AGU 期刊一周Research Spotlights (Aug 17~Aug 24, 2016)

发布时间:2016-8-25 16:33:13 点击次数:713

I. Atmospheric Sciences

1. How Sea Surface Temperatures Affect an Atmospheric Phenomenon

New research sheds light on the complex interplay between the atmosphere and the ocean and how both affect the Madden-Julian Oscillation.

2. Scientists Map Temperature and Density in Earth's Exosphere

Data from multiple orbiters give a clearer picture of how density and temperature interact and what that could mean for future satellite missions.

II. Geology & Geophysics

1. Deciphering the Bay of Bengal's Tectonic Origins

New magnetic and gravity data suggest that the boundary between continental and oceanic crust lies beneath northern Bangladesh, along the line of an Early Cretaceous spreading center.

2. First Results from NASA's Magnetospheric Multiscale Mission

Understanding magnetic reconnection is important in the context of Sun-Earth Connection, because of the resulting exchange of mass and energy, and the large amount of energy involved.

III.Hydrology, Cryosphere & Earth Surface

1. New Flood Model Offers National Streamflow Coverage

The model, released by the National Weather Service, will provide neighborhood-level flood forecasting.

IV.Ocean Sciences

1. Elephant Seals' Dives Show Slowdown in Ocean Circulation

Data from instruments mounted on elephant seals reveal that melting ice flushes fresh water into the Southern Ocean, suppressing an important arm of the global ocean circulation belt.

V. Climate Change

1. Headwater Streams May Export More Carbon Than Previously Thought

New research sheds light on the streams that carry carbon away from peatlands with the hope that the data will better inform climate models.

VI. Science Policy & Funding

1. U.S. Parks to Make Adaptation to "Continuous Change" a Top Goal

The U.S. National Park Service science adviser calls climate change an "overarching" challenge facing the national parks.

VII. Space & Planets

1. NASA's New Asteroid Sampler Will Illuminate Solar System's History

In 7 years, scientists hope to directly analyze materials from the asteroid Bennu, an object that may reveal what conditions were like in the solar system 4.5 billion years ago.

2. Forecasting Space Weather Like Earth Weather

Researchers find that as with terrestrial weather, ensemble forecasting—which uses several different models simultaneously—is the best way to produce accurate and precise forecasts of space weather.

VIII. Earth and Space Science

1. Pacific sea level predicts global temperature changes

The amount of sea level rise in the Pacific Ocean can be used to estimate future global surface temperatures, according to a new study.

Based on the Pacific Ocean’s sea level in 2015, the study estimates by the end of 2016 the world’s average surface temperature will increase up to 0.28 degrees Celsius (0.5 degrees Fahrenheit) more than in 2014.

IX. Geophysical Research Letters

1. Stability of B2-type FeS at Earth's inner core pressures

Using density functional theory, we investigated how substituting sulfur atoms for iron atoms affects the structure and energy of the body centered cubic and hexagonal close-packed iron phases at 350 GPa and at 0 K. We conclude that formation of random (Fe,S) solid solutions is energetically favorable in all intermediate compositions, although the random low-symmetry substitutions cause structural distortion. The (Fe,S) solid solution is nearly as favorable as the mechanical mixture of Fe-hcp and FeS-B2. This finding, in combination with dynamical stability, defines the B2 structure as a strong candidate for the sulfur-bearing phase of the Earth's inner core.

2.Ground detection of terrestrial gamma ray flashes from distant radio signals

Terrestrial gamma ray flashes (TGFs) are brief bursts of energetic gammy-ray photons generated during thunderstorms, which have been detected almost exclusively by satellite-based instruments. Here we present three lines of evidence which includes the three out of three simultaneously observed pairs, the same occurrence contexts, and the consistent estimated occurrence rate, which indicate a direct relationship between a subset of TGFs and a class of energetic radio signal easily detectable by ground-based sensors. This connection indicates that these gamma ray and radio emissions are two views of the same phenomenon and further enable detection of these TGFs from ground distant radio signals alone. Besides dramatically increasing the detection rate of TGFs, this ground detection approach can identify TGFs in continental and coastal areas that are at latitudes too high for present TGF-detecting satellites and will provide more insights into the mechanism of TGF production.

3.Changes in surface aerosol extinction trends over China during 1980–2013 inferred from quality-controlled visibility data

Pollution in China has been attracting extensive attention both globally and regionally, especially due to the perceptually worsening “smog” condition in recent years. We use routine visibility measurements from 1980 to 2013 at 272 World Meteorological Organization stations in China to assess the temporal changes in the magnitude and the sign of pollution trends. A strict and comprehensive quality control procedure is enforced by considering several issues not typically addressed in previous studies. Two methods are used to independently estimate the trend and its significance level. Results show that, in general, a strong increase in aerosol extinction coefficient over the majority of China is observed in the 1980s, followed by a moderate decrease in the 1990s, another increase in the 2000s, and a shift to decrease since around 2006 for some regions. Seasonally, winter and fall trends appear to be the strongest, while summer has the lowest trend.

4. An important missing source of atmospheric carbonyl sulfide: Domestic coal combustion

Carbonyl sulfide (COS), carbon monoxide (CO), and sulfur dioxide (SO2) emissions generated from prevailing domestic coal stoves fueled with raw bituminous coal were studied under alternation cycles of flaming and smoldering combustion. The measurements in the laboratory and the farmer's house indicated that COS and CO emissions mainly occurred under the condition of flame extinguishment after coal loading, whereas SO2 emissions were mainly generated through combustion with flame. The COS emission factors for the domestic stoves in the laboratory and the farmer's house were recorded as 0.57 ± 0.10 g COS kg−1 and 1.43 ± 0.32 g COS kg−1, being approximately a factor of 50 and 125 greater than that generated from coal power plants, respectively. Based on the COS emission factors measured in this study, COS emission from only domestic coal combustion in China would be at least 30.5 ± 5.6 Gg S yr−1 which was 1 magnitude greater than the current COS estimation from the total coal combustion in China.

5. Comparison of methods: Attributing the 2014 record European temperatures to human influences

The year 2014 broke the record for the warmest yearly average temperature in Europe. Attributing how much this was due to anthropogenic climate change and how much it was due to natural variability is a challenging question but one that is important to address. In this study, we compare four event attribution methods. We look at the risk ratio (RR) associated with anthropogenic climate change for this event, over the whole European region, as well as its spatial distribution. Each method shows a very strong anthropogenic influence on the event over Europe. However, the magnitude of the RR strongly depends on the definition of the event and the method used. Across Europe, attribution over larger regions tended to give greater RR values. This highlights a major source of sensitivity in attribution statements and the need to define the event to analyze on a case-by-case basis.

6. Direct observation of the thermal demagnetization of magnetic vortex structures in nonideal magnetite recorders

The thermal demagnetization of pseudo-single-domain (PSD) magnetite (Fe3O4) particles, which govern the magnetic signal in many igneous rocks, is examined using off-axis electron holography. Visualization of a vortex structure held by an individual Fe3O4 particle (~250 nm in diameter) during in situ heating is achieved through the construction and examination of magnetic-induction maps. Stepwise demagnetization of the remanence-induced Fe3O4 particle upon heating to above the Curie temperature, performed in a similar fashion to bulk thermal demagnetization measurements, revealed that its vortex state remains stable under heating close to its unblocking temperature and is recovered upon cooling with the same or reversed vorticity. Hence, the PSD Fe3O4 particle exhibits thermomagnetic behavior comparable to a single-domain carrier, and thus, vortex states are considered reliable magnetic recorders for paleomagnetic investigations.

7. Deepwater circulation variation in the South China Sea since the Last Glacial Maximum

Deepwater circulation plays a central role in global climate. Compared with the Atlantic, the Pacific deepwater circulation's history remains unclear. The Luzon overflow, a branch of the North Pacific deep water, determines the ventilation rate of the South China Sea (SCS) basin. Sedimentary magnetic properties in the SCS reflect millennial-scale fluctuations in deep current intensity and orientation. The data suggest a slightly stronger current at the Last Glacial Maximum compared to the Holocene. But, the most striking increase in deep current occurred during Heinrich stadial 1 (H1) and to a lesser extent during the Younger Dryas (YD). Results of a transient deglacial experiment suggest that the northeastern current strengthening at the entrance of the SCS during H1 and the YD, times of weak North Atlantic Deep Water formation, could be linked to enhanced formation of North Pacific Deep Water.