The Arctic and Antarctic are changing rapidly in response to global warming, with scientists striving to understand how escalating impacts on these unique regions impact the rest of the world. This story summarizes three significant recent studies.A new comprehensive greenhouse gas budget for Arctic terrestrial ecosystems estimates that the permafrost-covered region now emits more greenhouse gases — including carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) — than it stores. That trend is expected to accelerate if Arctic warming worsens further.Another recent study looked at the ice shelves edging the Antarctic continent, which act as brakes slowing the flow of glacial ice into the ocean that adds to sea-level rise. Although many factors impact the mass and stability of these shelves, a new model shows El Niño warming events help melt ice from below to increase shelf loss.Scientists also analyzed a record-breaking heat wave hitting Antarctica in March 2022, when temperatures soared by up to 40°C (72°F) above normal. They determined that this “black swan” event is having long-term impacts on the region’s ecosystems. The odds are that more such high-heat events will occur in future.
Most of us will never travel to Earth’s poles, but every creature on this planet will likely experience the consequences of escalating global warming in the polar north and south.
Rapidly rising temperatures are radically altering the freezing, melting and precipitation patterns in the polar regions. And there’s strong evidence those changes don’t stay in the Arctic or Antarctic, but resonate across the world.
Scientists now know that events in the far north and south affect global weather, sea level rise, biodiversity, ocean currents and more. Three recent studies add new insights about the effects of warming in the coldest places on Earth — and, by extension, on all of us.
Aerial view of a permafrost thaw slump on Herschel Island (Nunataryuk project), Unorganized Yukon, Canada. Arctic permafrost can store greenhouse gases for many centuries, but when that permafrost melts it releases those gases and they add to global climate change. Image by GRID-Arendal via Flickr (CC BY-NC-SA 2.0).
Arctic shifting from greenhouse gas sink to source
For centuries, the Arctic landscape has been a reliable long-term repository for greenhouse gases that, if released in large amounts into the atmosphere in coming years, could significantly accelerate global warming. But since the late 1970s, the Arctic has warmed at least twice — and perhaps almost four times — as fast as the rest of the world, leading to more thawed permafrost, raging record wildfires, and drastic terrain alterations.
In March 2024, scientists released a new study of this changing landscape that compared estimated emission releases versus uptake of three powerful greenhouse gases — carbon dioxide, methane and nitrous oxide — from 2000-2020.
They scaled up observational data from more than 1,000 in-situ flux monitoring sites scattered across five types of terrestrial ecosystems, and found that the comprehensive greenhouse gas (GHG) budget across the Arctic permafrost region has significantly shifted.
This Arctic region is no longer a greenhouse gas sink, and is becoming a source; it emitted an estimated 147 million metric tons of greenhouse gases during the first two decades of the 21st century.
The permafrost area in this study covers 18.5 million km2 (7.1 million mi2). The Boreal Arctic Wetlands and Lakes Data set (BAWLD) land cover classes are distinguished based on moisture regime, nutrient/pH regime, organic-soil depth, hydrodynamics, and the presence or absence of permafrost. To match the observational GHG flux data sets in the study, the nine terrestrial land cover classes in BAWLD were simplified into five: boreal forests, non-permafrost wetlands, dry tundra, tundra wetlands, and permafrost bogs. This permafrost regional budget is part of the RECCAP2 (REgional Carbon Cycle Assessment and Processes‐2) project of the Global Carbon Project that aims to collect and integrate regional GHGs budgets for 12 land regions and 5 ocean basins covering all global lands and oceans. Image courtesy of Ramage et al. (2024).
The highest carbon dioxide emissions over that period came from inland rivers and wildfires. The non-permafrost wetlands exhaled the most methane, and dry tundra released the most nitrous oxide.
“The results were not surprising,” said study lead author Justine Ramage, a physical geographer and postdoctoral researcher at Stockholm University in Sweden. “What was disturbing was that abrupt events such as fires and thaws are causing a big shift.”
Although the balance sheets showed negative numbers for CO2, indicating the Arctic still appears to be a carbon dioxide sink — especially in boreal forests — the study authors noted that large statistical uncertainties in the data make it more likely that carbon dioxide storage in permafrost is closer to a neutral status.
The analysis did not include subsea permafrost emissions or permafrost areas in Central Asia or the Tibetan plateau. Nor did the study estimate anthropogenic disturbances such as clear-cutting and other logging.
“This study advances our understanding of how CO2, CH4, and N2O fluxes come together for the permafrost region, after including inland waters (large sources of methane) and disturbances — both which were previously missing from the regional budget,” wrote Katey Walter Anthony in an email to Mongabay. She is a professor of aquatic ecology, biogeochemistry and permafrost science at the University of Alaska Fairbanks, and was not involved in the study.
Researchers say the accuracy of the GHG budget can be improved by increasing the amount of observational data and getting more detailed descriptions for ecosystem categories; difficult tasks in such a vast and inhospitable region, said Ramage.
The shift from terrestrial GHG sink to source is a bad sign for both the Arctic and for us, though more research will be needed to model how fast this change will unfold and how much it will impact the global climate.
The annual atmospheric greenhouse gases (GHGs) exchange (CO2, CH4 and N2O) for the five terrestrial land cover classes (boreal forests (9.0 × 106 km2), non‐permafrost wetlands (1.6 × 106 km2), dry tundra (5.2 × 106 km2), tundra wetlands (0.4 × 106 km2) and permafrost bogs (0.9 × 106 km2)); inland water classes (rivers (0.1 × 106 km2) and lakes (1.3 × 106 km2)). Annual lateral fluxes from coastal erosion and riverine fluxes are also reported in Tg C yr− 1 and Tg Nyr−. Note: magnitudes across the three different GHG fluxes within each land cover class cannot be compared with each other. Image courtesy of Ramage et al. (2024).
The El Niño–Antarctic connection
While the Arctic has been observed to be warming faster than the rest of the world for decades, scientists surmised that the massive Antarctic ice sheet had been mostly resistant to warming, and would be slower to succumb to climate change.
But satellite altimetry studies show that the West Antarctic ice sheet has been steadily losing mass. Likewise, the floating ice shelves along the Antarctic ice sheet’s edges are getting thinner, reducing their ability to slow the flow of on-land glaciers into the sea, which contributes directly to sea level rise.
One factor known to increase West Antarctic ice shelf melt is the El Niño–Southern Oscillation (ENSO), which every few years warms surface waters in the central and eastern Pacific Ocean, raises sea levels, disrupts global weather patterns, and causes coral bleaching.
A satellite study in 2018 found that although El Niño events can increase snowfall which adds mass atop ice shelves, the warmer waters under the shelves melts even more ice from below.
In a new study, researchers used ocean circulation models to isolate the impact of El Niño on ice shelf melt and determine how it intensifies melt from below.
“There’s a lot going on at the same time. We wanted to look at El Niño because, on the year-to-year timescale, it has the biggest impact [on ice shelf] melting,” said lead author Maurice Huguenin, a physical oceanographer and research associate for the Australian Centre for Excellence in Antarctic Science in Sydney.
A portion of the Antarctic Peninsula, seen from above, is one of the fastest-changing regions of the continent. The Antarctic ice sheet is a massive (14 million square kilometers) frozen reservoir holding well over half the world’s freshwater. There are 300 ice shelves that edge the continent that buttress and brake the glaciers keeping them from sliding into the sea. Understanding the factors that affect ice shelf thickness can help scientists assess the impact on global sea levels. Image courtesy of NASA/K. Ramsayer.
“We have known about the relationship between ENSO variability and changes in local atmospheric and oceanic conditions in West Antarctica affecting ice shelf melting,” said Fernando Paolo, senior machine-learning engineer for Global Fishing Watch, who previously studied Antarctic ice shelf loss using satellite data, and was not involved in the research. “The study expands on the actual mechanism by which local oceanic conditions during El Niño events promote influxes of warm circumpolar deep water underneath the ice shelves, increasing basal melting, with the opposite occurring during La Niña events.”
The findings are also another line of evidence that El Niño not only affects tropical and temperate environments, but, through atmospheric teleconnection, also impacts Antarctic climate, wrote Wenju Cai, a climate change expert and former senior researcher at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia, who was not involved in the study.
Huguenin cautions that the Antarctic reality might differ from the model: Depending on the region’s storms or other simultaneously occurring factors, a particular El Niño may not necessarily lead to more ice shelf melting.
Simplified diagram of physical changes on the West Antarctic continental shelf during El Niño events. “Our models show that during El Niño, the on-shelf flow of cold surface waters in West Antarctica, driven by coastal easterly winds, is reduced because the winds weaken. To balance out this mass deficit at the surface, more warm water flows onto the continental shelf below,” said researcher Maurice Huguenin. During a La Niña event, a largely opposite response occurs. Image courtesy of Huguenin et al. (2024).
When heat waves hit the coldest continent
Global warming is now regularly bringing more intense and unexpected weather events to the south polar region, like the record-breaking heat wave that hit East Antarctica in mid-March 2022, with temperatures 30-40° Celsius (54-72° Fahrenheit) higher than normal.
Although the heat wave only lasted a few days, and never climbed above -9.4°C (15.1°F), scientists found that the temperature swing had long-term impacts on the environment and left researchers with worrying questions over the likelihood of more such events in the future.
“Just because it’s an anomalous event doesn’t mean it can’t have big impacts,” said Jonathan Wille, a meteorologist and climatologist at the ETH Institute for Atmospheric and Climate Science in Zurich, who led a collaboration of 54 other scientists from 14 countries who analyzed the “black swan” heat wave. “The real challenge was to put it in context. We need to understand how extreme weather events like this will impact the long-term health of the Antarctic ice sheet,” Wille said.
In a two-part study, researchers first analyzed global weather records to identify how cyclones coupled with blocking conditions along the Antarctic coastline can combine to deliver an epic atmospheric river across 3.3 million square kilometers (almost 1.3 million square miles) of the southern continent.
The second study identified a range of impacts, including a positive annual surface mass balance for the Antarctic ice sheet due to increased snowfall; the collapse of the already weakened Conger/Glenzer ice shelf (which was aided by extra-intense ocean swells and surface winds); further declines in sea ice and fast-ice extents that were already at record-breaking minimums.
“These climate anomalies, and specifically in this case, atmospheric rivers, have important influences on the cryosphere,” noted Jeb Barrett, a soil ecologist and biochemist at Virginia Tech who was not involved in the research. “But these extreme weather events also have important influences on the hydrology and ecosystems where they occur.” Barrett has studied soil roundworms, tardigrades and microbial mats in the Antarctic’s McMurdo Dry Valleys for 25 years.
Hourly snow temperature measurements at Concordia Station using Pt100 sensors. On March 18, 2022, the hottest day of the heat wave, the temperature rose to -9.4°C (15.1°F), well above the typical -54°C (-65.2°F) average for March in Antarctica. Image courtesy of Wille et al. (2024).
Adélie penguin (Pygoscelis adeliae) on iceberg. A fatal temperature swing and precipitation led to 100% chick mortality during the 2013/14 breeding season of the Adélie penguin colony on Petrel Island at Pointe Géologie. An extra-cold fall and winter created extreme sea ice extents that forced adult penguins to walk farther to forage, depleting their energy and ability to feed their chicks. Then an unusually warm Antarctic summer brought heavy rains that soaked the downy plumage of the chicks, leaving them too cold to survive. Image by jean wimmerlin via Unsplash (Public domain).
In March, when East Antarctic temperatures typically plummet and streams run dry, the tiny organisms Barrett studies are adapted to spend the winter in a “freeze-dried” state. But the heat wave kept water in the streams, something never recorded in the 30-year database. Such extreme events can change the life history of these animals, said Barrett.
The timing of anomalous events is probably just as important as their magnitude, Barrett added. If the heat wave hits in Antarctica’s summer, the temperature swings aren’t as wild, but can cause much more damage to sensitive areas such as Thwaite’s Glacier, one of Antarctica’s most threatened glaciers, which already contributes 4% to annual global sea level rise and holds enough ice to raise sea levels by more than 60 centimeters (2 feet).
But a “weather whiplash” event — going from one extreme to another at a vulnerable time — can have severe effects, as occurred when heavy precipitation during the 2013/14 breeding season of an Adélie penguin colony on Petrel Island, left all the chicks dead.
“Loss of sea ice mass, the mortality and life-cycle effects on biological populations; these are the kinds of impacts that put anomalous events in greater perspective,” said Barrett.
As the world warms, researchers will continue monitoring climate change’s effects on the cryosphere — and the changing cryosphere’s impacts on the rest of the world.
Banner image: A multilayered lenticular cloud hovers near Mount Discovery, a volcano about 70 km (44 mi) southwest of McMurdo Station in Antarctica. The bulging sea ice in the foreground is a pressure ridge, formed when separate ice floes collided and piled up on each other. Image courtesy of NASA Earth Observatory/Adam Voiland.
Report ranks 60+ ideas, including geoengineering, to save the Arctic
Citations:
Rantanen, M., Karpechko, A. Y., Lipponen, A., Nordling, K., Hyvärinen, O., Ruosteenoja, K., … Laaksonen, A. (2022). The Arctic has warmed nearly four times faster than the globe since 1979. Communications Earth & Environment, 3(1). doi:10.1038/s43247-022-00498-3
Ramage, J., Kuhn, M., Virkkala, A., Voigt, C., Marushchak, M. E., Bastos, A., … Hugelius, G. (2024). The net GHG balance and budget of the permafrost region (2000-2020) from ecosystem flux upscaling. Global Biogeochemical Cycles, 38(4). doi:10.1029/2023gb007953
Otosaka, I. N., Shepherd, A., Ivins, E. R., Schlegel, N. J., Amory, C., van den Broeke, M., … Wouters, B. (2022). Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020. Earth System Science Data, 15, 1597-1616. doi:10.5194/essd-15-1597-2023
Paolo, F. S., Fricker, H. A., & Padman, L. (2015). Volume loss from Antarctic ice shelves is accelerating. Science, 348(6232), 327-331. doi:10.1126/science.aaa0940
Paolo, F. S., Padman, L., Fricker, H. A., Adusumilli, S., Howard, S., & Siegfried, M. R. (2018). Response of Pacific-sector Antarctic ice shelves to the El Niño/Southern Oscillation. Nature Geoscience, 11(2), 121-126. doi:10.1038/s41561-017-0033-0
Huguenin, M. F., Holmes, R. M., Spence, P., & England, M. H. (2024). Subsurface warming of the West Antarctic continental shelf linked to El Niño–Southern Oscillation. Geophysical Research Letters, 51(7). doi:10.1029/2023gl104518
Wille, J. D., Alexander, S. P., Amory, C., Baiman, R., Barthélemy, L., Bergstrom, D. M., … Zou, X. (2024). The extraordinary March 2022 East Antarctica “heat” wave. Part I: Observations and meteorological drivers. Journal of Climate, 37(3), 757-778. doi:10.1175/JCLI-D-23-0175.1
Wille, J. D., Alexander, S. P., Amory, C., Baiman, R., Barthélemy, L., Bergstrom, D. M., … Zou, X. (2024). The extraordinary March 2022 East Antarctica “heat” wave. Part II: Impacts on the Antarctic ice sheet. Journal of Climate, 37(3), 779-799. doi:10.1175/JCLI-D-23-0176.1
Ropert‐Coudert, Y., Kato, A., Meyer, X., Pellé, M., MacIntosh, A. J., Angelier, F., … Raclot, T. (2014). A complete breeding failure in an Adélie penguin colony correlates with unusual and extreme environmental events. Ecography, 38(2), 111-113. doi:10.1111/ecog.01182
Carbon Conservation, Carbon Dioxide, Climate, Climate Change, Climate Change And Conservation, Climate Change And Extreme Weather, Climate Science, Conservation, Earth Science, Environment, Global Environmental Crisis, Global Warming, Impact Of Climate Change, Ocean Warming, Permafrost, Polar Regions, Research, Science, Sea Ice
Antarctica, Arctic, Arctic Ocean, Global
>>> Read full article>>>
Copyright for syndicated content belongs to the linked Source : MongaBay – https://news.mongabay.com/2024/05/polar-warning-warming-temperatures-mean-more-than-melted-ice/
