Climate change may change the way ocean waves impact 50% of the world’s coastlines


Mark Hemer, CSIRO; Ian Young, University of Melbourne; Joao Morim Nascimento, Griffith University, and Nobuhito Mori, Kyoto University

The rise in sea levels is not the only way climate change will affect the coasts. Our research, published today in Nature Climate Change, found a warming planet will also alter ocean waves along more than 50% of the world’s coastlines.

If the climate warms by more than 2℃ beyond pre-industrial levels, southern Australia is likely to see longer, more southerly waves that could alter the stability of the coastline.

Scientists look at the way waves have shaped our coasts – forming beaches, spits, lagoons and sea caves – to work out how the coast looked in the past. This is our guide to understanding past sea levels.




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Rising seas threaten Australia’s major airports – and it may be happening faster than we think


But often this research assumes that while sea levels might change, wave conditions have stayed the same. This same assumption is used when considering how climate change will influence future coastlines – future sea-level rise is considered, but the effect of future change on waves, which shape the coastline, is overlooked.

Changing waves

Waves are generated by surface winds. Our changing climate will drive changes in wind patterns around the globe (and in turn alter rain patterns, for example by changing El Niño and La Niña patterns). Similarly, these changes in winds will alter global ocean wave conditions.




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Further to these “weather-driven” changes in waves, sea level rise can change how waves travel from deep to shallow water, as can other changes in coastal depths, such as affected reef systems.

Recent research analysed 33 years of wind and wave records from satellite measurements, and found average wind speeds have risen by 1.5 metres per second, and wave heights are up by 30cm – an 8% and 5% increase, respectively, over this relatively short historical record.

These changes were most pronounced in the Southern Ocean, which is important as waves generated in the Southern Ocean travel into all ocean basins as long swells, as far north as the latitude of San Francisco.

Sea level rise is only half the story

Given these historical changes in ocean wave conditions, we were interested in how projected 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 organisations combined to look at a range of different global wave models in a variety of future climate scenarios, to determine how waves might change in the future.

While we identified some differences between different studies, we found if the 2℃ Paris agreement target is kept, changes in wave patterns are likely to stay inside natural climate variability.

However in a business-as-usual climate, where warming continues in line with current trends, the models agreed we’re likely to see significant changes in wave conditions along 50% of the world’s coasts. These changes varied by region.

Less than 5% of the global coastline is at risk of seeing increasing wave heights. 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 heights, forecast for about 15% of the world’s coasts, can also alter coastal systems.

But describing waves by height only is the equivalent of describing an orchestra simply by the volume at which it plays.

Some areas will see the height of waves remain the same, but their length or frequency change. This can result in more force exerted on the coast (or coastal infrastructure), perhaps seeing waves run further up a beach and increasing wave-driven flooding.

Similarly, waves travelling from a slightly altered direction (suggested to occur over 20% of global coasts) can change how much sand they shunt along the coast – important considerations for how the coast might respond. Infrastructure built on the coast, or offshore, is sensitive to these many characteristics of waves.

While each of these wave characteristics is important on its own, our research identified that about 40% of the world’s coastlines are likely to see changes in wave height, period and direction happening simultaneously.

While some readers may see intense waves offering some benefit to their next surf holiday, there are much greater implications for our coastal and offshore environments. Flooding from rising sea levels could cost US$14 trillion worldwide annually by 2100 if we miss the target of 2℃ warming.




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How coastlines respond to future climate change will be a response to a complex interplay of many processes, many of which respond to variable and changing climate. To focus on sea level rise alone, and overlooking the role waves play in shaping our coasts, is a simplification which has great potential to be costly.


The authors would like to acknowledge the contribution of Xiaolan Wang, Senior Research Scientist at Environment and Climate Change, Canada, to this article.The Conversation

Mark Hemer, Principal Research Scientist, Oceans and Atmosphere, CSIRO; Ian Young, Kernot Professor of Engineering, University of Melbourne; Joao Morim Nascimento, PhD Candidate, Griffith University, and Nobuhito Mori, Professor, Kyoto University

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

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We built a network of greenhouses and rain shelters to simulate what climate change will do to soils



Mimicking the future.
Joe Fontaine, Author provided

Anna Hopkins, Edith Cowan University; Christina Birnbaum, Deakin University; Joe Fontaine, Murdoch University, and Neal Enright, Murdoch University

As most of the science community knows, the climate emergency is here now. Weather extremes such as droughts and heatwaves are increasing in frequency and intensity and are measurably exacerbated by climate change. The significant impacts of these extremes are well documented on both our native terrestrial and marine ecosystems.

Less documented is what’s happening beneath our feet. Changes below the ground are hard to measure, so most previous research has focused on what can be readily observed above the ground, such as tree deaths.

But soil is a crucial element of the climate system, being the second-largest store of carbon after the ocean. Climate change can result either in an increase in soil carbon storage (through plant growth), or in more carbon being released into the atmosphere (through plant death). Soil is also full of microbes such as fungi, bacteria and algae, and these organisms play a vital role in determining how well an ecosystem functions and how it responds to changes in climate.




Read more:
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We have completed one of the first studies to examine the impact of drought and warmer temperatures on living organisms below the ground (known as the soil biota), in biodiverse shrublands in Western Australia, near Eneabba, about 280km north of Perth. These areas are already suffering immense climate-related stress above ground as a result of rising temperatures and longer droughts. This is making these ecosystems extremely vulnerable with many plant species facing likely extinctions in the future.

We documented significant impacts for soil biota too, with implications for the health of ecosystems in regions that are expected to experience increased drought and climate warming in the future.

We found that lower rainfall and higher temperatures are likely to affect the overall composition of soil fungal communities, and that some groups may be lost altogether.

We saw an increase in the number of fungal species that cause plant disease, whereas many common and beneficial fungi declined in response to warming and drying. These beneficial fungi contribute to many important ecosystem processes, such as boosting plant growth, and ensuring that plants get enough water and nutrients such as phosphorus.

Western Australia’s shrublands are already suffering climate stress.
Joe Fontaine, Author provided

How we did it

We built specially constructed shelters and mini-greenhouses over plots of shrubland 4x4m in size, to recreate the drier, hotter weather conditions predicted to arise between now and the end of the 21st century. This allowed us to assess how the projected future climate will affect the composition, richness and diversity of soil fungi.

Our rain shelters consisted of a roof made of gutters, widely spaced so as to intercept about 30% of the rain that fell on the plot and funnel it away.




Read more:
We need more carbon in our soil to help Australian farmers through the drought


To study the impact of increased temperature, we enclosed separate plots on the same sites in walls made of transparent fibreglass sheeting. These worked in a similar way to a greenhouse, by reducing air flow and increasing daytime temperatures inside the shelter by 5.5℃.

We left the rain shelters and mini-greenhouses in place for four years. Then we collected soil from each plot and examined the fungi in the soil using DNA sequencing techniques.

How to engineer an artificial drought.
Joe Fontaine, Author provided

Our study revealed that it is vital to understand patterns of below-ground ecosystems as well as those we can see, if we are to accurately predict how our shrublands and other valuable ecosystems will be altered by climate change.The Conversation

Anna Hopkins, Lecturer in conservation biology and microbial ecology, Edith Cowan University; Christina Birnbaum, Honorary Fellow, Deakin University; Joe Fontaine, Lecturer, Environmental Science, Murdoch University, and Neal Enright, Professor in Plant Ecology, Murdoch University

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