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AGU Research Spotlight (Mar 30-Apr 04, 2018)

2018-04-06 08:50:11

I. Climate Change

1. Five Weird Archives That Scientists Use to Study Past Climates

When tree rings, ice cores, and cave formations can't cut it, try your luck with whale earwax or bat poop.


II. Hazards & Disasters

1. Are We Prepared for the Next Mega Eruption?

The frequency of eruptions with a Volcanic Explosivity Index of 7 is only one or two per thousand years but we cannot afford to be complacent.


III. Education

1. Virtual Mentoring Rewards Scientists at All Career Stages

Five geoscience organizations recently established an online global mentoring service for their disciplines.


IV. Geochemistry, Mineralogy, Volcanology

1. Diamond Impurities Reveal Water Deep Within the Mantle

A high-pressure form of ice, trapped within diamonds forged in the lower mantle, suggests that aqueous fluids reside deeper in Earth than we knew.


V. Hydrology, Cryosphere & Earth Surface

1. A City's Challenge of Dealing with Sea Level Rise

A well-developed case study in Ho-Chi Min City, Vietnam, exemplifies how other mega-cities located on deltas could face the major challenge of adapting to rising sea-level.


2.Coupled from the Start

Atmosphere and land model development has historically been segregated but coupled processes crucial to prediction and extremes can be properly represented only with a holistic approach.


VI. Geophysical Research Letters

1. Low‐Fe(III) Greenalite Was a Primary Mineral From Neoarchean Oceans

Banded iron formations (BIFs) represent chemical precipitation from Earth's early oceans and therefore contain insights into ancient marine biogeochemistry. However, BIFs have undergone multiple episodes of alteration, making it difficult to assess the primary mineral assemblage. Nanoscale mineral inclusions from 2.5 billion year old BIFs and ferruginous cherts provide new evidence that iron silicates were primary minerals deposited from the Neoarchean ocean, contrasting sharply with current models for BIF inception. Here we used multiscale imaging and spectroscopic techniques to characterize the best preserved examples of these inclusions. Our integrated results demonstrate that these early minerals were low‐Fe(III) greenalite. We present potential pathways in which low‐Fe(III) greenalite could have formed through changes in saturation state and/or iron oxidation and reduction. Future constraints for ancient ocean chemistry and early life's activities should include low‐Fe(III) greenalite as a primary mineral in the Neoarchean ocean.


2. Skilful Seasonal Predictions of Summer European Rainfall

Year‐to‐year variability in Northern European summer rainfall has profound societal and economic impacts; however, current seasonal forecast systems show no significant forecast skill. Here we show that skillful predictions are possible (r ~0.5, p < 0.001) using the latest high‐resolution Met Office near‐term prediction system over 1960–2017. The model predictions capture both low‐frequency changes (e.g., wet summers 2007–2012) and some of the large individual events (e.g., dry summer 1976). Skill is linked to predictable North Atlantic sea surface temperature variability changing the supply of water vapor into Northern Europe and so modulating convective rainfall. However, dynamical circulation variability is not well predicted in general—although some interannual skill is found. Due to the weak amplitude of the forced model signal (likely caused by missing or weak model responses), very large ensembles (>80 members) are required for skillful predictions. This work is promising for the development of European summer rainfall climate services.


3. Basal Settings Control Fast Ice Flow in the Recovery/Slessor/Bailey Region, East Antarctica

The region of Recovery Glacier, Slessor Glacier, and Bailey Ice Stream, East Antarctica, has remained poorly explored, despite representing the largest potential contributor to future global sea level rise on a centennial to millennial time scale. Here we use new airborne radar data to improve knowledge about the bed topography and investigate controls of fast ice flow. Recovery Glacier is underlain by an 800 km long trough. Its fast flow is controlled by subglacial water in its upstream and topography in its downstream region. Fast flow of Slessor Glacier is controlled by the presence of subglacial water on a rough crystalline bed. Past ice flow of adjacent Recovery and Slessor Glaciers was likely connected via the newly discovered Recovery‐Slessor Gate. Changes in direction and speed of past fast flow likely occurred for upstream parts of Recovery Glacier and between Slessor Glacier and Bailey Ice Stream. Similar changes could also reoccur here in the future.


4. A Possible Link Between Winter Arctic Sea Ice Decline and a Collapse of the Beaufort High?

A new study by Moore et al. (2018, https://doi.org/10.1002/2017GL076446) highlights a collapse of the anticyclonic “Beaufort High” atmospheric circulation over the western Arctic Ocean in the winter of 2017 and an associated reversal of the sea ice drift through the southern Beaufort Sea (eastward instead of the predominantly westward circulation). The authors linked this to the loss of sea ice in the Barents Sea, anomalous warming over the region, and the intrusion of low‐pressure cyclones along the eastern Arctic. In this commentary we discuss the significance of this observation, the challenges associated with understanding these possible linkages, and some of the alternative hypotheses surrounding the impacts of winter Arctic sea ice loss.


5. Solar Wind Deflection by Mass Loading in the Martian Magnetosheath Based on MAVEN Observations

Mars Atmosphere and Volatile EvolutioN observations at Mars show clear signatures of the shocked solar wind interaction with the extended oxygen atmosphere and hot corona displayed in a lateral deflection of the magnetosheath flow in the direction opposite to the direction of the solar wind motional electric field. The value of the velocity deflection reaches ~50 km/s. The occurrence of such deflection is caused by the “Lorentz‐type” force due to a differential streaming of the solar wind protons and oxygen ions originating from the extended oxygen corona. The value of the total deceleration of the magnetosheath flow due to mass loading is estimated as ~40 km/s.


6. Investigating Source Contributions of Size‐Aggregated Aerosols Collected in Southern Ocean and Baring Head, New Zealand using Sulfur Isotopes

Marine sulfate aerosols in the Southern Ocean are critical to the global radiation balance, yet the sources of sulfate and their seasonal variations are unclear. We separately sampled marine and ambient aerosols at Baring Head, New Zealand for one year using two collectors, and evaluated the sources of sulfate in coarse (1‐10 μm) and fine (0.05‐1 μm) aerosols using sulfur isotopes (δ34S). In both collectors, sea‐salt sulfate (SO42‐SS) mainly existed in coarse aerosols and non‐sea‐salt sulfate (SO42‐NSS) dominated the sulfate in fine aerosols, although some summer SO42‐NSS appeared in coarse particles due to aerosol coagulation. SO42‐NSS in the marine aerosols was mainly (88‐100%) from marine biogenic dimethylsulfide (DMS) emission, while the SO42‐NSS in the ambient aerosols was a combination of DMS (73‐79%) and SO2 emissions from shipping activities (~21‐27%). The seasonal variations of SO42‐NSS concentrations inferred from the δ34S values in both collectors were mainly controlled by the DMS flux.


7. Spatially‐Resolved Isotopic Source Signatures of Wetland Methane Emissions

We present the first spatially‐resolved wetland δ13C(CH4) source signature map based on data characterizing wetland ecosystems and demonstrate good agreement with wetland signatures derived from atmospheric observations. The source signature map resolves a latitudinal difference of ~10‰ between northern high‐latitude (mean ‐67.8‰) and tropical (mean ‐56.7‰) wetlands, and shows significant regional variations on top of the latitudinal gradient. We assess the errors in inverse modeling studies aiming to separate CH4 sources and sinks by comparing atmospheric δ13C(CH4) derived using our spatially‐resolved map against the common assumption of globally uniform wetland δ13C(CH4) signature. We find a larger interhemispheric gradient, a larger high‐latitude seasonal cycle and smaller trend over the period 2000‐2012. The implication is that erroneous CH4 fluxes would be derived to compensate for the biases imposed by not utilizing spatially‐resolved signatures for the largest source of CH4 emissions. These biases are significant when compared to the size of observed signals.


VII. AGU Blogs

1. Wider coverage of satellite data better detects magma supply to volcanoes

Using satellite imaging, researchers for the first time identified a major magma supply into a reservoir extending almost two miles from the crater of a volcano in Nicaragua.


2. Gavin Schmidt and Richard Alley’s Talk to a Full House at the Smithsonian

Anyone doing a presentation about Earth’s past climate has heard the same question. It goes something along the lines of: “How can you know what the weather was like ten thousand years ago? You weren’t there and neither was anyone else alive!”


3. NASA is for early-career, female scientists, too

When I tell someone that I’m part of a research team at NASA, I’m immediately met with stunned silence that is followed up with a confusing look. I wait, anticipating the inevitable question that arises as they look me up and down and say, “Wait, how old are you?” I sigh (inwardly) because, on the one hand, I can’t blame them. I admit I look about eighteen years old and honestly, I’m not much older than that. On the other hand, though, I am eager for the day to come when young, female scientists are accepted as they are without question.




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