You live in one of the sunniest countries in the world. You might want to use that solar advantage and harvest all this free energy. Knowing that solar panels are rapidly becoming cheaper and have become feasible even in less sunny places like the UK, this should be a no-brainer.
Despite this, the Australian government has taken a step backwards at a time when we should be thinking 30 years ahead.
Further reading: Will the national energy guarantee hit pause on renewables?
Can we do it differently? Yes, we can! My ongoing research on sustainable urbanism makes it clear that if we use the available renewable resources in the Sydney region we do not need any fossil resource any more. We can become zero-carbon. (With Louisa King and Andy Van den Dobbelsteen, I have prepared a forthcoming paper, Towards Zero-Carbon Metropolitan Regions: The Example of
Sydney, in the journal SASBE.)
Enough solar power for every household
Abundant solar energy is available in the Sydney metropolitan area. If 25% of the houses each installed 35 square metres of solar panels, this could deliver all the energy for the city’s households.
We conservatively estimate a total yield of 195kWh/m2 of PV panel placed on roofs or other horizontal surfaces. The potential area of all Sydney council precincts suited for PV is estimated at around 385km2 – a quarter of the entire roof surface.
We calculate the potential total solar yield at 75.1TWh, which is more than current domestic household energy use (65.3TWh, according to the Jemena energy company).
Wind turbines to drive a whole city
If we install small wind turbines on land and larger turbines offshore we can harvest enough energy to fuel our electric vehicle fleet. Onshore wind turbines of 1-5MW generating capacity can be positioned to capture the prevailing southwest and northeast winds.
The turbines are placed on top of ridges, making use of the funnel effect to increase their output. We estimate around 840km of ridge lines in the Sydney metropolitan area can be used for wind turbines, enabling a total of 1,400 turbines. The total potential generation from onshore wind turbines is 6.13TWh.
Offshore turbines could in principle be placed everywhere, as the wind strength is enough to create an efficient yield. The turbines are larger than the ones on shore, capturing 5-7.5MW each, and can be placed up to 30km offshore. With these boundary conditions, an offshore wind park 45km long and 6km wide is possible. The total offshore potential then is 5.18TWh.
Altogether, then, we estimate the Sydney wind energy potential at 11.3TWh.
Turning waste into biofuels
We can turn our household waste and green waste from forests, parks and public green spaces into biogas. We can then use the existing gas network to provide heating and cooling for the majority of offices.
Biomass from domestic and green waste will be processed through anaerobic fermentation in old power plants to generate biogas. Gas reserves are created, stored and delivered through the existing power plants and gas grid.
Further reading: Biogas: smells like a solution to our energy and waste problems
Algae has enormous potential for generating bio-energy. Algae can purify wastewater and at the same be harvested and processed to generate biofuels (biodiesel and biokerosene).
Specific locations to grow algae are Botany Bay and Badgerys Creek. It’s noteworthy that both are close to airports, as algae could be important in providing a sustainable fuel resource for planes.
Using algae arrays to treat the waste water of new precincts, roughly a million new households as currently planned in Western Sydney, enables the production of great quantities of biofuel. Experimental test fields show yields can be high. A minimum of 20,000 litres of biodiesel per hectare of algae ponds is possible if organic wastewater is added. This quantity is realisable in Botany Bay and in western Sydney.
Further reading: Biofuel breakthroughs bring ‘negative emissions’ a step closer
Extracting heat from beneath the city
Shallow geothermal heat can be tapped through heat pumps and establishing closed loops in the soil. This can occur in large expanses of urban developments within the metropolitan area, which rests predominantly on deposits of Wianamatta shale in the west underlying Parramatta, Liverpool and Penrith.
Where large water surfaces are available, such as in Botany Bay or the Prospect Reservoir, heat can also be harvested from the water body.
The layers of the underlying Hawkesbury sandstone, the bedrock for much of the region, can yield deep geothermal heat. This is done by pumping water into these layers and harvesting the steam as heat, hot water or converted electricity.
Further reading: Explainer: what is geothermal energy?
Hydropower from multiple sources
The potential sources of energy from hydro generation are diverse. Tidal energy can be harvested at the entrances of Sydney Harbour Bay and Botany Bay, where tidal differences are expected to be highest.
Port Jackson, the Sydney Harbour bay and all of its estuaries have a total area of 55km2. With a tidal difference of two metres, the total maximum energy potential of a tidal plant would be 446TWh. If Sydney could harvest 20% of this, that would be more than twice the yield of solar panels on residential roofs.
If we use the tide to generate electricity, we can also create a surge barrier connecting Middle and South Head. Given the climatic changes occurring and still ahead of us, we need to plan how to protect the city from the threats of future cyclones, storm surges and flooding.
I have written here about the potential benefits of artificially creating a Sydney Barrier Reef. The reef, 30km at most out at sea, would provide Sydney with protection from storms.
At openings along the reef, wave power generators can be placed. Like tidal power, wave power can be calculated: mass displacement times gravity. If around 10km of the Sydney shoreline had wave power vessels, the maximum energy potential would be 3.2TWh.
In the mouths of the estuaries of Sydney Harbour and Botany Bay, freshwater meets saltwater. These places have a large potential to generate “blue energy” through reverse osmosis membrane technology.
To combine protective structures with tidal generating power, an open closure barrier is proposed for the mouth of Sydney Harbour. The large central gates need to be able to accommodate the entrance of large cruise ships and to close in times of a storm surge. At the same time, a tidal plant system operates at the sides of the barrier.
Master plan for a zero-carbon city
All these potential energy sources are integrated into our Master Plan for a Zero-Carbon Sydney. Each has led to design propositions that together can create a zero-carbon city.
The research shows there is enough, more than enough, potential reliable renewable energy to supply every household and industry in the region. What is needed is an awareness that Australia could be a global frontrunner in innovative energy policy, instead of a laggard.
In recent years, scientists have successfully identified the human fingerprint on hot years, heatwaves, and a range of other temperature extremes around the world. But as everyone knows, climate change affects more than just temperature.
The “signal” of human-induced climate change is not always clear in other weather events, such as cold snaps or episodes of extreme rainfall.
Three new studies, released today as part of a special edition of the Bulletin of the American Meteorological Society, take a closer look at two such events, both of which happened in southern Australia in mid-2016: the frosts that hit Western Australia’s South West, and the extremely wet weather that hit much of southeastern Australia during that year’s winter and early spring.
Perhaps surprisingly, WA’s frosts showed a fingerprint of climate change, due to changes in weather patterns. Meanwhile, there was very little climate change signal in the extreme rainfall that hit the southeast.
While there is a clear human-driven upward trend in Australia’s average temperatures and the future of southern Australia is projected to be dry in the cool seasons, last year Australia experienced its wettest winter and September on record. Meanwhile, September in WA’s South West brought up to 18 frost nights across the region – the most on record in some locations.
An increasing temperature trend would limit the number of extreme cold events, and broadly speaking this is true for Australia. So what caused the record frost risk in South West WA in September 2016?
For the northern hemisphere, a “wobbly” jet stream has been proposed as the cause of periodic blasts of extreme cold weather. In this theory, human-driven changes to atmospheric circulation cause Arctic air to temporarily extend southwards over populated areas, bringing Arctic weather in spite of the background warming trend. But this kind of theory hasn’t been examined in depth for Australia.
During southwestern WA’s bout of September frosts, the atmospheric pressure was generally very high, and the skies were clear. What’s more, that month featured a particularly persistent weather pattern of slow-moving high pressure west of Australia, which brought in cold air from the south.
The question is whether human-induced climate change is altering the circulation to make these conditions more likely. Research led by Michael Grose addressed this question by comparing climate models that describe the current, human-altered climate, and ones that leave out the influence of human-produced greenhouse gases.
Their results suggest that human-induced climate change is indeed changing the circulation patterns in our region, making this particular pattern more likely. They also suggest that it’s a fine balance between increasing average temperatures and these altered circulation patterns in this part of Australia.
In the models, daily minimum temperatures were not colder in the current climate than in those models without a human influence. This suggests that the two effects may cancel out (as far as extreme frost is concerned), although more work is needed to understand this intriguing possibility.
Record wet winter
Raising the global temperature can also make air more humid and therefore can result in more extreme rainfall events. The wettest day of the year is projected to become wetter by the end of the century. Are we already seeing an increase in extreme rain, and does it also hold true over the course of a month or a whole season?
September 2016 was by far the wettest September on record in Australia’s southeast, including the Murray Darling Basin, Australia’s food bowl. The amount of moisture in the air column during that month was extremely high. The question is whether this could have happened in a climate without global warming.
Researchers led by Pandora Hope analysed the local conditions for rainfall generation in forecasts of the event, under both the current climate and in a model that did not feature human greenhouse emissions. Air moisture levels were very high in both forecasts, but no higher in the current human-influenced climate than it might otherwise have been.
But there is more to rain generation than simply how much moisture there is in the air. Other factors are also important, such as weather patterns that cause moist air to accumulate in certain areas, and local atmospheric instability which is important for storms to form.
The results showed that under current climate conditions, those circulation factors were not as favourable to producing rainfall as they would be in a world without increased levels of carbon dioxide.
In other words, the local environment is generally becoming more stable, so it will be harder for these sorts of extreme rainfall events to develop.
During July to September 2016 the eastern tropical Indian Ocean was extremely warm, a result of the coincidence of the year-to-year variability of the tropical oceans and a strong ongoing upward warming trend. Rainfall in southeast Australia is often increased when ocean temperatures to the northwest of Australia are unusually high.
Research by Andrew King found that this association is indeed strong, and very important for the heavy rainfall through these months in 2016. But by analysing climate models both with and without the human influence on the climate, he found that human forcing had little influence on the intensity of this extreme rain event, consistent with the findings of the other study described above.
There is clearly still much left to learn about attributing the causes of extreme weather events. But these studies show that examining the effects of climate change on atmospheric circulation can help us better understand humans’ influence on Australian weather extremes.
Pandora Hope, Senior research scientist, Australian Bureau of Meteorology; Andrew King, Climate Extremes Research Fellow, University of Melbourne; Eun-Pa Lim, Senior research scientist, Australian Bureau of Meteorology, and Michael Grose, Climate Projections Scientist, CSIRO
The Emissions Reduction Fund (ERF), established in 2014 with funding of A$2.55 billion, is mostly spent. With just A$200 million left to be allocated, the Climate Change Authority this week released a report on the fund’s progress that can be best described as magnanimous.
The federal government claims that 189 million tonnes of emissions have been diverted or prevented from entering the atmosphere under the scheme. But research I have done with a co-author from Melbourne Law School has found serious issues, from giving unnecessary funds, to counting decade-old projects as new emissions “reductions”.
While the Authority made 26 recommendations for improvement, each is relatively low-impact. Most of the recommendations go towards increasing the fund’s transparency or removing barriers to participation. While these are laudable aims, there are deeper problems.
How should the fund work?
At its most basic, the ERF gives private companies and individuals a cash incentive to avoid or sequester greenhouse gas emissions. These businesses or people compete for funding by putting their projects forward at reverse auctions.
The fund is unique in Australia’s climate policy, in that the legislation that supports it has strong bipartisan support. Even if a change of federal government leads to a new policy for curbing emissions, it’s very likely that the basic ERF structure will be carried forward.
But despite the fund’s importance, there has been surprisingly little detailed academic analysis of it to date. In an effort to redress this, a colleague and I have a paper forthcoming that examines the underlying logic and effect of the fund. The paper focuses specifically on the path into the ERF for landfill operators, although the conclusions stretch further than just those projects.
Our conclusions are simple. With A$2.55 billion, the fund has considerable potential to crop the low-hanging fruit of Australia’s emissions profile. However, there are serious flaws in how some projects are assessed for funding.
Where support is granted to projects that would proceed without it, there is no benefit to the government’s intervention. Rather than lopping the low-hanging fruit, we are instead throwing money at the fruit that is already sitting in a bowl on the kitchen bench.
How to avoid redundancy
In the language of offsetting schemes, assessing a project to see if it needs extra funding to be commercially viable is known as an “additionality” test. The legislation that underpins the ERF contains three such tests, which are actually very strong:
Newness: is a project new? Has work on it already begun? If it has, the project is ineligible, because it is considered already commercially viable.
Existing regulations: is a particular project or emissions abatement already required by law? If so, the project is ineligible for ERF funding.
Other government funding: does a project have access to other sources of government funding? If it does, the proponent should use those funds instead.
If these three tests were mandated for all projects submitted to the ERF, it would be filled with projects that truly deliver new environmental benefit. But they’re not – and it isn’t.
There’s a simple reason why these tests aren’t used in all cases: there are 34 different ways of abating emissions recognised by the ERF (technically referred to as “methodologies”), from the destruction of methane from piggeries using engineered biodigesters, to avoiding deforestation.
Because these activities are so diverse, the legislation that underpins the ERF allows the Department of Environment and Energy to create methodology-specific tests instead, in consultation with industry stakeholders. They are then subject to ministerial approval.
In most cases, the replacements merely finesse the tests to make them more appropriate to the specific circumstances. For example, the existence of a conservation covenant (basically a promise to protect land) is not an obstacle to participation under the avoided deforestation methodology, despite these covenants being legally binding on present and future users of the land.
The case of landfill gas
Other instances are much less innocuous. One such area is landfill, where the gas created by decomposing rubbish can be captured and burned to create energy.
In the most egregious examples of “regulatory slippage” that either myself or my co-author have ever seen, the tests for whether landfill-related schemes should get ERF money have been completely neutered.
First, it predates the ERF by a full decade. Second, the capture and disposal of methane from landfill sites is required by Queensland’s air pollution laws. Finally, it receives renewable energy certificates under the Commonwealth Renewable Energy Target, as power is often created by methane burned to drive a steam turbine.
Nevertheless, this project is funded by the ERF. It should be noted clearly that there is no suggestion that the project is engaged in any deception. Its operators are absolutely complying with regulations. The issue is that the regulations themselves have been watered down to a ludicrous degree.
Two of the three tests (no funding from other government programs and not legally required) have been replaced by an unbelievably tautological requirement that landfill gas and combustion projects fulfil the legislative definition of a landfill gas and combustion project. That is, in order to pass the tests, a landfill gas capture and combustion project must merely be a landfill gas capture and combustion project.
The newness requirement permits projects that were previously registered under schemes that predate the ERF, which includes most of the larger sites for the capture and combustion of landfill methane in Australia.
Because this project already existed, its contributions are captured in measurements of Australia’s baseline emissions. While there’s a good argument for rewarding ecologically responsibly companies, that is not actually the point of the ERF. To state the obvious, we should not be paying to maintain the status quo, and then claim to be reducing emissions.
The Climate Change Authority has unfortunately not taken the opportunity to address these underlying problems, or the potential for similar issues in future legislation.
More immediately, we must take the government’s claim to have abated 189 million tonnes of emissions with a hefty grain of salt. The reality is that the scheme’s effect on Australia’s total emissions is considerably smaller.
In 2005, when I was chair of the National Committee on Soil and Terrain, I started a debate: where is Australia’s whitest beach? This was a diversion from the committee’s normal business of looking at the sustainable management of Australia’s soils, but it led down a path I hadn’t expected.
What began as a bit of after-hours banter became a serious look across Australia in search of our whitest beaches. New South Wales had already laid claim to the title, arguing that Hyams Beach at Jervis Bay has the whitest sand in the world, purportedly backed up by Guinness World Records.
As it turned out, both claims were false. Guinness World Records has no such category, and the whitest beach (as we found) is actually elsewhere.
So we drafted terms of reference, and the search for Australia’s Whitest Beach began. Over the next year samples were collected across the nation. The criteria were simple: samples had to be taken from the swash zone (the gently sloping area between the water and the dunes) and the samples could not be treated in any way apart from air-drying. No bleaching. No sieving out of impurities. Marine environment only.
The results of the first judging in 2006 were startling. Of all the states and territories, the much promoted Hyams Beach in New South Wales came in fourth. Third was Victoria, second Queensland, and first Western Australia.
The other states and territories came in at Tasmania fifth, Northern Territory sixth, and South Australia seventh. The ACT didn’t have a beach to sample, although technically some of the Commonwealth lands around our coasts could possibly come in under their banner (but that’s another debate altogether).
The winning beach was Lucky Bay in Cape Le Grand National Park on WA’s south coast, but in reality any of the beaches in this area could have been winners – Hellfire Bay, Thistle Cove and Wharton’s beach (just to name a few) are all magnificently white.
A quick qualification here: the southwestern end of Lucky Bay, where many people enter the beach, is covered with seaweed – not the whitest bit! I should also note that all of the finalists in the whitest beach challenge were in their own right fabulously white. But when compared side-by-side, some beaches are clearly whiter than others.
The Queensland team felt aggrieved, so in 2007 I carried out a repechage with new samples from Queensland at Whitehaven Beach in the Whitsundays, and Lake McKenzie on Fraser Island. Lake McKenzie was ultimately disallowed as it is a freshwater lake and the rules stipulated a marine environment. Meanwhile, Whitehaven didn’t quite cut the mustard in the judging and Lucky Bay in WA was again the winner.
So what makes a beach white, and is it important anyway?
The assessments were based on a visual comparison, so to remove any possible visual bias after the 2007 challenge all the samples were scanned for their reflectance – how much light bounced off the sand, essentially – in the visible and infrared wavelengths. Our assumption was that higher reflectance throughout the visual spectrum correlates with greater whiteness.
As it turned out, the results from the scanning exactly correlated with the visual assessments. The eye is quite good at discerning small differences in colour and reflectance. (More background and the results from the competition are available here.)
So what makes a beach white? Obviously, a pristine environment helps. Another factor is the distance from rivers, which deliver coloured organic and clay contaminants to the coast.
The geology of the area and the source of the sand are also critical, with quartz seemingly a major requirement for fine sands. Most white sandy beaches are derived from granitic, or less commonly sandstone, geologies that weather to produce fine, frosted quartz sand grains. Interestingly, sands made from shell or coral fragments just aren’t as white.
Is it important?
While this competition began in fun, I do believe it’s important. Beaches are places of refuge in this crazy world, and a pristine white beach indicates a cleanliness that is worth striving for. The reflectance of light off these sands through shallow waters near the beach creates a surreal, magical turquoise colour. White beaches are like the canary in the coalmine – once they’re spoiled, we know we’re in trouble.
Even though this study was a first look at some of Australia’s whitest beaches, and sampling was limited, it did highlight the sheer number of wonderful sandy beaches that Australia has.
The story’s not finished though. There are many white beaches out there yet to be sampled, and if you’d like to alert me to your potentially award-winning beach please email me or leave a comment on the whitest beach website.
It’s our responsibility, and I believe honour, to protect these amazing places. I’m sure there are more wonderful beaches out there that we haven’t sampled which may defeat Lucky Bay.
Shelburne Bay in northern Queensland, for example, is a contender yet to be sampled, and there are some magnificent beaches on the east coast of Tasmania. Whatever the outcome, let’s celebrate the natural wonders that surround our country.
There’s no doubt that humans killed off the Tasmanian tiger. But a new genetic analysis suggests this species had been on the decline for millennia before humans arrived to drive them to extinction.
The Tasmanian tiger, also known as the thylacine, was unique. It was the largest marsupial predator that survived into recent times. Sadly it was hunted to extinction in the wild, and the last known Tasmanian tiger died in captivity in 1936.
In a paper published in Nature Ecology and Evolution today, my colleagues and I piece together its entire genetic sequence for the first time. It tells us that thylacines’ genetic health had been declining for many millennia before they first encountered human hunters.
Our research also offered the chance to study the origins of the similarity in body shape between the thylacine and dogs. The two are almost identical, despite having last shared a common ancestor more than 160 million years ago – a remarkable example of so-called “convergent evolution”.
Decoding the thylacine genome allowed us to ask the question: if two animals develop an identical body shape, do they also show identical changes in their DNA?
These questions were previously difficult to answer. The age and storage conditions of existing specimens meant that most thylacine specimens have DNA that is highly fragmented into very short segments, which are not suitable for piecing together the entire genome.
We identified a 109-year-old specimen of a young pouch thylacine in the Museums Victoria collection, which had much more intact DNA than other specimens. This gave us enough pieces to put together the entire jigsaw of its genetic makeup.
Next, we made a detailed comparison of thylacines and dogs to see just how similar they really are. We used digital imaging to compare the thylacine’s skull shape to many other mammals, and found that the thylacine was indeed very similar to various types of dog (especially the wolf and red fox), and quite different from its closest living marsupial relatives such as the numbat, Tasmanian devil, and kangaroos.
Our results confirmed that thylacines and dogs really are the best example of convergent evolution between two distantly related mammal species ever described.
We next asked whether this similarity in body form is reflected by similarity in the genes. To do this, we compared the DNA sequences of thylacine genes with those of dogs and other animals too.
While we found many similarities between thylacines’ and dogs’ genes, they were not significantly more similar than the same genes from other animals with different body shapes, such as Tasmanian devils and cows.
We therefore concluded that whatever the reason why thylacines and dogs’ skulls are so similarly shaped, it is not because evolution is driving their gene sequences to be the same.
The thylacine genome also allowed us to deduce its precise position in the marsupial family tree, which has been a controversial topic.
By examining the amount of diversity present in the single thylacine genome, we were able to estimate its effective population size during past millennia. This demographic analysis revealed extremely low genetic diversity, suggesting that if we hadn’t hunted them into extinction the population would be in very poor genetic health, just like today’s Tasmanian devils.
The less diversity you have in your genome, the more susceptible you are to disease, which might be why devils have contracted the facial tumour virus, and certainly why it has been so easily spread. The thylacine would have been at a similar risk of contracting devastating diseases.
This loss in population diversity was previously thought to have occurred as a population of thylacines (and devils) became isolated on Tasmania some 15,000 years ago, when the land bridge closed between it and the mainland.
But our analysis suggests that the process actually began much earlier – between 70,000 and 120,000 years ago. This suggests that both the devil and thylacine populations already had very poor genetic health long before the land bridge closed.
Now that we know the whole genome of the Tasmanian tiger, we know much more about this extinct animal and the unique place it held in Australia’s marsupial family tree. We are expanding our analyses of the genome to determine how it came to look so similar to the dog, and to continue to learn more about the genetics of this unique marsupial apex predator.
It is often said that we know more about the surface of other planets than we do about our own deep ocean. To overcome this problem, we embarked on a voyage on CSIRO’s research vessel, the Southern Surveyor, to help map Australia’s continental slope – the region of seafloor connecting the shallow continental shelf to the deep oceanic abyssal plain.
The majority of our seafloor maps depict most of the ocean as blank and featureless (and the majority still do!). These maps are derived from wide-scale satellite data, which produce images showing only very large features such as sub-oceanic mountain ranges (like those seen on Google Earth). Compare that with the resolution of land-based imagery, which allows you to zoom in on individual trees in your own neighbourhood if you want to.
But using a state-of-the art sonar system attached to the Southern Surveyor, we have now studied sections of the seafloor in more detail. In the process, we found evidence of huge underwater landslides close to shore over the past 25,000 years.
Generally triggered by earthquakes, landslides like these can cause tsumanis.
Into the void
For 90% of the ocean, we still struggle to identify any feature the size of, say, Canberra. For this reason, we know more about the surface of Venus than we do about our own ocean’s depths.
As we sailed the Southern Surveyor in 2013, a multibeam sonar system attached to the vessel revealed images of the ocean floor in unprecedented detail. Only 40-60km offshore from major cities including Sydney, Wollongong, Byron Bay and Brisbane, we found huge scars where sediment had collapsed, forming submarine landslides up to several tens of kilometres across.
What are submarine landslides?
Submarine landslides, as the name suggests, are underwater landslides where seafloor sediments or rocks move down a slope towards the deep seafloor. They are caused by a variety of different triggers, including earthquakes and volcanic activity.
As we processed the incoming data to our vessel, images of the seafloor started to become clear. What we discovered was that an extensive region of the seafloor offshore New South Wales and Southern Queensland had experienced intense submarine landsliding over the past 15 million years.
From these new, high-resolution images, we were able to identify over 250 individual historic submarine landslide scars, a number of which had the potential to generate a tsunami. The Byron Slide in the image below is a good example of one of the “smaller” submarine landslides we found – at 5.6km long, 3.5km wide, 220m thick and 1.5 cubic km in volume. This is equivalent to almost 1,000 Melbourne Cricket Grounds.
The historic slides we found range in size from less than 0.5 cubic km to more than 20 cubic km – the same as roughly 300 to 12,000 Melbourne Cricket Grounds. The slides travelled down slopes that were less than 6° on average (a 10% gradient), which is low in comparison to slides on land, which usually fail on slopes steeper than 11°.
We found several sites with cracks in the seafloor slope, suggesting that these regions may be unstable and ready to slide in the future. However, it is likely that these submarine landslides occur sporadically over geological timescales, which are much longer than a human lifetime. At a given site, landslides might happen once every 10,000 years, or even less frequently than this.
Since returning home, our investigations have focused on how, when, and why these submarine landslides occur. We found that east Australia’s submarine landslides are unexpectedly recent, at less than 25,000 years old, and relatively frequent in geological terms.
We also found that for a submarine landslide to generate along east Australia today, it is highly likely that an external trigger is needed, such as an earthquake of magnitude 7 or greater. The generation of submarine landslides is associated with earthquakes from other places in the world.
Submarine landslides can lead to tsunamis ranging from small to catastrophic. For example, the 2011 Tohoku tsunami resulted in more than 16,000 individuals dead or missing, and is suggested to be caused by the combination of an earthquake and a submarine landslide that was triggered by an earthquake. Luckily, Australia experiences few large earthquakes, compared with places such as New Zealand and Peru.
Why should we care about submarine landslides?
We are concerned about the hazard we would face if a submarine landslide were to occur in the future, so we model what would happen in likely locations. Modelling is our best prediction method and requires combining seafloor maps and sediment data in computer models to work out how likely and dangerous a landslide threat is.
Our current models of tsunamis generated by submarine landslides suggest that some sites could represent a future tsunami risk for Australia’s east coast. We are currently investigating exactly what this threat might be, but we suspect that such tsunamis pose little to no immediate threat to the coastal communities of eastern Australia.
That said, submarine landslides are an ongoing, widespread process on the east Australian continental slope, so the risk cannot be ignored (by scientists, at least).
Of course it is hard to predict exactly when, where and how these submarine landslides will happen in future. Understanding past and potential slides, as well as improving the hazard and risk evaluation posed by any resulting tsunamis, is an important and ongoing task.
In Australia, more than 85% of us live within 50km of the coast. Knowing what is happening far beneath the waves is a logical next step in the journey of scientific discovery.
Samantha Clarke, Associate Lecturer in Education Innovation, University of Sydney; Hannah Power, Lecturer in Coastal Science, University of Newcastle; Kaya Wilson, , University of Newcastle, and Tom Hubble, Associate professor, University of Sydney