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According to a study using satellite images, glacial lakes have grown rapidly around the world in the last three decades, showing the impact of increased meltwater draining off melting glaciers. 

The study, published in Nature Climate Change, entailed the team of scientists analysing more than 250 000 satellite images to assess how lakes formed by melting glaciers have been affected by global temperature rise.

Between 1990 and 2018, the number of glacial lakes has grown by 53%, expanding the amount of the planet covered by the lakes by about 51%. There are 14 394 glacial lakes spread over nearly 9 000 sq km of Earth’s surface. The researchers estimate that the volume of the world’s glacial lakes grew by 48% over this time and now hold 156.5 cubic km of water. 

Stephan Harrison, a professor of climate and environmental change at Exeter University and one of the researchers in the study, says, “Our findings show how quickly Earth surface systems are responding to climate change, and the global nature of this. More importantly, our results help to fill a gap in the science because, until now, it was not known how much water was held in the world’s glacial lakes.” 

You might also like: What Would Happen To The Climate If We Stopped Greenhouse Gas Emissions Immediately?

What are Glacial Lakes?

Glacial lakes are an important source of freshwater for many people around the world, particularly in Asia and parts of South America. However, they also present a growing risk from floods that can destroy villages, roads, pipelines and other infrastructure. 

The scientists highlight particular threats to hydroelectric power plants in the Himalayas, the Trans-Alaska pipeline and major roadways such as the Karakoram highway between China and Pakistan.

The fastest-growing lakes are in Scandinavia, Iceland and Russia, which all more than doubled in size, whereas the slower-growing ones are in Patagonia and Alaska. However, because many of the lakes in these regions are already vast, the increases are huge. In the north of Greenland, glacial lakes are growing rapidly and in south-west Greenland, some glacial lakes shrunk, but this was because they had already drained. 

Harrison says, “As lakes get bigger, there is more water in them to drain quickly and produce glacial lake outburst floods (GLOFs). Such events have killed tens of thousands of people over the past century and destroyed valuable infrastructure, such as hydroelectric power schemes. However, this is a complex issue. Some lakes become less vulnerable to GLOF triggers as they get bigger, but the more water that is available will tend to make the GLOF worse if one occurs.”

Scientists are working hard on ways to predict when GLOFs will occur but these events are rapid and unpredictable. There is often little to no warning when a glacial lake might burst because the natural dams that hold glacial lakes are unstable, so a small break can quickly become a gaping hole. 

In mid-May, a pocket of scorching hot air flowed north from Siberia and fanned out across the Arctic Ocean reaching as far as Greenland and triggering an unprecedented heatwave. In Khatanga, a Russian village above the Arctic Circle which normally remains below freezing in the spring, the mercury hit 25 degrees Celsius, smashing the previous record by 13 degrees C. According to temperature records which go back to 1958, no other year has been hotter in the Arctic for this same time period. This weather anomaly has since ignited significant wildfires in Russia and contributed to the rapid melt-out of sea ice in the Arctic Ocean — possibly jumpstarting this year’s melt season. Indeed, sea ice is currently at its fourth lowest for this time of year since record-keeping began in the 1970s. Could this increased Arctic ice melt actually be linked to the COVID-19 pandemic?

“Overall, this winter wasn’t particularly warm, but now that’s flipped around in the last month and we’re really seeing the effects,” says Mark Serreze, director of the National Snow and Ice Data Center (NSIDC). “Big holes are opening up along the Siberian coast where it’s been the warmest.”

This Central Arctic heatwave may not be a one-off event only occurring in spring 2020, researchers suggest. Rather, if levels of global industrial air pollutants continue to fall due to the COVID-19 pandemic, the current Arctic warmth could be a bellwether of what’s to come later this summer when sea ice melt annually kicks into high gear.

According to a recent study in Nature Climate Change, daily global greenhouse emissions dropped by 17 percent in early April compared to last year’s numbers. If maintained, a decline in carbon pollution is a good thing for global climate stability and for avoiding the most severe consequences of climate change.

But in the short-term, a drop-off in atmospheric pollutants can actually cause a slight increase in global warming. That’s because heat-trapping gases such as carbon dioxide and methane aren’t the only thing released by burning fossil fuels. Sulphate aerosols are also spewed into the air, and these aerosols are known to produce a cooling effect on the planet, mitigating some of the warming from greenhouse gases. If aerosol emissions are going down, it’s possible we could see a slight temperature bump upward this spring and summer which could speed up Arctic sea ice melt.

“Ultimately we need to eliminate sulfur pollution and sulphate aerosols, which cause lots of other problems too, such as acid rain,” says Michael Mann, a renowned climatologist and director of the Earth System Science Center at Pennsylvania State University. “But it is a ‘Faustian bargain’ in the sense that [reductions in aerosols] unmasks some of the global warming that had been hidden for decades by the sulphate aerosol pollution.”

You might also like: Antarctica’s Thwaites Glacier is Deteriorating at an Alarming Rate- What It Means

Sulphate Aerosols Reflect Solar Heat

Unlike greenhouse gases which can remain in our atmosphere for years, sulphate aerosols are relatively short-lived. They’re typically washed out of the troposphere in a matter of weeks, and therefore need to be constantly replenished by industry to maintain their cooling benefits.

Sulphate aerosols counteract planetary warming in two different ways. For one thing, they’re highly reflective. “They reflect a lot of sunlight back into space, rather than have it absorbed and warming the earth,” explains Michael Diamond, an atmospheric scientist at the University of Washington. “They can also change cloud properties. Clouds aren’t just pure water — they need a seed or a nuclei to form.” Sulphate aerosols provide such nuclei for water to condense around, creating a greater abundance of clouds, and more reflective clouds as well — an effect known as ‘cloud brightening.’

“It’s like a lot of little mirrors reflecting sunlight back to space,” says Diamond.

The United Nations Intergovernmental Panel on Climate Change has long struggled to quantify the exact cooling impact of sulphate aerosols. According to Mann, aerosols have likely been responsible for offsetting about 0.4 degrees Celsius of global surface warming, and a much larger amount — more than 1 degree C (1.8 degree F) — in the mid-latitude regions during summer when there is more sunlight to reflect back.

An AGU Advances study published in March 2020 sought to further quantify the aerosol impact on cloud brightening, with researchers zeroing in on a shipping lane in the southeast Atlantic. Diamond, who served as lead author of that study, found that sulphate aerosols from shipping were responsible for reducing warming by two watts per meter squared. To put that in perspective, greenhouse gases are responsible for warming of about 4 watts per meter squared. When Diamond and his team calculated the global cooling effect from all industrial activity around the world, on land and at sea, they found that sulphate aerosol-seeded clouds masked about a third of all warming from greenhouse gases.

covid-19 arctic ice melt
As sunlight intensifies in the Arctic during the spring and summer, clouds matter; the fewer the clouds, the more sunshine, and the more melt (Source: VisualHunt).

And Then Came COVID-19

Researchers around the world are now trying to parse out how Coronavirus lockdown measures have affected global emissions. In the Nature Climate Change study published last month, an international team of scientists found that daily CO2 emissions dropped by 17% at the peak of the coronavirus shutdown. However, emissions are creeping back up as shelter in place measures are relaxed. By year’s end it’s expected 2020 CO2 emissions will end up between 4 and 7% lower than 2019 — the biggest drop since World War II.

Another study published in Geophysical Research Letters in May found that nitrogen dioxide pollution over China, Western Europe, and the United States decreased by as much as 60% in early 2020 compared to the same time last year. And a study focused on northern China found that levels of Particulate Matter 2.5, a notable human health hazard, decreased by approximately 60% in January and February.

But Diamond says the picture is a bit more muddied when it comes to aerosols. His research group has been examining emission levels from China in February 2020. “In the clouds over the South China Plain and East China Sea, you don’t see any difference in the size of those cloud droplets,” he says, indicating there hasn’t been a significant change in the level of sulphate aerosols in the atmosphere. One explanation could be that though passenger traffic has fallen during the pandemic, electricity generation for industrial combustion is only down by about 10%, according to data from the Chinese government.

However, coincidentally, in January 2020, the United Nations International Maritime Organization implemented a policy banning ships from using fuels with a sulphur content above 0.5%, resulting in a seven-fold reduction from 3.5%. “Any signal we’re seeing in international shipping right now is a combination of this policy and the pandemic,” says Diamond.

Sulphate aerosols have been decreasing in the United States under the Clean Air Act as well, says Patricia Quinn, atmospheric chemistry leader at the U.S. National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Lab. Since the 1980s, sulphate aerosols have likely declined by between 30 and 50 percent. “It’s not serving as big as a mitigator [of warming] as it once was,” Quinn said. “Coal-fired power plants — a major source — aren’t being used as much as they were a few years ago because it’s a more expensive form of energy production now.”

Indeed, in a 2017 study, scientists posited that the sulphate aerosols released due to human activity masked the decline in Arctic sea ice in the mid-20th century, before the Clean Air Act went into effect, and actually led to periods of ice growth.

A Riddle, Wrapped in a Mystery, Inside an Enigma

So how might a reduction in sulphate aerosol levels affect the Arctic during the Coronavirus pandemic?

Quite a lot — maybe. Juan Acosta Navarro is an environmental scientist at the Barcelona Supercomputing Center. He says that, “The Arctic appears to be quite sensitive to changes in emissions of sulphate aerosols.” Using earth system computer modelling, his simulations showed that sulphate aerosol reductions in Europe since 1980 could potentially explain a significant fraction of Arctic warming over that period. Specifically, the Arctic received approximately 0.3 watts per meter squared of energy, warming by 0.5 degrees C (0.9 degrees F) on average as Europe’s sulphur emissions declined. “We conclude that air quality regulations in the Northern Hemisphere, the ocean and atmospheric circulation, and the Arctic climate are inherently linked,” his 2016 Nature Geoscience study stated.

But weather variability and climate system chaos — as always — still provide an obstacle to making any long-term predictions about the sea ice outcome this year, or any year.

“Patterns of the atmospheric circulation are going to play a huge role in what summer looks like,” says NSIDC’s Serreze. “Could we be looking at a record high global temperature this year? Maybe. We’re kind of on track for that right now. What’s going to happen with the sea ice? We know it’s well below average right now, but [weather variability] can counter the effects of greenhouse gases” in the short term.

Still, he’s energized — certainly not by COVID-19, but by the prospect of being able to test the role of sulphate aerosols on global warming. “Here we are, in a serendipitous sense, presented with this incredible global experiment. We can perhaps see what the effects are [of sulphate aerosol reduction] and how this relates back to the sea ice.”

“Every cloud has a silver lining,” he concludes.

Featured image by: Polar Cruises

This article was originally published on Mongabay, written by Gloria Dickie , and is republished here as part of an editorial partnership with Earth.Org. 

 

As climate change ricochets around the world, with Arctic warming and ice melt possibly bringing more extreme weather to mid-latitudes and northern sea ice melt perhaps generating a shift in equatorial wind patterns, new research shows that changes in tropical weather patterns may not just be coming from the top-down, but also from the bottom-up, from the Antarctic.

A study published in Nature Geoscience this March finds that melting sea ice in Antarctica is influencing weather patterns as far away as the equatorial Pacific, warming ocean surface temperatures, delivering more rain, and potentially creating El Niño-like effects.

Though there’s a growing body of research supporting an Arctic sea ice connection to tropical weather, this is one of the first studies to look at the impact of less sea ice at the South Pole on equatorial region weather. Scientists now estimate that diminished sea ice in both the Arctic and Antarctic will contribute roughly one-fifth of all the warming projected to occur in the tropics by the end of the century, less than 80 years away.

You might also like: ‘Green Snow’ is Spreading Across Antarctica: What Does it Mean?

antarctica ice melt
Sea ice and icebergs off East Antarctica in 2011 (Source: NASA Earth Observatory).

The biggest declines in sea ice so far have been documented in the Arctic, where extent over the past decade has fallen spectacularly below the 1981-2010 average. On March 5, 2020, Arctic sea ice hit its greatest extent for the year at 15 million square kilometers (5.7 million square miles), an improvement over recent winters, but “no reason to take what we are seeing as evidence for a recovery,” according to Mark Serreze, director of the National Snow and Ice Data Center.

In contrast, up until 2016 Antarctic sea ice was holding strong. Then things changed. In 2017 and 2018, sea ice extent around the southern continent plummeted, hitting record lows at the annual minimum. This year, Antarctica hit its minimum ice extent on February 21, at 2.69 million square kilometers (1.04 million miles) — above the three preceding years, but still well below average, particularly in the Amundsen-Ross region.

“All the climate models project that by the end of the century there will be a significant amount of Antarctic sea ice loss,” says Mark England, a polar climate scientist at Scripps Institution of Oceanography at the University of California San Diego and lead author of the Nature study. Indeed, some estimates indicate that Antarctica will lose half of its surrounding sea ice by 2100. Because that ice is floating, it won’t add to sea level rise, but it could cause havoc with global weather.

Earlier this year, researchers found that accelerating sea ice melt in the Arctic could be linked to the intensification of Central Pacific trade winds, the emergence of El Niño events, and the weakening of the North Pacific-Aleutian Low Circulation — a semi-permanent low pressure system that drives post-tropical cyclones and generates strong storms.

“The story for how the Arctic might impact the tropics has been getting stronger over the past couple of years through climate modeling studies,” explains England. “But if we’re trying to understand the polar regions’ impacts on the tropics, just concentrating on the Arctic may only give you half the signal over the next 50 or 60 years.”

In the new study, England and his co-authors used computer simulations to determine how Antarctic sea ice loss will combine with Arctic sea ice loss to alter wind patterns in the Pacific Ocean, inhibiting the upward movement of deep, cold ocean water to the surface, particularly in the eastern equatorial Pacific.

Based on England’s modeling, it’s expected that ice loss at the poles will combine to warm the equatorial Pacific surface ocean by 0.5℃ (0.9℉) and increase rain by more than 0.3 millimeters (0.01 inches) of rain there per day, while rainfall will decrease 0.2 millimeters per day south of Hawaii. Warming in these equatorial surface waters is also what happens during an El Niño event, which can trigger heavy rains in North and South America, and bring intense drought to Australia and west Pacific nations.

Prior to this research, England says, “we were really in the dark about what Antarctic sea ice loss may do. It’s a completely different idea where you have the Southern Ocean rather than the mid-latitude continents right next to [the ice areas].” But as it turns out, the effects of ice loss at the poles were quite similar. “We found that the tropical impacts kind of reinforce each other and lead to this quite large signal.”

“This study adds compelling evidence for the substantial global impacts of losing the Earth’s [reflective] mirror — namely sea ice at both poles,” says Jennifer Francis, a senior scientist at the Woods Hole Research Center who previously published a study that drew connections between changes in the Arctic and mid-latitude extreme weather. “Not only will ice melt affect the high-latitudes… it’s becoming abundantly clear that ocean currents, winds, and precipitation patterns in the temperate and tropical regions, where billions of people live, will also be disrupted.”

Still, more research is needed, with the influence of both poles upon the temperate and equatorial zones remaining a controversial topic. Last month, for example, mathematicians at the University of Exeter said they determined that Arctic warming does not, in fact, lead to a “wavier” jet stream around the mid-latitudes, but that any link between the two regions is likely due to random fluctuations in the jet stream impacting the Arctic — and not the other way round as Francis and other researchers assert who remain skeptical of the Exeter conclusions.

In terms of Antarctica, England says more modelling should be undertaken. “We’ve kind of skimmed the surface on the mechanism, but there’s a lot more work to be done to understand exactly the role of different feedbacks in getting this tropical response.”

In case none of this Antarctic climate news leaves you feeling vulnerable, another newly released study regarding the South Pole and sea level rise just might. According to scientists, Antarctica’s Denman glacier has retreated three miles over the past 20 years into its deepest undersea valley, providing a potential pathway for the warming ocean to accelerate melt from below. If the glacier were to retreat across the entire undersea canyon — roughly 100 miles — it could lose 540 trillion tons of ice and raise global sea level by five feet.

Featured image by: Eli Duke

This article was originally published on Mongabay, written by Gloria Dickie, and is republished here as part of an editorial partnership with Earth.Org. 

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