Thomas Mortlock, Macquarie University; Itxaso Odériz, Universidad Nacional Autónoma de México (UNAM); Nobuhito Mori, Kyoto University, and Rodolfo Silva, Universidad Nacional Autónoma de México (UNAM)
Sea level rise isn’t the only way climate change will devastate the coast. Our research, published today, found it is also making waves more powerful, particularly in the Southern Hemisphere.
We plotted the trajectory of these stronger waves and found the coasts of South Australia and Western Australia, Pacific and Caribbean Islands, East Indonesia and Japan, and South Africa are already experiencing more powerful waves because of global warming.
This will compound the effects of sea level rise, putting low-lying island nations in the Pacific — such as Tuvalu, Kiribati and the Marshall Islands — in further danger, and changing how we manage coasts worldwide.
But it’s not too late to stop the worst effects — that is, if we drastically and urgently cut greenhouse gas emissions.
An energetic ocean
Since the 1970s, the ocean has absorbed more than 90% of the heat gained by the planet. This has a range of impacts, including longer and more frequent marine heatwaves, coral bleaching, and providing an energy source for more powerful storms.
But our focus was on how warming oceans boost wave power. We looked at wave conditions over the past 35 years, and found global wave power has increased since at least the 1980s, mostly concentrated in the Southern Hemisphere, as more energy is being pumped into the oceans in the form of heat.
And a more energetic ocean means larger wave heights and more erosive energy potential for coastlines in some parts of the world than before.
Read more: Ocean warming threatens coral reefs and soon could make it harder to restore them
Ocean waves have shaped Earth’s coastlines for millions of years. So any small, sustained changes in waves can have long-term consequences for coastal ecosystems and the people who rely on them.
Mangroves and salt marshes, for example, are particularly vulnerable to increases in wave energy when combined with sea level rise.
To escape, mangroves and marshes naturally migrate to higher ground. But when these ecosystems back onto urban areas, they have nowhere to go and die out. This process is known as “coastal squeeze”.
These ecosystems often provide a natural buffer to wave attack for low-lying coastal areas. So without these fringing ecosystems, the coastal communities behind them will be exposed to more wave energy and, potentially, higher erosion.
So why is this happening?
Ocean waves are generated by winds blowing along the ocean surface. And when the ocean absorbs heat, the sea surface warms, encouraging the warm air over the top of it to rise (this is called convection). This helps spin up atmospheric circulation and winds.
In other words, we come to a cascade of impacts: warmer sea surface temperatures bring about stronger winds, which alter global ocean wave conditions.
Read more: Curious Kids: why are there waves?
Our research shows, in some parts of the world’s oceans, wave power is increasing because of stronger wind energy and the shift of westerly winds towards the poles. This is most noticeable in the tropical regions of the Atlantic and Pacific Oceans, and the subtropical regions of the Indian Ocean.
But not all changes in wave conditions are driven by ocean warming from human-caused climate change. Some areas of the world’s oceans are still more influenced by natural climate variability — such as El Niño and La Niña — than long-term ocean warming.
In general, it appears changes to wave conditions towards the equator are more driven by ocean warming from human-caused climate change, whereas changes to waves towards the poles remain more impacted by natural climate variability.
How this could erode the coasts
While the response of coastlines to climate change is a complex interplay of many processes, waves remain the principal driver of change along many of the world’s open, sandy coastlines.
So how might coastlines respond to getting hit by more powerful waves? It generally depends on how much sand there is, and how, exactly, wave power increases.
For example, if there’s an increase in wave height, this may cause increased erosion. But if the waves become longer (a lengthening of the wave period), then this may have the opposite effect, by transporting sand from deeper water to help the coast keep pace with sea level rise.
For low-lying nations in areas of warming sea surface temperatures around the equator, higher waves – combined with sea level rise – poses an existential problem.
People in these nations may experience both sea level rise and increasing wave power on their coastlines, eroding land further up the beach and damaging property. These areas should be regarded as coastal climate hotspots, where continued adaption or mitigation funding is needed.
It’s not too late
It’s not surprising for us to find the fingerprints of greenhouse warming in ocean waves and, consequentially, along our coastlines. Our study looked only at historical wave conditions and how these are already being impacted by climate change.
But if warming continues in line with current trends over the coming century, we can expect to see more significant changes in wave conditions along the world’s coasts than uncovered in our backward-looking research.
However, if we can mitigate greenhouse warming in line with the 2℃ Paris agreement, studies indicate we could still keep changes in wave patterns within the bounds of natural climate variability.
Read more: Seabirds are today’s canaries in the coal mine – and they’re sending us an urgent message
Still, one thing is abundantly clear: the impacts of climate change on waves is not a thing of the future, and is already occurring in large parts of the world’s oceans.
The extent to which these changes continue and the risk this poses to global coastlines will be closely linked to decarbonisation efforts over the coming decades.
This story is part of Oceans 21
Our series on the global ocean opened with five in depth profiles. Look out for new articles on the state of our oceans in the lead up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.
Thomas Mortlock, Senior Risk Scientist, Risk Frontiers, Adjunct Fellow, Macquarie University; Itxaso Odériz, Research assistant, Universidad Nacional Autónoma de México (UNAM); Nobuhito Mori, Professor, Kyoto University, and Rodolfo Silva, Professor, Universidad Nacional Autónoma de México (UNAM)
This article is republished from The Conversation under a Creative Commons license. Read the original article.
I thought the models couldnt handle wind. If they can – why would wind induced effect like coastal erosion be modelable – but not the wind induced effects on sea ice?
The real question is will the waves still be tasty?
So, they told these exact lies 30 years ago, repeated then 25, 20, 15, 10, 5 and now yet again. All they have is the same set of lies, just reworded and reprinted every few years. Yawn.
Then the stock photo selected is of a tranquil lagoon with near mirror surface.
I distinctly remember reading the alarmists whining about the loss of the Gulf Stream and other major currents due to “climate change”. Does their “novel” (read: unorthodox speculative ruse to drum up more speaking engagements and funding) “dynamic clustering” consider the hysterics of other grifters and their novel modeling gimmicks? If not, why not?
I want to see a cage-fight with these hacks all throwing their speculative mechanics into one large super-model, let a monkey twist the variability dials and see if they predict detonating Mars within twenty years.
(Oh.. just noticed that this is from the propaganda outlet ironically named “The Conversation”)
I’ll believe tripe like this when the elites stop buying waterfront properties and when waterfront properties or private islands loose their values.
Alternatively, why doesn’t this author recommend harnessing increased wave activity to produce energy – hydroelectric power at the shore?
Routine output from the Climate Liars…..
I blame it on daylight savings time.
The Conversation is just that, a conversation; and not a serious one but more like gossip around the water cooler.
It must definitely is not a conversation, it’s a monologue. Just try asking for evidence, proof, or offering a counter point of view. You’ll be cancelled before you can think.
They conveniently left out the fact that the same process promotes evaporation, which reinforces convection but also cools the surface of the water. This might be called lying by omission. However, it might also demonstrate the poor understanding the authors have of the big picture. However, one has to keep in mind that this is The Conversation!
Is our flush in danger because of CC ??
I like the way most articles end with “but it’s not too late”
I recall a few years ago the mantra was “we only have 10 years to save the planet” (or similar…..
At some point we should expect to see an alarmist article ending with either
“It’s too late – we are stuffed”
Or
“Meh – we got it wrong”
Just like fusion is always 20 years away, thermageddon is always 10 years away.
Salute!
Actchally, the salt water intrusion helps the mangroves and those suckers help with erosion by trapping silt and such.
Moved back here to the Gulf Coast over 40 years ago and can provide “boots on the ground’ verification of the massive increase in wave energy. When I was 45 years old I could easily stand in the surf trying to catch a pompano or sea trout or red fish. Now, I have to scurry back up on the sand like my grandchildren did before they learned about the waves and rip tides.
The wave energy has also been a major factor during the hurricanes we have had here since 1985. Lots more damage to the lots more condos and beach houses built on low shores. Imagine that? I just wonder how they measured that energy back in 1969 when Camille wiped Gulfport and Biloxi off the map! Those waves were significantly less powerful than the ones we have today.
My next peer reviewed paper for publication is going to correlate the 2 mm of sea level rise observed since 2010 with the number of small satellites put into orbit to have better cellphone coverage. I have to change my normal BS study, as some folks with the grant $$$ are catching on.
Gums sends…
If we reverse their model, do waves cease to exist before 1970s?
Coastlines are changing. Coastlines have always changed. Coastlines will always change. At one time Africa and South America are thought to have been connected. That is one heck of a coastline change!
Now adding this to my list of, what, over 200 different “bad things” that have been claimed as due to “climate change”, which itself stubbornly remains undefined.
Methods section suggests their “observations” were entirely limited to the output of a computer model they created and adjusted to their desired outcomes. Wake me up when someone does some actual science.
So they mention the (largely absent) sea level rise, then offer up a much less measurable new thing to worry about.
Not sure I’m understanding the snarkiness about the moon. As I understand it, the moon is key to understanding tidal movements, while waves are primarily governed by wind. Am I missing something?
“Our research shows, in some parts of the world’s oceans, wave power is increasing because of stronger wind energy and the shift of westerly winds towards the poles. “
This simplistic ‘analysis’ misses a couple of key points. Actual temperature is far less important than the change in temperature from one place to the next. Since the poles are warming faster than the equator, the delta T may actually be getting LESS. The other point is that the equator is spinning at over 1000 MPH, and carrying most of the atmosphere along with it. Otherwise, there would be 1000 MPH winds there. The surface is essentially motionless over the poles. This air speed difference can be a major factor in winds along the way, as the warm air at the equator rises and the cold air over the poles falls. 1.5 warmer degrees in the air circulating through this mess is hardly noticeable.
They say:
Their reference for this says:
They are claiming a higher heat gain over a shorter period.
Can we believe anything else they say?
Disclaimer: I am not a ‘climate scientist’.
“…encouraging the warm air over the top of it to rise (this is called convection).“
And that’s where I stopped reading. The author apparently considers he is addressing primary school children. I have to assume that the balance of the article is at the same level.
It’s more model nonsense.
From the “research“:
No matter where waves occur, they’ caused by ENSO.
As modeled theories go, this series of assumptions and complex calculations this series uses enough parameters for the elephant to not only wiggle it’s trunk, but to easily scratch beneath it’s tail.
So scare stories about sea level rises and oceans boiling aren’t working so they’ve got to try a different tactic.
“Since the 1970s, the ocean has absorbed more than 90% of the heat gained by the planet”
That heat came from IR, IR cant penetrate water, cant get past the cool layer, and cant warm it. The ocean can not absorb IR. It is a simple fact of physics.
What happens to it? Does it just wander off to the pub for a pint?
My pool gets warmer when the sun shines. I wonder how?
You would have thought that if waves were getting higher then ships would have to be designed to survive this new phenomenon. I see no comments in the nautical engineering press calling for a review of ship design because of this.