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Fewer trees, less undergrowth: Study says wildfires changing boreal forest – The Outlook

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4 years ago

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EDMONTON — The increasing frequency of wildfires in Canada’s boreal forest may be permanently changing one of the largest intact ecosystems left on Earth, research suggests.

“We feel pretty confident these effects will persist,” said Ellen Whitman, a forest ecologist at Natural Resources Canada and the University of Alberta.

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Whitman is a co-author on a recently published paper examining what happens when stands of boreal forest — the huge belt of green that stretches over the northern reaches of most Canadian provinces — are burned over more often as a result of climate change.

She and her colleagues paired up forest areas that had similar climate and soil conditions and had last been burned by the same fire. One half had been previously burned no more than 17 years before, while the other half’s last fire had been at least 30 years ago.

The differences were striking.

The short-interval stands were far more open with fewer trees. Aspens dominated instead of conifers. Growth beneath the trees — shrubs and grasses that cover a normal forest floor — was far less luxuriant with many fewer species. Areas of exposed mineral soil, where all organic material had been burned off, were larger and more common.

They felt completely different.

“You have a landscape where you’re surrounded by short, stunted trees,” Whitman said. “You have a crust of lichen or some sparse grasses. It’s almost like walking through the edge of a prairie where you’re shifting from a grassland into a forest edge.

“At a lot of the long-interval sites, you’ve got quite dense conifers, closer together. You’ve got moss on the ground and flowers and shrubs. It’s more what looks like a young forest.”

The boreal forest has evolved for fire. Many of its tree species need it to germinate.

Normally, fires don’t come around more often than every 30 years and often much longer. The lack of fuel in recently burned stands helps regulate that frequency.

Climate change is breaking those rules, Whitman said.

“We’re experiencing more hot, dry windy days — the main trigger for large fire years. As more years experience more extreme fire weather, (the blazes) are able to overwhelm that resistance that recently burned sites have.”

Nor are the parkland-like areas likely to evolve into a conventional boreal forest. Previous studies have found that the look of a forest is set early after a fire.

“Immediate post-fire condition is an extremely strong predictor of what the stand will look like further down the road,” said Whitman.

Whitman emphasizes that short-interval stands in her research are still small and most stretches of boreal forest burned in recent wildfires are regrowing normally. Wetlands are also less affected by short-interval fires than drier regions.

She said the forestry industry is unlikely to be affected any time soon — although forest-dependent animals such as caribou and songbirds will feel impacts.

And those impacts are growing.

“With a longer fire season, larger fires, more of the landscape burning each year, the likelihood of encountering a recently burned area increases. We’re undergoing a shortening of the fire frequency in the boreal forest.”

This report by The Canadian Press was first published Jan. 12, 2010.

— Follow Bob Weber @row1960 on Twitter

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An extra moon may be orbiting Earth — and scientists think they know exactly where it came from – Livescience.com

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April 23, 2024

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A fast-spinning asteroid that orbits in time with Earth may be a wayward chunk of the moon. Now, scientists think they know exactly which lunar crater it came from.

A new study, published April 19 in the journal Nature Astronomy, finds that the near-Earth asteroid 469219 Kamo’oalewa may have been flung into space when a mile-wide (1.6 kilometers) space rock hit the moon, creating the Giordano Bruno crater.

Kamo’oalewa’s light reflectance matches that of weathered lunar rock, and its size, age and spin all match up with the 13.6-mile-wide (22 km) crater, which sits on the far side of the moon, the study researchers reported.

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China plans to launch a sample-return mission to the asteroid in 2025. Called Tianwen-2, the mission will return pieces of Kamo’oalewa about 2.5 years later, according to Live Science’s sister site Space.com.

“The possibility of a lunar-derived origin adds unexpected intrigue to the [Tianwen-2] mission and presents additional technical challenges for the sample return,” Bin Cheng, a planetary scientist at Tsinghua University and a co-author of the new study, told Science.

Related: How many moons does Earth have?

Kamo’oalewa was discovered in 2016 by researchers at Haleakala Observatory in Hawaii. It has a diameter of about 100 to 200 feet (approximately 30 to 60 meters, or about the size of a large Ferris wheel) and spins at a rapid clip of one rotation every 28 minutes. The asteroid orbits the sun in a similar path to Earth, sometimes approaching within 10 million miles (16 million km).

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Follow-up studies suggested that the light spectra reflected by Kamo’oalewa was very similar to the spectra reflected by samples brought back to Earth by lunar missions, as well as to meteorites known to come from the moon.

Cheng and his colleagues first calculated what size object and what speed of impact would be necessary to eject a fragment like Kamo’oalewa from the lunar surface, as well as what size crater would be left behind. They figured out that the asteroid could have resulted from a 45-degree impact at about 420,000 mph (18 kilometers per second) and would have left a 6-to-12-mile-wide (10 to 20 km) crater.

There are tens of thousands of craters that size on the moon, but most are ancient, the researchers wrote in their paper. Near-Earth asteroids usually last only about 10 million years, or at most up to 100 million years before they crash into the sun or a planet or get flung out of the solar system entirely. By looking at young craters, the team narrowed down the contenders to a few dozen options.

The researchers focused on Giordano Bruno, which matched the requirements for both size and age. They found that the impact that formed Giordano Bruno could have created as many as three still-extant Kamo’oalewa-like objects. This makes Giordano Bruno crater the most likely source of the asteroid, the researchers concluded.

“It’s like finding out which tree a fallen leaf on the ground came from in a vast forest,” Cheng wrote on X, formerly known as Twitter.

Confirmation will come after the Tianwen-2 mission brings a piece of Kamo’oalewa back to Earth. Scientists already have a sample of what is believed to be ejecta from Giordano Bruno crater in the Luna 24 sample, a bit of moon rock brought back to Earth in a 1976 NASA mission. By comparing the two, researchers could verify Kamo’oalewa’s origin.

Editor’s note: This article’s headline was updated on April 23 at 10 a.m. ET.

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"Hi, It's Me": NASA's Voyager 1 Phones Home From 15 Billion Miles Away – NDTV

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April 23, 2024

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Launched in 1977, Voyager 1 was mankind’s first spacecraft to enter the interstellar medium

Washington, United States:

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NASA’s Voyager 1 probe — the most distant man-made object in the universe — is returning usable information to ground control following months of spouting gibberish, the US space agency announced Monday.

The spaceship stopped sending readable data back to Earth on November 14, 2023, even though controllers could tell it was still receiving their commands.

In March, teams working at NASA’s Jet Propulsion Laboratory discovered that a single malfunctioning chip was to blame, and devised a clever coding fix that worked within the tight memory constraints of its 46-year-old computer system.

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“Voyager 1 spacecraft is returning usable data about the health and status of its onboard engineering systems,” the agency said.

“The next step is to enable the spacecraft to begin returning science data again.”

Launched in 1977, Voyager 1 was mankind’s first spacecraft to enter the interstellar medium, in 2012, and is currently more than 15 billion miles from Earth. Messages sent from Earth take about 22.5 hours to reach the spacecraft.

Its twin, Voyager 2, also left the solar system in 2018.

Both Voyager spacecraft carry “Golden Records” — 12-inch, gold-plated copper disks intended to convey the story of our world to extraterrestrials.

These include a map of our solar system, a piece of uranium that serves as a radioactive clock allowing recipients to date the spaceship’s launch, and symbolic instructions that convey how to play the record.

The contents of the record, selected for NASA by a committee chaired by legendary astronomer Carl Sagan, include encoded images of life on Earth, as well as music and sounds that can be played using an included stylus.

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Their power banks are expected to be depleted sometime after 2025. They will then continue to wander the Milky Way, potentially for eternity, in silence.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

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West Antarctica's ice sheet was smaller thousands of years ago – here's why this matters today – The Conversation

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April 23, 2024

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As the climate warms and Antarctica’s glaciers and ice sheets melt, the resulting rise in sea level has the potential to displace hundreds of millions of people around the world by the end of this century.

A key uncertainty in how much and how fast the seas will rise lies in whether currently “stable” parts of the West Antarctic Ice Sheet can become “unstable”.

One such region is West Antarctica’s Siple Coast, where rivers of ice flow off the continent and drain into the ocean.

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The Ross Ice Shelf holds back the flow of ice streams from West Antarctica’s Siple Coast.
Journal of Geophysical Research, CC BY-SA

This ice flow is slowed down by the Ross Ice Shelf, a floating mass of ice nearly the size of Spain, which holds back the land-based ice. Compared to other ice shelves in West Antarctica, the Ross Ice Shelf has little melting at its base because the ocean below it is very cold.

Although this region has been stable during the past few decades, recent research suggest this was not always the case. Radiocarbon dating of sediments from beneath the ice sheet tells us that it retreated hundreds of kilometres some 7,000 years ago, and then advanced again to its present position within the last 2,000 years.

Figuring out why this happened can help us better predict how the ice sheet will change in the future. In our new research, we test two main hypotheses.



Read more:
What an ocean hidden under Antarctic ice reveals about our planet’s future climate

Testing scenarios

Scientists have considered two possible explanations for this past ice sheet retreat and advance. The first is related to Earth’s crust below the ice sheet.

As an ice sheet shrinks, the change in ice mass causes the Earth’s crust to slowly uplift in response. At the same time, and counterintuitively, the sea level drops near the ice because of a weakening of the gravitational attraction between the ice sheet and the ocean water.

As the ice sheet thinned and retreated since the last ice age, crustal uplift and the fall in sea level in the region may have re-grounded floating ice, causing ice sheet advance.

A graphic showing how Earth's crust uplifts and sea level drops near the ice sheet as it loses mass.
Earth’s crust uplifts and sea level drops near the ice sheet as it loses mass.
AGU, CC BY-SA

The other hypothesis is that the ice sheet behaviour may be due to changes in the ocean. When the surface of the ocean freezes, forming sea ice, it expels salt into the water layers below. This cold briny water is heavier and mixes deep into the ocean, including under the Ross Ice Shelf. This blocks warm ocean currents from melting the ice.

A graphic showing the interaction between cold dense waters and warmer deep flows under the Ross Ice Shelf.
Top: Cold dense shelf water blocks warm circumpolar deep water from melting the ice. Bottom: Warm circumpolar deep water flows under the ice shelf, causing ice melting and retreat.
AGU, CC BY-SA

Seafloor sediments and ice cores tell us that this deep mixing was weaker in the past when the ice sheet was retreating. This means that warm ocean currents may have flowed underneath the ice shelf and melted the ice. Mixing increased when the ice sheet was advancing.

We test these two ideas with computer model simulations of ice sheet flow and Earth’s crustal and sea surface responses to changes in the ice sheet with varying ocean temperature.

Because the rate of crustal uplift depends on the viscosity (stickiness) of the underlying mantle, we ran simulations within ranges estimated for West Antarctica. A stickier mantle means slower crustal uplift as the ice sheet thins.

The simulations that best matched geological records had a stickier mantle and a warmer ocean as the ice sheet retreated. In these simulations, the ice sheet retreats more quickly as the ocean warms.

When the ocean cools, the simulated ice sheet readvances to its present-day position. This means that changes in ocean temperature best explain the past ice sheet behaviour, but the rate of crustal uplift also affects how sensitive the ice sheet is to the ocean.

Three polar tents set up on the Ross Ice Shelf.
Changes in ocean temperature best explain the retreat of West Antarctica’s ice sheet in the past.
Veronika Meduna, CC BY-SA

What this means for climate policy today

Much attention has been paid to recent studies that show glacial melting may be irreversible in some parts of West Antarctica, such as the Amundsen Sea embayment.

In the context of such studies, policy debates hinge on whether we should focus on adapting to rising seas rather than cutting greenhouse gas emissions. If the ice sheet is already melting, are we too late for mitigation?



Read more:
We can still prevent the collapse of the West Antarctic ice sheet – if we act fast to keep future warming in check

Our study suggests it is premature to give up on mitigation.

Global climate models run under high-emissions scenarios show less sea ice formation and deep ocean mixing. This could lead to the same cold-to-warm ocean switch that caused extensive ice sheet retreat thousands of years ago.

For West Antarctica’s Siple Coast, it is better if we prevent this ocean warming from occurring in the first place, which is still possible if we choose a low-emissions future.

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