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AGU Research Spotlight (Nov 11-Nov 17, 2016)

2016-11-18 08:26:45

I. Natural Hazards

1.How Did Climate and Humans Respond to Past Volcanic Eruptions?

First workshop of the Volcanic Impacts on Climate and Society Working Group; Palisades, New York, 6–8 June 2016


II.Hazards & Disasters

1.Coastal Observations from a New Vantage Point

The NASA Geostationary Coastal and Air Pollution Events satellite mission plans to keep an eye on short-term processes that affect coastal communities and ecosystems.


2.Academia and the Military Can Be Valuable Partners

The common cause of protecting people and the environment from disasters can and should unite academics and military personnel.


III. Climate Change

1.Carbon Tax Initiative Fails in Washington State

Environmental groups were divided over the nation's first carbon tax ballot measure.


2.Reactions to Trump Environment Plans: From Defiance to Welcome

Some environmentalists and climate scientists took stances ranging from outrage to hope for common ground, whereas some industry groups embraced the new administration on energy and environment.


3.Predicting a Great Lake's Response to a Warm Winter

The Superior Challenge Summit: Forecasting El Ni?o's Impact on the World's Largest Lake; Ann Arbor, Michigan, 17–19 May 2016


IV. Space & Planets

1.Unprecedented Views of Mercury Constrain Hollow Formation

The consistently shallow depths of the depressions scattered across Mercury's surface suggest their morphology is not determined by the thickness of a volatile-rich outer layer.


2.Mars's Atmosphere Matches Earth's Turbulent Nature

Mars is even more like Earth than we thought, according to a statistical analysis of the planet's swirling atmosphere.


V. Geophysical Research Letters

1. Greenland Ice Sheet flow response to runoff variability

We use observations of ice sheet surface motion from a Global Positioning System network operating from 2006 to 2014 around North Lake in west Greenland to investigate the dynamical response of the Greenland Ice Sheet's ablation area to interannual variability in surface melting. We find no statistically significant relationship between runoff season characteristics and ice flow velocities within a given year or season. Over the 7?year time series, annual velocities at North Lake decrease at an average rate of ?0.9?±?1.1?m?yr?2, consistent with the negative trend in annual velocities observed in neighboring regions over recent decades. We find that net runoff integrated over several preceding years has a negative correlation with annual velocities, similar to findings from the two other available decadal records of ice velocity in western Greenland. However, we argue that this correlation is not necessarily evidence for a direct hydrologic mechanism acting on the timescale of multiple years but could be a statistical construct. Finally, we stress that neither the decadal slowdown trend nor the negative correlation between velocity and integrated runoff is predicted by current ice-sheet models, underscoring that these models do not yet capture all the relevant feedbacks between runoff and ice dynamics needed to predict long-term trends in ice sheet flow.


2. Role of regional wetland emissions in atmospheric methane variability

Atmospheric methane (CH4) accounts for ~20% of the total direct anthropogenic radiative forcing by long-lived greenhouse gases. Surface observations show a pause (1999–2006) followed by a resumption in CH4 growth, which remain largely unexplained. Using a land surface model, we estimate wetland CH4 emissions from 1993 to 2014 and study the regional contributions to changes in atmospheric CH4. Atmospheric model simulations using these emissions, together with other sources, compare well with surface and satellite CH4 data. Modeled global wetland emissions vary by ±3%/yr (σ?=?4.8?Tg), mainly due to precipitation-induced changes in wetland area, but the integrated effect makes only a small contribution to the pause in CH4growth from 1999 to 2006. Increasing temperature, which increases wetland area, drives a long-term trend in wetland CH4 emissions of +0.2%/yr (1999 to 2014). The increased growth post-2006 was partly caused by increased wetland emissions (+3%), mainly from Tropical Asia, Southern Africa, and Australia.


3. A three-dimensional QP imaging of the shallowest subsurface of Campi Flegrei offshore caldera, southern Italy

To improve the knowledge of the shallowest subsurface of Campi Flegrei caldera, a 3-D P wave attenuation tomography of the area was performed. We analyzed about 18,000 active seismic traces, which provided a data set of 11,873 Δt* measurements, e.g., the differential travel times to quality factor ratios. These were inverted through an adapted tomographic inversion procedure. The 3-D tomographic images reveal an average QP about 70, interpreted as water-saturated volcanic and marine sediments. An arc-like, low-QP structure at 0.5–1?km depths was interpreted as a densely fractured, fluid-saturated rock volume, well matching the buried rim of Campi Flegrei caldera. The spatial distribution of high- and low-QP bodies in the inner caldera is correlated with low-Vp values and may reflect either the differences in the percentage of fluid saturation of sediments or the presence of vapor state fluids beneath fumarole manifestations.


4. North-south variations of tropical storm genesis locations in the Western Hemisphere

In the Western Hemisphere, tropical storms or hurricanes form in the North Atlantic and eastern North Pacific. Previous studies have focused on storm variability in the frequency, duration, and intensity in each basin. Here we find that the tropical storm genesis location in one ocean basin ties to the other one. On both interannual and multidecadal time scales, a northward (southward) shift of the tropical storm genesis location is associated with a southward (northward) variation in the other ocean basin. The change of cross-Central America wind in the upper troposphere, which induces an out-of-phase relation of vertical wind shear, bridges storm activity in the two ocean basins. Sea surface temperatures in both the tropical Pacific and North Atlantic can induce the zonal wind change across Central America. An implication of this study is that hurricane outlooks can be improved by considering the two ocean basins together, and thus helping reduce the damage caused by hurricane landfall.


5. Urbanization causes nonstationarity in Indian Summer Monsoon Rainfall extremes

Global and local environmental changes are likely to introduce nonstationarity in the characteristics of Indian Summer Monsoon Rainfall (ISMR) extremes. Here we perform a nonstationary frequency analysis on ISMR extremes in a Generalized Additive Model for Location, Scale and Shape framework with a cluster of 74 models, considering nonstationarity in different possible combinations. Interestingly, we observe significant nonstationarity in ISMR extremes in urbanizing/developing-urban areas (transitioning from rural to urban), compared to completely urbanized or rural areas. This presents a postulation that the extent of urbanization plays a significant role in introducing nonstationarity in ISMR extremes. We emphasize the effect of urbanization in changing the character of ISMR extremes, which further needs a scientific re-evaluation by implementing physics-based modeling. The impact of these observational studies will be critical in correcting the bias of model projections of ISMR.


6. Laboratory air-entraining breaking waves: Imaging visible foam signatures to estimate energy dissipation

Oceanic air-entraining breaking waves fundamentally influence weather and climate through bubble-mediated ocean-atmosphere exchanges, and influence marine engineering design by impacting statistics of wave heights, crest heights, and wave loading. However, estimating individual breaking wave energy dissipation in the field remains a fundamental problem. Using laboratory experiments, we introduce a new method to estimate energy dissipation by individual breaking waves using above-water images of evolving foam. The data show the volume of the breaking wave two-phase flow integrated in time during active breaking scales linearly with wave energy dissipated. To determine the volume time-integral, above-water images of surface foam provide the breaking wave timescale and horizontal extent of the submerged bubble plume, and the foam decay time provides an estimate of the bubble plume penetration depth. We anticipate that this novel remote sensing method will improve predictions of air-sea exchanges, validate models of wave energy dissipation, and inform ocean engineering design.




WASHINGTON, DC — Australia shifts and tilts back and forth by several millimeters each year because of changes to the Earth’s center of mass, according to a new study. The findings could help scientists better track the precise location of Earth’s center of mass, which is important for GPS and other satellite measurements, according to the study’s author.


VII.Earth and Space Science

1.New maps reveal safe locations for wastewater injection

Geophysicists have compiled the most detailed maps yet of the geologic forces controlling the locations, types and magnitudes of earthquakes in Texas and Oklahoma. These new “stress maps” provide insight into the nature of the faults associated with recent temblors, many of which appear to have been triggered by the injection of wastewater deep underground.



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