publishedmedium:geophysical research letters

Scientists find massive reserves of mercury hidden in permafrost
▻https://phys.org/news/2018-02-scientists-massive-reserves-mercury-hidden.html

https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/2018/5-scientistsfi.jpg

Researchers have discovered permafrost in the northern hemisphere stores massive amounts of natural mercury, a finding with significant implications for human health and ecosystems worldwide.

In a new study, scientists measured mercury concentrations in permafrost cores from Alaska and estimated how much mercury has been trapped in permafrost north of the equator since the last Ice Age.

The study reveals northern permafrost soils are the largest reservoir of mercury on the planet, storing nearly twice as much mercury as all other soils, the ocean and the atmosphere combined.

The new study was published today in Geophysical Research Letters, a journal of the American Geophysical Union.

#arctique #pollution #mercure

Scientists capture Earth’s “hum” on ocean floor - GeoSpace - AGU Blogosphere (6/12/17)
▻https://blogs.agu.org/geospace/2017/12/06/scientists-capture-earths-hum-on-ocean-floor

Scientists have long known earthquakes can cause the Earth to vibrate for extended periods of time. However, in 1998 a research team found the Earth also constantly generates a low-frequency vibrational signal in the absence of earthquakes.

Since then, seismologists have proposed different theories to explain the existence of this continuous vibration, from atmospheric disturbances to ocean waves moving over the sea floor. They’ve also measured the vibration using seismometers on land, but had not yet successfully measured it at the sea floor, which could help scientists better quantify the sources of the vibrations.

Now, using seismic instruments on the bottom of the ocean, researchers have successfully quantified Earth’s vibrational “hum”. A new study published in Geophysical Research Letters, a journal of the American Geophysical Union, determined at the ocean bottom the frequencies at which the Earth naturally vibrates, and confirmed the viability of using ocean instruments to study the hum.

Hélas pour nous (et pour @intempestive, notamment) à 10 oscillations par heure, peu d’espoir d’entendre directement les soupirs de Gaïa… Sauf à les transformer en accélérant la bande son. C’est, évidemment, suggéré dans les commentaires…

The study determined Earth’s natural vibration peaks at several frequencies between 2.9 and 4.5 millihertz. These vibrations can’t be heard by people because they are approximately 10,000 times smaller than the lower hearing threshold of the human ear, which is 20 hertz.

North Korea’s nuclear test site has collapsed ... and that may be why Kim Jong-un suspended tests | South China Morning Post
▻http://www.scmp.com/news/china/diplomacy-defence/article/2143171/north-koreas-nuclear-test-site-has-collapsed-and-may-be-why-kim-jong-un
▻https://cdn4.i-scmp.com/sites/default/files/styles/620x356/public/images/methode/2018/04/25/7ed3c416-47d3-11e8-85b3-af25d27017e0_image_hires_191717.JPG

North Korea’s mountain nuclear test site has collapsed, putting China and other nearby nations at unprecedented risk of radioactive exposure, two separate groups of Chinese scientists studying the issue have confirmed. 

The collapse after five nuclear blasts may be why North Korean leader Kim Jong-un declared last Friday that he would freeze the hermit state’s nuclear and missile tests and shut down the site, one researcher said. 

The last five of Pyongyang’s six nuclear tests have all been carried out under Mount Mantap at the Punggye-ri nuclear test site in North Korea’s northwest.

A research team led by Wen Lianxing, a geologist with the University of Science and Technology of China in Hefei, concluded the collapse occurred following the detonation last autumn of North Korea’s most powerful thermal nuclear warhead in a tunnel about 700 metres (2,296 feet) below the mountain’s peak. 

The test turned the mountain into fragile fragments, the researchers found.

Ah ! souvenirs de Beryl…

Solar eclipse caused bow waves in Earth’s atmosphere | MIT News
▻http://news.mit.edu/2018/solar-eclipse-caused-bow-waves-earths-atmosphere-0119

http://news.mit.edu/sites/mit.edu.newsoffice/files/styles/og/public/images/2018/August-2017-eclipse-atmosphere-bow-wave-chart-MIT-00.png

The celebrated Great American Eclipse of August 2017 crossed the continental U.S. in 90 minutes, and totality lasted no longer than a few minutes at any one location. The event is well in the rear-view mirror now, but scientific investigation into the effects of the moon’s shadow on the Earth’s atmosphere is still being hotly pursued, and interesting new findings are surfacing at a rapid pace. These include significant observations by scientists at MIT’s Haystack Observatory in Westford, Massachusetts.
[…]
One kind of these new waves, known as #ionospheric_bow_waves, has been predicted for more than 40 years to exist in the wake of an eclipse passage. Researchers at MIT’s Haystack Observatory and the University of Tromsø in Norway confirmed the existence of ionospheric bow waves definitively for the first time during the August 2017 event. An international team led by Haystack Observatory scientists studied ionospheric electron content data collected by a network of more than 2,000 GNSS (Global Navigation Satellite System) receivers across the nation. Based on this work, Haystack’s Shunrong Zhang and colleagues published an article in December in the journal Geophysical Research Letters on the results showing the newly detected ionospheric bow waves.

#éclipse_solaire #vague_d'étrave_ionosphérique

▻https://www.youtube.com/watch?v=8vivMEVBwys

Arctic sea ice may be declining faster than expected: study
▻https://www.reuters.com/article/us-canada-arctic-research/arctic-sea-ice-may-be-declining-faster-than-expected-study-idUSKBN1CT2JD

https://s3.reutersmedia.net/resources/r/?m=02&d=20171024&t=2&i=1206815049&w=&fh=545px&fw=&ll=&pl=&sq=&r=LYNXMPED9N1JJ#.jpg

Arctic sea ice may be thinning faster than predicted because salty snow on the surface of the ice skews the accuracy of satellite measurements, a new study from the University of Calgary said on Tuesday.

The report from the Canadian university’s Cryosphere Climate Research Group published in the academic journal Geophysical Research Letters found satellite estimates for the thickness of seasonal sea ice have been overestimated by up to 25 percent.

That means the Arctic Ocean could be ice-free much sooner than some scientific predictions, which forecast sea ice will first disappear completely during summer months between 2040 and 2050, according to lead author Vishnu Nandan.

#Caspian_Sea evaporating as temperatures rise, study finds
▻http://news.agu.org/press-release/caspian-sea-evaporating-as-temperatures-rise-study-finds
▻http://sites.agu.org/files/2017/08/The-Caspian-Sea-from-Space.jpg

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Earth’s largest inland body of water has been slowly evaporating for the past two decades due to rising temperatures associated with climate change, a new study finds.

Water levels in the Caspian Sea dropped nearly 7 centimeters (3 inches) per year from 1996 to 2015, or nearly 1.5 meters (5 feet) total, according to the new study. The current Caspian Sea level is only about 1 meter (3 feet) above the historic low level it reached in the late 1970s.

Increased evaporation over the Caspian Sea has been linked to increased surface air temperatures. According to the data from the study, the average yearly surface temperature over the Caspian Sea rose by about 1 degree Celsius (1.8 degrees Fahrenheit) between the two time frames studied, 1979-1995 and 1996-2015. These rising temperatures are likely a result of climate change, according to the study’s authors.

Evaporation brought about by warming temperatures appears to be the primary cause of the current drop in sea level and the decline will likely continue as the planet warms, according to the study’s authors.

“From our point of view as geoscientists, it’s an interesting place because it’s possible to construct a sort of budget for the total amount of water that’s there,” said Clark Wilson, a geophysicist with the Jackson School of Geosciences at the University of Texas at Austin, and co-author of the new study published in Geophysical Research Letters, a journal of the American Geophysical Union. “The real control that causes it to go up and down over long periods of time is really most likely the evaporation, which is almost completely dominated by temperature.”

#Mer_Caspienne

Study : Ship Emissions Make Thunderstorms More Intense – gCaptain
▻http://gcaptain.com/study-ship-exhaust-makes-thunderstorms-more-intense

A new study mapping lightning around the globe finds lightning strokes occur nearly twice as often directly above heavily-trafficked shipping lanes in the Indian Ocean and the South China Sea than they do in areas of the ocean adjacent to shipping lanes that have similar climates.

The difference in lightning activity can’t be explained by changes in the weather, according to the study’s authors, who conclude that aerosol particles emitted in ship exhaust are changing how storm clouds form over the ocean.

The study published Sept. 7 in Geophysical Research Letters is the first to show ship exhaust can alter thunderstorm intensity. The researchers conclude that particles from ship exhaust make cloud droplets smaller, lifting them higher in the atmosphere. This creates more ice particles and leads to more lightning.

The results provide some of the first evidence that humans are changing cloud formation on a nearly continual basis, rather than after a specific incident like a wildfire, according to the authors. Cloud formation can affect rainfall patterns and alter climate by changing how much sunlight clouds reflect to space.

“It’s one of the clearest examples of how humans are actually changing the intensity of storm processes on Earth through the emission of particulates from combustion,” said lead author Joel Thornton, a UW professor of atmospheric sciences.

Common climatic signal from glaciers in the European Alps over the last 50 years - Vincent - 2017 - Geophysical Research Letters - Wiley Online Library

▻http://onlinelibrary.wiley.com/doi/10.1002/2016GL072094/full

Merci à @freakonometrics d’avoir signalé cette recherche sur Twitter, je la référence ici.

▻http://onlinelibrary.wiley.com/store/10.1002/2016GL072094/asset/image_n/grl55507-fig-0001.png?v=1&t=izcf7pb7&s=aa38a0c7bbebfa5b0dc1da2b

Conventional glacier-wide mass balances are commonly used to study the effect of climate forcing on glacier melt. Unfortunately, the glacier-wide mass balances are also influenced by the glacier’s dynamic response. Investigations on the effects of climate forcing on glaciers can be largely improved by analyzing point mass balances. Using a statistical model, we have found that 52% of the year-to-year deviations in the point mass balances of six glaciers distributed across the entire European Alps can be attributed to a common variability. Point mass balance changes reveal remarkable regional consistencies reaching 80% for glaciers less than 10 km apart. Compared to the steady state conditions of the 1962–1982 period, the surface mass balance changes are −0.85 m water equivalent (w.e.) a−1 for 1983–2002 and −1.63 m w.e. a−1 for 2003–2013. This indicates a clear and regionally consistent acceleration of mass loss over recent decades over the entire European Alps.

#climat #glaciers

Do #comet fractures drive #surface evolution ?
▻http://blogs.esa.int/rosetta/2015/08/18/do-comet-fractures-drive-surface-evolution

Extreme thermal stresses experienced by a comet as it orbits around the Sun could explain the extensive fracturing thought to drive its long-term surface erosion, say #Rosetta scientists analysing high-resolution #Images of #Comet_67P/Churyumov-Gerasimenko’s surface. The study, which is published online in the journal Geophysical Research Letters, is based on images taken between 6 August 2014 – when #rosetta first arrived at the comet – and 1 March 2015, and includes detailed images acquired from between just 8 and 18 km from the comet’s surface. Ramy’s team identified three distinct settings in which the fractures occur: networks of long narrow fractures, fractures on cliffs and fractured boulders. In addition, several unique features were identified: the parallel fractures running across (...)

#Instruments #Science #nucleus #osiris

Rainforest loss increased in the 2000s, concludes new analysis
▻http://news.mongabay.com/2015/0225-tropical-forest-loss.html

http://mongabay-images.s3.amazonaws.com/15/0225fao-vs-kim-pan_tropical150.jpg

Loss of tropical forests accelerated roughly 60 percent during the 2000s, argues a paper published in the journal Geophysical Research Letters. The findings contradict previous research suggesting that deforestation slowed since the 1990s.

The study is based on a map of 1990 forest cover developed last year by Do-Hyung Kim and colleagues from the University of Maryland. The map, which includes 34 countries that contain 80 percent of the world’s tropical forests, enabled the researchers to establish a consistent baseline for tracking forest cover change across regions and countries over time.

The study concludes that average annual gross forest loss in the tropics rose 58 percent in the 2000s relative to the 1990s rate. Overall 78.2 million hectares of forests were lost during the decade, up from 49.3 million.

http://mongabay-images.s3.amazonaws.com/15/0225kim_country_forest600.jpg http://mongabay-images.s3.amazonaws.com/15/0225kim_percentage_loss.jpg

#déforestation #data #visualisation

A Huge Antarctic Ice Sheet Is Melting Three Times Faster Than Previously Thought | ThinkProgress
▻http://thinkprogress.org/climate/2014/12/03/3598719/amundsen-sea-ice-melt

A West Antarctic ice sheet that is roughly the size of Texas is losing the amount of ice equivalent to Mount Everest every two years, representing a melt rate that has tripled over the last decade, according to new research to be published in the journal Geophysical Research Letters on Friday.

http://d35brb9zkkbdsd.cloudfront.net/wp-content/uploads/2014/12/NASA-300x259.jpg

Science Graphic of the Week: Rising Sea Levels Show Strange Patterns | WIRED

▻http://www.wired.com/2014/11/science-graphic-week-strange-patterns-emerge-rising-sea-levels/?mbid=social_twitter

The oceans aren’t level. Over the span of decades, atmospheric weather patterns push water the water around, causing sea levels in connected basins to rise and fall somewhat predictably. However, since 2000 the two huge basins in the southern hemisphere have broken their trend, rising jointly over 2 millimeters per year.

http://www.wired.com/wp-content/uploads/2014/11/Grawk-660x268.jpg

A new paper in Geophysical Research Letters proposes that this new development, found using satellite-derived sea height data, could be due to changes in a large climate system that wraps around the entire southern hemisphere. The map above shows the different oceanic basins (which aren’t always separated by continental bodies). The Indian ocean and southern Atlantic form the largest such connected system, and historically a rise in one would result in the fall of another.

#climat #mer #élévation_niveau_marin

Ground water is depleting in the Colorado River Basin - World Socialist Web Site

▻http://www.wsws.org/en/articles/2014/08/28/colo-a28.html

Ground water is depleting in the Colorado River Basin
By Stuart Winter
28 August 2014

A recent study of water loss in the Colorado River Basin since late 2004, published in Geophysical Research Letters, has determined that 75 percent of the loss came from underground sources. Seven western US states (Wyoming, Colorado, Utah, New Mexico, Nevada, Arizona and California) rely on the Colorado River and its tributaries for water for both individual use and agriculture. It is estimated that agriculture by itself currently uses approximately 60 percent of Colorado River ground water.

#eau #états-unis #environnement #sécheresse #colorado

Arctic melt speeding up | Climate News Network

▻http://www.climatenewsnetwork.net/2014/03/arctic-melt-speeding-up

By Tim Radford

It’s long been established that Arctic ice is on the retreat but it’s the pace of change that’s surprising scientists: latest studies show the region is at its warmest for 40,000 years.

LONDON, 9 March - Ice in the Arctic continues to retreat. The season without ice is getting longer by an average of five days every 10 years, according to a new study in Geophysical Research Letters. And in some regions of the Arctic, the autumn freeze is now up to 11 days later every decade.

#arctique #climat

Bridge Or Gangplank? Study Finds Methane Leakage From Gas Fields High Enough To Gut Climate Benefit | ThinkProgress
▻http://thinkprogress.org/climate/2013/08/07/2426441/methane-leakage-gas-fields

A major new study in Geophysical Research Letters by 19 researchers — primarily from NOAA and the Cooperative Institute for Research in Environmental Sciences (CIRES) — suggests natural gas may be more of gangplank than a bridge.

Scientists used a research aircraft to measure leakage and found:

The measurements show that on one February day in the Uintah Basin, the natural gas field leaked 6 to 12 percent of the methane produced, on average, on February days.

The Environmental Defense Fund (EDF) called the emissions rates “alarmingly high.” While the researchers conducted 12 flights, “they selected just one as their data source for this paper,” ClimateWire reports. Researchers actually measured higher emissions on other flights, but atmospheric conditions during those flights “gave the data more uncertainty.”

#pollution #environnement #méthane #gaz

Mayan Tree Chopping May Have Worsened Droughts, and Contributed to The Civilization’s Demise | 80beats | Discover Magazine
►http://blogs.discovermagazine.com/80beats/2012/08/22/mayan-tree-chopping-may-have-worsened-droughts-and-contribut

a new study published in Geophysical Research Letters finds that by cutting down forests, Mayans may have directly contributed to the droughts that brought about the downfall of their society.