AGU 期刊一周Research Spotlights (Apr 21~Apr 27, 2016)

发布时间:2016-4-28 15:13:50 点击次数:944


 I. Atmospheric Sciences

1. A Decade of Progress in Stratospheric Aerosol Research

Enhanced technology and chemistry-climate models have advanced our understanding of the sources and processes controlling the evolution of the stratospheric aerosol layer, the so-called Junge layer.

2. Blowin’ in the Wind: Observing Stratospheric Aerosols

New observations and understanding of stratospheric particles are crucial for evaluating their role in climate change.


II. Geology & Geophysics

1. What Makes Long-Runout Landslides So Mobile?

New research shows that acoustic waves rippling through some large landslides can reduce friction and allow slides to run out long distances.

2. Crowdsourced Seismology

The seismologists of the world want to turn you into an earthquake detector.

3. A Hole in Earth's Surface

Research shows that a broken lithosphere underneath the island of Hawai'i could explain the island's patterns of seismic activity.


III. Hazards & Disasters

1. Sustaining Existence: A Geoethical Dilemma

Would communicating science be more effective if geoethics were included in the discussion?


IV. Ocean Sciences

1. What Causes Long-Term North Atlantic Surface Temperature Cycles?

New evidence strengthens a likely link between 20- to 40-year sea surface temperature fluctuations and varying ocean circulation patterns.


V.Hydrology, Cryosphere & Earth Surface

1. Arctic Sea Ice Extent May Shrink Below 2012 Record Low

Satellite data, field measurements, and readings from "snow buoys" reveal ice thickness patterns similar to those preceding the lowest recorded sea ice extent, which was reached nearly 4 years ago.


VI. Space & Planets

1. Electrons Thrown Off Course in Near-Earth Magnetic Reconnection

NASA Magnetospheric Multiscale (MMS) mission detects energy differences in electrons scattered by magnetic reconnection.


VII. Climate Change

1. Finance Head Urges Strong Climate Mitigation, Adaptation Steps

Countries ratifying the Paris climate agreement need strong financial incentives to convince them to choose renewables over fossil fuels, according to World Bank president.

2. New Climate Studies: Worse Risks at 2°C Rise, Higher Rise Likely

Although the Paris agreement scheduled to be signed 22 April aims for a 2°C warming cap, new findings show that even a 1.5°C rise will hit glaciers hard.

3. U.S. Energy Secretary Says Paris Accord Cuts Are Not Enough

Moniz foresees progress on climate change in the United States no matter who wins the U.S. presidential election.

4. Challenges and Opportunities in Earth-Human Systems Research

Opportunities for Integration of Remote Sensing, Integrated Assessment, and Adaptation; Aspen, Colorado, 11–16 October 2015


VIII. Geochemistry, Mineralogy, Volcanology

1. Gypsum Forms in an Unexpected Way

Scientists spot the "stem cell" building blocks that lay the foundation for gypsum's formation.


IX. Space Science & Space Physics

1. Ionospheric Waves Linked to Polar Atmospheric Dynamics

Ionospheric waves are likely to be caused by processes in the polar atmosphere rather than by space weather.


X.Earth and Space Science

1. Idling diesel engines may produce dangerous pollutant

New research finds exhaust from idling diesel engines produces a significant amount of isocyanic acid when photons from sunlight help it react with other compounds in the atmosphere. The amount of this secondary photochemical isocyanic acid produced by non-road, idling diesel engines, like those in tractors, loaders, and other heavy construction and farm equipment, was 50 to 230 milligrams per kilogram of diesel burned, according to the new study. That comes to about 150 to 700 milligrams per gallon burned. That’s also two to six times greater than the amount of isocyanic acid produced by diesel engines running at higher speed and under a load, like cars and trucks driving on a highway, the new research found.

2. Action on climate change needs our hearts and heads: uniting our faith and science

We scientists are eyewitnesses to the changes occurring in our world. Every month, it seems, a new record is being broken: whether for global temperature, Greenland ice melt, hurricane intensification, heavy rainfall, or devastating heat waves.

3. Among Waves and Whirlwinds: A Mid-Cruise Account

On the morning of the 19th, the R/V Falkor entered harbor in the country of Tonga after nearly 12 days at sea. As we stood on the deck watching the dockworkers heave lines to and fro, several scientists breathed a sigh of relief, for we had spent a number of days being tossed around by the sea. It was by no means a severe beating, and the R/V Falkor is known for her ability to move swiftly and steadily through waves and swells. Still, if one is susceptible to seasickness, being in harbor or on land is a pleasant respite.

4. Asian irrigation influences East African rain

Irrigation from agriculture can directly influence climate thousands of kilometers away and even leap across continents, new research finds. Up to 40 percent of the rain in some regions of East Africa can be attributed to irrigation used in agriculture in Asia, according to a new study published in Geophysical Research Letters, a journal of the American Geophysical Union.


XI. Geophysical Research Letters

1. Laboratory measurements of heterogeneous CO2ice nucleation on nanoparticles under conditions relevant to the Martian mesosphere

Clouds of CO2 ice particles have been observed in the Martian mesosphere. These clouds are believed to be formed through heterogeneous nucleation of CO2 on nanometer-sized meteoric smoke particles (MSPs) or upward propagated Martian dust particles (MDPs). Large uncertainties still exist in parameterizing the microphysical formation process of these clouds as key physico-chemical parameters are not well known. We present measurements on the nucleation and growth of CO2 ice on sub 4 nm radius iron oxide and silica particles representing MSPs at conditions close to the mesosphere of Mars. For both particle materials we determine the desorption energy of CO2 to be Fdes = (18.5 ± 0.2) kJ mol1 corresponding to Fdes = (0.192 ± 0.002) eV and obtain m = 0.78 ± 0.02 for the contact parameter that governs heterogeneous nucleation by analyzing the measurements using classical heterogeneous nucleation theory. We did not find any temperature dependence for the contact parameter in the temperature range examined (64 K to 73 K). By applying these values for MSPs in the Martian mesosphere, we derive characteristic temperatures for the onset of CO2 ice nucleation, which are 8 - 18 K below the CO2 frost point temperature, depending on particle size. This is in line with the occurrence of highly supersaturated conditions extending to 20 K below frost point temperature without the observation of clouds. Moreover, the sticking coefficient of CO2 on solid CO2 was determined to be near unity. We further argue that the same parameters can be applied to CO2 nucleation on upward propagated MDPs. 

2. Interplay of Drought and Tropical Cyclone Activity in SE US Gross Primary Productivity

Tropical cyclones (TCs), often associated with massive flooding and landslides in the Southeast US (SE US), provide a significant input of freshwater to the hydrologic system, and their timing and trajectory significantly impact drought severity and persistence. This manuscript investigates the sensitivity of gross primary productivity (GPP) in the SE US to TC activity using the 1D column implementation of the Duke Coupled Hydrology Model with Vegetation (DCHM-V) including coupled water and energy cycles and a biochemical representation of photosynthesis. Decadal-scale simulations of water, energy and carbon fluxes were conducted at high temporal (30-min) and spatial (4 km) resolution over the period 2002-2012. At local scales, model results without calibration compare well against AmeriFlux tower data. At regional scales, differences between the DCHM-V estimates and the MODIS GPP product reflect the spatial organization of soil hydraulic properties and soil moisture dynamics by physiographic region, highlighting the links between the water and carbon cycles. To isolate the contribution of TC precipitation to SE US productivity, control forcing simulations are contrasted with simulations where periods of TC activity in the atmospheric forcing data were replaced with climatology. During wet years, TC activity impacts productivity in 40-50% of the SE US domain and explains a regional GPP increase of 3-5 Mg C/m2 that is 9% of the warm season total. In dry years, 23-34% of the domain exhibits a smaller positive response that corresponds to 4 - 8% of the seasonal carbon uptake, depending on TC timing and trajectory.

3. Exhumation of the Panama basement complex and basins: Implications for the closure of the cCentral 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 supports 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. This article is protected by copyright. All rights reserved.

4. Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism

Understanding the evolution of extinct ocean basins through time and space demands the integration of surface kinematics and mantle dynamics. We explore the existence, origin and implications of a proposed oceanic slab burial ground under Greenland through a comparison of seismic tomography, slab sinking rates, regional plate reconstructions and satellite-derived gravity gradients. Our preferred interpretation stipulates that anomalous, fast seismic velocities at 1000-1600 km depth imaged in independent global tomographic models, coupled with gravity gradient perturbations, represent paleo-Arctic oceanic slabs that subducted in the Mesozoic. We suggest a novel connection between slab-related arc mantle and geochemical signatures in some of the tholeiitic and mildly alkaline magmas of the Cretaceous High Arctic Large Igneous Province in the Sverdrup Basin. However, continental crustal contributions are noted in these evolved basaltic rocks. The integration of independent, yet complementary, datasets provides insight into present-day mantle structure, magmatic events and relict oceans.

5. Does Amazonian deforestation cause global effects; can we be sure?

The Lightning and Sprites Observation (LSO) experiment was designed to test a new concept of nadir-viewing sprite measurement on board the International Space Station using spectral differentiation methods for lightning and sprite identification. It was composed of two calibrated cameras: one equipped with a narrowband filter at 763 nm to maximize the contrast between sprites and lightning, and the other to monitor lightning. The LSO was operated at night during 15 days from 2001 to 2004 during which 197 lightning flashes, several sprites, hundreds of gas flares, and tens of cities were analyzed. The main strength of this experiment was its high spatial resolution of about 400 m. The structural details of some lightning are thus observed highlighting complex systems. Some features such as the nonlinear increase of the lightning-illuminated cloud top area with the peak radiance and the radial decrease of the lightning flash radiance were quantified. The median area is 129 km2 with median minor and major axes of 12 and 16 km. Two methods of sprite identification are presented and applied to the most intense sprite events observed by LSO. The sprite diameter is 5 km and it is shifted of about 22 km from the center of the parent lightning. A ratio of 1.7% is deduced for lightning flashes between the radiances measured by both cameras. These observations should be useful for the preparation or the analysis of future space missions dedicated to nadir-viewing observations of sprites.

6. Orbital evidence for more widespread carbonate-bearing rocks on Mars

Carbonates are key minerals for understanding ancient Martian environments because they are indicators of potentially habitable, neutral-to-alkaline water and may be an important reservoir for paleoatmospheric CO2. Previous remote sensing studies have identified mostly Mg-rich carbonates, both in Martian dust and in a Late Noachian rock unit circumferential to the Isidis basin. Here we report evidence for older Fe- and/or Ca-rich carbonates exposed from the subsurface by impact craters and troughs. These carbonates are found in and around the Huygens basin northwest of Hellas, in western Noachis Terra between the Argyre basin and Valles Marineris, and in other isolated locations spread widely across the planet. In all cases they cooccur with or near phyllosilicates, and in Huygens basin specifically they occupy layered rocks exhumed from up to ~5 km depth. We discuss factors that might explain their observed regional distribution, arguments for why carbonates may be even more widespread in Noachian materials than presently appreciated and what could be gained by targeting these carbonates for further study with future orbital or landed missions to Mars.


XII.AUG Newsroom

1. ONE OIL FIELD A KEY CULPRIT IN GLOBAL ETHANE GAS INCREASE

WASHINGTON, DC — A single U.S. shale oil field is responsible for much of the past decade’s increase in global atmospheric levels of ethane, a gas that can damage air quality and impact climate, according to new study. The researchers found that the Bakken Formation, an oil and gas field in North Dakota and Montana, is emitting roughly 2 percent of the globe’s ethane. That’s about 230,000 metric tons (250,000 U.S. tons) per year.

2. A THIRD OF THE WORLD’S BIGGEST GROUNDWATER BASINS ARE IN DISTRESS

WASHINGTON, D.C. – Human consumption is rapidly draining about a third of its largest groundwater basins, despite having little to no accurate data about how much water remains in them, according to two new studies led by the University of California, Irvine, using data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites. The result is that significant segments of Earth’s population are consuming groundwater quickly without knowing when it might run out, the researchers conclude. The new findings have been accepted for publication in Water Resources Research, a journal of the American Geophysical Union, and appear online today.

3. UNHEALTHY OZONE DAYS COULD INCREASE BY MORE THAN A WEEK IN COMING DECADES

WASHINGTON, DC — If emission rates continue unchecked, regions of the United States could experience between three and nine additional days per year of unhealthy ozone levels by 2050, according to a new study.