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Mittwoch, 30. November 2016

Huge Cracks In the West Antarctic Ice Sheet May Signal Its Collapse



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Huge Cracks In the West Antarctic Ice Sheet May Signal Its Collapse
// Gizmodo

A new rift in West Antarctica's Pine Island Glacier, photographed during a NASA Operation IceBridge flyover on November 4th, 2016. Image: NASA/Nathan Kurtz

Last year, a 225 square-mile chunk of West Antarctica's Pine Island Glacier broke off and tumbled into the sea. Now, Earth scientists at Ohio State University have pinpointed the root cause of the iceberg calving event: a crack that started deep below ground and 20 miles inland.

It's like nothing scientists have witnessed in West Antarctica before, and it doesn't bode well for the ice sheet's future.

A frozen fortress containing enough water to raise global sea levels many feet should it melt, the West Antarctic ice sheet is separated from the ocean by a series of large glaciers. For now, these glaciers act like corks in wine bottles to hold the ice at bay, but that may not be the case for much longer. Recent research has shown that Pine Island, Thwaites, and other glaciers along the Amundsen sea are retreating rapidly, as warm ocean waters lap against their margins. At this point, NASA says, collapse of the entire Amundsen sea sector appears to be "unstoppable."

The biggest question on everyone's mind is how quickly all of that ice will go, and to find out, we need to pinpoint the mechanisms responsible for ice sheet collapse. To that end, a study published today in Geophysical Research Letters takes a deep dive into an iceberg calving event in the summer of 2015. It arrives at a startling conclusion.

Bird's eye view of the Amundsen sea embayment, where major glaciers of the West Antarctic ice sheet empty into the ocean. Pope, Smith, and Kohler glaciers were the focus of this study. Image: NASA/GSFC/SVS

"The calving event itself wasn't a big deal," lead study author Ian Howat of Ohio State University told Gizmodo, noting that iceberg break-offs of this size happen about every 5 to 6 years at Pine Island. "What made this one different is how it got started."

At Pine Island and elsewhere along the Amundsen sea embayment, calving occurs at the glacier's outer margin, where the ice shelf is detached from bedrock. "It's kinda like a diving board sticking out over a pool," Howat said. Normally, cracks will start to form in areas experiencing extreme shear from ice flowing off the continent. They'll propagate laterally across the shelf, eventually causing the entire diving board to break away.

Not so with last year's Pine Island calving event. Analyzing several years of images taken by the Sentinel-1A satellite, Howat and his colleagues traced the break-off to a rift that formed at the base of the ice shelf nearly 20 miles inland, in 2013. Over the course of two years, the rift propagated all the way from bottom to top, until finally, it spat out an iceberg ten times the size of Manhattan.

What could have caused so much ice to break away in this unusual manner? In all likelihood, melting that started at the contact point between ice and bedrock is to blame. This would explain why the rift overlapped with a topographic valley—a place where the ice appeared to have thinned—in satellite images taken before the calving.

"I think what we're seeing is the surface expression of a much bigger valley at the base of the ice shelf," Howat said. "This tells us the ice shelf has weaknesses that are being exploited by increased ocean temperatures."

Troublingly, as waters around West Antarctica heat up, those weaknesses could be exploited more and more often. "If the ice sheet was going to retreat very slowly on long timescales, we'd just expect to see the usual calving," Howat said. "This event gives us a new mechanism for ice sheets falling apart quickly. It fits into that picture of a rapid retreat."

Howat noted that a second interior ice shelf rift (pictured above) was spotted during a NASA Operation Ice Bridge survey earlier this month. And there are many other topographic valleys—possible sites of future calving events—further up-glacier, but our ability to study them is hampered by a lack of good data.

One can't help but note that NASA's Earth science program, which makes such data available to scientists and the public, faces the possibility of major cuts under a Trump administration. These cuts would come at the precise moment when our planet is changing in rapid and hard-to-predict ways, which is when Earth science research is needed the most. Like cracks in an ice sheet, the irony runs deep.

[Geophysical Research Letters via OSU News]


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Sigurd A.Röber

The Great Barrier Reef Just Suffered the Worst Die-Off Ever Seen



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The Great Barrier Reef Just Suffered the Worst Die-Off Ever Seen
// Gizmodo

Dead table corals killed by bleaching, Northern GBR, November 2016. (Image: ARC Centre of Excellence For Coral Reef Studies)

Abnormally high water temperatures caused by you-know-what are being blamed for the worst coral die-off ever recorded along Australia's Great Barrier Reef.

Earlier this year, scientists at the ARC Centre of Excellence For Coral Reef Studies warned that the Reef is in big trouble, with about 35 percent of the coral in its northern and central areas either dead or dying. An updated survey conducted over the past two months, including investigations done from the air and underwater, shows that things have gotten considerably worse.

A scientist assesses coral mortality following a bleaching event. (Image: ARC Centre of Excellence For Coral Reef Studies)

In the northern regions, a 430 mile (700 km) stretch of reef lost an average of 67 percent of its shallow-water corals in the past nine months. In an area around Lizard Island in Far North Queensland, around 90 percent of the coral had died. The scientists said the impact was far worse than anticipated following the surveys done back in April of this year.

Staghorn corals killed by bleaching on the Northern GBR, November 2016. (Image: ARC Centre of Excellence For Coral Reef Studies)

These die-offs, called coral bleaching, happen when high water temperatures persist for an extended period of time, causing corals to expel their zooxanthella, a colorful algae that lives in their tissue. During the first five months of 2016, sea surface temperatures across the Great Barrier Reef were the hottest on record—a full one degree Celsius higher than the monthly average. The resulting heat stress did a lot of damage, but the loss of photosynthesizing zooxanthella triggered the lion's share of the die-offs, by causing corals to starve.

Average coral loss along each section of the Great Barrier Reef. (Image: ARC Centre of Excellence For Coral Reef Studies)

"Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef," noted ARC Centre scientist Terry Hughes in a statement. "This region escaped with minor damage in two earlier bleaching events in 1998 and 2002, but this time around it has been badly affected." Hughes says the increase in water temperature is being caused by carbon emissions, and warns that massive coral bleaching events could become an annual occurrence within two decades.

The good news, says Hughes, is that the southern two-thirds of the Reef escaped with minor damage. Regions to the south appeared much healthier, experiencing losses between one and six percent. "The corals have now regained their vibrant colour, and these reefs are in good condition," said Andrew Baird, an ARC Centre diver who visited the reefs in October and November.

Coral bleaching, in addition to triggering tremendous losses of marine life, affects tourism along the Reef—an industry that brings in $5 billion annually and employs around 70,000 people. Reefs can recover from bleaching events, but it takes time for the algae to return. Should nothing be done to curb greenhouse gas emissions, and if Hughes is right about bleaching events happening each year, the Great Barrier Reef will never recover, putting an end to one of the most majestic biological structures on the planet.

[ARC Centre of Excellence For Coral Reef Studies]


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Sigurd A.Röber

Montag, 21. November 2016

Röring: „Wir müssen uns ändern“ - agrarheute.com


 
Bild.: Sigurd Roeber©
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Röring: „Wir müssen uns ändern" - agrarheute.com
// Google News: Wirtschaft


agrarheute.com

Röring: „Wir müssen uns ändern"
agrarheute.com
„Wir müssen uns als Landwirtschaft in manchen Punkten ändern." Mit diesen Worten hat WLV-Präsident Johannes Röring eine umfassende „Offensive Nachhaltigkeit" angekündigt. Der Westfälisch-Lippische Landwirtschaftsverband (WLV) nimmt die ...
WLV will Verbraucher mit "offensiver Nachhaltigkeit" überzeugentop agrar online
Bauern wollen schlechtes Ansehen der Landwirtschaft verbessernNOZ - Neue Osnabrücker Zeitung
Landwirtschaftsverband Westfalen-Lippe benennt FehlerDIE WELT

Alle 5 Artikel »

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Sigurd A.Röber

Boliviens Regierung ruft wegen Dürre Notstand aus - tagesschau.de

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Boliviens Regierung ruft wegen Dürre Notstand aus - tagesschau.de
// Google News: Wirtschaft


tagesschau.de

Boliviens Regierung ruft wegen Dürre Notstand aus
tagesschau.de
Bolivien erlebt momentan die schwerste Dürre seit 25 Jahren. In sieben der zehn größten Städte des Landes herrscht bereits Wasserknappheit. Nun rief die Regierung den Katastrophenfall aus und wies die Bevölkerung an, Wasser zu sparen.
Proteste: Regierung in Bolivien ruft wegen schwerer Dürre Notstand ausDIE WELT
Schwerste Dürre seit 25 Jahren: Bolivien ruft nationalen Notstand ausn-tv.de NACHRICHTEN

Alle 6 Artikel »

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Sigurd A.Röber

Mittwoch, 2. November 2016

Deutschland ohne Plan bei Weltklimakonferenz von Marrakesch



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Deutschland ohne Plan bei Weltklimakonferenz von Marrakesch
// DW.de - News

Es war so gut gedacht: Umweltministerin Hendricks wollte in Marrakesch mit einem "Klimaschutzplan 2050" auftrumpfen. Doch die Gegenwehr von Unions-geführten Ministerien - und wohl auch von Genosse Gabriel - war zu groß. Bundesumweltministerin Barbara Hendricks rechnet nicht mehr mit einem deutschen Klimaschutzplan zur Weltklima-Konferenz Mitte November in Marrakesch. "Ich sehe keine Chance mehr", sagte die SPD-Politikerin in Berlin. Sie hätte es zwar gerne gesehen, wenn der Plan vorher beschlossen worden wäre. Die Blockadehaltung der Unionsparteien sei aber zu groß. Immerhin machten die Gespräche mit den CSU-geführten Ressorts Landwirtschaft und Verkehr Fortschritte, so dass eine Einigung noch dieses Jahr möglich sei. Hendricks machte zudem deutlich, dass die Energiebranche ihren CO2-Ausstoß stärker drosseln müsse als zuletzt vorgesehen. Die sei allein deshalb nötig, um die deutschen Klimaziele für 2020 noch zu schaffen. Ministerien für Verkehr und Landwirtschaft auf Anti-Kurs Der "Klimaschutzplan 2050" soll den Weg in eine Gesellschaft aufzeigen, die nahezu vollständig auf den Ausstoß von klimaschädlichen Gasen verzichtet. Er basiert auch auf dem 2015 in Paris beschlossenem Weltklimavertrag. Die Konferenz von Marrakesch in Marokko vom 7. bis 18. November soll versuchen, die ambitionierten Vorgaben tatsächlich umzusetzen. So müssen die Industrieländer ihre Zusage konkretisieren, ab 2020 jährlich hundert Milliarden Dollar (92 Milliarden Euro) für den Klimaschutz und die Bewältigung der Klimafolgen in armen Ländern bereitzustellen. In Paris hatten sich die Staaten völkerrechtlich zum Klimaschutz verpflichtet und vereinbart, so schnell wie möglich weltweit einen Wendepunkt beim Ausstoß klimaschädlicher Emissionen zu erreichen und die Erderwärmung auf "deutlich unter zwei Grad" zu begrenzen. Deutschland wollte seine Position in Marrakesch mit dem "Klimaschutzplan 2050" stärken. Diesen wollte Hendricks am Mittwoch im Kabinett beschließen ... Ganzen Artikel lesen »



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Sigurd A.Röber