AGU 期刊一周Research Spotlights (June 09~June 15, 2016)

发布时间:2016-6-17 8:50:52 点击次数:707

I. Atmospheric Sciences

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

The proposed wind farm, which commercial fishermen oppose, could produce at least 70 megawatts of energy annually, enough to power a quarter of a million homes.

2. Pinatubo 25 Years Later: Eight Ways the Eruption Broke Ground

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

Preliminary results from field measurements of smoldering Kalimantan peatlands suggest that the fires emitted 8% less carbon dioxide and 55% less methane than were previously estimated from lab tests.

II. Geology & Geophysics

1. Advancing Science Through the Renovation of AGU's Headquarters

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 pathways to a geosciences career can be confusing and complex, but the American Geophysical Union has a suite of resources to help students and their mentors plan their strategy.

3. Multicolor Terrain Mapping Documents Critical Environments

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?

Researchers investigate the factors that cause river terraces to form.

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

On World Oceans Day, let's reflect on the now realizable potential for investing in and building upon new opportunities that beckon from the sea.

2. Space Weather Research and Forecasting Act Introduced to Senate

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?

New research evaluates the ability of coastal foliage to influence the ocean's pH.

VI. Planetary Sciences

1. Curiosity Sends Curious Water Data from Mars

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

What scientists thought was a sunken Greek city turns out to be the fossils of an ancient hydrocarbon seep from several million years ago.


VIII.Earth and Space Science

1. Antarctic lakes provide glimpse of ancient forest fires, modern human impacts

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

A really interesting paper has just been published in Geophysical Research Letters examining the response of Californian earthflows to the ongoing, epic drought.  This paper was led by Georgie Bennett, currently at the US Forest Service and Colorado State University, but who will be joining us here at the University of East Anglia in January 2017 as a full faculty member. California has been suffering a serious drought for many years now.  In the paper, Bennett et al (2016) mapped 98 active earthflows in a 140 square kilometre area of the Eel River catchment in California.  This is an area with multiple large, often deep earthflows that are an important part of the geomorphic system.

3. The Dragons are Calling

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

For six recent Martian years, temperature records from NASA Mars orbiters reveal a pattern of three types of large regional dust storms occurring in sequence at about the same times each year during the southern hemisphere spring and summer. Each Martian year lasts about two Earth years.

IX. Geophysical Research Letters

1. Land surface and atmospheric conditions associated with heat waves over the Chickasaw Nation in the South Central United States

Exposure to extreme heat was reconstructed based on regional land-atmosphere processes from 1979 to 2010 in the South Central U.S. The study region surrounds the Chickasaw Nation (CN), a predominantly Native American population with a highly prevalent burden of climate-sensitive chronic diseases. Land surface and atmospheric conditions for summer heat waves were analyzed during spring (March-April-May, MAM) and summer (June-July-August, JJA) based on the Climate and Ocean: Variability, Predictability, and Change maximum temperature definition for heat wave frequency (HWF). The spatial-temporal pattern of HWF was determined using empirical orthogonal function (EOF) analysis and the corresponding principle component time series of the first EOF of HWF. Statistically significant analyses of observed conditions indicated that sensible heat increased and latent heat fluxes decreased with high HWF in the South Central U.S. The largest positive correlations of sensible heat flux to HWF and the largest negative correlations of latent heat flux to HWF were specifically observed over the CN. This is a significantly different energy transfer regime due to less available soil moisture during the antecedent MAM and JJA. The higher sensible heat from dry soil could cause significant warming from the near surface (>2.0°C) to the lower troposphere (>1.5°C), and accumulated boundary layer heat could induce the significant patterns of higher geopotential height and enhance anticyclonic circulations (negative vorticity anomaly) at the midtroposphere. Results suggested a positive land-atmosphere feedback associated with heat waves and called attention to the need for region-specific climate adaptation planning.

2. Tidal Disruption of Phobos as the Cause of Surface Fractures

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].

3. Climate change reduces warming potential of nitrous oxide by an enhanced Brewer-Dobson circulation

The Brewer-Dobson circulation (BDC), which is an important driver of the stratosphere-troposphere exchange, is expected to accelerate with climate change. One particular consequence of this acceleration is the enhanced transport of nitrous oxide (N2O) from its sources at the Earth's surface toward its main sink region in the stratosphere, thus inducing a reduction in its lifetime. N2O is a potent greenhouse gas and the most relevant currently emitted ozone-depleting substance. Here we examine the implications of a reduced N2O lifetime in the context of climate change. We find a decrease in its global warming potential (GWP) and, due to a decline in the atmospheric N2O burden, also a reduction in its total radiative forcing. From the idealized transient global warming simulation we can identify linear regressions for N2O sink, lifetime, and GWP with temperature rise. Our findings are thus not restricted to a particular scenario.

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.