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Greenland Ice Sheet Melting Faster Than at Any Time in Last 12,000 Years, Study Finds

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Greenland Ice Sheet Melting Faster Than at Any Time in Last 12,000 Years, Study Finds
Icebergs float at the mouth of the Ilulissat Icefjord during a week of unseasonably warm weather on Aug. 4, 2019 near Ilulissat, Greenland. Sean Gallup /Getty Images

Rising temperatures in the air and the water surrounding Greenland are melting its massive ice sheet at a faster rate than anytime in the last 12 millennia, according to a new study published Wednesday in the journal Nature.


The study, Rate of mass loss from the Greenland Ice Sheet will exceed Holocene values this century, found that while Greenland is losing ice rapidly now, the worst is yet to come. At its current trajectory, the Greenland ice sheet will lose its ice mass roughly four times faster than at anytime in the last 11,700 years. The researchers say the massive dump of freshwater into the ocean will disrupt the ocean's currents and raise sea levels, as The Washington Post reported.

Advanced prediction models had led scientists to conclude that Greenland's melting ice, which is currently the largest contributor to sea level rise, is raising sea levels by 0.7 millimeters each year. And, by the end of the century, that number could increase anywhere from four to ten times its current contribution.

This new paper found that prediction to be a severe underestimation. It revised that prediction and accounted for a wide range of greenhouse gas emissions to conclude that Greenland's contribution to sea level rise will actually be much worse. By the end of the century, it will lift sea levels between 2 to 10 centimeters every year, according to a commentary in Nature.

The Washington Post noted that while Greenland is the largest contributor to rising sea levels, the melting ice sheets in Antarctica may raise sea levels even more.

"We have altered our planet so much that the rates of ice sheet melt this century are on pace to be greater than anything we have seen under natural variability of the ice sheet over the past 12,000 years," said Jason Briner, a geologist at the University of Buffalo and lead author of the paper, as The Guardian reported.

Briner pointed out that the current ice melt is not due to the natural variability, which is why it is so different from historical patterns. This melting is strictly man-made, which is unprecedented in the history of the world, as CNN reported.

The commentary in Nature, written by Andy Aschwanden from the Geophysical Institute at the University of Alaska Fairbanks, noted that there is really only one way available to us to stop the acceleration of sea ice loss from Greenland.

"Thanks to the work of Briner and colleagues, we are now one step closer to the goal of accurately and confidently predicting mass loss from the Greenland ice sheet," Aschwanden concluded. "However, we are also increasingly certain that we are about to experience unprecedented rates of ice loss from Greenland, unless greenhouse-gas emissions are substantially reduced."

To conduct the research, the scientists used a combination of on-the-ground observations in southwest Greenland and advanced computer modeling. The geologists looked at the composition of Greenland's boulders to determine when ice was there and when it melted away. That analysis allowed them to put together an uninterrupted history of Greenland's ice sheet and a predictive model for the next century, as The Washington Post reported.

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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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