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A new study has found that marine heatwaves have become more than 20 times more frequent over the past four decades due to the burning of greenhouse gases. 

A marine heatwave is an extended period of time in which the water temperature in a particular ocean region is abnormally high. The study, published in the journal Science, is the first to look at the anthropogenic impacts on marine heatwaves and was conducted by a team of marine scientists at the University of Bern in Switzerland. By examining satellite measurements of sea surface temperatures from 1981 to 2017, the team found that these heatwaves have become longer, hotter and more frequent. 

In the 1980s, satellites recorded 27 major marine heatwaves, which each lasted about a month with water temperatures reaching a maximum of 4.8 degrees Celsius above average. In the last 10 years, there were 172 major heatwaves across the globe, lasting 48 days on average with temperatures reaching a maximum of 5.5 degrees above average.

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Heatwaves can have lasting, detrimental effects on marine ecosystems. Warmer temperatures can trigger algal blooms, impact on nutrient availability, cause coral bleaching and change fish migration patterns. 

In pre-industrial times, extreme marine heatwaves similar to those seen in the past decade would have occurred once every few hundred to thousands of years. However, the team found that if global temperatures rise 1.5 degrees Celsius- the goal of the Paris Agreement- these heatwaves could happen once a decade or century. If temperatures increase by 3 degrees Celsius, these heatwaves could become as frequent as once a year of decade. 

Charlotte Laufkӧtter, one of the authors of the study, says, “Ambitious climate goals are an absolute necessity for reducing the risk of unprecedented marine heatwaves. They are the only way to prevent the irreversible loss of some of the most valuable marine ecosystems.”

A prolonged heatwave in the Arctic that caused temperatures to soar to 38℃ in parts of Siberia, is causing wildfires to rage through parts of Siberia, Alaska, Greenland and Canada. In June, fires in the region emitted 16.3 million tons of carbon- or about 60 million tons of carbon dioxide, the highest levels since 2003 and almost nine times more than the same month in 2018. Earth.Org has compiled satellite images capturing the fires. 

The Arctic is warming twice as fast as the rest of the world. With the rise in temperature and heat comes increased dryness, causing the soil and permafrost to lose their moisture. This extreme dryness, combined with the rise in temperature, creates an optimum environment for wildfires to flourish. Dried peat is of particular concern as the large amounts of stored carbon allow it to burn rapidly and efficiently. 

The region is considered a tundra biome: a cold, dry desert with sparse vegetation apart from shrubs and mosses. Underground, permafrost resides, which significantly slows down the rate of peat decomposition, storing carbon as a result. When it thaws however, methane is released, making the conservation of peatlands vital.

Arctic Heatwave

Europe’s Copernicus Atmosphere Monitoring Service shows that the fire activity has been further to the east in the Siberian Arctic than in 2019, with more widespread fires in the non-Arctic parts of eastern Siberia. Mark Parrington, CAMS senior scientist, says, “It is very surprising how similar the daily trend in the fire activity has been compared to 2019, especially as it is so unusual to all the other years of data that we have.”

Throughout the heatwave, some parts of the Arctic registered temperatures as much as 16℃ higher than usual in May.

The fire season typically starts in early May and picks up at the beginning of June, but it started earlier this year, with satellites registering wildfires as soon as March. Fires generally burn through forests and peatlands in Siberia. The dry vegetation on these plains can burn under the snowpack of winter and satellite data suggested that high temperatures were reigniting these ‘zombie fires’. The warm air spreading from Siberia across the Arctic doesn’t directly cause fires, but together with low soil moisture levels and low precipitation, it can contribute to conditions conducive for fires to spread. 

The summer of 2019 endured record-breaking levels of smoke and smog throughout the Arctic tundra and surrounding forests. In just two months, it was estimated that approximately 100 intense wildfires spanned Alaska, Siberia, Canada and Greenland, with some reported to be ‘as big as 100 000 football fields’. In Siberia alone, the wildfires burned for 3 months and consumed over 4 million hectares of forest. 

As the areas within and surrounding the Arctic Circle tend to be remote, fires can burn indefinitely, jeopardising carbon stores and releasing greenhouse gases into the atmosphere that have knock-on effects on the rest of the world

“Fires are a natural part of the ecosystem, but what we’re seeing is an accelerated fire cycle: we are getting more frequent and severe fires and larger burned areas,” said Liz Holy, a researcher at NASA’s Goddard Space Flight Centre in Maryland.

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arctic wildfires
Fire occurrence in North-Eastern Russia between the 7th of June and 7th of July, from 2017 to 2020. Retrieved using the NASA FIRMS fire detection system.

Siberia

This summer, the fires have already burned through 333 000 hectares of land, according to Greenpeace. On June 20, the meteorological service of Russia recorded a peak of 38 in Verkhoyansk, the highest recorded temperature since records began in the late nineteenth century. Siberia is renowned for having a wildly fluctuating climate, holding the world record for temperatures ranging from -68 to 37

Climate scientists have stressed how ‘alarm bells should already be ringing’- especially in response to the catastrophic effects the Arctic wildfires will have on amplifying the rate of global warming

Another component essential for the unprecedented levels of wildfires in the Arctic is the number of storms prevalent. Between the years 2012 and 2018, a total of only 3 lightning strikes were recorded in regions close to the Arctic Ocean. However in 2019, a two-day period produced approximately 48 lightning strikes. The combination of lightning and dried earth propagates the energy and fuel required to start fires.

Moreover, the soot produced by the Arctic’s wildfires can be detrimental to humans and animals alike, inducing fatal chronic health conditions such as asthma attacks and strokes. The soot also contributes to the rising temperatures of the Arctic by settling on layers of ice and decreasing the albedo value of such surfaces- resulting in an increase in heat absorption and a decrease in light reflection, and therefore reinforcing the Arctic warming cycle.

Estimates from 2019

According to an article published by Harvard University, one peat fire can produce approximately 80 tons of carbon per acre, the equivalent of ‘the annual emissions of around 20 cars’. Estimates  suggest that the Arctic wildfires in 2019 produced a total of approximately 140 million metric tons of greenhouse gas emissions- the equivalent to ‘the annual emissions of over 20 million cars’. 

Though predictions are not always accurate, and have previously underestimated the fires which occurred last year, they do help researchers understand what is yet to come. Satellite images assist to monitor the fires by allowing experts to analyse characteristic smoke patterns and to measure heat output

In addition to reducing human activities that dehydrate the Arctic fringes, researchers suggest ‘actively re-wetting the peatlands and removing plants that could fuel a fire and replacing them with mosses that can keep the ground wet’. Though this method has not been tested on a large scale, such innovation demonstrates that attempts of combating and mitigating the Arctic wildfire problem is hopefully underway.


Featured image by: Western Arctic National Parklands

Antarctica experienced unprecedented heat this summer, with a heatwave that began in late spring in the Antarctic Peninsula and circumnavigated the continent over the next four months. Since the late 19th century, the planet has warmed by roughly 0.8°C. Scientists predict that the Earth’s temperature may increase by 3-5°C by the end of the century. This poses a massive problem for the fastest-warming regions on Earth, one of which is the Antarctic Peninsula. What does it mean when the coldest place on Earth heats up?

While isolated from the rest of the world, Antarctica drives the global ocean conveyor belt, a constantly moving system of deep-ocean circulation which transfers oceanic heat around the planet; Antarctica demonstrates the patterns of change that we can expect to see in other parts of the world.

According to the World Meteorological Organization (WMO), the Esperanza research base on the Antarctic Peninsula reported a temperature of 18.4°C on February 6, the hottest on record for the continent, which was eclipsed three days later, when a nearby research station recorded a temperature of 20.75°C, the continent’s first time to exceed 20°C in recorded history. 

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What Caused the Heatwave in Antarctica?

The Casey Station recorded a heatwave from January 23 to 26; on January 24, the maximum temperature was 9.3°C, almost 7°C above the Station’s 30-year mean for the month.

The arrival of warm, moist air amid this weather brought rain to the Davis Research Station in the normally cold desert of the Vestfold Hill. These conditions spurred meltwater pools and surface streams on local glaciers. These, along with melting snowbanks, contributed to high-flowing rivers and flooding lakes.

Antarctica Melting Rate

Further, the amount of ice flowing from the Thwaites Glacier, one of the biggest culprits in rising sea levels, has nearly doubled over the last three decades. A 2018 study reveals that ice shelf collapse from 1992 to 2017 increased the Antarctic Peninsula ice loss rate from 7 to 33 billion tons a year. 

In January, researchers recorded what they consider to be the biggest widespread melting of the George VI ice shelf, which is right beside the Antarctic Peninsula. The exact reason for this is unknown, but scientists surmise that the warm temperature likely affects other Antarctic regions as well.

Satellite images from February 2019 to February 2020 revealed that a huge iceberg from the Pine Island Glacier broke off into smaller pieces. This unprecedented heatwave in Antarctica and the sea level rise driven by the melting of the glaciers will lead to disastrous consequences. 

NASA’s Earth Observatory also reports that Antarctica’s warm temperatures began on February 5 and lasted until February 13, the period when the hottest temperature was recorded on the Esperanza base.

The weakened state of the Southern Hemisphere westerlies due to Antarctic Oscillation is a big factor as it normally shields warm weather from being transported from Earth’s temperate regions to the Antarctic Peninsula. The polar cyclone is at its maximum intensity during the winter and it reaches its weakest during the summer, weakening the westerlies. Dry and warm foehn winds may have also contributed as they release heat into the air. 

The late Indian monsoon retreat, the most delayed it has been in 60 years, caused the water in the Indian Ocean to be warmer than usual as an effect of the ‘positive’ state of the Indian Ocean Dipole (IOD). This positive IOD may have lasted until January, also contributing to the warmer temperature in the Antarctic regions. 

High-temperature trends in the Antarctic Peninsula give a clearer depiction of the continent’s climate, which is essential in observing rising sea levels and global warming conditions. An increase in these trends will cause further melting of the glaciers which intensifies extreme events brought about by the climate crisis.

According to WMO Deputy Secretary-General Elena Manaenkova, every seemingly insignificant degree of global warming will affect food security, access to clean water, species extinction and economic productivity. In addition to this, Pacific Island nations, such as Kiribati and Samoa, and coastal communities will most likely be displaced.

A paper by the WWF says that a 4°C increase in global temperature would melt nearly all the glaciers on Earth. Ocean warming may have caused more than half of Antarctica’s total ice loss during the last few years, especially in the eastern Antarctic Peninsula.

“It is worth repeating once again that we are the first generation to fully understand climate change and the last generation to be able to do something about it,” said WMO Secretary-General Petteri Taalas.

Since the 19th century, the global average sea level has increased by over 15cm. Concrete and realistic plans by global leaders paired with transformative climate action would address the current climate crisis. These events highlight how interconnected our climate systems are, from the surface to the stratosphere and from the monsoon tropics to the southernmost continent. An unprecedented heatwave in Antarctica is a sign of things to come for the rest of the planet and to avoid irreversible and devastating impacts, there is no better time to act than the present.

Featured image by: Daniel Enchev

Heatwaves, also known as discrete extreme warming events, are becoming more frequent, more intense and are lasting longer because of human-induced climate change, devastating oceans, according to a recent study published in Nature Climate Change.

What are marine heatwaves?

Marine heatwaves, where an ocean’s surface temperature is much warmer than normal, have also intensified, damaging ocean-dwelling ecosystems worldwide.

The study found this phenomenon to be the principal cause of problems for many biological processes and organisms, including critical foundation taxa such as corals that support ecosystems and provide important ecological services.

“The major concern is that the oceans have warmed significantly as a consequence of manmade climate change, so that marine heatwaves have become more frequent and will likely intensify over the coming decades,” said Dan Smale from the University of Western Australia and lead author of the paper. “Just as atmospheric heatwaves can destroy crops, forests and animal populations, marine heatwaves can devastate ocean ecosystems.”

Why are oceans heating up?

Marine heatwaves can be caused by many factors including localised air-sea heat fluxes, where heat from the atmosphere is transferred to the sea, and large-scale climate drivers such as the El Nino Southern Oscillation (ENSO) that occurs when low-level surface winds that normally blow from east to west are weakened.

Although extreme warming events can occur naturally, growing evidence suggests that the intensification of heatwaves in recent years is attributable to human activities.

Researchers looked for areas where marine heatwave intensification overlapped with areas of high biodiversity, temperature-sensitive populations and non-climatic human stressors and found several vulnerable regions.

These include Australia, the Caribbean Sea and the mid-Eastern Pacific coastline with high marine biodiversity, along with the South-West Pacific and mid-West Atlantic with high temperature-sensitive populations.

Populations and species that live near their warm range edge – the warmest temperatures they can endure – are particularly vulnerable as intense marine heatwaves expose them to temperatures they cannot tolerate.

Overfishing and pollution also place additional stress on marine diversity in regions that are already subject to intense marine heatwaves such as the central-West Atlantic, the North-East Atlantic and the North-West Pacific.

“Ocean ecosystems currently face a number of threats, including overfishing, acidification and plastic pollution, but periods of extreme temperatures can cause rapid and profound ecological changes, leading to loss of habitat, local extinctions, reduced fisheries catches and altered food webs,” Dr Smale said.

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Shark Bay in Australia, one of the world’s largest intact seagrass regions was hammered in a marine heatwave that lasted two months in the summer of 2010-11. This event alone released the CO2 equivalent of 1.6 million cars. – BY PAUL LAVERY

Moreover, the authors conducted a meta-analysis on the ecological impacts of eight prominent marine heatwave events, reviewing more than 100 scientific research papers.

They found that all marine taxonomic groups, with the exception of fish and mobile invertebrates, responded negatively to marine heatwaves. Birds and corals were the most adversely affected due to changes in prey availability and widespread bleaching respectively.

Coral bleaching along with moribund seagrass and decreased kelp biomass have also all been linked to temporary highs in water temperature. These three foundational taxa play a crucial role in supporting underwater ecosystems and provide important ecological services like carbon sequestration and nutrient cycling.

To date, most ecological studies have focused on the long-term trends of climate change. The authors of this paper have instead shown the dramatically immediate consequences of heatwaves on our oceans.

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