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AGU Research Spotlight (Dec 30-Jan 04, 2017)

2018-01-05 08:25:02

I. Climate Change

1.The Power of Water, Wind, and Solar (and Nothing Else)

Road map for improving climate calls for 100% clean, renewable energy by 2050.


II. Hazards & Disasters

1.What Feeds Indonesia’s Destructive Mud Eruption?

New advances in seismic investigations suggest links in plumbing between nearby magma volcanoes and a mud-erupting system that has been spewing for more than a decade.


2.The Curious Case of the Ultradeep 2015 Ogasawara Earthquake

Unusual ground motion associated with the deepest major earthquake in the seismological record is due to both its great depth and its origin away from the subducting slab.


III. Space & Planets

1.Comparing the Accuracy of Geomagnetic Field Models

Improved accuracy and optimization of models could benefit many applications.


IV. Biogeosciences

1.Scientists Probe Water Inside Leaves via Satellite

Improving satellite-based studies of vegetation optical depth, a critical ecosystem indicator.


2.Mossy Oaks Are Dripping with Organic Matter

Epiphyte-bearing trees leach carbon when it rains.


V. Geology & Geophysics

1.Read Them Again:Eos’s Most Viewed Stories of 2017

From mesmerizing maps to glacial floods and massive earthquakes, here’s a look back on last year’s most popular stories.


2.Erik M. Conway Receives 2017 Athelstan Spilhaus Award

Erik M. Conway received the Athelstan Spilhaus Award at the 2017 American Geophysical Union Fall Meeting Honors Ceremony, held on 13 December 2017 in New Orleans, La. The award honors an individual “for the enhancement of the public engagement with Earth and space sciences.”


3.Recording Belgium’s Gravitational History

Instruments at Belgium’s Membach geophysical station set a new record for monitoring gravitational fluctuations caused by storm surges, groundwater fluctuations, and the Moon’s tidal pull.


VI. Geophysical Research Letters

1. Large Lakes Dominate CO2 Evasion From Lakes in an Arctic Catchment

CO2 evasion from freshwater lakes is an important component of the carbon cycle. However, the relative contribution from different lake sizes may vary, since several parameters underlying CO2 flux are size dependent. Here we estimated the annual lake CO2 evasion from a catchment in northern Sweden encompassing about 30,000 differently sized lakes. We show that areal CO2 fluxes decreased rapidly with lake size, but this was counteracted by the greater overall coverage of larger lakes. As a result, total efflux increased with lake size and the single largest lake in the catchment dominated the CO2 evasion (53% of all CO2 evaded). By contrast, the contribution from the smallest ponds (about 27,000) was minor (<6%). Our results emphasize the importance of accounting for both CO2 flux rates and areal contribution of various sized lakes in assessments of CO2 evasion at the landscape scale.


2. Rapid Water Transport by Long-Lasting Modon Eddy Pairs in the Southern Midlatitude Oceans

Water in the ocean is generally carried with the mean flow, mixed by eddies, or transported westward by coherent eddies at speeds close to the long baroclinic Rossby wave speed. Modons (dipole eddy pairs) are a theoretically predicted exception to this behavior, which can carry water to the east or west at speeds much larger than the Rossby wave speed, leading to unusual transports of heat, nutrients, and carbon. We provide the first observational evidence of such rapidly moving modons propagating over large distances. These modons are found in the midlatitude oceans around Australia, with one also seen in the South Atlantic west of the Agulhas region. They can travel at more than 10 times the Rossby wave speed of 1–2 cm s?1 and typically persist for about 6 months carrying their unusual water mass properties with them, before splitting into individual vortices, which can persist for many months longer.


3. Investigating the Direct Meltwater Effect in Terrestrial Oxygen-Isotope Paleoclimate Records Using an Isotope-Enabled Earth System Model

Variations in terrestrial oxygen-isotope reconstructions from ice cores and speleothems have been primarily attributed to climatic changes of surface air temperature, precipitation amount, or atmospheric circulation. Here we demonstrate with the fully coupled isotope-enabled Community Earth System Model an additional process contributing to the oxygen-isotope variations during glacial meltwater events. This process, termed “the direct meltwater effect,” involves propagating large amounts of isotopically depleted meltwater throughout the hydrological cycle and is independent of climatic changes. We find that the direct meltwater effect can make up 15–35% of the δ18O signals in precipitation over Greenland and eastern Brazil for large freshwater forcings (0.25–0.50 sverdrup (106m3/s)). Model simulations further demonstrate that the direct meltwater effect increases with the magnitude and duration of the freshwater forcing and is sensitive to both the location and shape of the meltwater. These new modeling results have important implications for past climate interpretations of δ18O.


4. Volcano and Ship Tracks Indicate Excessive Aerosol-Induced Cloud Water Increases in a Climate Model

Aerosol-cloud interaction is the most uncertain mechanism of anthropogenic radiative forcing of Earth's climate, and aerosol-induced cloud water changes are particularly poorly constrained in climate models. By combining satellite retrievals of volcano and ship tracks in stratocumulus clouds, we compile a unique observational data set and confirm that liquid water path (LWP) responses to aerosols are bidirectional, and on average the increases in LWP are closely compensated by the decreases. Moreover, the meteorological parameters controlling the LWP responses are strikingly similar between the volcano and ship tracks. In stark contrast to observations, there are substantial unidirectional increases in LWP in the Hadley Centre climate model, because the model accounts only for the decreased precipitation efficiency and not for the enhanced entrainment drying. If the LWP increases in the model were compensated by the decreases as the observations suggest, its indirect aerosol radiative forcing in stratocumulus regions would decrease by 45%.


5. A Fluid Pulse on the Hikurangi Subduction Margin: Evidence From a Heat Flux Transect Across the Upper Limit of Gas Hydrate Stability

A transect of seafloor heat probe measurements on the Hikurangi Margin shows a significant increase of thermal gradients upslope of the updip limit of gas hydrate stability at the seafloor. We interpret these anomalously high thermal gradients as evidence for a fluid pulse leading to advective heat flux, while endothermic cooling from gas hydrate dissociation depresses temperatures in the hydrate stability field. Previous studies predict a seamount on the subducting Pacific Plate to cause significant overpressure beneath our study area, which may be the source of the fluid pulse. Double-bottom simulating reflections are present in our study area and likely caused by uplift based on gas hydrate phase boundary considerations, although we cannot exclude a thermogenic origin. We suggest that uplift may be associated with the leading edge of the subducting seamount. Our results provide further evidence for the transient nature of fluid expulsion in subduction zones.


VII. AGU Blogs

1.State Geological Surveys using StoryMaps to tell geologic stories

2,800 years ago, Homer sketched this visceral and indelible picture of the awesome power of floods to sculpt landforms. Over the past 175 years, state geological surveys have collectively published thousands of geologic maps, reports, bulletins and newsletters. Unlike Homer, we struggle daily telling our geology stories in ways that engage and inform decision makers and the public.


2.Normal faulting in the San Felipe Volcanic Field, New Mexico

Flying from Albuquerque to Denver last summer,en routeto Montana from theEarth Educators’ Rendezvous, I flew over a landscape that looked like the geomorphology was controlled by normal faulting. The view here is looking to the east, from a position in the air a bit north of Albuquerque.


3.A New Year’s resolution: help the public learn about NOAA

For those in attendance at the 2017 AGU Fall Meeting, you may have attended the Thursday morning keynote panel, titled Perspectives and Priorities on Earth and Space Science at Four U.S. Federal Agencies – NOAA, NASA, USGS, and NSF. The panel presented their views on the state of science at their agencies, their priorities for the near future, and how science will fare in an era of increasing budget pressures. These agencies were represented by Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA headquarters; William Easterling, head of the Directorate for Geosciences at the National Science Foundation; RDML Tim Gallaudet, USN Ret., Assistant Secretary of Commerce for Oceans and Atmosphere and Acting NOAA Administrator; and William H Werkheiser (via pre-recorded video), acting director of the U.S. Geological Survey.


4.The most remote place in the continental U.S.

Richard Forman, a Harvard professor of landscape ecology, once visited a mangrove swamp in the Florida Everglades that he described as the most remote place in the eastern U.S. The swamp was 17 miles from any road.



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