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Ozone-depleting gases might have driven extreme Arctic warming – Nature.com

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Drift ice/ice floes in the Arctic Ocean.

Climate change in the Arctic is shrinking the region’s cap of sea ice.Credit: Arterra/Universal Images Group/Getty

Gases that deplete the ozone layer could be responsible for up to half of the effects of climate change observed in the Arctic from 1955 to 2005.

The finding could help to explain the disproportionate toll of climate change on the region, which has long puzzled scientists. The Arctic is warming at more than twice the average rate of the rest of the globe — a phenomenon known as Arctic amplification — and it is losing sea ice at a staggering pace.

Ozone-depleting substances, including chlorofluorocarbons (CFCs), are known to warm the atmosphere thousands of times more efficiently than carbon dioxide. But most of the research on these chemicals has focused on their effects on the planet’s protective ozone layer — especially over the Southern Hemisphere, where they are responsible for the formation of the Antarctic ozone hole, says Mark England, a climate scientist at Scripps Institution of Oceanography in La Jolla, California. He co-authored the study, published on 20 January in Nature Climate Change1, which he says is “really reframing a lot of the discussion on a more global basis”.

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England and his colleagues compared climate simulations both with and without the mass emission of CFCs that began in the 1950s. Without CFCs, the simulations showed an average Arctic warming of 0.82 °C. When the presence of ozone-depleting compounds was factored in, that number jumped to 1.59 °C. The researchers saw similarly dramatic changes in sea-ice coverage between the two sets of model simulations. By running the models with fixed CFC concentrations while varying the thickness of the ozone layer, the team was able to attribute the warming directly to the chemicals — rather than changes these substances caused in the ozone layer.

England’s team has “done a careful study in a single model”, says Marika Holland, a climate scientist at the National Center for Atmospheric Research in Boulder, Colorado. “I think that it makes a lot of sense.” She says that the warming effect of ozone-depleting substances in the atmosphere is a well-documented phenomenon. However, she notes, the complexities of climate models make it hard to say for certain what the exact magnitude of the effect on the Arctic is.

Susan Strahan, an atmospheric scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, says that the work is “interesting and provocative”, but she is not yet convinced of its conclusions. A stronger argument could be made, she continues, if the team had been able to provide a clear physical explanation for the modelled amplification.

Both Strahan and Cecilia Bitz, a climate scientist at the University of Washington in Seattle, say that replicating these results in multiple climate models will be crucial for improving estimates of just how much responsibility CFCs bear for heating the Arctic.

Global CFC concentrations have been on the decline since the turn of the millennium, following the 1989 adoption of the Montreal Protocol, which called for a phase-out of the substances. Although many other factors contribute to Arctic amplification, the result suggests that Arctic warming and sea-ice melt might be tempered in the future as ozone-depleting substances continue to leave the atmosphere, Bitz says. “It’s a very important paper because it has a little shred of optimism.”

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Giant prehistoric salmon had tusk-like teeth for defence, building nests

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The artwork and publicity materials showcasing a giant salmon that lived five million years ago were ready to go to promote a new exhibit, when the discovery of two fossilized skulls immediately changed what researchers knew about the fish.

Initial fossil discoveries of the 2.7-metre-long salmon in Oregon in the 1970s were incomplete and had led researchers to mistakenly suggest the fish had fang-like teeth.

It was dubbed the “sabre-toothed salmon” and became a kind of mascot for the Museum of Natural and Cultural History at the University of Oregon, says researcher Edward Davis.

But then came discovery of two skulls in 2014.

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Davis, a member of the team that found the skulls, says it wasn’t until they got back to the lab that he realized the significance of the discovery that has led to the renaming of the fish in a new, peer-reviewed study.

“There were these two skulls staring at me with sideways teeth,” says Davis, an associate professor in the department of earth sciences at the university.

In that position, the tusk-like teeth could not have been used for biting, he says.

“That was definitely a surprising moment,” says Davis, who serves as director of the Condon Fossil Collection at the university’s Museum of Natural and Cultural History.

“I realized that all of the artwork and all of the publicity materials and bumper stickers and buttons and T-shirts we had just made two months prior, for the new exhibit, were all out of date,” he says with a laugh.

Davis is co-author of the new study in the journal PLOS One, which renames the giant fish the “spike-toothed salmon.”

It says the salmon used the tusk-like spikes for building nests to spawn, and as defence mechanisms against predators and other salmon.

The salmon lived about five million years ago at a time when Earth was transitioning from warmer to relatively cooler conditions, Davis says.

It’s hard to know exactly why the relatives of today’s sockeye went extinct, but Davis says the cooler conditions would have affected the productivity of the Pacific Ocean and the amount of rain feeding rivers that served as their spawning areas.

Another co-author, Brian Sidlauskas, says a fish the size of the spike-toothed salmon must have been targeted by predators such as killer whales or sharks.

“I like to think … it’s almost like a sledgehammer, these salmon swinging their head back and forth in order to fend off things that might want to feast on them,” he says.

Sidlauskas says analysis by the lead author of the paper, Kerin Claeson, found both male and female salmon had the “multi-functional” spike-tooth feature.

“That’s part of our reason for hypothesizing that this tooth is multi-functional … It could easily be for digging out nests,” he says.

“Think about how big the (nest) would have to be for an animal of this size, and then carving it out in what’s probably pretty shallow water; and so having an extra digging tool attached to your head could be really useful.”

Sidlauskas says the giant salmon help researchers understand the boundaries of what’s possible with the evolution of salmon, but they also capture the human imagination and a sense of wonder about what’s possible on Earth.

“I think it helps us value a little more what we do still have, or I hope that it does. That animal is no longer with us, but it is a product of the same biosphere that sustains us.”

This report by The Canadian Press was first published April 24, 2024.

Brenna Owen, The Canadian Press

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Giant prehistoric salmon had tusk-like spikes used for defence, building nests: study

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A new paper says a giant salmon that lived five million years ago in the coastal waters of the Pacific Northwest used tusk-like spikes as defense mechanisms and for building nests to spawn.

The initial fossil discoveries of the 2.7-metre-long salmon in Oregon in the 1970s were incomplete and led researchers to suggest the fish had fang-like teeth.

The now-extinct fish was dubbed the “saber-tooth salmon,” but the study published in the peer-reviewed journal PLOS One today renames it the “spike-toothed salmon” and says both males and females possessed the “multifunctional” feature.

Study co-author Edward Davis says the revelation about the tusk-like teeth came after the discovery of fossilized skulls at a site in Oregon in 2014.

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Davis, an associate professor in the department of earth sciences at the University of Oregon, says he was surprised to see the skulls had “sideways teeth.”

Contrary to the belief since the 1970s, he says the teeth couldn’t have been used for any kind of biting.

“That was definitely a surprising moment,” Davis says of the fossil discovery in 2014. “I realized that all of the artwork and all of the publicity materials … we had just made two months prior, for the new exhibit, were all out of date.”

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SpaceX sends 23 Starlink satellites into low-Earth orbit

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April 23 (UPI) — SpaceX launched 23 Starlink satellites into low-Earth orbit Tuesday evening from Space Launch Complex 40 at Cape Canaveral Space Force Station in Florida.

Liftoff occurred at 6:17 EDT with a SpaceX Falcon 9 rocket sending the payload of 23 Starlink satellites into orbit.

The Falcon 9 rocket’s first-stage booster landed on an autonomous drone ship in the Atlantic Ocean after separating from the rocket’s second stage and its payload.

The entire mission was scheduled to take about an hour and 5 minutes to complete from launch to satellite deployment.

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The mission was the ninth flight for the first-stage booster that previously completed five Starlink satellite-deployment missions and three other missions.

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