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3 trillion tons of Antarctic ice lost since 1992, seas rising, study suggests

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A comprehensive study suggests the Antarctic ice sheet lost roughly three trillion tons of ice between 1992 and 2017.

The study, published today in Nature, found that annual ice loss in West Antarctica — the most vulnerable to warming temperatures — was almost three times higher than earlier estimates, from 59 billion tons a year to 159 billion tons a year.

"This is a big increase in ice loss that needs to be understood and needs to be taken into consideration when we look to the future," Andrew Shepherd, lead author and a professor of Earth Observation University of Leeds in the United Kingdom said.

The Antarctic ice sheet covers about 24 million square kilometres and holds about 60 per cent of all freshwater on Earth. If it were to melt completely, it would raise sea levels by 58 metres. 

The team issued a video illustrating their findings.

In the big picture, the new findings suggest this: instead of the Antarctic ice sheet contributing 0.2 mm of water to rising sea levels, it is now three times that at 0.6 mm annually. Antarctica is now responsible for roughly 30 per cent of global sea rise rather than the 10 per cent once believed.

Though Shepherd said they can't point to one root cause that is responsible for the melt, it is in response to a changing climate.

"Antarctica has very clearly become activated over the past couple of decades in a way that it wasn't before," Shepherd said.

The study used 20 years of data from 24 independent satellite measurements, along with studies from more than 80 co-authors, and was prepared in collaboration with NASA and ESA.

"We think this is the most authoritative estimate to date, and it shows a really clear picture," Shepherd said.

Truth and consequences

The findings have far-reaching implications.

Rising sea levels not only pose a threat to low-lying islands in the Pacific, as we've seen by nations such as in the island nation of Kiribati, but contrary to common perception, it's the north that will feel the pinch with continuing Antarctic ice sheet melt.

Unusual iceberg at Rothera Research Station, Antarctic Peninsula. (Andrew Shepherd, University of Leeds )

Co-author W. Richard Peltier, professor of physics at the University of Toronto, explained that current theory suggests that on long time scales, the ocean surface must stay at a particular state of gravitational consistency. Adding mass throws that off. So ocean currents move in a way that redistributes additional mass. If the water begins to rise in the southern hemisphere unbalancing that consistency, currents redistribute to move the water somewhere else — that is, north.

It's a really important problem in climate science: separating out the long-term climate signal from the short-term weather fluctuations.– Andrew Shepherd, lead author

And that means something for Canada. With significant sea level rise, cities along the coasts, such as Halifax, Charlottetown and Vancouver, will likely be affected.

"The greatest threat from West Antarctic collapse would be northern hemisphere sites in general," Peltier said.

Sea ice versus ice sheets

These new findings may contradict what people have been reading in the news about increases in ice in Antarctica.

But that's because those reports are about sea ice, not ice sheets.

"There's a big difference between seasonal changes in sea ice and the longer term trends that we see in other parts of the cryosphere, like the ice sheets," Shepherd said.

Sea ice can be influenced by warm days, strong winds and ocean currents that can cause sea ice to wax or wane seasonally.

The same is not true of ice sheets, created by thousands of years of snowfall. 

"It's a really important problem in climate science: separating out the long-term climate signal from the short-term weather fluctuations."

Sea level contribution due to the Antarctic ice sheet between 1992 and 2017. ( imbie/Planetary Visions)

"The changes that we see there are even harder to perceive, because you can't see them with your eyes," Shepherd said of the ice sheet melt.

"If you look at the continent from space with a bird's-eye view, it would look the same today as it did 30 years ago. It's just lost a lot more ice because it's thinned and it's speeded up."

While measurements in the range of millimetres may not sound like anything significant, both Shepherd and Peltier note that what it means for the future.

"We've all been caught by surprise by the pace of which Antarctic ice loss has increased," Shepherd said. "It's not a small number … 0.6 millimetre sea level rise doesn't sound like a large number to the public. But it means a lot to the potential of future sea level rise."

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Thick Dust Clouds Spotted Near Martian Ice Cap

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ESA’s Mars Express took an incredible photo of dust clouds on Mars near the planet’s north polar ice cap in April 2018, shortly before a larger dust storm darkened the entire planet’s skies.

Credit: ESA/DLR/FU Berlin/CC BY-SA 3.0 IGO

A thick cloud of dust moves over the surface of Mars near the planet's north polar ice cap in a stunning photograph.

This June, a massive dust storm hit Mars, and before long, the storm had encapsulated the entire planet. But dust clouds are a common occurrence on Mars; before that storm, a smaller-scale tempest kicked up the impressive plumes in this new photo, taken in April by the European Space Agency's (ESA) Mars Express. The photoshows just how immense these clouds can get, with a thick dust cloud near the planet's north polar ice cap.

Dust storms happen on Mars most often during the southern summer season. At this time, the planet is closer to the sun along the elliptical Martian orbit, and the brightness increases the differences in temperature on Mars, which affect air movement on the planet. These temperature differences allow the Martian air to more easily lift dust particles on the surface, according to a statement from ESA.

However, while a planet-covering dust storm sounds terrifying, things aren't that chaotic on the surface. This is because storm wind speeds on Mars are usually less than half as fast as hurricane wind speeds on Earth. Additionally, because atmospheric pressure is so low on the Red Planet, even high-speed winds wouldn't do much damage to anyone on the planet. "You would probably feel a breeze, but it wouldn't be knocking you over," Michael Smith, who works at the NASA Goddard Space Flight Center, previously said to Space.com.

Mars Express captured this cloud using a high-resolution stereo camera on board. The dust storm that continues to rage on Mars is being imaged and monitored by five ESA and NASA orbiters, while NASA's Curiosity rover continues to collect data on the red, dusty surface.

Email Chelsea Gohd at cgohd@space.com or follow her @chelsea_gohd. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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Unique Armored Dinosaur Discovered In Utah

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The fossil reveals new details about the diversity and evolution of ankylosaurid dinosaurs

In 2008, researchers found the fossil of a remarkable armored dinosaur in southern Utah. The North American Late Cretaceous ankylosaurid dinosaur was covered in a smooth bony armor but it seems to be more closely related to ankylosaurids found in Asia than to ones that lived in northern America.

The new species of ankylosaurid dinosaur lived 76 million years ago during the Late Cretaceous Period and roamed the lost continent of Laramidia. Although many ankylosaurids dinosaur fossils have been found over the years in the southwestern US, the recent fossil offers the most complete skeleton of an ankylosaurid in the region. The fossil includes a complete skull, vertebrae and limb bones, as well as a perfectly preserved bony body armor.

The most interesting thing about this dinosaur is its spiky bony armor covering the skull and snout. These defining features make it look surprisingly similar to Asian ankylosaurids that originated in Asia between 125 to 100 million years ago.

“A reasonable hypothesis would be that ankylosaurids from Utah are related to those found elsewhere in western North America, so we were really surprised to discover that Akainacephalus was so closely related to species from Asia.” Co-author of the study Randall Irmis said in a statement.

A new analysis indicates that the diversity and evolution of armored dinosaurs in the region was the result of brief intervals of lowered sea level that allowed Asian ankylosaurid dinosaurs to immigrate to North America several times during the Late Cretaceous. Lower sea levels exposed the Beringian land bridge and allowed dinosaurs and other animals to move between Asia and North America, which led to the presence of two separate groups of ankylosaurid dinosaurs.

“It is extremely fascinating and important for the science of paleontology that we can read so much information from the fossil record, allowing us to better understand extinct organisms and the ecosystems they were a part of,” said lead author Jelle Wiersma.

“…Akainacephalus johnsoni; not only is this the first described and named Late Cretaceous ankylosaurid dinosaur from Utah, but this unique animal also strengthens the idea the evidence that distinct northern and southern provincialism existed during the late Campanian stage in Laramidia, because to date, we don’t see this type of ankylosaurid dinosaurs in the fossil record of northern Laramidia.”

Akainacephalus johnsoni has been assigned to a new genus. The genus name comes from the Greek words akaina, which means ‘thorn’ or ‘spike’, and cephalus, meaning ‘head.’ The other part of the name honors Randy Johnson, a dedicated museum volunteer who skillfully reconstructed its skull.

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This Massive Dust Storm Could Engulf Mars for Months

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Every six to eight years, massive dust storms can envelop Mars’s whole surface. NASA’s Martian probes are currently watching one unfold over the Red Planet. Scientists saw a small-scale dust storm begin on May 30th, and by June 20th, it’d gone “global,” engulfing the whole planet. For the NASA Opportunity rover, visibility dropped from that of a sunny day to an overcast one. Because the rover runs on solar energy, researchers suspended it to preserve its batteries. According to NASA, it could take as long as September before the dust starts to settle, and the Opportunity starts reporting back.

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Meanwhile, numerous other Mars orbiters are helping scientists understand the dust storm. “This is one of the largest weather events that we’ve seen on Mars,” since spacecraft observations began in the 1960s, said Michael Smith, a scientist at NASA’s Goddard Spaceflight Center. Smith and other scientists are trying to understand how small, regional storms swarm to become such a large one. They’re also recording how the dust storm changes the planet’s atmospheric temperatures, which can change winds, which in turn can amplify the storm by stirring up more dust from the planet’s surface. “The very fact that you can start with something that’s a local storm, no bigger than a small [US] state, and then trigger something that raises more dust and produces a haze that covers almost the entire planet is remarkable,” said Rich Zurek, the project scientist for MRO, which maps the evolution of the storm daily in color images and atmospheric temperature.

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Meanwhile, the Mars Curiosity is on a mission to acquire rock samples and study the storm from the surface of Mars itself, and another orbiter is studying Mars’ high atmosphere, 100 kilometers above the surface, where the dust doesn’t reach. Every time you see Mars in the sky in the weeks ahead, NASA advises, “remember how much data scientists are gathering to better understand the mysterious weather of the Red Planet.”

(via NASA)

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