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AGU Research Spotlight (Jul 20-Jul 26, 2017)

2017-07-28 11:13:06

I.Climate Change

1. Tiny Particles with Big Impact on Global Climate

A recent paper in Reviews of Geophysics suggests that new understandings of secondary organic aerosol may require a rethinking of atmospheric chemistry-climate models.


2. Antarctic Microbes Shape Nutrient Content of Snowmelt

As temperatures continue to rise, snow-dwelling microbes could accelerate melting and influence downstream ecosystems.


3. Tracking Water Through the North Atlantic Ocean

Workshop on Currents and Transports Across the Iceland-Faroe-Scotland Ridge; Tórshavn, Faroe Islands, 9–10 January 2017


II. Hazards & Disasters

1. Tsunami Records Show Increased Hazards for Chile’s Central Coast

Simulations of the historical quake raise new concerns: A similar event in the future could cause a devastating tsunami in Chile’s most populated coastal region.


2. The Value of Disaster Damage Data

The editors of a new book describe the benefits of systematic collection, storage, analysis, and sharing of damage data after flood events.


3. Volcano’s Toxic Plume Returns as Stealth Hazard

During a closely watched eruption, plumes of harmful sulfur dioxide gas morphed into “plumerangs” of sulfuric-acid-rich aerosols that descended on populated parts of Iceland.


III. Hydrology, Cryosphere & Earth Surface

1. Quantifying Coastal Rain Forest Carbon Transport

Aquatic Carbon Biogeochemistry of the Pacific Coastal Temperate Rainforest Region Workshop; Seattle, Washington, 7–10 February 2017


IV.Planetary Sciences

1. Saturn Unveiled: Ten Notable Findings from Cassini-Huygens

The soon-to-end NASA mission to Saturn changed the way we think of habitability beyond Earth, opened our eyes to dynamics in the gas giant’s atmosphere, and more.


V.Geophysical Research Letters

1. Simultaneous stabilization of global temperature and precipitation through cocktail geoengineering

Solar geoengineering has been proposed as a backup plan to offset some aspects of anthropogenic climate change if timely CO2 emission reductions fail to materialize. Modeling studies have shown that there are trade-offs between changes in temperature and hydrological cycle in response to solar geoengineering. Here we investigate the possibility of stabilizing both global mean temperature and precipitation simultaneously by combining two geoengineering approaches: stratospheric sulfate aerosol increase (SAI) that deflects sunlight to space and cirrus cloud thinning (CCT) that enables more longwave radiation to escape to space. Using the slab ocean configuration of National Center for Atmospheric Research Community Earth System Model, we simulate SAI by uniformly adding sulfate aerosol in the upper stratosphere and CCT by uniformly increasing cirrus cloud ice particle falling speed. Under an idealized warming scenario of abrupt quadrupling of atmospheric CO2, we show that by combining appropriate amounts of SAI and CCT geoengineering, global mean (or land mean) temperature and precipitation can be restored simultaneously to preindustrial levels. However, compared to SAI, cocktail geoengineering by mixing SAI and CCT does not markedly improve the overall similarity between geoengineered climate and preindustrial climate on regional scales. Some optimal spatially nonuniform mixture of SAI with CCT might have the potential to better mitigate climate change at both the global and regional scales.


2. Breaking of internal solitary waves generated by an estuarine gravity current

Mooring and ship-based data collected in a stratified estuary showed the generation of internal solitary waves by a bottom gravity current. Down-estuary winds drove a counterclockwise lateral circulation over channel-shoal bathymetry. When the lateral flows became supercritical, the pycnocline was sharply raised at the edge of the deep channel, leading to flow convergences and formation of a bottom gravity current. As the lateral circulation weakened during wind relaxation, the gravity current propagated onto the shoal and excited internal disturbances around its head. These disturbances evolved into a train of large-amplitude internal solitary waves that subsequently propagated ahead of the gravity current. The waves moving out of the gravity current broke, generating overturning and turbulence with energy dissipation rate reaching ~1 × 10?4 m2 s?3, 3 orders of magnitude larger than the background value. Our observations suggest that breaking internal waves may be an important source of turbulent mixing in stratified estuaries.


3. Stochastic modeling of interannual variation of hydrologic variables

Quantifying the interannual variability of hydrologic variables (such as annual flow volumes, and solute or sediment loads) is a central challenge in hydrologic modeling. Annual or seasonal hydrologic variables are themselves the integral of instantaneous variations and can be well approximated as an aggregate sum of the daily variable. Process-based, probabilistic techniques are available to describe the stochastic structure of daily flow, yet estimating interannual variations in the corresponding aggregated variable requires consideration of the autocorrelation structure of the flow time series. Here we present a method based on a probabilistic streamflow description to obtain the interannual variability of flow-derived variables. The results provide insight into the mechanistic genesis of interannual variability of hydrologic processes. Such clarification can assist in the characterization of ecosystem risk and uncertainty in water resources management. We demonstrate two applications, one quantifying seasonal flow variability and the other quantifying net suspended sediment export.


4. New methodology for computing tsunami generation by subaerial landslides: Application to the 2015 Tyndall Glacier landslide, Alaska

Landslide-generated tsunamis pose significant hazards and involve complex, multiphase physics that are challenging to model. We present a new methodology in which our depth-averaged two-phase model D-Claw is used to seamlessly simulate all stages of landslide dynamics as well as tsunami generation, propagation, and inundation. Because the model describes the evolution of solid and fluid volume fractions, it treats both landslides and tsunamis as special cases of a more general class of phenomena. Therefore, the landslide and tsunami can be efficiently simulated as a single-layer continuum with evolving solid-grain concentrations, and with wave generation via direct longitudinal momentum transfer—a dominant physical mechanism that has not been previously addressed in this manner. To test our methodology, we used D-Claw to model a large subaerial landslide and resulting tsunami that occurred on 17 October 2015, in Taan Fjord near the terminus of Tyndall Glacier, Alaska. Modeled shoreline inundation patterns compare well with those observed in satellite imagery.


5. Mass balance reassessment of glaciers draining into the Abbot and Getz Ice Shelves of West Antarctica

We present a reassessment of input-output method ice mass budget estimates for the Abbot and Getz regions of West Antarctica using CryoSat-2-derived ice thickness estimates. The mass budget is 8 ± 6 Gt yr?1 and 5 ± 17 Gt yr?1 for the Abbot and Getz sectors, respectively, for the period 2006–2008. Over the Abbot region, our results resolve a previous discrepancy with elevation rates from altimetry, due to a previous 30% overestimation of ice thickness. For the Getz sector, our results are at the more positive bound of estimates from other techniques. Grounding line velocity increases up to 20% between 2007 and 2014 alongside mean elevation rates of ?0.67 ± 0.13 m yr?1 between 2010 and 2013 indicate the onset of a dynamic thinning signal. Mean snowfall trends of ?0.33 m yr?1 water equivalent since 2006 indicate recent mass trends are driven by both ice dynamics and surface processes.


VI. AGU Blogs

1. NASA mission surfs through waves in space to understand space weather

The space surrounding our planet is full of restless charged particles and roiling electric and magnetic fields, which create waves around Earth. One type of wave, plasmaspheric hiss, is particularly important for removing charged particles from the Van Allen radiation belts, a seething coil of particles encircling Earth, which can interfere with satellites and telecommunications. A new study in the Journal of Geophysical Research: Space Physics, a journal of the American Geophysical Union, used data from NASA’s Van Allen Probes spacecraft to discover that hiss is more complex than previously understood.


2. Humanizing scientists via #AlongsideScience

I’m a morning person. I wake up early during the week to run/bike/go to the gym before I go to work. On the weekends, I still wake up fairly early, either to go for a run or a long bike ride, or to just sit with a coffee, the Washington Post (that I do actually get in print), and to peruse Twitter. Since I primarily follow mostly scientists or science-related accounts on Twitter, Saturday and Sunday morning tweets are usually pretty sparse. However, this Saturday I woke up to (yet another) a science-twitter-hashtag-phenomenon.


3. Could “cocktail geoengineering” save the climate?

Geoengineering is a catch-all term that refers to various theoretical ideas for altering Earth’s energy balance to combat climate change. Newresearch from an international team of atmospheric scientists published by Geophysical Research Lettersinvestigates for the first time the possibility of using a “cocktail” of geoengineering tools to reduce changes in both temperature and precipitation caused by atmospheric greenhouse gases.


4. Mountain glaciers recharge vital aquifers

Small mountain glaciers play a big role in recharging vital aquifers and in keeping rivers flowing during the winter, according to a new studypublished in Geophysical Research Letters, a journal of the American Geophysical Union.




WASHINGTON, DC—The American Geophysical Union (AGU) has selected its 2017 class of medalists, awardees, and prize recipients. Twenty-nine individuals are recognized this year for their dedication to science for the benefit of humanity and their achievements in Earth and space science.



WASHINGTON, D.C. — Three journalists are being awarded top honors from the American Geophysical Union this year for their reporting on the Earth and space sciences.



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