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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.

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.”

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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.

How to measure sea-ice thickness

  • 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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The body of a Ugandan Olympic athlete who was set on fire by her partner is received by family

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NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.

Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.

She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.

Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.

“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.

It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.

Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.

Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.

Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.

“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.

He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.

Kenya’s high rates of violence against women have prompted marches by ordinary citizens in towns and cities this year.

Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.

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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B.C. sets up a panel on bear deaths, will review conservation officer training

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VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.

Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”

Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.

“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.

B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.

Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.

Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.

Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.

“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”

Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”

“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.

Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.

“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.

This report by The Canadian Press was first published Sept. 9, 2024.

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