AGU 期刊一周Research Spotlights (Sep 8~Sep 14, 2016)

发布时间:2016-9-16 8:27:50 点击次数:645

I. Atmospheric Sciences

1. Atmospheric Chemists Should Tackle Risks to Society, Report Says

Protecting public health and the health of the climate and ecosystems warrants more focus from this scientific field, according to the report.

II. Geology & Geophysics

1. New Technique Tracks Rock Deformation at a Micrometric Scale

Scientists explore microscopic marble deformation at high pressures and temperatures using a novel experimental technique that could improve our understanding of rock deformation in nature.

III.Hydrology, Cryosphere & Earth Surface

1. How Vague Historical Writings Help Scientists Predict Floods

By including imprecise historical written records in their calculations, researchers were able to decrease uncertainty in estimations of future flood frequency.

2. Melting Ice Could Reveal Toxic Cold War Era Waste in Greenland

Unforeseen political disputes could arise as countries assess who's responsible for the cleanup of the Cold War relics.


IV. Climate Change

1. Volcanic Java and Climate Change

An account of a geophysicist's recent trip to Indonesia wouldn't be complete without intrigue and elucidations about what Java, climate change, and Butch Cassidy all have in common.

2. Here Comes the Anthropocene

Two recent papers in Earth's Future discuss the addition of a new epoch to the geological timescale.

3. Air-Sea Interactions Influence Major Southern Wind Belt

Ocean and atmospheric data provide evidence for how sea surface temperatures affect the Southern Annular Mode.

V. Space & Planets

1. A Flip-Flopping Climate Could Explain Mars's Watery Past

A new hypothesis might reconcile two opposing theories that have tried to explain Mars's mysterious history for more than 40 years.

2. Scientists Get First Glimpse of Solar Wind as It Forms

Using computer-processed images from Sun-watching satellites, scientists observed solar wind emerging from the Sun's corona.

VI. Earth and Space Science

1. Sikuliaq week 1 recap: Through the ice

Today marks one full week at sea. We’ve gone through the Bering Strait and Chukchi Sea into the Beaufort Sea, where we worked our way into the Beaufort Basin. Then we turned southwest and are now back in the northeastern part of the Chukchi Sea. We’ve recovered and replaced a mooring; steamed along the DBO 6 line, taking 18 CTD casts along the way; continued to collect surface underway measurements; prepped for the deployment of the super sucker sled, multi-corer, and glider (each very cool pieces of equipment that warrant future explanation); and most excitingly (at least for this unseasoned Arctic visitor who still gets giddy at the idea of being on a ship), we entered ice.

2. Fungi make steep slopes more stable

Fungi are fantastic. They give us beer, bread and cheese. And if those delicious reasons aren’t sufficient, then here’s another: a new study suggests some fungi can help prevent shallow landslides and surface erosion.

3.Walking the line: DBO 6

Eager scientists peak through the small circular window of the water-tight door between the wet lab and the Baltic room. When the all-clear is given and the door opened, they clamber en masse toward the CTD. Rachel delegates tasks with urgency – Debbie, Jenna, Mary-Kate, Katie, and Brianna go to their assigned stations. They squat next to nozzles and fill bottles with water. This water came from the cold, dark depths of the Beaufort Basin. It was collected in 10L Niskin bottles (no one could remember exactly who Niskin was. Onboard Wikipedia says Shale Niksin first came up with the idea in 1966) – essentially 4ft long tubes with caps at both ends. These are “fired” – or told to close to gather water – when an operator in the computer room of the ship clicks a button on a screen.

4. Into the Atlin wild

Where we are—Atlin, British Columbia—there are few trails and more than a few gaps in knowledge about the area’s geology. Our research team uses a geological map last updated in the early 2000s to navigate the terrain and find specific outcrops along the Atlin ophiolite where there are boundaries, or reaction fronts, places where the original rock was at some point altered by hot carbon dioxide-bearing fluids within the Earth’s crust.


VII. Geophysical Research Letters

1.Ice-flow reorganization in West Antarctica 2.5 kyr ago dated using radar-derived englacial flow velocities

We date a recent ice-flow reorganization of an ice divide in the Weddell Sea Sector, West Antarctica, using a novel combination of inverse methods and ice-penetrating radars. We invert for two-dimensional ice flow within an ice divide from data collected with a phase-sensitive ice-penetrating radar while accounting for the effect of firn on radar propagation and ice flow. By comparing isochronal layers simulated using radar-derived flow velocities with internal layers observed with an impulse radar, we show that the divide's internal structure is not in a steady state but underwent a disturbance, potentially implying a regional ice-flow reorganization, 2.5 (1.8–2.9) kyr B.P. Our data are consistent with slow ice flow in this location before the reorganization and the ice divide subsequently remaining stationary. These findings increase our knowledge of the glacial history of a region that lacks dated constraints on late-Holocene ice-sheet retreat and provides a key target for models that reconstruct and predict ice-sheet behavior.

2. Altitudinal dependence of meteor radio afterglows measured via optical counterparts

Utilizing the all-sky imaging capabilities of the first station of the Long Wavelength Array along with a host of all-sky optical cameras, we have now observed 44 optical meteor counterparts to radio afterglows. Combining these observations, we have determined the geographic positions of all 44 afterglows. Comparing the number of radio detections as a function of altitude above sea level to the number of expected bright meteors, we find a strong altitudinal dependence characterized by a cutoff below ~90 km, below which no radio emission occurs, despite the fact that many of the observed optical meteors penetrated well below this altitude. This cutoff suggests that wave damping from electron collisions is an important factor for the evolution of radio afterglows. This finding agrees with the hypothesis that the emission is the result of electron plasma wave emission.

3. Deep nightside photoelectron observations by MAVEN SWEA: Implications for Martian northern hemispheric magnetic topology and nightside ionosphere source

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission samples the Mars ionosphere down to altitudes of ~150 km over a wide range of local times and solar zenith angles. On 5 January 2015 (Orbit 520) when the spacecraft was in darkness at high northern latitudes (solar zenith angle, SZA >120°; latitude >60°), the Solar Wind Electron Analyzer (SWEA) instrument observed photoelectrons at altitudes below 200 km. Such observations imply the presence of closed crustal magnetic field loops that cross the terminator and extend thousands of kilometers to the deep nightside. This occurs over the weak northern crustal magnetic source regions, where the magnetic field has been thought to be dominated by draped interplanetary magnetic fields (IMF). Such a day-night magnetic connectivity also provides a source of plasma and energy to the deep nightside. Simulations with the SuperThermal Electron Transport (STET) model show that photoelectron fluxes measured by SWEA precipitating onto the nightside atmosphere provide a source of ionization that can account for the  density measured by the Suprathermal and Thermal Ion Composition (STATIC) instrument below 200 km. This finding indicates another channel for Martian energy redistribution to the deep nightside and consequently localized ionosphere patches and potentially aurora.

4. Role of mechanical erosion in controlling the effusion rate of basaltic eruptions

In many basaltic eruptions, observations show that the effusion rate of magma has a typical dependence on time: the effusion rate curves show first a period of increasing and later a decreasing phase by a maximum value. We present a model to explain this behavior by the emptying of a magma reservoir through a vertical cylindrical conduit with elliptical cross section, coupled with the its widening due to mechanical erosion, produced by the magma flow. The model can reproduce the observed dependence on time of effusion rate in basaltic eruptions. Eruption duration and the maximum value of effusion rate depend on the size of magma chamber, on lava viscosity and strongly on erosion rate per unit traction.

5. Internal tide oceanic tomography

A concept of internal tide oceanic tomography (ITOT) is proposed to monitor ocean warming on a global scale. ITOT is similar to acoustic tomography, but that work waves are internal tides. ITOT detects ocean temperature changes by precisely measuring travel time changes of long-range propagating internal tides. The underlying principle is that upper ocean warming strengthens ocean stratification and thus increases the propagation speed of internal tides. This concept is inspired by recent advances in observing internal tides by satellite altimetry. In particular, a plane wave fit method can separately resolve multiple internal tidal waves and thus accurately determines the phase of each wave. Two examples are presented to demonstrate the feasibility and usefulness of ITOT. In the eastern tropical Pacific, the yearly time series of travel time changes of the M2 internal tide is closely correlated with the El Niño–Southern Oscillation index. In the North Atlantic, significant interannual variations and bidecadal trends are observed and consistent with the changes in ocean heat content measured by Argo floats. ITOT offers a long-term, cost-effective, environmentally friendly technique for monitoring global ocean warming. Future work is needed to quantify the accuracy of this technique.

6. Confidence intervals for time averages in the presence of long-range correlations, a case study on Earth surface temperature anomalies

Time averages, a standard tool in the analysis of environmental data, suffer severely from long-range correlations. The sample size needed to obtain a desired small confidence interval can be dramatically larger than for uncorrelated data. We present quantitative results for short- and long-range correlated Gaussian stochastic processes. Using these, we calculate confidence intervals for time averages of surface temperature measurements. Temperature time series are well known to be long-range correlated with Hurst exponents larger than 1/2. Multidecadal time averages are routinely used in the study of climate change. Our analysis shows that uncertainties of such averages are as large as for a single year of uncorrelated data.

7. A local index of Maritime Continent intraseasonal variability based on rain rates over the land and sea

A local index for describing intraseasonal variability over the Maritime Continent is developed. The index is based on the ratio of area-averaged rain rate over the land to that over the sea. It takes advantage of the fact that the main convective envelope of intraseasonal variability events tends to modulate the diurnal precipitation cycle over the land over the entire Maritime Continent. Lagged analysis is used to create composite intraseasonal variability events, where “day 0” is chosen according to when the normalized rain rate over the sea becomes greater than that over the land. The index identifies intraseasonal variability events associated with the Madden Julian Oscillation as well as equatorial Kelvin waves and westward propagating equatorial Rossby waves. The results suggest a similar local impact of all such events in suppressing the rain rate over land relative to that over the sea when the main convective envelope approaches.

8. Understanding Pacific Ocean influence on interannual precipitation variability in the Sahel

Moisture budget decomposition is performed for the Sahel (10°–20°N and 20°W–40°E) in order to understand the processes that govern regional hydroclimate variability on interannual time scales and frame them in the context of their primary ocean driver. Results show that warm conditions in the Eastern Tropical Pacific remotely force anomalously dry conditions primarily through affecting the low-troposphere mass divergence field. This behavior is related to increased subsidence over the tropical Atlantic and into the Sahel and an anomalous westward flow of moisture from the continent, both resulting in a coherent drying pattern. Understanding the physical processes relating remote sea surface temperature anomalies to atmospheric circulation changes and the resulting complex local convergence patterns is important for advancing seasonal prediction of precipitation over West Africa.



WASHINGTON, DC – More than 60 leaders in science from academia, government agencies, and professional societies came together recently to address the challenge of sexual and gender-based harassment on campus, in the field, and at scientific meetings. The American Geophysical Union convened the workshop titled, “Sexual Harassment in the Sciences: A Call to Respond,” which was co-sponsored by the American Association for the Advancement of Science, American Chemical Society, American Geosciences Institute, Association for Women Geoscientists, and Earth Science Women’s Network.