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Antarctica’s Ross Ice Shelf, World’s Largest, is Melting in a Way Not Seen Before

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Ross Ice Shelf iceberg

This giant iceberg, B-15A, broke off the Ross Ice Shelf in Antarctica. (Credt: Josh Landis/NSF)

(Inside Science) — Most of the worry over melting ice in Antarctica has focused on the rapidly melting western shore, where there is enough ice to raise worldwide sea levels by up to 4.3 feet. But new research suggests that the massive Ross Ice Shelf, which has long been considered stable, might be at risk as well — potentially leading to a slower sea level rise of up to 38 feet as glaciers that were once held back by the shelf slide more quickly into the ocean. The researchers suspect that other crucial ice shelves could also be at risk.

“My primary concerns would be that the potential for melting and collapse of the big ice shelves is not being taken seriously enough,” said Laurie Padman, a physical oceanographer based in Corvallis, Oregon who works at a Seattle-based nonprofit called Earth and Space Research. “They’re being treated as less important because they are not presently showing much signs of change. But on a 100-year timescale, they have the potential for large changes.”

Antarctica’s fragile support system

The Ross Ice Shelf is the largest ice shelf in the world. Located on the side of Antarctica closest to New Zealand, it spans an area about the size of Spain and has an average thickness of roughly 1,300 feet. It is one of many ice shelves that extend oceanward from the edge of Antarctica with about 90 percent of their bulk submerged.

Melting of these ice shelves has no direct effect on global sea levels, since the ice is already at equilibrium with the surrounding water. But the ice shelves greatly slow the flow of glaciers on the continent that would otherwise slide faster into the ocean, causing water levels to rise.

The idea that ice shelves hold back grounded ice isn’t just theoretical. In 2002, Antarctica’s Larsen B ice shelf broke apart in less than a month, and afterward some of the adjacent glaciers sped up by as much as eight times.

The shattering of Larsen B shocked scientists, since no one had previously realized that an ice shelf could disappear so quickly, said Anna Hogg, a glaciologist at the University of Leeds in England. It was triggered by pools of water that formed on the ice shelf’s surface. The water leaked into fissures and forced them open in a process known as hydrofracture.

Hydrofracture is one of two mechanisms thought to account for most of the ice loss in the Antarctic. The other mechanism happens when deep, warm ocean currents flow far under an ice shelf, eating away at the “grounding line” where it connects to the land.

That’s what’s happening to the smaller Amundsen Sea ice shelves on Antarctica’s western shore, said Padman. Satellite measurements over the past 26 years have shown these ice shelves sinking, indicating that some are thinning by up to 7 meters (about 23 feet) per year. As a result, the glaciers they support — which contain enough ice to raise global sea levels by over four feet — are flowing rapidly into the sea.

A new way to melt

Satellite measurements suggest that the Ross Ice Shelf has been stable for the past few decades, even growing thicker in certain regions. But for the past four years, Padman has co-led a multi-institution collaboration called ROSETTA-Ice to study the Ross Ice Shelf more closely. Last month at the American Geophysical Union meeting in Washington, he presented some of the first findings from several studies that are part of the project.

The ROSETTA-Ice researchers have built a computer model of the interconnected factors that control the Ross Ice Shelf, including seasonal conditions, ocean currents, and the structure of ice and bedrock on the adjacent continent. The model is based on data collected by the ROSETTA-Ice team using instruments mounted on aircraft and on undersea robots.

The findings suggest that a spot on the northwestern side of the ice shelf is melting in a way researchers have not seen before — neither hydrofracture nor deep currents at the grounding line. Instead, the Ross’s problem is seasonal masses of warm water near the ocean surface in front of the ice shelf.

In winter, a crust of sea ice — far thinner than the actual ice shelf — covers the ocean in front of the shelf. But in summer, that sea ice melts, and the dark water absorbs solar energy and warms the water beneath. This warm surface water then erodes the northwestern corner of the Ross Ice Shelf, eating away at ice under the lip and causing small icebergs to crumble from its edge.

“What [Padman’s] talk showed is that on the Ross Ice Shelf, there are some regions that are showing very high melt rates at the front, by the calving front of the ice shelf, as opposed to the grounding line where we might normally look,” said Hogg, who was not involved in the research.

What it means for sea level

The lost ice is currently being replaced by ice flowing down from the continent, so the shelf is not yet getting thinner. But it could easily start to thin as the climate continues to warm, and current projections don’t take the processes the ROSETTA-Ice team observed into account, said Padman.

Most of the grounded glacier ice that is being held back by the Ross Ice Shelf is unlikely to melt anytime soon, in part because it is also held in place by the shape of underlying mountains and valleys, said Padman. But the melting corner of the Ross happens to be located right in front of a particularly vulnerable swathe of ice on the continent.

“It just happens to be in the right area where if you did thin the ice shelf, then you would have an effect on the amount of grounded ice coming into the ocean,” said Padman.

Even in a worst-case scenario, melting in the Ross won’t cause a sudden jump in sea levels over the next few decades, said Padman. But over centuries or millenia, the changes could be massive. The researchers are working to estimate how fast they might occur.

It’s possible that other Antarctic ice shelves also have spots that are melting rapidly due to summer surface warming, said Padman. For example, no one has yet looked for such a process on the Filchner-Ronne Ice Shelf, a huge ice shelf currently holding back glaciers that could raise sea levels by about 45 feet if they melted completely.

“We’re seeing a new process that we didn’t really think was an issue before,” said Hogg. “There is no reason why the stuff that they’re seeing on the Ross Ice Shelf wouldn’t be applicable elsewhere.”

[This story was originally published on Inside Science]

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Ecology

Globe Climate: Canada’s resource reckoning is coming

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Good afternoon, and welcome to Globe Climate, a newsletter about climate change, environment and resources in Canada.

This afternoon, the Alberta government announced that it is restoring a coal mining policy it revoked last spring. At the time, the move provoked a widespread public backlash detailed by The Globe. The original decision, which opened up more than 1.4 million hectares to exploration, was made without public consultation. Premier Jason Kenney previously defended the changes.

Lots more on coal and Canada’s resources industry in this week’s newsletter edition.

Now, let’s catch you up on other news.

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Ecology

‘Incredibly destructive’: Canada’s Prairies to see devastating impact of climate change

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As the climate continues to warm at an alarming rate, experts warn if dramatic steps to mitigate global warming are not taken, the effects in Canada’s Prairie region will be devastating to the country’s agriculture sector.

According to Environment and Climate Change Canada, the country is warming, on average, about double the global rate.

Scientists with the National Oceanic and Atmospheric Administration in the U.S. recently found 2020 was earth’s second-hottest year on record, with the average land and ocean surface temperature across the globe at 0.98 of a degree C above the 20th-century average.

However, the agency found the northern hemisphere saw its hottest year on record, at 1.28 degrees C above the average.

“(In Canada) we are looking at about 6.4C degrees of warming this century, which isn’t much less than one degree per decade, which is just a terrifying rate of warming,” Darrin Qualman, the director of climate crisis policy and action at the National Farmer’s Union said.

Qualman said there is “massive change coming” to Canada’s Prairies, which will be “incredibly destructive.”

“It’s not going too far to say that if we made that happen, parts of the Prairies wouldn’t be farmable anymore,” he said.

According to the federal government, in 2018 Canada’s agriculture and agri-food system generated $143 billion, accounting for 7.4 per cent of the country’s GDP.

The sector employed 2.3 million people in 2018. The majority of the 64.2 million hectares of farmland in Canada is concentrated in the Prairies and in southern Ontario.

The effects of climate change are already being felt on the ground in the Prairies, Qualman said, adding that the NFU has already heard from farmers complaining of “challenging weather.”

“People are sharing pictures of flattened crops and buildings, et cetera, that have been damaged,” he said. “And we’re still at the beginning of this.”

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Ecology

Insect-based dog food aims to cut your pet’s carbon pawprint

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Meat has an enormous carbon footprint, with livestock liable for about 15 per cent of worldwide emissions, as we have beforehand mentioned on this e-newsletter. That is prompted specialists to suggest consuming much less meat for sustainability (and well being) causes.

However what about your pet? One research discovered that the methane and nitrous oxide emissions generated by canine and cat meals within the U.S. alone had been equal to about 64 million tonnes of CO2, or roughly the quantity produced by 13.6 million automobiles. And it might be getting worse, with a development towards feeding pets “human-grade” meat.

That is prompted some pet meals makers to look to lower-carbon protein sources — together with bugs.

Research present that producing insect-based meals requires far much less feed, land and water and generates far fewer greenhouse fuel emissions per kilogram than meats comparable to beef, pork or rooster.

That is one of many causes increasingly more pet meals containing insect protein are hitting the market. Purina, a model owned by multinational Nestlé, launched a line of canine and cat meals containing black soldier fly larvae in Switzerland in November.

In Canada, Montreal-based Wilder Harrier began promoting canine treats made with cricket protein in 2015 and pet food made with black soldier fly larvae in 2019. It plans to broaden to launch a line of insect-based cat treats later this yr and cat meals in 2022 due to “a ton of demand,” mentioned firm co-founder Philippe Poirier.

Wilder Harrier initially labored with animal nutritionists on insect-based merchandise to unravel a unique downside — specifically, the founders’ canines had allergy symptoms to frequent meats utilized in canine meals. Poirier mentioned now about half its prospects hunt down the product due to their pets’ allergy symptoms and about half for environmental causes.

Dr. Cailin Heinze, a U.S.-based veterinary nutritionist licensed by the American School of Veterinary Vitamin, has written concerning the environmental influence of pet meals. She mentioned we’re typically “not as involved as we probably ought to [be]” concerning the environmental footprint of pets.

Alternatively, she famous that the longer-term influence of newer diets, comparable to vegan meals and people containing bugs, hasn’t been nicely examined in comparison with conventional pet meals.

Maria Cattai de Godoy, an assistant professor of animal sciences on the College of Illinois who research novel proteins for pet meals (together with bugs, yeast and plant-based substances), mentioned such substances are rigorously examined to find out their security and diet earlier than being added to pet meals. 

“This can be a very extremely regulated trade,” she mentioned, however admitted it is also evolving.

Relating to bugs, she mentioned constructive information “reveals promise in direction of utilizing them increasingly more in pet meals.” Insect-based proteins have additionally earned the endorsement of the British Veterinary Affiliation, which says some insect-based meals could also be higher for pets than prime steak.

However Godoy famous that there isn’t any one-size-fits-all resolution, and pet homeowners ought to take into consideration the wants of their very own particular person pet and analysis whether or not a specific weight loss plan can be appropriate.

She mentioned that other than the kind of protein, issues like packaging and manufacturing strategies may also make a distinction. For instance, utilizing meat byproducts that may in any other case turn into waste would not drive elevated meat manufacturing the identical approach as utilizing human-grade meat.

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