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AGU Research Spotlight (Feb 03-Feb 08, 2017)

2017-02-09 15:51:49

I.Atmospheric Sciences

1. Good Night Sunshine: Geoengineering Solutions to Climate Change?

In order to limit global warming to Paris Agreement goal levels, climate engineering should be considered as a viable solution.


2. Clouds Don't Reflect as Much Sunlight as Previously Thought

Icy clouds may actually increase, not decrease, the amount of solar energy that reaches Earth.


II.Space & Planets

1. New Research Shows Ceres May Have Vanishing Ice Volcanoes

The findings could help scientists better decipher the history of how the dwarf planet formed.


2. GPS Data Release to Boost Space-Weather Science

"Unprecedented" data key to understanding radiation threats to satellites, infrastructure


III.Hydrology, Cryosphere & Earth Surface

1. New Ground-Penetrating Radar Method Shows Promise in Aquifer

Recent advances in ground-penetrating radar data analysis could help reveal aquifer structure in unprecedented detail.


2. International Effort Tackles Landslide Hazards to Keep the Peace

Earth scientists work with the North Atlantic Treaty Organization to help keep a border-straddling hydroelectric power plant on the Black Sea coast safe from landslides.


IV. Global Change

1. Initiative Aims to Help Cut Losses from Extreme Weather Events

A new alliance aims to integrate social and behavioral science into meteorological research and practice to help build resilience to natural disasters.


V. Ocean Sciences

1. Tiny Creatures Form Massive, Bright Ring Around Antarctica

Dense algae populations in the Great Calcite Belt could cause carbon dioxide release from the ocean into the atmosphere.


2.An Up Close Look at the Megaquakes That Cause Tsunamis

Researchers recreate changes in the seafloor during Japan's devastating 2011 tsunami.


VI. Geophysical Research Letters

1. Suppressing breakers with polar oil films: Using an epic sea rescue to model wave energy budgets

Oil has been used to still stormy seas for centuries, but the mechanisms are poorly understood. Here we examine the processes by using quantitative information from a remarkable 1883 sea rescue where oil was used to reduce large breakers during a storm. Modeling of the oil film's extent and waves under the film suggests that large breakers were suppressed by a reduction of wind energy input. Modification of surface roughness by the film is hypothesized to alter the wind profile above the sea and the energy flow. The results are central to understanding air-sea momentum exchange, including its role in such processes as cyclone growth and storm surge, although they address only one aspect of the complex problem of wind interaction with the ocean surface.


2. Modulation of air-sea fluxes by extratropical planetary waves and its impact during the recent surface warming slowdown

It is widely accepted that natural decadal variability played a major role in the slowdown in global warming observed in the 21st century, with sea surface cooling in the tropical Pacific recognized as a major contributor. However, the warming pause was most pronounced during boreal winter, with Northern Hemisphere flow anomalies also playing a role. Here we quantify the contribution of extratropical heat exchanges by comparing geopotential and temperature anomalies simulated by ensembles of seasonal forecasts with similar ocean temperature but different heat fluxes north of 40°N, as a result of planetary wave variability. We show that an important part of heat flux anomalies is associated with decadal variations in the phase of a specific planetary wave pattern. In model simulations covering the last three decades, this variability pattern accounts for a decrease of 0.35°C/decade in the post-1998 wintertime temperature trend over northern continents.


3. Bounds on the calving cliff height of marine terminating glaciers

Increased calving and rapid retreat of glaciers can contribute significantly to sea level rise, but the processes controlling glacier retreat remain poorly understood. We seek to improve our understanding of calving by investigating the stress field controlling tensile and shear failure using a 2-D full-Stokes finite element model. Using idealized rectangular geometries, we find that when rapidly sliding glaciers thin to near buoyancy, full thickness tensile failure occurs, similar to observations motivating height-above-buoyancy calving laws. In contrast, when glaciers are frozen to their beds, basal crevasse penetration is suppressed and calving is minimal. We also find that shear stresses are largest when glaciers are thickest. Together, the tensile and shear failure criteria map out a stable envelope in an ice-thickness-water-depth diagram. The upper and lower bounds on cliff height can be incorporated into numerical ice sheet models as boundary conditions, thus bracketing the magnitude of calving rates in marine-terminating glaciers.


4. Methodology to create a new total solar irradiance record: Making a composite out of multiple data records

Many observational records critically rely on our ability to merge different (and not necessarily overlapping) observations into a single composite. We provide a novel and fully traceable approach for doing so, which relies on a multiscale maximum likelihood estimator. This approach overcomes the problem of data gaps in a natural way and uses data-driven estimates of the uncertainties. We apply it to the total solar irradiance (TSI) composite, which is currently being revised and is critical to our understanding of solar radiative forcing. While the final composite is pending decisions on what corrections to apply to the original observations, we find that the new composite is in closest agreement with the PMOD composite and the NRLTSI2 model. In addition, we evaluate long-term uncertainties in the TSI, which reveal a 1/fscaling.


5.Cross-Saharan transport of water vapor via recycled cold pool outflows from moist convection

Very sparse data have previously limited observational studies of meteorological processes in the Sahara. We present an observed case of convectively driven water vapor transport crossing the Sahara over 2.5?days in June 2012, from the Sahel in the south to the Atlas in the north. A daily cycle is observed, with deep convection in the evening generating moist cold pools that fed the next day's convection; the convection then generated new cold pools, providing a vertical recycling of moisture. Trajectories driven by analyses were able to capture the direction of the transport but not its full extent, particularly at night when cold pools are most active, and analyses missed much of the water content of cold pools. The results highlight the importance of cold pools for moisture transport, dust and clouds, and demonstrate the need to include these processes in models in order to improve the representation of Saharan atmosphere.


6. On the role of ice-nucleating aerosol in the formation of ice particles in tropical mesoscale convective systems

Over the decades, the cloud physics community has debated the nature and role of aerosol particles in ice initiation. The present study shows that the measured concentration of ice crystals in tropical mesoscale convective systems exceeds the concentration of ice nucleating particles (INPs) by several orders of magnitude. The concentration of INPs was assessed from the measured aerosol particle concentration in the size range of 0.5 to 1?μm. The observations from this study suggest that primary ice crystals formed on INPs make only a minor contribution to the total concentration of ice crystals in tropical mesoscale convective systems. This is found by comparing the predicted INP number concentrations with in situ ice particle number concentrations. The obtained measurements suggest that ice multiplication is the likely explanation for the observed high concentrations of ice crystals in this type of convective system.


7. Bathymetry of the Amundsen Sea Embayment sector of West Antarctica from Operation IceBridge gravity and other data

We employ airborne gravity data from NASA's Operation IceBridge collected in 2009–2014 to infer the bathymetry of sub–ice shelf cavities in front of Pine Island, Thwaites, Smith, and Kohler glaciers, West Antarctica. We use a three-dimensional inversion constrained by multibeam echo sounding data offshore and bed topography from a mass conservation reconstruction on land. The seamless bed elevation data refine details of the Pine Island sub–ice shelf cavity, a slightly thinner cavity beneath Thwaites, and previously unknown deep (>1200 m) channels beneath the Crosson and Dotson ice shelves that shallow (500 m and 750 m, respectively) near the ice shelf fronts. These sub–ice shelf channels define the natural pathways for warm, circumpolar deep water to reach the glacier grounding lines, melt the ice shelves from below, and constrain the pattern of past and future glacial retreat.



1. Analysis of 1883 at-sea rescue leads to new understanding of wave energy

A team of oceanographers has developed a new model for ocean wave energy, using an 1883 account of how a ship’s crew dumped oil into stormy seas and calmed the waves enough to save the crew of a sinking ship.


2. Greener cities could help urban plants endure summer heat

Urban plants offer city dwellers many benefits, such as improved health and decreased crime and pollution. And now we have even more reason to green our cities. A new study from the Water Sustainability and Climate project at the University of Wisconsin-Madison indicates that adding more greenery to the urban landscape could help urban vegetation cope better with the summer heat and a warming climate. In other words, the more plants in a city, the merrier they all are.


3. New climate index based on atmospheric pressure produces more accurate predictions of storm wave conditions

A method based on the north-south atmospheric pressure gradient along the Atlantic coast of Europe could lead to enhanced forecasting of extreme wave conditions and increased preparedness within coastal communities, a new study suggests.


4. Coal mine dust lowers spectral reflectance of Arctic snow by up to 84 percent, new study finds

Dust released by an active coal mine in Svalbard, Norway reduced the spectral reflectance of nearby snow and ice by up to 84 percent, according to new research.


IX. AGU News


WASHINGTON, DC — A recently discovered solitary ice volcano on the dwarf planet Ceres may have some hidden older siblings, say scientists who have tested a likely way such mountains of icy rock – called cryovolcanoes – might disappear over millions of years.



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