AGU期刊一周Research Spotlight (May 26~ June 2, 2017)

发布时间:2017-6-2 9:58:25 点击次数:190

I. Science Policy & Funding

1. Federal Science Funding Drops Sharply in Trump Budget Plan

Congress has shown bipartisan support for Earth and space sciences in the past. Advocates hope it will do so again.

II. Geochemistry, Mineralogy, Volcanology

1. A Volcanic Trigger for Earth’s First Mass Extinction?

Abnormally high levels of mercury in Ordovician rocks may imply that a huge surge of volcanism took place at a time when much of the planet’s ocean life vanished.

2.Ancient Impact May Have Triggered Long-Term Volcanic Eruptions

Scientists revisit Canada’s Sudbury crater in light of new evidence from other planets that suggests an alternative postimpact history.

III. Hazards & Disasters

1. Scientists Predict Active Hurricane Season

A combination of warm sea surface temperatures and a weak or absent El Niño may create conditions conducive to tropical storm formation.

2. Antenna Towers Attract Additional Lightning Strikes

Atmospheric scientists evaluate the influence of human-made structures on lightning data.

3. Mining Ancient Texts Reveals Clues to Space Weather of Yore

Low-latitude sightings of colorful hues in the sky likely to have been auroras indicate powerful geomagnetic storms buffeted Earth when some old chronicles were written, researchers report.

IV. Hydrology, Cryosphere & Earth Surface

1. A Plunge into the Depths of Italy’s Lake Garda

First International Scientific Workshop on GARDEN (Lake Garda Environmental system); Trento, Italy, 2 February 2017

2. A Foundation for Modeling Time-Periodic Groundwater Flow

The authors of a new book on groundwater hydraulics and hydrology describe a theoretical foundation for modeling time-periodic groundwater flow.

V. Global Change

1. Unseasonable Weather Entrenches Climate Opinions

Democrats and Republicans double down on their climate change opinions when faced with slightly cooler or warmer weather.

VI. Space & Planets

1. First Science Results from NASA’s Juno Mission

New findings challenge assumptions about Jupiter’s composition and magnetic fields.

2. Close Encounter with Jupiter

First results from the Juno mission shed new light on Jupiter’s atmosphere, gravity, magnetic field, aurora, history, and more.

VII. Geophysical Research Letters

1. Biofilm-induced bioclogging produces sharp interfaces in hyporheic flow, redox conditions, and microbial community structure

Riverbed sediments host important biogeochemical processes that play a key role in nutrient dynamics. Sedimentary nutrient transformations are mediated by bacteria in the form of attached biofilms. The influence of microbial metabolic activity on the hydrochemical conditions within the hyporheic zone is poorly understood. We present a hydrobiogeochemical model to assess how the growth of heterotrophic and autotrophic biomass affects the transport and transformation of dissolved nitrogen compounds in bed form-induced hyporheic zones. Coupling between hyporheic exchange, nitrogen metabolism, and biomass growth leads to an equilibrium between permeability reduction and microbial metabolism that yields shallow hyporheic flows in a region with low permeability and high rates of microbial metabolism near the stream-sediment interface. The results show that the bioclogging caused by microbial growth can constrain rates and patterns of hyporheic fluxes and microbial transformation rate in many streams.

2. No significant difference between Australian heat wave impacts of Modoki and eastern Pacific El Niño

The influence of two El Niño types on the frequency of summer heat wave days in Australia is investigated using both observations and an atmospheric climate model. The two basic spatial variants of El Niño are the traditional warming in the eastern equatorial Pacific (EP) and the Modoki variant that has its largest warming in the central equatorial Pacific. While impacts of Modoki El Niño on Australian precipitation can be quite distinct from EP El Niño, the impact on heat waves is still unknown. Using a set of ensemble simulations, we compare the influence of Modoki and EP sea surface temperature forcing on Australian heat waves. We find that there is minimal difference between the impact of Modoki and EP El Niños on heat waves over Australia, which implies that future studies on heat wave variability need not differentiate the two.

3. Internal variability in a coupled general circulation model in radiative-convective equilibrium

Numerical models run in non-rotating radiative-convective equilibrium (RCE) using prescribed sea surface temperatures (SSTs) show that convection can spontaneously aggregate into dry and moist areas, and that convective aggregation tends to increase with temperature. Using a general circulation model coupled to an ocean mixed layer, we show that in RCE the coupled ocean-atmosphere system exhibits some internal variability. This variability arises from the interplay between mean surface temperature, SST gradients and convective aggregation, and its timescale is proportional to the depth of the ocean mixed layer. For an ocean layer deeper than 10 m, the variability occurs at the interannual timescale, and variations of convective aggregation are almost out of phase with those of surface temperature. The coupled RCE framework might be relevant to understand some internal modes of variability of the tropical ocean-atmosphere system such as El Niño Southern Oscillation.

4. Causes of accelerating sea level on the East Coast of North America

The tide-gauge record from the North American East Coast reveals significant accelerations in sea level starting in the late twentieth century. The estimated post-1990 accelerations range from near zero to ~0.3 mm yr−2. We find that the observed sea level acceleration is well modeled using several processes: mass change in Greenland and Antarctica as measured by the Gravity Recovery and Climate Experiment satellites; ocean dynamic and steric variability provided by the GECCO2 ocean synthesis; and the inverted barometer effect. However, to achieve this fit requires estimation of an admittance for the dynamical and steric contribution, possibly due to the coarse resolution of this analysis or to simplifications associated with parameterization of bottom friction in the shallow coastal areas. The acceleration from ice loss alone is equivalent to a regional sea level rise in one century of 0.2 m in the north and 0.75 m in the south of this region.

5. Pacific sea surface temperatures, midlatitude atmospheric circulation, and widespread interannual anomalies in western U.S. streamflow

Widespread droughts can have considerable impact on western United States (U.S.) streamflow but causes related to moisture delivery processes are not yet fully understood. Here we examine western U.S. streamflow records to identify robust leading modes of interannual variability and their links to patterns of ocean and atmospheric circulation. The leading mode of streamflow variability, a pattern of west-wide streamflow anomalies, accounts for approximately 50% of variability and is associated with persistent high-pressure anomalies related to ridges off the Pacific North American coast. The second mode of variability accounts for approximately 25% of variability and is associated with ocean and atmospheric conditions in the tropical Pacific. Our results suggest that the leading mode of streamflow variability in the western U.S. is more strongly associated with internally driven midlatitude atmospheric variability than equatorial Pacific sea surface temperatures.

6. Dynamics of a “low-enrichment high-retention” upwelling center over the southern Senegal shelf

Senegal is the southern tip of the Canary upwelling system. Its coastal ocean hosts an upwelling center which shapes sea surface temperatures between latitudes 12° and 15°N. Near this latter latitude, the Cape Verde headland and a sudden change in shelf cross-shore profile are major sources of heterogeneity in the southern Senegal upwelling sector (SSUS). SSUS dynamics is investigated by means of Regional Ocean Modeling System simulations. Configuration realism and resolution (Δx≈ 2 km) are sufficient to reproduce the SSUS frontal system.

7. Hydroacoustic ray theory-based modeling of T wave propagation in the deep ocean basin offshore eastern Taiwan

T waves are conventionally defined as seismically generated acoustic energy propagating horizontally over long distances within the minimum sound speed layer in the ocean (SOFAR axis minimum). However, T waves have also been observed by ocean-bottom seismometers in ocean basins at depths greater than the SOFAR axis minimum. Previously, nongeometrical processes, such as local scattering at rough seafloor and water-sediment interface coupling, have been proposed as possible mechanisms for deep seafloor detection of T waves. Here we employ a new T wave modeling approach based on hydroacoustic ray theory to demonstrate that seismoacoustic energy can propagate to reach deep seafloor, previously considered as shadow zone of acoustic propagation. Our new hydroacoustic simulations explain well the observations of T waves on ocean-bottom seismometers at deep ocean basins east of Taiwan and shed new light on the mechanism for deep ocean T wave propagation.


1. Scientists discover new mode of ice loss in Greenland

A new study finds that during Greenland’s hottest summers on record, 2010 and 2012, the ice in Rink Glacier on the island’s west coast didn’t just melt faster than usual, it slid through the glacier’s interior in a gigantic wave, like a warmed freezer pop sliding out of its plastic casing. The wave persisted for four months, with ice from upstream continuing to move down to replace the missing mass for at least four more months.

2. LA lawns lose 70 billion gallons of water a year

In summer 2010, Los Angeles was losing about 100 gallons of water per person per day to the atmosphere through the evaporation and plant uptake of lawns and trees, new research finds. Lawns accounted for 70 percent of the water loss, while trees accounted for 30 percent, according to a new study.

3. How To Get Your Science Noticed? Get The Government to Try and Cover It Up!

Raul Grijalva, the ranking member of the House Committee on Natural Resources, sent a hot letter this week to the Secretary of the Interior. It was about the removal of the first line of a USGS press release last week. The press release was about a newly published paper showing a dramatic increase in coastal flooding as sea level rises, and I wrote about it last week here.

4. GOES-R Will Become GOES-East

It was highly likely that the new GOES-R satellite (Now GOES 16) would be moved to where the GOES-East satellite is now when it becomes operational in November. This is now official, with the announcement coming from NOAA today. By moving GOES 16 to 75 degrees east, we will see virtually all of the Tropical Atlantic and still have good coverage of the U.S. all the way past the Rockies.