AGU 期刊一周Research Spotlights (Aug 24~Aug 31, 2016)

发布时间:2016-9-2 9:10:31 点击次数:858

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I. Atmospheric Sciences

1. Incorporating 3-D Cloud Effects into Weather and Climate Models

Researchers explain how a new radiative scheme can be incorporated into global weather and climate models to better capture the effect of clouds on climate.


II. Geology & Geophysics

1. Stamps Celebrate National Parks on Agency's Centennial

Striking images showcase iconic and lesser known U.S. national parks, seashores, and historic sites.


III.Hydrology, Cryosphere & Earth Surface

1. Six Snapshots of Geoscience Research from National Parks

As the National Park Service celebrates its 100th anniversary, we celebrate ongoing Earth and atmospheric research made possible by conservation efforts.


IV. Climate Change

1. Collaboration to Enhance Coastal Resilience

Integrating models from the social and natural sciences could generate a more holistic approach to climate change response planning in coastal communities.


V. Space & Planets

1. Elevating Planetary Science in Africa

Although planetary sciences may be perceived as long-term fundamental research with little direct and immediate benefit for populations, expanding planetary science programs can have many benefits.

2. Juno Makes Closest Ever Orbit of Jupiter

NASA plans to release more pictures soon, including views of the planet's atmosphere and its north and south poles, all in unprecedented detail.

3. How Do Gullies Form on Mars?

New orbiter data support an important role for seasonal frost—not liquid water—in the formation of Martian gullies.

4. Closest Ever Terrestrial Exoplanet Found, Habitability Debated

Researchers are excited about a new, potentially habitable exoplanet orbiting our closest stellar neighbor, Proxima Centauri.


VI. Earth and Space Science

1. The demise of the Maya civilization: water shortage can destroy cultures

Something really drastic must have happened to the ancient Maya at the end of the Classic Period in the 9th Century. Within a short period of time, this advanced civilization in Central America went from flourishing to collapsing – the population dwindling rapidly and monumental stone structures, like the ones built at Yucatán, were no longer being constructed. The reason for this demise remains the subject of debate even today. Now, researchers at the Vienna University of Technology (TU Wien) may have found the explanation: the irrigation technology that served the Mayans well during periods of drought may have actually made their society more vulnerable to major catastrophes, according to a new study published in Water Resources Research, a journal of the American Geophysical Union.

2. Wildfire smoke hacks clouds

Plumes of wildfire smoke envelop and alter clouds, potentially affecting local weather, according to new research based on serendipitous airborne measurements of clouds in smoke from Canadian fires. The new data confirms clouds embedded in smoke are likely to warm up the atmosphere around clouds, causing the clouds to dissipate faster.

3. New study identifies next faults to fail along California-Nevada border

A handful of faults lining the border of California and Nevada may be near the point of rupture, according to a new study assessing earthquakes in the region as far back as 1,400 years ago. Scientists report that earthquakes in a fault network east of the Sierra Nevada Mountains are not random, but are likely triggered from stress bestowed by past earthquakes. This same type of stress has built up in six faults near Death Valley, California, and Reno, Nevada, according to the new research.

4. Hello from Sikuliaq 2016: The Dynamic Arctic

Welcome to our Dynamic Arctic blog! This will be our information hub to keep you up-to-date as we embark on a research cruise through the Beaufort and Chukchi Seas. Our journey will begin in Nome, Alaska on about August 31 and finish around October 1, 2016.

5. Less ice, more food?

Two teams will do separate but related scientific work aboard the Sikuliaq over the next month. The following is an overview of their proposed research and what they expect to find:

Dr. Laurie Juranek leads a team of 11 from Oregon State University’s College of Earth, Ocean, and Atmospheric Sciences (CEOAS). Juranek and her colleagues are investigating how Arctic sea ice change is affecting the region’s chemistry and ecology.


VII. Geophysical Research Letters

1. Overestimating climate warming-induced methane gas escape from the seafloor by neglecting multiphase flow dynamics

Continental margins host large quantities of methane stored partly as hydrates in sediments. Release of methane through hydrate dissociation is implicated as a possible feedback mechanism to climate change. Large-scale estimates of future warming-induced methane release are commonly based on a hydrate stability approach that omits dynamic processes. Here we use the multiphase flow model TOUGH + hydrate (T + H) to quantitatively investigate how dynamic processes affect dissociation rates and methane release. The simulations involve shallow, 20–100 m thick hydrate deposits, forced by a bottom water temperature increase of 0.03°C yr−1 over 100 years. We show that on a centennial time scale, the hydrate stability approach can overestimate gas escape quantities by orders of magnitude. Our results indicate a time lag of > 40 years between the onset of warming and gas escape, meaning that recent climate warming may soon be manifested as widespread gas seepages along the world's continental margins.

2. On the relationship between atmospheric rivers and high sea water levels along the U.S. West Coast

Atmospheric rivers (ARs) are narrow filaments of high moisture transported within extratropical systems. The role of ARs as drivers of heavy precipitation and flooding has been well documented; however, little is known about the contribution of landfalling ARs to high sea water levels, which are the leading cause of coastal flooding. Here we assess the relationship between ARs and extreme hourly sea level time series at 15 tide gauges along the continental U.S. Pacific Coast. Results indicate that ARs are associated with 15% to 50% of the annual sea level maxima before (and 22% to 65% after) removing tidal oscillations. Strong associations are also found when using other high sea level metrics. From a climatic perspective, the frequency of extreme hourly sea levels tends to increase during the negative phase of the Arctic Oscillation and during the positive phases of the Pacific-North American pattern and the El Niño–Southern Oscillation.

3. Trains of large Kelvin-Helmholtz billows observed in the Kuroshio above a seamount

Trains of large Kelvin-Helmholtz (KH) billows within the Kuroshio current at ~230 m depth off southeastern Taiwan and above a seamount were observed by shipboard instruments. The trains of large KH billows were present in a strong shear band along the 0.55 m s−1 isotach within the Kuroshio core; they are presumably produced by flow interactions with the rapidly changing topography. Each individual billow, resembling a cat's eye, had a horizontal length scale of 200 m, a vertical scale of 100 m, and a timescale of 7 min, near the local buoyancy frequency. Overturns were observed frequently in the billow cores and the upper eyelids. The turbulent kinetic energy dissipation rates estimated using the Thorpe scale had an average value of O(10−4) W kg−1 and a maximum value of O(10−3) W kg−1. The turbulence mixing induced by the KH billows may exchange Kuroshio water with the surrounding water masses.

4. On the role of extratropical air-sea interaction in the persistence of the Southern Annular Mode

Using the daily atmosphere and ocean reanalysis data, this study highlights the role of extratropical air-sea interaction in the variability of the Southern Annular Mode (SAM). Our analysis shows that the SAM-induced meridional dipolar sea surface temperature (SST) anomalies, through surface heat fluxes, can maintain persistent lower tropospheric temperature anomalies, which further results in anomalous eddy momentum forcing enhancing the persistence of the SAM. With the Finite Amplitude Wave Activity diagnosis, we illustrate that response of the eddy momentum forcing to SST anomalies can be attributed to changes in both baroclinic processes as baroclinic eddy generation and barotropic processes as wave breaking thus resultant diffusive eddy mixing, with the former confined at high latitudes and the latter strongest at midlatitudes. Spectral analysis further suggests that the above air-sea interactions are important for bimonthly and longer time scale SAM variations. The dipolar SST pattern may be an indicator for predicting subseasonal and interseasonal variabilities of the SAM.

5. Characteristics on fault coupling along the Solomon megathrust based on GPS observations from 2011 to 2014

The Solomon megathrust along the western Solomon arc generated two megathrust earthquakes in the past decade (Mw 8.1 in 2007 and Mw 7.1 in 2010). To investigate the interseismic deformation and inferred coupling on the megathrust, we deployed the first continuous GPS network in the Western Solomon Islands. Our 2011–2014 GPS data and the back slip inversion model show coupling ratio as high as 73% along the southeastern 2007 rupture segment but only 10% on average along the segment of 2010 event. Based on the spatial distribution of coseismic slip, aftershock clusters, derived coupling pattern, and paleogeodetic records, we discovered the former as a semipermanent asperity and the latter as a potential megathrust barrier. We propose that a characteristic earthquake of magnitude not less than Mw 8 will recur in an interval of 100 or more years by either single or doublet earthquake.

6. Single-station monitoring of volcanoes using seismic ambient noise

Seismic ambient noise cross correlation is increasingly used to monitor volcanic activity. However, this method is usually limited to volcanoes equipped with large and dense networks of broadband stations. The single-station approach may provide a powerful and reliable alternative to the classical “cross-station” approach when measuring variation of seismic velocities. We implemented it on the Piton de la Fournaise in Reunion Island, a very active volcano with a remarkable multidisciplinary continuous monitoring. Over the past decade, this volcano has been increasingly studied using the traditional cross-correlation technique and therefore represents a unique laboratory to validate our approach. Our results, tested on stations located up to 3.5 km from the eruptive site, performed as well as the classical approach to detect the volcanic eruption in the 1–2 Hz frequency band. This opens new perspectives to successfully forecast volcanic activity at volcanoes equipped with a single three-component seismometer.

7. Discrepant estimates of primary and export production from satellite algorithms, a biogeochemical model, and geochemical tracer measurements in the North Pacific Ocean

Estimates of primary and export production (PP and EP) based on satellite remote sensing algorithms and global biogeochemical models are widely used to provide year-round global coverage not available from direct observations. However, observational data to validate these approaches are limited. We find that no single satellite algorithm or model can reproduce seasonal and annual geochemically determined PP, export efficiency (EP/PP), and EP rates throughout the North Pacific basin, based on comparisons throughout the full annual cycle at time series stations in the subarctic and subtropical gyres and basin-wide regions sampled by container ship transects. The high-latitude regions show large PP discrepancies in winter and spring and strong effects of deep winter mixed layers on annual EP that cannot be accounted for in current satellite-based approaches. These results underscore the need to evaluate satellite- and model-based estimates using multiple productivity parameters measured over broad ocean regions throughout the annual cycle.

8. Dune-like dynamic of Martian Aeolian large ripples

Martian dunes are sculpted by meter-scale bed forms, which have been interpreted as wind ripples based on orbital data. Because aeolian ripples tend to orient and migrate transversely to the last sand-moving wind, they have been widely used as wind vanes on Earth and Mars. In this report we show that Martian large ripples are dynamically different from Earth's ripples. By remotely monitoring their evolution within the Mars Science Laboratory landing site, we show that these bed forms evolve longitudinally with minimal lateral migration in a time-span of ~ six terrestrial years. Our observations suggest that the large Martian ripples can record more than one wind direction and that in certain cases they are more similar to linear dunes from a dynamic point of view. Consequently, the assumption of the transverse nature of the large Martian ripples must be used with caution when using these features to derive wind directions.


VIII. AGU News

1.AGU FALL MEETING: PRESS REGISTRATION OPEN, BOOK HOTEL NOW

WASHINGTON, DC — 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, at the Moscone Center, 747 Howard St., San Francisco, California.