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AGU Research Spotlight (Jul 13-Jul 19, 2018)

2018-07-20 11:19:17

I.Climate Change

1.Evaluating the Accuracy of Seasonal Climate Predictions

An analysis of historical modeling outputs is improving our understanding of the relationships between different types of seasonal forecasting skills.


2.Icy Interactions

Complex interactions between ice sheets and other components of the Earth system determine how ice sheets contribute to sea level rise.


II.Science Policy & Funding

1.New EPA Head Says His Priorities Include Regulatory Relief

Andrew Wheeler brings a new tone and a vow of openness to the agency. However, he plans to pursue the same goal as his predecessor, which could weaken environmental regulations.


2.Dive into Ocean Issues with Shermans Lagoon

Sherman’s Lagoon creator talks to Eos about providing light-hearted entertainment while weaving in ocean facts and larger messages about threats to the ocean and its creatures.


III.Space & Planets

1.AGU and AAS Join Forces to Foster Understanding of Exoplanets

Enhanced cooperation between organizations representing astronomers and Earth and space scientists will build upon interdisplinary work already bridging geophysics and astronomy.


1.Ten New Moons Discovered Around Jupiter

The newly plotted moons of Jupiter include one“oddball”that orbits in the wrong direction and may be the remnant of a head-on collision.


IV.Natural Resources

1.Meeting the Mineral Needs of the United States

A recent report points out where the United States is most dependent on mineral imports and highlights some ways for reducing this dependence.



1.Glacial Meltwater Plumes Support Greenland Phytoplankton Blooms

Field measurements from the Bowdoin Glacier show that entrainment of deep water into upwelling glacial discharge delivers crucial nutrients to the surface of the surrounding fjord.


VI.Geophysical Research Letters

1.Ionospheric Density Irregularities, Turbulence, and Wave Disturbances during the Total Solar Eclipse over North America on 21 August 2017

Data from ionosonde and GPS total electron content (TEC) observations reveal a number of ionospheric phenomena during the total solar eclipse on 21 August 2017 over North America. The eclipse started over the west coast at~16:00 UTC (~07:53 LT) and ended over the east coast at~20:00 UTC (~14:46 LT). We identify a growth of plasma density irregularities and turbulence on the bottomside ionosphere during the eclipse totality (at~10:03 LT over Idaho Falls), signified by the distinct appearance of spread‐F echoes in the ionosonde data. In addition, data from the ionosonde observations also show some characteristic signatures of traveling ionospheric disturbances (TIDs) at~300 km altitude during the eclipse. Finally, large reductions in TEC and ionospheric plasma densities (by 33?45%) due to the eclipse were observed in both the GPS TEC and ionosonde data.


2.The Impact of Realistic Elastic Properties on Inversions of Shallow Subduction Interface Slow Slip Events Using Seafloor Geodetic Data

We examine the effects of topography and material heterogeneity on geodetic inversions of shallow slow slip at the Hikurangi Subduction Margin, New Zealand. Offshore vertical data from Absolute Pressure Gauges constrain our results. Using a finite element code to generate our Green's functions, we find that topography has a relatively small effect, reducing the seismic potency by only about 5% when compared to a flat model. When material heterogeneity from a New Zealand‐wide seismic velocity model is taken into account, we find an extremely large effect, with the seismic potency increasing by 58% or more. In previous work, we found the opposite effect for deeper slip events, where models including elastic property variations result in ~20% more slip than when they are neglected. Our previous results for deeper events are consistent with a simplified model that considers the elastic property contrasts between a strong subducting slab and a weaker overriding plate. To understand the opposite behavior of our shallower models we use synthetic forward models and view material property gradients in terms of additional body forces. We find that gradients in elastic properties can produce very different surface displacements near the source than simple contrasts, thus explaining the contrasting results for shallow slip events. Combined with our previous results for deeper events, this implies that neglecting material heterogeneity in slow slip inversions may result in overestimates in the amount of slip for deeper events and underestimates for shallow events.


3.SouthAtlanticforced multidecadal teleconnection to the midlatitude South Indian Ocean

Sea surface temperature (SST) in the mid‐latitude South Indian Ocean (MSIO) exhibits prominent multidecadal fluctuations that have profound climate impacts for regions around the Indian Ocean. Observational analysis suggests these multidecadal fluctuations can be explained by remote forcing from South Atlantic multidecadal variability (SAMV). A suite of Atlantic Pacemaker experiments performs well in reproducing the observed MSIO SST multidecadal variation and its association with the South Atlantic. This trans‐basin covariability can be described by an atmospheric bridge mechanism, in which SAMV‐related SST warming weakens regional meridional circulation over the South Atlantic, suppressing convection over tropical Africa. The reduced diabatic heating then drives cold atmospheric Kelvin wave that penetrates into the tropical Indian Ocean, leading to an anomalous cyclonic circulation there that weakens the westerlies over the MSIO and subsequently triggers the warming of MSIO. This initial warming is further amplified by local SST–water vapor positive feedback over the MSIO.


4.Predicting rates and distribution of carbonate melting in oceanic upper mantle: Implications for seismic structure and global carbon cycling

Coupling a global mantle flow model with a parameterized carbonate solidus, we examine the global distribution and extent of carbonate melting beneath the ocean basins. We predict carbonate melting in spatially heterogeneous patterns throughout the oceans. The rate of CO2 segregation from the mantle by off‐axis carbonate melting (~1.1 x 1012 mol/yr) is comparable to the global ridge flux (~1.2 x 1012 mol/yr). As the generation of carbonate melts should be enhanced in regions of mantle upwelling, we compare upwelling patterns with seismic detections of the G‐discontinuity. The upwelling velocities in areas where the G‐discontinuity is detected are not statistically different from areas with no detections–implying that the generation and pooling of carbonate melts are not dominant mechanisms in forming the G‐discontinuity. However, detections of a deeper seismic discontinuity are correlated with enhanced upwelling velocities, suggesting locally higher melt fractions at the transition between carbonate‐only and carbonate‐enhanced silicate melting.



1.Stitching Hope for the Coast–communicating coastal optimism for Louisiana

In March 2018, the Louisiana Universities Marine Consortium (LUMCON) hosted a gathering of thirty-seven scientists and science communicators for OCEANDOTCOMM, a collaborative storytelling event. The theme of the gathering, as well as what we were going to be asked to do, was not revealed by Executive Director Dr. Craig McClain until we arrived at the field station in Chauvin, LA. Drumroll, please…https://blogs.agu.org/geoedtrek/2018/07/17/stitching-hope-for-the-coast/

2.New magnetic anomaly map helps unveil Antarctica

The most comprehensive magnetic map of Antarctica ever produced was published online this week in a new studyin Geophysical Research Letters, a journal of the American Geophysical Union.The new map–which includes 3.5 million line-kilometers of magnetic anomaly data collected over the past 50 years–sheds new light on the structure and evolution of the Antarctic continent and its surrounding oceans.



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