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AGU Research Spotlight (Sep 08-Sep 14, 2017)

2017-09-15 09:58:08

I. Climate Change

1. India’s Plans for Coal Clash with Paris Agreement

India’s proposed coal plants threaten to lock out its low-emission energy goals under the international climate accord.


2. Coordinating and Communicating Carbon Cycle Research

2017 Joint NACP and AmeriFlux Principal Investigators Meeting; Bethesda, Maryland, 27–30 March 2017


3. A Diary of a Storm

When Hurricane Harvey struck Texas more than a week ago, an Eos staff editor based in Houston hunkered down. Here’s her day-by-day account of the storm and its aftermath.


II. Hazards & Disasters

1. Largest Flare of Past 9 Years Erupts from Sun

A massive flare and blast of charged particles toward Earth may disrupt satellites and communications and push auroras toward lower latitudes through tomorrow, according to space weather experts.


2. Hurricane Irma Tears Across Caribbean, Heads to South Florida

Florida residents prepare for potentially catastrophic winds and flooding.


III. Ocean Sciences

1. Monitoring Ocean Change in the 21st Century

Time series data sets, which contain measurements repeated over a span of decades, yield important insights into our oceans’ vital signs.


IV. Atmospheric Sciences

1. Ship Exhaust Makes Oceanic Thunderstorms More Intense

A new study provides some of the first evidence that humans are changing cloud formation on a nearly continual basis.


V. Biogeosciences

1. Following Carbon in an Age of Fire

As fires become more prevalent in California, researchers work to create a profile of the charred carbon left behind.


VI. Space & Planets

1. Ancient Maya May Have Foreseen Meteor Showers

Modern astronomical techniques have uncovered clues to a possible facet of Mayan astronomy from nearly 2 millennia ago not found in surviving records.


2. Juno Gets Spectacular View of Jupiter’s Aurora

The NASA spacecraft has taken images of Jupiter’s powerful aurora dancing around its poles, revealing never-before-seen details in their structure.


VII. Geophysical Research Letters

1. Permafrost collapse shifts alpine tundra to a carbon source but reduces N2O and CH4 release on the northern Qinghai-Tibetan Plateau

Important unknowns remain about how abrupt permafrost collapse (thermokarst) affects carbon balance and greenhouse gas flux, limiting our ability to predict the magnitude and timing of the permafrost carbon feedback. We measured monthly, growing-season fluxes of CO2, CH4, and N2O at a large thermokarst feature in alpine tundra on the northern Qinghai-Tibetan Plateau (QTP). Thermokarst formation disrupted plant growth and soil hydrology, shifting the ecosystem from a growing-season carbon sink to a weak source but decreasing feature level CH4 and N2O flux. Temperature-corrected ecosystem respiration from decomposing permafrost soil was 2.7 to 9.5-fold higher than in similar features from Arctic and Boreal regions, suggesting that warmer and dryer conditions on the northern QTP could accelerate carbon decomposition following permafrost collapse.


2. What are the contemporary sources of sediment in the Mississippi River?

Within the last two centuries, the Mississippi River basin has been transformed by changes in land use practices, dam construction, and training of the rivers for navigation. Here we analyze the contemporary patterns of fluvial sediment yield in the Mississippi River basin using all available data in order to assess the influence of regional land condition on the variation of sediment yield within the basin. We develop regional-scale relations between specific sediment yield (yield per unit area) and drainage area to reveal contemporary regional sediment yield patterns and source areas of riverine sediments. Extensive upland erosion before the development of soil conservation practices exported large amounts of sediment to the valleys and floodplains. We show that sediment today is sourced primarily along the river valleys from arable land, and from stream bank and channel erosion, with sediment yields from areas dominated by arable land 2 orders of magnitude greater than that of grassland dominated areas. Comparison with the “T factor,” a commonly quoted measure of agricultural soil resilience suggests that the latter may not reflect contemporary soil loss from the landscape.


3. Deep crustal melt plumbing of Bárearbunga volcano, Iceland

Understanding magmatic plumbing within the Earth's crust is important for understanding volcanic systems and improving eruption forecasting. We discuss magma plumbing under Bárearbunga volcano, Iceland, over a 4 year period encompassing the largest Icelandic eruption in 230 years. Microseismicity extends through the usually ductile region of the Earth's crust, from 7 to 22 km depth in a subvertical column. Moment tensor solutions for an example earthquake exhibits opening tensile crack behavior. This is consistent with the deep (>7 km) seismicity being caused by the movement of melt in the normally aseismic crust. The seismically inferred melt path from the mantle source is offset laterally from the center of the Bárearbunga caldera by ~12 km, rather than lying directly beneath it. It is likely that an aseismic melt feed also exists directly beneath the caldera and is aseismic due to elevated temperatures and pervasive partial melt under the caldera.


4. Creep and slip: Seismic precursors to the Nuugaatsiaq landslide (Greenland)

Precursory signals to material's failure are predicted by numerical models and observed in laboratory experiments or using field data. These precursory signals are a marker of slip acceleration on weak regions, such as crustal faults. Observation of these precursory signals of catastrophic natural events, such as earthquakes and landslides, is necessary for improving our knowledge about the physics of the nucleation process. Furthermore, observing such precursory signals may help to forecast these catastrophic events or reduce their hazard. I report here the observation of seismic precursors to the Nuugaatsiaq landslide in Greenland. Time evolution of the detected precursors implies that an aseismic slip event is taking place for hours before the landslide, with an exponential increase of slip velocity. Furthermore, time evolution of the precursory signals' amplitude sheds light on the evolution of the fault physics during the nucleation process.


5. Longwave emission trends over Africa and implications for Atlantic hurricanes

The latitudinal gradient of outgoing longwave radiation (OLR) over Africa is a skillful and physically based predictor of seasonal Atlantic hurricane activity. The African OLR gradient is observed to have strengthened during the satellite era, as predicted by state-of-the-art global climate models (GCMs) in response to greenhouse gas forcing. Prior to the satellite era and the U.S. and European clean air acts, the African OLR gradient weakened due to aerosol forcing of the opposite sign. GCMs predict a continuation of the increasing OLR gradient in response to greenhouse gas forcing. Assuming a steady linear relationship between African easterly waves and tropical cyclogenesis, this result suggests a future increase in Atlantic tropical cyclone frequency by 10% (20%) at the end of the 21st century under the RCP 4.5 (8.5) forcing scenario.


VII. AGU Blogs

1. Increases in wildfire-caused erosion could impact water supply and quality in the West

A growing number of wildfire-burned areas throughout the western United States are expected to increase soil erosion rates within watersheds, causing more sediment to be present in downstream rivers and reservoirs, according to a new study published online in Geophysical Research Letters, a journal of the American Geophysical Union.


2. Big earthquake in southwestern Mexico, M8.1

An earthquake occurred overnight in southwestern Mexico, inland from the Middle America Trench, a subduction zone where the Cocos Plate (oceanic lithosphere) is being shoved down and under the North American Plate (continental lithosphere at this location). The Cocos Plate is being generated today through seafloor spreading at the East Pacific Rise, and is being “recycled” into the mantle beneath southwestern Mexico and Central America.


3. North Korea blast lights up Alaska seismometers

On Saturday night, Matt Gardine was at home outside Fairbanks playing with his daughter when his phone beeped. As the seismologist on call with the Alaska Earthquake Center, Gardine’s duty was to get information out about detectable earthquakes right after they happen.



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