Large 7.6 Earthquake Hits Honduras; Tsunami Warning Issued

A 7.6-magnitude earthquake struck off the coast of Honduras, according to the U.S. Geological Survey.

The powerful quake struck about 125.4 miles north, northeast of the coast of Barra Patucca, Honduras. So far, there have been no immediate reports of damage.

The Pacific Tsunami Warning Center issued a tsunami advisory for Puerto Rico and the Virgin Islands.

The earthquake was initially recorded as a 7.8 magnitude, but then downgraded to 7.6 by USGS.

No further information was immediately available.

New Study Reveals Strong El Nino Events Cause Large Changes In Antarctic Ice Shelves

A new study published Jan. 8 in the journal Nature Geoscience reveals that strong El Nino events can cause significant ice loss in some Antarctic ice shelves while the opposite may occur during strong La Nina events.

El Niño and La Niña are two distinct phases of the El Niño/Southern Oscillation (ENSO), a naturally occurring phenomenon characterized by how water temperatures in the tropical Pacific periodically oscillate between warmer than average during El Niños and cooler during La Niñas.

The research, funded by NASA and the NASA Earth and Space Science Fellowship, provides new insights into how Antarctic ice shelves respond to variability in global ocean and atmospheric conditions.

The study was led by Fernando Paolo while a PhD graduate student and postdoc at Scripps Institution of Oceanography at the University of California San Diego. Paolo is now a postdoctoral scholar at NASA’s Jet Propulsion Laboratory. Paolo and his colleagues, including Scripps glaciologist Helen Fricker, discovered that a strong El Niño event causes ice shelves in the Amundsen Sea sector of West Antarctica to gain mass at the surface and melt from below at the same time, losing up to five times more ice from basal melting than they gain from increased snowfall. The study used satellite observations of the height of the ice shelves from 1994 to 2017.

“We’ve described for the first time the effect of El Niño/Southern Oscillation on the West Antarctic ice shelves,” Paolo said. “There have been some idealized studies using models, and even some indirect observations off the ice shelves, suggesting that El Niño might significantly affect some of these shelves, but we had no actual ice-shelf observations. Now we have presented a record of 23 years of satellite data on the West Antarctic ice shelves, confirming not only that ENSO affects them at a yearly basis, but also showing how.”

The opposing effects of El Niño on ice shelves – adding mass from snowfall but taking it away through basal melt – were at first difficult to untangle from the satellite data. “The satellites measure the height of the ice shelves, not the mass, and what we saw at first is that during strong El Niños the height of the ice shelves actually increased,” Paolo said. “I was expecting to see an overall reduction in height as a consequence of mass loss, but it turns out that height increases.”

After further analysis of the data, the scientists found that although a strong El Niño changes wind patterns in West Antarctica in a way that promotes flow of warm ocean waters towards the ice shelves to increase melting from below, it also increases snowfall particularly along the Amundsen Sea sector. The team then needed to determine the contribution of the two effects. Is the atmosphere adding more mass than the ocean is taking away or is it the other way around?

“We found out that the ocean ends up winning in terms of mass. Changes in mass, rather than height, control how the ice shelves and associated glaciers flow into the ocean,” Paolo said. While mass loss by basal melting exceeds mass gain from snowfall during strong El Niño events, the opposite appears to be true during La Niña events.

Over the entire 23-year observation period, the ice shelves in the Amundsen Sea sector of Antarctica had their height reduced by 20 centimeters (8 inches) a year, for a total of 5 meters (16 feet), mostly due to ocean melting. The intense 1997-98 El Nino increased the height of these ice shelves by more than 25 centimeters (10 inches). However, the much lighter snow contains far less water than solid ice does. When the researchers took density of snow into account, they found that ice shelves lost about five times more ice by submarine melting than they gained from new surface snowpack.

“Many people look at this ice-shelf data and will fit a straight line to the data, but we’re looking at all the wiggles that go into that linear fit, and trying to understand the processes causing them,” said Fricker, who was Paolo’s PhD adviser at the time the study was conceived. “These longer satellite records are allowing us to study processes that are driving changes in the ice shelves, improving our understanding on how the grounded ice will change,” Fricker said.

“The ice shelf response to ENSO climate variability can be used as a guide to how longer-term changes in global climate might affect ice shelves around Antarctica,” said co-author Laurie Padman, an oceanographer with Earth & Space Research, a nonprofit research company based in Seattle. “The new data set will allow us to check if our ocean models can correctly represent changes in the flow of warm water under ice shelves,” he added.

Melting of the ice shelves doesn’t directly affect sea level rise, because they’re already floating. What matters for sea-level rise is the addition of ice from land into the ocean, however it’s the ice shelves that hold off the flow of grounded ice toward the ocean.

Understanding what’s causing the changes in the ice shelves “puts us a little bit closer to knowing what’s going to happen to the grounded ice, which is what will ultimately affect sea-level rise,” Fricker said. “The holy grail of all of this work is improving sea-level rise projections,” she added.

Special Star Is A Rosetta Stone For Understanding The Sun’s Variability And Climate Effect

The spots on the surface on the Sun come and go with an 11-year periodicity known as the solar cycle. The solar cycle is driven by the solar dynamo, which is an interplay between magnetic fields, convection and rotation. However, our understanding of the physics underlying the solar dynamo is far from complete. One example is the so-called Maunder Minimum, a period in the 17th century, where spots almost disappeared from the surface of the Sun for a period of over 50 years.

A Rossetta Stone for stellar dynamos

Now, a large international team led by Christoffer Karoff from Aarhus University has found a star that can help shed light on the physics underlying the solar dynamo. The star is located 120 light years away in the constellation of Cygnus, and on the surface, the star looks just like the Sun: it has the same mass, radius and age — but inside, the chemical composition of the star is very different. It consists of around twice as many heavy elements as in the Sun. Heavy elements here means elements heavier than hydrogen and helium.

The team has succeeded in combining observations from the Kepler spacecraft with ground-based observations dating as far back as 1978, thereby reconstructing a 7.4-year cycle in this star. “The unique combination of a star almost identical to the Sun, except for the chemical composition, with a cycle that has been observed from both the Kepler spacecraft and from ground makes this star a Rosetta Stone for the study of stellar dynamos.” explains Karoff.

Heavy elements make the star more variable

By combining photometric, spectroscopic and asteroseismic data, the team collected the most detailed set of observations for a solar-like cycle in any star other than the Sun. The observations revealed that the amplitude of the cycle seen in the star’s magnetic field is more than twice as strong as what is seen on the Sun, and the cycle is even stronger in visible light.

This allowed the team to conclude that more heavy elements make a stronger cycle. Based on models of the physics taking place in the deep interior and the atmosphere of the star, the team was also able to propose an explanation of the stronger cycle. Actually, they came up with a two-part explanation. First, the heavy elements make the star more opaque, which changes the energy transport deep inside the star from radiation to convection. This makes the dynamo stronger, affecting both the amplitude of the variability in the magnetic field and the rotation pattern near the surface. The latter effect was also measured. Second, the heavy elements affect the processes on the surface and in the atmosphere of the star. Specifically, the contrast between diffuse bright regions called faculae and the quiet solar background increases as the mix of heavy elements is increased. This makes the cyclic photometric variability of the star stronger.

Can help us understand how the Sun affects our climate

The new study can help us understand how the irradiance of the Sun has changed over time, which is likely to have an effect on our climate. In general special attention is paid to the Maunder Minimum, which coincided with a period of relatively cold climate, especially in Northern Europe. The new measurements offer an important constraint on the models trying to explain the weak activity and possible reduced brightness of the Sun during the Maunder minimum.

Indonesia’s Sinabung Volcano Erupts Again

JAKARTA – Indonesia’s Sinabung volcano in northern Sumatra province erupted again on Wednesday (Dec 27), sending hot clouds into the sky.

The eruption occurred at 3.36pm local time, the country’s disaster management agency (BNPB) spokesman Sutopo Purwo Nugroho said in an update on his Twitter account.

The eruption sent black gray volcanic ash up into the sky as high as 3,500m towards the east and south-east and 4,600m in the south and south-east direction.

Volcanic ash also fell on several villages around the volcano, he said.

There were no casualties from Wednesday’s eruption as those living within the red zone around the volcano had been evacuated, he added.

“Mount Sinabung’s continuous eruptions have caused the exclusion zone to expand,” Dr Sutopo said, adding that 3,331 families who live in areas prone to the impact from the eruptions must be evacuated.

“Residents need to stay alert and listen to the government’s recommendations. We cannot predict when Mount Sinabung will stop erupting. Mount Sinabung’s volcanic and seismic parameters are still high therefore future eruptions are still likely.”

The eruption on Wednesday followed another on Dec 18.

The Indonesian authorities have imposed the highest alert on the volcano, which has been in place since 2013 when it began erupting.

Scientists Describe How Solar System Could Have Formed In Bubble Around Giant Star

Despite the many impressive discoveries humans have made about the universe, scientists are still unsure about the birth story of our solar system.

Scientists with the University of Chicago have laid out a comprehensive theory for how our solar system could have formed in the wind-blown bubbles around a giant, long-dead star. Published Dec. 22 in the Astrophysical Journal, the study addresses a nagging cosmic mystery about the abundance of two elements in our solar system compared to the rest of the galaxy.

The general prevailing theory is that our solar system formed billions of years ago near a supernova. But the new scenario instead begins with a giant type of star called a Wolf-Rayet star, which is more than 40 to 50 times the size of our own sun. They burn the hottest of all stars, producing tons of elements which are flung off the surface in an intense stellar wind. As the Wolf-Rayet star sheds its mass, the stellar wind plows through the material that was around it, forming a bubble structure with a dense shell.

“The shell of such a bubble is a good place to produce stars,” because dust and gas become trapped inside where they can condense into stars, said coauthor Nicolas Dauphas, professor in the Department of Geophysical Sciences. The authors estimate that 1 percent to 16 percent of all sun-like stars could be formed in such stellar nurseries.

This setup differs from the supernova hypothesis in order to make sense of two isotopes that occur in strange proportions in the early solar system, compared to the rest of the galaxy. Meteorites left over from the early solar system tell us there was a lot of aluminium-26. In addition, studies, including a 2015 one by Dauphas and a former student, increasingly suggest we had less of the isotope iron-60.

This brings scientists up short, because supernovae produce both isotopes. “It begs the question of why one was injected into the solar system and the other was not,” said coauthor Vikram Dwarkadas, a research associate professor in Astronomy and Astrophysics.

This brought them to Wolf-Rayet stars, which release lots of aluminium-26, but no iron-60.

“The idea is that aluminum-26 flung from the Wolf-Rayet star is carried outwards on grains of dust formed around the star. These grains have enough momentum to punch through one side of the shell, where they are mostly destroyed — trapping the aluminum inside the shell,” Dwarkadas said. Eventually, part of the shell collapses inward due to gravity, forming our solar system.

As for the fate of the giant Wolf-Rayet star that sheltered us: Its life ended long ago, likely in a supernova explosion or a direct collapse to a black hole. A direct collapse to a black hole would produce little iron-60; if it was a supernova, the iron-60 created in the explosion may not have penetrated the bubble walls, or was distributed unequally.

Other authors on the paper included UChicago undergraduate student Peter Boyajian and Michael Bojazi and Brad Meyer of Clemson University.

Indonesia’s Bali Volcano Spews Thick Smoke, Ashes

The Sunday’s eruption took place at 10:05 a.m. local time, emitting grayish thick smoke with wind detected heading for northeast, Indonesian National Disaster Mitigation Agency (BNPB) said.

“The eruption lasted for 10 minutes. White smoke was seen came out from the volcano summit after the blast,” BNPB Spokesperson Sutopo Purwo Nugroho said in a statement on Sunday.

He added that volcanic activities in the volcano remained intense at present.

Indonesian authorities imposed highest alert status on the volcano which took into effect since Nov. 27.

Sutopo pointed out that no significant impact has occurred in the last two consecutive days.

“Daily activities were normal in Bali, people remained calm. They currently have enough knowledge on impacts from the volcano’s eruption,” Sutopo added.

The top alert status was only applied within 8 to 10 kilometers from the volcano summit. People were told to refrain from conducting any activities around those areas.

“Outside those areas were still normal and safe,” he said.

The eruption which occurred on Saturday on 11:57 a.m. had prompted rain of ashes in villages located in the slope of the volcano.

Indonesian Transportation Minister Budi Karya Sumadi said on Saturday that the eruption would not affect the airports in Bali and nearby island of Lombok as the wind was heading for the east.

The ministry did not issue Notam (Notice to Airmen) related to the latest volcano eruption. The Notam notification contains information related to flight sustainability in emergency situation.

Volcanic activities of Mount Agung have been ensuing since September after 54 years of inactivity. The volcanic event has severely battered Bali’s tourism since then.

New Study Highlights Mantle Plumes and Yellowstone Supervolcano

In a new study, reported in the journal Nature Geosciences, University of Illinois geologists, Lijun Liu and graduate students Quan Zhou and Jiashun Hu used a technique called seismic tomography to peer deep into the subsurface of the western U.S. and piece together the geologic history behind the volcanism. Using supercomputers, the team ran different tectonic scenarios to observe a range of possible geologic histories for the western U.S. over the past 20 million years. The effort yielded little support for the traditional mantle plume hypothesis.

Recent stories in the national media are magnifying fears of a catastrophic eruption of the Yellowstone volcanic area, but scientists remain uncertain about the likelihood of such an event. To better understand the region’s subsurface geology, Uof I geologists have rewound and played back a portion of its geologic history, finding that Yellowstone volcanism is more far more complex and dynamic than previously thought.

“The heat needed to drive volcanism usually occurs in areas where tectonic plates meet and one slab of crust slides, or subducts, under another. However, Yellowstone and other volcanic areas of the inland western U.S. are far away from the active plate boundaries along the west coast,” said Liu who led the new research. “In these inland cases, a deep-seated heat source known as a mantle plume is suspected of driving crustal melting and surface volcanism.”

The teams goal is to develop a model that matches up with what they see both below ground and on the surface today. “We call it a hybrid geodynamic model because most of the earlier models either start with an initial condition and move forward, or start with the current conditions and move backward. Our model does both, which gives us more control over the relevant mantle processes” says graduate students Quan Zhou.

One of the many variables the team entered into their model was heat. Hot subsurface material – like that in a mantle plume – should rise vertically toward the surface, but that was not what the researchers saw in their models.

“It appears that the mantle plume under the western U.S. is sinking deeper into the Earth through time, which seems counterintuitive,” Liu said. “This suggests that something closer to the surface such as an oceanic slab originating from the western tectonic boundary – is interfering with the rise of the plume.”

As for likelihood of a violent demise of Yellowstone occurring anytime soon, the researchers say it is still too early to know. “Perhaps more importantly, this work will give us a better understanding of some of the mysterious processes deep within the Earth, which will help us better understand the consequences of plate tectonics, including the mechanism of Earthquakes and volcanoes.”