I. Atmospheric Sciences

1.A Decade of Progress in Stratospheric Aerosol Research

New observations and understanding of stratospheric particles are crucial for evaluating their role in climate change.

II. Geology & Geophysics

1.What Makes Long-Runout Landslides So Mobile?

The seismologists of the world want to turn you into an earthquake detector.

3.A Hole in Earth's Surface

Would communicating science be more effective if geoethics were included in the discussion?

IV. Ocean Sciences

1. What Causes Long-Term North Atlantic Surface Temperature Cycles?

Satellite data, field measurements, and readings from "snow buoys" reveal ice thickness patterns similar to those preceding the lowest recorded sea ice extent, which was reached nearly 4 years ago.

VI. Space & Planets

1.Electrons Thrown Off Course in Near-Earth Magnetic Reconnection

Countries ratifying the Paris climate agreement need strong financial incentives to convince them to choose renewables over fossil fuels, according to World Bank president.

2.New Climate Studies: Worse Risks at 2°C Rise, Higher Rise Likely

Moniz foresees progress on climate change in the United States no matter who wins the U.S. presidential election.

4.Challenges and Opportunities in Earth-Human Systems Research

Scientists spot the "stem cell" building blocks that lay the foundation for gypsum's formation.

IX. Space Science & Space Physics

1.Ionospheric Waves Linked to Polar Atmospheric Dynamics

New research finds exhaust from idling diesel engines produces a significant amount of isocyanic acid when photons from sunlight help it react with other compounds in the atmosphere. The amount of this secondary photochemical isocyanic acid produced by non-road, idling diesel engines, like those in tractors, loaders, and other heavy construction and farm equipment, was 50 to 230 milligrams per kilogram of diesel burned, according to the new study. That comes to about 150 to 700 milligrams per gallon burned. That’s also two to six times greater than the amount of isocyanic acid produced by diesel engines running at higher speed and under a load, like cars and trucks driving on a highway, the new research found.

2.Action on climate change needs our hearts and heads: uniting our faith and science

On the morning of the 19th, the R/V Falkor entered harbor in the country of Tonga after nearly 12 days at sea. As we stood on the deck watching the dockworkers heave lines to and fro, several scientists breathed a sigh of relief, for we had spent a number of days being tossed around by the sea. It was by no means a severe beating, and the R/V Falkor is known for her ability to move swiftly and steadily through waves and swells. Still, if one is susceptible to seasickness, being in harbor or on land is a pleasant respite.

4.Asian irrigation influences East African rain1. Laboratory measurements of heterogeneous CO2ice nucleation on nanoparticles under conditions relevant to the Martian mesosphere

Clouds of CO2 ice particles have been observed in the Martian mesosphere. These clouds are believed to be formed through heterogeneous nucleation of CO2 on nanometer-sized meteoric smoke particles (MSPs) or upward propagated Martian dust particles (MDPs). Large uncertainties still exist in parameterizing the microphysical formation process of these clouds as key physico-chemical parameters are not well known. We present measurements on the nucleation and growth of CO2 ice on sub 4nm radius iron oxide and silica particles representing MSPs at conditions close to the mesosphere of Mars. For both particle materials we determine the desorption energy of CO2 to be∆Fdes=(18.5±0.2)kJmol−1 corresponding to∆Fdes=(0.192±0.002)eV and obtain m=0.78±0.02 for the contact parameter that governs heterogeneous nucleation by analyzing the measurements using classical heterogeneous nucleation theory. We did not find any temperature dependence for the contact parameter in the temperature range examined (64K to 73K). By applying these values for MSPs in the Martian mesosphere, we derive characteristic temperatures for the onset of CO2 ice nucleation, which are 8 - 18K below the CO2 frost point temperature, depending on particle size. This is in line with the occurrence of highly supersaturated conditions extending to 20K below frost point temperature without the observation of clouds. Moreover, the sticking coefficient of CO2 on solid CO2 was determined to be near unity. We further argue that the same parameters can be applied to CO2 nucleation on upward propagated MDPs.

The emergence of the Central American isthmus occurred episodically from Eocene to Pliocene time and was caused by a series of tectonic and volcanic processes. Results from zircon U-Pb geochronology, zircon (U-Th)/He (ZHe) and apatite (U-Th)/He (AHe) thermochronology, and zircon Lu-Hf isotopic data from sedimentary (sandstones and recent river sands) and plutonic rocks from the Azuero Peninsula and Central Panama document the exhumation and uplift history of the Panamanian basement complex. Our data supports previous paleobotanical and thermochronological studies that suggest that by middle Eocene time some areas of Central Panama and Azuero Peninsula were exposed above sea level as a series of islands surrounded by shallow open marine waters. The Gatuncillo, Cobachón and Tonosí formations were deposited during this partial emergence. Transtension in the Oligocene-early Miocene produced various pull-apart basins (e.g., the Canal Basin) and local uplift that exhumed the Eocene strata (Gatuncillo and Cobachón formations). This event probably reduced circulation between the Pacific Ocean and the Caribbean Sea. The Tonosí Formation records late Miocene to Pleistocene cooling and exhumation, which may be related to uplift above the subducting Coiba Ridge. These results suggest that the emergence of the Isthmus of Panama followed a series of diachronous events that led to the final closure of the Central American seaway. This article is protected by copyright. All rights reserved.

4. Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism

The Lightning and Sprites Observation (LSO) experiment was designed to test a new concept of nadir-viewing sprite measurement on board the International Space Station using spectral differentiation methods for lightning and sprite identification. It was composed of two calibrated cameras: one equipped with a narrowband filter at 763 nm to maximize the contrast between sprites and lightning, and the other to monitor lightning. The LSO was operated at night during 15 days from 2001 to 2004 during which 197 lightning flashes, several sprites, hundreds of gas flares, and tens of cities were analyzed. The main strength of this experiment was its high spatial resolution of about 400 m. The structural details of some lightning are thus observed highlighting complex systems. Some features such as the nonlinear increase of the lightning-illuminated cloud top area with the peak radiance and the radial decrease of the lightning flash radiance were quantified. The median area is 129 km2 with median minor and major axes of 12 and 16 km. Two methods of sprite identification are presented and applied to the most intense sprite events observed by LSO. The sprite diameter is 5 km and it is shifted of about 22 km from the center of the parent lightning. A ratio of 1.7% is deduced for lightning flashes between the radiances measured by both cameras. These observations should be useful for the preparation or the analysis of future space missions dedicated to nadir-viewing observations of sprites.

6. Orbital evidence for more widespread carbonate-bearing rocks on Mars<span " style="font-size:16.0pt">

Carbonates are key minerals for understanding ancient Martian environments because they are indicators of potentially habitable, neutral-to-alkaline water and may be an important reservoir for paleoatmospheric CO2. Previous remote sensing studies have identified mostly Mg-rich carbonates, both in Martian dust and in a Late Noachian rock unit circumferential to the Isidis basin. Here we report evidence for older Fe- and/or Ca-rich carbonates exposed from the subsurface by impact craters and troughs. These carbonates are found in and around the Huygens basin northwest of Hellas, in western Noachis Terra between the Argyre basin and Valles Marineris, and in other isolated locations spread widely across the planet. In all cases they cooccur with or near phyllosilicates, and in Huygens basin specifically they occupy layered rocks exhumed from up to ~5 km depth. We discuss factors that might explain their observed regional distribution, arguments for why carbonates may be even more widespread in Noachian materials than presently appreciated and what could be gained by targeting these carbonates for further study with future orbital or landed missions to Mars.

XII.AUG Newsroom

1. ONE OIL FIELD A KEY CULPRIT IN GLOBAL ETHANE GAS INCREASE

WASHINGTON, DC — A single U.S. shale oil field is responsible for much of the past decade’s increase in global atmospheric levels of ethane, a gas that can damage air quality and impact climate, according to new study. The researchers found that the Bakken Formation, an oil and gas field in North Dakota and Montana, is emitting roughly 2 percent of the globe’s ethane. That’s about 230,000 metric tons (250,000 U.S. tons) per year.

2. A THIRD OF THE WORLD’S BIGGEST GROUNDWATER BASINS ARE IN DISTRESS

WASHINGTON, D.C. – Human consumption is rapidly draining about a third of its largest groundwater basins, despite having little to no accurate data about how much water remains in them, according to two new studies led by the University of California, Irvine, using data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites. The result is that significant segments of Earth’s population are consuming groundwater quickly without knowing when it might run out, the researchers conclude. The new findings have been accepted for publication in Water Resources Research, a journal of the American Geophysical Union, and appear online today.

3. UNHEALTHY OZONE DAYS COULD INCREASE BY MORE THAN A WEEK IN COMING DECADES

WASHINGTON, DC — If emission rates continue unchecked, regions of the United States could experience between three and nine additional days per year of unhealthy ozone levels by 2050, according to a new study.