coastal infrastructure), perhaps by seeing the waves rise higher on a beach and increasing wave-induced flooding.

Similarly, waves coming from a slightly altered direction (on 20% of the global coastline) could alter the amount of sand they skirt along the coast – important considerations for the coast's response. Infrastructures built on the coast or offshore are sensitive to these many wave characteristics.

Although each of these wave features is important in itself, our research revealed that about 40% of the world's coasts are likely to see changes in height, period, and direction of waves occurring simultaneously.

Some readers may see intense waves present benefits during their next surf vacation, but this will have far greater consequences for our coastal and offshore environments. The rise in sea level could cost 14 trillion dollars a year in the world by 2100 if we do not reach the goal of a 2 ℃ warming .

How coastlines respond to future climate change will be a response to a complex interaction of many processes, many of which respond to a changing and changing climate. Focusing only on sea level rise and the role played by waves in shaping our coasts is a simplification with high cost potential.

This article is republished from The Conversation under a Creative Commons license. Read the original article.