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

发布时间:2016-12-16 10:12:17 点击次数:594

I. Science Policy

1. Easterling to Lead Geosciences at National Science Foundation

The agency's departing head of geosciences will introduce Easterling to the Earth sciences community as his successor tomorrow at the American Geophysical Union's Fall Meeting in San Francisco.

https://eos.org/articles/easterling-lead-geosciences-national-science-foundation

2. Obama Science Adviser Warns Against Retreats on Climate, Science

Holdren sees pitfalls for U.S. global leadership in withdrawing from climate accord and says that moving Earth observations out of NASA "is a terrible idea."

https://eos.org/articles/obama-science-adviser-warns-against-retreats-on-climate-science


II.Atmospheric Sciences

1. Reading Raindrops: Microphysics in Typhoon Matmo

Quantitative predictions about tropical storms require an understanding of even their smallest physical processes. A new study observes unusual microphysics in 2014's Typhoon Matmo.

https://eos.org/research-spotlights/reading-raindrops-microphysics-in-typhoon-matmo

2. Rise in Tornado Numbers per Outbreak May Not Be Tied to Warming

Scientists studying why previous research revealed a steadily increasing number of tornadoes in the United States per outbreak find an unexpected result.

https://eos.org/articles/rise-in-tornado-numbers-per-outbreak-may-not-be-tied-to-warming


III. Climate Change

1. Earth's Ground Heat Flux Should Not Be Overlooked

Scientists compare models of how much heat Earth's surface gives off and absorbs from the atmosphere.

https://eos.org/research-spotlights/earths-ground-heat-flux-should-not-be-overlooked


IV.Hydrology, Cryosphere & Earth Surface

1. Frontiers in Cryoseismology

Recent review provides timely and comprehensive resource for emerging field.

https://eos.org/editors-vox/frontiers-in-cryoseismology


V. Natural Hazards

1. American Geophysical Union Approves Renovation of Headquarters

The transformed headquarters, to be completed by December 2018, features a design geared toward communicating science to the community, sparking collaboration, and reducing environmental impact.

https://eos.org/agu-news/american-geophysical-union-approve


VI. Geophysical Research Letters

1. On the frequency of the 2015 monsoon season drought in the Indo-Gangetic Plain

The 2015 drought in the Indo-Gangetic Plain posed new challenges related to food and water security and affected the lives of millions. All-India monsoon rainfall in 2015 was the tenth driest year on record (1906–2015) with a deficit of 14.5%, and the Indo-Gangetic Plain witnessed a rainfall deficit of 25.8% (third rank event). Drought severity was amplified by deficits from the previous years in the Indo-Gangetic Plain and other parts of India. The Indo-Gangetic Plain faced a 2 year cumulative deficit of 51%, and the drought of 2014–2015 was unprecedented with a return period of 542 years. The GRACE data showed the occurrence of consecutive negative terrestrial water storage and groundwater anomalies in 2014 and 2015, mainly centered over the Indo-Gangetic Plain region. Notwithstanding uncertainty in future projections, the multiyear droughts in the same regions can pose challenges for water resources and agriculture.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071407/full

2. Statistical tests of simple earthquake cycle models

A central goal of observing and modeling the earthquake cycle is to forecast when a particular fault may generate an earthquake: a fault late in its earthquake cycle may be more likely to generate an earthquake than a fault early in its earthquake cycle. Models that can explain geodetic observations throughout the entire earthquake cycle may be required to gain a more complete understanding of relevant physics and phenomenology. Previous efforts to develop unified earthquake models for strike-slip faults have largely focused on explaining both preseismic and postseismic geodetic observations available across a few faults in California, Turkey, and Tibet. An alternative approach leverages the global distribution of geodetic and geologic slip rate estimates on strike-slip faults worldwide. Here we use the Kolmogorov-Smirnov test for similarity of distributions to infer, in a statistically rigorous manner, viscoelastic earthquake cycle models that are inconsistent with 15 sets of observations across major strike-slip faults. We reject a large subset of two-layer models incorporating Burgers rheologies at a significance level of α = 0.05 (those with long-term Maxwell viscosities ηM <~ 4.0 × 1019 Pa s and ηM >~ 4.6 × 1020 Pa s) but cannot reject models on the basis of transient Kelvin viscosity ηK. Finally, we examine the implications of these results for the predicted earthquake cycle timing of the 15 faults considered and compare these predictions to the geologic and historical record.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL070681/full

3. Lithospheric velocity model of Texas and implications for the Ouachita orogeny and the opening of the Gulf of Mexico

A 3-D shear wave velocity model of Texas has been developed from Rayleigh wave phase velocities by using ambient noise data recorded at the USArray stations. In the upper crust, the Ouachita front separates high velocity in the Laurentia to its west from low velocity in the east and south Texas basins. The Ouachita belt is characterized as a high-velocity zone with local maximums coinciding with known uplifts, which we interpret as accreted island arcs during the Ouachita orogeny. Our model evidences a strong Ouachita lithosphere that helped to buffer crust thinning from the Mesozoic rifting. A significantly low-velocity anomaly is present in southeast Texas in the lower crust and upper mantle. We associate this anomaly with a past asthenosphere upwelling that likely originated from the edge of the subducted slab during the Ouachita collision and was potentially responsible for the opening of the Gulf of Mexico.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071167/full

4. The influence of declining sea ice on shipping activity in the Canadian Arctic

Significant attention has focused on the potential for increased shipping activity driven by recently observed declines in Arctic sea ice cover. In this study, we describe the first coupled spatial analysis between shipping activity and sea ice using observations in the Canadian Arctic over the 1990–2015 period. Shipping activity is measured by using known ship locations enhanced with a least cost path algorithm to generate ship tracks and quantified by computing total distance traveled in kilometers. Statistically significant increases in shipping activity are observed in the Hudson Strait (150–500 km traveled yr−1), the Beaufort Sea (40–450 km traveled yr−1), Baffin Bay (50–350 km traveled yr−1), and regions in the southern route of the Northwest Passage (50–250 km travelled yr−1). Increases in shipping activity are significantly correlated with reductions in sea ice concentration (Kendall's tau up to −0.6) in regions of the Beaufort Sea, Western Parry Channel, Western Baffin Bay, and Foxe Basin. Changes in multiyear ice-dominant regions in the Canadian Arctic were found to be more influential on changes to shipping activity compared to seasonal sea ice regions.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071489/full

5. Decadal variation and trends in subsurface salinity from 1960 to 2012 in the northern South China Sea

Observations suggest that subsurface waters in the northern South China Sea exhibited substantial low-frequency variability, with a striking decadal change in the southern limit of the 34.6 practical salinity unit (psu) isohaline. Long-term freshening of the subsurface waters, started in 1960, was followed by salinification from 1975, and freshening occurred again from 1993 to 2012. The linear trends were −0.0076, 0.0100, and −0.0078 psu/yr, respectively. An analysis of the subsurface salinity budget reveals that the main underlying contributors to subsurface salinity are horizontal advection and vertical entrainment. In particular, advection driven by the Luzon Strait transport and vertical entrainment from the mixed layer are the key factors controlling variations on subsurface salinity. Diagnosis of the salinity budget further suggests that entrainment from the mixed layer played a more important role in the freshening periods than in the salinifying period.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071439/full

6. Geophysical imaging of shallow degassing in a Yellowstone hydrothermal system

The Yellowstone Plateau Volcanic Field, which hosts over 10,000 thermal features, is the world's largest active continental hydrothermal system, yet very little is known about the shallow “plumbing” system connecting hydrothermal reservoirs to surface features. Here we present the results of geophysical investigations of shallow hydrothermal degassing in Yellowstone. We measured electrical resistivity, compressional-wave velocity from refraction data, and shear wave velocity from surface-wave analysis to image shallow hydrothermal degassing to depths of 15–30 m. We find that resistivity helps identify fluid pathways and that Poisson's ratio shows good sensitivity to saturation variations, highlighting gas-saturated areas and the local water table. Porosity and saturation predicted from rock physics modeling provide critical insight to estimate the fluid phase separation depth and understand the structure of hydrothermal systems. Finally, our results show that Poisson's ratio can effectively discriminate gas- from water-saturated zones in hydrothermal systems.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071306/full

7. Semiautomatic mapping of permafrost in the Yukon Flats, Alaska

Thawing of permafrost due to global warming can have major impacts on hydrogeological processes, climate feedback, arctic ecology, and local environments. To understand these effects and processes, it is crucial to know the distribution of permafrost. In this study we exploit the fact that airborne electromagnetic (AEM) data are sensitive to the distribution of permafrost and demonstrate how the distribution of permafrost in the Yukon Flats, Alaska, is mapped in an efficient (semiautomatic) way, using a combination of supervised and unsupervised (machine) learning algorithms, i.e., Smart Interpretation and K-means clustering. Clustering is used to sort unfrozen and frozen regions, and Smart Interpretation is used to predict the depth of permafrost based on expert interpretations. This workflow allows, for the first time, a quantitative and objective approach to efficiently map permafrost based on large amounts of AEM data.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071334/full


VII.AGU News

1. AGU FALL MEETING: TODAY’S PRESS EVENTS; GENERAL SESSIONS; POTENTIALLY NEWSWORTHY SESSIONS

SAN FRANCISCO — Discover the latest Earth and space science news at the 49th annual AGU Fall Meeting this December, when about 24,000 attendees from around the globe are expected to assemble for the largest worldwide conference in the Earth and space sciences. This year, the meeting runs from Monday through Friday, Dec. 12-16, 2016 at the Moscone Center, 747 Howard St., San Francisco, California.

https://news.agu.org/press-release/agu-fall-meeting-todays-press-events-general-sessions-potentially-newsworthy-sessions/

2. AGU SETS A NEW BAR IN REDUCING CARBON FOOTPRINT WITH GROUNDBREAKING NET ZERO HEADQUARTERS RENOVATION TO BEGIN IN EARLY 2017

WASHINGTON, D.C. – The American Geophysical Union (AGU) today announced formal approval from its Board of Directors to undertake a $41.7 million complete renovation of its 62,000-square-foot headquarters building, located in the Dupont Circle neighborhood. AGU is aspiring to be the first organization in the District of Columbia to renovate an existing commercial building to achieve net zero goals.

https://news.agu.org/press-release/agu-sets-a-new-bar-in-reducing-carbon-footprint-with-groundbreaking-net-zero-headquarters-renovation-to-begin-in-early-2017/


VIII.AGU Blogs

1. AGU 16: live stream of the first landslide session on Wednesday

This week is AGU 16 – the Fall Meeting of the American Geophysical Union in San Francisco.  As usual it is an amazing, stimulating and slightly intimidating event.  This is science on a grand scale both in terms of the projects themselves and the number of attendees.  Last year the meeting attracted almost 24,000 attendees.  This year feels just as busy, perhaps more so.

http://blogs.agu.org/landslideblog/2016/12/12/agu-16-1/

2. The landslide distribution from the M=7.8 Gorkha Earthquake in Nepal

In the aftermath of the M=7.8 Gorkha Earthquake in Nepal last May, there has been a sudden and very welcome interest in landslides in that country.  A number of groups undertook mapping of the landslide distribution, and the publications are now starting to appear.  In a paper just published in Landslides (Martha et al. 2016), a group from the National Remote Sensing Centre and India have analysed an inventory of coseismic landslides triggered by the earthquake.  The results are interesting.  They have used a range of high resolution satellite instruments to generate a high quality landslide map.  India has some wonderful satellites that represent ideal tools for this purpose, although the team have also used a range of other instruments as well.  The upshot is probably the best landslide inventory published to date. http://blogs.agu.org/landslideblog/2016/12/09/m7-8-gorkha-earthquake/

3. Cold Blast Coming, but Milder Air for Late December

There is little doubt now that the coldest air of the season so far will reach the Great Lakes and Northeast U.S. by Thursday, and highs Thursday and Friday will not likely reach freezing as far south as Kentucky and Virginia! There will be some more lake effect snow as well as this dry,frigid air crosses the relatively warm waters of the Great Lakes. Just to be clear, the polar vortex will be over Hudson Bay and not the U.S., as some newspapers reported today (USA TODAY).

http://blogs.agu.org/wildwildscience/2016/12/12/cold-blast-coming-milder-air-late-december/

4. The Next Time You Really Mess Things Up- Remember This Story

He had been called onto the carpet as they say, and it was not just a middle manager. It was the top boss. He’d been expecting it for over 24 hours now, and as he walked downstairs he could not help but think that he should just call it a career, and chuck it all. He was at retirement age after all, so why not. 

http://blogs.agu.org/wildwildscience/2016/12/08/next-time-really-mess-things-remember-story/