How are intense heat waves affecting life in Antarctica? 

The summer of 2024 is shaping up to be the hottest on record for numerous cities across the U.S. and globally, with temperatures reaching unprecedented levels. 

Even in Antarctica, which is currently in the middle of its winter, temperatures soared more than 50°F above the July average in some areas. This extreme weather event is part of a broader trend of intensifying heat waves fueled by climate change.

Delicate ecosystems of Antarctica 

A recent study published on July 31 in the journal Earth’s Future explores how such heat waves, particularly during Antarctica’s cold seasons, may impact the continent’s delicate ecosystems.

The research, led by scientists from the University of Colorado Boulder, focuses on how these heat waves could disrupt the lives of the animals and organisms that inhabit the coldest and driest places on Earth. 

The findings illustrate that climate change-driven extreme weather could have profound and long-lasting effects on the fragile ecosystems of Antarctica, particularly for its resilient yet vulnerable inhabitants.

Most intense heat wave on Earth

In March 2022, Antarctica experienced the most intense heat wave ever recorded on Earth. This unprecedented event occurred just as the region’s organisms were preparing for the long, harsh winter ahead. 

Temperatures soared more than 70°F above the average in parts of the continent, leading to rapid melting of glaciers and snow, even in the McMurdo Dry Valleys, a region known for being one of the coldest and driest places on the planet.

Microscopic organisms in soils 

As part of a Long-Term Ecological Research (LTER) project, researchers studied the impact of this sudden heat wave on the McMurdo Dry Valleys, where they found that the extreme weather likely disrupted the life cycles of many organisms. 

In particular, the rapid melting followed by an equally rapid refreeze appeared to have killed a significant number of invertebrates, such as roundworms, which are well-adapted to the harsh conditions of the polar desert.

“It’s important that we pay attention to these signals, even if they’re coming from microscopic organisms in soils in a polar desert,” said Michael Gooseff, senior author of the study and a professor in the Department of Civil, Environmental, and Architectural Engineering at CU Boulder. 

“They’re the early responders to changes that could cascade up to larger organisms, the landscape, and even us, far away from Antarctica.”

Extreme temperature rise 

Gooseff, a fellow at the Institute of Arctic and Alpine Research (INSTAAR), has led the LTER project at the McMurdo Dry Valleys for the past decade, regularly traveling to the southern region during the Antarctic summer to study the unique ecosystem. 

In November 2021, when Gooseff arrived in Antarctica, the landscape appeared much like it had for the past two decades.

However, by March 2022, when the research team had already left the continent, an atmospheric river – a massive storm carrying moist air over long distances – brought about the most extreme heat wave ever recorded there. 

The event caused temperatures in the McMurdo Dry Valleys to rise more than 45°F above normal, with air temperatures that typically hover around -4°F in March rising above freezing.

Disrupted life cycles

Satellite imagery and stream discharge measurements confirmed that the sudden warming caused an unusual wetting of the valleys’ soil, occurring more than two months after the typical summer thaw. 

This was a critical period when organisms in the region were preparing for the upcoming winter, shutting down their biological processes to conserve energy. 

The rapid rise and subsequent fall in temperatures, as the heat wave passed and the soil refroze, likely disrupted the delicate timing of these organisms’ life cycles.

“These animals invest a significant amount of energy in preparing and shutting down for the winter,” Gooseff explained. “When things start to warm up the following summer, they use energy to become active again.” 

“One of our major concerns with unusual weather events like this heat wave is that these animals might start using a lot more energy, thinking it’s summer, only to have to shut down again two days later. How many times can they go through that cycle before they exhaust their energy reserves?”

A false start to the summer

When Gooseff and his team returned to Antarctica in December 2022, they sampled the soil and compared the organisms in areas that had become wet during the heat wave with those in areas that had stayed dry. 

The findings revealed a 50% decrease in the population of Scottnema, a common roundworm species that is highly adapted to the extreme cold and dryness of the McMurdo Dry Valleys.

“The heat wave made the environment appear warm enough for things to get wet, creating a false start to summer. Some of the biology responding to these temperatures might be seriously disrupted by this,” Gooseff said. 

Implications for food webs

While species like Scottnema suffered, other organisms, such as tardigrades (also known as water bears), which are more tolerant of moisture, were likely less affected.

This shift in species populations could have wide-ranging implications for the region’s food webs and nutrient cycling.

Changes in the populations of organisms like Scottnema can have a significant impact on the ecosystem. Previous research has shown that Scottnema is responsible for about 10% of the carbon processing in the Dry Valleys’ soil ecosystem. 

Large species affected by heat waves in Antarctica 

As extreme weather events become more frequent due to climate change, larger species in Antarctica are also being affected.

In 2013, an unusual rainfall event along the Adélie Coast of East Antarctica killed all of the Adélie penguin chicks in the region, and in July 2024, temperatures in parts of East Antarctica climbed 50°F above the usual winter average.

Gooseff and his team plan to continue monitoring the effects of extreme weather events on Antarctica’s ecosystems.

As Gooseff noted, what happens in Antarctica does not stay in Antarctica. “The loss of ice shelves has pretty dramatic impacts on the mass balance of our oceans, and it affects us even thousands of miles away,” he concluded.

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