In the past few years, a new term has entered the everyday lexicon: Polar vortex.
Sounds scary — and it's true, you'll want to bundle up if the polar vortex is about to affect your local weather. But it's a bit unfortunate that the polar vortex has become associated with frigid temperatures in the United States, meteorologists say. In fact, the maligned circulatory pattern is usually responsible for keeping cold air locked at the North Pole.
Usually.
Then there are those times when the polar vortex stretches its wings and sends Arctic air southward. It's not that the polar vortex goes wandering, said Jason Furtado, a meteorologist at the University of Oklahoma.
"The polar vortex is still there, spinning over the polar regions," Furtado said. "It's just the edges of it that get deformed, and you get these cold-air outbreaks that can come down."
What the polar vortex is
The polar vortex is part of a low-pressure system, and just like other lows this one spins as winds blow in toward the lower pressure at the center of the system. (A hurricane is another example of a low-pressure system that spins.) Due to Earth's spin and a phenomenon called the Coriolis effect, these systems spin counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
As the North Pole tilts away from the sun in the winter months, bathing it in 24 hours of darkness, temperature gradients form between higher and lower latitudes, Furtado said. These gradients drive winds, leading to a pattern of low pressure that circulates counterclockwise around the pole.
The polar vortex is technically in the stratosphere, the middle layer of Earth's atmosphere. That area of low pressure is about 20 miles (32 kilometers) above the Earth's surface, Furtado said. The vortex affects daily weather when it drops down into the troposphere, the lowest layer of the atmosphere. [Earth's Atmosphere: Top to Bottom (Infographic)]
Does the South Pole have a vortex?
There are polar vortexes at both the North and South Poles, with the Southern Hemisphere vortex spinning clockwise. In each case, the vortex strengthens during winter and weakens during summer. The vortex at the South Pole is more stable than the one at the North Pole, said Brian Jackson of the National Weather Service, because there are fewer land masses in the Southern Hemisphere.
"It's a more stable environment, so it's less likely to be broken down as often as the Arctic," Jackson said.
In the Arctic, when some atmospheric event interferes with this spinning air, the United States and other areas to the south may see temperatures plunge. "It's a little rare for it to come so far south that we start to see it in the U.S., but every once in a while, we get a storm system that will start to disturb it," Jackson said.
"The polar vortex itself is actually stronger during the winter, but can be disrupted by fluctuations in the atmosphere that created these events, such as strong storm systems that pull warmer air into the Arctic and force the colder air out," Jackson told Live Science.
What the polar vortex does
Usually, there's a barrier keeping that Arctic air at the North Pole — the jet stream, a river of strong winds that often travels west to east across the U.S., following boundaries between cold and hot air.
"The jet stream is the barrier between the cold, arctic air to the north, and more temperate air to the south," Jackson said. "When the jet stream surges southward in these [polar vortex] events, it allows cold Arctic air to spill in behind it."
When a storm churns the polar vortex and disrupts its smooth circulatory pattern, the shape of the vortex can stretch. Lobes form that can spill cold air southward, as is happening in the Midwest and as is forecasted to happen in the northeastern United States into the weekend. Jackson said that it's sort of like an underfilled water balloon: When you squeeze it in one place, the water balloon pops out someplace else.
Meteorologists have known about the polar vortex for more than 100 years, but the term became popularized in 2014, when back-to-back intrusions by lobes of the vortex chilled Americans in January and February. The country has also seen large polar vortex intrusions in 1977, 1982 and 1989, Jackson said.
As the Arctic air moves southward, it warms — and back at the pole, as the disturbance that weakened the vortex's flow ends, the circulatory pattern strengthens. This locks cold air back at the pole and brings relief to those shivering at lower latitudes.
How long will Arctic blast last?
You may not have to stay too bundled up for long, as meteorologists expect this blast of Arctic air to go back home soon.
"We're expecting a second lobe of this [polar vortex] event to move through early next week and start to head out by late Monday/Tuesday [Dec. 19–20]," Jackson said. "Following that, more typical patterns of temperature variations are expected to resume. In fact, after this week, patterns favor warmer-than-normal conditions for the eastern half of the country."
SAN FRANCISCO — The driest desert on Earth may have once been a patchwork of lakes and marshlands that supported the first settlers of South America as they populated the continent, new research suggests.
The new findings suggest that the bone-dry Atacama Desert, which now looks almost as devoid of life as the surface of Mars, may have once been an important stopping point in the colonization of the Americas.
Although the Atacama Desert, although it is a barrier nowadays, it wasn't at the time early people were settling the Americas, Marco Pfeiffer, a doctoral candidate in soil science at the University of California at Berkeley, said here at a news conference today (Dec. 14) at the annual meeting of the American Geophysical Union. [See Photos of the 10 Driest Places on Earth]
A long and winding route
Currently, scientists believe people from northern Asia holed up in ice-free refuges in the area around the Bering Strait for thousands of years, then spilled out into North America between 20,000 and 18,000 years ago and migrated rapidly along coastlines to occupy South America. The oldest known evidence of human occupation in South America was found at a Chilean site south of Atacama called Monte Verde, which was occupied sometime between 14,800 and 18,500 years ago. Unfortunately, evidence to recreate this early migration is sparse; archaeologists believe most of the first Americans traveled along the coastline, which is now submerged beneath 330 feet (100 meters) of water.
In theory, America's first settlers could have also fanned out into Chile's Atacama Desertduring this early period. But the barren moonscape is one of the most forbidding places on the planet.
Squished between two mountain ranges that block rainfall from both sides, the 600-mile-long (1,000 kilometer) expanse gets just 0.6 inches (15 millimeters) of rainfall a year. The hyperarid conditions produce a salty, cracked crust that today supports almost no plant life. [See Images of the Arid Atacama Desert In Bloom]
Because archaeologists assumed the area was too menacing for early human settlers to have occupied for long, no one bothered looking for evidence of ancient settlements. A few studies have suggested that between 7,000 and 9,000 years ago rainfall in some regions of the Atacama may have been up to six times the current levels.
Then, in 2013, researchers published a study in the journal Quaternary Science Reviewsrevealing something extraordinary: evidence of human occupation at a site in the bone-dry heart of the desert, dating to around 13,000 years ago, Pfeiffer said.
"The only way this site could have happened is that there was a stream nearby that can supply water to this human settlement," Pfeiffer said.
Where there is water, there is life, but the reverse is also true. So Pfeiffer and his colleagues looked for evidence of water in the desert. Soon, they found it: Buried beneath a thick salt crust, they discovered evidence of ancient plants and animals, such as gastropods and phytoliths (tiny structures found in some plant tissues), which are typically found in freshwater lakes. Dating techniques using isotopes of carbon, or versions of carbon with different numbers of neutrons, revealed that the regions were wet sometime between 17,000 and 9,000 years ago.
The new data suggest the Atacama was once covered with a series of wetlands and marshes, including marshlands peppered with grasses and sedges that would have supported ancient camelid species (such as vicuna and guanaco) as well as other now-extinct mammals, Pfeiffer said. Those, in turn, would have provided sustenance for an early population of hunter-gatherers, he said.
They have also found some hints of early human occupation in the region, though the sites have yet to be excavated and no results have been published in a peer-reviewed journal, Pfeiffer said.
Original article on Live Science.
SAN FRANCISCO — About one-quarter of the world's population lives in coastal areas that will be unlivable by the year 2100 because of rising sea levels, researchers say.
In a special issue of the journal Earth's Future, coastal scientists and engineers detailed projections for sea-level rise for the year 2100, and described their model Monday (Dec. 12) here at the annual meeting of the American Geophysical Union.
Sea-level rise is a global phenomenon, with more than 130 cities with populations of 1 million people or more along vulnerable coasts, said Robert Nicholls, a professor of coastal engineering at the University of Southampton in the U.K. [Images of Melt: Earth's Vanishing Ice]
"To really understand how this might be impacted by sea-level rise, or other kinds of change, we need to understand all of the different scales and how they interact," Nicholls said. "That's what we've been doing in this big project."
The Earth's Future research project focused on creating a new model for sea-level rise that takes a more holistic approach in considering factors that will impact coastal communities, the scientists said. The traditional "bathtub model" — which simply raises water a certain height based on estimated ice melt — takes into account only rising water levels. In their new study, researchers built a model that considers not only rising water levels, but also incorporates the impacts of tides, storm surges, coastal infrastructure and defense frameworks (such as dikes).
What they found was a much more dynamic picture of how coastal communities will be affected by rising seas. Predictions typically look 50 to 100 years into the future, when the coastal systems will have changed dramatically, said Scott Hagen, director of the Louisiana State University Center for Coastal Resiliency.
For instance, models show that if sea levels rose 6.6 feet (2 meters) — the general estimation by scientists for sea-level rise if if carbon dioxide emissions continue — for a salt marsh along the coast of Louisiana, much of the marsh area would become open water by 2100.
"When that marsh is converted to open water, then what we can consider is that a hurricane storm surge can move more freely, farther into that coastal land," Hagen said. "Knowing what's happening at these salt marsh regions is really important for us to understand the ecosystem impacts of sea-level rise in general, and climate change as a whole."
In a developed area, such as Bangladesh (one of the most vulnerable areas to sea-level rise, according to Nicholls), the new model included such systems as pollution and land use, and even poverty and health, to determine risk.
Nicholls said such considerations as the deterioration of dikes will drastically change the sea-level rise prediction. A side-by-side comparison with the traditional model showed that the new systematic model determined there could be much wider, and more devastating flooding.
"You can see that it's a rather different picture from the bathtub model, the area could easily be flooded so much more," Nicholls said. "This is just one realization of what might happen, there are a lot of different pathways. But the point is that you're getting a much richer, more detailed picture of what might happen."
Original article on Live Science.
SAN FRANCISCO — About one-quarter of the world's population lives in coastal areas that will be unlivable by the year 2100 because of rising sea levels, researchers say.
In a special issue of the journal Earth's Future, coastal scientists and engineers detailed projections for sea-level rise for the year 2100, and described their model Monday (Dec. 12) here at the annual meeting of the American Geophysical Union.
Sea-level rise is a global phenomenon, with more than 130 cities with populations of 1 million people or more along vulnerable coasts, said Robert Nicholls, a professor of coastal engineering at the University of Southampton in the U.K. [Images of Melt: Earth's Vanishing Ice]
"To really understand how this might be impacted by sea-level rise, or other kinds of change, we need to understand all of the different scales and how they interact," Nicholls said. "That's what we've been doing in this big project."
The Earth's Future research project focused on creating a new model for sea-level rise that takes a more holistic approach in considering factors that will impact coastal communities, the scientists said. The traditional "bathtub model" — which simply raises water a certain height based on estimated ice melt — takes into account only rising water levels. In their new study, researchers built a model that considers not only rising water levels, but also incorporates the impacts of tides, storm surges, coastal infrastructure and defense frameworks (such as dikes).
What they found was a much more dynamic picture of how coastal communities will be affected by rising seas. Predictions typically look 50 to 100 years into the future, when the coastal systems will have changed dramatically, said Scott Hagen, director of the Louisiana State University Center for Coastal Resiliency.
For instance, models show that if sea levels rose 6.6 feet (2 meters) — the general estimation by scientists for sea-level rise if if carbon dioxide emissions continue — for a salt marsh along the coast of Louisiana, much of the marsh area would become open water by 2100.
"When that marsh is converted to open water, then what we can consider is that a hurricane storm surge can move more freely, farther into that coastal land," Hagen said. "Knowing what's happening at these salt marsh regions is really important for us to understand the ecosystem impacts of sea-level rise in general, and climate change as a whole."
In a developed area, such as Bangladesh (one of the most vulnerable areas to sea-level rise, according to Nicholls), the new model included such systems as pollution and land use, and even poverty and health, to determine risk.
Nicholls said such considerations as the deterioration of dikes will drastically change the sea-level rise prediction. A side-by-side comparison with the traditional model showed that the new systematic model determined there could be much wider, and more devastating flooding.
"You can see that it's a rather different picture from the bathtub model, the area could easily be flooded so much more," Nicholls said. "This is just one realization of what might happen, there are a lot of different pathways. But the point is that you're getting a much richer, more detailed picture of what might happen."
Original article on Live Science.
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