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Satellites now get full-year view of Arctic sea-ice – BBC

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Satellites can now measure the thickness of sea-ice covering the Arctic Ocean all year round.

Traditionally, spacecraft have struggled to determine the full state of the floes in summer months because the presence of surface meltwater has befuddled their instruments.

But by using new “deep learning” techniques, scientists have pushed past this limitation to get reliable observations across all seasons.

The breakthrough has wide implications.

Apart from the obvious advantage to ships, which need to know those parts of the Arctic that will be safe to navigate, there are significant benefits to climate and weather forecasting.

At the moment, there is considerable variation in the projections for when the polar ocean might be totally free of ice in an ever warmer world.

Having an improved insight into the melting processes in those key months when floes are being reduced, in area and thickness, ought now to sharpen the output from computer models.

“Despite excellent efforts by many researchers, these climate models’ predictions of when we’ll see the first fully ice-free Arctic Ocean in summer – they vary by 30-plus years,” Dr Jack Landy, from UiT The Arctic University of Norway, told BBC News.

“We need to tighten those predictions so we’re a lot more confident about what’s going to happen and when – and how the climate feedbacks will accelerate as a consequence.”

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The extent of Arctic sea-ice cover has been in decline for the entire period that satellites have been monitoring it, which is more than 40 years – a reduction running at an average rate of 13% per decade.

But it’s only really since 2011 that spacecraft have been able to consistently measure its thickness – and thickness (or more properly, volume) is the true measure of the floes’ health.

That’s because the extent of sea-ice cover is heavily dependent on whether the winds have spread out the floes or pushed them together.

To measure thickness, scientists use satellite altimeters.

The European Space Agency’s (Esa) pioneering Cryosat-2 mission carries a radar to measure the difference in height between the top of the marine ice and the top of the water in the cracks, or leads, that separate the floes.

From this difference, scientists can then, with a relatively simple calculation, work out the thickness of the ice.

The approach works well in winter months, but in summer, when the snows on top of the ice, and the ice itself, start to melt, pooling water effectively dazzles the radar. Scientists can’t be sure if the echo signal that returns to Cryosat is coming from the open ocean or from the surface of a meltpond sitting on the ice.

May through to September – the key melt season – has been a blind period for the spacecraft.

To solve the problem, researchers used an artificial intelligence (AI) technique in which an algorithm was able to learn and identify reliable observations from a vast library of synthetic radar signals.

Ice ridge

Seymour Laxon

Prof Julienne Stroeve, from University College London (UCL), explained: “We simulated what would be the echo shapes that we would get for different ice surface types – whether they had meltponds; whether it was flooded ice; or ice of different roughnesses; or simply leads. We created this huge database of physically based estimates of what the radar return should look like, and then we matched those to the individual radar pulses from the instrument to find echoes that matched the best.”

Esa has kept in its data archives all the Cryosat May-to-September measurements, even though for the past decade they’ve been of next to no use. But now, thanks to this new approach, Dr Landy’s team has been able to go back through the records to recover full-year ice thickness measurements for the entire time the satellite has been operational.

Dr Rachel Tilling worked extensively with Cryosat data before transferring her studies to the US space agency’s recently launched Icesat-2 laser altimeter mission.

She applauded the innovation.

“Summer is when sea-ice extent in the Arctic is seeing its most rapid decline, and having this extra dimension will help us understand more about how the ice pack is changing,” the Nasa scientist told BBC News.

“Icesat-2 has its own unique difficulties in summer but we’re lucky that its photon-counting technology means we can still measure the height of sea-ice, water and melt ponds year-round.

“Having said that, Cryosat-2 will always be my first love so I’m really excited to see it being used in this novel way.”

Meltponds

AWI/S.Hendricks

A chief beneficiary of the new thickness measurements would be Inuit populations in the Arctic, said Dr Michel Tsamados, also from UCL.

“[They] have identified sea-ice roughness and slush (melted snow and ice) as a key impediment for safe travel on the ice with the changing climate already negatively affecting these characteristics and causing increased travel accidents and search-and-rescues,” he explained.

“Both are related to the thickness of the ice. Therefore, measuring throughout the full year the sea-ice thickness from space from Cryosat-2 but also Icesat-2 and other satellite sensors will eventually help provide better maps to the Inuit populations for safe travel over this rapidly changing terrain.”

Dr Landy and colleague have published their new Cryosat approach in the journal Nature.

Presentational grey line

How to measure sea-ice thickness

How Cryosat measures sea-ice volume - graphic

  • Cryosat’s radar has the resolution to see the Arctic’s “floes” and “leads”
  • Some 8/9ths of the ice tends to sit below the waterline – the draft
  • The radar senses the height of the freeboard – the ice above the waterline
  • Knowing this 1/9th figure allows Cryosat to work out sea-ice thickness
  • The thickness multiplied by the area of ice cover produces a volume
  • Icesat-2 does exactly the same as Cryosat but with a laser instrument
  • The biggest uncertainty for both is the covering of snow on the ice

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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