AGU 期刊一周Research Spotlights (Sep 15~Sep 21, 2016)

发布时间:2016-9-23 8:25:33 点击次数:586

I. Atmospheric Sciences

1. Stuff My Reviewers Say

After going through a little more than a decade's worth of reviews, Noah Diffenbaugh shares insights about the peer review process and how reviewer feedback ultimately improved his publications.

2. Climate Change May Reduce Future Corn Supply

A suite of simulations run with a spectrum of starting conditions shows that climate change will reduce corn crop yield, although the degree of reductions varies widely.

II. Geology & Geophysics

1. AGU-Sponsored Workshop Targets Sexual Harassment in the Sciences

During the past 2 years, scientific societies and universities have faced increasing pressure to address a problem that has grown more visible.

2. All Earthquakes Are Created Equal

A study of the development of earthquakes shows that the size of the initial rupture does not determine its intensity or range later on.

3. Next President Must Name Science Leaders Fast, Report Urges

The report steers clear of providing guidance for how the next president should deal with specific science and technology issues, but it calls out climate change as a key policy area.

4. Four Position Statements Approved by AGU Board of Directors

The American Geophysical Union updated one position statement and reaffirmed three others as written.

III. Ocean Sciences

1. Obama Unveils First Marine National Monument in the Atlantic

The new designation follows the administration's expansion last month of a marine sanctuary in the Pacific Ocean near Hawaii into the world's largest protected ocean area.

IV. Climate Change

1. Probing the History of New Zealand's Orakei Maar

A team of scientists drilled into the bed within a northern New Zealand explosion crater lake to gain insights into volcanic hazards and past climates.

V. Space & Planets

1. Scientists Solve Charon's Red Mystery

Why are Charon's poles dusted with reddish material?

VI. Earth and Space Science

1. Ms. Callaghan’s Classroom: Sampling from the Sea

This is the latest in a series of dispatches from scientists and education officers aboard the National Science Foundation’s R/V Sikuliaq. Jil Callaghan is a 6th grade science teacher at Houck Middle School in Salem, Oregon. She is posting blogs for her students while aboard the Sikuliaq as part of a teacher at sea program through Oregon State University. Read more posts here. Track the Sikuliaq’s progress here.

2. Ms. Callaghan’s Classroom: Multi-coring

It was so cool to watch pieces of ice float by as we were working on deck! I’m standing next to the hose because we wash off the utensils (the metal sheet for cutting, the spatula used for scraping it into the bag, and the plastic ring) in between samples so that we don’t contaminate one layer with mud from another!

3.New study “reels in” data on Utah’s winter ozone problem

A deep sea fishing rod is probably not the first tool that comes to mind when thinking about how to study air pollution in a remote inland desert, but it’s the heart of a new system that has given scientists a minute-by-minute look at how quickly the sun can convert oil and gas emissions to harmful ground-level ozone.

4. Scientists investigate how atmospheric rivers may change as climate warms

A high-resolution climate model based at the National Center for Atmospheric Research (NCAR) is able to accurately capture the ribbons of moist air that sometimes escape the sodden tropics and flow toward the drier mid-latitudes, allowing scientists to investigate how “atmospheric rivers” may change as the climate warms.

VII. Geophysical Research Letters

1.Sea ice decline and 21st century trans-Arctic shipping routes

The observed decline in Arctic sea ice is projected to continue, opening shorter trade routes across the Arctic Ocean, with potentially global economic implications. Here we quantify, using Coupled Model Intercomparison Project Phase 5 global climate model simulations calibrated to remove spatial biases, how projected sea ice loss might increase opportunities for Arctic transit shipping. By midcentury for standard open water vessels, the frequency of navigable periods doubles, with routes across the central Arctic becoming available. A sea ice-ship speed relationship is used to show that European routes to Asia typically become 10 days faster via the Arctic than alternatives by midcentury, and 13 days faster by late century, while North American routes become 4 days faster. Future greenhouse gas emissions have a larger impact by late century; the shipping season reaching 4–8 months in Representative Concentration Pathway (RCP)8.5 double that of RCP2.6, both with substantial interannual variability. Moderately, ice-strengthened vessels likely enable Arctic transits for 10–12 months by late century.  

2. The effect of representing bromine from VSLS on the simulation and evolution of Antarctic ozone

We use the Goddard Earth Observing System Chemistry-Climate Model, a contributor to both the 2010 and 2014 World Meteorological Organization Ozone Assessment Reports, to show that inclusion of 5 parts per trillion (ppt) of stratospheric bromine (Bry) from very short lived substances (VSLS) is responsible for about a decade delay in ozone hole recovery. These results partially explain the significantly later recovery of Antarctic ozone noted in the 2014 report, as bromine from VSLS was not included in the 2010 Assessment. We show multiple lines of evidence that simulations that account for VSLS Bry are in better agreement with both total column BrO and the seasonal evolution of Antarctic ozone reported by the Ozone Monitoring Instrument on NASA's Aura satellite. In addition, the near-zero ozone levels observed in the deep Antarctic lower stratospheric polar vortex are only reproduced in a simulation that includes this Bry source from VSLS.

3. Subduction geometry beneath south central Alaska and its relationship to volcanism

The southern Alaskan margin captures a transition between compression and strike-slip-dominated deformation, accretion of the overthickened Yakutat terrane, termination of Aleutian arc magmatism, and the enigmatic Wrangell Volcanic Field. The extent of subduction and mantle structure below this region is uncertain, with important implications for volcanism. We present compressional and shear wave mantle velocity models below south central Alaska that leverage a new seismometer deployment to produce the most complete image of the subducting Pacific-Yakutat plate to date. We image a steeply dipping slab extending below central Alaska to >400 km depth, which abruptly terminates east of ~145°W. There is no significant slab anomaly beneath the nearby Wrangell volcanoes. A paucity of volcanism is observed above the subducting Yakutat terrane, but the slab structure below 150 km depth and Wadati-Benioff zone here are similar to those along the Aleutian-Alaska arc. Features of the mantle wedge or overlying lithosphere are thus responsible for the volcanic gap.

4. Sensitivity of precipitation extremes to radiative forcing of greenhouse gases and aerosols

Greenhouse gases (GHGs) and aerosols are the two most important anthropogenic forcing agents in the 21st century. The expected declines of anthropogenic aerosols in the 21st century from present-day levels would cause an additional warming of the Earth's climate system, which would aggravate the climate extremes caused by GHG warming. We examine the increased rate of precipitation extremes with global mean surface warming in the 21st century caused by anthropogenic GHGs and aerosols, using an Earth system model ensemble simulation. Similar to mean precipitation, the increased rate of precipitation extremes caused by aerosol forcing is significantly larger than that caused by GHG forcing. The aerosol forcing in the coming decades can play a critical role in inducing change in precipitation extremes if a lower GHG emission pathway is adopted. Our results have implications for policy-making on climate adaptation to extreme precipitation events.

5. Radar Imaging of Intense Nonlinear Ekman Divergence

In general, given an oceanic thermal front, there is a strong positive correlation between sea surface temperature (SST) gradients and surface winds, and the marine atmospheric boundary layer is unstable over the warm side of the oceanic thermal front. The Gulf Stream is a notable example of an oceanic thermal front, and its warm side is often detected as enhanced backscatter in synthetic aperture radar (SAR) images. However, in some “anomalous” SAR images, low backscatter is sometimes observed on the warm side of the front, which seems inconsistent. Therefore, we propose a mechanism to interpret the generation of the low backscatter, based on interactions between ocean surface wind waves and intense nonlinear Ekman divergence. This mechanism is verified by showing that patterns in an observed anomalous SAR image are in good agreement with those in the simulated radar signature. In addition, this methodology and analysis demonstrate that SAR is potentially important for detecting and diagnosing small scale air-sea interactions and upper ocean dynamics with strong vertical transports induced by submesoscale processes.

6. Trends of perchlorate in Antarctic snow: Implications for atmospheric production and preservation in snow

Perchlorate concentration ranges from a few to a few hundred ng kg−1 in surface and shallow-depth snow at three Antarctic locations (South Pole, Dome A, and central West Antarctica), with significant spatial variations dependent on snow accumulation rate and/or atmospheric production rate. An obvious trend of increasing perchlorate since the 1970s is seen in South Pole snow. The trend is possibly the result of stratospheric chlorine levels elevated by anthropogenic chlorine emissions; this is supported by the timing of a similar trend at Dome A. Alternatively, the trend may stem from postdepositional loss of snowpack perchlorate or a combination of both. The possible impact of stratospheric chlorine is consistent with evidence of perchlorate production in the stratosphere. Additionally, perchlorate concentration appears to be directly affected by the springtime Antarctic ozone hole. Therefore, perchlorate variations in Antarctic snow are likely linked to stratospheric chemistry and ozone over the Antarctic.

7. Dipolarization in the inner magnetosphere during a geomagnetic storm on 7 October 2015

A dipolarization event was observed by the Magnetospheric Multiscale (MMS) spacecraft at L = 3.8 and 19.8 magnetic local time starting at ~23:42:36 UT on 7 October 2015. The magnetic and electric fields showed initially coherent variations between the spacecraft. The sunward convection turned tailward after the dipolarization. The observation is interpreted in terms of the pressure balance or the momentum equation. This was followed by a region traversed where the fields were irregular. The scale length was of the order of the ion gyroradius, suggesting the kinetic nature of the fluctuations. Combination of the multi-instrument, multispacecraft data reveals a more detailed picture of the dipolarization event in the inner magnetosphere. Conjunction ionosphere-plasmasphere observations from DMSP, two-dimensional GPS total electron content, the Millstone Hill midlatitude incoherent scatter radar, and AMPERE measurements imply that MMS observations are located on the poleward edge of the ionospheric trough where Region 2 field-aligned currents flow.

8. Rain evaporation and moist patches in tropical boundary layers

Moist patches are areas in the subcloud layer characterized by a positive water vapor anomaly compared to the environment and are considered important in triggering new convective cells. A correct understanding of the origin of the water vapor in these patches is, thus, essential to improving existing convective parameterizations. Recent studies have addressed this problem and have shown that contrary to what was previously thought, the main source of water vapor in moist patches are surface latent heat fluxes, instead of rain evaporation. This manuscript offers a different perspective to the topic, focusing on the origin only of the water vapor that makes moist patches anomalously moist when compared to the environment. It is found that near the surface, rain evaporation contributes half as much as latent heat fluxes, implying that a parameterization of the thermodynamic forcing should be more sensitive to environmental variables, like relative humidity, than recently suggested.

9. High-resolution seismic tomography of the 2015 Mw7.8 Gorkha earthquake, Nepal: Evidence for the crustal tearing of the Himalayan rift

The Mw7.8 Gorkha earthquake struck Nepal and ruptured the boundary between the Indian and Eurasian plates. We conducted 2-D Pg wave tomography to clarify the seismogenic structure and try to understand causal mechanisms for this large earthquake, using the aftershock data recorded by 15 broadband seismic stations located near the China-Nepal border. Our high-resolution results show that coseismic slip area of the main shock is consistent with the high P wave velocity anomaly, and the region of maximum slip has a larger area with higher velocity than the region of initial slip, possibly resulting in the dominant low-frequency radiation of energy observed after the dominant high-frequency radiation of energy in the source rupture process. The boundary between these regions of contrasting high and low seismic velocity anomalies suggests a potential crustal tearing at the southern end of the Tangra Yum Co Rift, possibly resulting from different thrust speeds in the Greater Himalaya.



WASHINGTON, DC— Earth and space sciences play an increasingly important role in the technologies and advancements that have broad implications for society, from public health and safety to economic development. The American Geophysical Union (AGU) today reaffirmed its position statement, “AGU Supports Free and Open Communication of Scientific Findings,” acknowledging that scientists should be able to present their findings freely and “without censorship, intimidation, or political interference.” It also charges scientists with the responsibility to “portray their results, and the results of others, objectively, professionally, and without sensationalizing or politicizing the associated impacts.”


WASHINGTON, DC—Federal funding provides stability and continuity that’s essential to longer-term missions and programs in Earth and space science that lead to development and innovation. The American Geophysical Union (AGU) today reaffirmed its position statement, “The U.S. Government has a Critical Role in Supporting Basic Research in the Earth and Space Sciences,” noting the importance of federal funding on scientific research.


WASHINGTON, DC—The American Geophysical Union (AGU) today released a revision of its position statement on K-12 science education, “Earth and Space Sciences Should be Taught in K-12 Education.” AGU also announced that it has reaffirmed its position statement on teaching Earth history and evolution, “The Scientific Theories of Biological Evolution and History of the Earth Should be Central Elements of Science Education.”


WASHINGTON, DC — A great algae bloom at the bottom of the world is teaching scientists more about how an iconic symbol of the United Kingdom came to be.

The White Cliffs of Dover span England’s southeastern coastline for 16 kilometers (10 miles) and reach as tall as 110 meters (350 feet) high. Facing the narrowest part of the English Channel, the cliffs have come to symbolize England since the time of Julius Caesar, often the first and last view travelers have of the country by sea.