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AGU Research Spotlight (Sep 29-Oct 05, 2016)

2016-10-07 08:38:55

I. Atmospheric Sciences

1. Eliminating Uncertainty One Cloud at a Time

The impact of clouds on climate change has been a scientific mystery for decades. Now researchers are fighting to gain the upper hand.


II. Geology & Geophysics

1. Call for Comments: Responsibilities and Rights of Scientists

The American Geophysical Union urges members to comment soon on the organization's new draft position statement about scientists' responsibilities and rights and the integrity of the scientific process.


2. Earthquakes Could Funnel Radio Waves to Dark Zones in Mountains

By being coupled with a layer of mobile electrical charges on the Earth's surface, radio waves could travel over the ground to areas that would normally be unreachable, like behind a mountain.


3. Tide Gauge Records May Underestimate 20th Century Sea Level Rise

Tide gauges can help measure sea level change, but their limited locations and short records make it hard to pinpoint trends. Now researchers are evaluating the instruments' limitations.


4. Mapping Water and Heat Deep Under Long Valley Caldera

Researchers use electrical resistivity to find the heat source and reservoir feeding Long Valley Caldera's labyrinthine hydrothermal system.



1.The Arctic Freshwater Synthesis

The result of international study and coordination, this Special Issue provides an important "state-of-the-science" review of changing systems and their potential impacts.


IV. Climate Change

1.Switching to Drought-Tolerant Plants Could Alter Urban Climates

In Los Angeles, replacing lawns with native plants that need less water could lead to hotter days and cooler nights.


2. Mars’s Climate May Have Been Wet Much Later Than Thought

Water-carved valleys may be relatively young, challenging assumptions about the history of the Red Planet's climate.


3. Climate Change, Groundwater Management, and California's Future

Conference on Climate Change and the Sustainable Groundwater Management Act; University of California, Davis, California, 4–5 April 2016


V. Earth and Space Science

1.Research suggests Saturn’s moon Dione may harbor a subsurface ocean

A subsurface ocean could lie deep within Saturn’s moon Dione, according to a new study using publicly available data from the Cassini mission to Saturn. In 2013, images from NASA’s Cassini spacecraft hinted that Dione had a subsurface ocean when the moon formed, but the new study suggests the ocean could still exist today.


VI. Geophysical Research Letters

1. Spatial coherence of the seismic wavefield continuously recorded by the USArray

We use a method based on the array covariance matrix eigenvalues to study the level of spatial coherence and of isotropy of the seismic wavefield continuously recorded during 2010 by the USArray. First, we observe that the raw data are often dominated by local sources. To remove their influence, we apply spectral and temporal normalizations to the input signals. We notice that this widely used preprocessing in ambient-noise seismology does not fully homogenize the seismic wavefield and that some strongly coherent arrivals persist. Among these persistent signals generated by teleseismic sources we detect (1) seismic waves emitted by strong earthquakes, (2) a nearly continuous quasi-monochromatic signal at 26 s period, and (3) multiday coherent wave trends in the spectral band of oceanic microseisms (0.07–0.2 Hz). For the latter, beamforming analysis shows that while most of the signals are composed of surface waves, some are dominated by body waves likely generated in the deep ocean.


2. Global modeling of tropospheric iodine aerosol

Natural aerosols play a central role in the Earth system. The conversion of dimethyl sulfide to sulfuric acid is the dominant source of oceanic secondary aerosol. Ocean emitted iodine can also produce aerosol. Using a GEOS-Chem model, we present a simulation of iodine aerosol. The simulation compares well with the limited observational data set. Iodine aerosol concentrations are highest in the tropical marine boundary layer (MBL) averaging 5.2 ng (I) m?3 with monthly maximum concentrations of 90 ng (I) m?3. These masses are small compared to sulfate (0.75% of MBL burden, up to 11% regionally) but are more significant compared to dimethyl sulfide sourced sulfate (3% of the MBL burden, up to 101% regionally). In the preindustrial, iodine aerosol makes up 0.88% of the MBL burden sulfate mass and regionally up to 21%. Iodine aerosol may be an important regional mechanism for ocean-atmosphere interaction.


3. Sea level rise and inundation of island interiors: Assessing impacts of lake formation and evaporation on water resources in arid climates

Coasts of many low-lying islands will be inundated should sea level rise by 1?m by 2100 as projected, thereby decreasing water resources through aquifer salinization. A lesser known impact occurs if rising sea level elevates water tables above interior topographic lows to form lakes. Impacts of lake formation on water resources, however, remain unquantified. Here we use hydrological models, based on islands in the Bahamian archipelago, to demonstrate that on islands with negative water budgets, evaporation following lake inundation can cause more than twice the loss of fresh groundwater resources relative to an equivalent amount of coastal inundation. This result implies that in dry climates, low-lying islands with inland depressions could face substantially greater threats to their water resources from sea level rise than previously considered.


4. The crustal structure beneath Mauritius from teleseismic P-receiver functions - oceanic or continental?

It has recently been suggested that the volcanic island of Mauritius may be underlain by a remnant of continental origin termed “Mauritia”. To constrain the crustal thickness beneath Mauritius, we analyzed data from 11 land stations, 10 of which were deployed recently by the RHUM-RUM project. From the recordings, we obtained 382 P-receiver functions (RFs). By applying the H-κ stacking technique, we derive crustal thicknesses of approximately 10–15?km. We observe a considerable variation in the Vp/Vs-ratio caused by a lack of clear multiples. Using forward modeling of RFs, we show that the lack of clear multiples can be explained by a transitional Moho, where the velocity increases gradually. The modeling further indicates that the thickness of this gradient zone is estimated to be approximately 10?km. We argue that our findings suggest oceanic crust thickened by crustal underplating due the mantle plume currently located beneath the La Réunion.




WASHINGTON, DC — A new study connects the unprecedented West Coast toxic algal bloom of 2015 that closed fisheries from southern California to northern British Columbia to the unusually warm ocean conditions — nicknamed “the blob” — in winter and spring of that year.



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