An atmospheric river transported warm, moist air into the coldest and driest parts of the planet in 2022, resulting in temperatures soaring 70 degrees above the norm. A recent study sheds light on the effects of this event on Antarctica’s smallest creatures.
The summer of 2024 is expected to set records as the hottest season for numerous cities worldwide, including many in the U.S. Even Antarctica faced remarkable heat, experiencing temperatures over 50°F above its typical July weather during the height of winter.
On July 31, a study published in the journal Earth’s Future by a team of scientists that includes researchers from the University of Colorado Boulder discussed how heat waves, particularly those in Antarctica’s colder seasons, can influence local animal life. This research highlights the potential effects that extreme weather events, amplified by climate change, could have on the delicate ecosystems of the continent.
In March 2022, Antarctica experienced the most severe heat wave ever recorded on Earth, just as organisms in the southern regions were preparing for the long and severe winter. The extraordinary weather caused temperatures to rise in parts of Antarctica to over 70°F above average, resulting in the melting of glaciers and snow, even in the McMurdo Dry Valleys, known as one of the planet’s coldest and driest regions.
As part of a Long-Term Ecological Research (LTER) initiative in Antarctica, the research group discovered that the unexpected melting followed by a quick refreeze likely interfered with the life cycles of many organisms, leading to significant mortality among various invertebrates in the McMurdo Dry Valleys.
“We must heed these signals, even if they are originating from tiny organisms in polar deserts,” stated Michael Gooseff, the lead author of the paper and a professor in the Department of Civil, Environmental, and Architectural Engineering at CU Boulder. “These organisms respond early to changes that can eventually affect larger species, the environment, and even humans far from Antarctica.”
Upon his arrival in Antarctica in November 2021, Gooseff observed that the continent had remained largely unchanged for the past twenty years. As a fellow at the Institute of Arctic and Alpine Research (INSTAAR), Gooseff has led the LTER project in the McMurdo Dry Valleys, funded by the National Science Foundation, for the past decade. Almost every Antarctic summer, he visits the region to study its ecosystem and how its organisms endure in harsh environmental conditions.
Though most animals find it difficult to survive the severe dryness and cold, some microorganisms and invertebrates, like roundworms and tardigrades (commonly known as water bears), thrive in this frozen habitat. Tardigrades are tiny, eight-legged creatures measuring between 0.002 and 0.05 inches long, and can withstand extreme temperatures ranging from -328°F to 300°F, conditions that would be fatal for most other life forms.
In February 2022, all members of the polar research team left Antarctica before the end of the summer season. A month later, the continent was hit by the most extreme heat wave recorded, fueled by a severe storm known as an atmospheric river, which delivered moist air from afar to the polar region.
Monitoring systems in the McMurdo Dry Valleys captured data showing that air temperatures, usually around -4°F in March, rose above freezing, exceeding the typical temperature by 45°F.
Satellite images and stream discharge readings indicated that the rapid warming caused the valleys’ soil to become wetter more than two months after the peak summer thaw, a period when the ground is usually dry.
Within just two days after the heat wave, temperatures fell dramatically and the soil froze again. This event occurred during a critical time when organisms were preparing for the long, dark winter. Gooseff and his colleagues were interested to see how the animals in the valleys reacted.
“These animals put considerable energy into preparing and shutting down for the winter,” noted Gooseff. “When temperatures rise the next summer, they expend energy to become active again. We are concerned that unusual weather events like this heat wave may cause these animals to overexert themselves, thinking it’s summer, only to find themselves having to shut down again just days later. How many times can they endure this cycle before depleting their energy stores?”
The team returned to Antarctica the following summer in December 2022, where they collected soil samples and compared the organisms in wet areas to those in dry regions during the heat wave.
They found a 50% drop in the population of Scottnema, a prevalent type of roundworm, in areas that became wet. Scottnema is specially adapted to the severe cold and dryness of the region.
“The heat wave created conditions that seemed warm enough for wetness, leading to a premature start to summer. The biological responses to these temperatures may be significantly disrupted,” Gooseff explained.
Rapid fluctuations between extreme weather conditions can disproportionately affect sensitive species like Scottnema, while other animals, including tardigrades, may be less impacted. These resilient creatures can tolerate increased moisture, allowing them to thrive as the environment becomes wetter.
“Changes in which species inhabit the soil and their population sizes can dramatically influence the ecosystem’s food web and nutrient cycling,” Gooseff added.
Previous studies have shown that Scottnema contributes to around 10% of the carbon processed in the soil ecosystem of the Dry Valleys.
As climate change worsens extreme weather patterns in Antarctica, larger animals are also affected. For instance, during the summer of 2013, an unprecedented rainfall event along East Antarctica’s Adélie Coast resulted in the complete loss of all Adélie penguin chicks in that area. In July, temperatures in certain parts of East Antarctica reached as high as 50°F above the usual winter average.
Gooseff and his team plan to keep observing extreme weather events and their effects on the Antarctic ecosystem.
“What occurs in Antarctica has repercussions beyond its borders,” Gooseff remarked.
“The melting of ice shelves has dramatic effects on the ocean’s mass balance, impacting us even from thousands of miles away.”
