Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month

Dana M Bergstrom, University of Wollongong; Andrew Klekociuk, University of Tasmania; Diana King, University of Wollongong, and Sharon Robinson, University of Wollongong

While the world rightfully focuses on the COVID-19 pandemic, the planet is still warming. This summer’s Antarctic weather, as elsewhere in the world, was unprecedented in the observed record.

Our research, published today in Global Change Biology, describes the recent heatwave in Antarctica. Beginning in late spring east of the Antarctic Peninsula, it circumnavigated the continent over the next four months. Some of our team spent the summer in Antarctica observing these temperatures and the effect on natural systems, witnessing the heatwave first-hand.

Antarctica may be isolated from other continents by the Southern Ocean, but has worldwide impacts. It drives the global ocean conveyor belt, a constant system of deep-ocean circulation which transfers oceanic heat around the planet, and its melting ice sheet adds to global sea level rise.

Antarctica represents the simple, extreme end of conditions for life. It can be seen as a ‘canary in the mine’, demonstrating patterns of change we can expect to see elsewhere.

A heatwave in the coldest place on Earth

Most of Antarctica is ice-covered, but there are small ice-free oases, predominantly on the coast. Collectively 0.44% of the continent, these unique areas are important biodiversity hotspots for penguins and other seabirds, mosses, lichens, lakes, ponds and associated invertebrates.

This summer, Casey Research Station, in the Windmill Islands oasis, experienced its first recorded heat wave. For three days, minimum temperatures exceeded zero and daily maximums were all above 7.5°C. On January 24, its highest maximum of 9.2°C was recorded, almost 7°C above Casey’s 30-year mean for the month.

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The arrival of warm, moist air during this weather event brought rain to Davis Research Station in the normally frigid, ice-free desert of the Vestfold Hills. The warm conditions triggered extensive meltwater pools and surface streams on local glaciers. These, together with melting snowbanks, contributed to high-flowing rivers and flooding lakes.

By February, most heat was concentrated in the Antarctic Peninsula at the northernmost part of the continent. A new Antarctic maximum temperature of 18.4°C was recorded on February 6 at Argentina’s Esperanza research station on the Peninsula – almost 1°C above the previous record. Three days later this was eclipsed when 20.75°C was reported at Brazil’s Marambio station, on Seymour Island east of the Peninsula.

What caused the heatwave?

The pace of warming from global climate change has been generally slower in East Antarctica compared with West Antarctica and the Antarctic Peninsula. This is in part due to the ozone hole, which has occurred in spring over Antarctica since the late 1970s.

The hole has tended to strengthen jet stream winds over the Southern Ocean promoting a generally more ‘positive’ state of the Southern Annular Mode in summer. This means the Southern Ocean’s westerly wind belt has tended to stay close to Antarctica at that time of year creating a seasonal ‘shield’, reducing the transfer of warm air from the Earth’s temperate regions to Antarctica.

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But during the spring of 2019 a strong warming of the stratosphere over Antarctica significantly reduced the size of the ozone hole. This helped to support a more ‘negative’ state of the Southern Annular Mode and weakened the shield.

Other factors in late 2019 may have also helped to warm Antarctica. The Indian Ocean Dipole was in a strong ‘positive’ state due to a late retreat of the Indian monsoon. This meant that water in the western Indian Ocean was warmer than normal. Air rising from this and other warm ocean patches in the Pacific Ocean provided energy sources that altered the path of weather systems and helped to disturb and warm the stratosphere.

Is a warming Antarctica good or bad?

Localised flooding appeared to benefit some Vestfold Hills’ moss banks which were previously very drought-stressed. Prior to the flood event, most mosses were grey and moribund, but one month later many moss shoots were green.

Given the generally cold conditions of Antarctica, the warmth may have benefited the flora (mosses, lichens and two vascular plants), and microbes and invertebrates, but only where liquid water formed. Areas in the Vestfold Hills away from the flooding became more drought-stressed over the summer.

High temperatures may have caused heat stress in some organisms. Antarctic mosses and lichens are often dark in colour, allowing sunlight to be absorbed to create warm microclimates. This is a great strategy when temperatures are just above freezing, but heat stress can occur once 10°C is exceeded.

On King George Island, near the Antarctic Peninsula, our measurements showed that in January 2019 moss surface temperatures only exceeded 14°C for 3% of the time, but in 2020 this increased fourfold (to 12% of the time).

Based on our experience from previous anomalous hot Antarctic summers, we can expect many biological impacts, positive and negative, in coming years. The most recent event highlights the connectedness of our climate systems: from the surface to the stratosphere, and from the monsoon tropics to the southernmost continent.

Under climate change, extreme events are predicted to increase in frequency and severity, and Antarctica is not immune.

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Dana M Bergstrom, Principal Research Scientist, University of Wollongong; Andrew Klekociuk, Adjunct Senior Lecturer, University of Tasmania; Diana King, Research officer, University of Wollongong, and Sharon Robinson, Professor, University of Wollongong

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

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The world’s best fire management system is in northern Australia, and it’s led by Indigenous land managers

Rohan Fisher, Charles Darwin University and Jon Altman, Australian National University

The tropical savannas of northern Australia are among the most fire-prone regions in the world. On average, they account for 70% of the area affected by fire each year in Australia.

But effective fire management over the past 20 years has reduced the annual average area burned – an area larger than Tasmania. The extent of this achievement is staggering, almost incomprehensible in a southern Australia context after the summer’s devastating bushfires.

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The success in northern Australia is the result of sustained and arduous on-ground work by a range of landowners and managers. Of greatest significance is the fire management from Indigenous community-based ranger groups, which has led to one of the most significant greenhouse gas emissions reduction practices in Australia.

As Willie Rioli, a Tiwi Islander and Indigenous Carbon Industry Network steering committee member recently said:

Fire is a tool and it’s something people should see as part of the Australian landscape. By using fire at the right time of year, in the right places with the right people, we have a good chance to help country and climate.

Importantly, people need to listen to science – the success of our industry has been from a collaboration between our traditional knowledge and modern science and this cooperation has made our work the most innovative and successful in the world.

A tinder-dry season

The 2019 fire season was especially challenging in the north (as it was in the south), following years of low rainfall across the Kimberly and Top-End. Northern Australia endured tinder-dry conditions, severe fire weather in the late dry season, and a very late onset of wet-season relief.

Despite these severe conditions, extensive fuel management and fire suppression activities over several years meant northern Australia didn’t see the scale of destruction experienced in the south.

A comparison of two years with severe fire weather conditions. Extensive early dry season mitigation burns in 2019 reduced the the total fire-affected areas.

This is a huge success for biodiversity conservation under worsening, longer-term fire conditions induced by climate change. Indigenous land managers are even extending their knowledge of savanna burning to southern Africa.

Burn early in the dry season

The broad principles of northern Australia fire management are to burn early in the dry season when fires can be readily managed; and suppress, where possible, the ignition of uncontrolled fires – often from non-human sources such as lightning – in the late dry season.

Traditional Indigenous fire management involves deploying “cool” (low intensity) and patchy burning early in the dry season to reduce grass fuel. This creates firebreaks in the landscape that help stop larger and far more severe fires late in the dry season.

Relatively safe ‘cool’ burns can create firebreaks.
Author provided

Essentially, burning early in the dry season accords with tradition, while suppressing fires that ignite late in the dry season is a post-colonial practice.

Savannah burning is different to burn-offs in South East Australia, partly because grass fuel reduction burns are more effective – it’s rare to have high-intensity fires spreading from tree to tree. What’s more, these areas are sparsely populated, with less infrastructure, so there are fewer risks.

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Satellite monitoring over the last 15 years shows the scale of change. We can compare the average area burnt across the tropical savannas over seven years from 2000 (2000–2006) with the last seven years (2013–2019). Since 2013, active fire management has been much more extensive.

The comparison reveals a reduction of late dry season wildfires over an area of 115,000 square kilometres and of all fires by 88,000 square kilometres.

How fire has changed in northern Australia.
Author provided

Combining traditional knowledge with western science

The primary goals of Indigenous savanna burning projects remain to support cultural reproduction, on-country living and “healthy country” outcomes.

Savanna burning is highly symbiotic with biodiversity conservation and landscape management, which is the core business of rangers.

Ensuring these gains are sustainable requires a significant amount of difficult on-ground work in remote and challenging circumstances. It involves not only Indigenous rangers, but also pastoralists, park rangers and private conservation groups. These emerging networks have helped build new savanna burning knowledge and innovative technologies.

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While customary knowledge underpins much of this work, the vast spatial extent of today’s savanna burning requires helicopters, remote sensing and satellite mapping. In other words, traditional burning is reconfigured to combine with western scientific knowledge and new tools.

For Indigenous rangers, burning from helicopters using incendiaries is augmented by ground-based operations, including on-foot burns that support more nuanced cultural engagement with country.

On-ground burns are particularly important for protecting sacred sites, built infrastructure and areas of high conservation value such as groves of monsoonal forest.

Who pays for it?

A more active savanna burning regime over the last seven years has led to a reduction in greenhouse gas emissions of more than seven million tonnes of carbon dioxide equivalent.

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Savanna burning: carbon pays for conservation in northern Australia

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This is around 10% of the total emission reductions accredited by the Australian government through carbon credits units under Carbon Farming Initiative Act. Under the act, one Australian carbon credit unit is earned for each tonne of carbon dioxide equivalent that a project stores or avoids.

By selling these carbon credits units either to the government or on a private commercial market, land managers have created a A$20 million a year savanna burning industry.

How Indigenous Australians and others across Australia’s north are reducing emissions.

What can the rest of Australia learn?

Savanna fire management is not directly translatable to southern Australia, where the climate is more temperate, the vegetation is different and the landscape is more densely populated. Still, there are lessons to be learnt.

A big reason for the success of fire management in the north savannas is because of the collaboration with scientists and Indigenous land managers, built on respect for the sophistication of traditional knowledge.

This is augmented by broad networks of fire managers across the complex cross-cultural landscape of northern Australia. Climate change will increasingly impact fire management across Australia, but at least in the north there is a growing capacity to face the challenge.

Rohan Fisher, Information Technology for Development Researcher, Charles Darwin University and Jon Altman, Emeritus professor, School of Regulation and Global Governance, ANU, Australian National University

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