AGU期刊一周Research Spotlight (March 17~ March 23, 2017)

发布时间:2017-3-24 8:49:23 点击次数:356

I. Atmospheric Sciences

1. Last Remnant of North American Ice Sheet to Vanish in 300 Years

New study provides compelling evidence that the current level of Arctic warming is almost unprecedented in the past 2.5 million years.

2. Mars Polar Intrigue Spurs Multidisciplinary Collaboration

Sixth International Conference on Mars Polar Science and Exploration; Reykjavík, Iceland; 5–9 September 2016

3. Study Finds Hotspots of Ammonia over World's Major Farming Areas

In the U.S., efforts to curb acid rain in the 1990s had the unintended effect of increasing ammonia in the atmosphere.

4. EPA Reassesses Feasibility of Plan to Increase Fuel Efficiency

This January, the Environmental Protection Agency (EPA) finalized mileage standards set in 2012. Now, at the push of the auto industry, EPA and other agencies are going back for another look.

II. Science Policy

1. White House Budget Plan Slams Climate and Environmental Programs

The spending blueprint unveiled yesterday precedes a detailed budget proposal expected later this spring. Democrats declared the newly released plan "dead on arrival."

2. Republican Resolution Urges Congress to Counter Climate Threat

The bill calls for using American ingenuity and innovation to find solutions to changes in global and regional climates but makes no mention of fossil fuel emissions.

III. Hydrology, Cryosphere & Earth Surface

1. Mapping the Topographic Fingerprints of Humanity Across Earth

If increasingly globalized societies are to make better land management decisions, the geosciences must globally evaluate how humans are reshaping Earth's surface

IV. Hazards & Disasters

1. What Caused the Fatal 2014 Eruption of Japan's Mount Ontake?

Analysis of the change in the stratovolcano's tilt just prior to the explosion suggests that the cracking of a previously intact fluid barrier caused the country's deadliest eruption since 1926.

2. Water Quality Database Offers New Tools to Study Aquatic Systems

Researchers assess the federal Water Quality Portal, a Web portal that unites disparate water quality data sets and resources.

V. Ocean Sciences

1. Sun Glitter Provides a Detailed Map of Ocean Waves

European scientists use satellite sensors to detect light reflected off waves at the ocean's surface, which could help improve wave forecasts.

2. Study Finds That Coastal Wetlands Excel at Storing Carbon

Shoreline environments show more promise than other marine ecosystems for mitigating climate change, the analysis shows.

VI. Geophysical Research Letters

1. The nitrate/(per)chlorate relationship on Mars

Nitrate was recently detected in Gale Crater sediments on Mars at abundances up to ~600 mg/kg, confirming predictions of its presence at abundances consistent with models based on impact-generated nitrate and other sources of fixed nitrogen. Terrestrial Mars analogs, Mars meteorites, and other solar system materials help establish a context for interpreting in situ nitrate measurements on Mars, particularly in relation to other cooccuring salts. We compare the relative abundance of nitrates to oxychlorine (chlorate and/or perchlorate, hereafter (per)chlorate) salts on Mars and Earth. The nitrate/(per)chlorate ratio on Mars is < 1, significantly lower than on Earth (nitrate/(per)chlorate > 103), suggesting not only the absence of biological activity but also different (per)chlorate formation mechanisms on Mars than on Earth.

2. Enabling large-scale viscoelastic calculations via neural network acceleration

One of the most significant challenges involved in efforts to understand the effects of repeated earthquake cycle activity is the computational costs of large-scale viscoelastic earthquake cycle models. Computationally intensive viscoelastic codes must be evaluated at thousands of times and locations, and as a result, studies tend to adopt a few fixed rheological structures and model geometries and examine the predicted time-dependent deformation over short (<10 years) time periods at a given depth after a large earthquake. Training a deep neural network to learn a computationally efficient representation of viscoelastic solutions, at any time, location, and for a large range of rheological structures, allows these calculations to be done quickly and reliably, with high spatial and temporal resolutions. We demonstrate that this machine learning approach accelerates viscoelastic calculations by more than 50,000%. This magnitude of acceleration will enable the modeling of geometrically complex faults over thousands of earthquake cycles across wider ranges of model parameters and at larger spatial and temporal scales than have been previously possible.

3. Global-scale river network extraction based on high-resolution topography and constrained by lithology, climate, slope, and observed drainage density

To improve the representation of surface and groundwater flows, global land surface models rely heavily on high-resolution digital elevation models (DEMs). River pixels are routinely defined as pixels with drainage areas that are greater than a critical drainage area (Acr). This parameter is usually uniform across the globe, and the dependence of drainage density on many environmental factors is often overlooked. Using the 15″ HydroSHEDS DEM as an example, we propose the calibration of a spatially variable Acr as a function of slope, lithology, and climate, to match drainage densities from reference river networks at a 1:50,000 scale in France and Australia. Two variable Acr models with varying complexities were derived from the calibration, with satisfactory performances compared to the reference river networks. Intermittency assessment is also proposed. With these simple tools, river networks with natural heterogeneities at the 1:50,000 scale can be extracted from any DEM.

4. Anatomy of a late spring snowfall on sea ice

Spring melt initiation is a critical process for Arctic sea ice. Melting conditions decrease surface albedo at a time of high insolation, triggering powerful albedo feedback. Weather events during melt initiation, such as new snowfalls, can stop or reverse the albedo decline, however. Here we present field observations of such a snow event and demonstrate its enduring impact through summer. Snow fell 3–6 June 2014 in the Chukchi Sea, halting melt onset. The snow not only raised albedo but also provided a significant negative latent heat flux, averaging -51 W m−2 from 3 to 6 June. The snowfall delayed sustained melt by 11 days, creating cascading impacts on surface energy balance that totaled some 135 MJ/m2 by mid-August. The findings highlight the sensitivity of sea ice conditions on seasonal time scales to melt initiation processes.

5. Increased atmospheric ammonia over the world's major agricultural areas detected from space

This study provides evidence of substantial increases in atmospheric ammonia (NH3) concentrations (14 year) over several of the worlds major agricultural regions, using recently available retrievals from the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite. The main sources of atmospheric NH3 are farming and animal husbandry involving reactive nitrogen ultimately derived from fertilizer use; rates of emission are also sensitive to climate change. Significant increasing trends are seen over the U.S. (2.61% yr−1), the European Union (EU) (1.83% yr−1), and China (2.27% yr−1). Over the EU, the trend results from decreased scavenging by acid aerosols. Over the U.S., the increase results from a combination of decreased chemical loss and increased soil temperatures. Over China, decreased chemical loss, increasing temperatures, and increased fertilizer use all play a role. Over South Asia, increased NH3 emissions are masked by increased SO2 and NOx emissions, leading to increased aerosol loading and adverse health effects.

VII. AGU Blogs

1. Can You See The Equinox from Space? Yes!

The Equinox was at 10:29 GMT or 6:29 AM EDT this morning, and yes it is visible from space. The terminator between light and dark is exactly due north/south on the equinoxes, and you can see that this is indeed the case from the image above. The line will tilt to the right at exactly 23.5 degrees by the summer solstice.

2. February Second Warmest on Record

This February was 1.76°F (0.98°C) above the 20th-century average. The only February that was hotter was in 2016. When compared to the 20th-century average, February was the 7th hottest of any month on record The last February below the 20th-century average was in 1976. The rate of the February temperature increase has doubled since 1980. 15 of the 20 warmest Februaries have come since 2000. None were before 1983.

3. The Controversial Northeast Snow Cover in Living Color

This is an image with 1 km resolution, and if you click on the image you can get a much larger version. You can see the Susquehanna River clearly and the lack of snow near the coast as the warmer ocean air changed the snow to rain. You can download a 500-meter resolution image here. The snow forecast near the coast was very tricky and there has been some controversy …



Washington, D.C.—This statement is attributable to Christine McEntee, Executive Director and CEO of the American Geophysical Union (AGU):“President Trump’s proposed budget, if enacted, would be a step backward for scientific progress, jeopardize the U.S.’s role as a leader in innovation, and harm the American public. The cuts to federal agencies such as DOE, EPA, NOAA, NSF, USGS, and programs within NASA, will put the safety and wellbeing of millions of families and companies at risk. These agencies provide research and data that are critical in informing and shaping decisions that protect public health and safety, support national security, and facilitate economic stability and job growth in the US.