Displaying items by tag: environment

Giant iceberg splits from Antarctic

  • Published in World

By Jonathan Amos
BBC Science Correspondent

Image: Larsen C crackImage copyrightBAS
It's currently mid-winter in the Antarctic. The berg-producing crack was last filmed in the summer
One of the biggest icebergs ever recorded has just broken away from Antarctica.
The giant block is estimated to cover an area of roughly 6,000 sq km; that's about a quarter the size of Wales.
An US satellite observed the berg on Wednesday while passing over a region known as the Larsen C Ice Shelf.
Scientists were expecting it. They'd been following the development of a large crack in Larsen's ice for more than a decade.
The rift's propagation had accelerated since 2014, making an imminent calving ever more likely.
The more than 200m-thick tabular berg will not move very far, very fast in the short term. But it will need to be monitored. Currents and winds might eventually push it north of the Antarctic where it could become a hazard to shipping.
An infrared sensor on the American space agency's Aqua satellite spied clear water in the rift between the shelf and the berg on Wednesday. The water is warmer relative to the surrounding ice and air - both of which are sub-zero.
"The rift was barely visible in these data in recent weeks, but the signature is so clear now that it must have opened considerably along its whole length," explained Prof Adrian Luckman, whose Project Midas at Swansea University has followed the berg's evolution most closely.
The European Sentinel-1 satellite-radar system should also have acquired imagery in recent hours to confirm the break. Sentinel can sense any changes in the giant block's motion relative to the shelf.
How does it compare with past bergs?
The new Larsen berg is probably in the top 10 biggest ever recorded, but it is no match for some of the true monsters that have been witnessed in the Antarctic.
The largest observed in the satellite era was an object called B-15. It came away from the Ross Ice Shelf in 2000 and measured some 11,000 sq km. Six years later, fragments of this super-berg still persisted and passed by New Zealand.
In 1956, it was reported that a US Navy icebreaker had encountered an object of roughly 32,000 sq km. That is bigger than Belgium. Unfortunately, there were no satellites at the time to follow up and verify the observation.
It has been known also for the Larsen C Ice Shelf itself to spawn bigger bergs. An object measuring some 9,000 sq km came away in 1986. Many of Larsen's progeny can get wound up in a gyre in the Weddell sea or can be despatched north on currents into the Southern Ocean, and even into the South Atlantic.
A good number of bergs from this sector can end up being caught on the shallow continental shelf around the British overseas territory of South Georgia where they gradually wither away.

Media captionHelen Fricker: "Iceberg calving is the natural background mass-loss process"
What is the significance of the calving?
In and of itself, probably very little. The Larsen C shelf is a mass of floating ice formed by glaciers that have flowed down off the eastern side of the Antarctic Peninsula into the ocean. On entering the water, their buoyant fronts lift up and join together to make a single protrusion.
The calving of bergs at the forward edge of the shelf is a very natural behaviour. The shelf likes to maintain an equilibrium and the ejection of bergs is one way it balances the accumulation of mass from snowfall and the input of more ice from the feeding glaciers on land.
That said, scientists think Larsen C is now at its smallest extent since the end of the last ice age some 11,700 years ago, and about 10 other shelves further to the north along the Peninsula have either collapsed or greatly retreated in recent decades.
The two nearby, smaller shelves, Larsen A and Larsen B, disintegrated around the turn of the century; and a warming climate very probably had a role in their demise.
But Larsen C today does not look like its siblings. Prof Helen Fricker, from the Scripps Institution of Oceanography, told BBC News: "The signs we saw at Larsen A and B - we're not seeing yet. The thinning we saw for Larsen A and B - we're not seeing. And we're not seeing any evidence for large volumes of surface meltwater on the order of what you would need to hydro-fracture the ice shelf.
"Most glaciologists are not particularly alarmed by what's going on at Larsen C, yet. It's business as usual."
Map
Researchers will be looking to see how the shelf responds in the coming years; to see how well it maintains a stable configuration, and if its calving rate changes.
There was some keen interest a while back when the crack, which spread across the shelf from a pinning point known as the Gipps Ice Rise, looked as though it might sweep around behind another such anchor called the Bawden Ice Rise. Had that happened, it could have prompted a significant speed-up in the shelf's seaward movement once the berg came off.
As it is, scientists are not now expecting a big change in the speed of the ice.
One fascinating focus for future study will be a strip of "warm", malleable ice that runs east-west through the shelf, reaching the ocean edge about 100km north from the Gipps Ice Rise. This strip is referred to as the Joerg suture zone. There is a large queue of cracks held behind it.
"Calving of the iceberg is not likely itself to make the existing cracks at the Joerg Peninsula suture zone more likely to jump across this boundary," observed Chris Borstad, from the University Centre in Svalbard (UNIS).
"At this stage we really don't know whether there is some larger-scale process that might be weakening this zone, like ocean melting at the base of the shelf, or whether the current rift was just a random or episodic event that was bound to happen at some point.
"We know that rifts like this periodically propagate and cause large tabular icebergs to break from ice shelves, even in the absence of any climate-driven changes.
"I am working with a number of colleagues to design field experiments on Larsen C to answer this specific question (by measuring the properties of the Joerg suture zone directly). But until we get down there and take some more measurements we can only speculate."

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Increased risk of ozone loss over the United States in summer, evidence shows

  • Published in U.S.

Central United States vulnerable to ozone erosion from severe storms

Source:
Harvard John A. Paulson School of Engineering and Applied Sciences
Summary:
The protective stratospheric ozone layer above the central United States is vulnerable to erosion during the summer months from ozone-depleting chemical reactions, exposing people, livestock and crops to the harmful effects of UV radiation, research shows.
In the context of climate?chemistry coupling globally, the central United States in summer represents a combination of factors specific to both the geographic region and the season. Northerly flow of warm moist air from the Gulf of Mexico in combination with heating and convergence over the Great Plains frequently triggers powerful convection that injects water vapor into the stratosphere, where the upper level anticyclonic flow associated with the NAM can sequester the injection for up to a week or more over the United States. These conditions, in combination with cold stratospheric temperatures, can lead to heterogeneous catalysis on ubiquitous sulfate water aerosols that converts inorganic chlorine to ClO and can initiate ozone loss through an array of gas-phase catalytic cycles. Potential future enhancements in sulfate from volcanic injection or geoengineering increase the likelihood of halogen activation and ozone loss.
Credit: Harvard University
 
 

A new study out of Harvard University reveals that the protective stratospheric ozone layer above the central United States is vulnerable to erosion during the summer months from ozone-depleting chemical reactions, exposing people, livestock and crops to the harmful effects of UV radiation.

Powerful storm systems common to the Great Plains inject water vapor that, with observed temperature variations, can trigger the same chemical reactions over the central United States that are the cause of ozone loss over the polar regions, according to a new paper published in the Proceedings of the National Academy of Sciences.

The paper, led by James G. Anderson, the Philip S. Weld Professor of Atmospheric Chemistry at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), found that stratospheric ozone concentrations over the United States in summer are vulnerable to both increases in water vapor and observed variations in temperature from storm systems over the Great Plains. Increased frequency and intensity of these storm systems, as well as longer-term decreases in stratospheric temperatures, are expected to accompany climate change.

Using extensive aircraft observations in the Arctic stratosphere from the early 2000's, researchers established the chemical framework defining enhanced ozone loss rates with respect to temperature and water vapor. Then they employed recent NEXRAD weather radar observations to demonstrate that on average 4000 storms each summer penetrate into the stratosphere over the central United States, which is far more frequent than was previously thought.

This combination of circumstances puts the stratosphere over states including Texas, Oklahoma, Kansas, Nebraska, Iowa, Missouri, the Dakotas and states that border the Great Plains, at risk for chemical reactions that deplete ozone during summer, potentially leading to higher levels of exposure to damaging UV light from the sun.

"These developments were not predicted previously and they represent an important change in the assessment of the risk of increasing UV radiation over the central US in summer," said Mario J. Molina of the University of California San Diego, the 1995 Nobel Prize winner in stratospheric chemistry, who was not involved in this research.

Stratospheric ozone is one of the most delicate aspects of habitability on the planet. There is only marginally enough ozone in the stratosphere to provide protection from UV radiation for humans, animals and crops. Medical research specific to the United States has determined that a 1 percent decrease in the amount of ozone in the stratosphere corresponds to a 3 percent increase in the incidence of human skin cancer. There are now 3.5 million new cases of skin cancer each year reported in the US alone. Thus, for each 1 percent reduction in ozone, there would be an additional 100,000 new cases of skin cancer annually in the United States.

"Thunderstorms that hydrate the stratosphere can have significant local and regional impacts on Earth's radiation budget and climate," said Cameron R. Homeyer of the University of Oklahoma, a co-investigator on the paper. "This work demonstrates our increasing knowledge of such storms using ground-based and airborne observations and evaluates their potential for depleting stratospheric ozone now and in the future. The results strongly motivate the need for increased meteorological and chemical observations of such storms."

"Every year, sharp losses of stratospheric ozone are recorded in polar regions, traceable to chlorine and bromine added to the atmosphere by industrial chlorofluorocarbons and halons," said Steven C. Wofsy, the Abbott Lawrence Rotch Professor of Atmospheric and Environmental Science at SEAS and co-author of the study. "The new paper shows that the same kind of chemistry could occur over the central United States, triggered by storm systems that introduce water, or the next volcanic eruption, or by increasing levels of atmospheric carbon dioxide. We don't yet know just how close we are to reaching that threshold."

The scientific community has observed the chemical reactions that attack ozone over the polar regions in winter, but the important combination of observations that define the cause and the rate of stratospheric ozone loss have never been made over the central US in summer. This represents a major shortcoming in researchers' ability to forecast increases in UV radiation that might result from a volcanic event or climate change now and in the years to come.

"Rather than large continental-scale ozone loss that occurs over the polar regions in winter characterized, for example, by the term Antarctic ozone hole, circumstances over the central US in summer are very different," said Anderson. "In particular, because of the very frequent storm-induced injection events detailed by studies at Texas A&M and the University of Oklahoma using advanced radar methods, this structure of highly localized but numerous regions of potential ozone loss requires carefully specified observational strategies and systematic surveillance in order to provide the basis for accurate weekly forecasts of ozone loss."

The researchers are calling for extensive characterization of the stratosphere over the central United States in order to forecast short-term and long-term ozone loss related to increasing frequency and intensity of storm systems, higher levels of atmospheric carbon dioxide and methane, and other factors.


Story Source:

Materials provided by Harvard John A. Paulson School of Engineering and Applied SciencesNote: Content may be edited for style and length.

 

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CALIFORNIA STATE PARKS FOUNDATION’S 19th EARTH DAY RESTORATION AND CLEANUP PRESENTED BY PG&E ON SATURDAY, APRIL 22

Volunteers Needed for 41 Park Improvement Projects Statewide

Volunteers remove invasive plants as part of CSPF’s Earth Day Restoration and Cleanup.SAN FRANCISCO – On Saturday, April 22, 41 state parks across California will be the focus of California State Parks Foundation’s (CSPF) 19th Earth Day Restoration and Cleanup presented by Pacific Gas and Electric Company (PG&E). In addition to being a presenting sponsor, PG&E employees, friends and family will be on hand at 10 state parks. More than 4,000 volunteers are
needed to help with environmental improvement projects statewide.
California’s state parks receive great benefits from the work
completed by volunteers during the annual Earth Day Restoration
and Cleanup. This year, food storage lockers at campgrounds will
be installed prior to the busy summer season, fencing and gates
will be repaired, native and drought tolerant vegetation will be
planted, rain barrels will be installed and trash will be removed to
create a more welcoming and sustainable environment for visitors. Businesses and individuals are needed to actively participate with
their communities to help steward and care for California’s 280
treasured state parks..

“Earth Day is definitely one of my favorite days of the year. I am deeply moved to see people from across California working together to restore our treasured parks that are near and dear to us all,” said Susan Smartt, interim executive director of CSPF. “The out-pouring of support during this annual celebration makes a difference everyone can feel great about when they visit their favorite state park,” said Smartt.
PG&E is providing a $200,000 grant to CSPF for the supplies and materials needed to complete 10 Earth Day projects in Northern and Central California. Other sponsors include Target, Oracle, Edison International, Union Bank, Intel, The Nature Conservancy, and Microsoft.

“Over the many years that I have been involved with this event, I have been especially impressed with the dedication of my PG&E colleagues and how they involve their children and neighbors. It teaches all of us respect for the parks and outdoors and instills a sense of good stewardship which is critical for the future of these resources,” said Tom Esser, a PG&E employee and volunteer who has participated for 15 years.

CSPF project sites across California:
Angel Island State Park (PG&E sponsored) – Marin County
Anza-Borrego Desert State Park – San Diego County
Asilomar State Beach – Monterey County
Auburn State Recreation Area – Placer County
Benicia State Recreation Area– Solano County
California Citrus State Historic Park – Riverside County
Candlestick Point State Recreation Area (PG&E sponsored) – San Francisco County
Carlsbad State Beach – San Diego County
Carmel River State Beach – Monterey County
Castle Rock State Park – Santa Clara County
China Camp State Park – Marin County
Coast Dairies State Park, Panther Beach – Santa Cruz County
Crystal Cove State Park – Orange County
Cuyamaca Rancho State Park – San Diego County
Doheny State Beach – Orange County
Folsom Lake State Recreation Area (PG&E sponsored) – Sacramento County
Grover Hot Springs State Park – Alpine County
Half Moon Bay State Beach (PG&E sponsored) – San Mateo County
Henry W. Coe State Park (PG&E sponsored) – Santa Clara County
Huntington State Beach – Orange County
Lake Perris State Recreation Area – Riverside County
Lighthouse Field State Beach – Santa Cruz County
Malibu Creek State Park – Los Angeles County
McConnell State Recreation Area – Merced County
Millerton Lake State Recreation Area (PG&E sponsored) – Fresno County
Montaña de Oro State Park (PG&E sponsored) – San Luis Obispo County
Mt. Diablo State Park (PG&E sponsored) – Contra Costa County
Natural Bridges State Beach – Santa Cruz County
Portola Redwoods State Park – San Mateo County
Rio de Los Angeles State Park – Los Angeles County
Rio del Mar State Beach – Santa Cruz County
San Clemente State Beach – Orange County
San Elijo State Beach – San Mateo Campground – San Diego County
San Pasqual Battlefield State Historic Park – San Diego County
Sinkyone Wilderness State Park– Mendocino County
Sonoma Coast State Beach (PG&E sponsored) – Sonoma County
Sugarloaf Ridge State Park – Sonoma County
Sunset State Beach Park, Palm Beach – Santa Cruz County
Torrey Pines State Natural Reserve and Beach – San Diego County
Trinidad State Beach – Humboldt County
Twin Lakes State Beach, Seabright Cove – Santa Cruz County

Since its inception in 1998, CSPF’s Earth Day Restoration & Cleanup program has resulted in 83,785 participants contributing more than 334,301 volunteer hours’ worth nearly $6.6 million in park maintenance and improvements. Additionally, nearly $5 million has been raised through the Earth Day program to benefit state parks and the millions of Californians who rely on them for recreation, education, and inspiration.
-more-

To volunteer on Earth Day, visit calparks.org/earthday or call 1-415-262-4400. Space is limited, so advance registration is required. Parking fees are waived for Earth Day volunteers.
In-kind sponsors include Subway Restaurants and Peet's Coffee.

Media sponsors for 2017 include: KTVU-TV Channel 2 and KICU-TV, the Breeze 98.1, Half Moon Bay Review, Marin Independent Journal, Edible Silicon Valley and World Journal in San Francisco Bay Area; Santa Cruz Sentinel; the Sonoma Media Group including Froggy 92.9 and KSRO in Sonoma; KSOF-AM, Soft Rock 98.9 and KALZ in Fresno; Chino Hills Champion, San Clemente Times, Dana Point Times, The Capistrano Dispatch in Orange County; KLOVE/Air1, KKDO 94.7, KHITS, Entercom Sacramento, Auburn Journal and Folsom Telegraph in Sacramento; KSTT-FM and KVEC in San Luis Obispo; Riverside Press Enterprise in Riverside; and North County Sun, KSON, Sunny 98.1 and FM 94.9 in San Diego.

About Pacific Gas and Electric Company
Pacific Gas and Electric Company, a subsidiary of PG&E Corporation (NYSE:PCG), is one of the largest combined natural gas and electric energy companies in the United States. Based in San Francisco, with more than 20,000 employees, the company delivers some of the nation’s cleanest energy to nearly 16 million people in Northern and Central California. For more information, visit www.pge.com and pge.com/news.

About California State Parks Foundation
The California State Parks Foundation is a member-supported nonprofit dedicated to protecting and improving our state parks and expanding access to their natural beauty, rich culture and history, and recreational and educational opportunities for all Californians, now and in the future. For more information about the California State Parks Foundation, visit calparks.org.

Media Please Note:
For further details about the California State Parks Foundation’s 19th Earth Day, to schedule an interview, or for high resolution images, please contact Christina Mueller at (415) 215-3033 or This email address is being protected from spambots. You need JavaScript enabled to view it..
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