Connect with us

Science

Old carbon reservoirs unlikely to cause massive greenhouse gas release – EurekAlert

Published

 on


IMAGE: A thin section of an ice core collected at Taylor Glacier in Antarctica. The ice core samples contain tiny air bubbles with small quantities of ancient air trapped inside. The…
view more 

Credit: University of Rochester photo / Vasilii Petrenko

Permafrost in the soil and methane hydrates deep in the ocean are large reservoirs of ancient carbon. As soil and ocean temperatures rise, the reservoirs have the potential to break down, releasing enormous quantities of the potent greenhouse gas methane. But would this methane actually make it to the atmosphere?

Researchers at the University of Rochester–including Michael Dyonisius, a graduate student in the lab of Vasilii Petrenko, professor of earth and environmental sciences–and their collaborators studied methane emissions from a period in Earth’s history partly analogous to the warming of Earth today. Their research, published in Science, indicates that even if methane is released from these large natural stores in response to warming, very little actually reaches the atmosphere.

“One of our take-home points is that we need to be more concerned about the anthropogenic emissions–those originating from human activities–than the natural feedbacks,” Dyonisius says.

WHAT ARE METHANE HYDRATES AND PERMAFROST?

When plants die, they decompose into carbon-based organic matter in the soil. In extremely cold conditions, the carbon in the organic matter freezes and becomes trapped instead of being emitted into the atmosphere. This forms permafrost, soil that has been continuously frozen–even during the summer–for more than one year. Permafrost is mostly found on land, mainly in Siberia, Alaska, and Northern Canada.

Along with organic carbon, there is also an abundance of water ice in permafrost. When the permafrost thaws in rising temperatures, the ice melts and the underlying soil becomes waterlogged, helping to create low-oxygen conditions–the perfect environment for microbes in the soil to consume the carbon and produce methane.

Methane hydrates, on the other hand, are mostly found in ocean sediments along the continental margins. In methane hydrates, cages of water molecules trap methane molecules inside. Methane hydrates can only form under high pressures and low temperatures, so they are mainly found deep in the ocean. If ocean temperatures rise, so will the temperature of the ocean sediments where the methane hydrates are located. The hydrates will then destabilize, fall apart, and release the methane gas.

“If even a fraction of that destabilizes rapidly and that methane is transferred to the atmosphere, we would have a huge greenhouse impact because methane is such a potent greenhouse gas,” Petrenko says. “The concern really has to do with releasing a truly massive amount of carbon from these stocks into the atmosphere as the climate continues to warm.”

GATHERING DATA FROM ICE CORES

In order to determine how much methane from ancient carbon deposits might be released to the atmosphere in warming conditions, Dyonisius and his colleagues turned to patterns in Earth’s past. They drilled and collected ice cores from Taylor Glacier in Antarctica. The ice core samples act like time capsules: they contain tiny air bubbles with small quantities of ancient air trapped inside. The researchers use a melting chamber to extract the ancient air from the bubbles and then study its chemical composition.

Dyonisius’s research focused on measuring the composition of air from the time of Earth’s last deglaciation, 8,000-15,000 years ago.

“The time period is a partial analog to today, when Earth went from a cold state to a warmer state,” Dyonisius says. “But during the last deglaciation, the change was natural. Now the change is driven by human activity, and we’re going from a warm state to an even warmer state.”

Analyzing the carbon-14 isotope of methane in the samples, the group found that methane emissions from the ancient carbon reservoirs were small. Thus, Dyonisius concludes, “the likelihood of these old carbon reservoirs destabilizing and creating a large positive warming feedback in the present day is also low.”

Dyonisius and his collaborators also concluded that the methane released does not reach the atmosphere in large quantities. The researchers believe this is due to several natural “buffers.”

BUFFERS PROTECT AGAINST RELEASE TO THE ATMOSPHERE

In the case of methane hydrates, if the methane is released in the deep ocean, most of it is dissolved and oxidized by ocean microbes before it ever reaches the atmosphere. If the methane in permafrost forms deep enough in the soil, it may be oxidized by bacteria that eat the methane, or the carbon in the permafrost may never turn into methane and may instead be released as carbon dioxide.

“It seems like whatever natural buffers are in place are ensuring there’s not much methane that gets released,” Petrenko says.

The data also shows that methane emissions from wetlands increased in response to climate change during the last deglaciation, and it is likely wetland emissions will increase as the world continues to warm today.

Even so, Petrenko says, “anthropogenic methane emissions currently are larger than wetland emissions by a factor of about two, and our data shows we don’t need to be as concerned about large methane releases from large carbon reservoirs in response to future warming; we should be more concerned about methane released from human activities.”

###

This study was supported by the US National Science Foundation and the David and Lucille Packard Foundation.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

Let’s block ads! (Why?)



Source link

Continue Reading

Science

An award-winning photographer tells you how to take pictures of the night sky – CBC.ca

Published

 on


Dave Brosha is a professional photographer who, over the last 15 years, has taken highly stunning pictures of the Canadian wilderness.

It was when he was living in Yellowknife — before he pursued photography full time — that he first became interested in pointing his lens toward the skies.

“Yellowknife is known as one of the best areas on the planet for displays of the aurora borealis,” he said. “I found myself outside many, many nights under the stars.”

Since then Brosha has been short-listed multiple times for the Astronomy Photography of the Year Awards, and in 2010 he was the first runner-up in the category of land and space.

Now that he’s based in P.E.I., he splits his time between doing commercial assignments and teaching photography to people across Canada and in other parts of the world. 

Every summer, he holds a workshop on the Island with his colleague, Paul Zizka, on sunset and nighttime photography that features astrophotography, the art of capturing a picture of an object in space.

“Between Worlds.” Self-portrait photographed on the edge of a glacier in Iceland. ISO 3200, f/2.5, 30-seconds. (Dave Brosha/Dave Brosha Photography)

“There’s people that are more into deep-space photography, actually photographing the galaxies and close-ups of planets and stars and stuff like that,” Brosha said. “But to me, astrophotography is really just going out into the world once the light disappears and just exploring the beauty of that.”

Dave Brosha. (Amy Stackhouse)

Though his workshop just ended, Brosha took some time to tell CBC what beginners need to know to get into this hobby, which he says at its most barebones doesn’t require more than a fairly basic DSLR camera or a good smartphone — not even a fancy location.

“My favourite nighttime photographs have always just kind of come in my own backyard. I don’t have to drive anywhere, and it’s right there,” he said. 

“Whether exploring star trails or aurora borealis or Milky Way photographs, or just being able to go outside in your own backyard, it’s [all] pretty wonderful. 

“It helps to live in the countryside.”

Switching to manual

All good nighttime photographers — and all good photographers in general — must have a firm grasp on the concept of exposure. That’s the amount of light that’s allowed to reach the camera sensor. A picture that’s underexposed is one that looks too dark.

“Apparitions.” Photographed on a still night at low tide at Hopewell Rocks, New Brunswick. (Dave Brosha/Dave Brosha Photography)

“You have to understand the principles of capturing very small amounts of light over a longer time. So you have to know how to be able to operate your camera to capture those miniscule bits of light,” Brosha said. “It really forces you to slow down and think.”

For starters, that means ditching your camera’s auto settings. 

“You can’t really shoot night photography effectively in just auto mode. You have to learn the exposure triangle,” he said. “It takes a little bit of work, for sure. But the rewards are tremendous.”

Keep it steady

“World Goes Round”. The Old Man of Storr in the Isle of Skye, Scotland. ISO 4000, f/2.8, timelapse stitch of 45 30-second images. (Dave Brosha/Dave Brosha Photography)

The longer the camera’s shutter remains open, the larger the amount of light the camera takes in. As such, in a night photography environment, it’s common to see shutter speeds of over 20 to 30 seconds. 

But a slow shutter speed means the camera is very sensitive to any motion.

That’s great if you’re trying to capture the movement of celestial bodies such as when taking a “star trail” photograph, but even a slight movement could lead to blurry images.

Brosha said that for long exposures, it’s important to keep your camera steady. That means a good tripod is almost a must.

“If all else fails, I’ve improvised by propping my camera up on a solid surface,” Brosha said. “Using a timer on your camera rather than pressing your shutter also helps reduce camera shake.”

Check your ISO

Cranking up the ISO allows for more light to get in the camera at the expense of quality.

That could compensate for a faster shutter speed when capturing a moving object, such as when trying to capture the outlines of bright northern lights.

And having both a slow shutter speed and a high ISO could lead to highly detailed images of the night sky, such as this self-portrait with the Milky Way as a backdrop. It was taken with a 3200-ISO, and a 30-second shutter speed.

“Shine Your Light.” Self-portrait taken in The Pinnacles in Western Australia. ISO 3200, f/2.8, 30 seconds. (Dave Brosha/Dave Brosha Photography)

“When you go out there, and you even just let your eyes adjust for the dark, and you’re out there an hour, it’s remarkable how much more you see. The camera can take that even further,” Brosha said. “[It] picks up so much more.”

Perfect conditions

Brosha said that other than avoiding pouring rain, there are no real “ideal” conditions as to when to venture out, and that all types of weather can lead to interesting pictures.

“Cloudy? Reflected light pollution can actually look interesting in a long exposure. Full moon? Not the best conditions for shooting the Milky Way, but great conditions for being able to see your foregrounds,” he said.

“Where The Wild Winds Blow.” Portrait of Maggie Hood, Iceland. ISO 3200, f/2.2, 2.5-seconds. The subject was lit by an off-camera strobe. (Dave Brosha/Dave Brosha Photography)

A pitch-black night is a prime setting for taking pictures of stars. And if you’re looking to take a picture of the northern lights, you better look, well, north.

“It’s generally easier to photograph on the North Shore, when the aurora borealis is predicted. So that’s what I would probably recommend to people,” Brosha said.

Go out there and shoot

“Night Falls.” Alexandra Falls in the Northwest Territories. ISO 1600, f/7.1, 25-second exposure. (Dave Brosha/Dave Brosha Photography)

Brosha said that astrophotography may look intimidating on the surface, but that it’s not as complicated as most people might think. 

“All you have to grasp to begin is the concept of long exposure. And that usually I find for people is something that they can get the hang of pretty quickly. It just takes a little bit of practice,” he said.

Once you got that nailed down, Brosha said you can get really creative with it. And the setting allows for that.

“Every time you turn on a light, like a flashlight, your eyes kind of lose the adjustment to the nighttime that you’ve gained,” he said. 

“So you really try to function with as little light as possible. And so everything becomes slower and more deliberate.”

Plus, Brosha said, it’s a fine excuse to go outdoors.

Adblock test (Why?)



Source link

Continue Reading

Science

It's once again time for the Perseids, one of the best meteor showers of the year – CBC News

Published

 on


Each August, Earth plows through a thick trail of debris left over from a passing comet. The result: A spectacular night of meteors lighting up the sky.

One of the best and most anticipated meteor showers of the year is the Perseids, which takes place from mid-July to the end of August. But peak viewing — where you’ll get a chance to see the most meteors — falls on the night of Aug. 12-13 this year, according to the International Meteor Organization. 

That’s when Earth moves through the thickest part of the debris left over from comet 109P/Swift-Tuttle, with tiny pieces of particles burning up in our atmosphere at 59 km/s.

Try this interactive map showing how Earth passes through the meteor shower:

Swift-Tuttle, which was first discovered in 1862 independently by both Lewis Swift and Horace Tuttle, makes an orbit of the sun every 133 years. The last time it was in our solar system was in 1992. Still, from all those trips around the sun, it’s left behind plenty of debris. 

Some of this debris can be bigger than the normal grain-like particles and can create beautiful bolides, or bright fireballs that light up the sky.

How to see the meteors

Though the Perseids rarely disappoint, there is one thing to contend with this year that may hamper your viewing delight: the full moon.

With the moon lighting up the sky, that means that only the brightest of meteors will be visible. Fortunately, many Perseids tend to be quite bright anyway. 

The Perseids are given their name for the constellation — Perseus. This is the point in the sky from which they seem to appear, called the radiant.

This map shows the radiant of the Perseids, which get their name name from the nearby constellation Perseus. The radiant is the point in the sky from which the meteors seem to appear. (American Meteor Society)

While some people like to look in the direction of the constellation, which rises in the northeast, it limits the number of meteors that can be seen, since they will have shorter tails. To see longer meteors (ie., with long tails), you don’t need to look directly up, but at more of an angle.

And the best thing about meteor showers is that you don’t need a telescope or binoculars, just your own eyes.

You can also keep an eye out for “earthgrazers,” meteors that skim Earth’s atmosphere and, as a result, leave a long trail behind them.

These are best viewed early in the night, when the sky is dark and the radiant is low in the east. They will be moving roughly from north to south.

To increase your chances of catching some bright meteors, you could head out ahead of the peak night of Aug. 12, or even in the days after, when the moon won’t be entirely full. Try to keep the moon behind you when stargazing to block out its glare. 

Helpful hints

Another hot tip is to try to lie down on a blanket or even on a beach lounge chair, otherwise your neck will get tired and ache from trying to look up. 

Also, put away those phones as your eyes will need to become accustomed to the dark, something that can take anywhere from 30 minutes to an hour. And remember, the more stars you can see, the more faint meteors you will catch, so try to get to as dark a location as you can, away from city lights.

Patience is your friend, so try not to give up if you haven’t seen any meteors within a few minutes. Under ideal conditions, the Perseids can produce more than 100 meteors an hour, but don’t expect to see that many. 

At this time of year, you can also catch a couple of planets: Jupiter will be low in the east and hard to miss, and Saturn will lie in the southeast.

People can also use free apps like StarWalk or SkyView (they have a night mode that displays in red in order to preserve your night vision) that allow you to hold your phone up to the sky to identify constellations, planets and more.

There’s always something to look at in the night sky, even if meteors aren’t providing a show.

Adblock test (Why?)



Source link

Continue Reading

Science

Watch OSIRIS-REx's Complex Orbital Path Around Bennu in This Cool Animation – Universe Today

Published

 on


The OSIRIS-REx spacecraft conducted a two-year reconnaissance and sample collection at the asteroid Bennu, providing crucial data about the 500-meter-wide potentially hazardous rubble pile/space rock. When OSIRIS-REx arrived on Dec. 3, 2018, it needed some tricky navigation and precise maneuvers to make the mission work.

Experts at NASA Goddard’s Scientific Visualization Studio created an amazing visualization of the path the spacecraft took during its investigations. A short film called “A Web Around Asteroid Bennu” highlights the complexity of the mission, and the film is being shown at the SIGGRAPH computer graphics conference in Vancouver, British Columbia, Canada, a festival honoring standout works of computer animated storytelling.

Other films in the festival include Disney’s “Encanto” and Warner Brothers’ “The Batman.”

[embedded content]

Data visualizer Kel Elkins compiled the data for the film, which shows the web-like flight path for OSIRIS-REx, as well as the touch-and-go, or TAG, maneuver to collect the sample from the asteroid’s surface.

“I started working with the trajectory data in 2015,” Elkins said. “And when you first see an image of all the different maneuvers it looks like a rat’s nest. But it was really exciting to see these complicated maneuvers in 3D space.”

The video runs about four minutes in total, showing the flight path around Bennu from beginning to end in a single, continuous shot.

Screenshot from the visualization of OSIRIS-REx’s orbital path.

“From a trajectory and navigation perspective, the team really did things that have never been done before in planetary exploration,” said Mike Moreau, deputy project manager for OSIRIS-REx at NASA Goddard. “We flew the spacecraft closer to this object than any spacecraft has ever been flown before; we did maneuvers that were centimeters per second, or millimeters per second, in order to get the spacecraft exactly where it needed to be and to change its orbit.”

Taking their data visualization to the next level, Elkins and colleagues plan to release a 360-degree version of “A Web Around Asteroid Bennu” that wraps the video around the viewer, for an interactive experience on VR headsets, mobile devices, and online.

“As amazing as it is to see the trajectory in front of you in the original format, there’s something about putting the viewer in the middle of it and letting them look around,” Elkins said. “You’re in space and OSIRIS-REx is flying around you. We’re really excited to be able to publish this additional 360-degree view.”

This illustration shows the OSIRIS-REx spacecraft departing asteroid Bennu to begin its two-year journey back to Earth. Credits: NASA/Goddard/University of Arizona

OSIRIS-REx is currently on its way back towards Earth, and in September 2023, will drop off a sample in the Utah desert. Once the sample is retrieved, the spacecraft has been given a new mission, and it will be heading to one of the most infamous asteroids of them all, the potentially hazardous asteroid Apophis for an 18 month study. The mission will be renamed OSIRIS-APEX, which is short for OSIRIS-Apophis Explorer.

Source: NASA

Adblock test (Why?)



Source link

Continue Reading

Trending