AGU 期刊一周Research Spotlights (June 02~June 08, 2016)

发布时间:2016-6-10 9:50:00 点击次数:863

I. Atmospheric Sciences

1. Measuring Atmospheric Aerosols Despite the Clouds

Researchers devise ways for remote sensors to integrate aerosol content above clouds into current methods of measurement.

2. Humans Misread Wind Speeds, Skewing a Major Hazards Database

Weather spotters who report storm measurements and observations to a U.S. national compendium of storm data often exaggerate winds speeds—by about one third, on average.


II. Geology & Geophysics

1. A New View of the Plate Dynamics Behind Earthquakes in Ecuador

Scientists get one step closer to an updated seismic hazard map that could help Ecuador prepare for future tremors.

2. Mysterious "Necklace Echoes" in the Sky Explained

Scientists studying a 50–year–old mystery in the Earth's ionosphere have come up with their best explanation of it yet.

3. New Law Puts the Squeeze on the Arizona Geological Survey

Arizona state services at risk include a program to map Earth fissures; the state's earthquake-monitoring network; and the Survey's mineral resources program.

4. Despite Dryness, Quartz Grains Can Deform in Earth's Crust

A comparison of water content in undeformed and deformed quartz indicates that grains may change shape via weakening processes that cannot be duplicated in laboratory experiments.

5. Plunging into Waterfall Sediment Transport Modeling

A first-of-its-kind model describes how pools at the base of waterfalls adjust their depth to keep up with sediment flow.


III. Science Policy

1. Climate Scientists as Activists

The pursuit of global political solutions to climate change is not for the faint of heart—but it is a matter of civic responsibility.


IV. Climate Change

1. How Tropical Cyclones Influence Photosynthesis

A new modeling study gives insight into how tropical cyclones affected ecosystems in the southeastern United States between 2002 and 2012.

2. They Got to “Ask-Me-Anything.” So, What Did They Want to Know?

On behalf of JGR: Oceans, I consented to a Reddit Science AMA. What did an anonymous public want to learn about oceanography and climate science? More importantly, what can we learn from them?

3. How Regional Wind Patterns Will Influence Climate Change

Climate change is expected to cause wet regions to get wetter and dry regions to get drier, but new research suggests that the truth is more complicated.

4. One for All, All for One: A Global River Research Network

Intermittent rivers are an increasing share of the world's river network, but current models don't include them. One research network is gathering knowledge about these rivers from around the world.


V. Planetary Sciences

1. Pharaoh's Iron Dagger Made from a Meteorite, Study Confirms

After examining the metal under bombardment by X-rays, scientists find the composition of King Tutankhamun's knife blade matches "iron of the sky."


VI.Ocean Sciences

1. Deepwater Horizon Oil Lingered and Sank, Stuck to "Marine Snow"

A new study may explain how supposedly buoyant oil from the huge 2010 oil spill coated corals and other organisms on the ocean floor.


VII.Earth and Space Science

1. GeoDeepDive: Bringing dark data to light

Data represent the lifeblood of the scientific circulatory system. For example, paleontologists constantly seek new ways to find, prepare and analyze fossil specimens to better understand Earth’s biological past. The research of thousands of paleontologists toiling over many lifetimes yields an evolving quantitative summary of the history of life; a summary that is enriched over time.

2. Slowing of landslides reflects California’s drying climate

Data from on-the-ground measurements, aerial photography, satellite imagery and satellite-radar imaging have unveiled an unexpected geological consequence of northern California’s ongoing drought.

3. In desert suburb, homes in homeowners’ associations use less water, study finds

Lush landscaping increases home values, but these plants put unnecessary strain on the Phoenix metro area’s water supply, which comes mainly from rivers and underground reservoirs, according to Elizabeth Wentz, dean of social science in the College of Liberal Arts and Sciences and a professor in the School of Geographical Sciences and Urban Planning at Arizona State University in Phoenix.


VIII. Geophysical Research Letters

1. Exhumation of the Panama basement complex and basins: Implications for the closure of the Central American seaway

The emergence of the Central American isthmus occurred episodically from Eocene to Pliocene time and was caused by a series of tectonic and volcanic processes. Results from zircon U-Pb geochronology, zircon (U-Th)/He (ZHe) and apatite (U-Th)/He (AHe) thermochronology, and zircon Lu-Hf isotopic data from sedimentary (sandstones and recent river sands) and plutonic rocks from the Azuero Peninsula and Central Panama document the exhumation and uplift history of the Panamanian basement complex. Our data support previous paleobotanical and thermochronological studies that suggest that by middle Eocene time some areas of Central Panama and Azuero Peninsula were exposed above sea level as a series of islands surrounded by shallow open marine waters. The Gatuncillo, Cobachón and Tonosí formations were deposited during this partial emergence. Transtension in the Oligocene-early Miocene produced various pull-apart basins (e.g., the Canal Basin) and local uplift that exhumed the Eocene strata (Gatuncillo and Cobachón formations). This event probably reduced circulation between the Pacific Ocean and the Caribbean Sea. The Tonosí Formation records late Miocene to Pleistocene cooling and exhumation, which may be related to uplift above the subducting Coiba Ridge. These results suggest that the emergence of the Isthmus of Panama followed a series of diachronous events that led to the final closure of the Central American seaway.

2. Oxalate formation under the hyperarid conditions of the Atacama Desert as a mineral marker to provide clues to the source of organic carbon on Mars

In this study, we report the detection and characterization of the organic minerals weddellite (CaC2O4 · 2H2O) and whewellite (CaC2O4 · H2O) in the hyperarid, Mars-like conditions of the Salar Grande, Atacama Desert, Chile. Weddellite and whewellite are commonly of biological origin on Earth and have great potential for preserving records of carbon geochemistry and possible biological activity on Mars if they are present there. Weddellite and whewellite have been found as secondary minerals occurring inside the lower detrital unit that fills the Salar Grande basin. The extremely low solubility of most oxalate minerals inhibits detection of oxalate by ion chromatography (IC). Crystalline oxalates, including weddellite and whewellite, were detected by X-ray diffraction (XRD). The association of weddellite with surface biota and its presence among subsurface detrital materials suggest the potential of a biological origin for Salar Grande weddellite and whewellite. In this regard, biological activity is uniquely capable of concentrating oxalates at levels detectable by XRD. The complementary detection of oxalate-bearing phases through IC in the upper halite-rich unit suggests the presence of a soluble oxalate phase in the basin that is not detected by XRD. The formation, transport and concentration of oxalate in the Salar Grande may provide a geochemical analogue for oxalate-bearing minerals recently suggested to exist on Mars.

3. The Rigid-Plate and Shrinking-Plate Hypotheses: Implications for the Azimuths of Transform Faults

The rigid-plate hypothesis implies that oceanic lithosphere does not contract horizontally as it cools (hereinafter “rigid plate”). An alternative hypothesis, that vertically averaged tensional thermal stress in the competent lithosphere is fully relieved by horizontal thermal contraction (hereinafter “shrinking plate”), predicts subtly different azimuths for transform faults. The size of the predicted difference is as large as 2.44° with a mean and median of 0.46° and 0.31° respectively and changes sign between right-lateral- (RL-) and left-lateral- (LL-) slipping faults. For the MORVEL transform fault data set, all six plate pairs with both RL- and LL-slipping faults differ in the predicted sense, with the observed difference averaging 1.4° ± 0.9° (95% confidence limits.), which is consistent with the predicted difference of 0.9°. r, the sum-squared normalized misfit to global transform fault azimuths is minimized for γ = 0.8 ± 0.4 (95% confidence limits) where γ is the fractional multiple of the predicted difference in azimuth between the shrinking-plate (γ = 1) and rigid-plate (γ = 0) hypotheses. Thus observed transform azimuths differ significantly between RL-slipping and LL-slipping faults, which is inconsistent with the rigid-plate hypothesis, but consistent with the shrinking-plate hypothesis, which indicates horizontal shrinking rates of 2% Ma-1 for newly created lithosphere, 1% Ma−1 for 0.1-Ma-old lithosphere, 0.2% Ma−1 for 1-Ma-old lithosphere, and 0.02% Ma−1 for 10 Ma-old-lithosphere, which are orders of magnitude higher than the mean intraplate seismic strain rate of ~10−6 Ma−1 (5 × 10−19 s−1).

4. Revealing the early ice flow patterns with historical Declassified Intelligence Satellite Photographs back to 1960s

The reconnaissance ARGON satellites collected the earliest images of Antarctica from space dating back to the 1960s, providing valuable historical baseline information for studying polar ice sheets. Those photographs are under-utilized for ice motion mapping, due to lack of sufficient ground controls for image orthorectification. In this study, we orthorectified the ARGON photographs by fully exploiting the metric qualities of WorldView satellite images: very high spatial resolution and precise geolocation. Through a case study over Larsen Ice Shelf, we demonstrated that the camera model with bundle block adjustment can achieve geolocation accuracy of better than the nominal resolution (140 m) for orthorectifying ARGON images, with WorldView imagery as ground control source. This allowed us to extend the ice velocity records of Larsen Ice Shelf back into 1960s ~ 1970s for the first time. The retrospective analysis revealed that acceleration of the collapsed Larsen B occurred much earlier than previously thought.


IX. AUG Newsroom

1. ANTARCTIC COASTLINE IMAGES REVEAL FOUR DECADES OF ICE LOSS TO OCEAN

A study of images along 2000 kilometers (1,240 miles) of West Antarctica’s coastline has shown the loss of about 1000 square kilometers (about 390 square miles) of ice – an area equivalent to the city of Berlin – over the past 40 years.