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AGU Research Spotlight (Feb 01-Feb 07, 2018)

2018-02-09 15:18:07

I. Climate Change

1. Measuring Emissions from Smoldering Peat Fires

A new study measures emission factors for tropical peatland fires in Malaysia.


II. Hazards & Disasters

1. A New Massive Open Online Course on Natural Disasters

Two professors put their college course online. Enrollment jumped more than 20-fold, and a forum for exchanging ideas with a multigenerational international community was born.


III. Science Policy

1. Trump’s Address to Congress Largely Ignores Science

Speech touts ending “the war on coal” but makes no reference to climate change.


2. A Decade of Atmospheric Data Aids Black Hole Observers

Astrophysicists are using a global atmospheric model to help them coordinate a multicontinent, radio-frequency observing campaign to gaze at the black hole at the center of the Milky Way.


IV. Biogeosciences

1. Phosphorus Pollution Reaching Dangerous Levels Worldwide

Humans discharge four times the weight of the Empire State Building’s worth of phosphorus into freshwater bodies each year, a new study finds.


2. Two Paired Eddies Travel Faster and Further Than One

The first observational evidence of dipole eddy pairs (modons) in the southern midlatitude ocean reveals that they move faster, live longer, and travel greater distances compared to single eddies.


V. Geology & Geophysics

1. When Your Weird Science Gets Stopped at Airport Security

“Gamma ray spectrometer,” “rock hammer,” and “putty knife” are not phrases that airport security likes to hear.


VI. Geophysical Research Letters

1. Ionospheric Total Electron Content Response to the Great American Solar Eclipse of 21 August 2017

Using a comprehensive database of ~4,000 ground-based Global Navigation Satellite Systems stations, we investigate the ionosphere's response to the 21 August 2017 solar eclipse. The high-resolution, two-dimensional maps of the ionospheric total electron content (TEC) were constructed using combined GPS and GLONASS measurements. Solar eclipse resulted in a continent-size TEC decrease with stronger effects up to 50% over the U.S. eastern coast. Along the totality path within an area of 75% obscuration TEC decreased by ~30–40%. We reveal a latitudinal dependence of the TEC response with equatorward expansion of TEC depletion. Recovery signature in the form of large-scale TEC enhancement up to 20–30% occurred in posteclipse period. Swarm and DMSP satellites encountered the eclipse-induced plasma density depletion and posteclipse increase at 450 km height and above. These effects were associated with downward plasma fluxes from topside ionosphere/plasmasphere and thermospheric changes.


2.Top-Down CO Emissions Based On IASI Observations and Hemispheric Constraints on OH Levels

Assessments of carbon monoxide emissions through inverse modeling are dependent on the modeled abundance of the hydroxyl radical (OH) which controls both the primary sink of CO and its photochemical source through hydrocarbon oxidation. However, most chemistry transport models (CTMs) fall short of reproducing constraints on hemispherically averaged OH levels derived from methylchloroform (MCF) observations. Here we construct five different OH fields compatible with MCF-based analyses, and we prescribe those fields in a global CTM to infer CO fluxes based on Infrared Atmospheric Sounding Interferometer (IASI) CO columns. Each OH field leads to a different set of optimized emissions. Comparisons with independent data (surface, ground-based remotely sensed, aircraft) indicate that the inversion adopting the lowest average OH level in the Northern Hemisphere (7.8 × 105 molec cm?3, ~18% lower than the best estimate based on MCF measurements) provides the best overall agreement with all tested observation data sets.


3.Pan-Arctic Distribution of Bioavailable Dissolved Organic Matter and Linkages With Productivity in Ocean Margins

Rapid environmental changes in the Arctic Ocean affect plankton productivity and the bioavailability of dissolved organic matter (DOM) that supports microbial food webs. We report concentrations of dissolved organic carbon (DOC) and yields of amino acids (indicators of labile DOM) in surface waters across major Arctic margins. Concentrations of DOC and bioavailability of DOM showed large pan-Arctic variability that corresponded to varying hydrological conditions and ecosystem productivity, respectively. Widespread hot spots of labile DOM were observed over productive inflow shelves (Chukchi and Barents Seas), in contrast to oligotrophic interior margins (Kara, Laptev, East Siberian, and Beaufort Seas). Amino acid yields in outflow gateways (Canadian Archipelago and Baffin Bay) indicated the prevalence of semilabile DOM in sea ice covered regions and sporadic production of labile DOM in ice-free waters. Comparing these observations with surface circulation patterns indicated varying shelf subsidies of bioavailable DOM to Arctic deep basins.


4. Formation of the Lunar Fossil Bulges and Its Implication for the Early Earth and Moon

First recognized by Laplace over two centuries ago, the Moon's present tidal-rotational bulges are significantly larger than hydrostatic predictions. They are likely relics of a former hydrostatic state when the Moon was closer to the Earth and had larger bulges, and they were established when stresses in a thickening lunar lithosphere could maintain the bulges against hydrostatic adjustment. We formulate the first dynamically self-consistent model of this process and show that bulge formation is controlled by the relative timing of lithosphere thickening and lunar orbit recession. Viable solutions indicate that lunar bulge formation was a geologically slow process lasting several hundred million years, that the process was complete about 4 Ga when the Moon-Earth distance was less than ~32 Earth radii, and that the Earth in Hadean was significantly less dissipative to lunar tides than during the last 4 Gyr, possibly implying a frozen hydrosphere due to the fainter young Sun.


5. Lagrangian Timescales of Southern Ocean Upwelling in a Hierarchy of Model Resolutions

In this paper we study upwelling pathways and timescales of Circumpolar Deep Water (CDW) in a hierarchy of models using a Lagrangian particle tracking method. Lagrangian timescales of CDW upwelling decrease from 87 years to 31 years to 17 years as the ocean resolution is refined from 1° to 0.25° to 0.1°. We attribute some of the differences in timescale to the strength of the eddy fields, as demonstrated by temporally degrading high-resolution model velocity fields. Consistent with the timescale dependence, we find that an average Lagrangian particle completes 3.2 circumpolar loops in the 1° model in comparison to 0.9 loops in the 0.1° model. These differences suggest that advective timescales and thus interbasin merging of upwelling CDW may be overestimated by coarse-resolution models, potentially affecting the skill of centennial scale climate change projections.


6.Estimation of Throughfall and Stemflow Bacterial Flux in a Subtropical Oak-Cedar Forest

Transport pathways of microbes between ecosystem spheres (atmosphere, phyllosphere, and pedosphere) represent major fluxes in nutrient cycles and have the potential to affect microbially mediated biogeochemical processes. Novel data on bacterial fluxes from the phyllosphere to the pedosphere during rainfall via throughfall (rain dripping from/through the canopy) and stemflow (rain funneled down tree stems) are reported. Bacterial concentrations were quantified using flow cytometry and validated with quantitative polymerase chain reaction assays in rainfall samples from an oak-cedar forest in coastal Georgia (southeastern U.S.). Bacteria concentrations (cells mL?1) and storm-normalized fluxes (cells m?2 h?1, cells m?2 mm?1) were greater for cedar versus oak. Total bacterial flux was 1.5 × 1016 cells ha?1 yr?1. These previously unexamined bacterial fluxes are interpreted in the context of major elemental pools and fluxes in forests and could represent inoculum-level sources of bacteria (if alive), and organic matter and inorganic solute inputs (if lysed) to soils.


VII. AGU Blogs

1. Friday fold: 3D model from the Portsoy Shear Zone

Today’s Friday fold comes to us from the team at eRocK, a neat repository of structurally interesting 3D models. Their website describes the project this way.


2. Tijuana: a major landslide has destroyed 70 houses.

On Friday a major landslide struck the city of Tijuana in Mexico, destroying up to 70 houses.  El Universal reports that the slide first became evident on 19th January, with progressive failure over the last few days, but that the major collapse occurred at about 3 pm on Friday.  The landslide occurred in the Lomas del Rubi subdivision.  The Yucatan Times has a detailed report in English that includes details on the development of the landslide.


3. Landslides in the Maipo Valley, Chile

Last month I was in Chile working with colleagues from the Universidad de Chile and Universidad O’Higgins on our Newton-Picarte Fund project looking at seismically-triggered landslides in the vicinity of Santiago.  We were lucky enough to spend a couple of days in the Maipo Valley in the Andes, which is home to the most extraordinary collection of very large landslides.  The image below shows a Google Earth view of the area. As the image shows, this is a region of fascinating but complex geology, high relief and, of course, a variety of landslide types.


4. A Change of Climate

By Sam Illingworth Following on from my previous post, in which I described the process of curating a book of poetry about climate change, I would now like to share with you a collection of the poems that feature in A Change of Climate. Some of the poems in this collection are sad, some of them are funny, and some of them like ‘We are no longer interested in the …



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