Month: May 2018

Waves Have Variable Impact On Sea Ice In The Southern Ocean, Study Finds

Over the last two decades, sea ice steadily increased in the Southern Ocean, but starting in 2016, researchers were astonished by a rapid decline. This unforeseen diminishing of sea ice highlights the inadequacy of existing models of sea ice extent and thickness. This is significant because the Southern Ocean plays a key role in regulating the global carbon cycle by regulating the uptake of carbon and heat by the ocean.

One variable for which current models do not account is the stress of ocean waves on sea ice. A collaborative of European oceanographic researchers has now published a study of the effects of ocean waves on Southern Ocean sea ice using data from the Sentinel 1 constellation. The results are published in the Proceedings of the National Academy of Sciences.

To date, Sentinel 1 consists of two satellites, Sentinel 1a and Sentinel 1b, both equipped with C-band synthetic aperture radar, which provides very high resolution imagery from which researchers can derive wave height information. The researchers tested wave height data from thousands of Sentinel images against a model of an ice edge along the y axis with an x axis pointing into the ice and a narrow wave spectrum propagating toward direction Φ relative to the x axis.

Wind generates waves over ice-free oceans, which propagate over large distances, eventually reaching ice-covered water. Propagating waves redistribute the momentum from the wind over large regions, and impart that energy to sea ice through collision. Modeling shows that the stress created by these collisions impacts the ice edge.

Of particular interest is the rate of wave decay, or attenuation. Dampened waves in sea ice indicate that energy has been imparted to the ice edge, providing a decent metric for estimating the effects of waves on sea ice extent and thickness. However, as is often the case in scientific exploration, the results are complicated.

Although the researchers conclude that wave stress is an important factor in sea ice evolution, particularly within a few hundred kilometers of the sea ice, such stresses are highly variable. They report that wave decay can happen much more quickly than previously believed, but attenuation is highly variable.

“Clearly, the strong year-round wave forcing in the Southern Ocean provides a significant force that should help maintain a compact ice edge,” the authors write, adding that associated wave motions “likely also contribute to floe breakup and rafting, resulting in the rougher (and potentially thicker) sea ice observed by scatterometers near the ice edge.”

The authors believe the dataset produced by their study could contribute to coupled wave-ice interaction models currently under development.

Does Some Dark Matter Carry An Electric Charge?

Astronomers have proposed a new model for the invisible material that makes up most of the matter in the Universe. They have studied whether a fraction of dark matter particles may have a tiny electrical charge.

“You’ve heard of electric cars and e-books, but now we are talking about electric dark matter,” said Julian Munoz of Harvard University in Cambridge, Mass., who led the study that has been published in the journal Nature. “However, this electric charge is on the very smallest of scales.”

Munoz and his collaborator, Avi Loeb of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., explore the possibility that these charged dark matter particles interact with normal matter by the electromagnetic force.

Their new work dovetails with a recently announced result from the Experiment to Detect the Global EoR (Epoch of Reionization) Signature (EDGES) collaboration. In February, scientists from this project said they had detected the radio signature from the first generation of stars, and possible evidence for interaction between dark matter and normal matter. Some astronomers quickly challenged the EDGES claim. Meanwhile, Munoz and Loeb were already looking at the theoretical basis underlying it.

“We’re able to tell a fundamental physics story with our research no matter how you interpret the EDGES result,” said Loeb, who is the chair of the Harvard astronomy department. “The nature of dark matter is one of the biggest mysteries in science and we need to use any related new data to tackle it.”

The story begins with the first stars, which emitted ultraviolet (UV) light. According to the commonly accepted scenario, this UV light interacted with cold hydrogen atoms in gas lying between the stars and enabled them to absorb the cosmic microwave background (CMB) radiation, the leftover radiation from the Big Bang.

This absorption should have led to a drop in intensity of the CMB during this period, which occurs less than 200 million years after the Big Bang. The EDGES team claimed to detect evidence for this absorption of CMB light, though this has yet to be independently verified by other scientists. However, the temperature of the hydrogen gas in the EDGES data is about half of the expected value.

“If EDGES has detected cooler than expected hydrogen gas during this period, what could explain it?” said Munoz. “One possibility is that hydrogen was cooled by the dark matter.”

At the time when CMB radiation is being absorbed, the any free electrons or protons associated with ordinary matter would have been moving at their slowest possible speeds (since later on they were heated by X-rays from the first black holes). Scattering of charged particles is most effective at low speeds. Therefore, any interactions between normal matter and dark matter during this time would have been the strongest if some of the dark matter particles are charged. This interaction would cause the hydrogen gas to cool because the dark matter is cold, potentially leaving an observational signature like that claimed by the EDGES project.

“We are constraining the possibility that dark matter particles carry a tiny electrical charge – equal to one millionth that of an electron – through measurable signals from the cosmic dawn,” said Loeb. “Such tiny charges are impossible to observe even with the largest particle accelerators.”

Only small amounts of dark matter with weak electrical charge can both explain the EDGES data and avoid disagreement with other observations. If most of the dark matter is charged, then these particles would have been deflected away from regions close to the disk of our own Galaxy, and prevented from reentering. This conflicts with observations showing that large amounts of dark matter are located close to the disk of the Milky Way.

Scientists know from observations of the CMB that protons and electrons combined in the early Universe to form neutral atoms. Only a small fraction of these charged particles, about one in a few thousand, remained free. Munoz and Loeb are considering the possibility that dark matter may have acted in a similar way. The data from EDGES, and similar experiments, might be the only way to detect the few remaining charged particles, as most of the dark matter would be neutral.

“The viable parameter space for this scenario is quite constrained, but if confirmed by future observations, of course we would be learning something fundamental about the nature of dark matter, one of the biggest puzzles that we have in physics today,” said Harvard’s Cora Dvorkin who was not involved with the new study.

Lincoln Greenhill also from the CfA is currently testing the observational claim by the EDGES team. He leads the Large Aperture Experiment to Detect the Dark Ages (LEDA) project, which uses the Long Wavelength Array in Owen’s Valley California and Socorro, New Mexico.

A paper describing these results appear in the May 31, 2018 issue of the journal Nature.

Large Magellanic Cloud: A Crowded Neighborhood

Taking advantage of the capacities of the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile, astronomers captured this very detailed new image of the Tarantula Nebula and its numerous neighbouring nebulae and star clusters. The Tarantula, which is also known as 30 Doradus, is the brightest and most energetic star-forming region in the Local Group of galaxies.

The Tarantula Nebula, at the top of this image, spans more than 1000 light-years and is located in the constellation of Dorado (The Dolphinfish) in the far southern sky. This stunning nebula is part of the Large Magellanic Cloud, a dwarf galaxy that measures about 14,000 light-years across. The Large Magellanic Cloud is one of the closest galaxies to the Milky Way.

At the core of the Tarantula Nebula lies a young, giant star cluster called NGC 2070, a starburst region whose dense core, R136, contains some of the most massive and luminous stars known. The bright glow of the Tarantula Nebula itself was first recorded by French astronomer Nicolas-Louis de Lacaille in 1751.

Another star cluster in the Tarantula Nebula is the much older Hodge 301, in which at least 40 stars are estimated to have exploded as supernovae, spreading gas throughout the region. One example of a supernova remnant is the superbubble SNR N157B, which encloses the open star cluster NGC 2060. This cluster was first observed by British astronomer John Herschel in 1836, using an 18.6-inch reflector telescope at the Cape of Good Hope in South Africa. On the outskirts of the Tarantula Nebula, on the lower right-hand side, it is possible to identify the location of the famous supernova SN 1987A.

Moving to the left-hand side of the Tarantula Nebula, one can see a bright open star cluster called NGC 2100, which displays a brilliant concentration of blue stars surrounded by red stars. This cluster was discovered by Scottish astronomer James Dunlop in 1826 while working in Australia, using his self-built 9-inch (23-cm) reflecting telescope.

At the centre of the image is the star cluster and emission nebula NGC 2074, another massive star-forming region discovered by John Herschel. Taking a closer look one can spot a dark seahorse-shaped dust structure — the “Seahorse of the Large Magellanic Cloud.” This is a gigantic pillar structure roughly 20 light-years long — almost five times the distance between the Sun and the nearest star, Alpha Centauri. The structure is condemned to disappear over the next million years; as more stars in the cluster form, their light and winds will slowly blow away the dust pillars.

Obtaining this image was only possible thanks to the VST’s specially designed 256-megapixel camera called OmegaCAM. The image was created from OmegaCAM images through four different coloured filters, including one designed to isolate the red glow of ionised hydrogen.

Hail, High Winds And Downpours Put Swathes Of France On Alert

Storm warnings were in place for much of France on Wednesday as the recent extreme weather continues to lash the country, bringing with it hail, high winds and downpours.

Some 39 departments from the south west through central France to the north east of the country were on storm alert on Wednesday with more extreme weather set to batter the country throughout the afternoon and evening.

Orange alerts – the second highest warning level – were in place with the public told to expect hail, high winds and downpours.

The public in those areas with weather warnings in place are advised to avoid unnecessary travel during storms and to take shelter. They are also advised to stay away from rivers as there may be a risk of flash floods.

Between 40mm and 60mm of rain is expected to fall in less than an hour in local areas.

The storms are forecast to begin in the south west and head north throughout Wednesday.

The weather warnings are set to remain in place until Thursday morning.

France has been lashed by storms in recent days which have even seen the Eiffel Tower struck by lightning.

On Tuesday night torrential downpours in Paris left parts of the Metro system flooded. On Wednesday morning Line 1 between Nation and Vincennes remained suspended.

‘Critical Situation’ in Northern India as Pre-Monsoon Storms Kill Dozens of People

In the past two days, at least 48 people in northern India have died in pre-monsoon storms, prompting what a government official called a “critical situation.”

The fatalities were caused by lightning as well as strong winds and heavy rain that lashed rural areas, bringing down trees and walls, TP Gupta, project manager at Uttar Pradesh’s Relief Commissioner’s Office told CNN.

Sixteen lives were claimed in Uttar Pradesh state alone, while in hardest-hit Bihar 19 people died, 11 because of lightning.

These fatalities follow at least 200 storm-caused deaths in April and May, according to Gupta.

Authorities have tried to limit casualties by airing alerts on local television channels and by sending area officials to warn residents, especially in remote communities.

Pratyaya Amrit, principal secretary of Bihar’s Disaster Management Department, told CNN that the “situation was critical.”

Lightning strikes have killed more than 2,000 people in India every year since 2005, according to India’s National Crime Statistics Bureau. This past April, lightning struck the southern Indian state of Andhra Pradesh 36,749 times in just one night.

While the north contends with turbulent pre-monsoon weather, the annual rainy season, which typically runs from June to September, has already arrived in the south of the country, as of Tuesday. According to the Indian Meteorological Department (IMD), the showers hit the country’s southern coast three days ahead of schedule.

Evacuation Order Canceled As North Carolina Dam Deemed Safe

Residents and businesses near a dam in North Carolina appeared to have dodged potential disaster Wednesday after an emergency at the location was called off.

Earlier, heavy rains and a landslide in the western North Carolina mountains “compromised the integrity” of Lake Tahoma dam and triggered urgent calls for mandatory evacuations.

Emergency officials said the dam was “at risk of imminent failure” and the weather service extended a flash flood warning for central McDowell County until 12:30 p.m.

The National Weather Service cited reports early Wednesday from McDowell County emergency management officials that “water is spilling around the sides of Lake Tahoma dam.

Evacuations ongoing south of the dam.”

But later, McDowell County emergency officials said Lake Tahoma had been inspected and deemed safe and a mandatory evacuation was halted. “The emergency at Lake Tahoma has been canceled. The evacuation order is no longer in effect. The engineer has performed a safety inspection and determined that the evacuation order is no longer needed,” according to a statement on the McDowell County 911/Emergency Management Facebook page.

“Please remain alert for additional updates, as additional rainfall is expected this afternoon. We appreciate the public’s understanding during this storm.”

Richelle Bailey, spokeswoman for McDowell County’s emergency management department, said about 2,000 people live in the evacuation area and there are about 200 people in shelters.

Bailey said that William Kehler, the county’s emergency services director, was to return home on Wednesday after serving on a team deployed to Hawaii to help emergency workers deal with the volcano there.

Landslides, evacuations, flooding

Deadly subtropical depression Alberto, the storm system drenching the Southeast, has been pounding the rugged mountains in North Carolina, spawning landslides, evacuations and flash flooding.

The National Weather Service warned residents to stay off the roads as the increased threat for landslides and debris flows continues through Wednesday night.

“We have issued a flash flood emergency for McDowell County in NC,” the service tweeted. “Flash flooding, landslides and rapid rises on waterways are an immediate threat to life and property. Do not attempt to drive unless you are fleeing flood waters.

In Rutherford County, the Town of Lake Lure and Chimney Rock Village declared a state of emergency as the Rocky Broad River surpassed seven and a half feet, officials said on the town’s Facebook page.

They said the Hickory Nut Falls Campground and the Rivercreek Campground have been evacuated.

“The Town has had to repeatedly open the floodgates just to balance the continually rising river levels from the Upper Hickory Nut Gorge,” the town said. “Residents living along the river and in other low-lying areas or areas prone to landslides are urged to take higher ground immediately.”

There is also a flash flood emergency in Marion County, NC, about 20 miles west of Asheville, with 4 to 6 inches of rain fallen, CNN meteorologist Dave Hennen reported. Life-threatening flash flooding is being reported along the Catawba River and its tributaries there.

Emergency responders also were conducting several water rescues through McDowell County but no injuries or fatalities were reported, the agency said.

Alberto had weakened to a subtropical depression Monday but millions of people in parts of Alabama, Tennessee, Georgia and Kentucky were still under flash flood watches for much of Tuesday.

Heavy rainfall drenched parts of northern Georgia, the western Carolinas and Tennessee on Tuesday, increasing the threat of flash flooding in those areas, the National Weather Service said.

After moving into the Tennessee Valley, the system is forecast to head into the Ohio Valley and Great Lakes region Wednesday and Thursday, according to the National Hurricane Center.

Florida, Mississippi and Alabama — the three states bearing the brunt of the storm — declared emergencies ahead of Alberto.

On Monday, two journalists from South Carolina-based CNN affiliate WYFF were killed in Polk County, North Carolina. A tree fell on their SUV as they covered the hazardous weather, the station said.

Alberto made landfall Monday afternoon as a subtropical storm in the Florida Panhandle, reaching maximum sustained winds of 45 mph as it arrived in Laguna Beach, according to the hurricane center.

Click here to track the storm

Hurricane season is set to begin officially Friday.

Hidden Glacier Peak Volcano Is Among Washington’s Most Dangerous

As Kilauea continues its rampage on Hawaii’s Big Island, the 38th anniversary this month of Mount St. Helens’ cataclysmic eruption is an uneasy reminder that the snow-capped volcanoes of the Pacific Northwest can awaken at any time.

Yet one of Washington’s most dangerous volcanoes remains the least-monitored and the least-studied in the Cascade range.

Tucked deep inside its namesake 566,000-acre wilderness 70 miles northeast of Seattle, Glacier Peak is the state’s hidden volcano.

At 10,541 feet, its summit doesn’t tower over the landscape like Rainier, Baker or Adams. Settlers didn’t even realize it was a volcano until the 1850s, when Native Americans told the naturalist and ethnologist George Gibbs about a small mountain north of Rainier that once smoked.

Geologists since have discovered that Glacier Peak is one of the state’s most active and explosive volcanoes, said Seth Moran, scientist-in-charge at the U.S. Geological Survey’s Cascades Volcano Observatory. Its most recent eruption, about 300 years ago, was a small one.

But since the end of the last ice age, the volcano has erupted repeatedly in at least six episodes — including two outbursts five times bigger than the blast that blew Mount St. Helens apart on May 18, 1980.

An eruption of that scale today would bury nearby the communities Darrington and Rockport under slurries of mud and debris called lahars. Roiling columns of ash more than 100,000 feet high would disrupt air traffic across the region, while sediment-laden floods could reach the Puget Sound lowlands and possibly even threaten Interstate 5.

The USGS ranks Glacier Peak among the country’s highest-threat volcanoes. But the only monitoring is done by a single seismometer southwest of the summit — far less instrumentation than on any other Cascade volcano. The agency also has yet to complete a geologic map of the area, Moran said.

The problem is partly lack of money and staff, and partly because Glacier Peak is so hard to get to, he explained. Because it’s in wilderness, geologists have to pack in all their gear — then pack out heavy rock samples.

Hiking in to a base camp takes nearly two days, then it’s a cross-country scramble to reach remote ridges and valleys in search of signs of past eruptions.

“It’s a lot of forcing your way through the devil’s club and dense forests and navigating really, really steep terrain,” Moran said.

The USGS hopes to install four seismometers soon, while geologic field studies aim to fill in gaps in the volcano’s eruptive history. But the agency estimates it needs at least a dozen instruments on Glacier Peak to effectively track the tiny earthquakes and ground motion that can signal an impending eruption, Moran said.

Progress could be accelerated if Congress approves the Volcano Early Warning and Monitoring Bill sponsored by U.S. Sen. Maria Cantwell, D-Wash. The bill, which has passed the Senate, would authorize $55 million over the next five years, partly to modernize and expand monitoring at Glacier Peak and other volcanoes.

Sponsored in the House by U.S. Rep. Don Young, R-Alaska, the bill would fund volcano research and establish a center to track data from volcanoes around the clock.

“The safety of our communities is paramount, and our legislation will ensure we have the science, technology and monitoring needed to keep people informed and safe,” Cantwell said in a statement.

In addition to explosive eruptions and lahars, Glacier Peak’s repertoire includes formation of lava domes, parts of which collapsed repeatedly during past eruptions to form scorching avalanches of rock and debris called pyroclastic flows. The flows incinerate everything in their path — which makes Glacier Peak’s lack of close neighbors a good thing.

The thick vegetation that covers the mountain makes it hard to trace the path of past pyroclastic flows and lahars, so the USGS commissioned lidar, or laser mapping, that was finished in 2016.

The technique digitally strips away vegetation, revealing the bare landscape. Features such as lahars and lava flows pop out with unprecedented clarity, Moran said.

The resulting maps underscore the risk to the Stillaguamish and Skagit Valley communities closest to the mountain, many of which were built on the thick deposits left by past lahars. In a worst-case eruption, debris flows or their muddy remnants might reach as far as Arlington, Stanwood, Mount Vernon and La Conner, according to USGS analyses.

As scientists assemble a fuller picture of Glacier Peak’s hazards, officials in Snohomish County have been working to raise awareness and reduce the danger, where possible.

The county requires anyone who wants to build in the danger zone to sign a disclosure that makes it clear the property is “subject to periodic and potentially life-threatening destructive mud, water and debris flows.”

Over the past year, emergency managers posted the first education and warning signs in the Darrington area. They plan to install more in the near future, said Dara Salmon, deputy emergency management director. County residents can sign up to get emergency alerts for a wide range of natural disasters, including eruptions and lahars.

“I think awareness is higher than it used to be,” Salmon said, “But we still have a ways to go.”