I. Climate Change
1. Advanced Satellite Tracks Air Pollution in Extraordinary Detail
The unparalleled resolution of the European Space Agency’s Sentinel-5P’s spectrometer will allow scientists to pinpoint pollution sources, the agency reports.
https://eos.org/articles/advanced-satellite-tracks-air-pollution-in-extraordinary-detail
2. Integrating Water Science and Culture for Urban Sustainability
Workshop on Water and Environmental Global Challenges: International Water Infrastructures and Security; Miami, Florida, 23–25 May 2017
https://eos.org/meeting-reports/integrating-water-science-and-culture-for-urban-sustainability
3. Focus on Climate Solutions, Panelists Say
Time remains to prevent dangerous climate change if people take action now and don’t lose hope, climate experts said.
https://eos.org/articles/focus-on-climate-solutions-panelists-say
4. Airborne Surveys Examine Water Levels of Lakes Perched on Permafrost
Do water levels in high-latitude Canadian lakes fluctuate as one body or as separate entities? The answer could reveal clues to how melting permafrost influences the environment.
https://eos.org/articles/airborne-surveys-examine-water-levels-of-lakes-perched-on-permafrost
II. Ocean Sciences
1. After Obliteration, How Long Until Life Returned?
By studying the Chicxulub crater associated with the extinction of more than 75% of species then on Earth, researchers have begun to fill in a timeline for life’s rebound after the cataclysm.
https://eos.org/articles/after-obliteration-how-long-until-life-returned
III. Hydrology, Cryosphere & Earth Surface
1. Weight of Water Dropped by Hurricane Harvey Flexed Earth’s Crust
The precipitation that fell during the storm depressed the ground in parts of Texas, Louisiana, Arkansas, and Mississippi by as much as 1.8 centimeters in some places.
https://eos.org/articles/weight-of-water-dropped-by-hurricane-harvey-flexed-earths-crust
IV. Biogeosciences
1. Threatened Sea Turtles in Hawaii Losing Ground to Rising Oceans
By midcentury, the Hawaiian green sea turtle could lose nesting beaches of increasing importance on Oahu, the most populous island in the chain.
https://eos.org/articles/threatened-sea-turtles-in-hawaii-losing-ground-to-rising-oceans
2. Eyes in the Sky Look Closer at Under-Surveyed Northern Forests
Spaceborne images give scientists a detailed picture of the boreal forests’ tree heights, which help scientists estimate their contribution to carbon budgets.
https://eos.org/articles/eyes-in-the-sky-look-closer-at-under-surveyed-northern-forests
V. Geology & Geophysics
1. Sketch Your Science: Our Guesses About Your Sketches
Eos staff do their best to guess what scientists were drawing on the Sketch Your Science wall at the American Geophysical Union’s Fall Meeting in New Orleans, La.
https://eos.org/geofizz/sketch-your-science-our-guesses-about-your-sketches
2. Mary K. Hudson Receives 2017 John Adam Fleming Medal
Mary K. Hudson was awarded the 2017 John Adam Fleming Medal at the American Geophysical Union Fall Meeting Honors Ceremony, held on 13 December 2017 in New Orleans, La. The medal is for “original research and technical leadership in geomagnetism, atmospheric electricity, aeronomy, space physics, and/or related sciences.”
https://eos.org/agu-news/mary-k-hudson-receives-2017-john-adam-fleming-medal
3. Kopp, Lamb, Lavallée, Li, and Shaw Receive 2017 James B. Macelwane Medals
Robert E. Kopp, Michael P. Lamb, Yan Lavallée, Wen Li, and Tiffany A. Shaw were awarded the 2017 James B. Macelwane Medal at the American Geophysical Union Fall Meeting Honors Ceremony, held on 13 December 2017 in New Orleans, La. The medal is for “significant contributions to the geophysical sciences by an outstanding early career scientist.”
https://eos.org/agu-news/kopp-lamb-lavallee-li-and-shaw-receive-2017-james-b-macelwane-medals
VI. Geophysical Research Letters
1. Winter Sentinel-1 Backscatter as a Predictor of Spring Arctic Sea Ice Melt Pond Fraction
Spring melt pond fraction (fp) has been shown to influence September sea ice extent and, with a growing need to improve melt pond physics in climate and forecast models, observations at large spatial scales are needed. We present a novel technique for estimating fp on sea ice at high spatial resolution from the Sentinel-1 satellite during the winter period leading up to spring melt. A strong correlation (r = −0.85) is found between winter radar backscatter and fp from first-year and multiyear sea ice data collected in the Canadian Arctic Archipelago (CAA) in 2015. Observations made in the CAA in 2016 are used to validate a fp retrieval algorithm, and a fp prediction for the CAA in 2017 is made. The method is effective using the horizontal transmit and receive polarization channel only and shows promise for providing seasonal, pan-Arctic, fp maps for improved understanding of melt pond distributions and forecast model skill.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL075547/full
2. Dual Isotope Measurements Reveal Zoning of Nitrate Processing in the Summer Changjiang (Yangtze) River Plume
Riverine nitrogen input into the coastal zone has increased remarkably in recent decades. Yet its transformation and recycling within hydrodynamically active regions remains unclear. Using observations of nitrate concentration and dual isotopic composition across the Changjiang River plume within a three end-member mixing model, we found deviations between the observed and expected values for mixing alone, revealing the nonconservative behavior of nitrate. Using cross correlations between concentrations and dual isotope deviations, we identified three nitrogen transformation zones, which correspond to separate portions of the plume. Nitrification and sedimentary denitrification occurred near the river mouth, nitrification prevailed further offshore under the plume, and finally, phytoplankton assimilation occurred in the outer surface plume (>100 km offshore), where it was fueled by nitrate that had already been strongly modified by microbial processes. Information was assembled into a conceptual model offering an overview of nitrogen transformations in a large river plume.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL075951/full
3. Agreement of CMIP5 Simulated and Observed Ocean Anthropogenic CO2Uptake
Previous studies found large biases between individual observational and model estimates of historical ocean anthropogenic carbon uptake. We show that the largest bias between the Coupled Model Intercomparison Project phase 5 (CMIP5) ensemble mean and between two observational estimates of ocean anthropogenic carbon is due to a difference in start date. After adjusting the CMIP5 and observational estimates to the 1791–1995 period, all three carbon uptake estimates agree to within 3 Pg of C, about 4% of the total. The CMIP5 ensemble mean spatial bias compared to the observations is generally smaller than the observational error, apart from a negative bias in the Southern Ocean and a positive bias in the Southern Indian and Pacific Oceans compensating each other in the global mean. This dipole pattern is likely due to an equatorward and weak bias in the position of Southern Hemisphere westerlies and lack of mode and intermediate water ventilation.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL074435/full
4. Eclogitization of the Subducted Oceanic Crust and Its Implications for the Mechanism of Slow Earthquakes
The generating mechanism and process of slow earthquakes can help us to better understand the seismogenic process and the petrological evolution of the subduction system, but they are still not very clear. In this work we present robust Pand S wave tomography and Poisson's ratio images of the subducting Philippine Sea Plate beneath the Kii peninsula in Southwest Japan. Our results clearly reveal the spatial extent and variation of a low-velocity and high Poisson's ratio layer which is interpreted as the remnant of the subducted oceanic crust. The low-velocity layer disappears at depths >50 km, which is attributed to crustal eclogitization and consumption of fluids. The crustal eclogitization and destruction of the impermeable seal play a key role in the generation of slow earthquakes. The Moho depth of the overlying plate is an important factor affecting the depth range of slow earthquakes in warm subduction zones due to the transition of interface permeability from low to high there. The possible mechanism of the deep slow earthquakes is the dehydrated oceanic crustal rupture and shear slip at the transition zone in response to the crustal eclogitization and the temporal stress/strain field. A potential cause of the slow event gap existing beneath easternmost Shikoku and the Kii channel is the premature rupture of the subducted oceanic crust due to the large tensional force.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL074945/full
5. A Midwinter Minimum in North Atlantic Storm Track Intensity in Years of a Strong Jet
This study investigates the occurrence of a midwinter suppression in synoptic eddy activity within the North Atlantic storm track. It is found that eddy kinetic energy over the Atlantic is reduced during winter relative to fall and spring, despite the stronger wintertime jet and enhanced baroclinicity. This behavior is similar to the well-known Pacific midwinter minimum, yet the reduction over the Atlantic is smaller and persists for a shorter period. To examine the conditions favorable for this phenomenon, we present an analysis of years with stronger jet intensity versus years of weaker jets over the Atlantic and Pacific basins. When the wintertime jet is stronger, the midwinter suppression of eddy activity is more pronounced, and the jet is more equatorward. Since the climatological Atlantic jet is weaker relative to the Pacific jet, the conditions for a midwinter suppression in the Atlantic are generally less favorable, yet a midwinter suppression often occurs in years of a strong jet.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL075136/full
VII. AGU Blogs
1. NASA Solves How a Jupiter Jet Stream Shifts into Reverse
Speeding through the atmosphere high above Jupiter’s equator is an east–west jet stream that reverses course on a schedule almost as predictable as a Tokyo train’s. Now, a NASA-led team has identified which type of wave forces this jet to change direction.
https://blogs.agu.org/geospace/2017/12/18/nasa-solves-jupiter-jet-stream-shifts-reverse/
2. High-resolution climate models present alarming new projections for U.S.
Researchers have developed new, high-resolution climate models that may help policymakers mitigate the effects of climate change at a local level.
3. Lava-filled blocks on Venus may indicate geological activity
For planetary scientists, Venus’s geologic heartbeat flat-lined around 700 million years ago. Now, a global view of some well-known deformation features on Venus’s surface may indicate it’s capable of crustal motion, and that motion might even be happening today, scientists reported Monday at the 2017 American Geophysical Union Fall Meeting in New Orleans.
https://blogs.agu.org/geospace/2017/12/15/lava-filled-blocks-venus-may-indicate-geological-activity/
4. Proteins in shark teeth could hint at what they eat
Certain molecules found in shark teeth proteins could tell scientists how the predators are connected to other animals in the food web, according to new research.
https://blogs.agu.org/geospace/2017/12/15/proteins-shark-teeth-hint-eat/
5. Coastal erosion threatens archaeological sites along Greenland’s fjords
Hundreds of archaeology sites lie along the shores of Greenland’s fjords and coasts, revealing the entirety of the country’s ancestral cultures from as many as four thousand years ago. Coastal erosion, however, may soon drop many of those ancestral links into the ocean.
https://blogs.agu.org/geospace/2017/12/15/23061/
6. Subterranean Serendipity: Scientists stumble upon a new way to sample magma
Scientists have never directly observed magma beneath the Earth’s surface. But thanks to the discovery of easily accessible magma chambers, it may now be possible, report scientists at the 2017 American Geophysical Union Fall Meeting in New Orleans.
