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AGU Research Spotlight (Feb 15-Feb 21, 2018)

2018-02-22 18:34:48

I. Space & Planets

1. Modeling Geospace: Quantifying the Known-Unknowns

Imperfect knowledge of high-latitude forcing of the coupled ionosphere-theremosphere system translates into uncertainty in the low-latitude and midlatitude response to a geomagnetic storm.


2. Planetary Dune Workshop Expands to Include Subaqueous Processes

The Fifth International Planetary Dunes Workshop: From the Bottom of the Oceans to the Outer Limits of the Solar System; St. George, Utah, 16–19 May 2017


3. Long Term Preservation of Subsurface Ice on Mars

Layered-ejecta craters on Mars that are associated with impacts into rock mixed with volatiles have been formed throughout the planet’s history indicating the long-term preservation of subsurface ice.


II. Hazards & Disasters

1. Monitoring Tropical Cyclones with Lightning and Satellite Data

A new storm-following tool continually watches for lightning over the open ocean. Combined with satellite microwave data, the new real-time observations will improve forecasts of tropical cyclones.


2.The Challenges of Drought Prediction

Advances in dynamical modeling and the use of hybrid methods have improved drought prediction, but challenges still remain to improve the accuracy of drought forecasting.


III. Ocean Sciences

1. Ocean Tides Affect Ice Loss from Large Polar Ice Sheets

A recent paper in Reviews of Geophysics discusses how ocean tides affect the motion of, and loss of ice from, the Antarctic and Greenland ice sheets.


IV. Biogeosciences

1. U.S. and China Assess Ecosystem Effects of a Fading Cryosphere

Impacts of a Changing Cryosphere on Lakes and Streams in Mountain Regions: US-China Collaborative Workshop at Qinghai Lake; Qinghai, China, 21–27 August 2017


V. Geology & Geophysics

1. Untangling Sediment Transport Through River Networks

A stochastic sediment routing model for river networks is inverted to determine sediment source areas based on point observations of grain size and sediment flux at the basin outlet.


VI. Geophysical Research Letters

1.Irrigation as a Potential Driver for Anomalous Glacier Behavior in High Mountain Asia

Many glaciers in the northwest of High Mountain Asia (HMA) show an almost zero or positive mass balance, despite the global trend of melting glaciers. This phenomenon is often referred to as the “Karakoram anomaly,” although strongest positive mass balances can be found in the Kunlun Shan mountain range, northeast of the Karakoram. Using a regional climate model, in combination with a moisture-tracking model, we show that the increase in irrigation intensity in the lowlands surrounding HMA, particularly in the Tarim basin, can locally counter the effects of global warming on glaciers in Kunlun Shan, and parts of Pamir and northern Tibet, through an increase in summer snowfall and decrease in net radiance. Irrigation can thus affect the regional climate in a way that favors glacier growth, and future projections of glacier melt, which may impact millions of inhabitants surrounding HMA, will need to take into account predicted changes in irrigation intensity.


2. Ion Acceleration by Flux Transfer Events in the Terrestrial Magnetosheath

We report ion acceleration by flux transfer events in the terrestrial magnetosheath in a global two-dimensional hybrid-Vlasov polar plane simulation of Earth's solar wind interaction. In the model we find that propagating flux transfer events created in magnetic reconnection at the dayside magnetopause drive fast-mode bow waves in the magnetosheath, which accelerate ions in the shocked solar wind flow. The acceleration at the bow waves is caused by a shock drift-like acceleration process under stationary solar wind and interplanetary magnetic field upstream conditions. Thus, the energization is not externally driven but results from plasma dynamics within the magnetosheath. Energetic proton populations reach the energy of 30 keV, and their velocity distributions resemble time-energy dispersive ion injections observed by the Cluster spacecraft in the magnetosheath.


3. Evidence for Diverse Biogeochemical Drivers of Boreal Forest New Particle Formation

New particle formation (NPF) is an important contributor to particle number in many locations, but the chemical drivers for this process are not well understood. Daytime NPF events occur regularly in the springtime Finnish boreal forest and strongly impact aerosol abundance. In April 2014 size-resolved chemical measurements of ambient nanoparticles were made using the Time-of-Flight Thermal Desorption Chemical ionization Mass Spectrometer and we report results from two NPF events. While growth overall was dominated by terpene oxidation products, newly formed 20–70 nm particles showed enhancement in apparent alkanoic acids. The events occurred on days with rapid transport of marine air, which correlated with low background aerosol loading and higher gas phase methanesulfonic acid levels. These results are broadly consistent with previous studies on Nordic NPF but indicate that further attention should be given to the sources and role of non-terpenoid organics and the possible contribution of transported marine compounds in this process.


4. Arctic Sea Ice in a 1.5°C Warmer World

We examine the seasonal cycle of Arctic sea ice in scenarios with limited future global warming. To do so, we analyze two sets of observational records that cover the observational uncertainty of Arctic sea ice loss per degree of global warming. The observations are combined with 100 simulations of historical and future climate evolution from the Max Planck Institute Earth System Model Grand Ensemble. Based on the high-sensitivity observations, we find that Arctic September sea ice is lost with low probability (P≈ 10%) for global warming of +1.5°C above preindustrial levels and with very high probability (P> 99%) for global warming of +2°C above preindustrial levels. For the low-sensitivity observations, September sea ice is extremely unlikely to disappear for +1.5°C warming (P? 1%) and has low likelihood (P≈ 10%) to disappear even for +2°C global warming. For March, both observational records suggest a loss of 15% to 20% of Arctic sea ice area for 1.5°C to 2°C global warming.


5. Maritime NOx Emissions Over Chinese Seas Derived From Satellite Observations

By applying an inversion algorithm to NOx satellite observations from Ozone Monitoring Instrument, monthly NOx emissions for a 10 year period (2007 to 2016) over Chinese seas are presented for the first time. No effective regulations on NOxemissions have been implemented for ships in China, which is reflected in the trend analysis of maritime emissions. The maritime emissions display a continuous increase rate of about 20% per year until 2012 and slow down to 3% after that. The seasonal cycle of shipping emissions has regional variations, but all regions show lower emissions during winter. Simulations by an atmospheric chemistry transport model show a notable influence of maritime emissions on air pollution over coastal areas, especially in summer. The satellite-derived spatial distribution and the magnitude of maritime emissions over Chinese seas are in good agreement with bottom-up studies based on the Automatic Identification System of ships.


6. Physical Explanation of Archie's Porosity Exponent in Granular Materials: A Process-Based, Pore-Scale Numerical Study

The empirical Archie's law has been widely used in geosciences and engineering to explain the measured electrical resistivity of many geological materials, but its physical basis has not been fully understood yet. In this study, we use a pore-scale numerical approach combining discrete element-finite difference methods to study Archie's porosity exponent m of granular materials over a wide porosity range. Numerical results reveal that at dilute states (e.g., porosity ? > ~65%), m is exclusively related to the particle shape and orientation. As the porosity decreases, the electric flow in pore space concentrates progressively near particle contacts and mincreases continuously in response to the intensified nonuniformity of the local electrical field. It is also found that the increase in m is universally correlated with the volume fraction of pore throats for all the samples regardless of their particle shapes, particle size range, and porosities.


VII. AGU Blogs

1. Friday fold: Zerrissene turbidite system, Namibia

Today we get to look at some spectacular folds from Namibia’s Zerrissene turbidite system, courtesy of my friend Jay Kaufman of the University of Maryland, College Park. He scanned some of his old slides to share some on-the-ground visions of this incredible place with us


2. Other Minds, by Peter Godfrey-Smith

The Octopus, the Sea, and the Deep Origins of Consciousness is the subtitle of this fascinating, extremely approachable book. Paraphrasing Thomas Nagle, it asks “What is it like to be an octopus?” The author is a philosopher by training, but he does a fantastic job as a science writer, too. Anecdotes about encounters with cephalopods while diving are mixed with careful, deliberate, dejargonized descriptions of the scientific studies that have illuminated the evolution of minds. While we know that dolphins and chimpanzees and parrots are smart, they are all united in being vertebrates with a similarly-organized nervous system. Cuttlefish, squid, and octopuses are however much more distantly related (we share a common ancestor something like 550-600 million years ago), and yet they have independently evolved a remarkable intelligence.


3.Found: “Footprint” of Jupiter’s moon Callisto

The elusive “footprint” of Jupiter’s moon Callisto has been spotted for the first time near the south pole of the giant planet, according to a new study.


4. First satellite images of the Puerto Venus debris flows

Yesterday I highlighted the Puerto Venus debris flows that struck a rural community in Colombia last week, destroying a number of houses.  Whilst loss of life was avoided, the events caused significant damage.  They were also caught on some remarkable videos, which I included in my post.  There was speculation yesterday that the landslides had been caused by a the breach of a valley blocking landslide upstream near to El Pinal, but of course this can only be confirmed via satellite imagery or by fieldwork.  I have taken a look at the Planet Labs images of the area affected by the debris flows.  Whilst we are still waiting for a cloud-free image (challenging in this area at this time of year), these are quite informative.  The image below, collected by Planet Labs (and used with permission) with a 3 m resolution before the debris flows, shows the catchment above Puerto Venus, from which the debris flows originated.


5. Puerto Venus: massive debris flows in Colombia yesterday

The municipality of Narino in Antioquia in Colombia was affected by large debris flows, triggered by heavy rainfall, late last week.  Worst affected appears to be the village of Puerto Venus, which was struck by a large debris flow, destroying 12 houses.  The debris flow was captured in two remarkable videos that have been posted to Youtube.  This one shows the debris flow from one side of the river.



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