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AGU Research Spotlight (May 18-May 24, 2018)

2018-05-29 22:58:41

I. Hydrology, Cryosphere & Earth Surface

1. Making Maps on a Micrometer Scale

Geographic information system software, created for mapping cities and continents, works equally well with the minuscule layers and inclusions that record a crystal's history.


II. Hazards & Disasters

1. Magma Flow in a Major Icelandic Eruption

Mechanical modeling suggests that previous, undetected eruptions released tectonic stress near the ice-covered Bár?arbunga volcano.


2. Faster Lava Flows, Explosive Eruptions Begin at Kīlauea

Scientists say the dramatic increase in flows is likely due to the arrival of younger, hotter magma in the system.


III. Biogeosciences

1. Fresh Take on a Gold Treasure’s Origins Using Geochemistry

Blending geoscience and archaeology, researchers apply a new technique to pinpoint where ancient and unique gold artifacts were crafted.


IV. Ocean Sciences

1. Tides and Waves Interact to Cause Hurricanes in Near-Space

The interaction of tides and waves generated in the lower atmosphere can cause the mean zonal wind speed in the lower ionosphere to oscillate equivalent to a category 1 hurricane at Earth’s surface.


V. Geology & Geophysics

1. Challenging the Day Diagram, a Rock Magnetism Paradigm

A critique of the plot routinely used to determine bulk magnetic properties concludes the technique is so ambiguous that new approaches to understanding magnetic mineral assemblages must be developed


2. Touring the Solar System with Science Art

No sketchy science here! Just science sketches that bring conference note-taking to a whole new level.


3. What Shaped the Northern Apennine Deformation Front?

An integrated interpretation of well and seismic reflection data from Italy’s Po Valley shows the range’s undulations are controlled by the slope and composition of two major gliding horizons.


VI. Planetary Sciences

1. Postal Service Honors First American Woman in Space

New postage stamp features space shuttle astronaut Sally Ride, a role model for girls, women, and diversity in science. It puts “a stamp” on Ride’s accomplishments, her widow told Eos.


VII. Geophysical Research Letters

1. Strong linkage of El Ni?o‐Southern Oscillation to the polar cold air mass in the Northern Hemisphere

The total hemispheric polar cold air mass (PCAM) amount below a threshold potential temperature is conserved under an adiabatic condition and is a good indicator of polar warming. While the long‐term PCAM trends have been investigated, the cause of its interannual variability remains uncertain. Here, we find that the El Ni?o‐Southern Oscillation (ENSO) has a strong impact on the total northern hemispheric PCAM amount below a potential temperature of 280 K. The correlation coefficient between the Ni?o‐3.4 and the total PCAM reaches ‐0.66 over 36 recent winters. During El Ni?o, the PCAM decreases significantly because of the shorter PCAM residence time at high latitudes. The Aleutian Low intensifies and effectively transfers the PCAM from North America to the North Pacific, causing a significant decrease in the PCAM amount over the northern part of North America and a strengthening of cold air outflows over the central North Pacific. The PCAM coming to the warm ocean disappears rapidly and results in the imbalance of the hemispheric PCAM. This study reveals a notable influence of the tropical forcing on the variability of polar climate.


2. Could machine learning break the convection parameterization deadlock?

Representing unresolved moist convection in coarse‐scale climate models remains one of the main bottlenecks of current climate simulations. Many of the biases present with parameterized convection are strongly reduced when convection is explicitly resolved (i.e. in cloud resolving models at high spatial resolution ~ a kilometer or so). We here present a novel approach to convective parameterization based on machine learning, using an aquaplanet with prescribed sea surface temperatures as a proof of concept. A deep neural network is trained with a superparameterized version of a climate model in which convection is resolved by thousands of embedded 2D cloud resolving models. The machine learning representation of convection, which we call the Cloud Brain (CBRAIN) can skillfully predict many of the convective heating, moistening, and radiative features of superparameterization that are most important to climate simulation, although an unintended side effect is to reduce some of the superparameterization's inherent variance. Since as few as three months' high frequency global training data prove sufficient to provide this skill, the approach presented here opens up a new possibility for a future class of convection parameterizations in climate models that are built “top‐down”, i.e. by learning salient features of convection from unusually explicit simulations.


3. Application of a luminescence‐based sediment transport model

Quantifying the transport history of sand is a challenging but important goal in geomorphology. In this paper, we take a simple idea, that luminescence is bleached during transport and regenerates during storage, and use this as a basis to re‐envision luminescence as a sediment tracer. We apply a mathematical model describing luminescence through an idealized channel and reservoir system and then compare this idealized model to real rivers to see if luminescence can reproduce known sediment transport data. We provide results from application of this luminescence method in three rivers from the mid‐Atlantic region of the United States. This method appears promising. However, as a river system diverges from idealized conditions of the mathematical model, the luminescence data diverges from model predictions. We suggest that spatial variation in the delivery of sediment from hillslopes can be reflected in the channel sediment luminescence, and that luminescence acts as a function of landscape dynamics.


4. ENSO Transition Asymmetry: Internal and External Causes and Intermodel Diversity

El Ni?o is frequently followed by La Ni?a but the opposite case rarely happens. Here, we explore a mechanism for such an asymmetrical transition and its future changes. Internally the asymmetrical response of upper ocean waves against surface wind stress anomaly exerts a primary cause of ENSO transition asymmetry. Externally the asymmetrical capacitor effects of both Indian and Atlantic Oceans play some roles in driving the ENSO transition asymmetry via the inter‐basin interactions. The historical runs of CMIP5 show that the intermodel transition asymmetry is significantly correlated with the intermodel asymmetry in ocean wave response to surface wind forcing but not with that in the inter‐basin interactions. In addition, the El Ni?o‐to‐La Ni?a transition tendency was weaker in moderate global warming scenario runs (RCP4.5), while slightly enhanced in strong warming scenario runs (RCP8.5). Similar changes also appeared in the asymmetrical response of ocean waves against the surface wind forcing.


5. A statistical study of slow‐mode shocks observed by MMS in the dayside magnetopause

We investigated characteristics of slow‐mode shocks in the dayside magnetopause based on Magnetospheric Multiscale (MMS) observations from September 2015 to February 2017. We analyzed 99 magnetopause crossings with reconnection jets and high time resolution data, out of which 20 crossings showed slow‐mode shock signatures. Out of these crossings, one crossings showed slow‐mode shock signature on both sides, and the rest had slow‐mode shock signatures on one side, 6 (13) on magnetosphere (magnetosheath). The detection probability of slow‐mode shocks in the magnetopause is ~20%, which is greater than that reported in the magnetotail. We also found 12 rotational discontinuities in these slow‐mode shock events. The results also show that the observation of magnetosphere side slow‐mode shock is favored when the number density ratio of magnetosheath to magnetosphere is small. No clear dependence of the existence of slow‐mode shocks on other parameters such as, plasma beta, temperature anisotropy, jet velocity was found.


6. Predictions and observations for the oceanic lithosphere from S‐to‐P receiver functions and SS precursors

The ocean lithosphere is classically described by the thermal half space cooling (HSC) or the plate models, both characterized by a gradual transition to the asthenosphere beneath. Scattered waves find sharp seismic discontinuities beneath the oceans, possibly from the base of the plate. Active source studies suggest sharp discontinuities from a melt channel. We calculate synthetic S‐to‐P receiver functions and SS precursors for the HSC and plate models and also for channels. We find that the HSC and plate model velocity gradients are too gradual to create interpretable scattered waves from the base of the plate. Subtle phases are predicted to follow a similar trend as observations, flattening at older ages. Therefore, the seismic discontinuities are probably caused by a thermally controlled process that can also explain their amplitude, such as melting. Melt may coalesce in channels, although channels > 10 km thick should be resolvable by scattered wave imaging.


VII. AGU Blogs

1. New study details geological process behind Titan’s dunes

Titan’s windswept dunes may sprawl millions of more kilometers than previously thought and were likely formed by geological processes similar to those on Earth, according to a new study. The new findings could help scientists look for life or its molecular precursors on Saturn’s largest moon.


2. Time to feed CheMin

After successfully drilling the ‘Duluth’ target on Sol 2057 (as seen in the above Mastcam image), the science team is eager to find out what it’s made of.


3. Characterizing a Successful Drill!

This past weekend, Curiosity successfully drilled into the ‘Duluth’ rock target, generating a beautiful pile of drill tailings! This is a very exciting time for us on the rover team, who have been waiting for quite a while to successfully drill into a target and to ingest samples into the rover’s analytical instruments.


4. Voyage to the White Shark Café: Plankton — Video Update

“As an oceanographer, I’m interested in asking: What do they eat? Where are the plants? What fuels this?”


5. Voyage to the White Shark Café: Saildrone — video update

In this highlight video, take a guided tour with Dr. Bruce Robison as he talks through some of the wonderful life that the research team has seen with ROV SuBastian during the #WhiteSharkVoyage.


6. Voyage to the White Shark Café: Wrap up video

By Mónika Naranjo González “This research cruise is actually a beginning in which we are going to go out, offer the opportunity for policy changes that protect a region that no one would think about needs protection for white sharks. Through new knowledge we can reduce ignorance and then translate that into into action.” Dr Block has been thinking about this expedition for over a decade.




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