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AGU Research Spotlight (Jun 09-Jun 15, 2016)

2016-06-17 08:50:52

I. Atmospheric Sciences

1.Interior Approves Wind Farm Leasing Offshore from New York City

From the first rapid assessment of a volcano's history to insights on geoengineering, the 15 June 1991 eruption of Mount Pinatubo changed the way we approach and learn from volcanic hazards.

3.The 2015 Indonesian Fires: Less Carbon Release Than Was Thought

Earth and space science society aims to showcase science, promote collaboration, and push the limits of sustainable practice through renovation of its headquarters.

2.AGU Talent Pool Programs Can Help Students with Next Career Steps

The Titan airborne topographic laser system takes spatial and spectral data at three wavelengths at once, mapping threats from climate change and ecological disasters in regions with complex terrain.

III.Hydrology, Cryosphere & Earth Surface

1. A River Runs Through It, but Why?2.The Mathematics of Braided Rivers

River researchers find a mathematical relationship that predicts the average shape of a riverbed over a defined distance, opening the door to new ideas about modeling braided rivers.

IV. Science Policy

1.The New Blue Economy: A Vast Oceanic Frontier

This bill is a welcome and proactive effort to align all federal agencies to act in the nation's best interest when it comes to forecasting and responding to extreme space weather events.

V. Climate Change

1.Can Mangroves Buffer Ocean Acidification?

The rover's neutron spectroscopy instrument hints at an unexpected trend: The upper soil levels in the layers of Gale Crater's Kimberley formation seem to hold more water-associated hydrogen.

VII.Ocean Sciences

1."Sunken City" Was Really Made by Microbes

The distinctive molecular signatures can provide researchers with a glimpse into the planet’s long history of combustion. Atmospheric black carbon, which is generated by wildfires or fossil fuel use, become preserved in glaciers, which in turn serve as long-term reservoirs and chemical time capsules.

2.The response of Californian earthflows to drought

Verdant mountains embroider a necklace that surrounds the half-moon shaped beach of Nha Trang, where R/V Falkor awaits her next expedition.

Life everywhere is dependent on the ocean’s health, but this reality is quite apparent here. Tourism is the backbone of the local industry in this coastal city with sandy beaches, a seabed dotted with diverse corals and a turquoise bay rich in fisheries and seafood.

4.NASA Mars orbiters reveal seasonal dust storm pattern

Phobos, the innermost satellite of Mars, displays an extensive system of grooves that are mostly symmetric about its sub-Mars point. Phobos is steadily spiraling inward due to the tides it raises on Mars lagging behind Phobos’ orbital position and will suffer tidal disruption before colliding with Mars in a few tens of millions of years [Kaula, 1964; Mignard, 1981; Dobrovolskis, 1982; Burns, 1978; Bills et al., 2005]. We calculate the surface stress field of the de-orbiting satellite and show that the first signs of tidal disruption are already present on its surface. Most of Phobos’ prominent grooves have an excellent correlation with computed stress orientations. The model requires a weak interior that has very low rigidity on the tidal evolution timescale, overlain by a ~10-100?m exterior shell that has elastic properties similar to lunar regolith [Horvath et al., 1980] or powdery asteroid materials [Blum, 2006; Asphaug, 2009; Scheeres et al., 2010].

4.Young Martian Crater Gratteri and its Secondary Craters

In response to questions that have been raised about formation and effects of secondary craters on crater chronometry techniques, we studied properties of the secondary crater field around the young Martian primary ray crater Gratteri (diameter 7?km). The crater has an estimated age of 1 to 20 My, based on counts of small craters on flat interior surface, consistent with a likely age for a young crater its size (Hartmann et al. 2010). Among our findings: (1) We identify an unusual class of craters we call “rampart secondaries” which may suggest low angle impacts. (2) We measured size distributions of secondaries as a function of distance from Gratteri and used these data to reconstruct the mass-velocity distribution of ejecta blasted out of Gratteri. Our data suggest that crater density in rays tends to peak around 120-230?km from Gratteri (roughly 20-30D), and reaches roughly 30-70 times the inter-ray crater density. (3) Comparable total numbers of secondaries form inside rays and outside rays, and about half are concentrated in clusters in 2% of the area around Gratteri, with the others scattered over 98% of the area out to 400?km away from Gratteri. (4) In the old Noachian plains around Gratteri, secondaries have minimal effect on crater chronometry. These results, along with recently reported direct measurements of the rate of formation of 10?m-20?m primaries on Mars (Daubar et al., 2013), tend to negate suggestions that the numbers and/or clustering of secondaries destroy the effectiveness of crater counting as a chronometric tool.

5.Variability of Tornado Occurrence over the Continental United States since 1950

The United States experiences the most tornadoes of any country in the world. Given the catastrophic impact of tornadoes, concern has arisen regarding the variation in climatology of U.S. tornadoes under the changing climate. A recent study claimed that the temporal variability of tornado occurrence over the continental U.S. has increased since the 1970s. However, that study ignored the highly regionalized climatology of U.S. tornadoes. To address this issue, we examined the long-term trend of tornado temporal variability in each continental U.S. state. Based on the 64-year tornado records (1950-2013), we found that the trends in tornado temporal variability varied across the U.S., with only one-third of the continental area or three out of ten contiguous states (mostly from the Great Plains and Southeast, but where the frequency of occurrence of tornadoes is greater) displaying a significantly increasing trend. The other two-thirds area, where 60% of the U.S. tornadoes were reported (but the frequency of occurrence of tornadoes is less), however, showed a decreasing or a near-zero trend in tornado temporal variability. Furthermore, unlike the temporal variability alone, the combined spatial-temporal variability of U.S. tornado occurrence has remained nearly constant since 1950. Such detailed information on the climatological variability of U.S. tornadoes refines the claim of previous study and can be helpful for local mitigation efforts toward future tornado risks.


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