Firestorms and flaming tornadoes: how bushfires create their own ferocious weather systems



A firestorm on Mirror Plateaun Yellowstone Park, 1988.
Jim Peaco/US National Park Service

Rachel Badlan, UNSW

As the east coast bushfire crisis unfolds, New South Wales Premier Gladys Berejiklian and Rural Fire Service operational officer Brett Taylor have each warned residents bushfires can create their own weather systems.

This is not just a figure of speech or a general warning about the unpredictability of intense fires. Bushfires genuinely can create their own weather systems: a phenomenon known variously as firestorms, pyroclouds or, in meteorology-speak, pyrocumulonimbus.




Read more:
Firestorms: the bushfire/thunderstorm hybrids we urgently need to understand


The occurrence of firestorms is increasing in Australia; there have been more than 50 in the period 2001-18. During a six-week period earlier this year, 18 confirmed pyrocumulonimbus formed, mainly over the Victorian High Country.

A pyrocumulonimbus cloud generated by a bushfire in Licola,Victoria, on March 2, 2019.
Elliot Leventhal, Author provided

Its not clear whether the current bushfires will spawn any firestorms. But with the frequency of extreme fires set to increase due to hotter and drier conditions, it’s worth taking a closer look at how firestorms happen, and what effects they produce.

What is a firestorm?

The term “firestorm” is a contraction of “fire thunderstorm”. In simple terms, they are thunderstorms generated by the heat from a bushfire.

In stark contrast to typical bushfires, which are relatively easy to predict and are driven by the prevailing wind, firestorms tend to form above unusually large and intense fires.

If a fire encompasses a large enough area (called “deep flaming”), the upward movement of hot air can cause the fire to interact with the atmosphere above it, potentially forming a pyrocloud. This consists of smoke and ash in the smoke plume, and water vapour in the cloud above.

If the conditions are not too severe, the fire may produce a cloud called a pyrocumulus, which is simply a cloud that forms over the fire. These are typically benign and do not affect conditions on the ground.

But if the fire is particularly large or intense, or if the atmosphere above it is unstable, this process can give birth to a pyrocumulonimbus – and that is an entirely more malevolent beast.

What effects do firestorms produce?

A pyrocumulonibus cloud is much like a normal thunderstorm that forms on a hot summer’s day. The crucial difference here is that this upward movement is caused by the heat from the fire, rather than simply heat radiating from the ground.

Conventional thunderclouds and pyrocumulonimbus share similar characteristics. Both form an anvil-shaped cloud that extends high into the troposphere (the lower 10-15km of the atmosphere) and may even reach into the stratosphere beyond.

NASA image of pyrocumulonimbus formation in Argentina, January 2018.
NASA

The weather underneath these clouds can be fierce. As the cloud forms, the circulating air creates strong winds with dangerous, erratic “downbursts” – vertical blasts of air that hit the ground and scatter in all directions.

In the case of a pyrocumulonimbus, these downbursts have the added effect of bringing dry air down to the surface beneath the fire. The swirling winds can also carry embers over huge distances. Ember attack has been identified as the main cause of property loss in bushfires, and the unpredictable downbursts make it impossible to determine which direction the wind will blow across the ground. The wind direction may suddenly change, catching people off guard.

Firestorms also produce dry lightning, potentially sparking new fires, which may then merge or coalesce into a larger flaming zone.

In rare cases, a firestorm can even morph into a “fire tornado”. This is formed from the rotating winds in the convective column of a pyrocumulonimbus. They are attached to the firestorm and can therefore lift off the ground.




Read more:
Turn and burn: the strange world of fire tornadoes


This happened during the infamous January 2003 Canberra bushfires, when a pyrotornado tore a path near Mount Arawang in the suburb of Kambah.

A fire tornado in Kambah, Canberra, 2003 (contains strong language).

Understandably, firestorms are the most dangerous and unpredictable manifestations of a bushfire, and are impossible to suppress or control. As such, it is vital to evacuate these areas early, to avoid sending fire personnel into extremely dangerous areas.

The challenge is to identify the triggers that cause fires to develop into firestorms. Our research at UNSW, in collaboration with fire agencies, has made considerable progress in identifying these factors. They include “eruptive fire behaviour”, where instead of a steady rate of fire spread, once a fire interacts with a slope, the plume may attach to the ground and rapidly accelerate up the hill.

Another process, called “vorticity-driven lateral spread”, has also been recognised as a good indicator of potential fire blow-up. This occurs when a fire spreads laterally along a ridge line instead of following the direction of the wind.

Although further refinement is still needed, this kind of knowledge could greatly improve decision-making processes on when and where to deploy on-ground fire crews, and when to evacuate before the situation turns deadly.The Conversation

Rachel Badlan, Postdoctoral Researcher, Atmospheric Dynamics, UNSW

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

Australia could see fewer cyclones, but more heat and fire risk in coming months


Jonathan Pollock, Australian Bureau of Meteorology; Andrew B. Watkins, Australian Bureau of Meteorology; Catherine Ganter, Australian Bureau of Meteorology, and Paul Gregory, Australian Bureau of Meteorology

Northern Australia is likely to see fewer cyclones than usual this season, but hot, dry weather will increase the risk of fire and heatwaves across eastern and southern Australia.

The Bureau of Meteorology today released its forecast for the tropical cyclone season, which officially runs from November 1 to April 30.




Read more:
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Also published today is the October to April Severe Weather Outlook, which examines the risk of other weather extremes like flooding, heatwaves and bushfires.

Warmer oceans means more cyclones

On average, 11 tropical cyclones form each season in the Australian region. Around four of those cross the coast. The total number each season is roughly related to how much cooler or warmer than average the tropical oceans near Australia are during the cyclone season.

Map showing the average number of tropical cyclones through the Australian region and surrounding waters in ENSO-neutral years, using all years of data from the 1969-70 to 2017-18 tropical cyclone season.

One of the biggest drivers of change in ocean temperatures is the El Niño–Southern Oscillation, or ENSO. During La Niña phases of ENSO, the warmest waters in the equatorial Pacific build up in the western Pacific and to the north of Australia. That region then becomes the focus for more cloud, rainfall and tropical cyclones.

But during El Niño, the warmest water shifts towards the central Pacific and away from northern Australia. This decreases the likelihood of cyclones in our region.




Read more:
Explainer: El Niño and La Niña


And when ENSO is neutral, there is little push towards above or below average numbers of cyclones.

Temperatures in the tropical Pacific Ocean have been ENSO-neutral since April and are likely to stay neutral until at least February 2020. However, some tropical patterns are El Niño-like, including higher-than-average air pressure at Darwin. This may be related to the current record-strong positive Indian Ocean Dipole – another of Australia’s major climate drivers – and the cooler waters surrounding northern Australia.

The neutral ENSO phase alongside higher-than-average air pressure over northern Australia means we expect fewer-than-average tropical cyclones in the Australian region this season. The bureau’s Tropical Cyclone Season Outlook model predicts a 65% chance of fewer-than-average cyclones.

At least one tropical cyclone has crossed the Australian coast every season since reliable records began in the 1970s, so people across northern Australia need to be prepared every year. In ENSO-neutral cyclone seasons, this first cyclone crossing typically occurs in late December.




Read more:
El Niño has rapidly become stronger and stranger, according to coral records


Other severe weather

While cyclones are one of the key concerns during the coming months, the summer months also bring the threat of several other forms of severe weather, including bushfires, heatwaves and flooding rain.

With dry soils inland, and hence little moisture available to cool the air, and a forecast for clear skies and warmer days, there is an increased chance that heat will build up over central Australia during the spring and summer months. This increases the chance of heatwaves across eastern and southern Australia when that hot air is drawn towards the coast by passing weather systems.

Australian seasonal bushfire outlook, as of August 2019. Vast areas of Australia, particularly the east coast, have an above-normal fire potential this season.
Bushfire and Natural Hazards CRC/Australasian Fire and Emergency Service Authorities Council

Likewise, the dry landscape and the chance of extreme heat also raise the risk of more bushfires throughout similar parts of Australia, especially on windy days. And with fewer natural firebreaks such as full rivers and streams, even greater care is needed in some areas.

Widespread floods are less likely this season. This is because of forecast below-average rainfall and also because dry soils mean the first rains will soak into the ground rather than run across the landscape.

However, as we saw in northern Queensland in January and February this year, when up to 2 metres of rainfall fell in less than 10 days, localised flooding can occur in any wet season if a tropical low parks itself in one location for any length of time.




Read more:
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Most of all, it’s always important to follow advice from emergency services on what to do before, during and after severe weather. Know your weather, know your risk and be prepared. You can stay up to date with the latest forecast and warnings on the bureau’s website and subscribe to receive climate information emails.The Conversation

Jonathan Pollock, Climatologist, Australian Bureau of Meteorology; Andrew B. Watkins, Head of Long-range Forecasts, Australian Bureau of Meteorology; Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology, and Paul Gregory, BOM, Australian Bureau of Meteorology

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

Winter storms are speeding up the loss of Arctic sea ice



A scientist checks cracks in the Arctic sea ice after a storm (April 2015, N-ICE2015 expedition).
Amelie Meyer/NPI, Author provided

Amelie Meyer, University of Tasmania

Arctic sea ice is already disappearing rapidly but our research shows winter storms are now further accelerating sea ice loss.




Read more:
Arctic breakdown: what climate change in the far north means for the rest of us


The research is based on data we gathered during an expedition on a small Norwegian research vessel, the Lance, that was left to drift in the Arctic sea ice for five months in 2015.

Time series of air temperature anomalies in the Arctic for the period 1981-2010: Temperatures in the Arctic in May and June 2019 period were the warmest in the satellite records.
Zack Labe (@ZLabe)

The expedition was intense and felt more like going to the Moon than going on a typical research cruise. What took us by surprise were the many winter storms that battered the ice (and our ship and ice camp).

It has taken us years to collate these data but now we know the winter storms play a key role in the fate of Arctic sea ice, particularly in the Atlantic sector of the Arctic.

Norwegian research vessel ‘Lance’ frozen in the Arctic sea ice in February 2015 during the N-ICE2015 expedition.
Paul Dodd (NPI)

How winter storms amplify climate change

On average, about 10 extreme storms will reach all the way to the North Pole each winter. While these winter storms are short (they last on average 6-48 hours), they can be incredibly intense.

During a storm in winter 2015 we saw the air temperature rise from -40℃ (-40℉) to 0℃ (32℉) in just a day, and then fall back to -30℃ (-22℉) the next day, when cold Arctic air returned after the storm.

These storms bring heat, moisture and strong winds into the Arctic, and next we look at how they impact sea ice and its surroundings.

Warming and weakening the ice

The heat from the storms warms up the air, snow and ice, slowing down the growth of the ice. Moisture from the storms falls as snow on the ice. After the storm, the blanket of snow insulates the ice from the cold air, further slowing the growth of the ice for the remainder of winter.

The strong winds during the storms push the ice around and break it into pieces, making it more fragile and deforming it, more like a boulder field.

The strong winds also stir the ocean below the ice, mixing up warmer water from deeper waters to the surface where it melts the ice from below. This melting of the ice in the middle of winter can happen for several days after the storms when the air is already back to well below freezing.

Processes related to Arctic winter storms. In the first storm phase, strong southerly winds compress the ice cover and transport warm air, moisture, and bring strong winds. In the second phase, northerly winds transport ice southwards. After the storm has passed, cold and calm conditions return, allowing new ice to grow in leads. When the next winter storm arrives, it further drives the ice cover into a relatively thin-ice, snow-covered mosaic of strongly deformed ice floes. These new conditions impact surrounding ecosystems by shaping habitats and light conditions.
Graham et al., 2019 (Scientific Reports)

Thinner ice, shelter for life and accelerated melting

The breakup of the ice opens big passages of open water between ice floes, called leads. In winter these passages end up refreezing rapidly, generating new super-thin ice.

These thinner refrozen patches of ice let more light through in the following spring, allowing ocean plants (phytoplankton) to bloom earlier.

The rougher sea ice landscape becomes a shelter for many ice-associated Arctic organisms, including ice algae, becoming biological hot spots in the following spring.

The broken up and deformed ice drifts faster, reaching warmer waters where it melts sooner and faster.

So really, winter storms precondition the ice to a faster melt in the following spring with an impact that continues well into the following season.

Why is Arctic sea ice declining?

Winter sea ice cover in the Atlantic sector of the Arctic has been retreating at a record breaking pace, especially in the Barents Sea off Norway and Russia.

Average September Arctic sea ice extent from 1979 to 2018. Black line shows monthly average for each year; blue line shows the trend.
National Snow and Ice Data Center

The Arctic is particularly sensitive to human driven climate change. We know the decrease in sea ice is due to both the warming of the Arctic (air and ocean) and changing wind patterns that break up the ice cover.

But there are also amplifying mechanisms or “feedback” mechanisms, in which one natural process reinforces another. Their role in the decrease of sea ice is hard to predict. We now know winter storms in the Arctic contribute to these feedback mechanisms.

More storms ahead

Arctic winter storms are increasing in frequency and this is likely due to climate change.

With the thinner Arctic sea ice cover and shallower warmer water in the Arctic Ocean, the mechanisms we observed during the winter storms will likely strengthen and the overall impact of winter storms on Arctic ice is likely to increase in the future.

Two weeks ago, the Arctic sea ice reached its minimum extent for 2019, after another winter of intense winter storms. The minimum ice extent was effectively tied for second lowest since modern record-keeping began in the late 1970s, along with 2007 and 2016, reinforcing the long-term downward trend in Arctic ice extent. Arctic sea ice has been declining for at least 40 years, and amplifying mechanisms such as the winter storms are accelerating this retreat.

Arctic sea ice extent just reached its annual minimum extent for 2019 on September 18. This season was a tie for the 2nd lowest on record, along with 2007 and 2016 and behind 2012, which holds the overall record minimum.
Zack Labe (@ZLabe)

As highlighted in the recent IPCC Ocean and Cryopshere report, these changes in September sea ice are likely unprecedented for at least 1,000 years.

Remember also that changes in the Arctic don’t just affect the immediate region: Arctic warming has been linked to the polar vortex, and weather extremes across central Europe and north America.




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Microplastics may affect how Arctic sea ice forms and melts


As we start taking into account feedback mechanisms like the winter storms, our predictions for the first Arctic sea ice free summer are indicating it will likely happen before 2050.The Conversation

Amelie Meyer, Research fellow, University of Tasmania

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

The air above Antarctica is suddenly getting warmer – here’s what it means for Australia



Antarctic winds have a huge effect on weather in other places.
NASA Goddard Space Flight Center/Flickr, CC BY-SA

Harry Hendon, Australian Bureau of Meteorology; Andrew B. Watkins, Australian Bureau of Meteorology; Eun-Pa Lim, Australian Bureau of Meteorology, and Griffith Young, Australian Bureau of Meteorology

Record warm temperatures above Antarctica over the coming weeks are likely to bring above-average spring temperatures and below-average rainfall across large parts of New South Wales and southern Queensland.

The warming began in the last week of August, when temperatures in the stratosphere high above the South Pole began rapidly heating in a phenomenon called “sudden stratospheric warming”.




Read more:
The winter was dry, the spring will likely be dry – here’s why


In the coming weeks the warming is forecast to intensify, and its effects will extend downward to Earth’s surface, affecting much of eastern Australia over the coming months.

The Bureau of Meteorology is predicting the strongest Antarctic warming on record, likely to exceed the previous record of September 2002.

(Left) Observation of September 2002 stratospheric warming compared to (right) 2019 forecast for September.
The forecast for 2019 was provided by the Australian Bureau of Meteorology and was initialised on August 30, 2019.

What’s going on?

Every winter, westerly winds – often up to 200km per hour – develop in the stratosphere high above the South Pole and circle the polar region. The winds develop as a result of the difference in temperature over the pole (where there is no sunlight) and the Southern Ocean (where the sun still shines).

As the sun shifts southward during spring, the polar region starts to warm. This warming causes the stratospheric vortex and associated westerly winds to gradually weaken over the period of a few months.

However, in some years this breakdown can happen faster than usual. Waves of air from the lower atmosphere (from large weather systems or flow over mountains) warm the stratosphere above the South Pole, and weaken or “mix” the high-speed westerly winds.

Very rarely, if the waves are strong enough they can rapidly break down the polar vortex, actually reversing the direction of the winds so they become easterly. This is the technical definition of “sudden stratospheric warming.”

Although we have seen plenty of weak or moderate variations in the polar vortex over the past 60 years, the only other true sudden stratospheric warming event in the Southern Hemisphere was in September 2002.

In contrast, their northern counterpart occurs every other year or so during late winter of the Northern Hemisphere because of stronger and more variable tropospheric wave activity.

What can Australia expect?

Impacts from this stratospheric warming are likely to reach Earth’s surface in the next month and possibly extend through to January.

Apart from warming the Antarctic region, the most notable effect will be a shift of the Southern Ocean westerly winds towards the Equator.

For regions directly in the path of the strongest westerlies, which includes western Tasmania, New Zealand’s South Island, and Patagonia in South America, this generally results in more storminess and rainfall, and colder temperatures.

But for subtropical Australia, which largely sits north of the main belt of westerlies, the shift results in reduced rainfall, clearer skies, and warmer temperatures.

Past stratospheric warming events and associated wind changes have had their strongest effects in NSW and southern Queensland, where springtime temperatures increased, rainfall decreased and heatwaves and fire risk rose.

The influence of the stratospheric warming has been captured by the Bureau’s climate outlooks, along with the influence of other major climate drivers such as the current positive Indian Ocean Dipole, leading to a hot and dry outlook for spring.

Anomalous Australian climate conditions during the nine most significant polar vortex weakening years (1979, 1988, 2000, 2002, 2004, 2005, 2012, 2013, 2016) on both maximum and minimum temperatures, and rainfall for October-November, as compared to all other years between 1979-2016.
Bureau of Meteorology

Effects on the ozone hole and Antarctic sea ice

One positive note of sudden stratospheric warming is the reduction – or even absence altogether – of the spring Antarctic ozone hole. This is for two reasons.

First, the rapid rise of temperatures in the upper atmosphere means the super cold polar stratospheric ice clouds, which are vital for the chemical process that destroys ozone, may not even form.

Secondly, the disrupted winds carry more ozone-rich air from the tropics to the polar region, helping repair the ozone hole.

We also expect an enhanced decline in Antarctic sea ice between October and January, particularly in the eastern Ross Sea and western Amundsen Sea, as more warm water moves towards the poles due to the weaker westerly winds.




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Thanks to improvements in modelling and the Bureau’s new supercomputer, these types of events can be forecast better than ever before. Compared to 2002, when we didn’t know much about the event until after it had happened, this time we’ve had almost three weeks’ notice that a very strong warming event was coming. We also know much more about the process that has been set in train, that will affect our weather over the next one to four months.The Conversation

Harry Hendon, Senior Principal Research Scientist, Australian Bureau of Meteorology; Andrew B. Watkins, Manager of Long-range Forecast Services, Australian Bureau of Meteorology; Eun-Pa Lim, Senior research scientist, Australian Bureau of Meteorology, and Griffith Young, Senior IT Officer, Australian Bureau of Meteorology

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

The winter was dry, the spring will likely be dry – here’s why


Jonathan Pollock, Australian Bureau of Meteorology and Andrew B. Watkins, Australian Bureau of Meteorology

Winter still has a few days to run, but it’s highly likely to be one of Australia’s warmest and driest on record. While final numbers will be crunched once August ends, this winter will probably rank among the top ten warmest for daytime temperatures and the top ten driest for rainfall.

While it was drier than average across most of the country, it was especially dry across South Australia, New South Wales and southern Queensland. Small areas of South Australia and New South Wales are on track for their driest winter on record.




Read more:
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In contrast, parts of southern Victoria, western Tasmania and central Queensland were wetter than usual.

Preliminary winter 2019 rainfall deciles.
Bureau of Meteorology

Thirsty ground

Soil moisture normally increases during winter (except in the tropics, where it’s the dry season), and while we saw that in parts of Victoria, for most of Queensland and New South Wales the soil moisture actually decreased.

Dry soils leading into winter have soaked up the rain that has fallen, resulting in limited runoff and inflows into the major water storages across the country.

A glass half empty

Sydney’s water storages dropping below 50% received considerable public attention, and unfortunately a number of other regional storages in New South Wales and the Murray Darling Basin are much lower than that.

The winter ‘filling’ season in the southern Murray Darling Basin has been drier than usual for the third year in a row, and storages in the northern Murray Darling basin are extremely low or empty with no meaningful inflows.

Some rain in the west

Some regions did receive enough rainfall to grow crops this cool season. However, northern New South Wales and southern Queensland didn’t see an improvement in their severe year-to-date rainfall deficiencies over winter.

In fact, the area of the country that is experiencing year-to-date rainfall in the lowest 5% of historical records expanded.

In better news, the severe year-to-date deficiencies across southwest Western Australia shrank during winter.

Indian Ocean Dipole the culprit

Sustained differences between sea surface temperatures in the tropical western and eastern Indian Ocean are known as the Indian Ocean Dipole (IOD). The IOD impacts Australian seasonal rainfall and temperature patterns, much like the more well known El Niño–Southern Oscillation.

Warm sea surface temperatures in the tropical western Indian Ocean and cool sea surface temperatures in the eastern Indian Ocean, along with changes in both cloud and wind patterns, have been consistent with a positive Indian Ocean Dipole since late May.

International climate models, some of which forecast the positive IOD as early as February, agree that it is likely to continue through spring.

Typically, this means below average rainfall and above average temperatures for much of central and southern Australia, which is consistent with the current rainfall and temperature outlook from the Bureau’s dynamical computer model. The positive IOD is likely to be the dominant climate driver for Australia during the next three months.

Comparison of international climate model forecasts of the IOD index for November 2019.
Models from the Australian Bureau of Meteorology, Canadian Meteorological Centre, European Centre for Medium-Range Weather Forecasts, Meteo France, National Aeronautics and Space Administration (USA) and the Met Office (UK)

A dry end to 2019 likely

Chances are the remainder of 2019 will be drier than normal for most of Australia. The exceptions are western Tasmania, southern Victoria and western WA, where chances of a wetter or drier than average end to the year are roughly equal.

The spring 2019 outlook showing low chances of above average rainfall for most of the country.
Bureau of Meteorology

Warmer than average days are very likely (chances above 80%) for most of the country except the far south of the mainland, and Tasmania.

Nights too are likely to be warmer than average for most of the country. However, much of Victoria and Tasmania, and southern parts of South Australia and New South Wales have close to an even chance for warmer than average minimum temperatures.

Due to the warm and dry start to the year, the east coast of Queensland, New South Wales, Victoria and Tasmania, as well as parts of southern Western Australia, face above normal fire potential this coming bushfire season.

More outlooks more often

The term weather describes conditions over shorter periods, such as from minutes to days, while the term climate describes the more slowly varying aspects of the atmosphere.

From today, the Bureau of Meteorology is closing the forecast gap between weather and climate information with the release of weekly and fortnightly climate outlooks.

For the first time, rainfall and temperature outlooks for the weeks directly after the 7-day forecast are available. One- and two-week outlooks have been added to complement the existing 1-month and 3-month outlooks.




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The new outlook information for the weeks ahead also features how much above or below average temperatures are likely to be, and the likelihood of different rainfall totals.

The Bureau’s outlook videos explain the long-range forecast for the coming months.
Bureau of Meteorology


You can find climate outlooks and summaries on the Bureau of Meteorology website here.The Conversation

Jonathan Pollock, Climatologist, Australian Bureau of Meteorology and Andrew B. Watkins, Manager of Long-range Forecast Services, Australian Bureau of Meteorology

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

Extreme weather caused by climate change has damaged 45% of Australia’s coastal habitat



Bleached staghorn coral on the Great Barrier Reef. Many species are dependent on corals for food and shelter.
Damian Thomson, Author provided

Russ Babcock, CSIRO; Anthony Richardson, The University of Queensland; Beth Fulton, CSIRO; Eva Plaganyi, CSIRO, and Rodrigo Bustamante, CSIRO

If you think climate change is only gradually affecting our natural systems, think again.

Our research, published yesterday in Frontiers in Marine Science, looked at the large-scale impacts of a series of extreme climate events on coastal marine habitats around Australia.

We found more than 45% of the coastline was already affected by extreme weather events caused by climate change. What’s more, these ecosystems are struggling to recover as extreme events are expected to get worse.




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There is growing scientific evidence that heatwaves, floods, droughts and cyclones are increasing in frequency and intensity, and that this is caused by climate change.

Life on the coastline

Corals, seagrass, mangroves and kelp are some of the key habitat-forming species of our coastline, as they all support a host of marine invertebrates, fish, sea turtles and marine mammals.

Our team decided to look at the cumulative impacts of recently reported extreme climate events on marine habitats around Australia. We reviewed the period between 2011 and 2017 and found these events have had devastating impacts on key marine habitats.

Healthy kelp (left) in Western Australia is an important part of the food chain but it is vulnerable to even small changes in temperature and particularly slow to recover from disturbances such as the marine heatwave of 2011. Even small patches or gaps (right) where kelp has died can take many years to recover.
Russ Babcock, Author provided

These include kelp and mangrove forests, seagrass meadows, and coral reefs, some of which have not yet recovered, and may never do so. These findings paint a bleak picture, underscoring the need for urgent action.

During this period, which spanned both El Niño and La Niña conditions, scientists around Australia reported the following events:

2011: The most extreme marine heatwave ever occurred off the west coast of Australia. Temperatures were as much as 2-4℃ above average for extended periods and there was coral bleaching along more than 1,000km of coast and loss of kelp forest along hundreds of kilometres.

Seagrasses in Shark Bay and along the entire east coast of Queensland were also severely affected by extreme flooding and cyclones. The loss of seagrasses in Queensland may have led to a spike in deaths of turtles and dugongs.

2013: Extensive coral bleaching took place along more than 300km of the Pilbara coast of northwestern Australia.

2016: The most extreme coral bleaching ever recorded on the Great Barrier Reef affected more than 1,000km of the northern Great Barrier Reef. Mangrove forests across northern Australia were killed by a combination of drought, heat and abnormally low sea levels along the coast of the Gulf of Carpentaria across the Northern Territory and into Western Australia.

2017: An unprecedented second consecutive summer of coral bleaching on the Great Barrier Reef affects northern Great Barrier Reef again, as well as parts of the reef further to the south.

Heritage areas affected

Many of the impacted areas are globally significant for their size and biodiversity, and because until now they have been relatively undisturbed by climate change. Some of the areas affected are also World Heritage Areas (Great Barrier Reef, Shark Bay, Ningaloo Coast).

Seagrass meadows in Shark Bay are among the world’s most lush and extensive and help lock large amounts of carbon into sediments. The left image shows healthy seagrass but the right image shows damage from extreme climate events in 2011.
Mat Vanderklift, Author provided

The habitats affected are “foundational”: they provide food and shelter to a huge range of species. Many of the animals affected – such as large fish and turtles – support commercial industries such as tourism and fishing, as well as being culturally important to Australians.

Recovery across these impacted habitats has begun, but it’s likely some areas will never return to their previous condition.

We have used ecosystem models to evaluate the likely long-term outcomes from extreme climate events predicted to become more frequent and more intense.

This work suggests that even in places where recovery starts, the average time for full recovery may be around 15 years. Large slow-growing species such as sharks and dugongs could take even longer, up to 60 years.

But extreme climate events are predicted to occur less than 15 years apart. This will result in a step-by-step decline in the condition of these ecosystems, as it leaves too little time between events for full recovery.

This already appears to be happening with the corals of the Great Barrier Reef.

Gradual decline as things get warmer

Damage from extreme climate events occurs on top of more gradual changes driven by increases in average temperature, such as loss of kelp forests on the southeast coasts of Australia due to the spread of sea urchins and tropical grazing fish species.

Ultimately, we need to slow down and stop the heating of our planet due to the release of greenhouse gases. But even with immediate and effective emissions reduction, the planet will remain warmer, and extreme climatic events more prevalent, for decades to come.

Recovery might still be possible, but we need to know more about recovery rates and what factors promote recovery. This information will allow us to give the ecosystems a helping hand through active restoration and rehabilitation efforts.




Read more:
More than 28,000 species are officially threatened, with more likely to come


We will need new ways to help ecosystems function and to deliver the services that we all depend on. This will likely include decreasing (or ideally, stopping) direct human impacts, and actively assisting recovery and restoring damaged ecosystems.

Several such programs are active around Australia and internationally, attempting to boost the ability of corals, seagrass, mangroves and kelp to recover.

But they will need to be massively scaled up to be effective in the context of the large scale disturbances seen in this decade.The Conversation

Mangroves at the Flinders River near Karumba in the Gulf of Carpentaria. The healthy mangrove forest (left) is near the river while the dead mangroves (right) are at higher levels where they were much more stressed by conditions in 2016. Some small surviving mangroves are seen beginning to recover by 2017.
Robert Kenyon, Author provided

Russ Babcock, Senior Principal Research Scientist, CSIRO; Anthony Richardson, Professor, The University of Queensland; Beth Fulton, CSIRO Research Group Leader Ecosystem Modelling and Risk Assessment, CSIRO; Eva Plaganyi, Senior Principal Research Scientist, CSIRO, and Rodrigo Bustamante, Research Group Leader , CSIRO

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