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Record Ozone Hole Forms Over Arctic

Science

A record-sized hole has opened in the ozone layer over the Arctic, The Guardian reported Tuesday.


While both poles lose some ozone during their winters, the Arctic tends to lose much less than Antarctica, where the larger and more famous ozone hole is located, the European Space Agency (ESA) explained. This year's anomaly is the result of a combination of unusually low Arctic temperatures, sunlight, wind fields and human emissions of ozone-depleting substances like chlorofluorocarbons (CFC).

This doesn't mean ozone-depleting emissions are increasing, director of the Copernicus Atmosphere Monitoring Service Vincent-Henri Peuch told The Guardian.

"However, this is a reminder that one should not take the Montreal Protocol measures for granted, and that observations from the ground and from satellites are pivotal to avoid a situation where the chlorine and bromine levels in the stratosphere could increase again," he said.

The ozone layer is a layer of protective gas in the stratosphere that shields Earth from the sun's ultraviolet light, which can cause skin cancer and cataracts, ESA explained.

In Antarctica, a hole in this protective coating is ripped every winter when cold temperatures cause high clouds to form over the pole, as Nature reported. These clouds react with human emissions of chemicals like chlorine and bromine, which then deplete the ozone layer.

Usually, the North Pole doesn't get consistently cold enough for these reactions to occur. But this year, a "polar vortex" trapped so much cold air above the Arctic that there was more than at any time since 1979.

"The hole is principally a geophysical curiosity," Peuch told The Guardian. "We monitored unusual dynamic conditions, which drive the process of chemical depletion of ozone. [Those dynamics] allowed for lower temperatures and a more stable vortex than usual over the Arctic, which then triggered the formation of polar stratospheric clouds and the catalytic destruction of ozone."

The unusual hole is still smaller than its Antarctic counterpart.

"The ozone hole we observe over the Arctic this year has a maximum extension of less than 1 million sq km. This is small compared to the Antarctic hole, which can reach a size of around 20 to 25 million sq km with a normal duration of around 3 to 4 months," Diego Loyola from the German Aerospace Center told ESA.

It also is not expected to last as long. It formed around March 14 and is projected to disappear by mid April.

It is also unlikely to impact people, though there is a small chance it could move further south over southern Greenland, which would increase sunburn risk for people who live there, according to The Guardian.

But both ozone holes are ultimately on the mend, thanks to the 1987 Montreal Protocol that set limits on ozone-depleting chemicals. The Antarctic hole was the smallest in 35 years last November.

Overall, the ozone layer has been recovering at a rate of one to three percent per decade since 2000, according to the 2018 Scientific Assessment of Ozone Depletion, as ESA reported.

"At these projected rates, the Northern Hemisphere and mid-latitude ozone is predicted to recover by around 2030, followed by the Southern Hemisphere around 2050, and polar regions by 2060," ESA wrote.

A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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