Tyler O'Neal, Staff Editor EARTH SCIENCES

Washington shows how ice shards in Antarctic clouds let more solar energy reach Earth’s surface

Clouds come in myriad shapes, sizes, and types, which control their effects on climate. New research led by the University of Washington shows that the splintering of frozen liquid droplets to form ice shards inside Southern Ocean clouds dramatically affects the clouds’ ability to reflect sunlight back to space.

The paper, published March 4 in the open-access journal AGU Advances, shows that including this ice-splintering process improves the ability of high-resolution global models to simulate clouds over the Southern Ocean – and thus the models’ ability to simulate Earth’s climate. Clouds observed over the Southern Ocean on Jan. 29, 2018, during a field campaign involving the University of Washington that studied summer cloud cover around Antarctica.

“Southern Ocean low clouds shouldn’t be treated as liquid clouds,” said lead author Rachel Atlas, a UW doctoral student in atmospheric sciences. “Ice formation in Southern Ocean low clouds has a substantial effect on the cloud properties and needs to be accounted for in global models.”

Results show that it’s important to include the process whereby icy particles collide with supercooled droplets of water causing them to freeze and then shatter, forming many more shards of ice. Doing so makes the clouds dimmer, or decreases their reflectance, allowing more sunlight to reach the ocean’s surface. 

The difference between including the details of ice formation inside the clouds versus not including them was 10 Watts per square meter between 45 degrees south and 65 degrees south in the summer, which is enough energy to have a significant effect on temperature.

The study used observations from a 2018 field campaign that flew through Southern Ocean clouds, as well as data from NASA’s CERES satellite and the Japanese satellite Himawari-8.

Ice formation reduces clouds’ reflectance because the ice particles form, grow and fall out of the cloud very efficiently.

“The ice crystals deplete much of the thinner cloud entirely, therefore reducing the horizontal coverage,” Atlas said. “Ice crystals also deplete some of the liquid in the thick cores of the cloud. So the ice particles both reduce the cloud cover and dim the remaining cloud.” How ice behaves inside clouds affects the clouds’ 3-D shape and how much sunlight is reflected back to space. Arrows at the top show that the cloud on the left reflects less sunlight (smaller arrow) than the cloud on the right, so more solar energy reaches the ocean’s surface. On the left, a large rimer, or ice chunk (blue sunburst) attracts liquid water, which freezes and then shatters to create shards (blue rectangles). These shards grow as more water freezes to them, so shattering allows ice particles to grow in clouds at the expense of liquid drops. As these faster-growing, larger, ice shards fall (left side) less liquid water is left to spread out and disperse horizontally (right side).

In February, which is summer in the Southern Ocean, about 90% of the skies are covered with clouds, and at least 25% of those clouds are affected by the type of ice formation that was the focus of the study. Getting clouds right, especially in the new models that use smaller grid spacing to include clouds and storms, is important for calculating how much solar radiation reaches Earth.

“The Southern Ocean is a massive global heat sink, but its ability to take heat from the atmosphere depends on the temperature structure of the upper ocean, which relates to the cloud cover,” Atlas said.

NASA software benefits Earth, available for business, public use

Tyler O'Neal, Staff Editor EARTH SCIENCES

Many of NASA's computational innovations were developed to help explore space, but the public can download them for applications that benefit us right here on Earth. The agency’s latest software catalog has hundreds of popular programs, as well as more than 180 new ones, all available for free download. One of NASA’s most downloaded software codes, TetrUSS is a suite of computer programs used for fluid dynamics and aerodynamics analysis and design Credits: NASA

“From operations here on Earth to missions to the Moon and Mars, the software is integral to all that NASA does,” said NASA Administrator Bill Nelson. “The good news is this technology is available to the public for free. The software suited for satellites, astronauts, engineers, and scientists as it is applied and adapted across industries and businesses is a testament to the extensive value NASA brings to the United States – and the world."

NASA programs adapted and used by entrepreneurs, other government agencies, researchers, and others include:

  • TetrUSS: Aircraft emissions contribute significantly to humanity’s carbon footprint. Computational fluid dynamics programs developed at NASA allow engineers to design an aircraft’s shape to minimize drag, allowing for maximal fuel efficiency. Available in the United States, TetrUSS is one of NASA’s most downloaded applications of all time. The program has enabled users to improve designs for aircraft, automobiles, and boats, as well as gauge architectural aerodynamics and even assist in plane crash investigations.
  • WorldWind: The sheer volume of data captured by NASA’s many satellites can make it unwieldy for everyday use. WorldWind visualizes NASA data using a video game-like virtual globe of Earth, allowing users to zoom from satellite altitude down to any point on the planet’s surface. This software helps decision-makers worldwide manage scarce resources. It supports the Coast Guard by generating a map from live feeds of satellite and maritime data. And it helps researchers understand climate impacts on freshwater resources.

“In the race to mitigate the effects of human-made climate change, human-made technology can be a key advantage,” said Technology Transfer Program Executive Dan Lockney. “By making our repository of software widely accessible, NASA helps entrepreneurs, business owners, academia, and other government agencies solve real problems."

Dozens of other environmental science software programs are also ready for download. Highlights include:

  • A tool to calculate a solar power system's size and power requirements using fuel cells, solar cells, and batteries. 
  • Code to analyze solar aircraft concepts by evaluating flight worthiness and providing design feedback. 
  • Computational fluid dynamics software that can improve the efficiency of wind turbines for power generation.

Containing more than 800 programs, the NASA software catalog features categories such as system testing, aeronautics, data and image processing, autonomous systems, and more. The software is also continuously updated in a searchable repository online.

The agency will host a webinar on July 13, 2021, to allow the public to learn more about the download process and ask questions about available NASA software. Visit the information page to learn more and register:

https://go.nasa.gov/3iPFX7l

The software catalog is a product of NASA’s Technology Transfer program, managed for the agency by the Space Technology Mission Directorate. The program ensures technologies developed by and for NASA are broadly available to the public, maximizing the benefit to American taxpayers. For more information about NASA's Technology Transfer Program, visit:

https://technology.nasa.gov

What causes the deep Earth's most mysterious earthquakes?

Tyler O'Neal, Staff Editor EARTH SCIENCES

The cause of Earth's deepest earthquakes has been a mystery to science for more than a century, but a team of scientists may have cracked the case.

New research published in AGU Advances provides evidence that fluids play a key role in deep-focus earthquakes--which occur between 300 and 700 kilometers below the planet's surface. The research team includes Carnegie scientists Steven Shirey, Lara Wagner, Peter van Keken, and Michael Walter, as well as the University of Alberta's Graham Pearson.

Most earthquakes occur close to the Earth's surface, down to about 70 kilometers. They happen when stress builds up at a fracture between two blocks of rock--known as a fault--causing them to suddenly slide past each other. This close-up view of a super-deep diamond highlights its inclusions, seen here as black spots. Inclusions like these provide geochemical evidence that a sinking oceanic plate can carry water and other fluids deep into the mantle. CREDIT Photo by Evan Smith/© 2021 GIA

However, deeper into the Earth, the intense pressures create too much friction to allow this kind of sliding to occur and the high temperatures enhance the ability of rocks to deform to accommodate changing stresses. Though theoretically unexpected, scientists have been able to identify earthquakes that originate more than 300 kilometers below the surface since the 1920s.

"The big problem that seismologists have faced is how it's possible that we have these deep-focus earthquakes at all," said Wagner. "Once you get a few tens of kilometers down, it becomes incredibly difficult to explain how we are getting a slip on a fault when the friction is so incredibly high."

Ongoing work over the past several decades has shown us that water plays a role in intermediate-depth earthquakes--those that occur between 70 and 300 kilometers below Earth's surface. In these instances, water is released from minerals, which weakens the rock around the fault and allows the blocks of rock to slip. However, scientists didn't think this phenomenon could explain deep-focus earthquakes, largely because it was believed that water and other fluid-creating compounds couldn't make it far enough down into the Earth's interior to provide a similar effect.

This thinking changed for the first time when Shirey and Wagner compared the depths of rare deep-Earth diamonds to the mysterious deep-focus earthquakes.

"Diamonds form in fluids" explained Shirey, "if diamonds are there, fluids are there."

The diamonds themselves indicated the presence of fluids, however, they also brought samples of the deep-Earth to the surface for the scientists to study. When diamonds form in the Earth's interior, they sometimes capture pieces of minerals from the surrounding rock. These minerals are called inclusions and they may make your jewelry less expensive, but they are invaluable to Earth scientists. They are one of the only ways scientists can study direct samples of our planet's deep interior. 

The diamond's inclusions had the distinct chemical signature of similar materials found in oceanic crust. This means that the water and other materials weren't somehow created deep in the Earth's interior. Instead, they were carried down as part of a sinking oceanic plate.

Said Wagner: "The seismology community had moved away from the idea that there could be water that deep. But diamond petrologists like Steve were showing us samples and saying 'No, no, no. There's definitely water down here' So then we all had to get together to figure out how it got down there." 

To test the idea, Wagner and van Keken built super computational models to simulate the temperatures of sinking slabs at much greater depths than had been attempted before. In addition to the modeling, Walter examined the stabilities of the water-bearing minerals to show that under the intense heat and pressures of the Earth's deep interior, they would, indeed, be capable of holding on to water in certain conditions. The team showed that even though warmer plates didn't hold water, the minerals in the cooler oceanic plates could theoretically carry water to the depths we associate with deep-focus earthquakes. Some of Earth's largest earthquakes occur at tremendous depths (500-700 km) beneath the surface, always within or near oceanic plates that have sunk back into the Earth's interior. The cause of these events has been an enduring question in geology and geophysics for more than 40 years. In a new paper, a team of Carnegie and University of Alberta geoscientists provide several lines of evidence that fluids contribute to the genesis of deep earthquakes. New thermal modeling shows that carbonated crust and hydrated mantle in cold slabs can transport these fluids down to where deep earthquakes occur. Evidence from diamonds provides mineralogical proof of these mobile fluids in the mantle transition zone (440 - 670 km depth). This figure shows a sample thermal model of a subduction zone, with the relatively cold (blue) oceanic plate sinking into the comparatively hot (red) mantle. Three regions of earthquakes (grey spheres) visible in the oceanic plate: "intermediate-depth" dehydration-related earthquakes occurring between ~70 and ~250 km, a region of reduced seismicity between ~250 and ~350 km, and the region of "deep" seismicity below 350 km that extends to ~700 km. Superdeep diamonds (blue octahedra) are known to crystallize from fluids released in this deep region as the oceanic plate warms by the heat from the surrounding mantle. CREDIT Illustration by Steven Shirey, Peter van Keken, Lara Wagner, and Michael Walter/Carnegie Institution for Science

To solidify the study the team compared the simulations to real-life seismological data. They were able to show that the slabs that could theoretically carry water to these depths were also the ones experiencing the previously unexplained deep earthquakes.

This study is unusual in applying four different disciplines--geochemistry, seismology, geodynamics, and petrology--to the same question, all of which point to the same conclusion: water and other fluids are a key component of deep-focus earthquakes.

"The nature of deep earthquakes is one of the big questions in geoscience," said Shirey. "We needed all four of these different disciplines to come together to make this argument. It turned out we had them all in-house at Carnegie."